Heat treatment of large-diameter seamless steel pipe forgings, large forgings are mainly forged directly from steel ingots. Therefore, the effects of smelting, ingot casting and forging on the internal quality of castings must be considered during heat treatment. The main influencing factors are: chemical composition is not Uniformity for the presence of multiple smelting defects; coarse and very coarse 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 much higher than that of ordinary straight seam 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 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). Thick finished steel 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. For more about seamless steel pipe, visit this page:https://www.hu-steel.com/product85_1000.html
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