As a new type of material, stainless steel has been widely used in aerospace, auto parts and other fields because of its corrosion resistance and formability.
The application of laser welding in stainless steel occupies a very important position, especially in the automotive industry, the body is all connected by welding.
However, due to the influence of many factors, stainless steel plate welding has the problem of deformation, and it is difficult to control, which is not conducive to the sustainable development of related fields.
Therefore, it is of great significance to strengthen the research on laser welding deformation of stainless steel plate.
1. Overview of laser welding
In the process of laser welding, when the laser irradiates the surface of the material to be welded, part of it will be reflected and the rest will be absorbed to enter the material to complete the welding target.
In brief, the process of laser welding is to use the high-power laser beam focused by the optical system to irradiate the surface of the material to be welded, then make full use of the light energy absorption of the material to heat and other treatment, and finally form a welding joint after cooling.
In general, laser welding is mainly divided into thermal conduction welding and deep penetration welding.
2. Damage of welding deformation and main factors affecting welding deformation
The main factors affecting welding deformation are welding current, pulse width and frequency.
With the increase of welding current, the weld width increases, and spatter appears gradually, which leads to oxidation deformation and roughness on the weld surface;
When the pulse width reaches a certain extent, the heat conduction energy consumption of the material surface also increases.
Evaporation makes the liquid splash out from the molten pool, which leads to the decrease of the cross-sectional area of the solder joint and affects the strength of the joint;
The influence of welding frequency on welding deformation of stainless steel plate is closely related to the thickness of steel plate.
For example, for 0.5 mm stainless steel plate, when the frequency reaches 2 Hz, the weld overlap rate is higher;
When the frequency reaches 5 Hz, the welding seam burns seriously, the heat-affected zone is wide, and the deformation occurs.
Therefore, it is imperative to strengthen the effective control of welding deformation.
3. Effective measures to avoid laser welding deformation
In order to reduce the deformation of laser welding and improve the welding quality of stainless steel plate, it can start from optimizing the welding process parameters, and the specific operation methods are as followed:
3.1 Actively introduce the orthogonal experiment method
The orthogonal experiment method mainly refers to a kind of mathematical statistics method through orthogonal table analysis and arrangement of multi-factor experiments.
It can use less experiments to obtain effective results and infer the best implementation scheme.
At the same time, it can also conduct in-depth analysis, obtain more relevant information, and provide the basis for specific work.
Generally, welding current, pulse width and laser frequency are selected as the key objects, and the welding deformation is regarded as the index and controlled at the minimum.
It needs to adhere to the principle of rationality and control the level of factors in an appropriate range.
For example, for the stainless steel plate with a thickness of 0.5 mm, the current can be controlled between 80~96 I/A and the frequency between 2~5 f/Hz.
3.2 Selection of orthogonal table
In general, the level number of experimental factors should be consistent with the level number in orthogonal table, and the number of factors should be less than the number of columns in orthogonal table.
Reasonable design of orthogonal table can provide corresponding support and help for the follow-up research.
3.3 Range analysis of test results
According to the test results of stainless steel plate with thickness of 0.5 mm, the range difference of each column is not equal, which proves that different levels of each element have particularity, and the influence is not the same.
The order of influence on laser welding deformation is current, pulse width and frequency.
Considering all the factors, the best welding process parameters of laser should be controlled as follows: current 85 A, pulse width 7 ms, frequency 3 Hz.
The welding process parameters should be controlled in three values to ensure the minimum welding deformation of stainless steel plate with thickness of 0.5 mm.
For the stainless steel plate with the thickness of 0.8 mm, the current, pulse width and frequency should be controlled at 124 A, 8 ms and 4 Hz respectively to ensure the minimum deformation on the basis of meeting the tensile strength of the weld.
The thickness of stainless steel plate is 160 A, 11 ms, 5 Hz.
In the process of laser welding, the welding personnel control the parameters in a reasonable range, which can not only improve the welding quality and efficiency, but also avoid the deformation of steel plate and meet the production demand.
With the rapid development of science and technology, the control of welding deformation technology also develops, such as the application of finite element simulation in welding deformation control.
Through the use of welding temperature and stress to avoid welding deformation, the stress balance of stainless steel plate can be improved.
While avoiding steel plate welding deformation, the welding quality can be improved to promote the healthy development of related fields.
According to the above, as an effective welding technology, laser welding technology plays a positive role in improving the welding quality.
However, due to the influence of laser current and other factors, stainless steel plate laser welding has deformation and other problems.
So the welding personnel can take the orthogonal experiment method to obtain the best process parameters of different thickness steel plate, combined with the welding parameters to continuously improve the welding quality, so as to avoid the occurrence of steel plate deformation.
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