Why is the spiral steel pipe preheated before welding

Views : 504
Update time : 2023-08-25 09:23:40

  The purpose of the spiral steel pipe preheating before welding is as follows:

  (1) Preheating can slow down the cooling rate after welding, make hydrogen diffuse in the weld metal and escape, and avoid cracking caused by hydrogen. It can also reduce the degree of hardening of welds and heat-affected zones to improve the crack resistance of welded joints.

  (2) Preheating can reduce welding stress. Uniform local or general preheating reduces the weld zone temperature (also known as temperature gradient) between welders. In this way, on the one hand, the welding stress is reduced, and on the other hand, the welding strain rate is reduced, thereby avoiding welding cracks.

  (3) Preheating can reduce the bonding degree of the welded structure, especially the bonding degree of the corner joints, reduce the occurrence of cracks, and increase the preheating temperature.

  The selection of welding preheating temperature and interpass temperature is not only related to the chemical composition of steel and electrode, the stiffness of welding structure, welding method, ambient temperature, etc., but these factors should also be considered and determined. In addition, the uniformity of preheating temperature has an important influence on the uniformity of the welding area in the thickness direction of the steel and the reduction of welding stress. The width of local preheating should be the possibility of welder restraint, generally three times the wall thickness around the weld zone, and not less than 150-200mm. If the preheating is uneven, not only will the welding stress not be reduced, but it will increase the welding stress.

Related News
Read More >>
Differences between API 5L steel pipes VS ASTM A53 steel pipes Differences between API 5L steel pipes VS ASTM A53 steel pipes
Jul .11.2024
What is the difference between API 5L steel pipes VS ASTM A53 steel pipes,Shengtian steel pipe facory will introduce to you the following: 
ASTM A53 A106 Carbon steel seamless pipe has been sent to Thailand ASTM A53 A106 Carbon steel seamless pipe has been sent to Thailand
Jul .09.2024
ASTM A53 carbon steel pipe and ASTM A106 carbon steel pipe play an important role in oil and gas projects. Our factory can provide various standards of Seamless steel pipe including American, European, Russian, and Japanese standards, according to the different needs of different customers.
How to choose seamless stainless steel boiler pipe? How to choose seamless stainless steel boiler pipe?
Jul .05.2024
The seamless stainless steel boiler pipe is a common heat conversion equipment in our lives, and the boiler stainless steel pipe, as an important part of the boiler, plays a vital role in it.Stainless steel pipes play a vital role in the industrial and construction fields. Choosing the right model specifications is crucial to the success of engineering projects.
Why does thick-walled stainless steel pipe deform during heat treatment? Why does thick-walled stainless steel pipe deform during heat treatment?
Jul .02.2024
The performance of thick-walled stainless steel pipes will be better after heat treatment, and it will be more in line with the performance requirements of mechanical parts. However, during the heat treatment process, metal materials will have problems such as deformation.