What is the Stress Relieved in Welding?
The reheating of a weldment to a temperature below the transformation temperature and holding it for a specified period of time. A frequently used temperature and time is 1150°F for one hour per inch of thickness. This reheating removes most of the residual stresses put in the weldment by the heating and cooling during welding.
Stress relieving is often done after fabrication is complete and before final heat treatment. It can be used to remove stresses resulting from such operations as machining, shot peening, or grinding. It is also done to improve the dimensional stability of a component prior to final heat treatment or to prepare it for cold working.
There are two basic types of stress relieving: full stress relief and partial stress relief. Full stress relief means heating the entire part to the prescribed temperature and holding it long enough for all of the residual stresses to be relieved. Partial stress relief means heating only those areas where stresses are concentrated, such as at welds, corners, or bossed areas.
The choice of stress relieving method depends on the type of component being treated, the desired results, and the equipment available. Some common methods are:
- torch heating,
- inductive heating,
- resistance heating.
Furnace stress relieving is generally used for small parts or when a uniform temperature over the entire part is required. The workpiece is placed in a furnace and heated to the desired temperature. It is then held at that temperature long enough for the stresses to be relieved.
Torch stress relieving is generally used for larger parts or when a localized heat source is required. The torch is moved over the surface of the part, heating it to the desired temperature. As with furnace stress relieving, the part is then held at that temperature long enough for the stresses to be relieved.
Inductive stress relieving uses an inductor to generate an electromagnetic field that heats the workpiece. This method is generally used for small, delicate parts that cannot withstand the high temperatures of other methods.
Resistance stress relieving uses electrical resistance to generate heat in the workpiece. This method is generally used for small parts or when very accurate temperature control is required.
When should you stress relieve welds?
The answer to this question depends on the application. In general, however, it is recommended that welds be stress relieved whenever possible. This is because welds are often the weakest point in a component and can be the source of stress concentrations. Stress relieving welds can help to improve the overall strength and stability of a component.
What is the most common method of stress relieving welds?
The most common method of stress relieving welds is torch heating. This is because it is a relatively simple and inexpensive method that can be used on a wide variety of components. Torch heating also has the advantage of being able to heat localized areas, which is often desirable when stress relieving welds.
What is stress-relieved steel?
Stress-relieved steel is steel that has undergone stress relieving. This is a heat treatment process in which the steel is heated to a temperature below its transformation temperature and held at that temperature for a period of time. Stress-relieved steel is often used in applications where high levels of stress are expected, such as in shafts or gears.
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