Steel Q345B-CR vs Q345B TMCP
Steel · Q345B temper comparison
Q345B-CR and Q345B TMCP are two conditions of the same steel grade, Q345B: CR (cold rolled) versus TMCP (thermomechanically controlled processed). The chemistry is identical, so every difference below comes from the condition. Q345B-CR is the stronger of the two: yield strength 450 MPa (65.3 ksi) against 390 MPa (56.6 ksi) for Q345B TMCP, about 15% more; tensile strength follows at 560 MPa (81.2 ksi) vs 520 MPa (75.4 ksi). In exchange, Q345B TMCP is the more ductile: elongation 25% versus 16% for Q345B-CR, and Q345B-CR is harder (180 HB vs 165 HB). Q345B-CR runs hotter in service (400°C vs 350°C continuous).
Q345B-CRChoose it when strength drives the design, or when the part sees heat.
Q345B TMCPChoose it when the part is bent, formed or impact-loaded.
Q345B-CR vs Q345B TMCP: 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.
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: Elastic (Young's) Modulus 206 GPa29.9 Msi · Shear Modulus 79 GPa11.5 Msi · Bulk Modulus 160 GPa23.2 Msi · Poisson's Ratio 0.3
Physical
Density and transition temperatures.
Same in both: Density 7.85 g/cm³0.28 lb/in³ · Melting Point (Solidus) 1,460°C2,660 °F · Liquidus Temperature 1,510°C2,750 °F
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Max Service Temperature (continuous)
Min Service Temperature
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 247 J/g106 BTU/lb
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) -0.62 V · Corrosion Resistance 12 / 100
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Polishability
Same in both: Brazeability / Solderability 55 / 100
Sustainability
Primary-production footprint per kilogram.
Same in both: Embodied Energy (primary production) 25 MJ/kg10,748 BTU/lb · Embodied Carbon (primary production) 2.1 kg CO₂/kg · Embodied Water 40 L/kg4.8 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.
Q345B-CR vs Q345B TMCP — frequently asked
Is Q345B-CR stronger than Q345B TMCP?
Yes. Q345B-CR has a typical yield strength of 450 MPa (65.3 ksi) against 390 MPa (56.6 ksi) for Q345B TMCP — about 15% more. Tensile strength is 560 MPa (81.2 ksi) vs 520 MPa (75.4 ksi).
Which condition does FabDigit quote by default, CR or TMCP?
HR is the default Q345B condition in the FabDigit quote flow (neither CR nor TMCP). 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 welds better, Q345B-CR or Q345B TMCP?
Q345B TMCP. Its weldability rates excellent (90/100) against excellent (85/100) for Q345B-CR.
Ready to make it?
Upload a CAD file and FabDigit prices the part in Q345B-CR and Q345B TMCP 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.