What is the application of large diameter seamless steel pipe?

The proper selection and use of the electrode directly affects the chemical composition and performance of the weld, which is an important part of the preparation of large-diameter seamless steel pipe welding. Choosing the right electrode requires a comprehensive consideration of various factors, and sometimes it needs to be tested and verified before it can be finalized. The aspects to be considered are as follows: the performance requirements of the weld metal, the shape of the electrode, the rigidity and the position of the weld, the crack resistance of the weld metal, the processability, equipment and construction conditions, and economic rationality.

Large-scale forging of large-diameter seamless steel pipe forgings is mainly forged directly from steel ingots. Therefore, the effects of smelting, ingot casting and forging on the internal quality of the casting must be considered in the heat treatment, as long as the influencing factors are: uneven chemical composition. The existence of a variety of smelting defects; coarse and very uneven grains; more gases and impurities; greater forging stress and heat treatment stress. The purpose of heat treatment after forging large forgings is to prevent white spots and hydrogen embrittlement, improve the internal structure of forgings, eliminate forging stress, reduce hardness and improve cutting performance, so that it can obtain good mechanical properties or prepare for later heat treatment.

Forging of large diameter seamless steel pipes is a casting of large forgings. The difference between large-diameter seamless steel pipes and welded pipes is mainly due to different molding processes. Ordinary steel pipes, such as tap water pipes, are usually welded by bending the flat plate. You can find a weld on the top; the coarser diameter is usually a spiral weld. The seamless steel pipe is generally formed by laminating molten steel in a molten state through a ring slit and then being subjected to a stretching process, so that there is no weld. In terms of performance, especially the pressure bearing capacity is greatly improved compared with ordinary steel pipes, so it is often used on high-voltage equipment. Such as the piping connection of hydraulic equipment. The weld joint of ordinary steel pipe is its weak link, and the weld quality is also the main factor affecting its overall performance. People who have lived in the north generally have experienced the experience of freezing water pipes or heating pipes in the winter. The places where the explosions are usually welded. The welded pipe is not a seamless steel pipe. Seamless steel pipe production process The seamlessness of steel pipe is mainly achieved by tension reduction. The tension reduction process is a continuous rolling process of hollow base metal without core rod. Under the premise of ensuring the quality of the welding of the parent pipe, the pipe tension reduction process is to heat the whole welded pipe to 950 degrees Celsius or more, and then to various outer diameters and walls by a tension reducer (a total of 24 times of the tension reducer). The thick finished pipe, the hot-rolled steel pipe produced by this process is intrinsically different from the ordinary high-frequency welded pipe. After heating by the heating furnace, the metallographic structure and mechanical properties of the weld bead and the parent body can be completely consistent. Moreover, the large diameter is not The seam steel pipe is rolled and automatically controlled by a multi-pass tension reducer to make the dimensional accuracy of the steel pipe (especially the roundness and wall thickness accuracy of the pipe) superior to that of the similar seamless pipe.

In the world's developed countries, fluid pipes and boiler tubes have been widely used in the seamless process of steel pipes. With the development of society, the situation that domestic hot-rolled welded pipes gradually replace seamless pipes has been formed. The difference between seamless steel pipe and large diameter seamless steel pipe can be determined from several aspects. First, the welded pipe is generally fixed length, and generally 6 meters, 9 meters or 12 meters. There are very few fixed-length steel tubes, because the factory has a lot of price increases. The second can be seen from the cross section of the tube head. If there is rust, wipe it clean. If you look carefully, you will find the weld zone. Third, if it is pickled, it is most obvious. After the coating of the material coating, the quality of the pretreatment in the steel pipe indirectly affects the adhesion strength of the coating. The external pretreatment amount of large-diameter plastic coated steel pipe should reach the Sa2 level specified in the GB/T8923 scale. It can be coated with various plastic coatings of various properties such as polyvinyl chloride, polyethylene and epoxy resin according to different needs. It has good adhesion, strong corrosion resistance, strong acid resistance, strong alkali and other chemical corrosion, and is non-toxic. It is non-rust, wear-resistant, impact-resistant and penetrable. The surface of the pipe is smooth and does not adhere to any substance. It can reduce the resistance during transportation, increase the flow rate and conveying efficiency, and reduce the transmission pressure loss. The coating has no solvent and no exudable substances, so it will not pollute the medium to be transported, thus ensuring the purity and hygienicity of the fluid. It can be used alternately between -40 Â° C and +80 Â° C in the range of hot and cold cycles, without aging, It does not crack and can be used in harsh environments such as cold areas. The anchor pattern has a lightness of 50 Î¼m to 75 Î¼m. The steel pipe with external pretreatment work should be coated within 6 hours, and should be treated again after 6 hours of super work. Large-diameter seamless steel tubes have large elastic deformation, and improper operation during construction may cause large-diameter steel pipes to have large vertical deformation and instability, which seriously affects the use function.