It is inevitable to weld and cut the spiral steel pipe structure of the application of a spiral steel pipe. Because of the characteristics of the spiral steel pipe itself, the welding and cutting of the spiral steel pipe have its particularity compared with ordinary carbon steel, and it is easier to produce various defects in its welded joint and heat-affected zone (HAZ). The welding performance of the spiral steel pipe is mainly manifested in the following aspects, the high-temperature cracked referred to here refer to the cracks related to welding. High-temperature cracks can be roughly divided into solidification cracks, micro-cracks, HAZ (heat-affected zone) cracks, and reheating cracks.
Low-temperature cracks sometimes to occur to spiral steel pipes. Because the main causes of this is hydrogen diffusion, the degree of confinement of the welded joint, and the hardened structure, the main solution are to reduce the diffusion of hydrogen during the welding process, and appropriately perform preheating and post-weld heat treatment and reduce the degree of confinement.
The toughness of welded joints in spiral steel pipes is to reduce the susceptibility to high-temperature cracks, and the composition is usually designed so that 5%-10% of ferrite remains. However, the presence of these ferrites leads to a decrease in low-temperature toughness.
When the spiral steel pipe is welded, the amount of austenite in the welded joint area decreases, which affects the toughness. Also, with the increase of ferrite, its toughness value has a significant downward trend. It has been proved that the reason for the obvious decrease in the toughness of the welded joint of high-purity ferritic stainless steel is due to the mixing of carbon, nitrogen, and oxygen.