Steel 5135-QT425
Heat-treated state
AISI/SAE 5135 · UNS G51350
QT425 = q&T 425 °C
High-strength condition (≈38-40 HRC) for gears, spline shafts and high-tensile fasteners.
Values for the QT425 condition
Other 5135 tempers and conditions
5135 is listed in 10 conditions; see the grade overview at 5135.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Softest, most machinable and most formable condition; standard stock for parts that will be Q&T later. | 300 | 570 | 28 | 165 HB | — |
Hot rolled | Cheapest mill condition for parts that will be fully heat treated after machining. | 420 | 700 | 22 | 200 HB | — |
Normalized | Uniform fine-grain structure with moderate strength; good baseline for forgings and for parts not requiring Q&T. | 440 | 740 | 24 | 217 HB | — |
Cold drawn | Close tolerance, bright-finish bar with raised yield strength for shafts and studs used without further heat treatment. | 620 | 720 | 13 | 212 HB | — |
Q&T 650 °C | Softest tempered condition; choose when toughness and machinability outrank strength. | 720 | 850 | 22 | 24 HRC | — |
Q&T 540 °C | Choose oil quenched and tempered at 540 °C (≈30 HRC) for shafts, axles and connecting rods needing the classic strength/toughness balance of 830 MPa yield with 17% elongation. | 830 | 1,010 | 17 | 31 HRC | — |
Induction hardened | Selective surface hardening for journals, spline and gear teeth needing wear resistance over a tough core. | 830 | 1,010 | 15 | 55 HRC | 7.5 % IACS |
QT425This page Q&T 425 °C | High-strength condition (≈38-40 HRC) for gears, spline shafts and high-tensile fasteners. | 1,120 | 1,240 | 15 | 39 HRC | — |
Q&T 315 °C | Very high strength for springs and highly stressed wear parts; ductility still low. | 1,360 | 1,500 | 12 | 45 HRC | — |
Q&T 205 °C | Maximum hardness and wear resistance; use only for lightly loaded, non-impact wear parts. | 1,450 | 1,660 | 10 | 49 HRC | — |
What is 5135-QT425?
5135-QT425 is 5135 heat treated to QT425 — high-strength condition (≈38-40 HRC) for gears, spline shafts and high-tensile fasteners. 5135-QT425 has a yield strength of 1,120 MPa (162 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 93% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi). 5135-QT425 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; QT425 is available on request or by drawing note.
Advantages
- High strength — 1,120 MPa (162 ksi), better than 93% of steel grades
Limitations
- Difficult to machine — 34/100, worse than 86% of steel grades
5135-QT425 properties
Typical room-temperature values for 5135-QT425; 13 are specific to this condition. Other listed values are 5135 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
5135-QT425 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).
Mechanical14
5135-QT425 has a yield strength of 1,120 MPa (162 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 93% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
5135-QT425 is rated for continuous service to 340°C (644 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
5135-QT425 conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 5135-QT425 takes about 27 MJ of energy and emits 2.1 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 30%.
Manufacturability7
5135-QT425's machinability is poor (34/100, worse than 86% of steel grades); weldability fair (48/100); formability fair (50/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 5135-QT425
Is 5135 easy to machine?
Machine in the annealed or ≤32 HRC condition with carbide tooling and rigid setups; expect ~60 % of 1212 speed and grind rather than turn above 45 HRC.
Can 5135 be welded?
Weldable with low-hydrogen consumables but needs 200–320 °C preheat, controlled interpass and immediate stress-relief/temper to avoid martensitic HAZ cracking; weld before hardening where possible.
Can 5135 be formed, bent or molded?
Cold form only in the annealed/spheroidized state with generous bend radii; hot forge 1100–1200 °C, finish above 850 °C and slow-cool or normalize afterwards.
What surface finishes work on 5135?
No anodizing — protect by zinc or hard-chrome plating, phosphate + oil, black oxide or paint; nitriding and induction hardening give excellent wear surfaces.
5135 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 5135 / GB 35Cr | 0.33 – 0.38 | 0.35 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.6 – 0.8 | 0.7 |
| CrGB 35Cr: 0.80–1.10 | 0.8 – 1.05 | 0.95 |
| P | ≤ 0.04 | — |
| Smax; 0.015–0.035 for resulfurized variants | ≤ 0.04 | — |
| Niresidual (GB/T 3077) | ≤ 0.3 | — |
| Curesidual | ≤ 0.25 | — |
| Fe | balance | — |
5135-QT425 — frequently asked
What is 5135-QT425 used for?
5135-QT425 is typically used for gears, shafts, connecting rods, structural forgings and springs. In short: higher-carbon 51xx workhorse; good hardenability and wear; nitriding-friendly chromium steel.
What is the yield strength of 5135-QT425?
5135-QT425 has a typical yield strength of 1,120 MPa (162 ksi) and a tensile strength of 1,240 MPa (180 ksi) — stronger than 93% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 5135-QT425 easy to machine?
Not especially — machinability is rated poor (34/100, worse than 86% of steel grades). Machine in the annealed or ≤32 HRC condition with carbide tooling and rigid setups; expect ~60 % of 1212 speed and grind rather than turn above 45 HRC.
Can 5135-QT425 be welded?
With care — weldability is rated fair (48/100). Weldable with low-hydrogen consumables but needs 200–320 °C preheat, controlled interpass and immediate stress-relief/temper to avoid martensitic HAZ cracking; weld before hardening where possible.
What surface finishes work on 5135-QT425?
No anodizing — protect by zinc or hard-chrome plating, phosphate + oil, black oxide or paint; nitriding and induction hardening give excellent wear surfaces.
Can 5135-QT425 be formed, bent or molded?
Cold form only in the annealed/spheroidized state with generous bend radii; hot forge 1100–1200 °C, finish above 850 °C and slow-cool or normalize afterwards.
What is the maximum service temperature of 5135-QT425?
5135-QT425 is rated for continuous use to about 340°C (644 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 5135-A and 5135-QT205?
A is the default condition — softest, most machinable and most formable condition; standard stock for parts that will be Q&T later. QT205: maximum hardness and wear resistance; use only for lightly loaded, non-impact wear parts. Yield strength is 300 MPa in A versus 1,450 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)
- GB/T 3077 (35Cr) — SAC/ (2015)
- 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)
- 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.