To weld stainless steel pipes, a flat steel strip is formed first, and then the shape becomes a round tube. Once formed, the seams of the stainless steel pipe must be welded together. This weld greatly affects the formability of the part. Therefore, in order to obtain a welding profile that can meet the strict test requirements in the manufacturing industry, it is extremely important to select the appropriate welding technology. Undoubtedly, gas tungsten arc welding (GTAW), high frequency (HF) welding, and laser welding have been applied in the manufacture of stainless steel pipes.
In all steel pipe welding applications, the edges of the steel strip are melted, and when the steel pipe edges are squeezed together using the clamping bracket, the edges solidify. However, the unique property of laser welding is its high-energy beam density. The laser beam not only melts the surface of the material, but also creates a keyhole, so that the weld seam is very narrow.
Generally speaking, people think that the laser welding process is faster than GTAW, they have the same rejection rate, and the former brings better metallographic properties, which brings higher blasting strength and higher formability. When compared with high-frequency welding, the laser processing material does not oxidize, which results in a lower rejection rate and higher formability.
In the welding of stainless steel pipe factories, the welding depth is determined by the thickness of the steel pipe. In this way, the production goal is to improve formability by reducing the welding width while achieving higher speeds. When choosing the most suitable laser, one must not only consider the beam quality, but also the accuracy of the tube mill. In addition, before the dimensional error of the pipe rolling mill takes effect, it is necessary to consider the limitation of reducing the light spot.
There are many unique dimensional problems in steel pipe welding. However, the main factor affecting welding is the seam on the welding box. Once the steel strip is formed and prepared for welding, the characteristics of the weld include: strip gap, severe/slight welding misalignment, and change in the center line of the weld. The gap determines how much material is used to form the weld pool. Too much pressure will result in excess material on the top or inner diameter of the stainless steel welded pipe. On the other hand, severe or slight welding misalignment can lead to poor welding appearance.
In both cases, after the steel strip is cut and cleaned, it is rolled up and sent to the welding point. In addition, a coolant is used to cool the induction coil used in the heating process. Finally, some coolant will be used in the extrusion process. Here, a lot of force is applied to the squeeze pulley to avoid porosity in the welding area; however, using a larger squeeze force will result in an increase in burrs (or weld beads). Therefore, specially designed cutters are used to remove burrs inside and outside the pipe.
One of the main advantages of the high-frequency welding process is that it can process steel pipes at high speeds. However, a typical situation in most solid phase forging joints is that it is not easy to reliably test the joints of high-frequency welding if the traditional non-destructive technology (NDT) is used. Welding cracks may appear in flat and thin areas of low-strength joints. Such cracks cannot be detected using traditional methods, and therefore may lack reliability in some demanding automotive applications.
Traditionally, steel pipe manufacturers choose to complete the welding process with gas tungsten arc welding (GTAW). GTAW creates an electric welding arc between two non-consumable tungsten electrodes. At the same time, inert shielding gas is introduced from the spray gun to shield the electrode, generate ionized plasma flow, and protect the molten weld pool. This is an established and understood process, and it will be repeatable to complete a high-quality welding process.
In this way, the success of the stainless steel pipe factory welding process depends on the integration of all individual technologies, so it must be treated as a complete system. Hangao Tech(SEKO Machinery) has over 20 years' experience in the stainless steel welding pipe manufacturing. Moreover, we are the only one manufacturer who could combine all processing like forming and welding, weld bead leveling, bright annealing, polishing and ect. in China. If you have any doubt about stainless steel industrial welding tube production line. Just feel free to contact us.
