When carbon steel is quenched by water quenching, a white network or block structure appears in the metallographic inspection structure. At this time, there is uneven hardness in the hardness test.
When the chemical composition of the steel is constant, when large-section bolts are quenched, due to the effect of hardenability, the cooling rate from the surface to the core changes from fast to slow. At this time, the white network or block structure is usually considered to be the first common The shape of ferrite is transformed from intermittently fine semi-network to coarse network, because under normal circumstances, the quenching temperature does not appear too much deviation, and the probability of undissolved ferrite in the quenched structure is small. Eutectoid first The shape of ferrite is related to the cooling rate.
Therefore, during the organization inspection, the cooling rate should be checked first, and then the chemical composition and heating temperature should be considered to find the real reason.
