Effects of Heat Treating on Part Size
Understanding the factors that influence changes in part size during heat treatment can allow for more accurate estimates in preparation for final machining operations.
A common concern when heat treating parts is knowing how much the size of the parts will change. While the heat treater can often provide a rough estimate, the figures typically are not accurate enough to allow for final machining and/or grinding to close tolerances prior to heat treatment. The uncertainty stems from the number of variables introduced by the heat treating process. Taking these factors into consideration can help to provide an understanding for requirements for the final machining operations.
In the article “Predicting Size Change from Heat Treatment,” the authors look at the key considerations in estimating size change, and note that experimentation and process control can help to provide fairly accurate, consistent results. The article provides a short case study of a tooling manufacturer who, through careful monitoring of specific controllable variables and through precise control of heat treat parameters, is now able to predict size change during heat treatment of dies to within ± 0.001 inch.
See the article for more specific detail about the variables related to heat treating and those specifically affecting dimensional change.