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Rough Machining of Die Casting Dies: Preventing Cracking in Heat Treatment

This booklet provides guidelines to die builders, heat treaters, and die casters for rough machining of die casting dies. It focuses on avoiding problems during the heat treatment process, such as distortion and cracking. The booklet outlines factors to consider during rough machining and emphasizes the importance of controlling the quenching rate. It also provides recommendations for minimizing stresses during quenching.

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Rough Machining of Die Casting Dies: Preventing Cracking in Heat Treatment

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  1. Rough Machining of Die Casting Dies:Allowing for Distortion and Avoiding Cracking During Heat Treatment Stephen P. Midson The Midson Group, Inc.

  2. Rough Machining Booklet • New booklet from NADCA • Provide guidelines to die builder, heat treaters & die casters • Avoiding problems during heat treatment of dies

  3. Leaving appropriate amounts of machining stock on die Reducing stress that can lead to gross cracking Notifying heat treater of any welding performed on die Scope of Booklet

  4. Need for booklet was identified by: Mark Baleja Joe Price Gene Hainault Content is based on a presentation developed by: Bohler Uddeholm Corp Paulo Products Company Acknowledgements

  5. Two main sections Briefly review heat treatment processes for die casting dies Describe sources of stresses & warping Identifying factors that must be considered during rough machining Outline of Booklet

  6. First Section • Describes importance of maximizing quench rate during heat treatment • Summarizes data from recent paper from Schwam, Wallace & Birceanu

  7. First Section • Also describes problems that can occur if quenching rate is too fast • Stresses originating from: • Expansion & contraction of steel • Expansion during phase transformation from austenite to martensite

  8. Emphasizes the important of controlling the quenching rate NADCA recommends 50oF/min for Premium Grade H-13 First Section

  9. Outlines factors that die builders and heat treaters must consider during rough machining To ensure stresses developed during quenching do not damage die To ensure appropriate machining stock is left on die Second Section

  10. Machining Stock • Discuss • Ballooning • Die corners pulling up • Bowing of die edges

  11. Minimizing Stresses During Quenching • Use generous radii • Use generous shoulders between transitions in cross sections • Avoid thin walls & thin webs • Remove white layer after EDM

  12. Specific recommendations NOT made in report Minimum machining stock Minimum radii HIGHLY RECOMMENDED that machine shops communicate closely with heat treaters Before the die is machined Recommendations

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