Ask two suppliers whether AISI 403 and AISI 410 are "the same," and you get two confident, opposite answers. Both are right — it depends entirely on whether you are drawing a bar of steel or a forged component that has to survive twenty years of thermal cycling. This guide settles it the way our metallurgists do on the shop floor: by looking at what actually differs, what does not, and what that means for the part in front of you.
Quick answer
AISI 403 and AISI 410 are both 12% chromium martensitic stainless steels with nearly identical chemistry. The difference is quality discipline: AISI 403 (UNS S40300) is held to tighter residual-element limits and higher cleanliness than AISI 410 (UNS S41000), giving it lower heat-to-heat toughness scatter.
Specify 403 for rotating and safety-critical forgings — turbine blades and discs, critical valve trim, nuclear coolant-pump parts. Use 410 for general valve bodies, non-critical shafts, cutlery and cost-driven wear parts.
Key takeaways
- Same alloy family (11.5–13% Cr, ≤0.15% C, martensitic); 403 is essentially 410 held to a stricter internal specification.
- 403 caps nickel at ≤0.60% (vs 0.75%) and silicon lower, with cleaner steel — cutting toughness scatter roughly 2.5×.
- Typical Q+T strength: 403 ≈ 782 MPa tensile / 653 MPa yield vs 410 ≈ 690 / 485 MPa.
- Corrosion resistance, ~650°C oxidation limit and welding rules are effectively identical — do not pay a 403 premium for those.
- Rule of thumb: if toughness consistency is life-limiting, choose 403; otherwise 410 is the economical, correct choice.
§ 01 Same family, different quality discipline
They are not different alloys — 403 is 410 held to a stricter internal spec
Both grades are low-carbon martensitic stainless steels in the same window: roughly 11.5–13% chromium, carbon capped at 0.15%, hardenable by quench-and-temper. Drop a coupon of each into a corrosion cabinet and you will struggle to tell them apart, because the passive film, the oxidation limit and the temperature ceiling are governed by chromium — and on chromium the two grades are twins.
Where they diverge is in what the specification does not put in the headline. AISI 403 carries tighter limits on residual and tramp elements and is typically melted to a cleaner inclusion rating. The clearest single marker is nickel: 403 caps it at ≤0.60% against 410's ≤0.75%, and silicon is usually held lower too. None of that changes the alloy's identity. What it changes is consistency — and for a forging whose life is set by fatigue, consistency is the whole game. It is exactly this tighter internal spec that we hold across our custom AISI 403 (UNS S40300) forgings.
Metallurgist's note · why residuals decide fatigue life
Peak strength is rarely the limiting factor on a rotating part; the limiting factor is the lowest toughness value anywhere in a production batch, because that is where a fatigue crack starts. Tighter residual control and cleaner steel compress the heat-to-heat scatter in Charpy toughness, letting a designer set a tighter, more confident fatigue margin. That is why turbine OEMs write 403 into blade and disc specs rather than accept 410 to minimum.
§ 02 Composition head-to-head
Chemistry side by side
Read this table for the limits, not just the midpoints. Chromium and carbon overlap almost completely; the meaningful separation is in nickel and silicon, and — beyond the table — in how tightly a competent mill actually holds the residual elements.
| Element | AISI 403 · S40300 | AISI 410 · S41000 |
|---|---|---|
| Chromium (Cr) | 11.5 – 13.0 | 11.5 – 13.5 |
| Carbon (C) | ≤ 0.15 | ≤ 0.15 |
| Nickel (Ni) | ≤ 0.60 | ≤ 0.75 |
| Silicon (Si) | ≤ 0.50 | ≤ 1.00 |
| Manganese (Mn) | ≤ 1.00 | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.040 | ≤ 0.040 |
| Sulfur (S) | ≤ 0.030 | ≤ 0.030 |
Highlighted cells mark where 403's ceiling sits below 410's. The lower Si and Ni limits, with tighter residual control, give 403 its cleaner, more uniform microstructure.
