What is NACE MR0175 Seamless Steel Pipe Material

NACE MR0175 is not a specific seamless steel pipe material, but rather a standard developed by the National Association of Corrosion Engineers (NACE), officially titled "Sulfide Stress Crack Resistance Metallic Materials for Oilfield Equipment." In 2003, this standard was revised and renamed NACE MR0175/ISO 15156 "Oil and Gas Industry — Materials for H2S-Containing Environments in Oil and Gas Production." The following is an analysis of seamless steel pipe materials conforming to the NACE MR0175/ISO 15156 standard:

First, what are the chemical composition requirements for NACE MR0175 seamless steel pipe?

1) Sulfur Content: For seamless products, the S content is no more than 0.01%; for rolled products (steel plate), the S content is no more than 0.003%; for forged products, the S content is less than 0.025%. Reducing the sulfur content in steel increases its resistance to sulfide stress corrosion.

2) Phosphorus content: Generally, P ≤ 0.020%. Excessive phosphorus content reduces the toughness and corrosion resistance of steel. Controlling its content helps improve the performance of steel pipes in sulfur-containing environments.

3) Carbon content: Typically, C ≤ 0.10%. Excessive carbon content increases the hardness of steel, reduces toughness, and is detrimental to resistance to sulfide stress corrosion cracking. Lower carbon content improves the corrosion resistance of steel.

4) Nickel content: In carbon steel and low-alloy steel, the Ni content is less than 1%. Excessive nickel content may increase the steel's susceptibility to sulfide stress corrosion cracking.

Secondly, what are the mechanical property requirements for NACE MR0175 seamless steel pipes?

1) Hardness: The hardness of carbon steel and low-alloy steel should not exceed 22 HRC (Rockwell hardness). Forgings manufactured according to ASTM A105 should have a hardness not exceeding 187 HBW (Brinell hardness); forgings according to ASTM A234 WPB and WPC should have a hardness not exceeding 197 HBW (Brinell hardness); the maximum hardness of the weld zone should not exceed 250 HV (Vickers hardness) or 22 HRC (Rockwell hardness).

2) Strength: Tensile strength and yield strength should be consistent with the requirements of relevant standards for general steel pipes, and must meet the mechanical performance requirements under actual use conditions to ensure that the steel pipe will not fail under pressure and external forces.

Third, what are the heat treatment requirements for NACE MR0175 seamless steel pipes?

1) The base material should be non-free-cutting steel and belong to one of the following heat treatment states: hot-rolled (carbon steel only), annealed, normalized, normalized + tempered, normalized, austenitized, quenched and tempered, austenitized, quenched and tempered.

2) Carbon steel and low-alloy steel, after rolling, cold forging, or other manufacturing processes that result in permanent deformation of the outer fiber layer exceeding 5%, should undergo stress-relieving heat treatment (at a temperature not less than 595℃). However, cold-worked pipeline fittings of ASTM A53 B, ASTM A106 B, API 5L X42, or equivalent grades, with cold deformation not exceeding 15% and a hardness not greater than 197HBW, do not require heat treatment.

Fourth, what are the other requirements for NACE MR0175 seamless steel pipes?

1) Marking: Marking should use low-stress marking (dot marking, corrosion marking, U-shaped marking); if high-stress marking (V-shaped marking) is used, stress-relieving heat treatment at a temperature not less than 595℃ should be performed after marking.

2) Testing: When required by the customer, SSC (sulfide stress cracking test), SOHIC (stress-directed hydrogen cracking test), and SZC soft zone cracking test should be performed. The test methods and evaluation should be carried out in accordance with NACE standards.