Austenitic, work-hardening stainless that reaches 1500 MPa tensile in the rolling mill — SUS301, 12Cr17Ni7 and S30100 strip for springs, clock springs, electronic connectors and fatigue-loaded flat springs. No quench needed: the strength is built in by cold work.
SUS301 occupies a different metallurgical corner from the martensitic stainlesses. It cannot be hardened by heat treatment — but it hardens dramatically under cold rolling, and it keeps the corrosion resistance and formability of an austenitic steel. That combination is exactly what springs and connectors demand.
4Cr13 hardens by quenching to 48–53 HRC and takes a sharp edge, but its corrosion resistance is lower and it is magnetic. SUS301 hardens by cold work to 1500 MPa tensile, retains better corrosion resistance, and is the standard for springs and connectors rather than cutting edges.
Choose SUS301 for springs and connectors; choose 4Cr13 for blades and wear surfaces.SUS304 (18–8) has better corrosion resistance thanks to higher nickel (8–10.5%), but its lower carbon and stable austenite mean it work-hardens more slowly. SUS301's lower nickel (6–8%) makes it transform more readily under cold work, reaching higher strength at a lower material cost — the reason spring designers specify 301 over 304.
Choose SUS301 when maximum cold-worked strength matters more than peak corrosion resistance.Carbon spring steel reaches higher hardness and costs less, but rusts in ambient humidity and needs coating or oiling. SUS301 delivers spring-level strength with stainless corrosion resistance — the choice for springs exposed to moisture, salt spray or body contact where carbon steel would corrode.
Choose SUS301 when the spring must survive corrosive or uncoated service.SUS301, 12Cr17Ni7 and S30100 are the same alloy under Japanese, Chinese and American standards. The table below shows the correspondence and the temper range each is stocked in.
| Grade | Standard | UNS | Approx. equivalent | Primary use |
|---|---|---|---|---|
| SUS301 | JIS G4304 / G4313 | S30100 | 12Cr17Ni7 · AISI 301 · EN 1.4310 | Springs, connectors, clock springs, flat springs |
| 12Cr17Ni7 | GB/T 1220 | S30100 | SUS301 · AISI 301 | Spring clips, electronic contacts, stampings |
| S30100 | ASTM A666 / A240 | S30100 | SUS301 · 12Cr17Ni7 | Precision strip, aerospace springs, fatigue parts |
Equivalents are approximate — chemistry and mechanical limits vary slightly between standards. Final grade selection should follow your drawing and the governing specification. All values confirmed on the Mill Test Certificate per heat.
The three grade names share the same chemistry window. The low nickel (6–8%) relative to SUS304 is deliberate: it makes the austenite less stable, so cold rolling triggers martensite transformation and drives the work-hardening response that defines this grade.
| Element | SUS301 / 12Cr17Ni7 / S30100 (%) | Role |
|---|---|---|
| Carbon (C) | ≤ 0.15 | Strengthens austenite; higher C increases work-hardening rate |
| Silicon (Si) | ≤ 1.00 | Deoxidizer; mild solid-solution strengthening |
| Manganese (Mn) | ≤ 2.00 | Stabilizes austenite; deoxidizer |
| Phosphorus (P) | ≤ 0.045 | Residual — controlled for toughness and fatigue |
| Sulfur (S) | ≤ 0.030 | Residual — controlled for surface quality and edge integrity |
| Chromium (Cr) | 16.00 – 18.00 | Provides corrosion resistance via passive oxide film |
| Nickel (Ni) | 6.00 – 8.00 | Stabilizes austenite; lower than 304 to promote strain-induced martensite |
Reference: JIS G4304 (stainless steel plates), JIS G4313 (spring-grade stainless strip), GB/T 1220, ASTM A666. Actual heat chemistry confirmed on MTC. Iron is the balance.
