QW-407 Postweld Heat Treatment

[tong tong]

QW-407 Postweld Heat Treatment

QW-407.1 A separate procedure qualification is
required for each of the following conditions:
(a) For P-No. 1, P-No. 3, P-No. 4, P-No. 5, P-No. 6,
P-No. 9, P-No. 10, and P-No. 11 materials, the following
postweld heat treatment conditions apply:
(1) no PWHT
(2) PWHT below the lower transformation temperature
(3) PWHT above the upper transformation temperature
(e.g., normalizing)
(4) PWHT above the upper transformation temperature
followed by heat treatment below the lower transformation
temperature (e.g., normalizing or quenching
followed by tempering)
(5) PWHT between the upper and lower transformation
temperatures
(b) For all other materials, the following postweld heat
treatment conditions apply:
(1) no PWHT

(2) PWHT within a specified temperature range

QW-407.4 For ferrous base metals other than P-No. 7,
P-No. 8, and P-No. 45, when a procedure qualification test
coupon receives a postweld heat treatment exceeding the
upper transformation temperature, the maximum qualified
base metal thickness, T, shall not exceed 1.1 times the
thickness of the test coupon.

Dear Members,

Above mentioned subject and clauses are referred..I have a few question to ask..

1.  What "PWHT below the lower transformation temperature" means and from where we can get the value of temperature?

2.  What "PWHT above the upper transformation temperature" means and from where we can get the value of temperature?

3.  What "PWHT within a specified temperature range" means and it is from code and standard such as B31.3, ASMEVIII or etc?

I really need your expertise opinion. Thank in advance

Regards

Tong

[Sukamal Naskar]

Dear Tong,

 

 According to Fe-Fe3C diagram,

The temperature below A1 line is the lower transformation temperature. For plain carbon steel , A1 temperatute is 723 deg C.

 

The temp. above A3 line is the upper transformation temperature. this temperature is not constant like A1 in case of plain carbon steel. The temperature varies on the wt.% carbon. As the wt% carbon increases , the temperature decresses upto 0.8% carbon. then increases.

 

This A1 & A3 line depends on the alloy elements. this lines can be shift using different alloy elements, like Austenite stabilizors or ferrite stabilazors.

 

Normally we do PWHT or Stress Relive ( SR) below A1 temperatue. In ASME Sec VIII Div.1, you can get the temperature reference in UCS-56.

 

for upper transformation temperature, normally we select the temperature A3 + 30 ~40 deg C. You can get the reference for the upper transformation temperature from that material's Normalising temperature in ASME Sec II , Part A.

 

In ASME Sec VIII  Div1, UCS-56, you will get few P Number materials they have given the temperature ranges for PWHT, rest all they have specified the minimum temperature for the PWHT.

 

Regards,