seamless steel pipe
Seamless steel pipe is perforated by the whole round steel, and the steel pipe without weld on the surface is 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, pipe jacking, etc. According to the section shape, seamless steel pipes are divided into circular and special-shaped pipes. Special-shaped pipes have a variety of complex shapes such as square, oval, triangular, hexagonal, melon seed, star and winged pipes. The maximum diameter is 900mm and the minimum diameter is 4mm.
Seamless steel pipe production process
The production process of seamless steel pipe can be divided into cold drawing and hot rolling. The production process of cold-rolled seamless steel pipe is generally more complex than hot rolling. The pipe blank must be subjected to three roll continuous rolling first, and the sizing test shall be carried out after extrusion. If the surface does not respond to the crack, the round pipe shall be cut by a cutter to cut the blank with a growth of about one meter. Then enter the annealing process. The annealing shall be pickled with acid liquid. During pickling, pay attention to whether there are a large number of bubbles on the surface. If there are a large number of bubbles, it indicates that the quality of steel pipe can not meet the corresponding standards. The appearance of cold-rolled seamless steel pipe is shorter than that of hot-rolled seamless steel pipe. The wall thickness of cold-rolled seamless steel pipe is generally smaller than that of hot-rolled seamless steel pipe, but the surface looks brighter than that of thick wall seamless steel pipe. The surface is not too rough and the diameter is not too many burrs.
The delivery status of hot-rolled seamless steel pipe is generally hot-rolled and delivered after heat treatment. After quality inspection, the hot-rolled seamless steel pipe shall be strictly manually selected by the staff. After quality inspection, the surface shall be oiled, followed by many cold drawing experiments. After hot rolling, the perforation experiment shall be carried out. If the perforation expansion is too large, it shall be straightened and corrected. After straightening, it is transmitted to the flaw detector by the conveyor for flaw detection test. Finally, it is labeled and placed in the warehouse after specification arrangement.
Seamless steel pipe grade
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 be up to 6mm, the wall thickness can be up to 0.25mm, the outer diameter of thin-walled pipe can be up to 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 high-quality carbon bonded steels such as 10, 20, 30, 35 and 45, low-alloy structural steels such as 16Mn and 5mnv, or bonded steels such as 40Cr, 30CrMnSi, 45Mn2 and 40MnB. 10. Seamless pipes made of low carbon steel such as 20 are mainly used for fluid transmission pipelines. Seamless pipes made of medium carbon steel such as 45 and 40Cr are used to manufacture mechanical parts, such as stressed parts of automobiles and tractors. Generally, the strength and flattening test of seamless steel pipe shall be ensured. Hot rolled steel pipes shall be delivered in hot rolling state or heat treatment state; Cold rolling is delivered in heat treated condition.
Seamless steel pipe use
High pressure boiler, oil and gas pipeline, ship, liquid transportation, mechanical engineering and structure, low and medium pressure boiler, low temperature pipeline