Steel 65Mn · heat-treated state
Steel 65Mn Q&T
Properties of the Q&T condition, compared with the other 65Mn tempers.
High-temper condition per GB/T 1222 mechanical test requirement — best strength/toughness balance for structural spring parts.
What is 65Mn Q&T?
65Mn Q&T is 65Mn heat treated to Q&T — high-temper condition per GB/T 1222 mechanical test requirement — best strength/toughness balance for structural spring parts. 65Mn Q&T has a yield strength of 850 MPa (123 ksi) and a tensile strength of 1,080 MPa (157 ksi) — stronger than 88% of steel grades. Elongation at break is 10% and the elastic modulus is 206 GPa (29.9 Msi). 65Mn Q&T has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). Annealed is the default condition FabDigit quotes; Q&T is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High strength — 850 MPa (123 ksi), better than 88% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
Limitations
- Limited ductility — 10%, worse than 91% of steel grades
- Limited formability — 20/100, worse than 80% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
65Mn Q&T properties
Typical room-temperature values for 65Mn Q&T — 15 properties are specific to this condition; the rest are grade-level values shared by every 65Mn temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
65Mn Q&T has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical14
65Mn Q&T has a yield strength of 850 MPa (123 ksi) and a tensile strength of 1,080 MPa (157 ksi) — stronger than 88% of steel grades. Elongation at break is 10% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
65Mn Q&T 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 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
65Mn Q&T conducts electricity at 8.5 % IACS, better than 62% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 87% of steel grades.
Sustainability4
Producing a kilogram of 65Mn Q&T takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
65Mn Q&T's machinability is fair (50/100, worse than 53% of steel grades); weldability poor (25/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 65Mn tempers and conditions
65Mn is also supplied in 6 other conditions. The full side-by-side table is on the 65Mn overview.
- AnnealedDefaultDefault stocked condition — softest state for machining, blanking and cold forming before hardening.440 MPa yield · 215 HB
- Hardened & Tempered 50-55 HRCPick for wear-critical thin sections — blades, scrapers, mower and saw teeth — where edge retention beats toughness.1,650 MPa yield · 53 HRC
- Hardened & TemperedStandard spring temper for leaf springs, saw blades and clutch plates — maximum elastic limit with usable toughness.1,400 MPa yield · 46 HRC
- Cold DrawnWork-hardened strip or wire used where hardness is achieved without heat treatment (washers, shims, clips).900 MPa yield · 31 HRC
- Q&THigh-temper condition per GB/T 1222 mechanical test requirement — best strength/toughness balance for structural spring parts.850 MPa yield · 34 HRC
- NormalizedGrain-refining pre-treatment for forgings and heavy bar before final quench and temper.560 MPa yield · 265 HB
- Hot RolledCheapest mill condition for stock that will be re-heat-treated by the fabricator.520 MPa yield · 260 HB
Working with 65Mn Q&T
Is 65Mn easy to machine?
Machine only in the spheroidise-annealed state (≈55 % of 1212); hardened 65Mn needs grinding, CBN or carbide at low feed.
Can 65Mn be welded?
Poor — 0.66 % C gives hard, crack-prone HAZ; if unavoidable use preheat 250–350 °C, low-hydrogen filler and immediate stress-relief/temper, then re-heat-treat.
Can 65Mn be formed, bent or molded?
Blank and bend in the annealed condition with generous radii (≥3 t); hardened spring temper allows only light setting, so form first and heat-treat after; oil quench 810–840 °C, temper 350–420 °C for spring properties.
What surface finishes work on 65Mn?
No anodising — protect with oil, phosphate + oil, black oxide, zinc or Zn-Ni plating (bake to avoid hydrogen embrittlement above 40 HRC); grinds and polishes well when hardened; shot peening markedly raises spring fatigue life.
65Mn 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 | 0.62 – 0.7 | 0.66 |
| Si | 0.17 – 0.37 | 0.27 |
| Mnraises hardenability vs 1065 | 0.9 – 1.2 | 1.05 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Crresidual max | ≤ 0.25 | — |
| Niresidual max | ≤ 0.35 | — |
| Curesidual max | ≤ 0.25 | — |
| Fe | balance | — |
65Mn Q&T — frequently asked
What is 65Mn Q&T used for?
65Mn Q&T is typically used for coil springs, saw blades and springs. In short: medium-carbon spring bar.
What is the yield strength of 65Mn Q&T?
65Mn Q&T has a typical yield strength of 850 MPa (123 ksi) and a tensile strength of 1,080 MPa (157 ksi) — stronger than 88% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 65Mn Q&T easy to machine?
Reasonably — machinability is rated fair (50/100, worse than 53% of steel grades). Machine only in the spheroidise-annealed state (≈55 % of 1212); hardened 65Mn needs grinding, CBN or carbide at low feed.
Can 65Mn Q&T be welded?
Not readily — weldability is rated poor (25/100). Poor — 0.66 % C gives hard, crack-prone HAZ; if unavoidable use preheat 250–350 °C, low-hydrogen filler and immediate stress-relief/temper, then re-heat-treat.
What surface finishes work on 65Mn Q&T?
No anodising — protect with oil, phosphate + oil, black oxide, zinc or Zn-Ni plating (bake to avoid hydrogen embrittlement above 40 HRC); grinds and polishes well when hardened; shot peening markedly raises spring fatigue life.
Can 65Mn Q&T be formed, bent or molded?
Blank and bend in the annealed condition with generous radii (≥3 t); hardened spring temper allows only light setting, so form first and heat-treat after; oil quench 810–840 °C, temper 350–420 °C for spring properties.
What is the maximum service temperature of 65Mn Q&T?
65Mn Q&T 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.
Can FabDigit make parts in 65Mn Q&T?
Yes — 65Mn Q&T is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- GB/T 1222 Spring steels (2016)
- GB/T 699 Quality carbon structural steels — SAC (2015)
- 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.