§ 03 Mechanical properties & the scatter story
Where the numbers separate — and which number actually matters
In the standard quenched-and-tempered condition, typical values for 403 run ahead of 410. But the figure that should drive a critical-part decision is one most datasheets never print: toughness scatter across heats. The values below are typical results from our own production testing.
| Property | AISI 403 | AISI 410 |
|---|---|---|
| Tensile strength (typ.) | 782 MPa | 690 MPa |
| Yield strength 0.2% (typ.) | 653 MPa | 485 MPa |
| Hardness (typ.) | 217–237 HBW | ~197 HBW |
| Charpy V-Notch, RT (typ.) | ~102 J | ~80 J |
| Charpy scatter (CV across heats) | ~8% | ~20% |
Values are typical, not spec minimums; both grades exceed ASTM A276 minimums. The scatter row is the decisive one for fatigue-limited components.
Read those four numbers together and the picture is clear: choosing 403 buys strength headroom and — more importantly — predictability. It does not buy a different corrosion or temperature capability. If a salesperson tells you 403 "resists more corrosion" than 410, treat it as a red flag.
§ 04 Where they behave identically
Three things you should not pay a premium for
It is just as important to know where the grades are equal, so you do not over-specify:
- Corrosion resistance. Both rely on the same 11.5–13% Cr passive film, suited to atmospheric, pure-water and dry-steam environments — and both are unsuitable for chloride-bearing or strongly acidic service, where duplex or nickel alloys are required.
- High-temperature oxidation. Both are usable to roughly 650°C for oxidation, with useful strength retained to about 600°C. The ceiling is set by chromium, which is shared.
- Weldability. Both demand the same discipline: preheat above ~10 mm, matching E410/ER410 filler, mandatory post-weld tempering, controlled cooling through the embrittlement range. Neither welds as freely as an austenitic 304.
Shared hazard · the 370–565°C embrittlement zone
Both 403 and 410 suffer tempered-martensite embrittlement if tempered or slow-cooled through roughly 370–565°C. It slashes notch toughness while leaving hardness untouched — so a hardness test will not catch it. It applies equally to both grades and is one of the most common causes of "mystery" brittle failures in 12% Cr forgings.
§ 05 Cost & availability
What the price difference actually buys
410 is the more commonly stocked of the two and usually cheaper. 403 typically carries a modest premium — not because it is a richer alloy, but because reaching its tighter residual limits and cleaner inclusion rating takes more careful melting practice (EAF+LF+VOD, and ESR for the most demanding rotating parts).
Framed correctly, the premium is an insurance payment: you are buying consistency and qualification confidence, not corrosion or temperature performance. On a general valve body that premium is wasted. On a turbine blade root it is the cheapest line item in the whole risk budget. We forge both grades to specification from steel-melting to finished machining — the full material data, size range and certifications for our AISI 403 forged parts are on the product page.
§ 06 The decision matrix
Match the grade to the part, not to habit
Strip away the marketing and the choice comes down to one question: is toughness consistency life-limiting for this component? If yes, 403. If no, 410.
Specify AISI 403 when
Consistency is safety-critical
- Gas or steam turbine blades, discs, impellers and wheels
- Fatigue-limited rotating components at high RPM
- Critical valve trim — stems, seats, spindles in severe service
- Nuclear reactor coolant-pump parts
- Any spec calling out low residuals, delta-ferrite control or ESR melting
AISI 410 is enough when
Standard service, cost matters
- General valve bodies and bonnets in standard service
- Non-critical pump and drive shafts
- Cutlery, surgical and hand-tool blanks
- Wear parts where hardness, not toughness scatter, governs life
- Cost-sensitive volume jobs with generous fatigue margins
A useful default
When a drawing simply says "12% Cr martensitic" and the part rotates or holds pressure in a safety-critical loop, quote it in 403. When it is a general industrial part and the customer is price-sensitive, 410 is the responsible recommendation. A good forging partner tells you when you are over-specifying — and when you are cutting a corner you will regret.
§ 07 Application mapping
Typical grade choice by component
| Component | Typical choice | Why |
|---|---|---|
| Turbine blades & discs | 403 | Fatigue life set by toughness scatter |
| Compressor rotors / impellers | 403 | High-cycle rotating, low defect tolerance |
| Critical valve stems & seats | 403 | Safety-critical, cyclic loading |
| General valve bodies & bonnets | 410 | Standard service, cost-driven |
| Non-critical pump shafts | 410 | Adequate strength, generous margins |
| Cutlery / surgical / wear parts | 410 | Hardness-governed, not toughness-limited |
§ 08 Standards & equivalents
One note that prevents cross-certification headaches
Both grades appear across the major standards, but "equivalent" never means "identical" — Mn and residual allowances shift between systems. Roughly: AISI 403 leans toward the cleaner EN X6Cr13 (1.4000) family and JIS SUS403, while AISI 410 aligns with EN X12Cr13 (1.4006) and JIS SUS410. For any critical order, name your governing standard (usually ASTM or EN) and list the others as "reference only," so a mill test certificate cannot be quietly issued to a looser variant.
