Question 1

What is the difference between ASTM A240 and ASME SA-240?

Accepted Answer

ASTM A240 and ASME SA-240 share the same chemical composition and mechanical property limits for stainless steel plate, sheet and strip. ASME SA-240 is the version adopted into the ASME Boiler and Pressure Vessel Code, with additional certification and traceability provisions that code-stamped vessel fabrication requires. A mill qualified to produce plate to A240 is usually also qualified to supply SA-240 material, since the underlying chemistry and testing are identical. Specify SA-240 only when the finished item will carry an ASME code stamp.

Question 2

What is an EN 10204 3.1 vs 3.2 certificate?

Accepted Answer

A 3.1 certificate is validated and issued by the manufacturer's own authorized inspection representative, independent of the production department, and is the certificate most commonly supplied with stainless and nickel-alloy mill products. A 3.2 certificate adds validation by the purchaser's own inspector or an independent third-party inspection body named in the contract, giving an extra layer of verification beyond the mill's internal sign-off. Both certificate types report the same chemical and mechanical test results; the difference is who validates them, not what is tested. Most commercial orders travel with a 3.1 certificate, and 3.2 is reserved for critical or code-mandated projects.

Question 3

What does NACE MR0175 / ISO 15156 require of steel?

Accepted Answer

NACE MR0175 and its identical international version, ISO 15156, set metallurgical and hardness qualification limits for metals used in oil and gas production environments containing wet hydrogen sulfide, known as sour service. For carbon and low-alloy steel this typically means controlling hardness and, for some product forms, confirming resistance to hydrogen-induced cracking. For stainless and nickel alloys it restricts cold work, specifies heat treatment condition, and in some cases limits chloride content, because sour environments can trigger sulfide stress cracking in material that would otherwise be considered corrosion-resistant. A mill certificate referencing NACE MR0175 confirms the heat was produced and tested in the qualified condition for sour service.

Question 4

How do UNS, Werkstoff and JIS numbers cross-reference?

Accepted Answer

The Unified Numbering System is the US designation, for example N08825 for Incoloy 825, while the German Werkstoff number for the same alloy is 2.4858 and the closest Japanese JIS designation references its own compositional table. These systems were developed independently and do not convert by a fixed formula, so cross-reference relies on matching the underlying chemical composition and mechanical property ranges grade by grade. Getting the cross-reference right matters most on international orders, where a European drawing calling out a Werkstoff number and a purchase order calling out a UNS number must resolve to the same material.

Question 5

Which spec covers stainless plate vs pipe vs forgings?

Accepted Answer

Stainless flat products, meaning plate, sheet and strip, are specified to ASTM A240 or ASME SA-240. Stainless pipe is specified separately to ASTM A312, since pipe carries its own dimensional tolerances, hydrostatic test requirements and seam-weld provisions that a flat-product spec does not address. Forged fittings and flanges are covered by yet another standard, ASTM A182, because forging introduces its own grain-flow and mechanical-test requirements. Ordering the correct form-specific standard, not just the correct grade, is what a mill certificate is checked against at receiving inspection.

Question 6

What is ASTM A262 intergranular-corrosion testing?

Accepted Answer

ASTM A262 defines a set of standardized test practices used to detect susceptibility to intergranular corrosion in austenitic stainless steel, most often the result of chromium carbide precipitation at grain boundaries after welding or improper heat treatment, known as sensitization. The practices use different combinations of etching, electrochemical reactivation or boiling acid exposure depending on the grade and the suspected form of attack. Fabricators welding 304 or 316 for service that will see 425–815°C, or testing low-carbon L grades to confirm a weld did not sensitize, specify an A262 practice as an acceptance test. A passing result confirms the grain boundaries remain free of the continuous carbide network that triggers intergranular attack in service.

Standards

Stainless steel standards: ASTM A240 and ASME SA-240

Pressure-vessel plate standards: A516, A20, A387

Nickel alloy standards: B409, B424, B443, B575

Pipe, fitting and flange standards

Certification standards: EN 10204, NACE MR0175

UNS, Werkstoff and JIS cross-reference

Browse standards

Frequently asked

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