Seamless steel pipes are divided into two types: hot-rolled and cold-drawn seamless steel pipes. Hot rolled steel pipes are divided into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, geological steel pipes and other steel pipes.

Folds and internal cracks in medium and low pressure boiler tubes are the most common forms of defects. Internal folds and internal cracks may be distributed along the entire length of the steel pipe, or located only at both ends or part of the length. When rolling alloy steel pipes, inward folding is particularly easy to occur, and rolling general carbon steel pipes sometimes occur.

Spiral steel pipe is a spiral seam steel pipe made of strip steel coils as raw materials, often extruded and formed by automatic double-wire double-sided submerged arc welding.

The rapid cooling of steel pipes after rolling has obvious effects on the production of bearing steel pipes, reducing network carbides, improving the pearlite structure, and shortening the spheroidizing annealing time.

The forming technologies of large-size seamless pipe fittings mainly include: hot spinning, hot extrusion, hot piercing and rolling, and hot pushing and expanding.

This method includes the setting of the furnace temperature and holding time in two passes.