Managing Thermal Expansion Tolerances and Yield Loss across Scaled High Speed Stamping Dies
Active thermal control and cryogenic substrate stabilization eliminate shut-height drift and thermal scrap loss in high-speed progressive stamping dies.
Retained Austenite
Meaning
Metallurgical phases in steel consist of the original high temperature structure that failed to transform during quenching. Retained austenite exists as soft pockets within the harder martensitic matrix of a tool. The presence of this phase is determined by the chemistry of the steel and the speed of the cooling process.
Hardness Impact
High levels of this phase reduce the overall hardness and wear resistance of a die. Because retained austenite is softer than martensite, the tool might deform under the high pressures of a stamping run. This softening leads to shorter tool life and more frequent regrinding.
Volume Change
External stress or temperature drops can cause this phase to transform into martensite long after the tool is finished. When this transformation occurs, the tool expands because martensite takes up more space than retained austenite. This growth can ruin the precision of the die and lead to clearance issues.
Thermal Treatment
Sub zero cooling or multiple tempering cycles are used to minimize the amount of this phase. Measuring the percentage of retained austenite involves using X ray diffraction to analyze the crystal structure of the metal. Keeping the levels low ensures the dimensional stability of high precision manufacturing components.