Steel Q690
GB Q690
Q690 is a quenched-and-tempered or TMCP high-strength structural steel plate, offered in C, D, E and F impact classes and closely comparable to S690Q.
Reference datasheet — Q690 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the QT condition
Q690 tempers and conditions
Q690 is supplied in 2 conditions, soft to hard. QT is the default FabDigit quotes; the values on this page are for it.
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Thermomechanically controlled processed | Pick for lower carbon equivalent and easier field welding (less/no preheat) in medium thickness plate and welded box sections. | 715 | 830 | 17 | 22 HRC | 7.8 % IACS |
QTDefault Quenched and tempered | Standard supply condition for thick high-strength plate; best strength/toughness balance for crane booms and heavy equipment. | 730 | 850 | 16 | 25 HRC | — |
Supply forms, finishes and certifications
Ways Q690 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
Q690C | Quality grade C, Charpy V-notch qualified at 0 °C | Certification |
Q690D | Quality grade D, Charpy V-notch qualified at −20 °C | Certification |
Q690E | Quality grade E, Charpy V-notch qualified at −40 °C | Certification |
Q690F | Quality grade F, Charpy V-notch qualified at −60 °C | Certification |
What is Q690?
Q690 is a quenched-and-tempered or TMCP high-strength structural steel plate, offered in C, D, E and F impact classes and closely comparable to S690Q. It is specified where strength-to-weight drives the design: 730 MPa yield, 850 MPa tensile, 16 % elongation, about 255 HB (25 HRC) and service to 400 °C. The trade-offs are limited cold formability, machinability around 40 % of AISI 1212, and welding that needs low-hydrogen consumables, preheat and heat-input control to preserve HAZ toughness. It has no atmospheric corrosion resistance; Q550 is the usual fallback when better forming and welding behaviour matters more than yield strength. Q690 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). Q690 has a yield strength of 730 MPa (106 ksi) and a tensile strength of 850 MPa (123 ksi) — stronger than 83% of steel grades. Elongation at break is 16% and the elastic modulus is 206 GPa (29.9 Msi).
What is Q690 used for?
- excavator arms
- mobile crane sections
- mining equipment
Advantages
- High strength — 730 MPa (106 ksi), better than 83% of steel grades
Limitations
- Difficult to machine — 40/100, worse than 77% of steel grades
Q690 properties
Typical room-temperature values for Q690-QT; bars are the position among steel grades.
Physical3
Q690 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
Q690 has a yield strength of 730 MPa (106 ksi) and a tensile strength of 850 MPa (123 ksi) — stronger than 83% of steel grades. Elongation at break is 16% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
Q690 is rated for continuous service to 400°C (752 °F). It conducts heat at 40 W/m·K (23.1 BTU/hr·ft·°F), worse than 64% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
Q690 conducts electricity at 7.6 % IACS, worse than 65% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of Q690 takes about 26 MJ of energy and emits 2.1 kg of CO₂ — less than 64% of steel grades. Typical recycled content is 25%.
Manufacturability5
Q690's machinability is fair (40/100, worse than 77% of steel grades); weldability good (65/100); formability fair (40/100).
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. Q690 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Q690
Is Q690 easy to machine?
Machine as a ~255 HB Q&T alloy steel: rigid setups, coated carbide, 80–140 m/min turning, moderate feeds; avoid dry grinding that can re-temper or crack the surface.
Can Q690 be welded?
Use low-hydrogen consumables matching ~690 MPa, preheat 100–150 °C (thickness/CEV dependent), interpass ≤250 °C and controlled heat input to protect HAZ toughness; no PWHT above the tempering temperature.
Can Q690 be formed, bent or molded?
Cold-bend transverse to rolling direction with minimum inner radius ≈3t (roll-form rather than press where possible); hot forming above ~580 °C destroys the Q&T condition and requires re-heat-treatment.
Q690 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 some thick Q&T plate per GB/T 16270 | ≤ 0.18 | 0.15 |
| Si | ≤ 0.6 | 0.3 |
| Mn | ≤ 2 | 1.5 |
| P≤0.020 for D, ≤0.020/0.018 for E/F | ≤ 0.03 | 0.01 |
| S≤0.010 for E, ≤0.008 for F | ≤ 0.02 | 0.01 |
| Nbmicro-alloying | ≤ 0.11 | 0.04 |
| V | ≤ 0.2 | 0.05 |
| Ti | ≤ 0.05 | 0.02 |
| Cr | ≤ 1 | 0.4 |
| Nihigher for E/F grades | ≤ 0.8 | 0.3 |
| Cu | ≤ 0.8 | 0.2 |
| Mo | ≤ 0.3 | 0.2 |
| Bhardenability booster in Q&T plate | ≤ 0 | 0 |
| Altotal Al | ≥ 0.02 | 0.03 |
| N | ≤ 0.02 | 0.01 |
| Fe | balance |
What surface finishes work on Q690?
No inherent corrosion resistance — shot-blast to Sa 2.5 and apply epoxy/zinc-rich primer systems; if hot-dip galvanizing, watch for liquid-metal-assisted and hydrogen embrittlement risks in high-strength sections.
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).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel Q690 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- S690Q
How much does Q690 cost?
Q690 is a budget-cost steel ($), cheaper than about 90% 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.
Q690 — frequently asked
What is Q690 used for?
Q690 is typically used for excavator arms, mobile crane sections and mining equipment. In short: 690 MPa-class Q&T plate; maximum structural strength-to-weight; restricted cold formability.
What is the yield strength of Q690?
Q690 has a typical yield strength of 730 MPa (106 ksi) and a tensile strength of 850 MPa (123 ksi) — stronger than 83% of steel grades. Strength varies by condition: see the 2 listed tempers.
Is Q690 easy to machine?
Not especially — machinability is rated fair (40/100, worse than 77% of steel grades). Machine as a ~255 HB Q&T alloy steel: rigid setups, coated carbide, 80–140 m/min turning, moderate feeds; avoid dry grinding that can re-temper or crack the surface.
Can Q690 be welded?
Yes — weldability is rated good (65/100). Use low-hydrogen consumables matching ~690 MPa, preheat 100–150 °C (thickness/CEV dependent), interpass ≤250 °C and controlled heat input to protect HAZ toughness; no PWHT above the tempering temperature.
What surface finishes work on Q690?
No inherent corrosion resistance — shot-blast to Sa 2.5 and apply epoxy/zinc-rich primer systems; if hot-dip galvanizing, watch for liquid-metal-assisted and hydrogen embrittlement risks in high-strength sections.
Can Q690 be formed, bent or molded?
Cold-bend transverse to rolling direction with minimum inner radius ≈3t (roll-form rather than press where possible); hot forming above ~580 °C destroys the Q&T condition and requires re-heat-treatment.
What is the maximum service temperature of Q690?
Q690 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 Q690-QT and Q690 TMCP?
QT is the default condition — standard supply condition for thick high-strength plate; best strength/toughness balance for crane booms and heavy equipment. TMCP: pick for lower carbon equivalent and easier field welding (less/no preheat) in medium thickness plate and welded box sections. Yield strength is 730 MPa in QT versus 715 MPa in TMCP.
How much does Q690 cost?
Q690 is a budget-cost steel ($), cheaper than about 90% 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.
Sources
- EN 10025-6 Hot rolled products of structural steels — quenched and tempered plates (S690Q/QL/QL1) — CEN (2019)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- High-strength quenched & tempered structural plate datasheets (S690Q/Q690 class) — Steel plate producers (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.