In industrial production, straight-seam steel pipes tend to have two choices, one is to use ordinary straight-seam steel pipe, the other option is to have good performance of straight-seam steel pipe. In the long-term production practice process, enterprises have generally formed a consensus that this has many good characteristics of straight-seam steel pipe in many ways better than ordinary straight-seam steel pipe. The reason why this straight-seam steel pipe is slightly better than the ordinary straight-seam steel pipe, mainly because this straight-seam steel pipe has several characteristics that ordinary straight-seam steel pipe does not have.
One of these characteristics refers to the high aberration of the straight-seam steel pipe itself. The straight-seam steel pipe in pipeline transportation often needs to bear a lot of friction, in the process of pipe transportation, when the material passes through the pipe, the part of the elbow often produces great friction, especially when using the pipe to transfer solid material, the pipe in the place of the straight-seam steel pipe will produce a large impact and friction, these impact and friction force is likely to cause great damage to the straight-seam steel pipe. Ordinary straight-seam steel pipes often have no way to withstand such shocks and frictions, and the use of far-reaching ceramic elbows can greatly enhance the elbow's resistance to impact and friction.
Not only in terms of friction, ceramic elbows are also very good in terms of. In the process of transmission, the material and the pipe produce a great deal of friction, which produces a high amount of heat, especially at the bend, this high temperature is obvious.
Ordinary straight-seam steel pipe is likely to deform or damage at high temperatures, and this ceramic straight-seam steel pipe tends to have a relatively high temperature resistance characteristics, that temperature characteristics make this straight-seam steel pipe can withstand this high temperature, so that the clock straight-seam steel pipe has a long life.
The application of surface non-destructive detection is carried out in accordance with the standard requirements, and its detection objects and applications are generally as follows:
1, straight-seam steel pipe material quenching tendency of larger welding joint bee port detection.
2, the design temperature is lower than or equal to minus 29 degrees Celsius non-Austial stainless steel pipe slope detection.
3, double-sided welding parts provide for the root of the weld after the root detection.
4, when the use of oxyacetylene flame cutting has a hardening tendency on the alloy pipe welding card, the defect detection of the grinding site.
5, straight-seam steel pipe material outside the surface quality inspection.
6, pay attention to butt weld surface defect detection.
7, pay attention to the straight seam steel pipe angle weld surface defect detection.
8, pay attention to the welding joint surface defect detection of the plug welding and the cross-joint three-way branch.
9, straight-seam steel pipe bending after surface defect detection.
Production conditions for straight-seam steel pipes:
1, welding
Large diameter straight seam steel pipe generally uses high-frequency welding, high-frequency welding is a kind of induction welding (or pressure contact welding), it does not need weld fillers, no weld splash, welding thermal impact area narrow, welding molding beautiful, welding machinery performance is good and other advantages, so in the production of steel pipe has been widely used. According to the principle of electromagnetic induction and ac charge in the conductor skin effect, proximity effect and vortex heat effect, so that the steel at the edge of the weld is partially heated to the melting state, by the roller extrusion, so that the weld to achieve crystal indirect integration, so as to achieve the purpose of weld welding, cooling to form a solid straight seam weld.
2, weld clearance
The strip steel is fed into the weld pipe unit, through the multi-roll rolling pressure, the strip steel gradually rolled up, forming a circular pipe billet with an opening gap, adjust the pressure of the extrusion roller, so that the weld gap is controlled at 1 to 3mm, and the weld port is flat at both ends. If the gap is too large, it will cause the proximity effect to decrease, the vortex heat is insufficient, the weld crystal indirectly does not fit well and produces no fusion or cracking. If the gap is too small, the adjacent effect is increased, the welding heat is too large, resulting in weld burn damage, or the weld is squeezed, rolling pressure after the formation of a deep pit, affecting the quality of the weld surface.
3, welding temperature
Low-carbon steel, welding temperature control in 1250 to 1460 degrees C, to meet the pipe wall thickness of 3 to 5mm welding through requirements. Welding temperature is mainly controlled by regulating high-frequency vortex thermal power and welding speed. When the input heat is insufficient, the edge of the heated weld does not reach the weld temperature, the metal tissue remains solid, forming an unmelted or unwelded, and when the input heat is too large, the edge of the heated weld exceeds the welding temperature, resulting in over-burning or melting droplets, which cause the weld to form a melting hole.
