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Improvement of Welding Process of Automatic Laser Tailor Welding Line

by:VENTECH     2022-04-19

Abstract: This article focuses on the new problems that arise in the mass production of our company’s fully automatic laser tailored welding line in the process of welding 0.7mm to 1.4mm ultra-thin carbon steel plates. After research and analysis in many aspects, the system has Improve and perfect, and finally solve the problem.


Keywords: shielding gas, laser spot mode, weld forming


1. Overview


Laser tailor-welded blanks are flat blanks that use laser processing technology to weld flat materials of different thicknesses, different materials or different surface coatings together before the parts are stamped and formed. Laser tailor-welded blanks are widely used in the automotive industry. With the unremitting efforts of our company's engineers, the cold-rolled thin steel plates of general thickness (1mm-2mm) are tailor-welded, and the welding process is relatively mature.


With the diversified development of welding products, new problems have arisen in the mass production process of tailor-made laser welding of 0.7mm to 1.4mm ultra-thin carbon steel plates.


2. The emergence of on-site problems


The problems reported by customers on site are as follows: 1. Cup convex test, the weld cracked in the heat induction zone; 2. The back forming width of the weld was too large; 3. The back forming pile height of the weld was too large; 4. High power (>3000w) cannot stabilize welding. After the flat blank is welded, the stamping and forming failure rate is relatively high. As shown below:



3. Problem analysis and solutions


Field equipment configuration: 1. Our company independently researched and developed automatic laser tailor-welding line; 2. Keweijing CQ series 4500 laser, spot mode: welding mode; 3 Cooke 300mm focal length reflective focusing lens; 4. Welding shielding gas: Argon


3.1. The influence of spot mode on weld formation


For high-power CO2 lasers, the cutting die can get a larger aspect ratio than the welding die; and under the same process parameters, the weld shape of the cutting die is thinner than that of the welding die. We can choose the laser mode for different product needs.


3.2. The effect of defocusing amount on weld formation


The amount of defocus affects the size of the laser spot on the surface of the weldment, and therefore has a greater impact on the welding penetration, the width of the weld and the cross-sectional shape of the weld.


3.3. The influence of plasma on weld formation


Plasma control is one of the key technologies to solve high-power CO2 laser welding. The method of side blowing auxiliary gas is used on site to compress the plasma control in the molten pool groove.


The actual processing on site found that when the height of the side blowing nozzle is about 3mm, the plasma cloud area is the smallest, and the coupling effect between the laser energy and the workpiece is the best. The use of high-purity nitrogen or helium or a mixture of helium and argon can suppress the plasma cloud to a minimum. When the power of the laser is greater than 3000w, the plasma cloud is in an unstable and fluctuating state.


After the above analysis, we have made a corresponding solution:


Change the laser laser mode and change the welding mode to cutting mode. The problems of cupping test cracking in the thermal induction zone and over-width forming on the back of the weld have been effectively solved.


Considering that the use of high-purity nitrogen as a shielding gas is likely to produce 'trachoma' and the cost of helium, the pure argon is changed to a mixture of helium and argon, and the back of the weld is high and high power is not possible The problem of stable welding has been effectively solved.


4. Summary


From the point of view of welding process, the above solutions may not be the best solution, but for the use of field equipment, it is indeed the best way to deal with the problem.


This article is an original manuscript, please indicate the source for reprinting.

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