PROCESS FOR PRODUCING COPPER-BRAZED DOUBLE WALL STEEL TUBES BY MEANS OF LONG

COOLING LINE ANNEALING METHOD

TECHNICAL FIELD

The invention relates to the production method for metal tube having at least two walls brought together by means of copper-brazing method.

The production process developed according to the present invention comprises the process steps of air-cooling the tube by means of the annealing line integrated with the elongation line, covering the tunnel forming the annealing line with serpentine such that said annealing line will not be too long, and in the tube shaping group, increasing the diameters of the spools and the bearing that enable to shape the tubes so that the oscillation of the band layer is reduced during when the pipe is taking a shape and smoother sectional surfaces are obtained.

PRIOR ART

The stainless steel material used in today's industry are preferred to a very wide extent, because of their high corrosion and oxidation resistance, high mechanical and physical properties, hot and cold workability and weldability. In order to avoid corrosion, the steel sheets are used after increasing the corrosion, resistance of their surface. The steel sheets made of steel material are generally used in the production of steel tubes. Steel sheet tubes have a very wide field of use, especially as the brake and fuel tube in the automotive sector and also as the condenser tube in the refrigerator, washing machine and dishwasher; hence the resistance to corrosion must be provided for the surfaces thereof in contact with water and moisture.

The chemical decomposition an electrolyte undergoes under the effect of an electric current is called electrolysis. Electrolysis develops along with the conduction of said current within the electrolyte. Electrolyte is frequently in dissolved form or in the form of an aqueous solution of a salt. Both surfaces of said steel sheet is coated with copper to be used in brazing process, by means of electrolysis method. The copper- coated steel sheet is cut in the form of bands having the widths theoretically

calculated beforehand for the production of the tube with desired diameter, and the bands are wound in the form of rolls. The copper-coated sheet bands cut and wound into the bands with appropriate width are passed through shaping spools placed one after the other and are allowed to take the tube shape in cold process by means of the mandrel.

The produced copper-coated double wall tubes are conductively heated up to a temperature (~1150 ⁰ C) above the melting temperature of copper, and brazed to each other under protective gas (hydrogen) at a certain advancing speed in the heating unit. In the heating unit, the copper, i.e. the brazing material, is prevented from cooling down, as well as from being oxidized under the gas atmosphere. One of the brazing processes takes place via movable contact units, while the other takes place with stationary contact units.

According to the state of the art, once the brazing has taken place, the copper-coated steel sheet in the form of a tube enters the annealing unit and the pipe is watered at the end of the line to provide cooling. The hot copper-coated steel tube enters a fast regime of cooling under the influence of water, at the end of the annealing unit.

According to the state of the art, the costs increase and the quality reduces due to the reasons mentioned above.

Today, the practices related to brazing the steel sheets are known to exist. One of such practices disclosed in the document no. JP7258886 relates to electro- galvanization of the steel layer by means of point weldability. This document relates to steel sheet with increased weldability able to be used in the industry with high efficiency.

Another practice in the document no. 2005/02248 relates to the units wherein the brazing provided according to automation by converting the steel sheet raw material from the band form into the cylindrical form. According to this practice, the invention relates to the units wherein the brazing is carried out according to automation by converting the stainless steel sheet raw material from band form into cylindrical tubes. The model designed as Unit 1 , Unit 2 and Unit 3 comprises band raw material

inlet (1), castamide runner (2), rope (3), castamide (4), welding torch (5), diamond tip (6) and pipe outlet (7). The units may be adjusted rightwards, leftwards, upwards and downward and their degree may also be adjusted. Castamide (4) is used in Unit 1 , Unit 2 and Unit 3. The rope (3) providing form to the material used enables the smooth flow of material. In Unit 3, the rounded metallic diamond tip (6) is used made of castamide having a corrosion time of 6 months. The support is provided by means of this diamond tip (6) to enable the formed material to flow towards the weld in a continuous and uniform manner.

The patent application no. US2003012909 relates to the double wall tubes comprising a polyamide-based layer at the inside thereof and an outer layer formed of a material selected from polyether ester, polyester ether and fluorinated polymer.

