The invention pertains to a method and a system for manufacturing a steel product having a coating with spangles, and to a steel product having a coating with spangles.

Steel products, for example flat steel products, e.g. cold rolled steel band or cold rolled steel plates, are often provided with a metallic coating to increase corrosion resistance. Some coating materials and coating processes, such as for example hot-dip coating of a product with a coating containing zinc (Zn) and aluminum (Al), result in a coating showing spangles at its outer surface. The spangles create a distinctive appearance of the steel product.

Although attempts have been made to reduce the size of the spangles as much as possible, even to the extent that they are barely visible, for some applications the spangled surface is an attractive feature in the design of an object which is to be made out of the steel product. In particular, for such applications it is attractive if the spangles are relatively large and homogenous in size.

Known methods of fabrication however generally result in steel products that have a coating with relatively small spangles that vary significantly in size from one to another.

For example, such steel products are made by a process in which first the surface of the steel product is cleaned to remove oily substances rom the surface. Such oily substances may originate from cold rolling the steel product. Typically, the steel product is arranged in a cleaning bath containing an alkaline cleaning agent in order to remove the oily substance from the surface of the steel product. After the cleaning, the steel product is annealed and then provided with a metallic coating in a hot-dip coating process.

Japanese patent applications JP2000219949 and JP2000219952 disclose processes for the manufacture of a steel product with a Zn-AI-Si coating having spangles. In the disclosed processes, the oily substance is removed in an oxidizing furnace. Then, an annealing is carried out under a reducing atmosphere. This reduces the iron oxide that has been formed on the surface of the steel product in the oxidizing furnace. This is necessary to obtain a good adhesion of the coating. After the annealing, the steel product is provided with a Zn-AI-Si coating by a hot-dip process.

In the processes known from JP2000219949 and JP2000219952, the formation of the spangles is controlled by controlling the dew point and the composition of the atmosphere under which the annealing takes place.

It has been found that the processes as known from JP2000219949 and

JP2000219952 are difficult to control, in particular with respect to the balancing of the oxidation phase during the cleaning and the reduction phase during the annealing. If the oxidation phase is too long as compared to the reduction phase, too much iron oxide will remain on the surface of the steel product which is detrimental to the coating quality, in particular to the adhesion of the coating onto the steel product. On the other hand, if the oxidation phase is not carried out long enough, residual oily substances will remain on the surface of the steel product, which is also detrimental for the quality and appearance of the coating.

Another approach that is used in the prior art to control the spangle size is to adapt the composition of the hot-dip coating bath. For example, US 6689489 proposes to modify the coating bath by adding a particulate compound constituent in effective amounts to control the spangle facet size of the coated product. Constituents include borides such as titanium boride and aluminum borides, carbides such as titanium carbide, and aluminides such as titanium aluminide.

US 6689489 is aimed at reducing the spangle size, but also mentions that sometimes a visual spangle size is desirable in Galvalume like hot-dip coated products, and that customers view inconsistent spangle size as a coating quality problem as well as an aesthetic problem. Such a visual spangle of uniform size may be produced by adding a small amount of ΤΊΒ2 grain refiner to the hot-dip coating bath. By making bath additions of between about 0.0008- 0.0012% by weight boron in the form of boride particles to the bath we are able to produce a consistent spangle facet size of between about 400 to 500 microns (measured using the mean intercept length method described in ASTM E1 12).

It is the object of the invention to provide an improved method and system for manufacturing a steel product having a coating with spangles, and an improved steel product having a coating with spangles.

The object of the invention is obtained by a method for manufacturing a steel product having a metallic coating with spangles,

wherein the method comprises the following steps:

- receiving a steel product having a surface, wherein an oily substance is present at the surface of the steel product,

- removing the oily substance from the surface of the steel product by contacting the oily substance on the surface of the steel product with a plasma in a non-oxidizing cleaning atmosphere,

- after removing the oily substance from the surface of the steel product, annealing the steel product under a non-oxidizing annealing atmosphere, - applying the metallic coating on the steel product by a hot-dip coating process whereby the metallic coating with the spangles is formed on the surface of the steel product.

In accordance with the method according to the invention, the method starts with a steel product having a surface. The surface is a steel surface. The steel product is for example a flat steel product, e.g. a cold rolled band or a cold rolled plate, or a product made from a flat steel product.

An oily substance is present at the surface of the steel product, for example as a result of the cold rolling process. In a cold rolling process, oily substances (e.g. in the form of emulsions of oil in water) are for example used for cooling the rollers and/or for lubrication between the rollers and the steel product. After the cold rolling, often some of the oily substance from the emulsion remains behind on the steel product, e.g. after the water from the emulsion has evaporated. The oily substance on the surface of the steel product may however also originate from other sources. The term "oily substance" includes greasy substances.

The method according to the invention involves removing the oily substance from the surface of the steel product. In accordance with the invention, this removal involves contacting the oily substance on the surface of the steel product with a plasma in a non- oxidizing cleaning atmosphere. As will be explained below, this way of cleaning the surface of the steel product results in the formation of the desired spangle pattern on the finished product.

In accordance with the invention, the removal of the oily substance from the steel surface takes place in a non-oxidizing atmosphere. As a consequence, non-oxidizing conditions are present at the surface of the steel product during the removal of the oily substances by the plasma. In addition to the effect on the spangle pattern in the finished product as explained below, this prevents the formation of iron oxide at the surface of the steel product during the step of the removal of oily substance from the surface of the steel product.

As a next step, the steel product is annealed under a non-oxidizing annealing atmosphere. The non-oxidizing atmosphere prevents the formation of iron oxide at the surface of the steel product during the annealing. The prevention of the formation of iron oxide at the surface of the steel product during the removal of the oily substance and during the annealing eliminates the necessity for an additional step of removing the iron oxide from the surface of the steel product before applying the metallic coating in a hot-dip process, or at least reduces the amount of effort that needs to be put into removing iron oxide from the surface of the steel product before applying the metallic coating in the hot-dip coating process. Optionally, the annealing atmosphere is such that light oxidation of the surface of the steel product that occurred between the removal of the oily substances with the plasma and the start of the annealing process is removed during the annealing.

In the method according to the invention, after the annealing the metallic coating is applied onto the steel product by a hot-dip coating process. In this step, the metallic coating with the spangles is formed on the surface of the steel product.

When known methods for manufacturing of steel products with a metallic coating having spangles are applied, the appearance of the spangles in the finished product is often unpredictable. Some products may have large spangles and thus relatively few spangles per unit of surface area, while other products have small spangles and thus relatively many spangles per unit of surface area.

