Steel SHY685-QT (Quenched and tempered)
Heat-treated state · default condition
Standard stocked condition for general welded high-strength structures at ambient service temperature.
Values for the QT condition
Other SHY685 tempers and conditions
SHY685 is listed in 3 conditions; see the grade overview at SHY685.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SHY685NS | Choose for thick, heavily welded joints where a lower carbon equivalent (less preheat, better HAZ toughness) is decisive. | 720 | 815 | 22 | 24 HRC | — |
Normalized | Pick when the structure must retain notch toughness down to about −40 °C (cold-climate cranes, penstocks, offshore). | 725 | 820 | 21 | 25 HRC | 7.2 % IACS |
QTDefaultThis page Quenched and tempered | Standard stocked condition for general welded high-strength structures at ambient service temperature. | 730 | 830 | 20 | 26 HRC | — |
What is SHY685-QT?
SHY685-QT is SHY685 heat treated to QT — standard stocked condition for general welded high-strength structures at ambient service temperature. SHY685-QT has a yield strength of 730 MPa (106 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 83% of steel grades. Elongation at break is 20% and the elastic modulus is 206 GPa (29.9 Msi). SHY685-QT 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).
Advantages
- High strength — 730 MPa (106 ksi), better than 83% of steel grades
Limitations
- Difficult to machine — 38/100, worse than 80% of steel grades
SHY685-QT properties
Typical room-temperature values for SHY685-QT; 10 are specific to this condition. Other listed values are SHY685 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SHY685-QT 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
SHY685-QT has a yield strength of 730 MPa (106 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 83% of steel grades. Elongation at break is 20% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
SHY685-QT is rated for continuous service to 350°C (662 °F). It conducts heat at 36 W/m·K (20.8 BTU/hr·ft·°F), worse than 73% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
SHY685-QT conducts electricity at 7.2 % IACS, worse than 71% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of SHY685-QT takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 25%.
Manufacturability7
SHY685-QT's machinability is fair (38/100, worse than 80% of steel grades); weldability good (62/100); formability fair (42/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SHY685-QT
Is SHY685 easy to machine?
Machine like 4140 Q&T at ~250–290 HB: rigid setup, coated carbide, 80–140 m/min turning, positive feeds to stay under the work-hardened skin, and flood coolant to avoid tempering the surface.
Can SHY685 be welded?
Weldable with low-hydrogen SMAW/FCAW/GMAW using ~690 MPa-class consumables; control preheat/interpass (typically 100–150 °C by thickness and Ceq), limit heat input to protect HAZ strength, and avoid PWHT above the plate's tempering temperature.
Can SHY685 be formed, bent or molded?
Cold bend transverse to rolling direction with radii of about 3–4 t and dressed edges; hot forming is discouraged because it destroys the Q&T properties unless the plate is re-quenched and tempered.
What surface finishes work on SHY685?
Not anodizable — shot blast to SA 2.5 and use epoxy/polyurethane paint, thermal-spray zinc or metallizing; if galvanizing or plating, guard against hydrogen embrittlement and liquid-metal embrittlement of this strength class.
SHY685 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≤0.14 typical for N/NS sub-grades | ≤ 0.18 | 0.14 |
| Si | 0.15 – 0.55 | 0.3 |
| Mn | 0.6 – 1.5 | 1.1 |
| Plower limit applied for NS | ≤ 0.03 | 0.01 |
| Slower limit applied for NS | ≤ 0.03 | 0.01 |
| Niadded for low-temperature toughness | ≤ 2 | 0.8 |
| Crhardenability addition | ≤ 1.2 | 0.5 |
| Mohardenability / temper resistance | ≤ 0.7 | 0.45 |
| Cuoptional | ≤ 0.5 | 0.2 |
| Vmicroalloy, optional | ≤ 0.1 | 0.04 |
| Timicroalloy, optional; protects B | ≤ 0.05 | 0.02 |
| Bhardenability, optional | ≤ 0.01 | 0 |
| Febalance; carbon equivalent / weld-crack parameter limited per JIS G3128 | balance | — |
SHY685-QT — frequently asked
What is SHY685-QT used for?
SHY685-QT is typically used for construction machinery, penstocks and welded structural fabrications. In short: 690 MPa-class weldable plate; weight-saving structural upgrade; field-weldable high-yield steel.
What is the yield strength of SHY685-QT?
SHY685-QT has a typical yield strength of 730 MPa (106 ksi) and a tensile strength of 830 MPa (120 ksi) — stronger than 83% of steel grades. Strength varies by condition: see the 3 listed tempers.
Is SHY685-QT easy to machine?
Not especially — machinability is rated fair (38/100, worse than 80% of steel grades). Machine like 4140 Q&T at ~250–290 HB: rigid setup, coated carbide, 80–140 m/min turning, positive feeds to stay under the work-hardened skin, and flood coolant to avoid tempering the surface.
Can SHY685-QT be welded?
Yes — weldability is rated good (62/100). Weldable with low-hydrogen SMAW/FCAW/GMAW using ~690 MPa-class consumables; control preheat/interpass (typically 100–150 °C by thickness and Ceq), limit heat input to protect HAZ strength, and avoid PWHT above the plate's tempering temperature.
What surface finishes work on SHY685-QT?
Not anodizable — shot blast to SA 2.5 and use epoxy/polyurethane paint, thermal-spray zinc or metallizing; if galvanizing or plating, guard against hydrogen embrittlement and liquid-metal embrittlement of this strength class.
Can SHY685-QT be formed, bent or molded?
Cold bend transverse to rolling direction with radii of about 3–4 t and dressed edges; hot forming is discouraged because it destroys the Q&T properties unless the plate is re-quenched and tempered.
What is the maximum service temperature of SHY685-QT?
SHY685-QT is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SHY685-QT and SHY685-NS?
QT is the default condition — standard stocked condition for general welded high-strength structures at ambient service temperature. NS: choose for thick, heavily welded joints where a lower carbon equivalent (less preheat, better HAZ toughness) is decisive. Yield strength is 730 MPa in QT versus 720 MPa in NS.
Sources
- JIS G 3128 — Steel plates of high yield strength for welded structure (SHY685, SHY685N, SHY685NS) — JISC (2020)
- EN 10025-6 — Flat products of high yield strength structural steels in the quenched and tempered condition (S690Q/QL/QL1) — CEN (2019)
- 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)
- High-strength quenched and tempered structural plate (690 MPa class) datasheets — Nippon Steel / JFE Steel / SSAB (2023)
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.