What is hot-rolled seamless steel pipe?

Seamless steel pipe is a steel pipe made from a whole round steel perforated without welded seams on the surface, called seamless steel pipe. According to the production method, seamless steel pipe can be divided into hot-rolled seamless steel pipe, cold-rolled seamless steel pipe, cold-drawn seamless steel pipe, extruded seamless steel pipe, top tube and so on. Cold rolled seamless steel pipe is a steel pipe that is rolled below the crystallization temperature, while hot rolled seamless steel pipe is a steel pipe that is rolled above the crystallization temperature.

Advantages of hot-rolled seamless steel pipe

The casting organization of the ingot can be destroyed, refining the grain of steel and eliminating microstructural defects, so that the steel organization is dense and the mechanical properties are improved. This improvement is mainly reflected in the direction of rolling, so that the steel is no longer isotropic to a certain extent; bubbles, cracks and looseness formed during casting can also be welded together under high temperature and pressure.

Disadvantages of hot-rolled seamless steel pipe

1. After hot rolling, the non-metallic inclusions inside the steel (mainly sulfides and oxides, and silicates) are pressed into thin sheets, and the phenomenon of delamination (lamination) occurs. Delamination greatly deteriorates the properties of the steel in tension along the thickness direction, and there is a risk of interlaminar tearing during weld shrinkage. The local strain induced by weld shrinkage often reaches several times the yield point strain, which is much larger than the load-induced strain.

2. Residual stresses caused by uneven cooling. Residual stress is the internal self-equilibrium stress in the absence of external forces, a variety of cross-sectional hot-rolled steel have such residual stresses, generally the larger the cross-sectional size of the steel, the greater the residual stress. Although the residual stress is self-balancing, but the performance of steel members under the action of external forces still has a certain impact. Such as deformation, stability, fatigue resistance and other aspects may have a negative effect.

3. Hot-rolled steel products, for the thickness and edge width of this aspect is not good control. We are familiar with thermal expansion and contraction, as the beginning of the hot rolled out even if the length and thickness are up to standard, the final cooling will still appear a certain negative difference, the wider the negative side width, the thicker the performance of the more obvious. Therefore, it is impossible to be too precise about the width, thickness, length, angle, and edge line of the steel for large size steel.

Classification of hot-rolled 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, etc.

Seamless steel pipe for general use: it is made of 10, 20, 30, 35, 45 and other high quality carbon knotted steel 16Mn, 5MnV and other low alloy structural steel or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other alloy steel hot rolled or cold rolled. 10, 20 and other low carbon steel seamless pipe is mainly used for fluid transportation pipeline. 45, 40Cr and other medium carbon steel seamless pipe is used to The seamless tubes made of 45, 40Cr and other medium carbon steels are used to manufacture mechanical parts, such as the stressed parts of automobiles and tractors. Seamless steel tubes are generally used to ensure strength and crush test. Hot-rolled steel pipe is delivered in hot-rolled state or heat-treated state; cold-rolled is delivered in heat-treated state.

Cangzhou Shenlong Pipe Manufacturing Co., Ltd. is an enterprise specializing in the production, processing and sales of various steel pipes and pipe fittings, with production base in Cangzhou, Hebei Province. It was founded in 1992, covering an area of more than 60,000 square meters, with more than 200 employees (including 30 inspectors) and an annual production capacity of about 150,000 tons of steel pipes and 40,000 tons of pipe fittings. We can provide first-class quality and professional technical service! Welcome to contact us!