The inventors have now found that when the removal of the oily substances involves contacting the oily substance on the surface of the steel product with a plasma in a non- oxidizing cleaning atmosphere, the spangles on the resulting product are uniform and large in size, resulting in a pleasant appearance of the product. It is suspected that this may be related to the connection of the oily substance to the surface of the initial steel product onto which the coating is applied, which in particular cases may be relatively strong.

If the initial steel product onto which the coating is to be applied has been produced in a way in which the oily substance on the surface of the steel product has not been subjected to high temperature and/or high pressure, the oily substance will generally be present in the form of a film. The connection between the oily substance in the film and the surface of the steel product is weak, and the oily substance can properly be removed using known methods such as chemical cleaning (e.g. by using an alkaline cleaning substance) or electrochemical cleaning.

However, in other production methods of steel products, the oily substances that are used are subjected to high temperature and/or high pressure. This occurs for example during cold rolling of flat steel products, in particular when high speed cold rolling processes are applied. In cold rolling, oily substances (e.g. in the form of emulsions of oil in water) are for example used for cooling the rollers and/or for lubrication between the rollers and the steel product. At high temperature and/or high pressure, for example esterified fatty acids which can be present in the oily substance may be degraded. Such degraded esterified fatty acids can form a strong bond with the iron atoms that are present at the surface of the steel product. For example, a C-atom of the degraded esterified fatty acid may form a covalent bond with a Fe-atom at the surface of the steel product. Such a bond is very strong and is not easily broken by generally applied methods for removing oily substances of the surface of steel products in preparation for hot-dip coating. Also other manufacturing processes may result in such strong bonds being formed between the oily substance and the surface of the steel product, in particular if these manufacturing processes involve high temperature and/or high pressure. Also other components of the oily substance than the degraded esterified fatty acids may form such a strong bond with the surface of the steel product.

Such strongly bonded degraded esterified fatty acids (or other components of the oily substance) will remain present at the surface of the steel product until the steel product is arranged into the bath of molten metal during the hot-dip coating process, as the annealing process also does not break the strong bonds. In the hot-dip coating process, they influence the formation of the spangles, for example by forming seeds for crystals to grow from. Such crystals form the spangles that are present in the finished product. So, when many of such strongly bonded degraded esterified fatty acids are present at the surface of the steel product when it is arranged in the bath of molten metal for the hot-dip coating process, the finished surface will show many small and often also unevenly shaped spangles.

The removal of the oily substance from the surface of the steel product as proposed according to the invention involves contacting the surface of the steel product with a plasma in a non-oxidizing cleaning atmosphere. This way of removing the oily substance from the surface of the steel product has shown to be effective in breaking the strong bonds, e.g. covalent bonds, between components of the oily substance and the surface of the steel product.

The plasma cleaning may preferably be done by means of a high-energy plasma arc.

With plasma arc cleaning, an electric arc is generated between an electrode of a cleaning device and the surface that is to be cleaned, similar to an arc that is created during plasma arc welding. This opposed to conventional plasma cleaning, during which a surface is only contacted with plasma ions, without the presence of an arc.

The electric arc creates, during the cleaning, very high temperatures in the surface of the steel and the resulting heat of the plasma arc breaks down the bonded organic molecules into their elemental atoms. The arc may thereby prevent the occurrence of burning or incineration of the organic molecules.

The plasma arc may further induce high current densities, which may result in quick heating, melting and/or explosive evaporation at the surface of the steel. The plasma arc cleaning may be conducted through the thermal sublimation, gasification and dissociation of the organic compounds and oxides on the surface that is to be treated.

The contacting of the surface of the steel product by the plasma does not have to be long to obtain the desired effect. Optionally, the duration of the contacting of the surface of the steel product by the plasma is 1 second or less. As a result, if a steel product from which the oily substances have been removed in accordance with the invention is provided with a metallic coating in a hot-dip coating process has relatively large and evenly shaped spangles. The method according to the invention can be applied on steel products in which the oily substance or a component of the oily substance is strongly bonded to the surface of the steel product, but also on steel products in which such a strong bond between the oily substance or a component thereof and the surface of the steel product is absent. So, the method according to the invention allows to manufacture steel products with a metallic coating having relatively large and evenly shaped spangles irrespective of the strength of the bond between the oily substance or a component of the oily substance to the surface of the steel product. This makes that the manufacturer of such steel products is no longer dependent how the initial steel product with the oily substance at the surfaces has been produced with respect to the spangling pattern that is obtained in the final product.

In a possible embodiment, the non-oxidizing cleaning atmosphere contains a mixture of H ₂ and N ₂ at atmospheric pressure or at a sub-atmospheric pressure (e.g. between 1 mbar and 1000 mbar, for example between 5 mbar and l OOmbar, for example between 10 mbar and 50 mbar, for example between 10 mbar and 30 mbar, for example between 10 mbar and 20 mbar). The plasma is created from this mixture. For example, the cleaning atmosphere contains 5 vol% H ₂ , related to the entire volume of the cleaning atmosphere. Optionally, the non-oxidizing cleaning atmosphere is a mixture of H ₂ and N ₂ at atmospheric pressure or at a sub-atmospheric pressure (e.g. between 1 mbar and 1000 mbar, for example between 5 mbar and l OOmbar, for example between 10 mbar and 50 mbar, for example between 10 mbar and 30 mbar, for example between 10 mbar and 20 mbar), containing only inevitable contaminants as further components of the mixture, e.g. contaminants that originate from the oily substance after the oily substance has been contacted by the plasma. For example, this mixture of H ₂ and N ₂ contains 5 vol% H ₂ , related to the entire volume of the cleaning atmosphere.

In a possible embodiment, the non-oxidizing cleaning atmosphere contains air at a sub- atmospheric pressure (e.g. between 1 mbar and 1000 mbar, for example between 5 mbar and l OOmbar, for example between 10 mbar and 50 mbar, for example between 10 mbar and 30 mbar, for example between 10 mbar and 20 mbar).

