Views: 3 Author: Site Editor Publish Time: 2023-06-26 Origin: Site
There are many uses for modern seamless steel pipe production. Seamless steel pipe (Seamless Steel Tube) is a long strip of steel with a hollow section and no seams around it. The steel pipe has a hollow section and is widely used as a pipeline for transporting fluids, such as pipelines for transporting oil, natural gas, gas, water, and certain solid materials. Compared with solid steel such as round steel, the steel pipe is lighter in weight when the bending and torsional strength is the same. It is an economical cross-section steel and is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes, automobile transmission shafts, and bicycles. Frames and steel scaffolding used in building construction, etc. The use of steel pipes to manufacture ring parts can improve the utilization rate of materials, simplify the manufacturing process, save materials, and process man-hours, such as rolling bearing rings, jack sets, etc., which have been widely used in steel pipes. Steel pipe is also an indispensable material for various conventional weapons, and barrels, barrels, etc. must be made of steel pipes. Steel pipes can be divided into round pipes and special-shaped pipes according to the shape of the cross-sectional area. Due to the condition that the circumference is equal, the area of the circle is the largest, and more fluid can be transported with a circular tube. In addition, when the ring section is subjected to internal or external radial pressure, the force is relatively uniform, so most steel pipes are round pipes.
However, round pipes also have certain limitations. For example, under the condition of plane bending, round pipes are not as strong as square and rectangular pipes in bending strength. Some agricultural machinery skeletons, steel and wood furniture, etc. often use square and rectangular pipes. According to different purposes, special-shaped steel pipes with other cross-sectional shapes are also required.
At present, there are more than 5,100 production plants under more than 1,850 companies in more than 110 countries producing steel pipes in the world, among which there are more than 260 factories under more than 170 companies in 44 countries that produce oil pipes. In 2000, the national apparent consumption of seamless steel pipes was 4.18 million tons, of which the domestic supply was 3.821 million tons, accounting for 91.4% of the total domestic demand. Imports were 359,000 tons, accounting for 8.59% of total domestic demand. In the same year, the consumption of oil pipes was about 910,000 tons. Imports were about 252,000 tons. Imported pipes account for about 70% of total domestic consumption, of which imported pipes account for 27.69% of total domestic consumption, and oil pipe imports account for about 70% of total seamless steel pipe imports. Oil pipes imported from Japan accounted for more than half of the total imports. In 2000, China's largest oil casing production base produced 522,000 tons of steel pipes, including 364,100 tons of oil casings. Casing accounts for more than half of the country's oil production. It occupies the first place in China's bushing market in terms of output and sales volume.
Judging from the international and domestic markets, the existing production capacity of seamless steel pipes (including special oil pipes) has exceeded the demand. Therefore, the future focus should be on giving full play to the capabilities of existing units and developing products such as oil pipes, high-pressure boiler pipes, and gas cylinder pipes with high strength, high resistance to damage, and high corrosion resistance. It is also the content of the country's optimization of product structure for the current steel market in my country. This is also the key to increasing product competitiveness at home and abroad and expanding market share. That is to say, improving the market competitiveness of domestic steel pipe enterprises is the long-term task and the key to the successful development of domestic enterprises after joining WTO.
