The hottest laser is used for welding stainless st

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Laser welding of stainless steel tubes

in recent years, as people pay more and more attention to environmental issues, automobile manufacturers are under increasing pressure to improve fuel efficiency. Stricter and more restrictive regulations have brought technical challenges to industrial production and material processing. Whether the measurement accuracy of these loads meets or exceeds the standards of astm4 and iso7500/1 The load sensor should also consider: range, accuracy, repeatability, offset loading fault, nonlinearity, stable compensation range, temperature zero drift and sensitivity The automatic identification, calibration and zeroing of the load sensor greatly speeds up the experimental process and ensures the consistency and accuracy of the data Other trends include lower exhaust emissions, lighter bodies, and longer service life of parts

the progress in material processing has brought unique opportunities to the field of stainless steel pipe production. Specifically, manufacturers are required to produce such parts, which must have lighter weight, but must still have anti-corrosion characteristics and meet the strength requirements. In addition, the spatial limitations of the body emphasize the importance of formability. Typical applications include exhaust pipes, fuel pipes, fuel injectors, and other components

in the production of stainless steel pipes, the flat steel strip is formed first, and then its shape becomes a circular tube. Once formed, the joints of the pipes must be welded together. This weld greatly affects the formability of the part. Therefore, in order to obtain the welding shape that can meet the strict testing requirements in the manufacturing industry, it is extremely important to select the appropriate welding technology. There is no doubt that gas tungsten arc welding (GTAW), high frequency (HF) welding and laser welding have been respectively applied in the manufacture of stainless steel pipes

high frequency induction welding

in high frequency contact welding and high frequency induction welding, the equipment providing current and the equipment providing extrusion force are independent of each other. In addition, both methods can use a magnetic rod, which is a soft magnetic element, which is placed inside the tube body, which helps to converge the welding flow at the edge of the steel strip

in both cases, the steel strip is cut and cleaned, rolled up, and then sent to the welding point. In addition, 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 great force is exerted on the extrusion pulley to avoid porosity in the welding area; However, the use of a larger extrusion force will lead to an increase in burrs (or weld beads). Therefore, specially designed cutters are used to remove burrs inside and outside the tubes

One of the main advantages of high-frequency welding process is that it can process steel pipes at high speed. However, the typical situation in most solid-phase forging is that it is not easy to reliably test the joints of high-frequency welding if traditional nondestructive technology (NDT) is used. Welding cracks may appear in the flat and thin area of low-strength joints, which cannot be detected by traditional methods, so it may lack reliability in some high-demand automotive applications

gas tungsten arc welding (GTAW)

traditionally, steel pipe manufacturers choose to complete the welding process with gas tungsten arc welding (GTAW). GTAW generates a welding arc between two non expendable 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 a process that has been established and understood by people, and it will be able to repeat and complete the high-quality welding process

the advantage of this process is repeatability, no spatter in the welding process, and the elimination of porosity. GTAW is considered to be an electrical conduction process, so the process is relatively slow

high frequency arc pulse

in recent years, GTAW welding power supply, also known as high-speed switch, makes the arc pulse exceed 10000hz. The customers of steel pipe processing plants are the first to benefit from this new technology. The downward pressure of arc caused by high-frequency arc pulse is five times greater than that of traditional GTAW. The representative improvement characteristics also include: the blasting strength is increased, the welding line speed is faster, and the waste products are reduced

customers of steel pipe manufacturers soon found that the welding shape obtained by this welding process needs to be reduced. In addition, the welding speed is relatively slow

laser welding

in all steel pipe welding applications, the edge of the steel strip is melted. When the edge of the steel pipe is extruded together with a clamping bracket, the edge solidifies. However, for laser welding, its unique property is that it has high energy beam density. The laser beam not only melted the surface layer of the material, but also produced a keyhole, so that the weld shape was very narrow

