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Advantages of thick-wall seamless tube cold extrusion technology are as follows:
1. Extrusion parts accurate size and smooth surface: At present, China's development of cold extrusion general dimensional accuracy of up to 8 to 9, if the ideal lubrication, precision second only to the fine polished surface. Therefore, the parts produced by cold extrusion generally do not need to be processed, only a small amount of finishing (grinding).
2. To save raw materials: cold extrusion material utilization can usually reach more than 80%. Such as the liberation of the car piston cutting material utilization rate of 43.3%, while the use of cold extrusion material utilization increased to 92%; Another example of universal joint bearing sleeve to cold extrusion, the material utilization from the past 27.8% to 64%. It can be seen that the use of cold extrusion machinery parts production, you can save a lot of steel and nonferrous metal materials.
3. High productivity: the efficiency of cold extrusion production of mechanical parts is very high, especially the production of large quantities of parts, with cold extrusion method to increase than the cutting several times, several times, or even hundreds of times. For example, the automotive piston pin with cold extrusion method than the use of cutting manufacturing increased by 3.2 times, and now with cold extrusion piston pin automaton, to further improve productivity. The productivity of a cold extrusion robot is equivalent to the productivity of 100 general lathes or 10 4-axis automatic lathes.
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Hot-rolled precision tube continuous casting round tube blank or slab as raw material, the stepping heating furnace heating, high-pressure water after descaling into the roughing mill, roughing material through the first, tail, and then into the finishing mill. The implementation of computer-controlled rolling, after finishing rolling through the laminar flow coiling and coiling, a straight hair volume. Straight hair volume head and tail tend to tongue and fish tail, thickness and width is poor, the edge often exist in the waves, flap, tower and other defects. The heavy weight, coil diameter of 760mm. The straight hair through the head, tail, trimming and multi-pass straightening, leveling and other finishing lines, and then re-board or re-roll, that is: hot-rolled steel, cut with other products. If the hot-rolled finishing roll after pickling to remove the oxide coating and oiled immediately after the heat roll pickling coil. Stainless steel pipe connections are diverse, the common type of pipe fittings are compression, compression, live, push, threaded, socket welding, live flange connection, welding and welding and the traditional connection phase A derivative of a series of connections.
These connections, according to their different principles, its scope of application is also different, but most are easy to install, solid and reliable. Connection ring or gasket material used, most of the selection of the national standard silicone rubber, nitrile rubber and EPDM, eliminating the user's worries.
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Pipeline is used to transport oil, natural gas and other large-diameter welded steel pipe with hot-rolled coil or heavy plate. Pipeline steel in use, in addition to the requirements of higher compressive strength, but also requires a high temperature toughness and excellent welding performance. Compared with the X70 pipeline used in the West-East Gas Pipeline Project, the yield strength of K60 pipeline steel is comparable with that of X70 pipeline steel, but its tensile strength is higher than that of X70 pipeline steel.
1. Pipeline steel
Plate and coil for the manufacture of oil, natural gas, long-distance pipelines or coal, building material slurry pipes, etc. are called steelforpipelines. Generally used in thick-walled thick-walled longitudinal welded pipe, and the coil for the production of straight seam resistance welded pipe or submerged spiral welded pipe. Domestic production capacity of 700,000 t / a spiral welded pipe with a diameter of less than 1800mm has been established in China. In recent years, a production line of straight seam thick-walled welded pipes with a caliber of less than 1600mm has been established. The domestic production of pipeline steel that meets the design requirements of the pipeline project of API 5L standard is only 10 years old, with Baosteel being the most important, as well as Ansteel, WISCO, Panzhihua Iron and Steel, Jiuquan Iron and Steel, Wugang, and other stable production of X60 ~ X70 grade pipeline steel in the international market occupies a certain position, has put into production X80 grade pipeline quality has reached the international advanced level, X100 grade pipeline steel has been developed, not yet put into mass production.
