For welded pipes of special materials, heat treatment must be carried out before and after welding, which is very important to the welding quality. The pre-heating of welded pipes made of special materials can not only slow down the cooling rate after welding, but also help hydrogen diffuse and escape from the weld metal to avoid hydrogen-induced cracking. At the same time, the degree of hardening of the weld seam and the heat-affected zone is reduced, and the crack resistance of the welded joint is improved.

Large-diameter LSAW pipes are widely used in natural gas, petroleum, chemical industry, octg pipe and other fields, and generally refer to straight seam steel pipes with an outer diameter of 500mm or more.

Welded steel pipe slag inclusions are slag that remains inside the weld. Welding slag inclusions are generally divided into two categories:The first category is metal slag inclusions. The second category is non-metallic slag, which refers to the slag remaining in the weld after welding, including electrode coating or flux, sulfide, oxide and nitride. According to its formation, it can be divided into point-like slag inclusions, linear slag inclusions, chain-like slag inclusions and dense slag inclusions.

It is cold drawn seamless pipe, which is to draw the metal pipe with a cold drawing machine without heating. The advantage is that it does not need to be carried out at high temperature. The disadvantage is that the residual stress is large, and it cannot be drawn too long. Cold drawing can improve toughness and tensile strength to obtain better mechanical properties.

Some difficulties are often encountered in the construction of steel sheet piles, and the following methods are often used to solve them:

Common steel pipes (such as seamless pipes or welded steel tubes) are 12 meters long and can be placed in the cabin. If the steel pipe is placed on the deck, it must be carefully tied to avoid damage during shipping.