Production process of seamless steel pipe
The production process of the general seamless steel pipe can be divided into two kinds of cold drawing and hot rolling. The production process of cold rolled seamless steel tube is generally more complicated than hot rolling. The tube billet must be three rolls in continuous rolling. After the extrusion, the diameter of the pipe must be tested. If the surface has no response to the crack, the pipe must be cut through the cutting machine and the cutting growth is about one meter. The blank. Then enter the annealing process, annealing to use acid liquid for acid washing, acid washing should pay attention to the surface is a large number of bubbles, if there is a large number of bubbles, the quality of the steel pipe can not reach the standard of response. The appearance of the cold rolled seamless steel tube is shorter than the hot rolled seamless steel pipe, the wall thickness of the cold rolled seamless steel tube is generally smaller than the hot rolled seamless steel pipe, but the surface looks brighter than the thick wall seamless steel tube, the surface is not too rough, and the diameter is not too much burr. The delivery status of hot-rolled seamless steel tubes is generally delivered after hot rolling. After quality inspection, the hot rolled seamless steel tube must be carefully selected by the staff after quality inspection. After the quality inspection, the surface oil should be applied to the surface. Then the cold drawing experiment is followed by many experiments. After hot rolling, the experiment of perforation should be carried out. If the perforated expansion is too large, straightening and correction will be needed. After straightening, the transmission device is then transmitted to the flaw detecting machine to carry out the flaw detection experiment. Finally, the label is attached and the specification is arranged to be placed in the warehouse.
Hot rolling (extruded seamless steel pipe)
Pipe billet, heating, perforation, three roll skew rolling, continuous rolling or extrusion, depipe, diameter (or reducing diameter), cooling, straightening, water pressure test (or flaw detection), mark to warehouse seamless steel pipe is made of steel ingot or solid pipe through perforation, and then hot rolled, cold rolled or cold dialed. The specification of seamless steel pipe is expressed by outer diameter * millimeter of wall thickness. Two types of seamless steel tubes are divided into hot-rolled and cold rolled (seamless) steel tubes. The hot rolled seamless steel tubes are divided into steel tubes, low and medium pressure boiler tubes, high pressure boiler tubes, alloy tubes, stainless steel pipes, oil cracking pipes, geological pipes and other steel pipes. The cold rolled (dialing) seamless steel tubes are divided into ordinary steel tubes, low medium pressure boiler tubes, high pressure boiler tubes, alloy steel tubes, stainless steel pipes, oil cracking tubes and other steel pipes, including carbon thin-walled steel tubes, alloy thin-walled steel tubes, stainless steel tubes and special-shaped steel tubes. The outer diameter of hot rolled seamless tube is generally greater than 32mm, the wall thickness is 2.5-200mm, the cold rolled seamless steel pipe can reach 6mm, the wall thickness can be 0.25mm, the outer diameter of the thin-walled tube can be less than 0.25mm, and the cold rolling mill has a higher precision than the hot rolling.
The seamless steel tubes are made of hot rolled or cold rolled steel with low alloy structural steels such as 10, 20, 30, 35, 45 and other high quality carbon steel 16Mn, 5MnV, or 40Cr, 30CrMnSi, 45Mn2, 40MnB, etc. Seamless pipes made of low carbon steel such as 10 and 20 are mainly used for fluid conveying pipes. 45, 40Cr and other medium carbon steel seamless pipe for manufacturing mechanical parts, such as cars and tractors of the force parts. Generally, the strength and flattening test of seamless steel pipe should be ensured. Hot rolled steel pipes are delivered in hot rolling or heat treatment; cold rolling is delivered in heat and heat treatment.
Hot rolling, as the name suggests, the temperature of the rolled piece is high, so the deformation resistance is small, and large deformation can be achieved. Taking the rolling of steel plate as an example, the thickness of continuous casting billets is about 230mm, and after rough rolling and finishing rolling, the final thickness is 1~20mm. At the same time, because of the small width to thickness ratio of steel plate, the requirement of dimensional accuracy is relatively low, and the shape problem is not easy to appear. For the organization that is required, it is generally realized through controlled rolling and controlled cooling, that is to control the rolling temperature and finishing rolling temperature of the finishing rolling, the round tube billet, the heating, the piercing, the punch, the annealing, the acid washing, the oil (copper plating), the multi pass cold drawing (cold rolling), the billet tube, the heat treatment, the straightening, the water pressure test (inspection), the marking, and the warehouse.
Two. The production process of spiral steel pipe
Spiral steel pipe is made of rolled steel strip as raw material, often warm extruded and welded by automatic double wire submerged arc welding technology.
(1) raw materials are steel coil, wire and flux. Strict physical and chemical tests should be carried out before the input.
(2) butt welding of steel head and tail, single wire or double wire submerged arc welding, and automatic submerged arc welding repair after rolling into steel pipe.
(3) before forming, strip is leveled, trimming, planing, surface cleaning, transportation and bending.
(4) the electric contact pressure gauge is used to control the pressure of the oil cylinder on both sides of the conveyor so as to ensure the smooth conveying of the strip.
(5) use external or internal control roll forming.
