Steel 15 CARB
Heat-treated state
CARB = carburized 900–930 °C, quenched + 180 °C temper
The main reason to use grade 15: hard wear-resistant case (58–62 HRC) over a tough, soft, unhardened core.
Values for the CARB condition
Other 15 tempers and conditions
15 is listed in 7 conditions; see the grade overview at 15.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
HRDefault Hot rolled | Cheapest, most-stocked condition for welded structures and parts that will be carburized or machined afterwards. | 245 | 400 | 30 | 111 HB | — |
Cold rolled | Thin sheet and strip for stamped brackets, washers and deep-drawn cups needing a clean bright surface. | 260 | 380 | 30 | 115 HB | 10.8 % IACS |
Normalized | Standard GB/T 699 test condition; use for uniform fine grain, best toughness and predictable machining before carburizing. | 265 | 425 | 34 | 121 HB | — |
Solution annealed | Softest condition — pick it for maximum ductility in deep drawing or heavy cold forming. | 284 | 386 | 37 | 111 HB | — |
Cold drawn | Choose for bright straight bar with tight tolerance, higher yield and better chip control on automatic lathes. | 350 | 420 | 18 | 126 HB | — |
CARBThis page Carburized 900–930 °C, quenched + 180 °C temper | The main reason to use grade 15: hard wear-resistant case (58–62 HRC) over a tough, soft, unhardened core. | 350 | 500 | 15 | 60 HRC | — |
Water quenched (~900 °C) and tempered ~200 °C | Thin sections only — gives a modest strength bump when carburizing is not wanted; hardenability is very low. | 400 | 550 | 20 | 10 HRC | 10.2 % IACS |
What is 15 CARB?
15 CARB is 15 heat treated to CARB — the main reason to use grade 15: hard wear-resistant case (58–62 HRC) over a tough, soft, unhardened core. 15 CARB has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 74% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi). 15 CARB has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,465°C (2,669 °F). HR is the default condition FabDigit quotes; CARB is available on request or by drawing note.
Advantages
- Forms and bends easily — 85/100, better than 96% of steel grades
- High electrical conductivity — 10.8 % IACS, better than 94% of steel grades
- Conducts heat well — 51 W/m·K (29.5 BTU/hr·ft·°F), better than 92% of steel grades
- Tough — resists crack growth — 130 MPa·√m (118.3 ksi·√in), better than 89% of steel grades
Limitations
- Difficult to machine — 12/100, worse than 99% of steel grades
- Hard to polish — 45/100, worse than 84% of steel grades
15 CARB properties
Typical room-temperature values for 15 CARB; 10 are specific to this condition. Other listed values are 15 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
15 CARB has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,465°C (2,669 °F).
Mechanical16
15 CARB has a yield strength of 350 MPa (50.8 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 74% of steel grades. Elongation at break is 15% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
15 CARB is rated for continuous service to 400°C (752 °F). It conducts heat at 51 W/m·K (29.5 BTU/hr·ft·°F), better than 92% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
15 CARB conducts electricity at 10.8 % IACS, better than 94% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of 15 CARB takes about 25 MJ of energy and emits 2.1 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 25%.
Manufacturability6
15 CARB's machinability is not recommended (12/100, worse than 99% of steel grades); weldability poor (30/100); formability excellent (85/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 15 CARB
Is 15 easy to machine?
Gummy and prone to built-up edge — run sharp positive-rake tools, high speed, generous coolant; normalizing or cold drawing before machining greatly improves surface finish.
Can 15 be welded?
Excellent — CE ≈ 0.25, weldable by SMAW/GMAW/TIG/spot with E43xx (E6013/E7018) filler, no preheat or PWHT required in normal thicknesses.
Can 15 be formed, bent or molded?
Very good cold formability: deep drawing, bending to tight radii (≈1t) and cold heading are all routine; hot forming at 850–1150 °C.
What surface finishes work on 15?
No natural corrosion protection — specify zinc/nickel plating, hot-dip galvanizing, phosphating, black oxide or paint; polishes only to a modest finish because of the soft ferrite matrix.
15 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 |
|---|---|---|
| CGB/T 699-2015 grade 15 | 0.12 – 0.19 | 0.15 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.35 – 0.65 | 0.5 |
| P≤0.030 for high-grade (A) quality | ≤ 0.04 | 0.02 |
| S≤0.030 for high-grade (A) quality | ≤ 0.04 | 0.02 |
| Crresidual | ≤ 0.25 | 0.1 |
| Niresidual | ≤ 0.3 | 0.1 |
| Curesidual | ≤ 0.25 | 0.1 |
| Fe | balance | — |
15 CARB — frequently asked
What is 15 CARB used for?
15 CARB is typically used for carburized shafts, bolts, pins and light structural components. In short: carburizing-grade low-carbon steel; SAE 1015 equivalent; excellent cold-heading formability.
What is the yield strength of 15 CARB?
15 CARB has a typical yield strength of 350 MPa (50.8 ksi) and a tensile strength of 500 MPa (72.5 ksi) — weaker than 74% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 15 CARB easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 99% of steel grades). Gummy and prone to built-up edge — run sharp positive-rake tools, high speed, generous coolant; normalizing or cold drawing before machining greatly improves surface finish.
Can 15 CARB be welded?
Not readily — weldability is rated poor (30/100). Excellent — CE ≈ 0.25, weldable by SMAW/GMAW/TIG/spot with E43xx (E6013/E7018) filler, no preheat or PWHT required in normal thicknesses.
What surface finishes work on 15 CARB?
No natural corrosion protection — specify zinc/nickel plating, hot-dip galvanizing, phosphating, black oxide or paint; polishes only to a modest finish because of the soft ferrite matrix.
Can 15 CARB be formed, bent or molded?
Very good cold formability: deep drawing, bending to tight radii (≈1t) and cold heading are all routine; hot forming at 850–1150 °C.
What is the maximum service temperature of 15 CARB?
15 CARB is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 15-HR and 15-WQT?
HR is the default condition — cheapest, most-stocked condition for welded structures and parts that will be carburized or machined afterwards. WQT: thin sections only — gives a modest strength bump when carburizing is not wanted; hardenability is very low. Yield strength is 245 MPa in HR versus 400 MPa in WQT.
Sources
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- SAE J403 — Chemical Compositions of SAE Carbon Steels — SAE International (2014)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- 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.