Steel SUM32 CARB-QT
Heat-treated state
JIS SUM32
CARB-QT = carburized, Quenched & Tempered
Use when the machined part needs a wear-resistant case (~0.3–1.0 mm) over a tough low-carbon core.
Values for the CARB-QT condition
Other SUM32 tempers and conditions
SUM32 is listed in 6 conditions; see the grade overview at SUM32.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Hot rolled | Cheapest form for large-section parts that will be fully machined or subsequently heat treated. | 235 | 425 | 33 | 121 HB | — |
Solution annealed | Softest condition for heavy cold heading, deep boring or before carburizing. | 285 | 430 | 33 | 121 HB | 10.8 % IACS |
Normalized | Uniform fine grain and better toughness/consistency before machining or case hardening. | 303 | 467 | 33.5 | 121 HB | 10.5 % IACS |
Cold Drawn + Stress Relieved | Choose when parts must stay straight after asymmetric machining of cold-drawn bar. | 395 | 470 | 18 | 143 HB | 10.5 % IACS |
CDDefault Cold drawn | Standard stocked condition for screw-machine work: good size tolerance, straightness and chip control. | 415 | 485 | 15 | 143 HB | — |
CARB-QTThis page Carburized, Quenched & Tempered | Use when the machined part needs a wear-resistant case (~0.3–1.0 mm) over a tough low-carbon core. | 420 | 640 | 15 | 60 HRC | — |
What is SUM32 CARB-QT?
SUM32 CARB-QT is SUM32 heat treated to CARB-QT — use when the machined part needs a wear-resistant case (~0.3–1.0 mm) over a tough low-carbon core. SUM32 CARB-QT has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 640 MPa (92.8 ksi) — weaker than 53% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi). SUM32 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). CD is the default condition FabDigit quotes; CARB-QT is available on request or by drawing note.
Advantages
- Conducts heat well — 51.9 W/m·K (30 BTU/hr·ft·°F), better than 96% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High electrical conductivity — 10.5 % IACS, better than 89% of steel grades
Limitations
- Hard to polish — 40/100, worse than 96% of steel grades
- Difficult to machine — 25/100, worse than 93% of steel grades
SUM32 CARB-QT properties
Typical room-temperature values for SUM32 CARB-QT; 10 are specific to this condition. Other listed values are SUM32 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
SUM32 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).
Mechanical13
SUM32 CARB-QT has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 640 MPa (92.8 ksi) — weaker than 53% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
SUM32 CARB-QT is rated for continuous service to 350°C (662 °F). It conducts heat at 51.9 W/m·K (30 BTU/hr·ft·°F), better than 96% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
SUM32 CARB-QT conducts electricity at 10.5 % IACS, better than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of SUM32 CARB-QT takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability7
SUM32 CARB-QT's machinability is poor (25/100, worse than 93% of steel grades); weldability fair (40/100); formability fair (40/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with SUM32 CARB-QT
Is SUM32 easy to machine?
Excellent — ~90 % of 1212; MnS breaks chips and lubricates the cutting edge, allowing high feeds on CNC lathes with standard carbide.
Can SUM32 be welded?
Marginal — high sulfur invites hot cracking and porosity; if unavoidable use low-hydrogen filler, preheat 100–150 °C and low heat input, and avoid highly restrained joints.
Can SUM32 be formed, bent or molded?
Only light cold bending/heading; sulfide stringers cut transverse ductility, so hot form above 900 °C for severe shapes.
What surface finishes work on SUM32?
No anodizing; protect with black oxide, zinc phosphate, zinc or electroless nickel plating — inclusions can leave micro-pits after polishing or plating.
SUM32 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 |
|---|---|---|
| CJIS G4804 free-cutting steel | 0.12 – 0.2 | 0.16 |
| MnAISI 1117 counterpart runs 1.00–1.30 | 0.6 – 1.1 | 0.9 |
| P | ≤ 0.04 | 0.03 |
| SMnS inclusions give the free-cutting behaviour | 0.1 – 0.2 | 0.15 |
| Sinot normally specified; usually low (rimmed/semi-killed practice) | ≤ 0.1 | 0.05 |
| Fe | balance | — |
SUM32 CARB-QT — frequently asked
What is SUM32 CARB-QT used for?
SUM32 CARB-QT is typically used for gears, shafts and bushings. In short: case-hardenable free-cutting steel; about 90 % of 1212; better formability than SUM41.
What is the yield strength of SUM32 CARB-QT?
SUM32 CARB-QT has a typical yield strength of 420 MPa (60.9 ksi) and a tensile strength of 640 MPa (92.8 ksi) — weaker than 53% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is SUM32 CARB-QT easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of steel grades). Excellent — ~90 % of 1212; MnS breaks chips and lubricates the cutting edge, allowing high feeds on CNC lathes with standard carbide.
Can SUM32 CARB-QT be welded?
With care — weldability is rated fair (40/100). Marginal — high sulfur invites hot cracking and porosity; if unavoidable use low-hydrogen filler, preheat 100–150 °C and low heat input, and avoid highly restrained joints.
What surface finishes work on SUM32 CARB-QT?
No anodizing; protect with black oxide, zinc phosphate, zinc or electroless nickel plating — inclusions can leave micro-pits after polishing or plating.
Can SUM32 CARB-QT be formed, bent or molded?
Only light cold bending/heading; sulfide stringers cut transverse ductility, so hot form above 900 °C for severe shapes.
What is the maximum service temperature of SUM32 CARB-QT?
SUM32 CARB-QT 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 SUM32-CD and SUM32-HR?
CD is the default condition — standard stocked condition for screw-machine work: good size tolerance, straightness and chip control. HR: cheapest form for large-section parts that will be fully machined or subsequently heat treated. Yield strength is 415 MPa in CD versus 235 MPa in HR.
Sources
- JIS G 4804 Sulfur and sulfur-composite free-cutting steels — JSA (2019)
- ASTM A29/A29M Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.13B — Corrosion: Materials — ASM International (2005)
- SAE/AISI machinability ratings for carbon steels — SAE International (2017)
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.