Technical Field

The invention relates to a system and a welding method for preventing liquid metal embrittlement in the welding zone and improving the welding quality.

In particular, the invention relates to a system and a welding method in which the molten liquid metal is removed by ejecting or sucking from the welding area beyond the point resistance welding electrode through a radially outward opening hole in the cap center.

State of the Art

Cracks that occur during the welding process are usually limited material separations that extend two-dimensionally, i.e., in a planar manner. Cracks are significant welding defects and can occur in the fusion welding, the base metal, the weld metal, or the heat-affected zone.

Cracks occur due to regional stresses in the welding metal. These cracks can be transverse, longitudinal, crater, star, or scattered. The stresses that cause the crack result from the welding metal contracting and the prevention of this contraction. Cracks in the weld metal can occur due to reasons such as poor adaptation of the parts to be welded, improper welding edges, insufficient penetration, residues, high sulfur content in the material composition, or low ductility of the material.

One of the most common reasons of cracks in the prior art is residues in the welding zone. These cracks occur when a low temperature melting residue material at grain boundaries is heated to very high temperatures, causing the grain boundaries to be re-melted and shrinkage stresses to occur during cooling. In these regions, grain boundary phases or segregation zones with a lower melting temperature than the surrounding matrix melt locally and create cracks due to the shrinkage that occurs during cooling. These cracks are typically microcracks that are difficult to detect with non-destructive testing.

To prevent cracks caused by residues in the welding process, non-ferrous metals such as Zn, Cu, and Al that cause liquid metal embrittlement must be removed from the area.

A thin layer of zinc is applied to steel for corrosion protection by galvanizing. Since the simplest and most economical galvanizing method is hot-dip galvanizing, this process is mostly carried out by this method. During spot resistance welding, molten Zn easily infiltrates grain boundaries on the steel surface. Cracks and brittle fractures occur during solidification. It is widely known that liquid metal embrittlement develops due to various factors such as liquid Zn, welding parameters, and liquid metal brittle-sensitive alloys.

In the context of this invention, the electrodes of the welding area are used to bring the temperature of zinc above its melting point in order to remove zinc from the surface before welding. Afterwards, the liquid zinc is intended to be removed from the environment with radius channels that direct compressed air. Air/gas will be introduced into the electrode redirectors instead of the electrode caps.

In a design where the installation is made directly on the cap, the record must also change with the cap. This leads to an increase in cost.

EP18709083.2 relates to a resistance spot welding method for zinc-coated steel plates adapted specifically to the requirements of the automotive industry, in order to achieve high mechanical resistance in the welds and reduce the risk of crack formation due to liquid metal embrittlement.

In conclusion, due to the aforementioned problems and the inadequacy of the current solutions regarding this issue, it has become necessary to develop a new solution in the relevant technical field.

Object of the Invention

The invention aims to solve the aforementioned negatives by being created inspired by the current circumstances.

Main object of the invention is to remove the molten liquid metal from the welding point area, either by ejecting or suction, through a radius hole that opens outward at the center of the electrode cap of the resistance spot welding.

Another object of the invention is to remove the molten coating material from the welding area using pressurized gas.

Another object of the invention is to reduce the cost of electrode replacement by directing air/gas into the redirector outside the electrode caps.

Another object of the invention is to provide a welding method that prevents welding embrittlement.

To achieve the aforementioned objectives, a cleaning system is provided, comprises: a body to ensure that the elements of the cleaning system are positioned on and the cleaning system remains as a whole, • an inlet channel positioned on the body to provide compressed gas entry to the cleaning system,

• at least one channel inside the body to transmit the compressed air coming from the inlet channel to ensure that the non-ferrous metals in the liquid form that cause liquid metal embrittlement on the surface of the welding area are collected at a single point,

• a suction hole at the end of the body to enable the suction of the molten metals collected by the compressed air from the channel,

• a suction channel connected to the suction hole to allow the molten metals collected by the suction hole to be taken to the outside area,

• a distribution channel to ensure that the compressed gas from the inlet channel is homogeneously distributed to the channels.

To achieve the aforementioned objectives, a welding method is provided, comprises the following steps:

• providing the required temperature for the coating metal that causes liquid metal embrittlement to transition to the liquid phase in the welding area,

• melting the non-ferrous metals in the welding area,

• cleaning the welding area by suctioning the molten metals through a cleaning system by the cleaning system provided by this invention and taking them to the outside environment,

• performing the welding process.

