Here are 8 reasons why you might want to consider stress relieving the steel before machining your parts.
- High carbon grade of steel. Alloy grades over 0.40 carbon and carbon grades above 0.50 carbon can often benefit from stress relief.
- Heavy draft to make size. Heavy draft can add cold working strain which can set up stresses in the part.
- Small diameter parts. The percentage of cold work (strain) is higher for the same draft reduction as diameter decreases.
- Long parts. Stresses tend to display and their effects increase longitudinally.
- Assymetric parts– and parts with large differences in section or mass.
- To increase mechanical properties. At lower stress relieving temperatures, the hardness, tensile strength, and elastic properties of most cold drawn steels increase.
- To decrease mechanical properties. At higher stress relieving temperatures, hardness, tensile strength and yield strength are reduced while % elongation and 5 reduction of area are increased.
- To reduce distortion off the machine. Usually stress relieving is used as a last ditch effort to reduce the distortion that presents after machining a part with some or many of the characteristics given above.
Stress relieving is a lower than the material’s critical point thermal treatment also known as strain drawing, strain tempering, strain annealling, strain relieving, or pre-aging. It is performed to modify the the magnitude and distribution of of residual forces within a cold drawn steel bar, as well as to modify the mechanical properties.