Steel Q355B · supply condition · default condition
Steel Q355B-HR
Properties of the HR condition, compared with the other Q355B tempers.
Default stock form: hot-rolled plate, sections, coil and bar for general structural fabrication.
What is Q355B-HR?
Q355B-HR is Q355B supplied in the HR condition — default stock form: hot-rolled plate, sections, coil and bar for general structural fabrication. Q355B-HR has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 67% of steel grades. Elongation at break is 25% and the elastic modulus is 206 GPa (29.9 Msi). Q355B-HR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,430°C (2,606 °F).
Advantages
- Readily welded — 85/100, better than 83% of steel grades
- Forms and bends easily — 65/100, better than 81% of steel grades
- Conducts heat well — 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades
- Ductile — tolerates forming and impact — 25%, better than 76% of steel grades
Limitations
- Hard to polish — 45/100, worse than 84% of steel grades
Q355B-HR properties
Typical room-temperature values for Q355B-HR — 12 properties are specific to this condition; the rest are grade-level values shared by every Q355B temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
Q355B-HR has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,430°C (2,606 °F).
Mechanical16
Q355B-HR has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 67% of steel grades. Elongation at break is 25% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
Q355B-HR is rated for continuous service to 400°C (752 °F). It conducts heat at 48 W/m·K (27.7 BTU/hr·ft·°F), better than 79% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
Q355B-HR conducts electricity at 8.6 % IACS, better than 66% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (14/100), better than 70% of steel grades.
Sustainability4
Producing a kilogram of Q355B-HR takes about 25 MJ of energy and emits 2.1 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 22%.
Manufacturability6
Q355B-HR's machinability is good (55/100, better than 62% of steel grades); weldability excellent (85/100); formability good (65/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other Q355B tempers and conditions
Q355B is also supplied in 3 other conditions. The full side-by-side table is on the Q355B overview.
- HRDefaultDefault stock form: hot-rolled plate, sections, coil and bar for general structural fabrication.380 MPa yield · 155 HB
- CRPick for thin gauge (<3 mm) parts needing tight thickness tolerance, clean scale-free surface and direct painting.420 MPa yield · 172 HB
- GalvanizedUse where the structure is outdoors or humid and painting maintenance is undesirable; zinc gives sacrificial protection.375 MPa yield · 155 HB
- NChoose for thick plate or when finer grain, uniform properties through thickness and better low-temperature toughness are needed.375 MPa yield · 148 HB
Working with Q355B-HR
Is Q355B easy to machine?
Machines like a 0.2 %C low-alloy steel — use carbide at ~120–180 m/min, expect stringy chips and moderate tool life; ~60 % of AISI 1212 rating.
Can Q355B be welded?
Readily weldable by SMAW/GMAW/SAW with E50xx (ER50-6) consumables; preheat 75–150 °C for plate above ~30 mm or under restraint, and avoid welding through zinc on galvanized stock.
Can Q355B be formed, bent or molded?
Cold bends to 2× thickness inner radius per GB/T 1591; hot forming 900–1150 °C, and re-normalize heavy sections after severe hot work.
What surface finishes work on Q355B?
No inherent corrosion protection — shot blast to Sa2.5 then epoxy/zinc-rich primer, or hot-dip galvanize; not suitable for decorative polished exposure.
Q355B chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| CGB/T 1591-2018, AR delivery | ≤ 0.24 | 0.18 |
| Si | ≤ 0.55 | 0.3 |
| Mn | ≤ 1.6 | 1.35 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.04 | 0.02 |
| Nbmicroalloying, optional | ≤ 0.05 | 0.02 |
| Vmicroalloying, optional | ≤ 0.12 | — |
| Timicroalloying, optional | ≤ 0.2 | — |
| Crresidual | ≤ 0.3 | — |
| Niresidual | ≤ 0.3 | — |
| Curesidual | ≤ 0.4 | — |
| Moresidual | ≤ 0.1 | — |
| N | ≤ 0.01 | — |
| Altotal Al, when Nb/V/Ti not added | ≥ 0.02 | 0.03 |
| Fe | balance | — |
Q355B-HR — frequently asked
What is Q355B-HR used for?
Q355B-HR is typically used for bridges, building frames and crane jibs. In short: high-strength structural plate.
What is the yield strength of Q355B-HR?
Q355B-HR has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 67% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is Q355B-HR easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like a 0.2 %C low-alloy steel — use carbide at ~120–180 m/min, expect stringy chips and moderate tool life; ~60 % of AISI 1212 rating.
Can Q355B-HR be welded?
Yes — weldability is rated excellent (85/100). Readily weldable by SMAW/GMAW/SAW with E50xx (ER50-6) consumables; preheat 75–150 °C for plate above ~30 mm or under restraint, and avoid welding through zinc on galvanized stock.
What surface finishes work on Q355B-HR?
No inherent corrosion protection — shot blast to Sa2.5 then epoxy/zinc-rich primer, or hot-dip galvanize; not suitable for decorative polished exposure.
Can Q355B-HR be formed, bent or molded?
Cold bends to 2× thickness inner radius per GB/T 1591; hot forming 900–1150 °C, and re-normalize heavy sections after severe hot work.
What is the maximum service temperature of Q355B-HR?
Q355B-HR is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Q355B-HR and Q355B-CR?
HR is the default condition — default stock form: hot-rolled plate, sections, coil and bar for general structural fabrication. CR: pick for thin gauge (<3 mm) parts needing tight thickness tolerance, clean scale-free surface and direct painting. Yield strength is 380 MPa in HR versus 420 MPa in CR.
Can FabDigit make parts in Q355B-HR?
Yes — Q355B-HR is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- GB/T 700 / GB 50017 (elastic constants, CTE) — MOHURD (2017)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19: Fatigue and Fracture — ASM International (1996)
- EN 10025-2 S355JR (comparison grade) — CEN (2019)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.