Steel SCr415 CARB-QT
Heat-treated state
JIS SCr415
CARB-QT = carburized, quenched and tempered
The service condition for gears and splines: 0.6–1.2 mm effective case at 58–62 HRC over a tough core.
Values for the CARB-QT condition
Other SCr415 tempers and conditions
SCr415 is listed in 8 conditions; see the grade overview at SCr415.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose for cold-headed or cold-extruded gear and fastener blanks needing maximum ductility. | 300 | 480 | 31 | 140 HB | 8 % IACS |
ADefault Solution annealed | Standard stocked condition: soft and dimensionally stable for machining gear blanks before carburizing. | 340 | 540 | 26 | 160 HB | — |
Hot rolled | Cheapest mill condition for bar that will be forged or fully heat treated afterwards. | 400 | 600 | 21 | 180 HB | — |
Normalized | Used to refine forging structure and give uniform grain size before carburizing. | 420 | 620 | 23 | 180 HB | 7.8 % IACS |
Carbonitrided and tempered | Use for small, low-load gears, washers and levers where a 0.1–0.4 mm hard, wear-resistant case is enough. | 520 | 750 | 18 | 59 HRC | 7.5 % IACS |
Cold drawn | Pick for close-tolerance bright bar for pins, shafts and small gear blanks with minimal turning. | 580 | 710 | 12 | 210 HB | — |
CARB-QTThis page Carburized, quenched and tempered | The service condition for gears and splines: 0.6–1.2 mm effective case at 58–62 HRC over a tough core. | 640 | 900 | 17 | 60 HRC | — |
Quenched and tempered | For small, thin parts that need a hard through-section rather than a carburized case. | 760 | 1,000 | 13 | 32 HRC | — |
What is SCr415 CARB-QT?
SCr415 CARB-QT is SCr415 heat treated to CARB-QT — the service condition for gears and splines: 0.6–1.2 mm effective case at 58–62 HRC over a tough core. SCr415 CARB-QT has a yield strength of 640 MPa (92.8 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 79% of steel grades. Elongation at break is 17% and the elastic modulus is 206 GPa (29.9 Msi). SCr415 CARB-QT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). A is the default condition FabDigit quotes; CARB-QT is available on request or by drawing note.
Advantages
- High strength — 640 MPa (92.8 ksi), better than 79% of steel grades
Limitations
- Difficult to machine — 12/100, worse than 99% of steel grades
- Difficult to weld — 10/100, worse than 99% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
- Limited service temperature — 180°C (356 °F), worse than 98% of steel grades
- Low fracture toughness — 60 MPa·√m (54.6 ksi·√in), worse than 78% of steel grades
SCr415 CARB-QT properties
Typical room-temperature values for SCr415 CARB-QT; 16 are specific to this condition. Other listed values are SCr415 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SCr415 CARB-QT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical15
SCr415 CARB-QT has a yield strength of 640 MPa (92.8 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 79% of steel grades. Elongation at break is 17% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
SCr415 CARB-QT is rated for continuous service to 180°C (356 °F). It conducts heat at 44 W/m·K (25.4 BTU/hr·ft·°F), better than 57% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
SCr415 CARB-QT conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of SCr415 CARB-QT takes about 27 MJ of energy and emits 2 kg of CO₂ — less than 59% of steel grades. Typical recycled content is 30%.
Manufacturability7
SCr415 CARB-QT's machinability is not recommended (12/100, worse than 99% of steel grades); weldability not recommended (10/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SCr415 CARB-QT
Is SCr415 easy to machine?
Machine soft (annealed 143–187 HB) with carbide or HSS at ~65 % of 1212 rates; leave 0.1–0.3 mm stock for post-carburizing grinding since the 60 HRC case needs CBN/grinding.
Can SCr415 be welded?
Weldable in the soft condition with low-hydrogen consumables, 150–250 °C preheat and post-weld stress relief; do not weld carburized surfaces (cracking and case softening).
Can SCr415 be formed, bent or molded?
Good hot forgeability at 1100–1200 °C; cold heading and extrusion practical after spheroidize annealing plus phosphate/soap lubrication; normalize before carburizing to control distortion.
What surface finishes work on SCr415?
No anodizing (ferrous) — protect with oil, manganese phosphate, black oxide, or zinc/nickel plating (bake to avoid hydrogen embrittlement of the hardened case); ground and shot-peened gear flanks give best fatigue life.
SCr415 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 |
|---|---|---|
| C | 0.13 – 0.18 | 0.15 |
| Si | 0.15 – 0.35 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | — |
| S | ≤ 0.03 | — |
| Cr | 0.9 – 1.2 | 1.05 |
| Niresidual, max | ≤ 0.25 | — |
| Curesidual, max | ≤ 0.3 | — |
| Fe | balance | — |
SCr415 CARB-QT — frequently asked
What is SCr415 CARB-QT used for?
SCr415 CARB-QT is typically used for carburized gears, shafts and pins. In short: entry-level carburizing chrome steel; good soft-state machinability; 5115 / 15Cr equivalent.
What is the yield strength of SCr415 CARB-QT?
SCr415 CARB-QT has a typical yield strength of 640 MPa (92.8 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 79% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is SCr415 CARB-QT easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 99% of steel grades). Machine soft (annealed 143–187 HB) with carbide or HSS at ~65 % of 1212 rates; leave 0.1–0.3 mm stock for post-carburizing grinding since the 60 HRC case needs CBN/grinding.
Can SCr415 CARB-QT be welded?
Not readily — weldability is rated not recommended (10/100). Weldable in the soft condition with low-hydrogen consumables, 150–250 °C preheat and post-weld stress relief; do not weld carburized surfaces (cracking and case softening).
What surface finishes work on SCr415 CARB-QT?
No anodizing (ferrous) — protect with oil, manganese phosphate, black oxide, or zinc/nickel plating (bake to avoid hydrogen embrittlement of the hardened case); ground and shot-peened gear flanks give best fatigue life.
Can SCr415 CARB-QT be formed, bent or molded?
Good hot forgeability at 1100–1200 °C; cold heading and extrusion practical after spheroidize annealing plus phosphate/soap lubrication; normalize before carburizing to control distortion.
What is the maximum service temperature of SCr415 CARB-QT?
SCr415 CARB-QT is rated for continuous use to about 180°C (356 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between SCr415-A and SCr415-QT?
A is the default condition — standard stocked condition: soft and dimensionally stable for machining gear blanks before carburizing. QT: for small, thin parts that need a hard through-section rather than a carburized case. Yield strength is 340 MPa in A versus 760 MPa in QT.
Sources
- JIS G 4053 — Low-alloyed steels for machine structural use — JISC (2016)
- GB/T 3077 — Alloy structural steels (15Cr) — SAC (2015)
- SAE J404 / ASTM A29 (5115 chemical limits) — SAE / ASTM (2020)
- 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 (carburizing) — 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.