Scrap metal shearing operates under harsh working conditions, which places high demands on the quality of the shear blades, particularly in terms of strength and toughness.

H13 is an alloy tool steel. Because it contains a large amount of alloying elements, it has excellent hardenability. After quenching, a considerable amount of retained austenite often remains in the microstructure. This retained austenite continues to transform into martensite only during the cooling process after tempering, which is known as “secondary quenching.”

After the first tempering, the formation of new martensite generates new internal stresses. In addition, some retained austenite may still remain untransformed. Therefore, a second tempering or even a third tempering treatment is required.

The tempering temperature is generally between 550–600°C, and the tempering time depends on the furnace load and the effective thickness of the blades.