1. Full solution treatment (annealing), generally by heating to about 1080°C followed by rapid cooling, removes all residual stresses, but is not a practical treatment for most large or complex fabrications. This heat treatment not only recrystallises the work hardened grains but also takes chromium carbides (precipitated at grain boundaries in sensitised steels) back into solution in the austenite.
2. Stress relieving at temperatures below 400°C is an acceptable practice but results in only modest stress relief. Stress relieving at 425 to 925°C significantly reduces residual stresses that otherwise might lead to stress corrosion cracking or dimensional instability in service. One hour at 870°C typically relieves about 85% of the residual stresses. However, stress relieving in this temperature range can also precipitate grain boundary carbides, resulting in sensitisation that severely impairs corrosion resistance in many media. To avoid these effects, it is strongly recommended that a stabilised stainless steel (grade 321 or 347) or an extra-low-carbon type (304L or 316L) be used, particularly when lengthy stress relieving is required.
3. Low Temperature Stress Relieving
When austenitic stainless steels have been cold worked to develop high strength, low temperature stress relieving will increase the proportional limit and yield strength (particularly compressive yield strength). This is a common practice for austenitic stainless steel spring wire. A two hour treatment at 345 to 400°C is normally used; temperatures up to 425°C may be used if resistance to intergranular corrosion is not required for the application. Higher temperatures will reduce strength and sensitise the metal, and generally are not used for stress relieving cold worked products.
*** Before you select the heat treatment, it is advised to discuss with your client or metallurgist.
Please find the following reference for more detail information;
은정철 (thomaseun@hanmail.net), 스테인레스강의 실무, para. 6.2.1 Stress Relieving, (도) 대신기술, 2000
1. Full solution treatment (annealing), generally by heating to about 1080°C followed by rapid cooling, removes all residual stresses, but is not a practical treatment for most large or complex fabrications. This heat treatment not only recrystallises the work hardened grains but also takes chromium carbides (precipitated at grain boundaries in sensitised steels) back into solution in the austenite.
2. Stress relieving at temperatures below 400°C is an acceptable practice but results in only modest stress relief. Stress relieving at 425 to 925°C significantly reduces residual stresses that otherwise might lead to stress corrosion cracking or dimensional instability in service. One hour at 870°C typically relieves about 85% of the residual stresses. However, stress relieving in this temperature range can also precipitate grain boundary carbides, resulting in sensitisation that severely impairs corrosion resistance in many media. To avoid these effects, it is strongly recommended that a stabilised stainless steel (grade 321 or 347) or an extra-low-carbon type (304L or 316L) be used, particularly when lengthy stress relieving is required.
3. Low Temperature Stress Relieving
When austenitic stainless steels have been cold worked to develop high strength, low temperature stress relieving will increase the proportional limit and yield strength (particularly compressive yield strength). This is a common practice for austenitic stainless steel spring wire. A two hour treatment at 345 to 400°C is normally used; temperatures up to 425°C may be used if resistance to intergranular corrosion is not required for the application. Higher temperatures will reduce strength and sensitise the metal, and generally are not used for stress relieving cold worked products.
*** Before you select the heat treatment, it is advised to discuss with your client or metallurgist.
Please find the following reference for more detail information;
은정철 (thomaseun@hanmail.net), 스테인레스강의 실무, para. 6.2.1 Stress Relieving, (도) 대신기술, 2000