MATERIALS · August 25, 2026 · 7 MIN READ

Stainless Steel Grade Equivalents: GB, AISI and JIS Side by Side

06Cr19Ni10, 304 and SUS304 are the same alloy family — 18 % Cr, 8–11 % Ni, carbon 0.08 % max — but GB/T 20878, ASTM A240 and JIS G4303 do not specify identical limits on sulphur, phosphorus and residuals, so a Chinese mill certificate to GB will not always satisfy an ASTM purchaser. The three tables below give the working equivalents and, more importantly, the places where the equivalence breaks.

WHERE THIS APPLIES AT FORGEPRESS CHINA

ForgePress China forges and certifies 304, 304L, 316, 316L, 321 and 410 to GB/T 20878, ASTM A240 or JIS G4303 as the purchase order requires. Capacity: HKM3 hot-die forging line 1,000–5,000 t, part weight 0.1–500 kg, maximum envelope 1,200 × 800 mm, as-forged to ISO 8062 class C with critical dimensions machined to ±0.2 mm, process control to ISO 9001, first article 4–8 weeks from die design release.

KEY NUMBERS

06Cr19Ni10 (GB) = 304 (AISI/ASTM) = SUS304 (JIS); carbon limit 0.08 % in all three.
022Cr17Ni12Mo2 = 316L = SUS316L; carbon 0.03 % max, Mo 2.0–3.0 %.
Austenitic stainless forging window is narrow: 1,150–1,200 °C start, finish above 900 °C.
GB designations were rewritten in GB/T 20878-2007: 0Cr18Ni9 became 06Cr19Ni10.

The three standards and what they actually control

GB/T 20878 is the Chinese designation and composition standard; ASTM A240/A276 covers plate, sheet and bar for pressure and general applications; JIS G4303 covers stainless bars. All three describe the same 18-8 family, but they differ in how much freedom the mill has on residuals and on the balance of nickel.

That matters at the purchasing level, not the engineering level. A part designed around 304 will forge and machine the same whether the mill certificate says 06Cr19Ni10 or 304 — until a pressure-equipment inspector refuses a GB certificate because the specification calls for ASTM. Decide the certificate requirement before the mill order, not after.

Working equivalence table

GB/T 20878	AISI / ASTM	JIS	Typical use in forging
06Cr19Ni10	304	SUS304	General corrosion-resistant forgings, food and dairy
022Cr19Ni10	304L	SUS304L	Welded assemblies, avoids sensitisation
06Cr17Ni12Mo2	316	SUS316	Marine, chemical, chloride exposure
022Cr17Ni12Mo2	316L	SUS316L	Piping components, pharmaceutical
06Cr18Ni11Ti	321	SUS321	Elevated-temperature service, exhaust parts
12Cr13	410	SUS410	Martensitic; wear parts, not corrosion-critical
20Cr13	420	SUS420J1	Cutlery, valve trim, hardenable
10Cr17	430	SUS430	Decorative, low-cost, ferritic

Equivalence means the alloys fall in the same specification family. It does not mean the mill certificates are interchangeable for a purchaser who specified a particular standard.

Where the equivalence breaks

First, nickel balance. GB allows the nickel range at the low end for cost reasons, and a 304 with 8.0 % Ni is materially less corrosion-resistant in chloride than one at 10.5 %. If the application is coastal or chlorinated, specify a minimum nickel content on the purchase order rather than relying on the grade name.

Second, carbon. 304 caps carbon at 0.08 %, 304L at 0.03 %. Substituting 304 for 304L in a welded assembly is the classic sensitisation error: chromium carbide precipitates at the grain boundaries in the heat-affected zone and the material becomes intergranularly corrodible. If the part will be welded, specify L-grade, and specify it as L-grade on the certificate.

Third, sulphur. Free-machining variants (303 / SUS303, and 304 with added S) machine far better but are markedly less corrosion-resistant and are not weldable. A supplier switching to a free-machining grade to hit a price is a real and common substitution — check the certificate, not the label.

Forging stainless: what changes in the process

Stainless is not "steel with chromium". Flow stress at temperature is 50–80 % higher than carbon steel, the forging window is narrower, and the material work-hardens so aggressively that a second blow at low temperature will crack the surface. Start at 1,150–1,200 °C, never finish below 900 °C, and plan for 30–50 % more tonnage than the same geometry in carbon steel.

Tooling wear also rises: abrasive oxide scale on stainless is harder than on carbon steel, and die life typically drops 40–60 %. That is a tooling-cost line item, not a footnote.

Frequently asked questions

Is 06Cr19Ni10 the same as 304?

Same alloy family and the same carbon limit of 0.08 %, but certified to a different standard with different permitted residual levels. For most mechanical applications they are interchangeable; for a purchaser who specified ASTM A240, a GB certificate may not be accepted even though the analysis is close.

Can I substitute 304 for 316?

Only if the service environment has no chlorides and no elevated temperature. 316 adds 2.0–3.0 % molybdenum, which is what provides resistance to pitting in chloride; 304 will pit in seawater and in many chemical streams where 316 survives.

Why did 0Cr18Ni9 become 06Cr19Ni10?

GB/T 20878-2007 moved Chinese stainless designations to a system that states the carbon content to two decimal places, so 0Cr18Ni9 (carbon up to 0.08 %) became 06Cr19Ni10. Both designations appear on older drawings and both refer to the same family.