The stainless that hardens. 4Cr13, SUS420J2, 2Cr13 and 7C27Mo2 strip — C 0.20–0.45%, Cr 12–14%, quenched to 48–55 HRC — built for edges and loaded surfaces that must also resist corrosion.
Martensitic stainless occupies the narrow band between carbon tool steels and austenitic stainless — and that band is exactly where blades, bearings and valves live. It is not the most corrosion-resistant stainless, nor the hardest steel, but it is the only family that delivers both at once.
Carbon tool steel hardens higher and costs less, but rusts in ambient humidity. Martensitic stainless holds 48–55 HRC while surviving washdown, steam and body fluids — the reason surgical blades are not made from SK5.
Choose martensitic when the part sees moisture or sterilization.304 and 316 resist corrosion better but cannot be quench-hardened — annealed hardness stays near 200 HB. Martensitic 4Cr13 triples that to 48–53 HRC, making it the only stainless choice for a cutting edge.
Choose martensitic when the part needs a hard edge or wear surface.17-4PH offers higher strength and toughness but at a significant premium and with more complex heat treatment. 4Cr13 / SUS420J2 delivers the hardness most blade and bearing applications need at a lower material cost.
Choose 4Cr13 for cost-sensitive edge and wear parts.Chemistry ranges below are typical per the governing standard. Actual heat chemistry and mechanicals are confirmed on the Mill Test Certificate (MTC) for every coil.
| Grade | Standard | C (%) | Cr (%) | Hardness (HRC, quenched) | Primary use |
|---|---|---|---|---|---|
| 4Cr13 | GB/T 1220 | 0.36 – 0.45 | 12.0 – 14.0 | 48 – 53 | Surgical blades, industrial knives, bearing races |
| SUS420J2 | JIS G4304 | 0.26 – 0.40 | 12.0 – 14.0 | 48 – 53 | Razor blades, cutlery, medical instruments |
| 2Cr13 | GB/T 1220 | 0.16 – 0.25 | 12.0 – 14.0 | 40 – 45 | Valve stems, pump shafts, fasteners |
| 7C27Mo2 | Uddeholm / SIS | ~0.45 – 0.55 | ~13.0 – 15.0 | 52 – 56 | Premium knives, high-wear blade edges |
| SUS301 (austenitic, work-hardening) | JIS G4304 | ≤ 0.15 | 16.0 – 18.0 | n/a (work-hardened) | Spring clips, connectors, fatigue-loaded strips |
Chemistry typical per GB/T 1220 / JIS G4304 / applicable standard. 7C27Mo2 values are indicative per producer datasheet — confirm on MTC. SUS301 is included in our stainless range per the stocked product line; it is austenitic, not martensitic, and hardens by cold work rather than quenching.
The two most commonly ordered martensitic grades. 4Cr13 is the higher-carbon blade grade; 2Cr13 is the lower-carbon structural grade.
| Element | 4Cr13 (%) | 2Cr13 (%) | Role |
|---|---|---|---|
| Carbon (C) | 0.36 – 0.45 | 0.16 – 0.25 | Drives hardenability and peak hardness |
| Chromium (Cr) | 12.0 – 14.0 | 12.0 – 14.0 | Provides corrosion resistance and carbide formation |
| Manganese (Mn) | ≤ 1.00 | ≤ 1.00 | Deoxidizer, mild hardenability boost |
| Silicon (Si) | ≤ 1.00 | ≤ 1.00 | Deoxidizer |
| Phosphorus (P) | ≤ 0.035 | ≤ 0.035 | Residual — controlled for toughness |
| Sulfur (S) | ≤ 0.030 | ≤ 0.030 | Residual — controlled for edge quality |
| Nickel (Ni) | ≤ 0.60 | ≤ 0.60 | Residual / optional toughness addition |
Reference: GB/T 1220 (Stainless steel bars). Strip chemistry follows the same grade specification. All values typical per standard — actual heat composition confirmed on MTC. For SUS420J2, refer to JIS G4304; chemistry is broadly comparable with C 0.26–0.40%.
4Cr13 / SUS420J2 strip, 0.10–0.40 mm thick, slit to 6–25 mm widths. Blanked or etched in the soft state, then quenched to 50–54 HRC and passivated for corrosion resistance and biocompatibility per ISO 7153-1.
Thin-gauge SUS420J2 or 4Cr13 takes a sharp, durable edge without the brittleness of higher-alloy knife steels. Consistent carbon across the coil keeps the quench result repeatable at high volume.
7C27Mo2 or 4Cr13 for packaging, textile and food-processing blades where the edge sees abrasion plus washdown. Higher molybdenum in 7C27Mo2 improves edge retention in premium grades.
4Cr13 strip formed into thin-section bearing races, then through-hardened. The chromium gives corrosion resistance in humid or lightly corrosive environments where standard bearing steel would pit.
2Cr13 is the workhorse for valve stems, seats and pump shafts — lower carbon means better toughness and machinability, with enough hardness for wear resistance in fluid-handling equipment.
SUS301 austenitic strip work-hardens to high strength in the rolling mill, making it the standard for electrical contacts, spring clips and fatigue-loaded flat springs in corrosive environments.
Multi-pass rolling to your gauge — 0.10 mm for surgical blade stock up to 3.0 mm for bearing and valve strip — with controlled thickness tolerance and surface finish.
Full soft annealing to a controlled hardness band so the strip blanks cleanly. The part is quenched and tempered by you after forming — we document the starting hardness on the MTC.
Slitting to 6 mm and above for blade and progressive-die coils, with managed burr and camber. Width tolerance confirmed at quoting and checked before dispatch.
For customers who want finished-property strip, we supply quenched-and-tempered coil to a specified hardness band — ideal for spring and wear parts that skip in-house heat treatment.
These grade families share material, processing or application territory with the topic on this page.
301 / 304 / 316 grades with excellent corrosion resistance and formability for springs, medical and food parts.
SK5 / SK7 / T8A / T10A grades with wear resistance and edge hardness for cutting tools.
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