The patent application no. US2003041912 relates to the tubes used in conveying the fluids comprising an inner layer made of steel, an outer layer made of steel surrounding said inner layer and an end connecting piece made of weldable steel.

However, said double wall tubes are not able to provide the desired strength. In addition, extra labor and time losses occur during the production steps of said tubes, costs increase and water consumption becomes very high.

As a result, the presence of the need for the high strength double wall tubes, which eliminate the disadvantages existing in the state of the art, and the inadequacy of the existing solutions have made it necessary to provide an improvement in the related art.

OBJECT OF THE INVENTION

The present invention relates to the method for producing the metal tubes with at least two walls, which satisfies the aforesaid requirements, eliminates all the disadvantages and provides some additional advantages.

The object of the invention is to carry out a metal tube production method that enables more controlled and slower cooling, by cooling at least two walled tube by

means of air within the line where it passes through, instead of contacting with water the copper-coated and at least two walled tube coming out of brazing process, owing to the elongation of the line.

The object of the invention is both to prevent the increase in the hardness values of the metal tubes owing to cooling by air and to avoid the possible corrosive effects of the water, which is used for cooling purposes and contacted with said tube, on the surface of the material.

In order for the cooling in the winding machines at the end of the line to reach the temperature that is possible to reach by the cooling process with water, it is needed to extend the cooling line. In order to avoid an excessive length in the cooling line, the tunnel forming the annealing unit is wrapped by serpentine sheets and in this way, the surface area in contact with the air is increased.

Another object of the invention is to decrease the oscillation of the band during the time the tube is taking shape and thus to make it possible to obtain smoother sectional surfaces.

Another object of the invention is to increase the quality of production and the product.

Another object of the invention is to reduce the costs.

Another object of the invention is to carry out the production of the tubes with wider outer diameter. In this way, the product diversity is increased.

In order to achieve all the aforesaid advantages that will understood from the following detailed description, the present invention enables the tube to be cooled by providing its contact with the air by means of the annealing line integrated with the elongation line, wherein the tunnel forming the annealing line is covered by serpentine sheets so that said annealing line will not be excessively long, thus the heat transfer rate may be increased. Also in the tube shaping group, the diameters of the spools and the bearings that allow the tube to take shape are enlarged such that

the oscillation of the band layer is reduced during when the pipe is taking its shape and smoother sectional surfaces are obtained.

The structural and characteristic features and all the advantages of the invention will be more clearly understood from the appended drawings and the detailed description written with reference to said figures and therefore, the evaluation must be made taking into consideration these figures and the detailed description.

BRIEF DESCRIPTION OF THE FIGURES

In order to best understand the embodiment of the present invention along with its additional elements and advantages, it must be considered together with the figures the description of which is provided below.

Figure-1 is the representative two-dimensional front sectional view of the double wall tube.

Figure-2 is the representative two-dimensional front view of the annealing unit for the tube with at least one copper layer.

Figure-3 is the representative two-dimensional front view of the tube shaping group.

Figure-4 is the representative two-dimensional front view of the horizontal spool group.

Figure-5 is the representative two-dimensional side view of the annealing line. Figure-6 is the representative two-dimensional front view of the section A-A of the annealing line.

REFERENCE NUMBERS

1. Tube

1.1. Steel Sheet Layer

1.2. Copper Layer

1.3. Joining Surfaces 2. Band Stand 3. Tube shaping group 3.1. Vertical spool group

3.2. Horizontal spool group 3.3 Vertical spool outlet group

4. Annealing unit 4.1. Furnace Group 4.2. Windlass Group

4.3. Leakage test device

4.4. Tube Stand

5. Crushing group

6. Tunnel 7. Sheets

8. Band layer

9. Line feet

10. Spool

11. Bearing

T Annealing line A Elongation line

DETAILED DESCRIPTION OF THE INVENTION

In this detailed description, the present invention relates to the production method for at least double walled steel tube with high corrosion resistance and strength.

