Seamless steel pipes

Seamless steel pipes

Seamless steel pipes are made of a whole piece of metal, and there are no seams on the surface. They are called seamless steel pipes. According to the production method, seamless pipes are divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, jacking pipes, etc. According to the cross-sectional shape, seamless steel pipes are divided into round and special-shaped pipes. Special-shaped pipes have square, oval, triangle, hexagon, melon seed, star, winged pipes and many other complex shapes. The maximum diameter is 650mm and the minimum diameter is 0.3mm. According to different uses, there are thick-walled pipes and thin-walled pipes. Seamless steel pipes are mainly used as petroleum geological drilling pipes, cracking pipes for petrochemicals, boiler pipes, bearing pipes, and high-precision structural steel pipes for automobiles, tractors, and aviation. A steel pipe with no seams along the periphery of its cross section. According to different production methods, it is divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, jacking pipes, etc., all with their own process regulations. The materials include ordinary and high-quality carbon structural steel (Q215-A~Q275-A and 10~50 steel), low alloy steel (09MnV, 16Mn, etc.), alloy steel, stainless acid-resistant steel, etc. According to the use, it is divided into general use (used for water, gas pipelines and structural parts, mechanical parts) and special use (used for boilers, geological exploration, bearings, acid resistance, etc.). ① Main production process of hot-rolled seamless steel pipe (△ Main inspection process):
Pipe blank preparation and inspection△→Pipe blank heating→Pipe perforation→Pipe rolling→Steel pipe reheating→Size (reduction)→Heat treatment△→Finished pipe straightening→Finishing→Inspection△(Non-destructive, physical and chemical, bench inspection)→Warehousing
② Main production process of cold-rolled (drawn) seamless steel pipe: Seamless steel pipe_Seamless steel pipe manufacturer_Seamless steel pipe price
Blank preparation→Acid pickling and lubrication→Cold rolling (drawing)→Heat treatment→Straightening→Finishing→Inspection
General seamless steel pipe production process can be divided into cold drawing and hot rolling. The production process of cold-rolled seamless steel pipe is generally more complicated than hot rolling. The pipe blank must first be rolled with three rollers, and then the sizing test must be carried out after extrusion. If there is no response crack on the surface, the round pipe must be cut by a cutting machine and cut into a billet of about one meter in length. Then enter the annealing process. Annealing must be pickled with acidic liquid. When pickling, pay attention to whether there is a large amount of bubbles on the surface. If there is a large amount of bubbles, it means that the quality of the steel pipe does not meet the corresponding standards. In appearance, cold-rolled seamless steel pipes are shorter than hot-rolled seamless steel pipes. The wall thickness of cold-rolled seamless steel pipes is generally smaller than that of hot-rolled seamless steel pipes, but the surface looks brighter than thick-walled seamless steel pipes, and the surface is not too rough, and the diameter does not have too many burrs.
The delivery state of hot-rolled seamless steel pipes is generally hot-rolled and heat-treated before delivery. After quality inspection, hot-rolled seamless steel pipes must be strictly hand-selected by staff, and the surface must be oiled after quality inspection, followed by multiple cold drawing tests. After hot rolling treatment, perforation tests must be carried out. If the perforation diameter is too large, straightening and correction must be carried out. After straightening, the conveyor device will be conveyed to the flaw detector for flaw detection, and finally labeled, arranged in specifications, and placed in the warehouse.
Round tube billet → heating → perforation → three-roller oblique rolling, continuous rolling or extrusion → tube removal → sizing (or reducing diameter) → cooling → straightening → hydraulic pressure test (or flaw detection) → marking → storage Seamless steel pipe is made of steel ingot or solid tube billet by perforation into rough tube, and then made by hot rolling, cold rolling or cold drawing. The specifications of seamless steel pipe are expressed in millimeters of outer diameter * wall thickness.
The outer diameter of hot-rolled seamless pipe is generally greater than 32mm, and the wall thickness is 2.5-200mm. The outer diameter of cold-rolled seamless steel pipe can reach 6mm, the wall thickness can reach 0.25mm, and the outer diameter of thin-walled pipe can reach 5mm and the wall thickness is less than 0.25mm. Cold rolling has higher dimensional accuracy than hot rolling.
Generally, seamless steel pipes are made of 10, 20, 30, 35, 45 high-quality carbon steel, 16Mn, 5MnV and other low-alloy structural steel or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other alloy steels. Hot rolling or cold rolling. Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid delivery pipelines. Seamless pipes made of medium carbon steel such as 45 and 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 states; cold-rolled steel pipes are delivered in heat-treated states.
Hot rolling, as the name implies, has a high temperature for the rolled piece, so the deformation resistance is small and a large deformation amount can be achieved. Taking the rolling of steel plates as an example, the thickness of the continuous casting billet is generally about 230mm, and after rough rolling and finishing rolling, the final thickness is 1~20mm. At the same time, due to the small width-to-thickness ratio of the steel plate, the dimensional accuracy requirements are relatively low, and it is not easy to have plate shape problems, mainly to control the convexity. For those with organizational requirements, it is generally achieved through controlled rolling and controlled cooling, that is, controlling the start rolling temperature and the final rolling temperature of the finishing rolling. Round tube billet → heating → piercing → heading → annealing → pickling → oiling (copper plating) → multiple passes of cold drawing (cold rolling) → billet tube → heat treatment → straightening → water pressure test (flaw detection) → marking → storage.