Steel Q355D
GB Q355D
Q355D is a Chinese GB/T 1591 low-alloy high-strength structural steel with a minimum yield of 355 MPa (≤16 mm) and guaranteed Charpy V-notch impact energy of ≥34 J at −20 °C, making it the cold-service quality level of the Q355 family.
Values for the HR condition
Q355D tempers and conditions
Q355D is supplied in 4 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
HRDefault Hot rolled | Standard stocked condition for plate, section and bar; cheapest and adequate for most welded structures up to ~40 mm. | 380 | 530 | 25 | 155 HB | 8.6 % IACS |
Normalized | Choose for thick plate, pressure or low-temperature duty where uniform fine grain and higher, more consistent impact energy are needed. | 390 | 540 | 27 | 150 HB | 8.6 % IACS |
Thermomechanically controlled processed | Pick for heavy welded fabrication: lowest carbon equivalent, best toughness and least preheat, but avoid hot forming or PWHT above ~580 °C. | 400 | 520 | 26 | 150 HB | 8.6 % IACS |
Cold drawn | Use for shafts and machined parts needing tight size and straightness; strength and hardness rise, ductility and toughness drop. | 500 | 620 | 14 | 185 HB | 8.6 % IACS |
What is Q355D?
Q355D is a Chinese GB/T 1591 low-alloy high-strength structural steel with a minimum yield of 355 MPa (≤16 mm) and guaranteed Charpy V-notch impact energy of ≥34 J at −20 °C, making it the cold-service quality level of the Q355 family. Its low carbon and controlled carbon equivalent give good weldability and cold formability, so it is the default choice for welded bridges, cranes, pressure structures, frames and mobile equipment where mild steel is too weak. Limits are ordinary (essentially nil) corrosion resistance, strength that falls with section thickness, and no meaningful service above ~400 °C. Q355D has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,450°C (2,642 °F). Q355D has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 68% of steel grades. Elongation at break is 25% and the elastic modulus is 210 GPa (30.5 Msi).
What is Q355D used for?
- Bridge girders and plate weldments
- Crane and hoist structures
- Cold-climate structural frames
- Pressure-bearing welded structures
- Mobile equipment chassis and booms
- Machine bases and heavy frames
- Structural sections and gussets
Advantages
- Readily welded — 88/100, better than 87% of steel grades
- Forms and bends easily — 70/100, better than 86% of steel grades
- Tough — resists crack growth — 120 MPa·√m (109.2 ksi·√in), better than 81% of steel grades
- Ductile — tolerates forming and impact — 25%, better than 77% of steel grades
Limitations
- Hard to polish — 45/100, worse than 84% of steel grades
Q355D properties
Typical room-temperature values for Q355D-HR; bars are the position among steel grades.
Physical3
Q355D has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,450°C (2,642 °F).
Mechanical16
Q355D has a yield strength of 380 MPa (55.1 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 68% of steel grades. Elongation at break is 25% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
Q355D is rated for continuous service to 400°C (752 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
Q355D conducts electricity at 8.6 % IACS, better than 66% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of Q355D takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability6
Q355D's machinability is good (55/100, better than 62% of steel grades); weldability excellent (88/100); 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. Q355D is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Q355D
Is Q355D easy to machine?
Machines like A572-50 mild-alloy steel — use carbide at ~120–180 m/min with good chip breaking; sticky, stringy chips in the as-rolled condition, so favour positive rake and adequate feed.
Can Q355D be welded?
Excellent weldability with Ceq ≤0.45 (E5015/ER50-6 or matching); preheat 50–100 °C only for thick sections or restraint, and use low-hydrogen practice to protect the −20 °C toughness.
Can Q355D be formed, bent or molded?
Cold bends to 2a–3a mandrel radius across the grain; hot forming 900–1050 °C followed by normalizing is fine for AR/N material, but avoid hot forming TMCP plate.
Manufacturability
The process limits FabDigit applies to Q355D. Every Q355D part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Better55 / 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 | Excellent88 / 100 |
| Bendable | Yes |
Q355D 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 |
|---|---|---|
| C≤0.20 % for ≤150 mm sections per GB/T 1591-2018 | ≤ 0.2 | 0.16 |
| Si | ≤ 0.55 | 0.3 |
| Mn | ≤ 1.6 | 1.4 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.02 | 0.01 |
| Nbmicroalloying, optional | ≤ 0.05 | 0.02 |
| Vmicroalloying, optional | ≤ 0.1 | 0.03 |
| Timicroalloying, optional | ≤ 0.05 | 0.02 |
| Crresidual | ≤ 0.3 | 0.1 |
| Niresidual | ≤ 0.5 | 0.1 |
| Curesidual | ≤ 0.4 | 0.1 |
| Moresidual | ≤ 0.1 | 0.02 |
| N | ≤ 0.01 | 0.01 |
| Altotal Al, for fine-grain/killed practice | ≥ 0.02 | 0.03 |
| FeCeq (IIW) ≤ 0.45 % typical for Q355D | balance |
What surface finishes work on Q355D?
No inherent corrosion resistance — shot blast to Sa 2½ then zinc-rich primer, hot-dip galvanize (watch Si level for coating thickness) or metallize; welds and cut edges need the same protection.
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 Q355D cost?
Q355D 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.
Q355D — frequently asked
What is Q355D used for?
Q355D is typically used for bridge girders and plate weldments, crane and hoist structures, cold-climate structural frames, pressure-bearing welded structures, mobile equipment chassis and booms and machine bases and heavy frames. In short: workhorse structural plate.
What is the yield strength of Q355D?
Q355D has a typical yield strength of 380 MPa (55.1 ksi) and a tensile strength of 530 MPa (76.9 ksi) — weaker than 68% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is Q355D easy to machine?
Reasonably — machinability is rated good (55/100, better than 62% of steel grades). Machines like A572-50 mild-alloy steel — use carbide at ~120–180 m/min with good chip breaking; sticky, stringy chips in the as-rolled condition, so favour positive rake and adequate feed.
Can Q355D be welded?
Yes — weldability is rated excellent (88/100). Excellent weldability with Ceq ≤0.45 (E5015/ER50-6 or matching); preheat 50–100 °C only for thick sections or restraint, and use low-hydrogen practice to protect the −20 °C toughness.
What surface finishes work on Q355D?
No inherent corrosion resistance — shot blast to Sa 2½ then zinc-rich primer, hot-dip galvanize (watch Si level for coating thickness) or metallize; welds and cut edges need the same protection.
Can Q355D be formed, bent or molded?
Cold bends to 2a–3a mandrel radius across the grain; hot forming 900–1050 °C followed by normalizing is fine for AR/N material, but avoid hot forming TMCP plate.
What is the maximum service temperature of Q355D?
Q355D 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 Q355D-HR and Q355D-CD?
HR is the default condition — standard stocked condition for plate, section and bar; cheapest and adequate for most welded structures up to ~40 mm. CD: use for shafts and machined parts needing tight size and straightness; strength and hardness rise, ductility and toughness drop. Yield strength is 380 MPa in HR versus 500 MPa in CD.
How much does Q355D cost?
Q355D 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 Q355D?
Yes — Q355D 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 / GB 50017 (elastic constants, thermal data) — MOHURD / SAC (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 S355J2 (comparison grade) — CEN (2019)
- worldsteel LCI data for steel plate — World Steel Association (2023)
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.