Steel A387 Gr 21L Class 1 PWHT vs A387 Gr 21L Class 1 Q+T
Steel · A387 Gr 21L Class 1 temper comparison
A387 Gr 21L Class 1 PWHT and A387 Gr 21L Class 1 Q+T are two conditions of the same steel grade, A387 Gr 21L Class 1: PWHT (post-weld heat treated) versus Q+T (quenched and tempered). The chemistry is identical, so every difference below comes from the condition. A387 Gr 21L Class 1 Q+T is the stronger of the two: yield strength 350 MPa (50.8 ksi) against 245 MPa (35.5 ksi) for A387 Gr 21L Class 1 PWHT, about 43% more; tensile strength follows at 520 MPa (75.4 ksi) vs 450 MPa (65.3 ksi). In exchange, A387 Gr 21L Class 1 PWHT is the more ductile: elongation 29% versus 25% for A387 Gr 21L Class 1 Q+T, and A387 Gr 21L Class 1 Q+T is harder (160 HB vs 133 HB).
A387 Gr 21L Class 1 PWHTChoose it when the part is bent, formed or impact-loaded.
A387 Gr 21L Class 1 Q+TChoose it when strength drives the design.
A387 Gr 21L Class 1 PWHT vs A387 Gr 21L Class 1 Q+T: 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.
A387 Gr 21L Class 1 PWHTA387 Gr 21L Class 1 Q+T
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) 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: Shear Modulus 80 GPa11.6 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.29
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,425°C2,597 °F · Liquidus Temperature 1,510°C2,750 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Same in both: Specific Heat Capacity 460 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 · Max Service Temperature (continuous) 540°C1,004 °F · Min Service Temperature -30°C-22 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Same in both: Galvanic Potential (seawater, vs SCE) -0.6 V · Corrosion Resistance 22 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Same in both: Brazeability / Solderability 45 / 100 · Polishability 50 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 31 MJ/kg13,328 BTU/lb · Embodied Carbon (primary production) 2.3 kg CO₂/kg · Embodied Water 45 L/kg5.4 gal/lb · Typical Recycled Content 25%
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.
A387 Gr 21L Class 1 PWHT vs A387 Gr 21L Class 1 Q+T — frequently asked
Is A387 Gr 21L Class 1 Q+T stronger than A387 Gr 21L Class 1 PWHT?
Yes. A387 Gr 21L Class 1 Q+T has a typical yield strength of 350 MPa (50.8 ksi) against 245 MPa (35.5 ksi) for A387 Gr 21L Class 1 PWHT — about 43% more. Tensile strength is 520 MPa (75.4 ksi) vs 450 MPa (65.3 ksi).
Which condition does FabDigit quote by default, PWHT or Q+T?
N+T is the default A387 Gr 21L Class 1 condition in the FabDigit quote flow (neither PWHT nor Q+T). The other condition is available on request or by drawing note — specify it in the material field or the part notes and the quote is priced for it.
Which is easier to machine, A387 Gr 21L Class 1 PWHT or A387 Gr 21L Class 1 Q+T?
A387 Gr 21L Class 1 PWHT. Its machinability rates good (57/100) against fair (48/100) for A387 Gr 21L Class 1 Q+T.
Ready to make it?
Upload a CAD file and FabDigit prices the part in A387 Gr 21L Class 1 PWHT and A387 Gr 21L Class 1 Q+T 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.