FAQ's

4130, 4140 and low alloys. When does NACE MR0175 require SSC testing for qualification?

NACE MR0175/ISO 15156 in part 2 / Annex A does quote 4130 grades A.2.2.3.2 Tubulars and tubular components made of Cr-Mo low-alloy steels (UNS G41XX0, formerly AISI 41XX, and modifications), if quenched and tempered in the tubular form, are acceptable if their hardness does not exceed 30 HRC and they have SMYS grades of 690 MPa (100 ksi), 720 MPa (105 ksi), and 760 MPa (110 ksi). The maximum yield strength for each grade shall be no more than 103 MPa (15ksi) higher than the SMYS. SSC resistance shall be demonstrated by testing each test batch and shall comply with B.1 using the UT test. A.2.2.3.3 Tubulars and tubular components made of Cr-Mo low-alloy steels (UNS G41XX0, formerly AISI 41XX and modifications), if quenched and tempered in the tubular form, are acceptable if the hardness does not exceed 26 HRC. These products should be qualified by SSC testing in accordance with B.1 using the UT test.

Q1: Shall we consider that §A.2.2.3.2 applies only for hardness 26 < hardness = 30HRC and §A.2.2.3.2 applies only for hardness 22 < hardness = 26 HRC?

A1: The requirements in A.2.2.3.2 go beyond just the specification of max hardness of 30 HRC as noted in the clause. Applicable limits for AYS are also indicated. SSC resistance in this case shall be demonstrated by testing as indicated in the clause.

Q2: A.2.2.3.2 doesn’t quote ‘’test batch’’: Shall we consider that SSC results are considered as valid for any similar applications?

A2: A.2.2.3.3 doesn’t quote ‘’test batch’’ and uses only ‘’should’’ : Are SSC results valid for any similar applications if tested once for material meeting A.2.2.3.3 requirements?
If requirements are met in accordance to the stricter criteria applicable to materials of higher hardness (and additional yield strength requirements) than the ones applied in A.2.2.3.3, then those materials will also be considered acceptable for the lesser material condition (i.e. lower hardness). As noted in the clause, the word should implies a recommendation rather than a strict requirement as long as the rest of the requirements in Clause A.2 (and all-inclusive sub-clauses as applicable) are satisfied.

Q3: Are any grade UNS G41XX with hardness = 22 HRC if Q&T in the tubular form, acceptable without additional testing as soon long as it meet NACE MR0175 chemical composition requirements (mainly S = 0.025 %….) ?

A3: As noted in Clause A.2.1.1 (second paragraph) “Carbon and low-alloy steels, products and components that comply with A.2 are, with stated exceptions, qualified in accordance with this part of ISO 15156 without further SSC testing. Nevertheless, any SSC testing that forms part of a materials manufacturing specification shall be carried out successfully and the results reported. “Therefore, tubular materials with hardness <= 22 HRC that meet general and specific requirements in Clause A.2 (and all-inclusive sub-clauses as applicable) are acceptable without further testing. Please also note that chemical composition is not the only requirement that needs to be met. As noted in Clause A.2.1.1 – third paragraph, “The majority of steels that comply with the general requirements of A.2 are not individually listed; however, for convenience, some examples of such steels are listed in Table A.2, Table A.3 and Table A.4.” Also, NACE MR0175-2 = ISO 15156-2 ed 2015 7.2.1.4 SSC regions 1, 2 and 3. Documented field experience may also be used as the basis for material selection for a specific sour-service application; see ANSI/NACE MR0175/ISO 15156-1.

Q4: Is there an official & recognized list associated to NACE MR0175-2 = ISO 15156- 2 ed 2015 for material qualified upon field experience?

A4: There is no official record that tracked and documented field experience.

 

This question is in relation to NACE MR0175/ISO 15156-2/A.2.2.3

Reference MP inquiry #2018-02

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