How is seamless steel pipe made?

The seamless steel pipe is made of perforated whole round steel, and the steel pipe without weld seam on the surface is called seamless steel pipe.

①The main production process of hot-rolled seamless steel pipe (△main inspection process):
Tube blank preparation and inspection△→tube blank heating→piercing→tube rolling→steel reheating→fixed (reduced) diameter→heat treatment△→finished pipe straightening→finishing→inspection△ (non-destructive, physical and chemical, Taiwan inspection)→warehousing

②The main production process of cold-rolled (drawn) seamless steel pipe:
Billet preparation→pickling lubrication→cold rolling (drawing)→heat treatment→straightening→finishing→inspection

The production process of general seamless steel pipes can be divided into two types: cold-drawing and hot-rolling. The production process of cold-rolled seamless steel pipes is generally more complicated than that of hot rolling. In the sizing test, if the surface does not respond to cracks, the round tube shall be cut by a cutting machine and cut into a billet with a length of about one meter. Then enter the annealing process, annealing should be pickled with acidic liquid, and pay attention to whether there is a lot of blistering on the surface during pickling. In appearance, the cold-rolled seamless steel pipe is shorter than the hot-rolled seamless steel pipe. The wall thickness of the cold-rolled seamless steel pipe is generally smaller than that of the hot-rolled seamless steel pipe, but the surface looks brighter than the thick-walled seamless steel pipe, and the surface is not too much. Much rougher, and the caliber doesn't have too many burrs.

The delivery state of hot-rolled seamless steel pipe is generally that the hot-rolled state is delivered after heat treatment. 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 several cold-drawing experiments. After the hot-rolling treatment, the perforation experiment should be carried out. If the diameter of the perforation is too large, it should be straightened and corrected. After straightening, it will be sent to the flaw detector by the conveyor for flaw detection experiment, and finally labelled and arranged in specifications, and then placed in the warehouse.

Round tube blank→heating→piercing→three-roll skew rolling, continuous rolling or extrusion→tube removal→sizing (or reducing)→cooling→straightening→hydrostatic test (or flaw detection)→marking→storage seamless steel pipe It is made of steel ingots or solid tube blanks through perforation to make capillaries, and then hot-rolled, cold-rolled or cold-drawn. The specification of seamless steel pipe is expressed by outer diameter * wall thickness mm.

The outer diameter of hot-rolled seamless pipes is generally greater than 32mm, and the wall thickness is 2.5-200mm. The outer diameter of cold-rolled seamless pipes can reach 6mm and the wall thickness can reach 0.25mm. The outer diameter of thin-walled pipes can reach 5mm. Rolling has higher dimensional accuracy than hot rolling.

Generally, seamless steel pipes are made of 10, 20, 30, 35, 45 and other high-quality carbon steel 16Mn, 5MnV and other low-alloy structural steel or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other combined steel hot-rolled or cold-rolled. Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid transportation pipelines. 45, 40Cr and other medium carbon steel seamless pipes are used to manufacture mechanical parts, such as the stressed parts of automobiles and tractors. Generally, seamless steel pipes are used to ensure strength and flattening tests. Hot-rolled steel pipes are delivered in hot-rolled or heat-treated state; cold-rolled steel pipes are delivered in heat-treated state.

Hot rolling, as the name implies, has a high temperature of the rolled piece, 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-to-thickness ratio of the steel plate, the dimensional accuracy requirements are relatively low, and the plate shape problem is not easy to occur, and the main control is to control the crown. For those with organizational requirements, it is generally realized by controlled rolling and controlled cooling, that is, controlling the opening temperature and final rolling temperature of finishing rolling. Round tube billet → heating → perforation → heading → annealing → pickling → oiling (copper plating) → Multi-pass cold drawing (cold rolling) → billet tube → heat treatment → straightening → hydraulic test (flaw detection) → marking → storage.