The structural and characteristic features of the invention and all its advantages will be better understood through the detailed description written with reference to the figures provided below, and therefore, the evaluation should be made taking into account these figures and the detailed explanation.

Figures to Help Understanding of the Invention

Figure 1 is a front view of the cleaning system of the invention.

Figure 2 is a side sectional view of the cleaning system of the invention.

Figure 3 is another side sectional view of the cleaning system of the invention.

Figure 4 is a detailed view of the suction hole and channels.

Figure 5 is a detailed side sectional view of the suction hole and suction channel.

Figure 6 is a view showing the internal structure of the cleaning system of the invention.

Figure 7 is another view showing the internal structure of the cleaning system of the invention. Description of Part References

1. Body

2. Suction hole

3. Cap redirector

4. Inlet channel

5. Channel

6. Connection point

7. Distribution channel

8. Suction channel

A. Cleaning system

Detailed Description of the Invention

In this detailed description, the preferred structures and welding methods for preventing liquid metal embrittlement in the welding area subject to the invention and improving welding quality are explained only for the better understanding of the subject matter.

In the cleaning system (A) subject to the invention, body (1) is the part on which the other elements of the invention are positioned, ensuring that the cleaning system (A) stays as a whole.

The body (1 ) is mounted from connection point (6) to the machine to be used.

There is an inlet channel (4) on the body (1) and at least one channel (5) inside the body (1). Compressed gas enters the cleaning system (A) from the inlet channel (4), and this compressed gas is transmitted to channels (5) inside the body (1).

There is a suction hole (2) at the end of the body (1 ), and the suction hole (2) is in contact with a suction channel (8). The output points of the channels (5) are radially arranged around the suction hole (2). Compressed air from the channels (5) ensures that non-ferrous metals such as Zn, Cu, and Al that cause liquid metal embrittlement on the surface of the welding area are collected at a middle point around the diameter of the suction hole (2). The channels (5) are preferably adjustable in terms of output angle, allowing the exit angle of the compressed gas to be adjusted. The suction hole (2) is a truncated cone shape with a larger diameter near the outer surface of the body (1 ) to be able to suck the collected metals. The collected molten metals are taken out to the external area through the suction channel (8).

The distribution channel (7) ensures that the compressed gas from the inlet channel (4) is homogeneously distributed to the channels (5). Compressed gas is given simultaneously from opposite directions of the electrode to provide a homogeneous gas distribution. In the cleaning system (A), there is a fixed cap redirector (3) outside of which the record is mounted. As can be seen in Figure 4, since the channels (5) are open to the surface, an external shield, namely the cap redirector (3), is put on the channels (5) to prevent them from being disconnected and directed directly downwards when gas is blown from above. The cap redirector (3) directs the gas to the channels (5) in the nozzle. The cap redirector (3) is positioned a little above the electrode to prevent it from contacting the part during welding.

The cleaning system (A) can be used by positioning it on, outside, or in the center of the part to be welded.

The welding method using the cleaning system (A) is as follows: The temperature required for the coating metal to pass into the liquid phase, which causes liquid metal embrittlement in the welding area, is provided. Non-ferrous metals such as Zn, Cu, and Al that cause liquid metal embrittlement on the surface of the welding area are melted. This process can be called "coating melting pulse." The cleaning system (A) is used to suck the molten metal and eject it out of the welding area, and the coating is cleaned of molecules that cause contamination such as unwanted molten metals and oxides in the welding area. The welding process is applied to the cleaned welding area. This process can be called the "cleaning pulse." Since there is no substance in the welding area that causes liquid metal embrittlement, a welding process that does not cause liquid metal embrittlement is performed. This process can be called the "main welding pulse." The "coating melting pulse," "cleaning pulse," and "main welding pulse" processes mentioned in the invention welding method will be applied continuously without waiting time between them.

The welding process mentioned in the invention is preferably spot resistance welding.

In the invention, the molten non-ferrous coating layer metals can be removed from the surface by two alternative methods. The first is to remove the molten non-ferrous or non-ferrous coating metal from the channels (5) by blowing air. Here, heating is done with electrodes, and normal air can be blown or heating and blowing can be done with hot air. Here, the air mentioned will be heated enough to raise the non-ferrous coating metal to the melting temperature in an area. In addition to the first method mentioned, the molten non-ferrous metal can be removed from the surface by sucking it with an electrode with a suction hole (2) by heating the electrode.