1. Causes of soft spots on the mold surface:
(1) The surface of the mold has an oxide scale, rust spots, and partial decarburization before heat treatment.
(2) After the mold is quenched and heated, the cooling and quenching medium is improperly selected, and there are too many impurities or aging in the quenching medium.

2. Preventive measures for soft spots on the mold surface:
(1) Oxide scale and rust spots should be removed before heat treatment of the mold. The surface of the mold should be properly protected during quenching and heating. Vacuum electric furnaces, salt bath furnaces, and protective atmosphere furnaces should be used for heating as much as possible.
(2) When cooling the mold after quenching and heating, a suitable cooling medium should be selected, and the cooling medium used for a long time should be filtered frequently or replaced regularly.

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