In possible embodiment, the non-oxidizing cleaning atmosphere contains an inert gas (e.g. argon or helium) or a mixture of inert gases (e.g. argon and helium) at atmospheric pressure or at a sub-atmospheric pressure (e.g. between 1 mbar and 1000 mbar, for example between 5 mbar and l OOmbar, for example between 10 mbar and 50 mbar, for example between 10 mbar and 30 mbar, for example between 10 mbar and 20 mbar). Optionally, the non-oxidizing cleaning atmosphere is an inert gas or a mixture of inert gases at atmospheric pressure or at a sub-atmospheric pressure ((e.g. between 1 mbar and 1000 mbar, for example between 5 mbar and l OOmbar, for example between 10 mbar and 50 mbar, for example between 10 mbar and 30 mbar, for example between 10 mbar and 20 mbar), containing only inevitable contaminants as further components, e.g. contaminants that originate from the oily substance after the oily substance has been contacted by the plasma.

In a possible embodiment, the non-oxidizing cleaning atmosphere and the non-oxidizing annealing atmosphere are the same.

In a variant of this embodiment, both the non-oxidizing cleaning atmosphere and the annealing atmosphere contain a mixture of H ₂ and N ₂ at atmospheric pressure or at a sub- atmospheric pressure (e.g. between 1 mbar and 1000 mbar, for example between 5 mbar and l OOmbar, for example between 10 mbar and 50 mbar, for example between 10 mbar and 30 mbar, for example between 10 mbar and 20 mbar). The plasma is created from this mixture. For example, the cleaning atmosphere contains 5 vol% H ₂ , related to the entire volume of the cleaning atmosphere. Optionally, the non-oxidizing cleaning atmosphere is a mixture of H ₂ and N ₂ at atmospheric pressure or at a sub-atmospheric pressure (e.g. between 1 mbar and 1000 mbar, for example between 5 mbar and l OOmbar, for example between 10 mbar and 50 mbar, for example between 10 mbar and 30 mbar, for example between 10 mbar and 20 mbar), containing only inevitable contaminants as further components of the mixture, e.g. contaminants that originate from the oily substance after the oily substance has been contacted by the plasma. For example, this mixture of H ₂ and N ₂ contains 5 vol% H ₂ , related to the combined volume of the cleaning atmosphere and the annealing atmosphere. Optionally, this mixture of H ₂ and N ₂ contains 5 vol% H ₂ related to the volume of the cleaning atmosphere and 5 vol% H ₂ related to the volume of annealing atmosphere.

The choice for cleaning atmosphere and an annealing atmosphere being or containing a mixture of H ₂ and N ₂ as described above has shown to provide particular good results.

In a further variant of this embodiment, both the non-oxidizing cleaning atmosphere and the annealing atmosphere contain an inert gas (e.g. argon or helium) or a mixture of inert gases (e.g. argon and helium) at atmospheric pressure or at a sub-atmospheric pressure (e.g. between 1 mbar and 1000 mbar, for example between 5 mbar and l OOmbar, for example between 10 mbar and 50 mbar, for example between 10 mbar and 30 mbar, for example between 10 mbar and 20 mbar). Optionally, the non-oxidizing cleaning atmosphere is an inert gas or a mixture of inert gases at atmospheric pressure or at a sub-atmospheric pressure (e.g. between 1 mbar and 1000 mbar, for example between 5 mbar and l OOmbar, for example between 10 mbar and 50 mbar, for example between 10 mbar and 30 mbar, for example between 10 mbar and 20 mbar), containing only inevitable contaminants as further components, e.g. contaminants that originate from the oily substance after the oily substance has been contacted by the plasma. In a possible embodiment, a voltage is applied to create the plasma and this voltage is between 5V and 100V. Optionally, this voltage is between 10V and 50V, for example between 15V and 30V.

In a possible embodiment, the power density that is applied to create the plasma and remove the oily substance from the surface of the steel product is between 50 kW/m ² and 150 kW/m ² , for example 100 kW/m ² .

In a possible embodiment, the energy density that is applied to remove the oily substance from the surface of the steel product is between 0.05 kWh/m ² and 0.15 kWh/m ² , for example 0.1 kWh/m ² . In a possible embodiment, the steel product is contacted at least twice by a plasma in the oil-removal step.

In a possible embodiment, the steel product is a flat steel product. For example, the steel product is a cold rolled flat steel product, e.g. a cold rolled steel band or cold rolled steel plate.

In a possible embodiment, the steel product is a cold rolled steel plate which has been subjected to a deformation process, which deformation process includes deformation in a direction out of the plane of the cold rolled steel plate. This deformation process optionally takes place before the removal of the oily substance, between the removal of the oily substance and the annealing, between the annealing and the hot-dip coating process or after the hot-dip coating process.

In a possible embodiment, the velocity of the steel product during the performance of the method is between 30 meters per minute and 250 meters per minute, optionally between 100 meters per minute and 200 meters per minute, e.g. 150 meters per minute. The removal of the oily substance by the plasma works well at these velocities, and these velocities correspond to normal processing speeds for hot-dip coating systems.

In a possible embodiment, the metallic coating comprises at least 30 wt% zinc (Zn), based on the weight of the coating.

Optionally, the metallic coating comprises at least zinc (Zn) and aluminum (Al), with the coating comprising at least 30 wt% Zn, based on the weight of the coating. Optionally, the metallic coating comprises at least zinc (Zn) and aluminum (Al), with the coating comprising at least 25 wt% Al, based on the weight of the coating. Optionally, the metallic coating comprises at least zinc (Zn) and aluminum (Al), with the coating comprising between 25 wt% and 70 wt% Al, based on the weight of the coating.

Optionally, the metallic coating comprises at least zinc (Zn) aluminum (Al) and silicon

(Si), with the coating comprising at least 30 wt% Zn, based on the weight of the coating. Optionally, the metallic coating comprises at least zinc (Zn) aluminum (Al) and silicon (Si), with the coating comprising at least 55 wt% Al, based on the weight of the coating.

Optionally, the metallic coating contains 55wt% Al, 43.4wt% Zn and 1.6 wt% Si, all based on the weight of the coating.

Optionally, the finished product is made of Galvalume ®.

Optionally, the metallic coating is a metallic coating in accordance with US 3,343,930 and/or in accordance with US 3,343,089.

Optionally, the base material of the steel product is a mild steel and/or a low alloy steel, e.g. a carbon steel or a low alloy carbon steel.

The invention further pertains to a steel product having a metallic coating with spangles, which product is obtainable by the method according to the invention, in which product the average spangle size of the metallic coating is larger than 1 .7 mm. Optionally, the average spangle size is larger than 2.0 mm, e.g. larger than 2.5 mm, e.g. larger than 3 mm. The average spangle size is measured by the average intercept distance method in accordance with Australian standard AS1733.

