The general seamless steel pipe production process can be divided into two types: cold drawing and hot rolling. The production process of cold rolled seamless steel pipe is generally more complicated than hot rolling. The tube billet must first be subjected to three-roll continuous rolling, and after extrusion In the sizing test, if the surface does not respond to cracks, the round tube will be cut by a cutting machine and cut into a blank with a length of about one meter. Then enter the annealing process. Annealing should use acidic liquid for pickling. When pickling, pay attention to whether there is a large amount of foaming on the surface. If there is a large amount of foaming, it means that the quality of the steel pipe does not meet the corresponding standards. The appearance of cold-rolled seamless steel tubes is shorter than that of hot-rolled seamless steel tubes. The wall thickness of cold-rolled seamless steel tubes is generally smaller than that of hot-rolled seamless steel tubes, but the surface looks brighter than thick-walled seamless steel tubes. It ’s rough and does n’t have too many burrs.
The delivery status of the hot-rolled seamless steel pipe is generally the hot-rolled state after heat treatment for delivery. After the quality inspection, the hot-rolled seamless steel pipe must be strictly hand-selected by the staff. After the quality inspection, the surface should be oiled, followed by multiple cold-drawing experiments, and the piercing experiment after the hot-rolling treatment If the diameter of the perforation is too large, straightening and correction should be carried out. After straightening, it is transferred to the flaw detection machine by the conveyor to carry out the flaw detection experiment. Finally, the label is attached, the specifications are arranged, and then placed in the warehouse.
Hot rolled
Round tube billet → heating → perforation → three-roller cross-rolling, continuous rolling or extrusion → tube removal → sizing (or reduced diameter) → cooling → straightening → hydraulic test (or flaw detection) → marking → seamless steel pipe in storage It is made of steel ingots or solid tube blanks by perforation to make capillaries, and then made by hot rolling, cold rolling or cold dialing. The specification of seamless steel pipe is expressed by the outer diameter * wall thickness in millimeters. Seamless steel tubes are divided into hot-rolled and cold-rolled (dial) seamless steel tubes. Hot-rolled seamless steel pipes are divided into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, geological steel pipes and other steel pipes. Cold-rolled (dial) seamless steel pipes include general steel pipes, low and medium pressure boiler steel pipes, high-pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, and other steel pipes, but also include carbon thin-walled steel pipes, alloy thin-walled steel pipes, Stainless thin-walled steel pipe and special-shaped steel pipe. The outer diameter of hot-rolled seamless pipe is generally greater than 32mm, 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, the wall thickness is less than 0.25mm Rolling has higher dimensional accuracy than hot rolling.
Generally, seamless steel tubes are made of high-alloy carbon steels such as 10, 20, 30, 35, 45 and other low-alloy structural steels such as 16Mn and 5MnV or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other combined steels by hot or cold rolling. Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid transportation pipelines. Seamless tubes 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, seamless steel tubes are used to ensure the strength and flattening test. Hot-rolled steel pipes are delivered in hot-rolled or heat-treated state; cold-rolled steel pipes are delivered in hot-treated state.
Hot rolling, as the name implies, the temperature of the rolled product is high, so the deformation resistance is small, and a large amount of deformation can be achieved. Taking the rolling of steel plates as an example, the thickness of the continuous casting slab 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-thickness ratio of the steel plate, the dimensional accuracy requirements are relatively low, and it is not easy The shape problem is mainly controlled by the convexity. For the requirements of the organization, it is generally achieved by controlled rolling and controlled cooling, that is, the opening and finishing temperatures of the finishing rolling are controlled. Round tube billet → heating → perforation → heading → annealing → pickling → oiling (copper plating) → multi-pass cold drawing (cold rolling) → billet → heat treatment → straightening → hydraulic test (flaw detection) → marking → entry Library process
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