SUS301 is ordered by temper, not by a single strength number. Each temper represents a different level of cold reduction, and the tensile strength climbs accordingly. The temper you choose depends on the spring force you need and the amount of forming the part must survive.
| Temper | Tensile (MPa, min) | Yield (MPa, min) | Elongation (%, min) | Hardness (HV, max) | Typical application |
|---|---|---|---|---|---|
| Annealed (O) | ≤ 735 | ≤ 205 | ≥ 40 | ≤ 200 | Deep drawing, severe forming, then work-hardened in-process |
| 1/4 Hard | ≥ 860 | ≥ 510 | ≥ 25 | ≤ 260 | Moderate forming, light springs |
| 1/2 Hard | ≥ 1030 | ≥ 760 | ≥ 15 | ≤ 310 | General springs, clips, connectors |
| 3/4 Hard | ≥ 1210 | ≥ 930 | ≥ 10 | ≤ 360 | High-strength springs, flat spring stock |
| Full Hard (H) | ≥ 1320 | ≥ 1030 | ≥ 5 | ≤ 400 | Heavy springs, clock springs, fatigue-loaded parts |
| Extra Hard (EH) | ≥ 1450 | — | ≥ 3 | ≤ 460 | Maximum-strength springs, precision contacts |
| Super Hard (SH) | ≥ 1500 | — | — | ≤ 500 | Ultra-high-strength spring applications, specialty electronics |
Values typical per JIS G4313 and ASTM A666 for spring-grade stainless strip. Actual tensile, yield and hardness are documented on the MTC per coil. Elongation decreases as temper increases — select the softest temper that meets your spring force requirement to preserve formability.
SUS301 1/2H to 3/4H strip, 0.10–0.40 mm, slit to 3–20 mm widths. Stamped into pin contacts, socket springs and grounding clips where high contact force, fatigue resistance and corrosion protection are required in a compact footprint.
Full hard or extra hard SUS301, 0.08–0.30 mm, wound into spiral power springs for timers, retractors and automotive steering wheel clock springs. The high tensile-to-thickness ratio stores more energy per unit volume than carbon steel alternatives.
3/4H to H temper strip formed into flat springs, retaining clips, snap fasteners and battery contacts. The work-hardened structure delivers consistent spring force over millions of cycles without the need for post-forming heat treatment.
SUS301 H temper for seatbelt retractor springs and sensor springs where corrosion resistance in the vehicle cabin environment and reliable cyclic performance are non-negotiable. Full MTC traceability per coil for safety-component documentation.
3/4H to EH SUS301 for surgical instrument springs, endoscopic clips and implantable-adjacent components. The austenitic structure and chromium passivation resist body fluids and sterilization cycles; passivation available on request.
S30100 to ASTM A666 for aerospace spring components and precision instrument elements where the combination of high strength, low magnetic permeability (in lower tempers) and corrosion resistance is specified by the design engineer.
Multi-pass rolling to your specified temper — from annealed for forming through super hard for maximum spring force. Tensile and hardness verified per coil and documented on the MTC.
Slitting to 5 mm and above for connector and progressive-die coils, with managed burr and camber. Width tolerance confirmed at quoting and checked before dispatch.
Round-edge, slit-edge or deburred edge options to match your stamping or winding operation. Edge condition affects spring fatigue life — we match it to your application.
2B, BA or polished surfaces as standard. Passivation treatment available for medical and aerospace grades to maximize corrosion resistance and remove free iron from the surface.
The quench-hardening family — 4Cr13, SUS420J2, 2Cr13 — for blades, bearings and valves. Compare the hardening mechanism and choose the right stainless family for your part.
View martensitic stainless strip →Carbon and alloy strip in the full cold-rolled range — from deep-drawing DC04 through high-carbon SAE1078 for spring and tool applications.
View cold-rolled strip →Spheroidized, tight-tolerance carbon strip for net-shape fine blanking of automotive and mechanical components — the process partner to our spring and stainless ranges.
View fine blanking steel →How SUS301 compares to carbon spring steels (SK5, SAE1078) and alloy spring steels (50CrV4) across strength, fatigue and corrosion — a guide for material selection.
Read the guide →Every coil ships with an MTC documenting chemistry, tensile, hardness and processing history. This guide explains what each field means and what to check before accepting material.
Read the guide →Application page covering spring steel strip for automotive clutch disc springs — including temper selection, fatigue life considerations and processing requirements.
View application →Include thickness × width, temper, quantity and destination port. Our engineers reply within one working day.