The invention further pertains to a steel product having a metallic coating with spangles, which product is obtainable by the method according to the invention, in which product the metallic coating has 40 spangles or less per cm ² . Optionally, the metallic coating has 30 spangles or less per cm ² , e.g. 10 spangles or less per cm ² .

In general, the amount of spangles in the metallic coating of the steel product that is manufactured in accordance with the invention is 50% or less as compared to the amount of spangles in the metallic coating of a steel product that is manufactured in accordance with known production methods.

The invention further pertains to a steel product having a metallic coating with spangles, which product is obtainable by the method according to the invention, in which product the metallic coating contains at least zinc (Zn) and aluminum (Al), with the coating comprising between 25 wt% and 70 wt% Al, based on the weight of the coating, and in which product the metallic coating has 40 spangles or less per cm ² . Optionally, in this product, the metallic coating at this part has 30 spangles or less per cm ^2, , e.g. 10 spangles or less per cm ² . Optionally, in this product, the metallic coating contains 55wt% Al, 43.4wt% Zn and 1 .6 wt% Si, all based on the weight of the coating.

The invention further pertains to a steel product having a metallic coating with spangles, which product is obtainable by the method according to the invention, in which product the metallic coating contains at least zinc (Zn) and aluminum (Al), with the coating comprising between 25 wt% and 70 wt% Al, based on the weight of the coating, and in which at least a part of the product has a material thickness between 1 mm and 2 mm, optionally between 1 .4 mm and 1.6 mm, optionally 1 .5 mm, at which part the metallic coating has 30 spangles or less per cm ² , optionally 10 spangles or less per cm ² .

Optionally, in this product, the metallic coating contains 55wt% Al, 43.4wt% Zn and 1 .6 wt% Si, all based on the weight of the coating.

The invention further pertains to a steel product having a metallic coating with spangles, which product is obtainable by the method according to the invention, in which product the metallic coating contains at least zinc (Zn) and aluminum (Al), with the coating comprising between 25 wt% and 70 wt% Al, based on the weight of the coating, and in which at least a part of the product has a material thickness between 0.1 mm and 1 mm, optionally between 0.4 mm and 0.6 mm, optionally 0.5 mm, at which part the metallic coating has 10 spangles or less per cm ² . Optionally, in this product, the metallic coating at this part has 7 spangles or less per cm ² .

Optionally, in this product, the metallic coating contains 55wt% Al, 43.4wt% Zn and 1 .6 wt% Si, all based on the weight of the coating. The invention further pertains to a steel product having a metallic coating with spangles, which product is obtainable by the method according to the invention, in which product the metallic coating contains at least zinc (Zn) and aluminum (Al), with the coating comprising between 25 wt% and 70 wt% Al, based on the weight of the coating, and in which product the average spangle size of the metallic coating is larger than 1 .7 mm. Optionally, the average spangle size is larger than 2.0 mm, e.g. larger than 2.5 mm, e.g. larger than 3 mm. The average spangle size is measured by the average intercept distance method in accordance with Australian standard AS1733.

Optionally, in this product, the metallic coating contains 55wt% Al, 43.4wt% Zn and 1 .6 wt% Si, all based on the weight of the coating.

The invention further pertains to a steel product having a metallic coating with spangles, which product is obtainable by the method according to the invention, in which product the metallic coating contains at least zinc (Zn) and aluminum (Al), with the coating comprising between 25 wt% and 70 wt% Al, based on the weight of the coating, and in which at least a part of the product has a material thickness between 1 mm and 2 mm, optionally between 1 .4 mm and 1.6 mm, optionally 1 .5 mm, at which part the average spangle size of the metallic coating is larger than 1.7 mm. Optionally, the average spangle size is larger than 2.0 mm, e.g. larger than 2.5 mm, e.g. larger than 3 mm. The average spangle size is measured by the average intercept distance method in accordance with Australian standard AS1733.

Optionally, in this product, the metallic coating contains 55wt% Al, 43.4wt% Zn and 1 .6 wt% Si, all based on the weight of the coating.

The invention further pertains to a steel product having a metallic coating with spangles, which product is obtainable by the method according to the invention, in which product the metallic coating contains at least zinc (Zn) and aluminum (Al), with the coating comprising between 25 wt% and 70 wt% Al, based on the weight of the coating, and in which at least a part of the product has a material thickness between 0.1 mm and 1 mm, optionally between 0.4 mm and 0.6 mm, optionally 0.5 mm, at which part the average spangle size of the metallic coating is larger than 3.0 mm. Optionally, the average spangle size is larger than 3.5 mm, e.g. larger than 4.0 mm. The average spangle size is measured by the average intercept distance method in accordance with Australian standard AS1733.

Optionally, in this product, the metallic coating contains 55wt% Al, 43.4wt% Zn and 1 .6 wt% Si, all based on the weight of the coating.

The invention further pertains to a system for manufacturing a steel product having a metallic coating with spangles,

wherein the system comprises:

- a receiving section, which is adapted to receive a steel product having a surface with an oily substance being present at the surface of the steel product,

- an oil-removal device which is adapted to remove the oily substance from the surface of the steel product, which oil-removal device comprises an oil-removal chamber for accommodating the steel product or a part thereof during the removal of the oily substance and a plasma generating device which is adapted to generate a plasma inside the oil-removal chamber so as to allow the oily substance to be contacted by the plasma,

- an annealing device which is adapted to perform annealing of the steel product or part thereof after the removal of the oily substance from the surface of said steel product or said part thereof, which annealing device comprises an annealing chamber for accommodating the steel product during the annealing, - a hot-dip coating device, which is adapted to apply a metallic coating on the steel product or a part thereof by a hot-dip coating process after annealing the steel product or the part thereof,

- an atmosphere control device which is adapted to create and maintain a non-oxidizing atmosphere in the oil-removal chamber and in the annealing chamber.

The system according to the invention is suitable for carrying out the method according to the invention. The system according to the invention comprises a receiving section, an oil-removal device, an annealing device, a hot-dip coating device and an atmosphere control device.

The receiving section is adapted to receive a steel product having a surface with an oily substance being present at the surface of the steel product. The steel product enters the system according to the invention via the receiving section.

