In short: 30Cr13 (old designation 3Cr13) is the GB high-carbon martensitic stainless steel — the direct Chinese counterpart of AISI 420, equivalent to EN 1.4028 (X30Cr13) and JIS SUS420J2. It is a 12–14% chromium alloy with ~0.30% carbon that quench-hardens to 48–53 HRC. Its crystal structure after quenching is BCT martensite (α′); it is permanently magnetic and derives all its strength from the austenitize → quench → temper cycle. Note the GB family logic: 410 = GB 12Cr13 and 420 = GB 20Cr13 sit at lower carbon; 30Cr13 is on the high-carbon side of 420. If you are buying to a GB datasheet and need an international match, 420 is the grade to specify; step up to 440C for maximum hardness or down to 410 for better toughness and corrosion resistance.
What 30Cr13 (3Cr13) Stainless Steel Is
30Cr13 is a GB-standard high-carbon martensitic stainless steel — the grade most Chinese mills and buyers reach for when they need a hardenable, cutlery-class stainless. In the older GB naming it is written 3Cr13; under GB/T 20878-2007 the prefix digits ×10 denote carbon, so "30Cr13" reads as ~0.30% C with ~13% Cr.[1]
The single most useful fact for international procurement: 30Cr13 is the GB equivalent of AISI 420. It maps to EN 1.4028 (X30Cr13) and JIS SUS420J2, with the GB composition limits running C 0.26–0.35% and Cr 12–14%.[1][2] If you search a GB datasheet and a supplier quotes "420" or "1.4028", they are offering the same high-carbon 13% Cr martensitic steel.
Within the GB 13Cr martensitic family, carbon is the dividing line. 410 = GB 12Cr13 and 420 = GB 20Cr13 carry less carbon; 30Cr13 sits on the high-carbon side of 420, and [40Cr13](/en/materials/stainless-steel/4cr13) higher still. More carbon means harder martensite and a finer edge — at the cost of more chromium-carbide formation and slightly reduced corrosion resistance.[3]
Chemical Composition
Composition limits for 30Cr13 per GB/T 1220 / GB/T 20878. Carbon — the critical hardening element — is what differentiates 30Cr13 from the lower-carbon 410 (12Cr13) and 420 (20Cr13): it raises the tetragonality of the hardened martensite and the peak hardness achievable.[1]
| Element | Symbol | Content (wt%) | Role |
|---|---|---|---|
| Carbon | C | 0.26–0.35 | The key hardening element at ~0.30% — higher than 410/420; increases BCT tetragonality and peak HRC |
| Chromium | Cr | 12–14 | Forms the passive film; minimum for stainlessness — partially consumed by carbides |
| Silicon | Si | ≤ 1 | Deoxidiser; assists oxidation resistance |
| Manganese | Mn | ≤ 1 | Deoxidiser; forms MnS inclusions (pit-initiation sites) |
| Nickel | Ni | ≤ 0.6 | Trace only (≤0.60%) |
| Phosphorus | P | ≤ 0.035 | Residual impurity, held low |
| Sulfur | S | ≤ 0.03 | Residual; MnS inclusions are pit-initiation sites |
| Iron | Fe | Balance | Base metal |
Per GB/T 1220 / GB/T 20878 30Cr13. Cross-referenced against EN X30Cr13 / 1.4028.[1][2]
Crystal Structure: BCT Martensite from Quench Hardening
Stainless steel is an alloy — a solid solution of elements in iron — so it has no molecular formula. The correct description is by crystal structure.
