Austempering of Seamless Steel Tube

Subcritical quenching temperature between 740 - 810when selected. Subcritical quenching select the heating temperature 780, quenching holding time 15min; select after quenching and tempering temperature 630, tempering heating holding time 50min. Since subcritical quenching heated two phase region, while retaining part of the state of undissolved ferrite under quenching, while maintaining high strength and toughness can be improved. At the same temperature than conventional low temperature quenching, quenching reduces stress, thus reducing the hardening of the deformation, so to ensure the smooth operation of the production of heat, but also for the subsequent car Sijia provide good material. At present, the technology has been applied steel pipe plant in Tianjin steel pipe, warranty data show that the yield strength of steel heat treatment after Rt0.6 in 820 - 860MPa, tensile strength Rm in 910 - 940MPa, impact toughness Akv in 65 - 85J Room invulnerability performance 100 percent qualified. Data show that the steel is already quite high quality steel grade oil casing, on the other hand also shows that the subcritical quenching process is a great way to avoid the production of steel products during high-temperature brittleness.

Such as carbon seamless steel pipe and other lower hardenability of steel isothermal hardening, should be appropriate to increase the quenching temperature, H is to increase the stability of the austenite to avoid and prevent the occurrence of high temperature non Bayesian isothermal process changing body. Austempering restrictions steel and seamless pipe size. During austempering, the basic principle is to ensure that change does not happen seamless steel high temperature in the cooling process, and therefore the size of seamless steel pipe steel grades and a direct impact on the quality of the isothermal quenching, the general requirements for the carbon steel seamless pipe The effective thickness should be less than 5mm, the effective thickness of steel should be less than 30mm. From the perspective of the carbon content in the 0.4% to 0.6% of the carbon is not suitable for austempering, higher than 0.6% carbon steel to isothermal quenching. Austempering temperature and time should be determined according to the performance requirements of seamless steel tubes, with reference to the steel of C curve, in principle, all the austenite into bainite, usually on the cooling medium bath nitrate solution, in order to ensure temperature stability, should be added to the cooling means in the medium, the medium to prevent the increase in temperature affect the quenching quality. Moreover, etc. should be based on the length of time the temperature transition end seamless steel tubes organizations as a benchmark, long working efficiency is reduced, and therefore should be taken seriously. Isothermal hardening of seamless steel pipe and some may be tempered. But for some ^'s body hardening of the workpiece, the internal residual austenite will be transformed in the subsequent air cooling process is martensite, and therefore must be tempered, the purpose is to eliminate brittleness and stable seamless steel ruler, note the tempering temperature should be below the isothermal temperature.