The oil-removal device is adapted to remove the oily substance from the surface of the steel product. The oil-removal device comprises an oil-removal chamber for accommodating the steel product or a part thereof during the removal of the oily substance and a plasma generating device which is adapted to generate a plasma inside the oil-removal chamber. The plasma that is created by the plasma generating device in use contacts the oily substance on the surface of the steel product when the steel product or a part thereof is in the oil-removal chamber. The steel product or a part thereof being in the oil-removal chamber includes the situation where the steel product is at least partly in the oil-removal chamber, e.g. in case the steel product is supplied from a coil of steel product and moved through the system in a continuous process. The plasma generating device for example contains at least one electrode and a voltage generator which is adapted to create a voltage differential between the electrode and the steel product to create a plasma.

The annealing device is adapted to perform annealing of the steel product or a part thereof after the removal of the oily substance from said steel product or said part thereof. The annealing device comprises an annealing chamber for accommodating the steel product or a part thereof during the annealing.

The hot-dip coating device is adapted to apply a metallic coating on the steel product by a hot-dip coating process. This takes places after annealing the steel product. The hot-dip coating device for example comprises a container for accommodating a bath of molten metal from which the coating is to be formed.

The atmosphere control device is adapted to create and maintain a non-oxidizing atmosphere in the oil-removal chamber and in the annealing chamber. The atmosphere control device may for example comprise one or more gas sources and/or a pressure control system.

In a possible embodiment, the system according to the invention further comprises a conveyor system which is adapted to move the steel product along a processing path in a direction of conveyance. The processing path extends from the receiving section, through the oil-removal chamber of the oil-removal device, through the annealing chamber of the annealing device and through the hot-dip coating device.

In this embodiment, the oil-removal chamber is arranged upstream of the annealing chamber as seen in the direction of conveyance, and the annealing chamber is arranged upstream of the hot-dip coating device as seen in the direction of conveyance.

The conveyor system may for example comprise an automated conveyor, e.g. a conveyor belt or chain conveyor, and/or a conveyor comprising a plurality of guide wheels and/or support wheels and/or support rollers. The support wheels, support rollers and/or guide wheels may be driven or idle. Alternatively or in addition, the conveyor system comprises a wheeled container which is automatically or manually transported within the system according to the invention.

Optionally, the conveyor system is adapted to transport the steel product at a velocity between 30 meters per minute and 250 meters per minute, optionally between 100 meters per minute and 200 meters per minute, e.g. 150 meters per minute.

The conveyor system is optionally adapted to support and move along the processing path a plurality of individual steel products, e.g. separate steel plates or steel tubes, and/or a long steel strip that is uncoiled from a coil, or a continuous steel product which originates from a continuous steel product manufacturing process, e.g. a continuous steel product manufacturing process which includes a cold rolling process.

The system according to the invention may allow the process of the invention to be carried out continuously or in a batch-wise manner. In a possible embodiment of the system according to the invention, the oil-removal chamber and the annealing chamber are connected to each other through a connection passage. During use, the composition and the pressure of the cleaning atmosphere, the annealing atmosphere and the atmosphere in the connection passage are substantially the same.

In a possible embodiment of the system according to the invention, the system comprises a combined processing chamber having an oil-removal section and an annealing section, and wherein the oil-removal section contains the oil-removal chamber and wherein the annealing section contains the annealing chamber.

In a possible embodiment of the system according to the invention, the atmosphere control device comprises a cleaning atmosphere control device and an annealing atmosphere control device. The cleaning atmosphere control device is adapted to control the cleaning atmosphere in the oil-removal chamber. The annealing atmosphere control device is adapted to control the annealing atmosphere in the annealing chamber. In a possible embodiment of the system according to the invention, the receiving section is adapted to align the steel product for processing in the system. Optionally, alternatively or in addition, the receiving section provides an air lock or other sealing device to separate the cleaning atmosphere inside the oil-removal chamber of the oil-removal device from the outside atmosphere.

The invention will be described in more detail below under reference to the drawing, in which in a non-limiting manner exemplary embodiments of the invention will be shown. The drawing shows in:

Fig. 1 : a first embodiment of the system according to the invention, which allows to carry out an embodiment of the method according to the invention,

Fig. 2: a second embodiment of the system according to the invention, which allows to carry out an embodiment of the method according to the invention,

Fig. 3A: shows a first example of a steel product having a coating with spangles, which steel product has been produced in accordance with a first known method,

Fig. 3B: shows a first example of a steel product having a coating with spangles, which steel product has been produced in accordance with a second known method,

Fig. 3C: shows a first example of a steel product having a coating with spangles, which steel product has been produced in accordance with the method according to the invention, Fig. 4A: shows a second example of a steel product having a coating with spangles, which steel product has been produced in accordance with a first known method,

Fig. 4B: shows a second example of a steel product having a coating with spangles, which steel product has been produced in accordance with a second known method,

Fig.4C: shows a second example of a steel product having a coating with spangles, which steel product has been produced in accordance with the method according to the invention. Fig. 1 shows a first of the system 1 according to the invention, which allows to carry out an embodiment of the method according to the invention.

In the embodiment of fig. 1 , the system 1 comprises a receiving section 10 , an oil- removal device 20, an annealing device 30, a hot-dip coating device 40 and an atmosphere control device 50.

The receiving section 10 is adapted to receive a steel product 5 having a surface 6 with an oily substance being present at the surface 6 of the steel product 5. The steel product enters 5 the system 1 via the receiving section 10. For example, the steel product 5 is a cold rolled strip or cold rolled plate. Optionally, the receiving section 10 is adapted to align the steel product 5 for processing in the system 1. Optionally, alternatively or in addition, the receiving section 10 provides an air lock or other sealing means to separate the cleaning atmosphere inside the oil-removal device 20 from the outside atmosphere.

The oil-removal device 20 is adapted to remove the oily substance from the surface 6 of the steel product 5. The oil-removal device 20 comprises an oil-removal chamber 21 for accommodating the steel product 5 or a part thereof during the removal of the oily substance and a plasma generating device 22 which is adapted to generate a plasma 24 inside the oil- removal chamber 21. The plasma 24 that is created by the plasma generating device 22 in use contacts the oily substance on the surface 6 of the steel product 5 when the steel product 5 or a part thereof is in the oil-removal chamber 21 .

In the embodiment of fig. 1 , the plasma generating device 22 comprises two electrodes

23 and a voltage generator 26 which is adapted to create a voltage differential between the electrodes 23 and the steel product 5 to create a plasma. In the embodiment of fig. 1 , the voltage generator is connected to the steel product 5 via a sliding contact 25.

