Steel 1340 · heat-treated state
Steel 1340 Q&T 650C
Properties of the Q&T 650C condition, compared with the other 1340 tempers.
Toughest Q&T condition for impact-loaded or low-temperature parts where ~800 MPa is enough.
What is 1340 Q&T 650C?
1340 Q&T 650C is 1340 heat treated to Q&T 650C — toughest Q&T condition for impact-loaded or low-temperature parts where ~800 MPa is enough. 1340 Q&T 650C has a yield strength of 621 MPa (90.1 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 79% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi). 1340 Q&T 650C 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). HR is the default condition FabDigit quotes; Q&T 650C is available on request or by drawing note.
Advantages
- High service temperature — 500°C (932 °F), better than 90% of steel grades
- High strength — 621 MPa (90.1 ksi), better than 79% of steel grades
1340 Q&T 650C properties
Typical room-temperature values for 1340 Q&T 650C — 14 properties are specific to this condition; the rest are grade-level values shared by every 1340 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
1340 Q&T 650C 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).
Mechanical13
1340 Q&T 650C has a yield strength of 621 MPa (90.1 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 79% of steel grades. Elongation at break is 22% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
1340 Q&T 650C is rated for continuous service to 500°C (932 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
1340 Q&T 650C conducts electricity at 7.8 % IACS, worse than 58% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 87% of steel grades.
Sustainability4
Producing a kilogram of 1340 Q&T 650C takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 55% of steel grades. Typical recycled content is 30%.
Manufacturability6
1340 Q&T 650C's machinability is fair (48/100, worse than 57% of steel grades); weldability fair (35/100); formability poor (28/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 1340 tempers and conditions
1340 is also supplied in 9 other conditions. The full side-by-side table is on the 1340 overview.
- HRDefaultCheapest stock condition for parts that will be machined and then heat treated.470 MPa yield · 217 HB
- Q&T 205CMaximum-hardness condition for wear parts; very low ductility and notch sensitivity, rarely used structurally.1,593 MPa yield · 50 HRC
- Q&T 315CHigh-strength wear/spring-like condition; watch tempered-martensite embrittlement in this range.1,462 MPa yield · 46 HRC
- Q&T 425CCommon high-strength shaft/bolt condition around 1200 MPa UTS with usable toughness.1,130 MPa yield · 40 HRC
- Q&TGeneral-purpose quenched-and-tempered condition balancing ~950 MPa strength with good toughness for shafts and bolts.830 MPa yield · 31 HRC
- CRPick for close tolerance, bright finish and higher as-supplied yield without heat treatment.705 MPa yield · 240 HB
- Q&T 650CToughest Q&T condition for impact-loaded or low-temperature parts where ~800 MPa is enough.621 MPa yield · 25 HRC
- Cold Finished1340 manganese alloy steel supplied as cold-drawn/turned-and-polished bar: ~15–20 % strength gain and tight size tolerance over hot-rolled, with reduced ductility and residual stress.590 MPa yield · 207 HB
- NormalizedUniform fine-grain structure with higher strength than annealed; good pre-machining or as-delivered condition for forgings.558 MPa yield · 24 HRC
- AnnealedSoftest, most machinable and most formable condition; used for deep machining before hardening.435 MPa yield · 207 HB
Working with 1340 Q&T 650C
Is 1340 easy to machine?
Machine in the annealed or normalized condition (~55 % of 1212); use rigid setups, carbide at 120–180 m/min, and expect gummy chips from high Mn.
Can 1340 be welded?
Weldable with low-hydrogen consumables but CE ≈ 0.75 demands 200–300 °C preheat, interpass control and post-weld temper to avoid HAZ cracking.
Can 1340 be formed, bent or molded?
Hot forge 1100–1200 °C, finish above 900 °C; cold forming limited to mild bends in the annealed state due to high yield and work hardening.
What surface finishes work on 1340?
No inherent corrosion resistance — oil, black oxide, phosphate, zinc/Zn-Ni plating or paint; bake after plating to relieve hydrogen embrittlement above 40 HRC.
1340 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 | 0.38 – 0.43 | 0.4 |
| Mnprimary hardenability element | 1.6 – 1.9 | 1.75 |
| Si | 0.15 – 0.35 | 0.25 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
1340 Q&T 650C — frequently asked
What is 1340 Q&T 650C used for?
1340 Q&T 650C is typically used for shafts, forged gears and industrial bolts. In short: manganese chromium bar.
What is the yield strength of 1340 Q&T 650C?
1340 Q&T 650C has a typical yield strength of 621 MPa (90.1 ksi) and a tensile strength of 800 MPa (116 ksi) — stronger than 79% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 1340 Q&T 650C easy to machine?
Reasonably — machinability is rated fair (48/100, worse than 57% of steel grades). Machine in the annealed or normalized condition (~55 % of 1212); use rigid setups, carbide at 120–180 m/min, and expect gummy chips from high Mn.
Can 1340 Q&T 650C be welded?
With care — weldability is rated fair (35/100). Weldable with low-hydrogen consumables but CE ≈ 0.75 demands 200–300 °C preheat, interpass control and post-weld temper to avoid HAZ cracking.
What surface finishes work on 1340 Q&T 650C?
No inherent corrosion resistance — oil, black oxide, phosphate, zinc/Zn-Ni plating or paint; bake after plating to relieve hydrogen embrittlement above 40 HRC.
Can 1340 Q&T 650C be formed, bent or molded?
Hot forge 1100–1200 °C, finish above 900 °C; cold forming limited to mild bends in the annealed state due to high yield and work hardening.
What is the maximum service temperature of 1340 Q&T 650C?
1340 Q&T 650C is rated for continuous use to about 500°C (932 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 1340-HR and 1340-CR?
HR is the default condition — cheapest stock condition for parts that will be machined and then heat treated. CR: pick for close tolerance, bright finish and higher as-supplied yield without heat treatment. Yield strength is 470 MPa in HR versus 705 MPa in CR.
Can FabDigit make parts in 1340 Q&T 650C?
Yes — 1340 Q&T 650C 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
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1397 — Estimated Mechanical Properties of Steel Bars — SAE International (2018)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- GB/T 3077 (40Mn2) — SAC (2015)
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.