Basic knowledge of steel pipe
Steel pipe is a kind of hollow strip steel, which is widely used as a pipeline for transporting fluids, such as oil, natural gas, water, gas, steam, etc. In addition, when the bending strength and torsion strength are the same, the weight is lighter, so it is also widely used for manufacturing mechanical parts and engineering structures, and is also commonly used for producing various conventional weapons, barrels, shells, etc.
Classification of steel pipes: Steel pipes are divided into seamless steel pipes and welded steel pipes (welded pipes). According to the section shape, it can be divided into round pipe and special-shaped pipe. Circular steel pipe is widely used, but there are some special-shaped steel pipes such as square, rectangle, semicircle, hexagon, equilateral triangle and octagon.
All steel pipes subjected to fluid pressure should be tested by hydraulic pressure to check their pressure resistance and quality. If there is no leakage, wetting or expansion under the specified pressure, it will be qualified. Some steel pipes should be subjected to curling test, flaring test and flattening test according to the standards or requirements of the buyer.
Seamless steel tube: Seamless steel tube is made of steel ingot or solid tube blank through perforation, and then made by hot rolling, cold rolling or cold drawing. The specification of seamless steel pipe is expressed by outer diameter * wall thickness in millimeters.Seamless steel tubes are divided into hot-rolled and cold-rolled seamless steel tubes.
Hot rolled seamless 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.
Cold-rolled (drawn) seamless steel pipes include common steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking steel pipes and other steel pipes, as well as carbon thin-walled steel pipes, alloy thin-walled steel pipes, stainless thin-walled steel pipes and special-shaped steel pipes.
Generally, the outer diameter of hot-rolled seamless pipe is larger than 32mm, and the wall thickness is 2.5-75mm; Cold-rolled seamless steel pipes can have an outer diameter of 6mm, a wall thickness of 0.25mm, and thin-walled pipes can have an outer diameter of 5mm and a wall thickness of less than 0.25mm. The dimensional accuracy of cold-rolled steel pipes is higher than that of hot-rolled steel pipes.
Generally, seamless steel pipes are made by hot rolling or cold rolling of excellent carbon bonded steel (10, 20, 35, 45), low alloy structural steel (16Mn, 5MnV) or bonded steel (40Cr, 30CrMnSi, 45Mn2, 40MnB).
Seamless pipes made of (10, 20) and other low carbon steels are mainly used for fluid conveying pipelines. Seamless pipes made of medium carbon steel such as (45, 40Cr) are used to manufacture mechanical parts, such as stress parts of automobiles and tractors. Generally, the strength and flattening test of seamless steel pipe should be ensured.
Hot-rolled steel pipes are delivered in hot-rolled or heat-treated state; Delivered by cold rolling and heat treatment.
