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

NADCA Die Materials Committee Rough Machining Booklet New booklet from NADCA Provide guidelines to die builder, heat treaters & die casters Avoiding problems during heat treatment of dies

NADCA Die Materials Committee Scope of Booklet 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

NADCA Die Materials Committee Acknowledgements 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

NADCA Die Materials Committee Outline of Booklet Two main sections 1.Briefly review heat treatment processes for die casting dies 2.Describe sources of stresses & warping »Identifying factors that must be considered during rough machining

NADCA Die Materials Committee First Section Describes importance of maximizing quench rate during heat treatment Summarizes data from recent paper from Schwam, Wallace & Birceanu

NADCA Die Materials Committee 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

NADCA Die Materials Committee First Section Emphasizes the important of controlling the quenching rate NADCA recommends 50 o F/min for Premium Grade H-13

NADCA Die Materials Committee Second Section 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

NADCA Die Materials Committee Machining Stock Discuss »Ballooning »Die corners pulling up »Bowing of die edges

NADCA Die Materials Committee 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

NADCA Die Materials Committee Recommendations 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