Stress relief annealing

See ASTM A263, A264, A265, and B432. To convert MPa to psi, multiply by 145. Stress relief annealed at 621 °C. 

Residual. Stress-relief-anneal components and assemblies following cold working or welding operations. Note, however, that annealing has no effect on applied stresses. 

Stress-relief-annealing cannot be expected to eliminate SCC in every case. Only residual stresses are reduced in stress-relief-annealing. Applied stresses, which may be responsible for the cracking, will remain. Inhibitors are not 100% effective in combating SCC. Complete coverage and inhibition is difficult to achieve, especially below deposits, in crevices, and in pits. 

Residual stresses caused by large temperature differences between the weld bead and adjacent metal can be reduced by preheating the metals to be welded, especially if the sections are thick, or by stress-relief-annealing following the welding procedure. Proper welding techniques, especially the use of appropriate weld filler metals to minimize weld-metal shrinkage, can minimize residual stresses. 

When stress-relief-annealing 300 series stainless steel components, care must be taken to avoid slow cooling through the sensitization range (see Weld Decay in this chapter). 

Spannungs-freiglUhen, n. Metal.) stress-relief anneal, -grad, m. degree of tension, spannungslos, a. without tension or strain Elec.) dead. 

Heat treatment may also affect the extent and distribution of internal stresses. These may be eliminated by appropriate annealing treatments which can remove susceptibility to stress-corrosion cracking. This must be explored in any studies of the performance of materials in environments where stress-corrosion cracking is a hazard. In particular cases, stress-relief annealing treatments may result in the appearance of new phases which, while eliminating the stress-corrosion effects, will induce another type of path of attack. This possibility must be kept in mind in assessing the overall benefits of heat treatments applied primarily for stress relief. 

Austenitic stainless steels are the most significant class of corrosion-resistant alloys for which intergranular corrosion can be a major problem in their satisfactory use. The problem is most often encountered as a result of welding but also may result from stress-relief annealing or incorrect heat treatments. Intergranular corrosion also can occur in ferritic stainless steels and in nickel- and aluminum-base alloys. 

Rigid, amorphous plastics such as polystyrene and acrylic are frequently annealed for stress relief. Annealing... 

If stress relief annealing is to be carried out on stainless austenitic steels to avoid stress corrosion cracking, tenperatures above are required because of the high strength at elevated temperatures. The use of more resistant materials can therefore be regarded as a more suitable alternative. 

Mechanical Reduce the applied stress and/or stress-relief anneal to reduce the residual stress. 

Nickel is outstandingly resistant to hot or cold alkalies. Only silver and possibly zirconium are more resistant. Nickel exposed to boiling 50% NaOH corrodes at the rate of 0.06 gmd (0.0001 ipy). It also resists fused NaOH, low-carbon nickel being preferred for this application in order to avoid intergranular attack of the stressed metal stress relief anneal, 5 min at SJ5°C (llOO F) is advisable. Nickel is attacked by aerated aqueous ammonia solutions, a soluble complex, Ni(NH3)i+, forming as a corrosion product. It is also attacked by strong hypochlorite solutions with formation of pits. 

Alloy 400 is not resistant to oxidizing media (e.g., HNO3, FeCh, CUSO4, and H2Cr04) nor to wet CI2, Br2, SO2, and NH3. The alloy is susceptible to S.C.C. in moist aerated hydrofiuoric acid and in hydrofluorosiUcic acid vapor, but susceptibility can be minimized by deaeration of the environment and by stress relief annealing the alloy component [10]. 

The presence of cladding adds to the concerns for RPV integrity, since the cladding may increase the tendency for a small, near-surface flaw to propagate into the RPV wall. It is hypothesized that cladding residual stresses are present after RPV fabrication, and that these tensile residual stresses exist in the clad layer due to the difference in thermal contraction between the stainless steel cladding and ferritic base metal which occurs during cool-down from the RPV stress relief anneal. 

To reduce internal stresses in the material by means of stress-relief annealing, high temperatures exceeding 1173 K (900 °C) are required for stainless steels due to their high levels of thermal strength. Due to these high temperatures stress-relief... 

Stress relief annealing for Beta III may consist of re-solution heat treatment or an aging heat treatment. Re-solution treatment may be accomplished in as short a time as 1 to 2 min at 715 to 730 C (1325 to 1350 °F), followed by either water quenching or air cooling. No special treatment is... 

Weldment Stress Relief Much of the available data on stress relief annealing pertains to weldments. Fusion weldments in 6.4 mm (0.250 in.) plate are reported to be stress relieved to zero residvial stress levels by any of the following treatments ... 

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