FAQ's

What is the minimum temperature for PWHT of carbon steels according to NACE MR0175?

 

Question: According to NACE MR0175, what is the minimum post weld heat treatment temperature (PWHT) for carbon and low alloy steels?

Answer: ANSI / NACE MR0175 / ISO 15156 – 2 in clause A.2.1.4 states that a minimum temperature of 620°C (1150°F) is required for low alloy steels. There is no minimum temperature requirement for carbon steels.

Question: Is PWHT mandatory as per NACE MR0175?

Answer: ANSI / NACE MR0175 / ISO 15156 – 2 in clause A.2.1.4 states that weldments that do not comply with the standard requirements (hardness) shall undergo PWHT.

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Regarding new revision of NACE MR0175/ ISO15156-2 (2015) Section A.2.1.4, I have following question:
– On 2009 revision: minimum post weld heat treatment temperature (PWHT) shall be 1150 F for Carbon and Low Alloy Steel. With the changes on 2015 “ A minimum PWHT at 1150F shall be used for low alloy steel”, is minimum PWHT temperature at 1150 F apply to Carbon Manganese steel as well or this temperature is just applicable to Low Alloy steel.?
– If minimum PWHT temperature at 1150 F is not applicable to Carbon Manganese steel, is there any minimum PWHT temperature requirement applicable to carbon manganese steel?
(MP INQUIRY #2017-13)
ANSWER:
Q1: Regarding NACE MR0175/ ISO15156-2 (2015) Section A.2.1.4, the 2009 revision states that the minimum post weld heat treatment temperature (PWHT) shall be 1150 F for Carbon and Low Alloy Steel. The 2015 revision states “ A minimum PWHT at 1150F shall be used for low alloy steel”. Does the minimum PWHT temperature at 1150 F apply to Carbon Manganese steel as well or this temperature is just applicable to Low Alloy steel?
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A1: The 1150F requirement is specific to low alloy steels. Note that carbon and carbon manganese steels still are required to comply with the hardness requirements as defined in Table A.1 when the SMYS exceeds 52 ksi. As noted in Clause A.2.1.4, as-welded carbon steels, carbon-manganese steels and low-alloy steels that comply with the hardness requirements of Table A.1 do not require post-weld heat treatment.
Q2: If minimum PWHT temperature at 1150 F is not applicable to Carbon Manganese steel, is there a minimum PWHT temperature requirement?
A2: There is no specific defined PWHT minimum temperature defined for carbon and carbon-manganese steels. The PWHT requirement is that it must yield a product that complies with the other requirements defined by NACE MR0175/ ISO15156-2 Clause A.2.1.4

Reference MP Inquiry 2017-13 (NACE MR0175 Part 2 A.2.1.4)

 

 

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