Saturday, August 28, 2010

Re: [MW:6756] What is SR(PWHT) thickness requirements by AWS D1.1

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 shall

conform 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 thickness

of 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 impractical

to 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 relieving

of 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:

From: Srinivas Engr <srinivas.gmsrini@gmail.com>
Subject: [MW:6753] What is SR(PWHT) thickness requirements by AWS D1.1
To: "Materials & Welding" <materials-welding@googlegroups.com>
Date: Saturday, August 28, 2010, 11:46 AM

Dear all,

what r thickness to be done for SR(PWHT) for CS according to AWS D1.1
structural steel code?
Where to refer in AWS D1.1? for thickness requirements for PWHT?

Thanks
Srinivas

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