§ 09 Key terms
Quick glossary
- Martensitic stainless steel
- A hardenable stainless family (~11.5–18% Cr, higher carbon) that forms hard martensite on quenching. Strong and wear-resistant, but less corrosion-resistant than austenitic grades. 403 and 410 both belong here.
- Residual (tramp) elements
- Unspecified elements — nickel, copper, phosphorus, tin — carried in from scrap. Tighter limits raise cleanliness and cut property scatter. This is the core of the 403-vs-410 difference.
- Charpy V-notch (CVN) toughness
- Energy in joules absorbed by a notched bar in an impact test. Its lowest value and its batch-to-batch scatter drive fatigue-life confidence on rotating parts.
- Quench & temper (Q+T)
- Austenitize, rapidly quench to martensite, then temper to trade a little hardness for toughness. The standard delivery condition for both grades.
§ 10 Frequently asked
AISI 403 vs 410 — quick answers
What is the difference between AISI 403 and AISI 410?
Both are 12% Cr martensitic stainless with nearly identical chemistry. 403 is held to tighter residual limits (Ni ≤0.60% vs 0.75%, lower Si) and higher cleanliness, giving lower toughness scatter — so 403 is used for turbine and safety-critical forgings, 410 for general valve and shaft parts.
Is AISI 403 stronger than AISI 410?
In the quenched-and-tempered condition, typical 403 values run higher — around 782 MPa vs 690 MPa tensile in our production data. But the more decisive difference is consistency: 403 shows far lower heat-to-heat scatter in Charpy toughness.
Can I substitute AISI 410 for AISI 403?
Only if the governing specification allows it. For general valve bodies, non-critical shafts and wear parts, 410 is a sound substitute. For turbine blades and discs, nuclear coolant-pump parts, or any part where the spec calls out low residuals, ferrite control or ESR melting, use 403.
Do AISI 403 and 410 weld the same way?
Yes — same family, same precautions: preheat above ~10 mm thickness, matching E410/ER410 filler, mandatory post-weld tempering, and controlled cooling through the 370–565°C embrittlement range.
Which is more corrosion resistant, 403 or 410?
They are essentially equal. Both depend on the same 11.5–13% Cr passive film and both are limited to atmospheric, pure-water and dry-steam service. Selecting 403 does not improve corrosion resistance.
Is AISI 403 more expensive than AISI 410?
Usually a modest premium that pays for tighter melt control and cleaner steel, not a different alloy — you are buying consistency and qualification confidence. On general parts the premium is wasted; on critical rotating parts it is well spent.
What are the UNS numbers for AISI 403 and AISI 410?
AISI 403 is UNS S40300 (Grade 403); AISI 410 is UNS S41000 (Grade 410). Rough equivalents: 403 ≈ EN X6Cr13 (1.4000) / JIS SUS403; 410 ≈ EN X12Cr13 (1.4006) / JIS SUS410.
§ 11 Sources & standards
References
Standards & authoritative references
- ASTM A276 / A276M — Standard Specification for Stainless Steel Bars and Shapes. astm.org
- ASTM A473 — Standard Specification for Stainless Steel Forgings. ASTM International.
- AZoM — Stainless Steel Grade 403 (UNS S40300), Forging. azom.com
- NACE MR0175 / ISO 15156 — Materials for use in H₂S-containing environments (sour service hardness limits).
- EN 10088-3 — Stainless steels: technical delivery conditions for semi-finished products, bars, rods and sections.
- Jiangsu Liangyi internal production and heat-treatment test data (2000–2026), quoted values are typical results.
Still deciding on grade?
Send us the drawing — we'll recommend 403 or 410 with the data behind it
We forge both grades from steel-melting to finished machining, with EN 10204 3.1 mill test certificates on every shipment (3.2 third-party certificates available on request). Tell us the service conditions and we'll advise where a 403 premium earns its cost — and where 410 is the smarter spec.