The annealing device 30 is adapted to perform annealing of the steel product 5 or a part thereof after the removal of the oily substance from said steel product or said part thereof. The annealing device 30 comprises an annealing chamber 31 for accommodating the steel product 5 or a part thereof during the annealing.

The hot-dip coating device 40 is adapted to apply a metallic coating on the steel product 5 after annealing the steel product 5. The coating is applied using a hot-dip coating process. In the embodiment of fig. 1 , the hot-dip coating device 40 comprises a container 41 for accommodating a bath of molten metal from which the coating is to be formed.

The atmosphere control device 50 is adapted to create and maintain a non-oxidizing atmosphere in the oil-removal chamber 21 and in the annealing chamber 31 . The atmosphere control device 50 may for example comprise one or more gas sources and/or a pressure control system. In the embodiment of fig. 1 , the system 1 further comprises a conveyor system 60 which is adapted to move the steel product 5 along a processing path 63 in a direction of conveyance 61 . The processing path extends from the receiving section 10, through the oil- removal chamber 21 of the oil-removal device 20, through the annealing chamber 31 of the annealing device 30 and through the hot-dip coating device 40.

As can be seen in fig. 1 , the oil-removal chamber 21 is arranged upstream of the annealing chamber 31 as seen in the direction of conveyance 61 , and the annealing chamber 31 is arranged upstream of the hot-dip coating device 40 as seen in the direction of conveyance 61 .

In the example of fig. 1 , the conveyor system 60 comprises a plurality of rotatable rollers 62, which support and move the steel product 5 along the processing path 63.

Optionally, the conveyor system 60 is adapted to transport the steel product 5 at a velocity between 30 meters per minute and 250 meters per minute, optionally between 100 meters per minute and 200 meters per minute, e.g. 150 meters per minute.

In the embodiment of fig. 1 , the oil-removal chamber 21 and the annealing chamber 31 are connected to each other through a connection passage 32. During use, the composition and the pressure of the cleaning atmosphere, the annealing atmosphere and the atmosphere in the connection passage 32 are substantially the same.

In the embodiment of fig. 1 , optionally, the annealing chamber 41 is connected to the hot-dip coating device 40 by a second connection passage 42, in which also a non-oxidizing atmosphere, for example the same as the annealing atmosphere, is present in order to avoid oxidation of the steel product 5 after annealing.

In the embodiment of fig. 1 , the atmosphere control device 50 comprises a cleaning atmosphere control device 51 and an annealing atmosphere control device 52 . The cleaning atmosphere control device 51 is adapted to control the cleaning atmosphere in the oil- removal chamber 21. The annealing atmosphere control device 52 is adapted to control the annealing atmosphere in the annealing chamber 31 .

In the embodiment of fig. 1 , the processing starts with a steel product 5 having a surface 6. The surface 5 is a steel surface. The steel product 5 is for example a flat steel product, e.g. a cold rolled band or a cold rolled plate, or a product made from a flat steel product. An oily substance is present at the surface 6 of the steel product 5, for example as a result of the cold rolling process. This steel product, or a part thereof, is received in the receiving section 10 of the system 1. Then, the oily substance is removed from the surface 6 of the steel product 5. This removal involves contacting the oily substance on the surface 6 of the steel product 5 with a plasma 24 in a non-oxidizing cleaning atmosphere inside the oil-removal chamber 21 . In the example of fig. 1 , two clouds of plasma 24 are created, so the surface 6 of the steel product 5 is brought into contact with the plasma 24 twice. Alternatively, it is possible to contact the surface 6 of the steel product 5 contact with the plasma 24 only once or more times than twice.

As a next step, the steel product 5 is annealed under a non-oxidizing annealing atmosphere in the annealing chamber 31 .

Then, after the annealing, the metallic coating is applied onto the steel product 5 by a hot-dip coating process which takes place in the hot-dip coating device 40.

In the embodiment of fig. 1 , the non-oxidizing cleaning atmosphere contains a mixture of H ₂ and N ₂ at atmospheric pressure or at a sub-atmospheric pressure (for example between 10 mbar and 50 mbar, e.g. between 10 mbar and 20 mbar). The plasma 24 is created from this mixture. Optionally, the non-oxidizing cleaning atmosphere is a mixture of H ₂ and N ₂ at atmospheric pressure or at a sub-atmospheric pressure (for example between 10 mbar and 50 mbar, e.g. between 10 mbar and 20 mbar), containing only inevitable contaminants as further components of the mixture, e.g. contaminants that originate from the oily substance after the oily substance has been contacted by the plasma.

For example, the mixture of H ₂ and N ₂ contains 5 vol% H ₂ , related to the volume of the cleaning atmosphere.

In the embodiment of fig. 1 , the non-oxidizing cleaning atmosphere and the non- oxidizing annealing atmosphere are the same. Optionally, the mixture of H ₂ and N ₂ contains 5 vol% H ₂ , related to the volume of the cleaning atmosphere and 5 vol% H ₂ related to the volume of the annealing atmosphere.

In the embodiment of fig. 1 , a voltage is applied to create the plasma 24 and this voltage is between 15V and 30V.

In the embodiment of fig. 1 , the power density that is applied to create the plasma and remove the oily substance from the surface of the steel product is between 50 kW/m ² and 150 kW/m ² , for example 100 kW/m ² .

In the embodiment of fig. 1 , the metallic coating optionally comprises at least zinc (Zn) and aluminum (Al), with the coating comprising between 25 wt% and 70 wt% Al, based on the weight of the coating. Optionally, the finished product is made of a Galvalume material. The finished steel product 5 that is obtained by carrying out the method according to the invention in the system according to fig. 1 has spangles at its surface 6.

Fig. 2 shows a second embodiment of the system according to the invention, which allows to carry out an embodiment of the method according to the invention.

The embodiment of fig. 2 is similar to the embodiment of fig. 1. The difference is that in the embodiment of fig.2, the system comprises a combined processing chamber 70. The combined processing chamber 70 has an oil-removal section 71 and an annealing section 72. The oil-removal section 71 contains the oil-removal chamber 21 and the annealing section 72 contains the annealing chamber 31.

The oil-removal device 20 is adapted to remove the oily substance from the surface 6 of the steel product 5. In the embodiment of fig. 2, the oil-removal chamber 21 is arranged in an oil-removing section 71 in the combined process chamber 70. The steel product 5 or a part thereof is accommodated in the oil-removal chamber 21 of the oil-removal section 71 of the combined process chamber 70 during the removal of the oily substance. In this embodiment, the plasma generating device 22 is adapted to generate a plasma 24 inside the oil-removal chamber 21 of the oil-removal section 71 of the combined process chamber 70. The plasma 24 that is created by the plasma generating device 22 in use contacts the oily substance on the surface 6 of the steel product 5 when the steel product 5 or a part thereof is in the oil- removal chamber 21 of the oil-removal section 71 of the combined process chamber 70.

