The Classification of Seamless Steel Pipe

Seamless steel pipe is divided into two categories, including hot-rolled and cold-rolled seamless steel pipe.

Hot-rolled seamless steel pipe contains general steel pipe, low and medium pressure boiler steel pipe, high pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, oil cracking pipe, geological pipe and other steel pipe.

In addition to the general steel pipe, cold-rolled seamless steel pipe also contains low pressure boiler steel pipe, high pressure boiler steel pipe, alloy steel pipe, stainless steel pipe, oil cracking pipe, other steel pipe, but also include carbon thin-walled steel pipe, alloy thin-walled steel pipe, stainless steel pipe, special-shaped steel tube.

The diameter of hot-rolled seamless pipe is generally greater than 32mm, wall thickness is 2.5-75mm, the diameter of cold-rolled seamless steel pipe can be 6mm, wall thickness can be 0.25mm, the diameter of thin tube can be 5mm, wall thickness is less than 0.25mm, Cold-rolled seamless steel pipe has higher dimensional accuracy than the hot-rolled seamless steel pipe.

The seamless steel pipe for general use: is made by 10,20,30,35,45 and other high-quality carbon steel, 16Mn, 5MnV and other low-alloy structural steel or 40Cr, 30CrMnSi, 45Mn2, 40MnB alloy steel by hot-rolled or cold rolled. The seamless steel pipe made by 10,20 and other low-carbon steel is mainly used for fluid transportation pipeline. The seamless steel pipe made by 45,40Cr and other carbon steel is mainly used to manufacture mechanical parts, such as cars, tractors force parts. The seamless steel pipe for general use should ensure strength and flattening test. The hot-rolled steel pipe is delivered in a hot-rolled state or a heat-treated state, cold-rolled steel is delivered in a heat-treated state.

Hot-rolled Seamless Steel Pipe

Hot-rolled seamless steel pipe is a large category of seamless steel pipe, which is divided according to the production method. Hot rolling is relative to cold rolling, cold rolling is carried out rolling at room temperature, and hot rolling is carried out rolling at the recrystallization temperature. Seamless steel pipe is named relative to the welded steel pipe, seamless steel pipe is usually made of round steel perforation and reprocessing, welded steel pipe is usually welded by steel plate in different ways. The diameter of hot-rolled seamless steel pipe is usually above 38mm. Seamless steel pipe with smaller diameter can be obtained by cold rolling or cold drawing.

The process of hot-rolled seamless steel pipe:

Hot-rolled seamless steel pipe is generally produced on automatic rolling mill units. The solid bar is inspected and cleared of surface defects. Then it is cut into the required length, and centered on face of the perforation end of the pipe billet. And then it will be sent to the heating furnace to heat, and bore a hole on the puncher. In the perforation, the solid bar will continue to rotate and forward at the same time, in the role of the roll and the head, the tube billet internal will be gradually formed cavity, that is said capillary. And then it will be sent to the automatic rolling mill to continue rolling. Finally, it will be reeled the wall thickness by reeling mill, sized by sizing mill, to achieve the specifications. It is a more advanced method that using continuous rolling mill to produce hot-rolled seamless steel pipe. Generally process of hot-rolled seamless steel pipe: round bars → heating → piercing → three-roll cross rolling, rolling or extrusion → detached → sizing (or reducing) → cooling → parison tube → straightening → hydrostatic test (or flaw detection) → mark → storage.

Hot-rolled Seamless Steel Pipe

Hot-rolled seamless steel pipe is a large category of seamless steel pipe, which is divided according to the production method. Hot rolling is relative to cold rolling, cold rolling is carried out rolling at room temperature, and hot rolling is carried out rolling at the recrystallization temperature. Seamless steel pipe is named relative to the welded steel pipe, seamless steel pipe is usually made of round steel perforation and reprocessing, welded steel pipe is usually welded by steel plate in different ways. The diameter of hot-rolled seamless steel pipe is usually above 38mm. Seamless steel pipe with smaller diameter can be obtained by cold rolling or cold drawing.

The process of hot-rolled seamless steel pipe:

Hot-rolled seamless steel pipe is generally produced on automatic rolling mill units. The solid bar is inspected and cleared of surface defects. Then it is cut into the required length, and centered on face of the perforation end of the pipe billet. And then it will be sent to the heating furnace to heat, and bore a hole on the puncher. In the perforation, the solid bar will continue to rotate and forward at the same time, in the role of the roll and the head, the tube billet internal will be gradually formed cavity, that is said capillary. And then it will be sent to the automatic rolling mill to continue rolling. Finally, it will be reeled the wall thickness by reeling mill, sized by sizing mill, to achieve the specifications. It is a more advanced method that using continuous rolling mill to produce hot-rolled seamless steel pipe. Generally process of hot-rolled seamless steel pipe: round bars → heating → piercing → three-roll cross rolling, rolling or extrusion → detached → sizing (or reducing) → cooling → parison tube → straightening → hydrostatic test (or flaw detection) → mark → storage.