Steel 4161-QT315
Heat-treated state
AISI/SAE 4161 · UNS G41610
QT315 = q&T 315 °C
Very high strength for heavily loaded springs and torsion bars where some ductility is still needed.
Values for the QT315 condition
Other 4161 tempers and conditions
4161 is listed in 10 conditions; see the grade overview at 4161.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose for cold heading, deep drawing or heavy cold forming of this high-carbon grade. | 390 | 700 | 22 | 11 HRC | 8.1 % IACS |
ADefault Solution annealed | Softest supply condition for machining, cold forming and subsequent hardening by the user. | 415 | 760 | 18 | 217 HB | — |
Hot rolled | Lowest-cost mill condition for spring blanks and forging stock that will be heat treated afterwards. | 550 | 900 | 14 | 26 HRC | 7.8 % IACS |
Normalized | Uniform fine pearlitic structure for forgings prior to machining or hardening; higher strength than annealed. | 700 | 1,080 | 12 | 34 HRC | — |
Cold drawn | Bright, close-tolerance bar with raised yield strength for shafts machined without further heat treatment. | 760 | 900 | 10 | 26 HRC | 7.8 % IACS |
Q&T 650 °C | Softest Q&T condition — maximum ductility and machinability while retaining tempered-martensite structure. | 895 | 965 | 18 | 30 HRC | — |
Q&T 540 °C | Tough quenched-and-tempered condition for shock-loaded shafts and machined high-strength parts. | 1,145 | 1,240 | 14 | 38 HRC | — |
Q&T 425 °C | Typical leaf/coil spring and heavy shaft condition — best balance of fatigue strength and toughness. | 1,415 | 1,550 | 11 | 45 HRC | — |
QT315This page Q&T 315 °C | Very high strength for heavily loaded springs and torsion bars where some ductility is still needed. | 1,620 | 1,855 | 8 | 53 HRC | — |
Q&T 205 °C | Maximum hardness and strength for wear-critical tooling; very low toughness, avoid notches and impact. | 1,725 | 2,035 | 6 | 57 HRC | — |
What is 4161-QT315?
4161-QT315 is 4161 heat treated to QT315 — very high strength for heavily loaded springs and torsion bars where some ductility is still needed. 4161-QT315 has a yield strength of 1,620 MPa (235 ksi) and a tensile strength of 1,855 MPa (269 ksi) — stronger than 98% of steel grades. Elongation at break is 8% and the elastic modulus is 205 GPa (29.7 Msi). 4161-QT315 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F). A is the default condition FabDigit quotes; QT315 is available on request or by drawing note.
Advantages
- High strength — 1,620 MPa (235 ksi), better than 98% of steel grades
Limitations
- Difficult to machine — 20/100, worse than 97% of steel grades
- Limited ductility — 8%, worse than 95% of steel grades
- Low fracture toughness — 33 MPa·√m (30 ksi·√in), worse than 95% of steel grades
- Limited service temperature — 250°C (482 °F), worse than 85% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
4161-QT315 properties
Typical room-temperature values for 4161-QT315; 13 are specific to this condition. Other listed values are 4161 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
4161-QT315 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F).
Mechanical16
4161-QT315 has a yield strength of 1,620 MPa (235 ksi) and a tensile strength of 1,855 MPa (269 ksi) — stronger than 98% of steel grades. Elongation at break is 8% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4161-QT315 is rated for continuous service to 250°C (482 °F). It conducts heat at 42.7 W/m·K (24.7 BTU/hr·ft·°F), better than 50% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
4161-QT315 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 4161-QT315 takes about 30 MJ of energy and emits 2.2 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
4161-QT315's machinability is poor (20/100, worse than 97% of steel grades); weldability poor (20/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4161-QT315
Is 4161 easy to machine?
Machine in the annealed/spheroidized state (~55 % of 1212); above 40 HRC use carbide or CBN with rigid setups, or finish by grinding.
Can 4161 be welded?
Poor weldability — CE ≈ 0.95; if unavoidable, preheat 300–350 °C, use low-hydrogen consumables and temper immediately after welding.
Can 4161 be formed, bent or molded?
Cold form only in spheroidize-annealed condition with generous radii; hot forge 1100–1200 °C and always normalize/anneal afterwards; oil quench from 830–860 °C and temper at once to avoid quench cracking.
What surface finishes work on 4161?
No anodizing; use black oxide, manganese phosphate + oil, zinc or Cr plating (bake 190 °C ≥4 h after plating to avoid hydrogen embrittlement); shot peening greatly boosts spring fatigue life.
4161 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 |
|---|---|---|
| Chighest carbon of the 41xx family | 0.56 – 0.64 | 0.6 |
| Mn | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| Cr | 0.7 – 0.9 | 0.8 |
| Mo | 0.25 – 0.35 | 0.3 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
4161-QT315 — frequently asked
What is 4161-QT315 used for?
4161-QT315 is typically used for heavy springs, high-strength shafts and gears. In short: highest-carbon 41xx grade; spring-strength Cr-Mo steel; very limited weldability.
What is the yield strength of 4161-QT315?
4161-QT315 has a typical yield strength of 1,620 MPa (235 ksi) and a tensile strength of 1,855 MPa (269 ksi) — stronger than 98% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 4161-QT315 easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of steel grades). Machine in the annealed/spheroidized state (~55 % of 1212); above 40 HRC use carbide or CBN with rigid setups, or finish by grinding.
Can 4161-QT315 be welded?
Not readily — weldability is rated poor (20/100). Poor weldability — CE ≈ 0.95; if unavoidable, preheat 300–350 °C, use low-hydrogen consumables and temper immediately after welding.
What surface finishes work on 4161-QT315?
No anodizing; use black oxide, manganese phosphate + oil, zinc or Cr plating (bake 190 °C ≥4 h after plating to avoid hydrogen embrittlement); shot peening greatly boosts spring fatigue life.
Can 4161-QT315 be formed, bent or molded?
Cold form only in spheroidize-annealed condition with generous radii; hot forge 1100–1200 °C and always normalize/anneal afterwards; oil quench from 830–860 °C and temper at once to avoid quench cracking.
What is the maximum service temperature of 4161-QT315?
4161-QT315 is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 4161-A and 4161-QT205?
A is the default condition — softest supply condition for machining, cold forming and subsequent hardening by the user. QT205: maximum hardness and strength for wear-critical tooling; very low toughness, avoid notches and impact. Yield strength is 415 MPa in A versus 1,725 MPa in QT205.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 — Hardenability Bands for Carbon and Alloy H Steels — SAE International (2019)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM International (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)
- ASM Handbook Vol.16 — Machining — ASM International (1989)
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.