Figure-1 provides the representative two-dimensional front sectional view of the double wall tube (1) and Figure-2 provides the representative two-dimensional front view of the annealing unit (4) where the tube (1) with at least one copper layer (1.2) is formed.

Both surfaces of the steel sheet layer (1.1) is coated with copper to be used in brazing process, by means of the electrolysis method. The steel sheet layer (1.1) coated with copper layer (1.2) is sliced into the widths calculated beforehand theoretically, for the production of the tube (1) with desired diameter. After this stage, said steel sheet layer (1.1) with copper layer (1.2) takes the shape of the band layer

(8) as shown in Figure-3 and Figure-4. Band layer (8) is a layer including copper coated onto the steel sheet layer (1.1). The steel sheet layer (1.1) ^' with copper layer (1.2) in the form of band layer (8) is wound in the form of a roll in the tube shaping group (3). The steel sheet layer (1.1) with copper layer (1.2) wound in the form of a roll of band layers (8) with suitable width is passed through the. shaping mandrel groups (3.1, 3.2) placed one after the other, in order to cold-shape the same in the form of a tube (1) with the help of the mandrel (shaft). The tubes (1) with copper layer (1.2) seen in Figure-1 are heated in the furnace group (4.1) at the melting temperature of the copper (about 1150 ⁰ C), and are joined to each other via their joining surfaces (1.3) under the protective gas (hydrogen) at a certain advance speed. In the furnace group (4.1), the copper, the brazing material, is prevented from cooling down, while it is also prevented from being oxidized under the gas atmosphere. Contrary to the state of the art, the diameters of the spools are increased from 38 mm to 49 mm and the bearings (11) are also enlarged in the spool groups (3.1 , 3.2), which enable the tube (1) to take a shape and are located in the tube shaping group (3) called roll forming, thus the oscillation of the band layer (8) is reduced during when the tube is (1) taking its shape and smoother sectional surfaces are obtained. In this way, it becomes also possible to perform the production of the tubes (1) having an outer diameter of 6.35mm, 8.00mm, 9.52 mm and 10.00 mm. The tube shaping group (3) comprises at least eight vertical spool groups (3.1) and at least five horizontal spool groups (3.2) placed on a steel tray with the size 2000x340 mm. At least seven of the vertical spool groups (3.1) are driven by means of a gearbox and cardan shafts. The first group comprises the crushing group (5) carrying out the necessary crushing process on the edge of the band layer (8) and the connecting element of the mandrel wire calibrating the inside of the tube (1). As seen in Figure-3, there is a front guide apparatus, which guides the band layer (8) and retains the dirt such as stone pieces on the band layer (8). The spools of the crushing group (8) are formed such that they can perform the crushing at the necessary angle on both sides of the band layer (8). The band layer (8) is first folded in the form of a wide "U". As seen in Figure-4, the fold remaining outside is supported by means of the vertical spools (10) of the horizontal spool groups (3.2), and the radius profiles are folded by means of the horizontal spools (10) in accordance with the given templates. The horizontal spools (10) and the vertical spools (10) are adjusted such that the folding edge will follow a line (i.e. they are adjusted such that the edge

remaining on the inside will advance on the same level). The tube (1) then passes through the vertical spool outlet group (3.3) to advance towards the elongation line (A) and then towards the annealing line (T).