The manufacturing process of seamless steel pipe
1. Hot rolling (extruded seamless steel pipe): round tube billet → heating → piercing → three-roll cross rolling, continuous rolling or extrusion → stripping → sizing (or reducing) → cooling → straightening → hydraulic test (or flaw detection) → marking → warehousing
The raw material for rolling seamless pipe is a round tube billet, and the round tube embryo should be cut by a cutting machine to grow billets with a length of about 1 meter, and transported to the furnace by conveyor belt. The billet is fed into the furnace to heat, the temperature is about 1200 degrees Celsius. The fuel is hydrogen or acetylene. The temperature control in the furnace is a key issue. After the round tube is out of the furnace, it must be pierced through a pressure piercer. Generally, the more common piercer is the cone roll piercer. This kind of piercer has high production efficiency, good product quality, large perforation diameter expansion, and can wear a variety of steel types. After piercing, the round tube billet is successively cross-rolled, continuously rolled, or extruded by three rolls. After extrusion, the tube should be taken off for sizing. Sizing by high-speed rotary cone drill holes into the billet to form a tube. The inner diameter of the steel pipe is determined by the length of the outer diameter of the drill bit of the sizing machine. After the steel pipe is sized, it enters the cooling tower and is cooled by spraying water. After the steel pipe is cooled, it will be straightened. After straightening, the steel pipe is sent to the metal flaw detector (or hydraulic test) by the conveyor belt for internal flaw detection. If there are cracks, bubbles, and other problems inside the steel pipe, they will be detected. After the quality inspection of steel pipes, strict manual selection is required. After the quality inspection of the steel pipe, paint the serial number, specification, production batch number, etc. with paint. And hoisted into the warehouse by crane.
2. Cold drawn (rolled) seamless steel pipe: round tube blank→heating→piercing→heading→annealing→pickling→oiling (copper plating)→multi-pass cold drawing (cold rolling)→blank tube→heat treatment→straightening → Hydrostatic test (flaw detection) → Marking → Storage.
The rolling method of cold-drawn (rolled) seamless steel pipes is more complicated than hot-rolling (extruded seamless steel pipes). The first three steps of their production process are the same. The difference starts from the fourth step. After the round tube is empty, it needs to be heated and annealed. After annealing, use a special acidic liquid for pickling. After pickling, apply oil. Then it is followed by a multi-pass cold drawing (cold rolling) and special heat treatment. After heat treatment, it will be straightened. After straightening, the steel pipe is sent to the metal flaw detector (or hydraulic test) by the conveyor belt for internal flaw detection. If there are cracks, bubbles, and other problems inside the steel pipe, they will be detected. After the quality inspection of steel pipes, strict manual selection is required. After the quality inspection of the steel pipe, paint the serial number, specification, production batch number, etc. with paint. And hoisted into the warehouse by crane.
Seamless pipe production classification - hot-rolled pipe, cold-rolled pipe, cold-drawn pipe, extruded pipe, pipe jacking
1. Structural seamless steel pipes (GB/T8162-1999) are seamless steel pipes used for general structures and mechanical structures.
2. Seamless steel pipe for fluid transportation (GB/T8163-1999) is a general seamless steel pipe used to convey fluids such as water, oil, and gas.
3. Seamless steel pipes for low and medium pressure boilers (GB3087-1999) are used to manufacture superheated steam pipes, boiling water pipes for low and medium pressure boilers of various structures, superheated steam pipes, large smoke pipes, small smoke pipes and arch bricks for locomotive boilers High-quality carbon structural steel hot-rolled and cold-drawn (rolled) seamless steel pipes for pipes.
4. Seamless steel tubes for high-pressure boilers (GB5310-1995) are high-quality carbon steel, alloy steel, and stainless heat-resistant seamless steel tubes for the heating surface of water tube boilers for high pressure and above.
5. High-pressure seamless steel pipe for fertilizer equipment (GB6479-2000) is a high-quality carbon structural steel and alloy steel seamless steel pipe suitable for chemical equipment and pipelines with a working temperature of -40~400°C and a working pressure of 10~30Ma.
6. Seamless steel pipes for petroleum cracking (GB9948-88) are seamless steel pipes suitable for furnace tubes, heat exchangers, and pipes in petroleum refineries.
7. Steel pipes for geological drilling (YB235-70) are steel pipes used for core drilling by geological departments and can be divided into drill pipes, drill collars, core pipes, casing pipes, and sedimentation pipes according to their uses.
8. Seamless steel pipes for diamond core drilling (GB3423-82) are seamless steel pipes used for drill pipes, core rods, and casings for diamond core drilling.
