The the difference impacted strength for the finished steel from direct quenching ,temprring and ausstenitic state
Direct quenching and tempering prior austenite state can affect the strength of finished steel - balance toughness. Under the present circumstances, the purpose of this study was to examine the tempering process parameters and composition of its impact, it is important that all austenitic steels have similar status. This is confirmed by the three-dimensional parameter austenite OK. Austenite grain size and morphology is very similar in all cases. There are slightly more high-Mo steel flat austenite grain size and morphology, but we think it will not significantly affect the results obtained.
The results show that there is a high heating rates and short-term peak temperature insulation rapid induction tempering process can produce a finer, more uniform carbide structure in the tempered martensite, and, as expected, moved to carbide ball higher tempering temperature. In other places also made similar observations. The reason for this phenomenon is due to the higher heating rates when heated to a higher temperature carbide nucleation rate is higher, and more fine dispersed carbides. It is also considered to improve the heating rate can delay martensite dislocation structure of reply, leaving the high density of heterogeneous nucleation point for the new carbide. In the present case, it is clear that the holding time has important implications for the distribution of carbides: the traditional heat treatment time makes diffusion more fully dispersed. If by Hollomon Jaffe parameter considering these effects, it can be seen on the ball of temperature both tempering process is similar. Induction tempering in the case of not holding a peak temperature of 655 ℃ after tempering, carbides spheroidized become apparent, however, traditional tempering for 30min, at a peak temperature of 545 ℃ can see carbide ball of. Comprehensive Hollomon-Jaffe parameter 16.32 and 16.13, respectively, which largely explains the observed differences in temperature of the ball: two kinds of heat treatment method showed a tempering effect tempering effect and P values given roughly the same.
Surprisingly, as seen as Hayashi and furuhara etc., etc., even if the induction heating of high heating rates carbide finer and more uniform, induction tempering process on the strength - ductility - Impact toughness balance and no significant beneficial effect. However, the two have had a good temper mechanical properties in combination: even in the absence of quenched and tempered, hardened steel flat directly austenite exhibits good toughness - strength balance.
For a given composition range of about 1000MPa yield strength and research of, 0.10% C 0.18% C over the -40 ℃ to get better Charpy V-impact toughness. Although the test results do not express P and S are each separately influence, but still can be seen, the P and S content of the low performance is advantageous. Interestingly, however, is that for a given yield strength, 0.2% Mo and 0.1% C steel test toughness higher than 0.4% Mo steels of test. Test steels pay more adverse impact of 0.2% Mo exact cause further studies are needed to explain.
