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Dec 25, 2017


When the Cr12MoV steel is quenched at 980 ℃ (ie, low quenched), the carbides melt less, the carbon content of the matrix is about 0.5%, Cr is 6%, molybdenum is only 0.5%, vanadium is melted less, The amount of carbide in the matrix is about 15%, while the residual austenite is only 20% or less, the hardness after quenching HRC60 ~ 62. Due to the low carbon content of the matrix, the quenched matrix has high toughness. But the compressive yield strength does not reach the high level, the low quenching temperature generally can only take low temperature (180-200 ℃) tempering, suitable for low load, high speed cold die, low temperature tempering hardness HRC> 60, tempering times two Times.

Cr12MoV steel with quenching temperature (1025-1030 ℃) (that is, the normal quenching) to improve the carbon concentration of the matrix, the alloy carbide is further melted, the maximum hardness, while the amount of retained austenite also rose to nearly 40%. Quenching hardness HRC62-63 or so. Quenching in the quenching temperature can be 180-200 ℃ low temperature tempering, access to the highest hardness and best wear resistance, but slightly lower toughness, can not be used in heavy-duty die. After the quenching temperature quenching 380-400 ℃ can be tempered, but the hardness will drop to HRC58 or so, can get the best strength and toughness and significantly improve the cold forging die fracture resistance, but wear resistance decreased.

Cr12MoV steel above 1050 ℃ temperature quenching (ie, high quenching) are high quenching temperature quenching. With the increase of quenching temperature, carbon and alloying elements and carbides further melt into austenite, the carbon and alloying elements increase, the stability of austenite increases, and the amount of retained austenite after quenching also rises sharply To 40-60%, or even higher, the hardness of the quench is reduced to about HRC55 due to the increased amount of retained austenite. Due to the increase of retained austenite and the increase of austenite stability, low-temperature tempering can not transform austenite, and only high-temperature tempering can promote a large amount of austenite transformation. Improve its hardness (1150 ℃ quenching, the quenching hardness may fall below HRC45-50) secondary hardening phenomenon. Tempering at high temperature (520-540 ℃), be sure to conduct three tempering. In addition, with the increase of the quenching temperature, the grain size in steel rapidly grows, and the grain size at 1080 ° C is as long as 9 grades, even at 1150 ° C or even 7-8 grades. Quenching temperature to reduce the amount of carbides (volume fraction) decreased, so the toughness decreased, wear resistance also decreased, but red hardness increased. Therefore, only when high-impact, low-load and red hardness are required, the high-quenching and high-recovery process is adopted. After high temperature tempering hardness can reach above HRC62, it should be noted that the secondary hardening of the high temperature tempering temperature to a very narrow, for Cr12MoV steel at 520 ℃, Cr12Mo1V1 at 540 ℃, beyond this temperature range (often only ± 5 ℃), the hardness of the larger fluctuations. If it is Cr12 steel, the heating temperature can be a little higher without anti-1000 degrees is below. Insulation 30-40 points enough. Quenching to 60HRC above is convenient. Cr12 steel quality gap is very large, high forging requirements. Forging to "two light and six heavy forging", so that the distribution of carbide as uniform, but in fact simply can not meet the requirements.

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