30Cr13 follows the classic martensitic transformation pathway, and its ~0.30% carbon produces a high BCT tetragonality and therefore high hardness. On austenitising and quenching, the austenite transforms displacively into BCT martensite (α′) — a body-centred lattice distorted along one axis by trapped interstitial carbon atoms. More carbon → more distortion → harder martensite, which is why 30Cr13 out-hardens 410.[3]
The as-quenched 30Cr13 is very hard but brittle, with retained austenite alongside the martensite. Tempering at low temperature converts retained austenite and relieves stresses — maintaining high hardness while reducing brittleness. The BCT lattice is ferromagnetic throughout all heat-treatment states. Studies on the equivalent AISI 420 confirm that austenitising followed by oil quenching yields a martensite + retained austenite + chromium-carbide microstructure, with tempering adjusting carbide size and distribution.[3]
Corrosion Resistance: Good When Hardened and Polished
30Cr13 is moderately corrosion resistant in mild atmospheres, fresh water, and dilute acids when in the hardened and polished condition. Its resistance is lower than 410 and substantially lower than austenitic 304 or 316, because the higher carbon intensifies two degradation mechanisms.[4]
Vulnerability 1 — Carbide precipitation and Cr depletion. Research on the equivalent tempered type 420 stainless steel shows that chromium-rich carbides (Cr₂₃C₆, Cr₇C₃) precipitate during tempering. The matrix chromium concentration falls: at 550 °C tempering, the Cr in the matrix drops to ~10.5% — below the threshold for a continuous passive film — causing intergranular corrosion. At 700 °C tempering, localised corrosion occurs at carbide-adjacent Cr-depletion zones, initiating pitting.[4]
Vulnerability 2 — High carbon, less free chromium. Even at the higher end of the Cr range (14%), the effective chromium available for passivation is reduced by carbide formation. With ~0.30% C, 30Cr13 is less corrosion resistant than the lower-carbon 410 despite a comparable chromium range — carbon, not chromium, is the limiting factor.
Best corrosion performance from 30Cr13 is achieved in the hardened (low-temperature temper), ground/polished, and passivated condition — this keeps Cr in solid solution and maximises passive-film integrity.[4]
MnS inclusions from residual sulfur act as pit-initiation sites, documented across stainless grades.[5]
Mechanical & Physical Properties
30Cr13 offers two distinct property profiles depending on heat treatment — the defining advantage of hardenable martensitic grades. In the annealed condition it is soft and machinable; quenched and tempered, hardness in HRC becomes the primary metric. GB/T 1220 sets the quench-and-tempered minimum strengths for hot-rolled bar.[1]
| Hardness | ≤235 HBW |
| Magnetic response | Magnetic |
| Tensile strength (MPa) | ≥735 |
| Yield strength (MPa) | ≥540 |
| Elongation (%) | ≥12 |
| Hardness | 48–53 HRC |
| Density (g/cm³) | 7.75 |
| Magnetic response | Magnetic |
| Temper / condition | Hot-rolled bar, quenched and tempered (GB/T 1220) |
The 48–53 HRC achievable after quench and temper is the defining property of 30Cr13 in cutlery, surgical blades and fine tooling — noticeably harder than 410. The annealed bar is held to ≤235 HBW for machining and forming, then hardened to service condition. GB/T 1220 also specifies the Q&T minimum tensile, yield and elongation for hot-rolled bar; those exact values are shown in the table above.[1]
Studies comparing AISI 410 and 420 — the lower- and matching-carbon equivalents of 30Cr13 — confirm that the higher-carbon grade shows a more complex martensitic matrix with chromium-carbide precipitates that strongly affect both hardness stability and localised-corrosion susceptibility after tempering.[3]
Key Characteristics
- The GB equivalent of AISI 420. Maps to EN 1.4028 (X30Cr13) and JIS SUS420J2 — the grade to specify when a GB 30Cr13 datasheet meets an international spec.
- Heat-treatable to 48–53 HRC. A cutlery-class hardness range — harder than 410, softer than the bearing-grade 440C.
- Mirror-polishable. The martensitic structure with fine carbides takes a high-lustre polish, valued in surgical and dental instruments.
- Permanently magnetic. The BCT lattice is ferromagnetic through all heat-treatment states.
- Moderate corrosion resistance. Adequate for mild atmospheres, fresh water and food contact when hardened and polished — inferior to austenitic grades in chloride environments.