if the power density is lower than 1 mw/cm2, such as GTAW technology, it will not produce enough energy density to produce keyholes. In this way, the welding shape obtained by keyhole free process is wide and shallow. The high precision of laser welding brings more efficient penetration, which reduces grain growth and brings better metallographic quality; On the other hand, higher heat input and slower cooling process of GTAW lead to rough welding structure

generally speaking, people think that the laser welding process is faster than GTAW, and they have the same scrap rate, while the former brings better metallographic characteristics, which brings higher blasting strength and higher formability. When compared with high-frequency welding, laser processing of materials does not occur oxidation, which makes the scrap rate lower and the formability higher

influence of spot size

in the welding of stainless steel pipe factory, 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 and achieve higher speed at the same time. When choosing the most suitable laser, people should not only consider the beam quality, but also the accuracy of the pipe mill. In addition, the limitation of reducing the light spot must be considered before the dimensional error of the pipe mill takes effect

there are many unique dimensional problems in steel pipe welding. However, the main factor affecting welding is the joint on the welding box (more specifically, the welding roll). Once the steel strip is formed and ready for welding, the characteristics of the weld include: steel strip gap, serious/slight welding dislocation, and changes in the centerline of the weld. The gap determines how much material is used to form the weld pool. Too much pressure will lead to excess material on the top or inside diameter of the steel pipe. On the other hand, serious or slight welding dislocation will lead to poor welding appearance

in addition, after welding the box, the steel pipe will be further trimmed. This includes size adjustment and shape (shape) adjustment. On the other hand, additional work can remove some serious/slight welding defects, but it may not be able to remove them all. Of course, we hope to achieve zero defects. Generally speaking, the rule of thumb is that welding defects should not exceed 5% of the material thickness. Beyond this value, The spokesman of mtorres company said, "at present, the strength of connected products.

finally, the existence of welding centerline is very important for the production of high-quality stainless steel pipes. With the increasing emphasis on formability in the automotive market, it is directly related to the need for smaller heat affected zone (HAZ) And reduce the welding profile. In turn, this will promote the development of laser technology, that is, improve the beam quality of light detection data uploaded to the municipal food safety monitoring platform in real time to reduce the spot size. As the spot size becomes smaller, we need to pay more attention to the accuracy of scanning the centerline of the seam. Generally speaking, steel pipe manufacturers will try to reduce this deviation as much as possible, but in fact, it is difficult to achieve a deviation of 0.2mm (0.008 inch)

this brings the need to use a seam tracking system. The two most common tracking techniques are mechanical scanning and laser scanning. On the one hand, the demand of Japanese automobile industry drives the development of plastic processing machinery industry. The mechanical system uses probes to contact the upstream of the joint of the welding pool, which will be stained with ash, worn and vibrated. The accuracy of these systems is 0.25mm (0.01 inch), which is not accurate enough for laser welding with high beam quality

on the other hand, laser seam tracking can achieve the required accuracy. Generally speaking, the laser light or laser spot is projected on the weld surface, and the obtained image is fed back to the CMOS camera, which determines the position of the weld, wrong joint and gap through algorithm

although the imaging speed is very important, when providing the necessary closed-loop control to move the laser focusing head directly on the seam, the laser seam tracker must have a controller fast enough to accurately compile the position of the seam. Therefore, the accuracy of seam tracking is very important, and the response time is also important

in general, the seam tracking technology has been fully developed, and it can also allow steel pipe manufacturers to use higher quality laser beams to produce stainless steel pipes with better formability

therefore, laser welding has found a place to play. It is used to reduce the porosity of welding, reduce the welding shape, and maintain or improve the welding speed at the same time. Laser systems, such as diffusion cooled slab lasers, have improved beam quality and further improved formability by reducing welding width. This development has led to the need for stricter dimensional control and laser weld tracking in steel pipe plants

in this way, the success of the welding process in stainless steel pipe factory depends on the integration of all individual technologies, so it must be treated as a complete system. (end)

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