The seamless steel pipe is a circular, square, rectangular steel with a hollow section and no seams around it. The seamless steel pipe is formed by perforating a steel ingot or a solid tube blank, and then hot rolled, cold rolled or cold drawn. The seamless steel pipe has a hollow section and is used as a pipe for conveying fluid. Compared with a solid steel such as round steel, the steel pipe has a lighter weight when it has the same bending and torsional strength, and is an economical section steel which is widely used for manufacturing structures. Parts and mechanical parts, such as oil drill pipes, automotive drive shafts, bicycle frames, and steel scaffolding used in construction.
Seamless steel pipe production process: hot rolling, hot expansion, cold drawing, cold rolling, and centrifugal casting seamless steel pipe. Seamless steel pipe specifications: 8-1240 × 1-200 mm. A welded steel pipe is a steel pipe which is welded and formed by a steel strip or a steel plate and deformed into a circular shape or a square shape, and has a joint on the surface. The blank used for welded steel pipes is steel plate or strip steel. According to different welding methods, it can be divided into arc welded pipe, high frequency or low frequency electric resistance welded pipe, gas welded pipe, furnace welded pipe, Bondi pipe and so on.
Electric resistance welding pipe: used in oil drilling and machinery manufacturing. Furnace welded pipe: It can be used as water gas pipe, etc., large diameter straight seam welded pipe is used for high pressure oil and gas transportation; spiral welded pipe is used for oil and gas transportation, pipe pile and pier. According to the shape of the weld, it can be divided into straight seam welded pipe and spiral welded pipe. Longitudinal welded pipe: the production process is simple, the production efficiency is high, the cost is low, and the development is fast. Spiral welded pipe: The strength is generally higher than that of a straight welded pipe. It is possible to produce a welded pipe with a large diameter with a narrow blank, and it is also possible to produce a welded pipe with a different pipe diameter with a blank of the same width. However, compared with the straight pipe of the same length, the weld length is increased by 30 to 100%, and the production speed is low.
Therefore, most of the smaller diameter welded pipes are straight seam welded, and the large diameter welded pipes are mostly spiral welded. According to the purpose, it is divided into general welded pipe, galvanized welded pipe, blown oxygen welded pipe, wire casing, metric welded pipe, idler pipe, deep well pump pipe, automobile pipe, transformer pipe, electric welding thin wall pipe, electric welding special pipe and spiral welded pipe.
Slotted steel pipes and seamless steel pipes are divided according to the processing form. The seamed steel pipes are generally welded, and the seamless steel pipes are cold drawn and hot-rolled.
1.1. Hot-rolled seamless pipes are generally produced on automatic rolling mills. The solid tube blank is inspected and the surface defects are removed, cut into the required length, centered on the end face of the perforated end of the tube blank, then sent to a heating furnace for heating and perforated on the punching machine.
At the same time, the perforation is continuously rotated and advanced. Under the action of the roll and the head, a cavity is gradually formed inside the tube blank, which is called a capillary tube. It is sent to the automatic pipe mill for further rolling. Finally, the whole machine is uniform in wall thickness, and the sizing machine is sizing to meet the specification. The production of hot-rolled seamless steel tubes by continuous rolling mills is a more advanced method.
1.2. If you want to obtain seamless pipes of smaller size and better quality, you must use cold rolling, cold drawing or a combination of the two. Cold rolling is usually carried out on a two-roll mill in which the steel pipe is rolled in an annular hole formed by a variable-section circular hole groove and a stationary tapered head. Cold drawing is usually carried out on a single-chain or double-chain cold drawing machine of 0.5 to 100T.
1.3. Extrusion method The tube blank to be heated is placed in a closed extrusion cylinder, and the perforated rod moves together with the extrusion rod to extrude the extrusion from the smaller mold hole. This method can produce steel pipes with smaller diameters. Seamless steel pipe use: mainly used as a pipe or structural part for conveying fluid.
Sewed steel pipes are mainly welded by steel plates (steel strips), so they are cheap and widely used. Seamless steel pipes are mostly used in the machinery industry, and seamed steel pipes are mostly used in the construction industry. However, seamless pipes are used for pressure pipes.