Steel 1548 QT40-45HRC
Hardness band
AISI/SAE 1548 · UNS G15480 · EN 1.1226
High-strength condition for heavily loaded pins, levers and spring-type parts where impact demand is moderate.
Values for the QT40-45HRC condition
Other 1548 tempers and conditions
1548 is listed in 8 conditions; see the grade overview at 1548.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition; choose for maximum machinability and for parts that will be quench hardened afterwards. | 350 | 600 | 20 | 170 HB | — |
HRDefault Hot rolled | Lowest-cost stock condition for forged/machined shafts that will later be normalized, Q&T or induction hardened. | 365 | 660 | 12 | 197 HB | — |
Normalized | Uniform fine pearlitic structure for forgings before machining or induction hardening; better toughness consistency than as-rolled. | 415 | 700 | 16 | 207 HB | — |
Annealed and Cold Drawn | Use when cold-drawn bar must still be headed, bent or heavily machined — softer and more ductile than as-drawn. | 565 | 655 | 12 | 187 HB | — |
Cold drawn | Pick for straight, close-tolerance, bright bar with higher yield strength and better surface finish straight from stock. | 630 | 730 | 10 | 217 HB | — |
Induction hardened | The classic use of 1548: 55–60 HRC martensitic case on journals and splines with a tough Q&T core. | 780 | 950 | 14 | 57 HRC | — |
oil quenched, tempered ~540–590 °C | General-purpose quenched-and-tempered shaft condition balancing strength, toughness and machinability. | 800 | 965 | 16 | 30 HRC | — |
QT40-45HRCThis page oil quenched, tempered ~400–450 °C | High-strength condition for heavily loaded pins, levers and spring-type parts where impact demand is moderate. | 1,180 | 1,350 | 11 | 43 HRC | — |
What is 1548 QT40-45HRC?
1548 QT40-45HRC is 1548 heat treated to QT40-45HRC — high-strength condition for heavily loaded pins, levers and spring-type parts where impact demand is moderate. 1548 QT40-45HRC has a yield strength of 1,180 MPa (171 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Elongation at break is 11% and the elastic modulus is 200 GPa (29 Msi). 1548 QT40-45HRC 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). HR is the default condition FabDigit quotes; QT40-45HRC is available on request or by drawing note.
Advantages
- High strength — 1,180 MPa (171 ksi), better than 94% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High electrical conductivity — 10.5 % IACS, better than 89% of steel grades
- Conducts heat well — 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades
Limitations
- Difficult to weld — 12/100, worse than 96% of steel grades
- Difficult to machine — 25/100, worse than 93% of steel grades
- Limited ductility — 11%, worse than 89% of steel grades
- Low fracture toughness — 50 MPa·√m (45.5 ksi·√in), worse than 86% of steel grades
1548 QT40-45HRC properties
Typical room-temperature values for 1548 QT40-45HRC; 14 are specific to this condition. Other listed values are 1548 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
1548 QT40-45HRC 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
1548 QT40-45HRC has a yield strength of 1,180 MPa (171 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Elongation at break is 11% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
1548 QT40-45HRC is rated for continuous service to 400°C (752 °F). It conducts heat at 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
1548 QT40-45HRC conducts electricity at 10.5 % IACS, better than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 1548 QT40-45HRC 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
1548 QT40-45HRC's machinability is poor (25/100, worse than 93% of steel grades); weldability not recommended (12/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 1548 QT40-45HRC
Is 1548 easy to machine?
Machines like 1045–1050 at ~55 % of 1212; use rigid setups, coated carbide, 120–180 m/min, and prefer annealed or Q&T ≤32 HRC stock for heavy cuts.
Can 1548 be welded?
Carbon equivalent ~0.7 — preheat 250–350 °C, low-hydrogen consumables and immediate stress relief/PWHT; avoid welding on induction-hardened surfaces.
Can 1548 be formed, bent or molded?
Hot forging at 1100–1200 °C is easy; cold bending and heading are limited, so anneal or normalize before severe cold work.
What surface finishes work on 1548?
No natural corrosion protection — specify black oxide, manganese phosphate, zinc plating or paint; hard chrome and nitrocarburizing are common on hardened journals.
1548 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 J403 heat analysis | 0.44 – 0.52 | 0.48 |
| Mnhigh-Mn 15xx series, boosts hardenability | 1.1 – 1.4 | 1.25 |
| P | ≤ 0.04 | 0.02 |
| Smax; 1548 is not a resulfurized free-machining grade | ≤ 0.05 | 0.03 |
| Sitypical for killed bar, not always specified | 0.15 – 0.35 | 0.25 |
| Fe | balance | — |
1548 QT40-45HRC — frequently asked
What is 1548 QT40-45HRC used for?
1548 QT40-45HRC is typically used for automotive axle shafts, steering components, induction-hardened parts and couplings. In short: induction-hardening shaft steel; high hardenability, medium machinability; preheat required for welding.
What is the yield strength of 1548 QT40-45HRC?
1548 QT40-45HRC has a typical yield strength of 1,180 MPa (171 ksi) and a tensile strength of 1,350 MPa (196 ksi) — stronger than 94% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 1548 QT40-45HRC easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of steel grades). Machines like 1045–1050 at ~55 % of 1212; use rigid setups, coated carbide, 120–180 m/min, and prefer annealed or Q&T ≤32 HRC stock for heavy cuts.
Can 1548 QT40-45HRC be welded?
Not readily — weldability is rated not recommended (12/100). Carbon equivalent ~0.7 — preheat 250–350 °C, low-hydrogen consumables and immediate stress relief/PWHT; avoid welding on induction-hardened surfaces.
What surface finishes work on 1548 QT40-45HRC?
No natural corrosion protection — specify black oxide, manganese phosphate, zinc plating or paint; hard chrome and nitrocarburizing are common on hardened journals.
Can 1548 QT40-45HRC be formed, bent or molded?
Hot forging at 1100–1200 °C is easy; cold bending and heading are limited, so anneal or normalize before severe cold work.
What is the maximum service temperature of 1548 QT40-45HRC?
1548 QT40-45HRC 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.
What is the difference between 1548-HR and 1548-IH?
HR is the default condition — lowest-cost stock condition for forged/machined shafts that will later be normalized, Q&T or induction hardened. IH: the classic use of 1548: 55–60 HRC martensitic case on journals and splines with a tough Q&T core. Yield strength is 365 MPa in HR versus 780 MPa in IH.
Sources
- SAE J403 — Chemical Compositions of SAE Carbon Steels — SAE International (2014)
- SAE J1397 — Estimated Mechanical Properties and Machinability of Steel Bars — SAE International (2009)
- 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.4 — Heat Treating — ASM International (1991)
- GB/T 699 — (50Mn comparable grade) — 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.