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Why the 420 family includes several EN grades
1.4021, 1.4028 and 1.4034, commonly associated with 420, are distinct EN grades. Their steel names X20Cr13, X30Cr13 and X46Cr13 indicate different carbon levels. All are martensitic stainless steels capable of hardening through suitable heat treatment, without representing identical treatment outcomes or mechanical balances.
A shaft combines a load-bearing body with bearing surfaces, while a thin cutting edge transfers force into a small contact region. Carbon differences affect the hardness–toughness balance developed through heat treatment for these functions. The distinct EN identities reflect this manufacturing difference.
What increasing carbon changes
Carbon affects attainable hardness and wear behaviour after suitable hardening. A higher-carbon option can become relevant where retention of edge shape matters. Increasing hardness does not mean that every mechanical property improves in the same direction, however. Impact behaviour, section and final heat treatment are other parts of the picture.
1.4021 / X20Cr13 is the lower-carbon option; X30Cr13 and X46Cr13 identify the two higher-carbon grades. The increase can matter at edges and contact surfaces involving higher hardness targets. All three can follow a route of machining annealed geometry before developing final properties by heat treatment.
| EN grade | Steel name | Key distinction |
|---|---|---|
| 1.4021 | X20Cr13 | Lower carbon among the three options |
| 1.4028 | X30Cr13 | Higher carbon than 1.4021 |
| 1.4034 | X46Cr13 | Higher carbon among the three options |
Annealed stock and final heat treatment
Cutting and machining annealed material involve different conditions from processing hardened stock. Initial manufacture may establish the rough geometry before later heat treatment develops final properties. Hardening and tempering are stages through which the hardness–toughness relationship is adjusted. The grade name alone does not identify the mechanical condition of the finished component.
Heat treatment can produce dimensional changes and surface scale. Allowance is therefore left on shafts requiring finish grinding or on precision cutting surfaces. Final grinding removes it to establish both dimensions and the functional surface. The allowance provides room for that later operation.
Shafts, mechanical components and cutting surfaces
1.4021 is among the options considered for components combining mechanical loading with a need for corrosion resistance. Higher-carbon variants can occupy a different role in cutting and wearing surfaces. Edge geometry, contact area and loading influence how material hardness translates into component behaviour.
A cutting edge involves its thickness and support from the body as well as hardness. A broad sliding face instead emphasises contact area and finish. Different carbon and carbide characteristics make 440C another stainless option used in these applications.
Manufacturing differences in welding and forming
The hardenability of 420 grades also matters during welding. Heating and cooling around a joint can alter local microstructure and hardness. Fabrication approaches used for familiar welded grades such as 304L therefore do not transfer directly to martensitic 420 steels. Carbon level and initial condition contribute to this distinction.
Forming generally takes place in a softer starting condition. Bending a sheet blank, preparing holes and machining the main geometry can establish the part before hardening. Any welding adds its local thermal cycle to that sequence. Final mechanical properties develop during heat treatment.
Final surface and corrosion behaviour
Chromium content alone does not explain the corrosion resistance of martensitic stainless steels. Heat treatment, resulting microstructure and final surface also matter. Machining or grinding residues, heat-treatment scale and liquid-retaining regions can change contact with the environment. A suitably prepared, clean surface contributes to component function alongside mechanical properties.
A clean, well-finished surface matters particularly in fluid-contact mechanical parts. Grinding residues, heat-treatment scale and retained liquid in a confined joint can change surface conditions. Surface preparation following hardening and precision machining is consequently among the final manufacturing stages for a 420 component.
What distinguishes 420F / 1.4029?
Grade 420F / 1.4029 is a martensitic stainless steel with sulfur added for machinability. Its carbon range differs from 420 designations such as 1.4021 and 1.4028. It is used for small shafts, valve parts and fasteners. The sulfur addition also explains why corrosion and surface requirements remain separate considerations.
A mechanical table carrying a delivery condition such as +QT850 describes quenched and tempered material. The same properties should not be expected in an annealed bar. The 420F page therefore presents mechanical ranges together with product size and condition.
Other EN designations in the 420 family
Grades 1.4031 / X39Cr13 and 1.4037 / X65Cr13 are martensitic stainless steels with different carbon ranges. Grade 1.4035 / X46CrS13 is also distinguished by its sulfur range. These are separate designations rather than arbitrary spellings of 420. Their inclusion in the corrosion-resisting steel tables of EN 10088-3 also illustrates why an application in a blade or tool-like component does not, on its own, define the material class.
The ranges below summarise chemical differences under EN 10088-3:2023; they are not a hardness table. Higher carbon can allow greater hardness after suitable heat treatment. Nevertheless, annealed product hardness and hardened-part hardness differ, and an exact HRC value cannot be calculated from carbon content alone.
| EN designation | Carbon | Maximum sulfur / sulfur range |
|---|---|---|
| 1.4031 — X39Cr13 | 0.36–0.42% | ≤ 0.030% |
| 1.4034 — X46Cr13 | 0.43–0.50% | ≤ 0.030% |
| 1.4035 — X46CrS13 | 0.43–0.50% | 0.15–0.35% |
| 1.4037 — X65Cr13 | 0.58–0.70% | ≤ 0.015% |