Steel 85-QT (Quenched and tempered)
Heat-treated state · default condition
AISI/SAE 1084
Standard reference spring temper: good balance of elastic limit and toughness for general flat and coil springs.
Values for the QT condition
Other 85 tempers and conditions
85 is listed in 12 conditions; see the grade overview at 85.
Compare all 12 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition for blanking, machining and cold forming of strip and bar before hardening. | 400 | 690 | 22 | 192 HB | — |
Hot rolled | Mill supply condition for bar and hot-rolled strip; must be annealed before machining and quenched before use. | 550 | 950 | 12 | 29 HRC | 10 % IACS |
Normalized | Grain-refining pre-treatment for forged or heavily worked stock before hardening. | 590 | 1,010 | 11 | 31 HRC | 10 % IACS |
Cold drawn | Bright bar/wire with close tolerance for machined spring parts hardened afterwards. | 700 | 850 | 9 | 24 HRC | 10.5 % IACS |
QTDefaultThis page Quenched and tempered | Standard reference spring temper: good balance of elastic limit and toughness for general flat and coil springs. | 1,080 | 1,230 | 8 | 40 HRC | — |
Cold rolled hard strip | Work-hardened thin strip used directly for light shims/clips or as blanking stock for later hardening. | 1,100 | 1,250 | 3 | 40 HRC | 9.5 % IACS |
quenched + tempered ~400 °C | Higher elastic limit for thin flat springs, clips and washers where deflection loads are high. | 1,400 | 1,550 | 5 | 46 HRC | — |
Blue tempered / scaleless hardened-and-tempered spring strip | Ready-to-use hardened strip with blue oxide finish — buy this for stamped flat springs with no in-house heat treatment. | 1,450 | 1,600 | 4 | 47 HRC | 9 % IACS |
Oil quenched and tempered spring wire | Uniform tempered-martensite wire for coil springs needing consistent relaxation resistance without post-coiling hardening. | 1,450 | 1,650 | 6 | 48 HRC | 9.2 % IACS |
Patented (lead-bath) cold drawn spring wire | Fine-pearlite drawn wire for cold-coiled small springs; strength rises sharply as diameter falls. | 1,550 | 1,800 | 3 | 48 HRC | 9.2 % IACS |
quenched + low tempered 200–300 °C | Blade-like spring parts, scrapers, doctor blades and cutting-edge components needing wear resistance. | 1,650 | 1,850 | 3 | 53 HRC | — |
As-quenched | Intermediate condition only — maximum hardness but brittle; must be tempered immediately. | 1,900 | 2,200 | 0.5 | 64 HRC | 7.2 % IACS |
What is 85-QT?
85-QT is 85 heat treated to QT — standard reference spring temper: good balance of elastic limit and toughness for general flat and coil springs. 85-QT has a yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,230 MPa (178 ksi) — stronger than 93% of steel grades. Elongation at break is 8% and the elastic modulus is 207 GPa (30 Msi). 85-QT has a density of 7.81 g/cm³ (0.282 lb/in³), lighter than 84% of steel grades. It melts at 1,400°C (2,552 °F).
Advantages
- High strength — 1,080 MPa (157 ksi), better than 93% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High electrical conductivity — 9.5 % IACS, better than 75% of steel grades
Limitations
- Limited ductility — 8%, worse than 95% of steel grades
- Low fracture toughness — 40 MPa·√m (36.4 ksi·√in), worse than 92% of steel grades
- Limited formability — 12/100, worse than 92% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
- Difficult to machine — 30/100, worse than 89% of steel grades
85-QT properties
Typical room-temperature values for 85-QT; 12 are specific to this condition. Other listed values are 85 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
85-QT has a density of 7.81 g/cm³ (0.282 lb/in³), lighter than 84% of steel grades. It melts at 1,400°C (2,552 °F).
Mechanical16
85-QT has a yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,230 MPa (178 ksi) — stronger than 93% of steel grades. Elongation at break is 8% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
85-QT is rated for continuous service to 250°C (482 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
85-QT conducts electricity at 9.5 % IACS, better than 75% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 85-QT takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 25%.
Manufacturability6
85-QT's machinability is poor (30/100, worse than 89% of steel grades); weldability poor (15/100); formability not recommended (12/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 85-QT
Is 85 easy to machine?
Machine only in the spheroidize-annealed state (~190 HB) with sharp carbide or HSS tooling; above 45 HRC use grinding or EDM.
Can 85 be welded?
Essentially unweldable in service condition — 0.85 %C gives hard, crack-prone HAZ; if unavoidable preheat 250–350 °C and temper immediately after.
Can 85 be formed, bent or molded?
Blank and form in the annealed or cold-rolled state, then harden at 780–820 °C and quench in oil (thin sections) or brine; hardenability is shallow, so keep sections under ~6 mm.
What surface finishes work on 85?
Bare surface rusts quickly — finish with black-oxide/blueing plus oil, phosphate, zinc or nickel plate; bake after plating at 190–200 °C to avoid hydrogen embrittlement.
85 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 1222 grade 85; AISI 1084 is 0.80–0.93 | 0.82 – 0.9 | 0.86 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.5 – 0.8 | 0.65 |
| Crresidual | ≤ 0.25 | — |
| Niresidual | ≤ 0.35 | — |
| Curesidual | ≤ 0.25 | — |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Fe | balance | — |
85-QT — frequently asked
What is 85-QT used for?
85-QT is typically used for flat springs, blade springs and small die springs. In short: higher hardness than grade 70; thin-section spring strip; shallow hardenability.
What is the yield strength of 85-QT?
85-QT has a typical yield strength of 1,080 MPa (157 ksi) and a tensile strength of 1,230 MPa (178 ksi) — stronger than 93% of steel grades. Strength varies by condition: see the 12 listed tempers.
Is 85-QT easy to machine?
Not especially — machinability is rated poor (30/100, worse than 89% of steel grades). Machine only in the spheroidize-annealed state (~190 HB) with sharp carbide or HSS tooling; above 45 HRC use grinding or EDM.
Can 85-QT be welded?
Not readily — weldability is rated poor (15/100). Essentially unweldable in service condition — 0.85 %C gives hard, crack-prone HAZ; if unavoidable preheat 250–350 °C and temper immediately after.
What surface finishes work on 85-QT?
Bare surface rusts quickly — finish with black-oxide/blueing plus oil, phosphate, zinc or nickel plate; bake after plating at 190–200 °C to avoid hydrogen embrittlement.
Can 85-QT be formed, bent or molded?
Blank and form in the annealed or cold-rolled state, then harden at 780–820 °C and quench in oil (thin sections) or brine; hardenability is shallow, so keep sections under ~6 mm.
What is the maximum service temperature of 85-QT?
85-QT is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 85-QT and 85-Q?
QT is the default condition — standard reference spring temper: good balance of elastic limit and toughness for general flat and coil springs. Q: intermediate condition only — maximum hardness but brittle; must be tempered immediately. Yield strength is 1,080 MPa in QT versus 1,900 MPa in Q.
Sources
- GB/T 1222 (2016)
- ASTM A684 / SAE J403 (1084, 1085 carbon steel) — ASTM / SAE (2021)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Machinery's Handbook (machinability ratings, heat treatment of carbon steels) — Industrial Press (2020)
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.