Steel 1345 QT40-45
Hardness band
AISI/SAE 1345 · UNS G13450
QT40-45 = q&T 40–45 HRC
Maximum strength/wear condition for small cross-sections; accept low toughness and notch sensitivity.
Values for the QT40-45 condition
Other 1345 tempers and conditions
1345 is listed in 8 conditions; see the grade overview at 1345.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Pick for maximum machinability and stock removal before final quench-and-temper or for lightly loaded parts. | 440 | 725 | 20 | 205 HB | — |
Hot rolled | Cheapest mill condition for parts that will be forged, normalized or heat treated after rough machining. | 470 | 780 | 17 | 225 HB | — |
Normalized | Use to homogenize forgings and get uniform mid-strength properties without quench distortion. | 580 | 890 | 18 | 26 HRC | — |
Stress relieved | Use on cold-drawn bar or rough-machined parts to cut distortion in later machining while keeping most cold-work strength. | 620 | 790 | 15 | 21 HRC | 8 % IACS |
Cold drawn | Choose for close-tolerance bar with raised yield strength and good surface, where no further heat treatment is planned. | 690 | 830 | 12 | 23 HRC | — |
Q&T 28–32 HRC | General-purpose tough condition for shafts and levers needing good impact strength with moderate hardness. | 840 | 985 | 17 | 30 HRC | — |
Q&T 33–38 HRC | Higher-strength option for gears, spindles and highly loaded bolting where some ductility is still required. | 1,030 | 1,160 | 14 | 36 HRC | — |
QT40-45This page Q&T 40–45 HRC | Maximum strength/wear condition for small cross-sections; accept low toughness and notch sensitivity. | 1,260 | 1,400 | 11 | 43 HRC | — |
What is 1345 QT40-45?
1345 QT40-45 is 1345 heat treated to QT40-45 — maximum strength/wear condition for small cross-sections; accept low toughness and notch sensitivity. 1345 QT40-45 has a yield strength of 1,260 MPa (183 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 95% of steel grades. Elongation at break is 11% and the elastic modulus is 205 GPa (29.7 Msi). 1345 QT40-45 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). A is the default condition FabDigit quotes; QT40-45 is available on request or by drawing note.
Advantages
- High strength — 1,260 MPa (183 ksi), better than 95% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Difficult to weld — 10/100, worse than 99% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
- Difficult to machine — 22/100, worse than 95% of steel grades
- Limited ductility — 11%, worse than 89% of steel grades
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 82% of steel grades
1345 QT40-45 properties
Typical room-temperature values for 1345 QT40-45; 16 are specific to this condition. Other listed values are 1345 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
1345 QT40-45 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).
Mechanical16
1345 QT40-45 has a yield strength of 1,260 MPa (183 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 95% of steel grades. Elongation at break is 11% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
1345 QT40-45 is rated for continuous service to 300°C (572 °F). It conducts heat at 43 W/m·K (24.8 BTU/hr·ft·°F), better than 51% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
1345 QT40-45 conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 1345 QT40-45 takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
1345 QT40-45's machinability is poor (22/100, worse than 95% of steel grades); weldability not recommended (10/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 1345 QT40-45
Is 1345 easy to machine?
Machine in the annealed or cold-drawn state with rigid setups and carbide tooling; the high Mn work-hardens and gives gummy chips, so use positive rake, generous feeds and flood coolant, and finish-grind after hardening above ~35 HRC.
Can 1345 be welded?
Poor weldability (carbon equivalent >0.8): preheat 250–350 °C, use low-hydrogen consumables or matching filler, control interpass temperature and temper/stress-relieve immediately after welding to avoid martensitic cracking.
Can 1345 be formed, bent or molded?
Hot forge at 1100–1200 °C and normalize afterwards; cold forming is limited to gentle bends in the annealed condition — the high-Mn medium-carbon matrix cracks in tight radii and cold-drawn bar has little remaining ductility.
What surface finishes work on 1345?
No corrosion resistance — protect with oil, black oxide, manganese phosphate, zinc or Ni plating (bake to relieve hydrogen above 32 HRC), or paint; polishes well after hardening and takes induction-hardened, ground bearing surfaces.
1345 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 |
|---|---|---|
| CSAE/AISI 1345 heat analysis | 0.43 – 0.48 | 0.46 |
| Mn13xx manganese series | 1.6 – 1.9 | 1.75 |
| Sifor killed steel; not applicable to some semi-killed grades | 0.15 – 0.35 | 0.25 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
1345 QT40-45 — frequently asked
What is 1345 QT40-45 used for?
1345 QT40-45 is typically used for shafts, axles, machine parts and forgings. In short: deeper hardening than 1335; poor weldability, high CE; forging and shaft grade.
What is the yield strength of 1345 QT40-45?
1345 QT40-45 has a typical yield strength of 1,260 MPa (183 ksi) and a tensile strength of 1,400 MPa (203 ksi) — stronger than 95% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 1345 QT40-45 easy to machine?
Not especially — machinability is rated poor (22/100, worse than 95% of steel grades). Machine in the annealed or cold-drawn state with rigid setups and carbide tooling; the high Mn work-hardens and gives gummy chips, so use positive rake, generous feeds and flood coolant, and finish-grind after hardening above ~35 HRC.
Can 1345 QT40-45 be welded?
Not readily — weldability is rated not recommended (10/100). Poor weldability (carbon equivalent >0.8): preheat 250–350 °C, use low-hydrogen consumables or matching filler, control interpass temperature and temper/stress-relieve immediately after welding to avoid martensitic cracking.
What surface finishes work on 1345 QT40-45?
No corrosion resistance — protect with oil, black oxide, manganese phosphate, zinc or Ni plating (bake to relieve hydrogen above 32 HRC), or paint; polishes well after hardening and takes induction-hardened, ground bearing surfaces.
Can 1345 QT40-45 be formed, bent or molded?
Hot forge at 1100–1200 °C and normalize afterwards; cold forming is limited to gentle bends in the annealed condition — the high-Mn medium-carbon matrix cracks in tight radii and cold-drawn bar has little remaining ductility.
What is the maximum service temperature of 1345 QT40-45?
1345 QT40-45 is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 1345-A and 1345 QT40-45?
A is the default condition — pick for maximum machinability and stock removal before final quench-and-temper or for lightly loaded parts. QT40-45: maximum strength/wear condition for small cross-sections; accept low toughness and notch sensitivity. Yield strength is 440 MPa in A versus 1,260 MPa in QT40-45.
Sources
- SAE J403 — Chemical Compositions of SAE Carbon and Alloy Steels (13xx) — SAE International (2014)
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought, General Requirements — ASTM (2020)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 4A — Steel Heat Treating Fundamentals and Processes — ASM International (2013)
- Machinery's Handbook, 31st ed. (machinability ratings) — 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.