- Poor weldability. The high carbon makes the heat-affected zone very hard and brittle; pre-heat and post-weld heat treatment are required.
How 30Cr13 Is Made
Production follows the standard martensitic route — EAF melting, AOD decarburisation, hot and cold rolling, annealing, pickling — with tight AOD control to land carbon precisely in the 0.26–0.35% window (above 420/20Cr13, below 40Cr13). For service as a cutting or precision-tool part, the critical step is the hardening cycle.
Heat treatment route (as for the equivalent 420): preheat → austenitise (~980–1065 °C) → quench in air or oil → temper immediately at low temperature for maximum hardness, or higher for improved toughness, avoiding the embrittlement range. The annealed-then-hardened sequence is what gives the grade its dual property profile.[3]
30Cr13 vs 420 vs 440C — GB Names and International Matches
All three are martensitic and hardenable. The key insight is the GB↔international mapping: 30Cr13 is essentially AISI 420, while 410 (12Cr13) sits lower in carbon and 440C higher. Choose on whether you need a finer edge, general service, or maximum bearing-grade hardness.
Applications by Industry
30Cr13's combination of high hardness and moderate corrosion resistance makes it a workhorse for sharp-edge and wear-critical components across Chinese manufacturing — the same role 420 plays internationally.[1]
Knife Blades and Cutlery
Kitchen and utility knife blades, scissors, and consumer cutlery — a mainstay GB grade for mass-market blades. The 48–53 HRC hardness provides edge retention with the corrosion resistance stainless demands.[1]
Surgical and Dental Instruments
Scalpels, scissors, forceps and dental probes. 30Cr13 hardens sharply and survives repeated steam-sterilisation cycles while holding a fine edge; the mirror-polish capability matters for instruments used in sterile environments.[1]
Springs and Wear Parts
Springs and wear components in service below ~300 °C, where the hardened martensitic structure resists abrasion. The quench-and-tempered Q&T condition (tensile ≥735 MPa, yield ≥540 MPa per GB/T 1220) supports loaded spring and wear duty.[1]
Shafts, Valve Seats and Fasteners
Shafts, valve seats, and fasteners that need more surface hardness than 410 can deliver. The extra carbon over 410/12Cr13 meaningfully extends service life in mildly erosive or abrasive duty.
Forms & Finishes
Common product forms:Bar (round / flat)PlateSheetCoilWire
Surface finishes:AnnealedNo.4PolishedHardened + ground
For hardened blade and instrument applications, the polished or near-mirror finish applied before hardening is the functional surface — improving both edge quality and corrosion resistance. Bar and wire are the dominant forms supplied to cutlery and spring makers.
References
- 30Cr13 (3Cr13) Stainless Steel — Composition, Properties, Equivalent. theworldmaterial.com (datasheet citing GB/T 1220, GB/T 3280; gives GB Q&T mechanical values and AISI 420 / EN 1.4028 / SUS420J2 equivalents). theworldmaterial.com/30cr13-3cr13-stainless-steel/
- X30Cr13 / 1.4028 — Chemical composition, equivalents. steelnumber.com (European steel database; title confirms X30Cr13 / 1.4028 and lists "3Cr13" among world equivalents). steelnumber.com/en/steel_composition_eu.php?name_id=82
- Investigating the structural properties and wear resistance of martensitic stainless steels. (AISI 410 & AISI 420 heat treatment, hardness, microstructure — the matching-carbon equivalent of 30Cr13). Heliyon / PMC11575766, 2024. pmc.ncbi.nlm.nih.gov/articles/PMC11575766/
- Accessing the full spectrum of corrosion behaviour of tempered type 420 stainless steel. (Zhou & Engelberg). Materials and Corrosion, 2021. — applies directly to 30Cr13 (≈ 420). doi.org/10.1002/maco.202112442
- Pitting corrosion characteristics of sintered Type 316L stainless steel: pores and MnS. (Saito et al.). npj Materials Degradation 8, 2024. doi.org/10.1038/s41529-024-00482-6