Steel Q235B vs S355J2
Steel · grade comparison
Steel Q235B and S355J2 are both steel grades, both structural steel. S355J2 is the stronger of the two: yield strength 390 MPa (56.6 ksi) against 250 MPa (36.3 ksi) for Q235B, about 56% more; tensile strength follows at 520 MPa (75.4 ksi) vs 420 MPa (60.9 ksi). In exchange, Q235B is the more ductile: elongation 28% versus 24% for S355J2, and S355J2 is harder (170 HB vs 120 HB). S355J2 runs hotter in service (400°C vs 350°C continuous) and Q235B conducts heat better (50 W/m·K vs 45 W/m·K). On the shop floor, Q235B machines more easily (65 vs 55 out of 100).
Q235BChoose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
S355J2Choose it when strength drives the design, or when the part sees heat.
Q235B vs S355J2: 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.
Elastic (Young's) Modulus
Shear Modulus
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Reduction in Area
Compressive Strength
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Rockwell B
Hardness, Vickers
Same in both: Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.3
Physical
Density and transition temperatures.
Melting Point (Solidus)
Liquidus Temperature
Same in both: Density 7.85 g/cm³0.28 lb/in³
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Max Service Temperature (continuous)
Same in both: Specific Heat Capacity 470 J/kg·K0.11 BTU/lb·°F · Thermal Expansion (CTE, 20–100 °C) 12 µm/m·K6.7 µin/in·°F · Latent Heat of Fusion 270 J/g116 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 %)
Weldability
Formability (cold)
Castability
Brazeability / Solderability
Same in both: Polishability 40 / 100
Sustainability
Primary-production footprint per kilogram.
Embodied Water
Typical Recycled Content
Same in both: Embodied Energy (primary production) 25 MJ/kg10,748 BTU/lb · Embodied Carbon (primary production) 2 kg CO₂/kg
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 | Q235B | S355J2 |
|---|---|---|
| Default condition | HR | HR |
| Relative cost | $ Budget | $ Budget |
| Min. machined wall | 0.8 mm | 0.8 mm |
| Best machined surface | Ra 1.6 µm | Ra 1.6 µm |
Both are offered for CNC machining and Sheet metal. Both take the same 38 finishes: AlCrN, AlTiN, Black Oxide, CVD Al2O3, CVD TiCN, CVD TiN, Cerakote, Chrome Plating, Copper Plating, CrN, DLC, E-Coating and 26 more.
Q235B vs S355J2 — frequently asked
Is S355J2 stronger than Q235B?
Yes. S355J2 has a typical yield strength of 390 MPa (56.6 ksi) against 250 MPa (36.3 ksi) for Q235B — about 56% more. Tensile strength is 520 MPa (75.4 ksi) vs 420 MPa (60.9 ksi).
Which is cheaper, Q235B or S355J2?
Both sit in the same relative cost tier ($, budget); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, Q235B or S355J2?
Q235B, by a small margin. Both rate good for machinability — 65/100 against 55/100 for S355J2; for welding the order is Q235B first (excellent, 95/100) then S355J2 (excellent, 88/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in Q235B and S355J2 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.