According to the actual production situation, we believe that the main reason of quenching crack of 4140 steel plate is:
If the use of water as quenching medium, 4140 steel cooling speed is faster at high temperature range, but the cooling speed is slow at low temperature range lower than the Ms temperature. The water temperature rises, the cooling ability decreased at the high temperature range, but the cooling capacity almost unchanged at the low temperatures. When the 4140 steel is cooled to below Ms temperature, martensite phase transition, volume expansion, have second kinds of distortion, second kinds of stress, and the macro structure stress and thermal stress, so prone to quenching crack.
If the cooling rate is too fast will produce tissue stress when the tempering, lead to 4140 steel generate longitudinal crack.
The annular crack of steel edge is because of edge nonuniform chamfer lead to stress concentration when quenching.
The above article from Songshunsteel official website (http://www.songshunsteel.com/)
The original address: http://www.songshunsteel.com/news_show_27_15_69.html, reproduced please specify. songblog1504
If the use of water as quenching medium, 4140 steel cooling speed is faster at high temperature range, but the cooling speed is slow at low temperature range lower than the Ms temperature. The water temperature rises, the cooling ability decreased at the high temperature range, but the cooling capacity almost unchanged at the low temperatures. When the 4140 steel is cooled to below Ms temperature, martensite phase transition, volume expansion, have second kinds of distortion, second kinds of stress, and the macro structure stress and thermal stress, so prone to quenching crack.
If the cooling rate is too fast will produce tissue stress when the tempering, lead to 4140 steel generate longitudinal crack.
The annular crack of steel edge is because of edge nonuniform chamfer lead to stress concentration when quenching.
The above article from Songshunsteel official website (http://www.songshunsteel.com/)
The original address: http://www.songshunsteel.com/news_show_27_15_69.html, reproduced please specify. songblog1504
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