2. Technical requirements of pipeline
Modern pipelines are low-carbon or ultra-low carbon microalloyed steel, high-tech content and high value-added products, the production of pipelines almost all application of the metallurgical field nearly 20 years of all new achievements in process technology. The current pipeline project development trends are large diameter, high pressure gas transportation, cold and corrosion of the service environment, the thick-walled subsea pipeline. Therefore, modern pipeline steel should have high strength, high toughness and resistance to brittle fracture, low welding carbon content and good weldability, as well as anti-HIC and anti-H2S corrosion. Optimized production strategy is to improve the cleanliness and uniformity of steel, C≤0.09%, S≤0.005%, P≤0.01%, O≤0.002%, and take the micro-alloying, vacuum Degassing + CaSi, soft reduction in continuous casting, multi-stage thermo-mechanical rolling, and multi-functional intermittent accelerated cooling. At present, there is no toughness index for pipeline steel in pipeline specification at home and abroad, there are only specific requirements for the pipe material:
(1) Minimum service temperature (-5 ℃) DWTT ≥ 85% SA;
(2) Charpy impact absorption power ≥145J at minimum operating temperature (-5 ℃).
At present, the technical conditions of pipeline steel are generally American Petroleum Institute standards API Spec 5L, but the technical conditions of ordering specific domestic or specific users are often much more strict than API standards.
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The manufacture of boilers and power stations requires a large number of high-pressure boiler tubes, mainly steel for boiler drums, soda pipes for boilers (including superheaters, reheaters, waterwalls and economizer pipes), boilers and power station soda pipes including header, the main cold water) steel and so on. Cold-drawn seamless steel pipe thread is mainly used for boiler water wall pipe, the actual use of the site is the boiler water wall.
Water wall is the role of precipitation into high-temperature steam, its working principle is in the tube through the cooling water, the water will be carried away by the wall heat away, at the same time, the cooling water becomes heated after the high-temperature steam. Water wall tube directly to the boiler after burning high temperature gas contact, the surface withstand high temperature radiation. If the steam flow is poor or there is air bubbles attached to the pipe wall, it will result in poor heat transfer, easy to cause the pipe wall temperature is too high, ranging from the water pipe wall to reduce the service life, increase power plant maintenance shutdown time, serious but also cause the tube wall burn through, the water flow into the boiler combustion chamber, which in turn led to the explosion of the boiler safety accident. The advantage of using internally threaded seamless steel tubes as boiler waterwall tubes is that due to the concave and convex internal threads on the inner wall, the disturbance to the mixture of water and steam can be enhanced during the circulation of the soda water in the boiler waterwall, so the water vapor does not flow flatly in the tube, But the formation of turbulent flow, this flow can avoid the bubble attached to the pipe wall, to remove the steam film to prevent deterioration of film boiling worse heat transfer, can effectively improve the wall heat transfer, the wall temperature Uniform, to avoid burning phenomenon.
These subcritical and supercritical pressure boiler thermal power plant capacity, steam parameters and the major industrial countries are basically the same, and most of the well-known foreign manufacturers to introduce boiler design technology. As these boilers in the work of the temperature and pressure parameters than the previous boiler has greatly improved the use of materials and conventional boilers are also different, first demonstrated in the choice of materials, which are made by a number of foreign boilers. The boiler designed by the factory prefers to use ASME grade materials instead of the materials used in the implementation of GB5310 standard, followed by structural changes in materials. The most typical changes are concentrated on tubes for water wall tubes. In order to improve the use of drum walls, life expectancy and heat transfer effect, more than 300,000 KW subcritical and supercritical boiler water wall tubes no longer use ordinary pipe, but the use of cold drawn seamless steel pipe, the material generally used ASME series SA210A-1, SA -210C, SA213T2 and several other brands. The internally threaded seamless steel pipe is a kind of seamless steel pipe with spiral rib on the inner surface manufactured through cold drawing process.
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In the case of small deformation, the wall thickness deviation is small, and the surface roughness of the thick wall spiral steel tube decreases gradually.The large deformation of the blank wall thickness deviation will affect the wall thickness deviation of the spiral steel tube.
The researchers found that the higher the elongation, the greater the hardness, the higher the strength of the steel tube.Good overall performance.
Spiral steel pipe rolling when the flow of the material in a band, small deformation of rolling material flow beam shaped, and the tao time and subsequent heat treatment conditions between rolling technology, under the condition of same sufficiently large deformation proceeds of tubing organization distortion is more serious.
The effect of small deformation on the anisotropy of the thick-walled spiral steel tube is small.The anisotropy of mechanical properties in multipass rolling has certain fluctuation.