In Figure-5, the representative two-dimensional side view of the annealing line (T) is provided, and in Figure-6, the representative two-dimensional front view of the section A-A of the annealing line (T) is provided. Contrary to the existing methods, instead of contacting with water at least two walled tube (1) coming out of the brazing process to cool down the same, the annealing unit (4) is extended by means of the annealing unit (T) integrated with elongation line (A) through which said tube (1) passes, and the contact of the tube (1) is provided with the air, thus achieving a more controlled and slower cooling of the tube. In order to provide cooling by means of air, the annealing line (T) is integrated with the elongation line (A) to cool down the tube (1) with at least two walls and owing to such cooling, the increase in the hardness values is prevented, as well as avoiding the possible corrosive effects that the water, which is used for cooling and contacting the tube (1), may cause on the surface material. In said annealing line (T), there are present the tunnel (6) and the serpentine sheets (7). As seen in Figure-5, the tunnel stands on the feet (9) in the annealing line (T). In order to avoid an excessively long annealing line (T), the tunnel forming said annealing line (T) is surrounded by steel sheets (7) and in this manner, the surface area of the tube (1) contacting the air is increased. Then the cooled tubes (1) are passed through the leakage test device (4.3) to subject the same to the leakage test. The tubes (1) having been subjected to the leakage test are passed through the windlass group (4.2) pulling the tube according to the machine speed and through the tube stand (4.4), and thus are made ready for delivery.

As a result, in order to increase the quality and reduce the cost for the production of the copper-brazed tube (1) with at least one layer, the annealing line (T) is integrated with the previously existing elongation line (A) (21.5 meters) so that the total length of the elongation line (A) and the annealing line (T) is increased to 55 meters, and the cooling of the copper-coated (1.2) tubes (1) with at least 2 walls is provided by means of air, instead of water. In addition, with the enlargement of the spool (10) diameters and the bearings (11) in the tube shaping group (3), the oscillation of the

band layer (8) is reduced during when the tube (1) is taking its shape and smoother sectional surfaces are obtained.

The invention is the production process for the metal tube (1) with at least two walls, wherein the copper is coated onto especially the steel sheet layer (1.1) by means of the electrolysis method, two wall tube (1) is obtained by stagewise advancing from the obtained sheet layer (1.1) with copper layer (1.2), the obtained two wall tube (1) is permitted to reach the brazing temperature, then it is heated at the brazing temperature by means of the two electric contact points located in a mobile and spaced manner from one another and delimiting a heating zone, and is joined by means of copper braze heated up to the occurrence of the optimum brazing, and wherein said process comprises the process step of cooling the tube (1) by providing its contact with air for a longer time along the elongation line (A) and the annealing line (T) by means of the annealing line (T) being integrated with the elongation line (A), the diameters of the spools (10) have a value of 49 mm ± 0,02 and the bearings (11) have a size in the range 31 mm ± 0,02 to 38 mm ± 0,02 so that the oscillation of the band layer (8) is reduced in the tube shaping group (3) and smoother sectional surfaces are obtained.

The invention is the line, which has the band stand (2) carrying the copper-coated steel sheet, the vertical spool group (3.1) and the horizontal spool group (3.2) enabling said band layers (8) to pass through said band stand (2) to take the shape of a tube (1), the furnace group (4.1) enabling the heating up to a temperature above the melting point of the copper and preventing the cooling of the copper and also its oxidation under the gas atmosphere, the elongation line (A) enabling the tubes (1) to be transported to the leakage test device (4.3), wherein there is provided the annealing unit (4) having at least one annealing line (T) being integrated with the elongation line (A) to provide the contact of the copper coated tube with at least two walls (1) with the air, and also the vertical spool groups (3.1) and the horizontal spool groups (3.2) are provided in said annealing unit (4) having at least one spool (10) with a size of 49 mm ± 0,02 and at least one bearing (11) with a size in the range 31 mm ± 0,02 to 38 mm ± 0,02, in order to decrease the oscillation of said band layer (8) and to enable smoother sectional surfaces to be obtained, and there are also provided the tunnel (6) through which the tube (1) passes in the annealing

line (T), and at least one sheet (7) around said tunnel (6), which enables to avoid an excessively long annealing line (T) and to increase the surface of the copper-coated tube with at least one layer in contact with the air, said steel (7) being made of steel sheet.

The protective scope of this application is determined in the section of claims and the scope may by no means be limited to the description above provided only for exemplary purposes. It is obvious that a person skilled in the art may provide the innovation put forward by the invention also by using the similar embodiments and/or apply this embodiment to other fields with similar purpose used in the relevant art. Consequently, such embodiments would obviously lack the criterion of innovative step, and especially the criterion of exceeding the state of the art.