In laser welding, what kind of blowing method could we choose, how to select principle of shielding gas?
1) Blowing method
There are currently two main methods of blowing protective gas: one is paraxial side blown protective gas, as shown in Figure 1; the other is coaxial protective gas, as shown in Figure 2.
How to choose the two blowing methods is a comprehensive consideration of many aspects. Generally, it is recommended to use the side blowing protective gas method.
2) Selection principle of blowing method
First of all, it needs to be clear that the so-called "oxidation" of the weld is only a common name. In theory, it means that the chemical reaction between the weld and the harmful components in the air leads to the deterioration of the quality of the weld. It reacts chemically with oxygen, nitrogen and hydrogen in the air.
To prevent the weld from being "oxidized" is to reduce or avoid the contact of such harmful components with the weld metal at high temperature. The pool metal solidifies and its temperature drops below a certain temperature throughout the time period.
Case analysis
For example, titanium alloy welding can quickly absorb hydrogen when the temperature is above 300°C, quickly absorb oxygen when it is above 450°C, and quickly absorb nitrogen when it is above 600°C, so the titanium alloy weld is solidified and the temperature drops to 300°C All of the following stages need to be effectively protected, otherwise they will be "oxidized".
It is not difficult to understand from the above description that the blown shielding gas not only needs to protect the weld pool in a timely manner, but also needs to protect the area that has been welded and just solidified, so the paraxial side shown in Figure 1 is generally used Blow shielding gas, because the protection range of this method is wider than that of the coaxial protection method in Figure 2, especially for the area where the weld has just solidified.
For engineering applications, not all products can use side-shaft side-blown protective gas. For some specific products, only coaxial protective gas can be used. Specifically, it needs to be determined from the product structure and joint form. targeted selection.
1. Selection of specific protective gas blowing methods
1) Straight line weld
If the weld seam shape of the product is straight, the joint form can be butt joint, lap joint, female angle joint or lap joint. For this type of product, it is better to use the shielding gas method of side-axis side blowing.
2) Plane closed graphic welds
If the shape of the weld seam of the product is a closed shape such as a plane circumference, a plane polygon, a plane multi-segment line, etc., the joint form can be butt joints, lap joints, lap joints, etc., and all products of this type use coaxial shielding gas. way is better.
2. Conclusion
The selection of shielding gas directly affects the quality, efficiency and cost of welding production. However, due to the diversity of welding materials, the selection of welding gases is also relatively complicated in the actual welding process. It is necessary to comprehensively consider welding materials, welding methods, welding positions and For the required welding effect, a more suitable welding gas can be selected through the welding test to achieve better welding results. If you also have questions about the laser welding industrial tube rolling and forming machine, please contact Hangao (SEKO) Team for exchange and consultation.
