Effect of cooling rate on structure and hardness of quenched steel
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It was shown that by varying the relative motion of heated samples in water one can achieve very high cooling rates. A cooling rate of 7000 deg/sec at a depth of 1 mm can be attained in samples 6×6 ×8 mm.
The microhardness of low-carbon steel is increased by raising the cooling rate from 1000 to 7000 deg/sec during quenching.
In commercially pure iron (0.06% C) the increase in microhardness is accompanied by an increase in microdeformation and refining of the mosaic blocks; in steel with 0.15% C one observes only refining of the blocks, while the microdeformation decreases.