9. Oil drilling pipe (YB528-65) is a seamless steel pipe that is thickened inside or outside at both ends of oil drilling. There are two types of steel pipes: threaded and non-threaded. The threaded pipes are connected with joints, and the non-threaded pipes are connected with tool joints by butt welding.
10. Carbon steel seamless steel pipes for ships (GB5213-85) are carbon steel seamless steel pipes for the manufacture of Class I pressure-resistant piping systems, Class II pressure-resistant piping systems, boilers, and superheaters. The working temperature of the carbon steel seamless steel pipe wall does not exceed 450°C, and the working temperature of the alloy steel seamless steel pipe wall exceeds 450°C.
11. The seamless steel pipe for automobile half-shaft casing (GB3088-82) is a hot-rolled seamless steel pipe of high-quality carbon structural steel and alloy structural steel for the manufacture of automobile half-shaft casing and drive axle housing shaft pipe.
12. High-pressure oil pipes for diesel engines (GB3093-86) are cold-drawn seamless steel pipes for manufacturing high-pressure pipes for diesel engine injection systems.
13. Precision inner diameter seamless steel tubes for hydraulic and pneumatic cylinders (GB8713-88) are cold-drawn or cold-rolled precision seamless steel tubes with precise inner diameters for the manufacture of hydraulic and pneumatic cylinders.
14. Cold-drawn or cold-rolled precision seamless steel pipe (GB3639-83) is a cold-drawn or cold-rolled precision seamless steel pipe with high dimensional accuracy and good surface finish for mechanical structures and hydraulic equipment. The use of precision seamless steel pipes to manufacture mechanical structures or hydraulic equipment can greatly save machining hours, improve material utilization, and help improve product quality.
15. Structural stainless steel seamless steel pipe (GB/T14975-1994) is a hot-rolled ( extrusion, expansion) and cold-drawn (rolled) seamless steel tube.
16. Stainless steel seamless steel pipes for fluid transportation (GB/T14976-1994) are hot-rolled (extruded, expanded) and cold-drawn (rolled) seamless steel pipes made of stainless steel for fluid transportation.
17. Special-shaped seamless steel pipe is a general term for seamless steel pipes with cross-sectional shapes other than round pipes. According to the shape and size of the cross-section of the steel pipe, it can be divided into special-shaped seamless steel pipes with equal wall thickness (code-named D), special-shaped seamless steel pipes with different wall thickness (code-named BD), and special-shaped seamless steel pipes with the variable diameter (code-named BJ). Special-shaped seamless steel pipes are widely used in various structural parts, tools, and mechanical parts. Compared with round pipes, special-shaped pipes generally have a larger moment of inertia and section modulus, and have greater bending and torsion resistance, which can greatly reduce the structural weight and save steel.
Generally, seamless steel pipes are made of high-quality carbon structural steels such as 10, 20, 30, 35, 45, 16Mn, 5MnV, and other low-alloy structural steels, or 40Cr, 30CrMnSi, 45Mn2, 40MnB and other combined steels that are hot-rolled or cold-rolled. 10, 20, and other low-carbon steel seamless pipes are mainly used for fluid-conveying 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 pipes are used to ensure strength and flattening tests. Hot-rolled steel pipes are delivered in a hot-rolled or heat-treated state; cold-rolled steel pipes are delivered in a heat-treated state. Seamless steel pipes for low and medium-pressure boilers: used to manufacture various low and medium-pressure boilers, superheated steam pipes, boiling water pipes, water wall pipes, and superheated steam pipes for locomotive boilers, large smoke pipes, small smoke pipes, and arch brick pipes, etc.
Hot-rolled or cold-rolled (dial) seamless steel pipes are made of high-quality carbon structural steel. It is mainly made of No. 10 and No. 20 steel. In addition to ensuring the chemical composition and mechanical properties, hydrostatic tests, crimping, flaring, and flattening tests are required. Hot rolling is delivered in a hot-rolled state, and cold rolling (dial) is delivered in a heat-treated state.