1. What is a steel pipe?
Steel pipe is a hollow long steel strip, which is widely used as a pipeline for conveying fluids, such as oil, natural gas, water, coal gas, steam, etc. In addition, when bending and torsional strength are the same, the weight is light, so it is also widely used in the manufacture of mechanical parts and engineering structures. It is also commonly used to produce various conventional weapons, gun barrels, shells, etc.
2. Classification of steel pipes?
Steel pipes are divided into two categories: seamless steel pipes and welded steel pipes (seamless pipes). According to the cross-sectional shape, they can be divided into round pipes and special-shaped pipes. Round steel pipes are widely used, but there are also some square, rectangular, semicircular, hexagonal, equilateral triangle, octagonal and other special-shaped steel pipes. For steel pipes that bear fluid pressure, hydraulic tests must be carried out to test their pressure resistance and quality. They are qualified if there is no leakage, soaking or expansion under the specified pressure. Some steel pipes must also be subjected to curling tests, expansion tests, flattening tests, etc. according to standards or requirements of the buyer.
3. What is a seamless steel pipe?
Seamless steel pipe is made of steel ingot or solid tube billet through perforation into rough tube, and then hot rolled, cold rolled or cold drawn. The specifications of seamless steel pipe are expressed by outer diameter * wall thickness in millimeters. Seamless steel pipe is divided into hot rolled and cold rolled (drawn) seamless steel pipe. Hot rolled seamless steel pipe is divided into general steel pipe, low and medium pressure boiler steel pipe, high pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, petroleum cracking pipe, geological steel pipe and other steel pipes.
4. What is cold rolled (drawn) seamless steel pipe?
In addition to general steel pipe, low and medium pressure boiler steel pipe, high pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, petroleum cracking pipe and other steel pipes, cold rolled (drawn) seamless steel pipe also includes carbon thin wall steel pipe, alloy thin wall steel pipe, stainless thin wall steel pipe and special steel pipe. The outer diameter of hot-rolled seamless pipes is generally greater than 32mm, with a wall thickness of 2.5-75mm. The outer diameter of cold-rolled seamless steel pipes can reach 6mm, with a wall thickness of 0.25mm. The outer diameter of thin-walled pipes can reach 5mm and the wall thickness is less than 0.25mm. Cold rolling has higher dimensional accuracy than hot rolling.
5. What are the general grades of seamless steel pipes?
Generally, seamless steel pipes are made of high-quality carbon steels such as 10.20.30.35.45, low-alloy structural steels such as 16Mn.5MnV, or alloy steels such as 40Cr.30CrMnSi.45Mn2.40MnB, which are hot-rolled or cold-rolled. Seamless pipes made of low-carbon steels such as 10.20 are mainly used for fluid delivery pipelines.
Seamless pipes made of medium-carbon steels such as 45.40Cr are used to manufacture mechanical parts, such as load-bearing parts of automobiles and tractors. Generally, seamless steel pipes must ensure strength and flattening tests. Hot rolled steel pipes are delivered in hot rolled or heat treated state; cold rolled steel pipes are delivered in hot or heat treated state.
