Steel 4Cr5MoSiV vs H21
Steel · grade comparison
Steel 4Cr5MoSiV and H21 are both steel grades. H21 is the stronger of the two: yield strength 620 MPa (89.9 ksi) against 500 MPa (72.5 ksi) for 4Cr5MoSiV, about 24% more; tensile strength follows at 900 MPa (131 ksi) vs 780 MPa (113 ksi). In exchange, 4Cr5MoSiV is the more ductile: elongation 22% versus 18% for H21. 4Cr5MoSiV is lighter (7.8 g/cm³ vs 8.28 g/cm³ for H21) and H21 runs hotter in service (450°C vs 400°C continuous). On the shop floor, 4Cr5MoSiV machines more easily (good vs fair).
4Cr5MoSiVChoose it when the part is bent, formed or impact-loaded, or when weight is the constraint.
H21Choose it when strength drives the design, or when the part sees heat.
4Cr5MoSiV vs H21: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all steel grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Bulk Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Reduction in Area
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
Fracture Toughness (K_IC)
Hardness, Rockwell C
Same in both: Elastic (Young's) Modulus 210 GPa30.5 Msi · Shear Modulus 81 GPa11.7 Msi
Physical
Density and transition temperatures.
Density
Same in both: Melting Point (Solidus) 1,420°C2,588 °F · Liquidus Temperature 1,480°C2,696 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Same in both: Specific Heat Capacity 460 J/kg·K0.11 BTU/lb·°F · Latent Heat of Fusion 250 J/g107 BTU/lb · Min Service Temperature -20°C-4 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Galvanic Potential (seawater, vs SCE)
Corrosion Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Formability (cold)
Polishability
Same in both: Weldability 35 / 100 · Castability 30 / 100 · Brazeability / Solderability 40 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Same in both: Typical Recycled Content 45%
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Modulus of Resilience
Thermal Diffusivity
Thermal Shock Resistance Index
Strength versus weight
Yield strength against density for every steel grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | 4Cr5MoSiV | H21 |
|---|---|---|
| CNC machining | — | Yes |
| Default condition | — | Annealed |
| Relative cost | $$ Standard | $$ Standard |
| Min. machined wall | — | 0.8 mm |
| Best machined surface | — | Ra 1.6 µm |
| AlCrN | — | Yes |
| AlTiN | — | Yes |
| Black Oxide | — | Yes |
| CVD Al2O3 | — | Yes |
| CVD TiCN | — | Yes |
| CVD TiN | — | Yes |
| Cerakote | — | Yes |
| Chrome Plating | — | Yes |
| CrN | — | Yes |
| DLC | — | Yes |
| E-Coating | — | Yes |
| HVOF Coating | — | Yes |
| Hot-Dip Galvanizing | — | Yes |
| MoS2 | — | Yes |
| Multilayer CVD | — | Yes |
| Nickel Plating | — | Yes |
| PTFE Coating | — | Yes |
| Painting | — | Yes |
They share 9 finishes: Copper Plating, Electroless Nickel (EN), Epoxy Coating, Gold Plating, Hard Chrome Plating, Manganese Phosphate, Plasma Spray, Silver Plating, Zinc Phosphate.
4Cr5MoSiV vs H21 — frequently asked
Is H21 stronger than 4Cr5MoSiV?
Yes. H21 has a typical yield strength of 620 MPa (89.9 ksi) against 500 MPa (72.5 ksi) for 4Cr5MoSiV — about 24% more. Tensile strength is 900 MPa (131 ksi) vs 780 MPa (113 ksi).
Which is cheaper, 4Cr5MoSiV or H21?
Both sit in the same relative cost tier ($$, standard); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, 4Cr5MoSiV or H21?
4Cr5MoSiV. Its machinability rates good (55/100) against fair (40/100) for H21.
Ready to make it?
Upload a CAD file and FabDigit prices the part in 4Cr5MoSiV and H21 side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.