Hi Srinivas, Pls.refer to AWS D1.1-Section 5.8 for SR.Also Pls.find below the extraction of that. 5.8 Stress-Relief Heat Treatment Where required by the contract documents, welded assemblies shall be stress relieved by heat treating. Final machining after stress relieving shall be considered when needed to maintain dimensional tolerances. 5.8.1 Requirements. The stress-relief treatment shallconform to the following requirements: (1) The temperature of the furnace shall not exceed 600°F [315°C] at the time the welded assembly is placed in it. (2) Above 600°F, the rate of heating shall not be more than 400 °F per hour divided by the maximum metal thicknessof the thicker part, in inches, but in no case more than 400°F per hour. Above 315°C, the rate of heating in °C/hr shall not exceed 5600 divided by the maximum metal thickness, in millimeters, but not more than 220°C/hr. During the heating period, variations in temperature throughout the portion of the part being heated shall be no greater than 250°F [140°C] within any 15 ft [5 m] interval of length. The rates of heating and cooling need not be less than 100°F [55°C] per hour. However, in all cases, consideration of closed chambers and complex structures may indicate reduced rates of heating and cooling to avoid structural damage due to excessive thermal gradients. (3) After a maximum temperature of 1100°F [600°C] is reached on quenched and tempered steels, or a mean temperature range between 1100°F and 1200°F [600°C and 650°C] is reached on other steels, the temperature of the assembly shall be held within the specified limits for a time not less than specified in Table 5.2, based on weld thickness. When the specified stress relief is for dimensional stability, the holding time shall be not less than specified in Table 5.2, based on the thickness of the thicker part. During the holding period there shall be no difference greater than 150°F [85°C] between the highest and lowest temperature throughout the portion of the assembly being heated. (4) Above 600°F [315°C], cooling shall be done in a closed furnace or cooling chamber at a rate no greater than 500°F [260°C] per hour divided by the maximum metal thickness of the thicker part in inches, but in no case more than 500°F [260°C] per hour. From 600°F [315°C], the assembly may be cooled in still air. 5.8.2 Alternative PWHT. Alternatively, when it is impracticalto PWHT to the temperature limitations stated in 5.8.1, welded assemblies may be stress-relieved at lower temperatures for longer periods of time, as given in Table 5.3. 5.8.3 Steels Not Recommended for PWHT. Stress relievingof weldments of ASTM A 514, ASTM A 517, ASTM A 709 Grades 100 (690) and 100W (690W), and ASTM A 710 steels is not generally recommended. Stress relieving may be necessary for those applications where weldments shall be required to retain dimensional stability during machining or where stress corrosion may be involved, neither condition being unique to weldments involving ASTM A 514, ASTM A 517, ASTM A 709 Grades 100 (690) and 100W (690W), and ASTM A 710 steels. However, the results of notch toughness tests have shown that PWHT may actually impair weld metal and HAZ toughness, and intergranular cracking may sometimes occur in the grain-coarsened region of the weld HAZ. Thanks & Regards, (Karthik) Karthikeyan.S QA/QC Manager Getabec Energy Co.,Ltd. 379,Moo6,Soi8,Nikhomphatana, Rayong-21180, Thailand. Phone: 0066 38 897035-8 (Off) Fax: 0066 38 897034 Hand Phone: 0066 892512282 --- On Sat, 8/28/10, Srinivas Engr <srinivas.gmsrini@gmail.com> wrote:
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