Cryogenic Treatment: Practical Tips for Reducing Defects in Mold Processing 

Causes and Preventive Measures for Quenching Cracks:

Shape Effect: Primarily caused by design factors such as excessively small fillet radii (R), improper placement of holes, and poor section transitions.
Overheating (Overburning): Mainly resulting from inaccurate temperature control, temperature fluctuations, non-standardized vacuum heat treatment processes, inadequate tempering, excessively high set temperatures, and uneven furnace temperatures. Preventive measures include inspecting and calibrating the temperature control system, revising process temperatures, and placing spacers between workpieces and the furnace floor.
Decarburization: Caused by factors such as overheating (or overburning), unprotected heating in air furnaces, insufficient machining allowance, and residual decarburized layers from forging or preliminary heat treatment. Preventive measures include using controlled atmosphere heating, salt bath heating, vacuum furnaces, box furnaces with protective packaging or anti-oxidation coatings, and increasing machining allowance by 2-3mm.
Improper Cooling: Mainly due to inappropriate coolant selection or excessive cooling. Preventive measures include understanding the cooling characteristics of quenching media and employing tempering treatments.
Poor Raw Material Microstructure: Such as severe carbide segregation, poor forging quality, and improper preliminary heat treatment methods. Preventive measures include adopting correct forging processes and reasonable preliminary heat treatment regimes.
Insufficient Hardness

Causes and Preventive Measures for Insufficient Hardness:

Low Quenching Temperature: Primarily caused by improper process temperature settings, temperature control system errors, and incorrect methods of loading the furnace or immersing in the cooling bath. Preventive measures include revising process temperatures, inspecting and calibrating the temperature control system, ensuring workpieces are evenly spaced and loaded individually into the bath, and avoiding stacking or bundling.
High Quenching Temperature: Resulting from improper process temperature settings or temperature control system errors. Preventive measures include revising process temperatures and inspecting and calibrating the temperature control system.
Over-Tempering: Caused by excessively high tempering temperature settings, temperature control system failures, or loading into the furnace at elevated temperatures. Preventive measures include revising process temperatures, inspecting and calibrating the temperature control system, and ensuring workpieces are not loaded above the set furnace temperature.
Improper Cooling: Causes include prolonged pre-cooling time, inappropriate coolant selection, reduced cooling performance due to rising quenching medium temperature, poor agitation, and high removal temperatures from the bath. Preventive measures include rapid removal from the furnace and immersion in the bath, understanding the cooling characteristics of quenching media, maintaining oil temperatures between 60-80°C and water temperatures below 30°C, adding or changing cooling media when temperatures rise due to high quenching loads, enhancing coolant agitation, and removing workpieces at Ms + 50°C.
Decarburization: Caused by residual decarburized layers in raw materials or during quenching heating. Preventive measures include using controlled atmosphere heating, salt bath heating, vacuum furnaces, box furnaces with protective packaging or anti-oxidation coatings, and increasing machining allowance by 2-3mm.