The annealing device 30 is adapted to perform annealing of the steel product 5 or a part thereof after the removal of the oily substance from said steel product or said part thereof. In the embodiment of fig. 2, the annealing chamber 31 is arranged in an annealing section 72 in the combined process chamber 70. The steel product 5 or a part thereof is accommodated in the annealing chamber 31 of the annealing section 72 of the combined process chamber 70 during the annealing.

In the embodiment of fig. 2, the conveyor system 60 is adapted to move the steel product 5 along a processing path 63 in a direction of conveyance 61 . In this embodiment, the processing path extends from the receiving section 10, through the oil-removing chamber 21 in the oil-removal section 71 , through the annealing chamber 32 in the annealing section 72 and through the hot-dip coating device 40.

As can be seen in fig. 2, the oil-removal section 71 is arranged upstream of the annealing section 72 as seen in the direction of conveyance 61 , and the annealing section 72 is arranged upstream of the hot-dip coating device 40 as seen in the direction of conveyance 61 . Example 1

In example 1 , three steel products with spangles are made. Each steel product is made using a different production method. The first and second product are made by a production method that is known in the art, while the third product is made using the method according to the invention. In the three production methods, the relevant production parameters were identical.

All three steel products have been provided with the same type of coating. This coating contains 55wt% Al, 43.4 wt% Zn and 1 .6 wt% Si (all based on the weight of the coating).

The three steel products that result from the application of the three production methods are shown in the figures 3A, 3B and 3C, respectively. All figures show the resulting steel products at the same scale. The width of each steel product is 8 centimeters, the thickness about 1.5 mm.

Fig. 3A shows the surface of the first example of the steel product with the coating which product has been made using the first production method. The first production method is a known production method.

In the first production method, the initial product is a mild steel strip of 8 centimeters wide, with some oily substance at it surface. The oily substance originates from the cold rolling process.

The oily substance is removed by a vapour phase cleaning method. By use of this vapour phase cleaning method generally only poorly adherent organic molecules will be removed.

After the removal of the oily substance from the surface of the steel product, the steel product is annealed at a temperature of 800 °C, during 1 minute, under an atmosphere of 5%

H ₂ in N ₂ (dew point of -30 °C) at atmospheric pressure.

After the annealing, the steel product is subjected to a hot-dip coating process. The temperature of the bath with the liquid coating material was 590°C, and the steel product was submerged in the bath during 5 seconds. After removal of the steel product from the coating bath, the steel product was cooled at a cooling rate of about 2 Kelvin per second for 10 seconds and followed by forced cooling at a cooling rate of about 20 Kelvin per second

(between about 580 °C and 500 °C).

The steel product obtained by this method is shown in fig. 3A. As can be seen, the spangles are very small and the surface of the product has an uneven appearance. About 80 spangles per cm ² are found on this steel product. Fig. 3B shows the surface of the first example of the steel product with the coating which has been made using the second production method. The second production method is a known production method.

In the second production method, the initial product is a mild steel strip of 8 centimeters wide, with some oily substance at it surface. The oily substance originates from the cold rolling process. The initial product is the same as the initial product that was subjected to the first production method.

The oily substance is removed using Ricoline C72 which is a strong alkaline cleaning agent (pH about 13, 60 °C processing temperature) and that is known to remove organic molecules (eg. fatty acid esters) and inorganic substances (eg. salts of fatty acids)

After the removal of the oily substance from the surface of the steel product, the steel product is annealed at a temperature of 800 °C, during 1 minute, under an atmosphere of 5% H ₂ in N ₂ (dewpoint of about -10 °C) at atmospheric pressure. In the early stages of the annealing, some oxidation of the surface occurs when this second production method is used.

After the annealing, the steel product is subjected to a hot-dip coating process. The temperature of the bath with the liquid coating material was 590°C, and the steel product was submerged in the bath during 5 seconds. After removal of the steel product from the coating bath, the steel product was cooled at a cooling rate of about 2 Kelvin per second for 10 seconds and followed by forced cooling at a cooling rate of about 20 Kelvin per second (between about 580 °C and 500 °C).

The steel product obtained by this method is shown in fig. 3B. As can be seen, the spangles are larger than those on the steel product made by the first production method, but they are still rather small and the sizes of the different spangles are quite different from each other. About 40 spangles per cm ² are found on this steel product. This still results in a surface having an uneven appearance, which makes the steel product not very suitable for design applications in which the surface appearance is important.

Fig. 3C shows the surface of the first example of the steel product with the coating which has been made using the third production method, which is the method according to the invention.

In the third production method, the initial product is a mild steel strip of 8 centimeters wide, with some oily substance at it surface. The oily substance originates from the cold rolling process. The initial product is the same as the initial product that was subjected to the first production method and the same as the initial product that was subjected to the second production method.

The oily substance is removed by contacting the surface of the steel product with a plasma. The plasma was generated in a cleaning atmosphere containing 5% H ₂ in N ₂ . The pressure in the cleaning atmosphere was atmospheric pressure (1 bar). The voltage difference between the electrodes to generate the plasma was 16 V, and the applied energy density was 0.12 kWh/m ² . No addition removal of the oily substance took place before contacting the surface of the steel product with the plasma, or between the contacting of the surface with the plasma and the subsequent annealing.

After the removal of the oily substance from the surface of the steel product, the steel product is annealed at a temperature of 800 °C, during 1 minute, under an atmosphere of 5% H ₂ in N ₂ (dewpoint of about -30 °C) at atmospheric pressure. After the annealing, the steel product is subjected to a hot-dip coating process The temperature of the bath with the liquid coating material was 590°C, and the steel product was submerged in the bath during 5 seconds. After removal of the steel product from the coating bath, the steel product was cooled at a cooling rate of about 2 Kelvin per second for 10 seconds and followed by forced cooling at a cooling rate of about 20 Kelvin per second (between about 580 °C and 500 °C). (determined at a surface temperature of the steel product of about 400°C).

The steel product obtained by this method is shown in fig. 3C. As can be seen, the spangles are larger than those on the steel products made by the first and second production method. The size of the spangles is evenly distributed, and does not vary a lot between one spangle and another. About 20 spangles per cm ² are found on this steel product. This results in a surface having a decorative appearance, which makes the steel product suitable for design applications in which the surface appearance is important.