(6) the weld gap control device is adopted to ensure that the weld gap meets the welding requirements, and the pipe diameter, misalignment and weld clearance are strictly controlled.
(7) internal and external welding uses Lincoln Electric Welder to carry out single wire or double wire submerged arc welding so as to achieve stable welding quality.
(8) the welded seam after welding is checked by on-line continuous ultrasonic automatic injury detector, which ensures the non-destructive detection coverage of 100% spiral weld. If defective, automatic alarm and spray marking, production workers adjust the process parameters at any time, eliminate defects in time.
(9) use air plasma cutting machine to cut the steel pipe into single root.
(10) after cutting into single steel pipe, each steel pipe must be strictly first inspected, to check the mechanical properties of the weld, the chemical composition, the condition of dissolution, the quality of the surface of the steel tube and the inspection of nondestructive testing, so as to ensure that the production of the pipe is qualified.
(11) There are continuous sonic detection marks on the weld, through manual ultrasonic and X ray review, such as defects, after repair, again after nondestructive testing, until the defect has been confirmed.
(12) all the butt welds of the strip and the joint of the butt joint with the spiral weld are all examined by X ray television or film.
(13) each steel pipe is hydrostatic test and the pressure is radial sealed. The test pressure and time are strictly controlled by the microcomputer inspection device for steel pipe water pressure. The test parameters are automatically printed and recorded.
(14) machining the end of the pipe, making the verticality of the end face, the slope angle and the blunt edge accurately controlled.
Three. Production process of welded pipe
The longitudinal welded pipe has the advantages of simple production process, high production efficiency, low cost and rapid development. The strength of a spiral welded pipe is generally higher than that of a straight welded pipe. It can produce a larger pipe with a narrow blank, and the same width of the blank can be used to produce a pipe with different diameters. However, compared with the straight seam pipe of the same length, the weld length is increased by 30~100% and the production speed is low.
Large diameter or thicker welded pipes are usually made directly from steel billets, while small welded pipe can only be welded directly through steel strips. Then after a simple polishing, the wire can be pulled. Therefore, small diameter welded pipes are mostly welded longitudinally, while large diameter welded pipes are mostly spiral welded.
Four. The production process of bearing steel
50 tons UHP electric furnace smelting, 60 tons LF furnace refining, 60 ton VD furnace vacuum treatment, alloy steel rectangular billet continuous casting (260mm x 300mm, 180mm x 220mm), slow cooling or hot delivery, rolling material, finishing and inspection into the warehouse.
Five. The production process of galvanized pipe
Inspection of black parts, hanging material, degreasing, rinsing, pickling, cleaning, washing, dipping and helping plating agent, hot air drying, hot dip galvanizing, internal and external, cooling, passivation and rinsing, unloading, discharging, testing, dressing, marking, packing, transportation and transportation
Six. Forming process of straight welded pipe
Main production process of large diameter longitudinal welded pipe: large diameter longitudinal welded pipe)
1., plate inspection: after the steel plate used for manufacturing large diameter submerged arc welded straight steel pipe has entered the production line, ultrasonic inspection of the whole board is carried out first.
2. milling edge: through the edge milling machine, double side milling on the edge of the steel plate two, so as to achieve the required width, edge parallelism and groove shape.
3. preflanging: pre bending machine is used to pre bend the edge of the plate, so that the edges of the board meet the required curvature.
4. molding: in the JCO molding machine, the first half of the plate after the pre bending is stepped into the form of “J”, then the other half of the steel plate is bending to form a “C” shape, and finally the “O” shape of the opening is formed.
5. pre welding: make the formed longitudinal welded steel pipe seams and use gas shielded welding (MAG) for continuous welding.
6. internal welding: using longitudinal multi wire submerged arc welding (up to four wire) to weld the inner side of the straight seam pipe.
7. external welding: longitudinal multi wire submerged arc welding is carried out on the outside of the longitudinal submerged arc welded pipe.
8. ultrasonic test I. inspection of the inside and outside weld of the longitudinal welded pipe and the base metal on both sides of the weld seam 100%.
9. X ray examination I: 100% X – ray industrial TV inspection of internal and external welds. Image processing system is adopted to ensure the sensitivity of flaw detection.
10. expanding diameter: expanding the length of submerged arc welded straight steel pipe to improve the dimensional accuracy of the steel pipe and improving the distribution state of the internal stress of the steel pipe.
11. water pressure test: on the water pressure test machine, the steel pipe after the expansion is tested by the root by root to ensure the test pressure of the steel pipe to meet the standard requirements. The machine has the function of automatic recording and storage.
12. chamfering: the steel pipe after inspection is processed to meet the required pipe end groove dimensions.
13. ultrasonic testing II: ultrasonic inspection is carried out again and again to check the possible defects of longitudinal welded pipe after expanding and water pressure.
14. X ray examination II: X – ray industrial TV inspection and pipe end fillet shooting for steel pipe after expanding and hydraulic test;
15. tube end magnetic particle inspection: carry out this inspection to find pipe end defects;
16. anticorrosion and coating: qualified steel pipe shall be anticorrosive and coated according to user requirements.
Source: China Steel Pipes Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)