Precautions when welding spiral steel pipe

It is imperative to weld and cut the spiral steel pipe structure in the application of 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 numerous defects in its welded joint and heat-affected zone (HAZ). The welding performance of the spiral steel pipe is mainly manifested in In the following aspects, the high-temperature crack referred to here refers to the cracks related to welding. Elevated temperature cracks can be roughly divided into solidification cracks, micro-cracks, HAZ (heat affected zone) cracks, and reheating cracks. Low-temperature cracks sometimes occur in spiral steel pipes. Because the main reason for this is hydrogen diffusion, the degree of confinement of the welded joint, and the hardened structure, the main solution is 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 to ensure 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 influences 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 noticeable decrease in the toughness of welded joints of high-purity ferritic stainless steel is due to the mixing of carbon, nitrogen, and oxygen.