Steel 1139 QT-28-32HRC
Hardness band
AISI/SAE 1139 · UNS G11390
Common through-hardened level for higher-load shafts, pins and threaded fasteners.
Values for the QT-28-32HRC condition
Other 1139 tempers and conditions
1139 is listed in 9 conditions; see the grade overview at 1139.
- HR
- ANN
- NORM
- CD-SR
- CD
- IH
- QT-22-26HRC
- QT-28-32HRC
- QT-34-38HRC
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Hot rolled | Lowest-cost form for parts that will be fully machined or later heat treated. | 345 | 620 | 16 | 11 HRC | 10 % IACS |
Annealed | Softest condition, used before severe machining or when maximum dimensional stability matters. | 345 | 570 | 22 | 8 HRC | 10.5 % IACS |
Normalized | Refines forging/rolling structure and gives uniform mid-range strength before final machining. | 380 | 655 | 20 | 11 HRC | 10 % IACS |
Cold Drawn, Stress Relieved | Choose when heavy asymmetric machining would otherwise cause the part to bow. | 530 | 640 | 14 | 10 HRC | 10 % IACS |
CDDefault Cold drawn | Standard stocked condition: best size tolerance, straightness and chip control for screw-machine work. | 565 | 655 | 12 | 192 HB | — |
Induction hardened | Pick for wear surfaces and bearing journals where the machined core toughness is retained. | 570 | 700 | 11 | 54 HRC | 9.5 % IACS |
oil quenched from ~845 °C, tempered high | Tough, readily machinable strength level for shafts and studs with moderate loading. | 660 | 830 | 17 | 24 HRC | 9.5 % IACS |
QT-28-32HRCThis page oil quenched, tempered ~540 °C | Common through-hardened level for higher-load shafts, pins and threaded fasteners. | 780 | 950 | 15 | 30 HRC | — |
oil quenched, tempered ~455 °C | Highest practical through-hardened level; accept reduced toughness and machinability. | 930 | 1,120 | 12 | 36 HRC | 9 % IACS |
What is 1139 QT-28-32HRC?
1139 QT-28-32HRC is 1139 heat treated to QT-28-32HRC — common through-hardened level for higher-load shafts, pins and threaded fasteners. 1139 QT-28-32HRC has a yield strength of 780 MPa (113 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 86% of steel grades. Elongation at break is 15% and the elastic modulus is 200 GPa (29 Msi). 1139 QT-28-32HRC 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). CD is the default condition FabDigit quotes; QT-28-32HRC is available on request or by drawing note.
Advantages
- Easy to machine — 72/100, better than 97% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High strength — 780 MPa (113 ksi), better than 86% of steel grades
- Conducts heat well — 49 W/m·K (28.3 BTU/hr·ft·°F), better than 83% of steel grades
- High electrical conductivity — 10 % IACS, better than 83% of steel grades
Limitations
- Hard to polish — 40/100, worse than 96% of steel grades
1139 QT-28-32HRC properties
Typical room-temperature values for 1139 QT-28-32HRC; 10 are specific to this condition. Other listed values are 1139 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
1139 QT-28-32HRC 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).
Mechanical13
1139 QT-28-32HRC has a yield strength of 780 MPa (113 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 86% of steel grades. Elongation at break is 15% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
1139 QT-28-32HRC 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
1139 QT-28-32HRC conducts electricity at 10 % IACS, better than 83% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 1139 QT-28-32HRC 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
1139 QT-28-32HRC's machinability is very good (72/100, better than 97% of steel grades); weldability poor (30/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 1139 QT-28-32HRC
Is 1139 easy to machine?
Excellent chip breaking from MnS; run 20–30% higher surface speed than 1045, carbide inserts, positive rake, light sulfurized oil or coolant.
Can 1139 be welded?
Not recommended for structural welds — high S plus ~0.40 C promotes hot cracking and hard HAZ; if welded, preheat 200–300 °C, low-hydrogen consumables and post-weld stress relief.
Can 1139 be formed, bent or molded?
Poor cold formability, especially transverse; hot forge 1150–1230 °C and finish above 900 °C, then normalize.
What surface finishes work on 1139?
No anodizing; protect with zinc or zinc-nickel plating, black oxide, phosphate-and-oil, or paint. Sulfide stringers limit mirror polish and can leave micro-pits after plating.
1139 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 / ASTM A29 heat analysis | 0.35 – 0.43 | 0.39 |
| Mn | 1.35 – 1.65 | 1.5 |
| P | ≤ 0.04 | 0.02 |
| Sresulfurized for machinability | 0.13 – 0.2 | 0.16 |
| Sinot normally specified for resulfurized grades | ≤ 0.1 | 0.05 |
| Fe | balance | — |
1139 QT-28-32HRC — frequently asked
What is 1139 QT-28-32HRC used for?
1139 QT-28-32HRC is typically used for shafts, studs and bolts. In short: free-machining 1140 equivalent; heat-treatable to 38 HRC; poor weldability by design.
What is the yield strength of 1139 QT-28-32HRC?
1139 QT-28-32HRC has a typical yield strength of 780 MPa (113 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 86% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is 1139 QT-28-32HRC easy to machine?
Yes — machinability is rated very good (72/100, better than 97% of steel grades). Excellent chip breaking from MnS; run 20–30% higher surface speed than 1045, carbide inserts, positive rake, light sulfurized oil or coolant.
Can 1139 QT-28-32HRC be welded?
Not readily — weldability is rated poor (30/100). Not recommended for structural welds — high S plus ~0.40 C promotes hot cracking and hard HAZ; if welded, preheat 200–300 °C, low-hydrogen consumables and post-weld stress relief.
What surface finishes work on 1139 QT-28-32HRC?
No anodizing; protect with zinc or zinc-nickel plating, black oxide, phosphate-and-oil, or paint. Sulfide stringers limit mirror polish and can leave micro-pits after plating.
Can 1139 QT-28-32HRC be formed, bent or molded?
Poor cold formability, especially transverse; hot forge 1150–1230 °C and finish above 900 °C, then normalize.
What is the maximum service temperature of 1139 QT-28-32HRC?
1139 QT-28-32HRC 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 1139-CD and 1139-HR?
CD is the default condition — standard stocked condition: best size tolerance, straightness and chip control for screw-machine work. HR: lowest-cost form for parts that will be fully machined or later heat treated. Yield strength is 565 MPa in CD versus 345 MPa in HR.
Sources
- SAE J403 — Chemical Compositions of SAE Carbon Steels — SAE International (2014)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought, General Requirements — ASTM (2020)
- ASTM A108 — Steel Bar, Carbon and Alloy, Cold-Finished — ASTM (2018)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.16 — Machining — ASM International (1989)
- GB/T 8731 (Y40Mn comparable grade) — SAC (2008)
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.