① Main production process of hot rolled Seamless Steel Pipe (△ main inspection process):
Preparation and inspection of pipe blank △ → heating of pipe blank → perforation → pipe rolling → reheating of Steel Pipe → sizing (reducing) → heat treatment △ → straightening of finished pipe → finishing → inspection △ (nondestructive, physical and chemical, bench inspection) → warehousing
② Main production processes of cold rolled (drawn) seamless steel pipe:
Blank preparation → pickling and lubrication → cold rolling (drawing) → heat treatment → straightening → finishing → inspection
The general production process of seamless steel pipe in China 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 first be subject to three roll continuous rolling, and the sizing test shall be carried out after extrusion. If the surface does not respond to the crack, the round pipe must 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. When pickling, the seamless Steel Pipe Factory shall 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 pipes produced by the seamless steel pipe factory cannot 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 pipes produced by Chinese steel pipe plants is generally hot-rolled and delivered after heat treatment. After quality inspection, the hot-rolled seamless steel pipe shall be strictly selected by the staff by hand. After quality inspection, the surface shall be coated with oil, 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 transferred to the flaw detector by the conveyor for flaw detection test, labeled, arranged and placed in the warehouse.
Round tube blank → heating → perforation → three roll cross rolling, continuous rolling or extrusion → pipe stripping → sizing (or reducing) → cooling → straightening → hydrostatic test (or flaw detection) → marking → warehousing seamless steel pipe is made of steel ingot or solid tube blank through perforation, and then hot rolled, cold rolled or cold drawn. The specification of seamless steel pipe is expressed in mm of outer diameter * wall thickness.
The outer diameter of hot-rolled seamless steel pipe in China 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.
Hot rolling, as the name suggests, the temperature of rolled piece is high, so the deformation resistance is small and large deformation can be realized. Seamless steel pipe plant takes the rolling of steel plate as an example. Generally, the thickness of continuous casting slab is about 230mm, while after rough rolling and finish rolling, the final thickness is 1 ~ 20mm. At the same time, because the width thickness ratio of the steel plate is small and the requirements for dimensional accuracy are relatively low, the shape problem is not easy to occur, and the convexity is mainly controlled.
It is generally realized by controlled rolling and controlled cooling, that is, to control the start rolling temperature and final rolling temperature of finish rolling Round tube blank → heating → perforation → heading → annealing → pickling → oiling (copper plating) → multi pass cold drawing (cold rolling) → blank tube → heat treatment → straightening → hydrostatic test (flaw detection) → marking → warehousing.