SUS410 Stainless Steel: Martensitic Grade for Mechanical Parts

What Is SUS410 Stainless Steel?

SUS410 is the JIS designation for a 12% chromium martensitic stainless steel, equivalent to AISI 410, UNS S41000, EN 1.4006 (X12Cr13) and the Chinese grade 12Cr13. It belongs to the martensitic family: the material is magnetic, has a body-centred cubic structure, and can be hardened significantly by quenching and tempering. In the annealed condition SUS410 is relatively soft and easy to machine; after heat treatment its hardness and strength exceed what most austenitic grades can offer, which makes it a common choice for shafts, fasteners, valve components, pump parts, cutlery and general mechanical parts.

Chemical Composition and International Equivalents

The table below lists the guaranteed composition ranges for SUS410 per JIS G4303 and for the equivalent UNS S41000 plate and sheet per ASTM A240. Chromium in the 11.5-13.5% range provides moderate corrosion resistance in mild atmospheric and freshwater environments; the low carbon content of the ASTM plate version keeps the annealed structure soft enough for forming and machining.

Element	SUS410 (JIS G4303)	UNS S41000 (ASTM A240)
Carbon (C)	≤ 0.15%	≤ 0.08%
Silicon (Si)	≤ 1.00%	≤ 1.00%
Manganese (Mn)	≤ 1.00%	≤ 1.00%
Phosphorus (P)	≤ 0.040%	≤ 0.040%
Sulfur (S)	≤ 0.030%	≤ 0.030%
Chromium (Cr)	11.50-13.50%	11.50-13.50%

Common international equivalents: JIS SUS410, AISI 410, UNS S41000, EN 1.4006, GB 12Cr13. When ordering, always confirm which product form and standard apply, because bar, plate and wire specifications set slightly different carbon limits.

Mechanical Properties and Heat Treatment

SUS410 is supplied either in the annealed condition or in the quenched and tempered condition. Annealed material offers the best machinability, while quenched and tempered material provides high hardness and wear resistance. Typical guaranteed values are shown below.

Property	Annealed	Quenched and Tempered
Tensile strength Rm	≥ 485 MPa (ASTM A240); ≥ 540 MPa (JIS G4303)	700-900 MPa (typical)
0.2% proof stress Rp0.2	≥ 205 MPa (ASTM A240)	≥ 550 MPa (typical)
Elongation	≥ 20% (ASTM A240)	12-18% (typical)
Hardness	≤ 200 HBW (JIS G4303); ≤ 217 HBW (ASTM A240)	Rc 35-42 (typical)

A typical hardening cycle is austenitising at 950-1000 °C followed by oil or air quenching, then tempering at 650-750 °C for a tough medium-hard part or at 550-650 °C for higher hardness. Full annealing at 815-900 °C with slow furnace cooling restores the soft condition for further machining. Because every heat responds slightly differently, final properties should be verified on the actual production lot.

Typical Applications

SUS410 is widely used for mechanical parts where moderate corrosion resistance and high hardness are both required: shafts and spindles, valves and valve stems, pump components, fasteners and studs, turbine blades, cutlery and kitchen tools, and general wear parts such as guides and bushes. In appliances it appears as internal structural parts that never see aggressive chemicals.

Limitations and Selection Considerations

Three limitations should be checked before selecting SUS410. First, corrosion resistance is far below that of SUS304 or SUS316: SUS410 will rust in marine, humid or chloride-containing environments and should be avoided there unless painted or otherwise protected. Second, weldability is limited: the martensitic structure hardens on cooling, so preheating and post-weld tempering are normally required to avoid cracking. Third, maximum continuous service temperature is roughly 650 °C in air, above which scaling and softening become significant. If higher corrosion resistance or easier welding is needed, consider austenitic or duplex alternatives even if they cost more.

FAQ

Can SUS410 be hardened by heat treatment?

Yes. Austenitising at 950-1000 °C, quenching in oil or air, and tempering at the selected temperature raises hardness to about Rc 35-42 while tensile strength typically reaches 700-900 MPa. This is the main advantage of SUS410 over austenitic grades.

What is the difference between SUS410 and SUS304?

SUS410 is a magnetic, hardenable martensitic grade with 12% chromium and no nickel. SUS304 is a non-magnetic austenitic grade with 18% chromium and 8% nickel, offering far better corrosion resistance and formability but lower hardness and no response to hardening heat treatment.

Is SUS410 corrosion resistant?

It offers moderate resistance in mild atmospheric, freshwater and light industrial environments. It is not suitable for seawater, strong acids or prolonged humid or chloride exposure without protective coating.

Can SUS410 be welded?

Yes, but with precautions. Preheat to roughly 150-300 °C, use low-hydrogen filler, and temper after welding to restore toughness and relieve hardening. Where welding is frequent, a lower-carbon or austenitic grade is often easier to work with.

What is the difference between SUS410 and SUS420J1?

SUS420J1 has a higher carbon content of 0.16-0.25% and therefore reaches higher hardness after heat treatment, at the cost of lower ductility and weldability. SUS410 is preferred when toughness and machinability matter more than maximum hardness.

Is SUS410 magnetic?

Yes. Like all martensitic and ferritic stainless steels, SUS410 is magnetic in every condition because of its ferritic or martensitic crystal structure.