Steel 8655-QT425
Heat-treated state
AISI/SAE 8655 · UNS G86550
QT425 = q&T 425 °C
Balanced strength/toughness for highly stressed shafts, pins and springs.
Values for the QT425 condition
Other 8655 tempers and conditions
8655 is listed in 11 conditions; see the grade overview at 8655.
Compare all 11 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose for maximum softness/ductility before cold heading, deep machining or severe forming of this high-carbon grade. | 380 | 690 | 25 | 13 HRC | 8 % IACS |
ADefault Solution annealed | Softest condition — the usual bar stock form for machining before hardening. | 400 | 750 | 21 | 223 HB | — |
Hot rolled | Lowest-cost mill form for parts that will be fully heat treated after rough machining. | 520 | 900 | 16 | 26 HRC | 7.8 % IACS |
Normalized | Use to refine grain and homogenize forgings before final quench and temper. | 710 | 1,080 | 13 | 33 HRC | — |
Cold drawn | Pick for tight size tolerance and straight, bright bar with higher as-supplied strength. | 720 | 860 | 10 | 25 HRC | 7.8 % IACS |
Q&T 650 °C | Softest Q&T condition — best ductility and machinability while keeping tempered-martensite structure. | 915 | 1,020 | 19 | 29 HRC | — |
induction hardened and tempered surface | Use when a hard wear surface (55–60 HRC case) is needed over a tougher Q&T core. | 1,080 | 1,250 | 10 | 57 HRC | 7.4 % IACS |
Q&T 540 °C | General-purpose quenched-and-tempered condition where impact toughness matters more than wear. | 1,140 | 1,250 | 15 | 35 HRC | — |
QT425This page Q&T 425 °C | Balanced strength/toughness for highly stressed shafts, pins and springs. | 1,420 | 1,550 | 12 | 43 HRC | — |
Q&T 315 °C | Very high strength with slightly better toughness than the 205 °C temper; typical for wear plates and dies. | 1,620 | 1,830 | 10 | 50 HRC | — |
Q&T 205 °C | Maximum hardness and wear resistance; use only where impact loading is low. | 1,700 | 2,000 | 9 | 55 HRC | 41 W/m·K |
What is 8655-QT425?
8655-QT425 is 8655 heat treated to QT425 — balanced strength/toughness for highly stressed shafts, pins and springs. 8655-QT425 has a yield strength of 1,420 MPa (206 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 96% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi). 8655-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 — 1,420 MPa (206 ksi), better than 96% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to machine — 28/100, worse than 91% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
- Low fracture toughness — 65 MPa·√m (59.2 ksi·√in), worse than 75% of steel grades
8655-QT425 properties
Typical room-temperature values for 8655-QT425; 13 are specific to this condition. Other listed values are 8655 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
8655-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).
Mechanical16
8655-QT425 has a yield strength of 1,420 MPa (206 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 96% of steel grades. Elongation at break is 12% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
8655-QT425 is rated for continuous service to 350°C (662 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
8655-QT425 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 8655-QT425 takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
8655-QT425's machinability is poor (28/100, worse than 91% of steel grades); weldability poor (20/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 8655-QT425
Is 8655 easy to machine?
Machine in the annealed or spheroidized state with rigid setups and carbide tooling; above ~40 HRC switch to CBN/ceramic or grinding.
Can 8655 be welded?
Poor weldability (CE ≈ 1.0) — preheat 250–350 °C, low-hydrogen consumables and immediate post-weld temper are required; avoid welding on hardened parts.
Can 8655 be formed, bent or molded?
Hot forge 1100–1200 °C and cool slowly to avoid cracking; cold forming limited to gentle bends in the spheroidized condition.
What surface finishes work on 8655?
No anodizing; protect with black oxide, phosphate-and-oil, zinc or hard chrome, and bake after plating to avoid hydrogen embrittlement at high hardness.
8655 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 J404 / ASTM A29 grade 8655 | 0.5 – 0.6 | 0.55 |
| Mn | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| Ni | 0.4 – 0.7 | 0.55 |
| Cr | 0.4 – 0.6 | 0.5 |
| Mo | 0.15 – 0.25 | 0.2 |
| P | ≤ 0.04 | — |
| S | ≤ 0.04 | — |
| Fe | balance | — |
8655-QT425 — frequently asked
What is 8655-QT425 used for?
8655-QT425 is typically used for high-strength bolts, springs, wear parts and heavy-duty gears. In short: highest-carbon 86xx grade; through-hardening wear steel; poor weldability, hot-form only.
What is the yield strength of 8655-QT425?
8655-QT425 has a typical yield strength of 1,420 MPa (206 ksi) and a tensile strength of 1,550 MPa (225 ksi) — stronger than 96% of steel grades. Strength varies by condition: see the 11 listed tempers.
Is 8655-QT425 easy to machine?
Not especially — machinability is rated poor (28/100, worse than 91% of steel grades). Machine in the annealed or spheroidized state with rigid setups and carbide tooling; above ~40 HRC switch to CBN/ceramic or grinding.
Can 8655-QT425 be welded?
Not readily — weldability is rated poor (20/100). Poor weldability (CE ≈ 1.0) — preheat 250–350 °C, low-hydrogen consumables and immediate post-weld temper are required; avoid welding on hardened parts.
What surface finishes work on 8655-QT425?
No anodizing; protect with black oxide, phosphate-and-oil, zinc or hard chrome, and bake after plating to avoid hydrogen embrittlement at high hardness.
Can 8655-QT425 be formed, bent or molded?
Hot forge 1100–1200 °C and cool slowly to avoid cracking; cold forming limited to gentle bends in the spheroidized condition.
What is the maximum service temperature of 8655-QT425?
8655-QT425 is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 8655-A and 8655-QT205?
A is the default condition — softest condition — the usual bar stock form for machining before hardening. QT205: maximum hardness and wear resistance; use only where impact loading is low. Yield strength is 400 MPa in A versus 1,700 MPa in QT205.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- SAE J1268 — Hardenability Bands for Carbon and Alloy H Steels — SAE International (2019)
- 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.