Steel Q355C
GB Q355C
Q355C is a Chinese hot-rolled low-alloy high-strength structural steel to GB/T 1591-2018, with a 355 MPa minimum yield (t ≤ 16 mm) and guaranteed Charpy V-notch impact energy of 34 J at 0 °C (quality class C).
Values for the HR condition
Q355C tempers and conditions
Q355C is supplied in 3 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
HRDefault Hot rolled | Default stock condition for plate, section, coil and bar; use for general welded structures at ≥0 °C. | 380 | 520 | 26 | 150 HB | — |
Normalized | Pick for thick plate (>40 mm) or when finer grain and higher, more uniform through-thickness toughness is required. | 390 | 530 | 28 | 155 HB | — |
Cold drawn | Choose for round/square bar needing tight tolerance and bright surface; strength up, ductility and toughness down. | 520 | 620 | 12 | 185 HB | — |
What is Q355C?
Q355C is a Chinese hot-rolled low-alloy high-strength structural steel to GB/T 1591-2018, with a 355 MPa minimum yield (t ≤ 16 mm) and guaranteed Charpy V-notch impact energy of 34 J at 0 °C (quality class C). It is chosen for welded bridges, buildings, cranes, pressure parts and heavy machine frames where plain Q235 lacks strength but full alloy steel is unnecessary, offering good weldability (CEV ≈ 0.40–0.47) and cold formability. Limits are modest corrosion resistance (needs paint or galvanizing), no low-temperature guarantee below 0 °C (use Q355D/E), and yield strength that falls with increasing plate thickness. Q355C has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,500°C (2,732 °F). Q355C has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 68% of steel grades. Elongation at break is 26% and the elastic modulus is 206 GPa (29.9 Msi).
What is Q355C used for?
- Welded bridge girders
- Crane and hoist structures
- Building and platform framing
- Heavy machine frames and bases
- Pressure parts for above-zero service
- Baseplates and gussets
- Mining and earthmoving structures
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Forms and bends easily — 70/100, better than 86% of steel grades
- Readily welded — 85/100, better than 83% of steel grades
- Ductile — tolerates forming and impact — 26%, better than 82% of steel grades
Limitations
- Hard to polish — 40/100, worse than 96% of steel grades
Q355C properties
Typical room-temperature values for Q355C-HR; bars are the position among steel grades.
Physical3
Q355C has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,500°C (2,732 °F).
Mechanical16
Q355C has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 68% of steel grades. Elongation at break is 26% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
Q355C is rated for continuous service to 400°C (752 °F). It conducts heat at 45 W/m·K (26 BTU/hr·ft·°F), better than 66% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
Q355C conducts electricity at 8.2 % IACS, better than 61% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of Q355C takes about 24 MJ of energy and emits 1.9 kg of CO₂ — less than 97% of steel grades. Typical recycled content is 25%.
Manufacturability6
Q355C's machinability is good (60/100, better than 83% of steel grades); weldability excellent (85/100); formability very good (70/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. Q355C is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Q355C
Is Q355C easy to machine?
Cuts like a 0.17 %C Mn steel at ~150 HB — carbide inserts, 120–200 m/min turning; slightly gummy chips, so use positive rake and good coolant.
Can Q355C be welded?
Excellent for SMAW/GMAW/SAW with E50 (490 MPa class) consumables; preheat 80–150 °C only for thick sections or restraint, no PWHT needed for normal thicknesses.
Can Q355C be formed, bent or molded?
Cold-bends to the GB/T 1591 mandrel requirement (d = 2a for t ≤ 16 mm); hot forming 900–1100 °C, avoid finishing below 800 °C to keep grain size.
Manufacturability
The process limits FabDigit applies to Q355C. Every Q355C part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better60 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Excellent70 / 100 |
|---|---|
| Weldability | Excellent85 / 100 |
| Bendable | Yes |
Q355C 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, hot-rolled Q355C | ≤ 0.2 | 0.17 |
| Si | ≤ 0.55 | 0.3 |
| Mn | ≤ 1.6 | 1.4 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| NbNb+V+Ti ≤ 0.22 total | ≤ 0.05 | 0.02 |
| V | ≤ 0.1 | 0.02 |
| Ti | ≤ 0.05 | 0.01 |
| Altotal Al (Als), when Nb/V/Ti not added | ≥ 0.02 | 0.03 |
| Crresidual | ≤ 0.3 | 0.05 |
| Niresidual | ≤ 0.3 | 0.03 |
| Curesidual | ≤ 0.4 | 0.05 |
| Moresidual | ≤ 0.1 | 0.01 |
| N | ≤ 0.01 | 0.01 |
| Fe | balance |
What surface finishes work on Q355C?
Must be protected — shot blast to Sa 2.5 then epoxy/zinc-rich primer, or hot-dip galvanize (Si held below 0.55 % keeps coating growth reasonable).
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
How much does Q355C cost?
Q355C is a budget-cost steel ($), cheaper than about 99% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Q355C — frequently asked
What is Q355C used for?
Q355C is typically used for welded bridge girders, crane and hoist structures, building and platform framing, heavy machine frames and bases, pressure parts for above-zero service and baseplates and gussets. In short: high-strength structural plate.
What is the yield strength of Q355C?
Q355C has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 68% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is Q355C easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Cuts like a 0.17 %C Mn steel at ~150 HB — carbide inserts, 120–200 m/min turning; slightly gummy chips, so use positive rake and good coolant.
Can Q355C be welded?
Yes — weldability is rated excellent (85/100). Excellent for SMAW/GMAW/SAW with E50 (490 MPa class) consumables; preheat 80–150 °C only for thick sections or restraint, no PWHT needed for normal thicknesses.
What surface finishes work on Q355C?
Must be protected — shot blast to Sa 2.5 then epoxy/zinc-rich primer, or hot-dip galvanize (Si held below 0.55 % keeps coating growth reasonable).
Can Q355C be formed, bent or molded?
Cold-bends to the GB/T 1591 mandrel requirement (d = 2a for t ≤ 16 mm); hot forming 900–1100 °C, avoid finishing below 800 °C to keep grain size.
What is the maximum service temperature of Q355C?
Q355C 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 Q355C-HR and Q355C-CD?
HR is the default condition — default stock condition for plate, section, coil and bar; use for general welded structures at ≥0 °C. CD: choose for round/square bar needing tight tolerance and bright surface; strength up, ductility and toughness down. Yield strength is 380 MPa in HR versus 520 MPa in CD.
How much does Q355C cost?
Q355C is a budget-cost steel ($), cheaper than about 99% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in Q355C?
Yes — Q355C is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- GB/T 700-2006 (comparison basis) — SAC (2006)
- ASTM A572/A572M Grade 50 (equivalent HSLA plate) — ASTM (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.