Example 2 In example 2, again three steel products with spangles are made. Each steel product is made using a different production method. The first and second product are made by a production method that is known in the art, while the third product is made using the method according to the invention. In the three production methods, the relevant production parameters were identical.

All three steel products have been provided with the same type of coating. This coating contains 55wt% Al, 43.4 wt% Zn and 1 .6 wt% Si (all based on the weight of the coating).

The three steel products that result from the application of the three production methods are shown in the figures 4A, 4B and 4C, respectively. All figures show the resulting steel products at the same scale. The width of each steel product is 8 centimeters, the thickness about 0.5 mm. Fig. 4A shows the surface of the second example of the steel product with the coating which has been made using the first production method. The first production method is a known production method. The first production method of example 2 is very similar to the first production method of example 1 .

In the first production method, the initial product is a mild steel strip of 8 centimeters wide, with some oily substance at it surface. The oily substance originates from the cold rolling process.

The oily substance is removed by a vapour phase cleaning method. By use of this vapour phase cleaning method generally only poorly adherent organic molecules will be removed.

After the removal of the oily substance from the surface of the steel product, the steel product is annealed at a temperature of 800 °C, during 1 minute, under an atmosphere of 5% H ₂ in N ₂ (dewpoint of about -30 °C) at atmospheric pressure.

After the annealing, the steel product is subjected to a hot-dip coating process. The temperature of the bath with the liquid coating material was 590°C, and the steel product was submerged in the bath during 5 seconds. After removal of the steel product from the coating bath, the steel product was cooled at a cooling rate of about 3 Kelvin per second for 10 seconds and followed by forced cooling at a cooling rate of about 40 Kelvin per second (between about 570 °C and 500 °C).

The steel product obtained by this method is shown in fig. 4A. As can be seen, the spangles are very small and the surface of the product has an uneven appearance. About 24 spangles per cm ² are found are found on this steel product. When comparing the steel product shown in fig. 4A to the steel product shown in fig. 3A, the spangles on the surface of the steel product shown in fig. 4A are larger than the spangles on the surface of the steel product shown in fig. 3A. It is believed that this is cause by the faster cooling of the steel product after applying the hot-dip coating in the production method of example 2.

Fig. 4B shows the surface of the first example of the steel product with the coating which has been made using the second production method. The second production method a known production method. The second production method of example 2 is very similar to the second production method of example 1 .

In the second production method, the initial product is a mild steel strip of 8 centimeters wide, with some oily substance at it surface. The oily substance originates from the cold rolling process. The initial product is the same as the initial product that was subjected to the first production method. The oily substance is removed using Ricoline C72 which is a strong alkaline cleaning agent (pH about 13, 60 °C processing temperature) and that is known to remove organic molecules (eg. fatty acid esters) and inorganic substances (eg. salts of fatty acids).

After the removal of the oily substance from the surface of the steel product, the steel product is annealed at a temperature of 800 °C, during 1 minute, under an atmosphere of 5% H ₂ in N ₂ (dewpoint of about -30 °C) at atmospheric pressure. In the early stages of the annealing, some oxidation of the surface occurs when this second production method is used.

After the annealing, the steel product is subjected to a hot-dip coating process. The temperature of the bath with the liquid coating material was 590°C, and the steel product was submerged in the bath during 5 seconds. After removal of the steel product from the coating bath, the steel product was cooled at a cooling rate of about 3 Kelvin per second for 10 seconds and followed by forced cooling at a cooling rate of about 40 Kelvin per second (between about 580 °C and 500 °C).

The steel product obtained by this method is shown in fig. 4B. As can be seen, the spangles are larger than those on the steel product made by the first production method, but they are still rather small and the sizes of the different spangles are quite different from each other. About 12 spangles per cm ² are found on this steel product. This still results in a surface having an uneven appearance, which makes the steel product not very suitable for design applications in which the surface appearance is important.

When comparing the steel product shown in fig. 4B to the steel product shown in fig. 3B, the spangles on the surface of the steel product shown in fig. 4B are larger than the spangles on the surface of the steel product shown in fig. 3B. It is believed that this is cause by the faster cooling of the steel product after applying the hot-dip coating in the production method of example 2.

Fig. 4C shows the surface of the first example of the steel product with the coating which has been made using the third production method, which is the method according to the invention.

In the third production method, the initial product is a mild steel strip of 8 centimeters wide, with some oily substance at it surface. The oily substance originates from the cold rolling process. The initial product is the same as the initial product that was subjected to the first production method and the same as the initial product that was subjected to the second production method.

The oily substance is removed by contacting the surface of the steel product with a plasma. The plasma was generated in a cleaning atmosphere containing 5% H ₂ in N ₂ . The pressure in the cleaning atmosphere was atmospheric pressure (1 bar). The voltage difference between the electrodes to generate the plasma was 16 V, and the applied energy density was 0.12 kWh/m ² . No addition removal of the oily substance took place before contacting the surface of the steel product with the plasma, or between the contacting of the surface with the plasma and the subsequent annealing.

After the removal of the oily substance from the surface of the steel product, the steel product is annealed at a temperature of 800 °C, during 1 minute, under an atmosphere of 5% H ₂ in N ₂ (dewpoint of about - 30 °C) at atmospheric pressure.

After the annealing, the steel product is subjected to a hot-dip coating process The temperature of the bath with the liquid coating material was 590°C, and the steel product was submerged in the bath during 5 seconds. After removal of the steel product from the coating bath, the steel product was cooled at a cooling rate of about 3 Kelvin per second for 10 seconds and followed by forced cooling at a cooling rate of about 40 Kelvin per second (between about 580 °C and 500 °C).

The steel product obtained by this method is shown in fig. 4C. As can be seen, the spangles are larger than those on the steel products made by the first and second production method. The size of the spangles is evenly distributed, and does not vary a lot between one spangle and another. About 6 spangles per cm ² are found on this steel product. This results in a surface having a decorative appearance, which makes the steel product suitable for design applications in which the surface appearance is important.

When comparing the steel product shown in fig. 4C to the steel product shown in fig. 3C, the spangles on the surface of the steel product shown in fig. 4C are larger than the spangles on the surface of the steel product shown in fig. 3C It is believed that this is cause by the faster cooling of the steel product after applying the hot-dip coating in the production method of example 2.