Steel 20# · heat-treated state
Steel 20# CARB
Properties of the CARB condition, compared with the other 20# tempers.
Choose for small gears, cams, bushings and wear pins needing a 0.3–1.2 mm hard case over a tough low-carbon core.
What is 20# CARB?
20# CARB is 20# heat treated to CARB — choose for small gears, cams, bushings and wear pins needing a 0.3–1.2 mm hard case over a tough low-carbon core. 20# CARB has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 640 MPa (92.8 ksi) — stronger than 53% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi). 20# CARB has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,495°C (2,723 °F). CD is the default condition FabDigit quotes; CARB is available on request or by drawing note.
Advantages
- 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
Limitations
- Difficult to machine — 12/100, worse than 99% of steel grades
- Limited ductility — 12%, worse than 84% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
20# CARB properties
Typical room-temperature values for 20# CARB — 10 properties are specific to this condition; the rest are grade-level values shared by every 20# temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
20# CARB has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,495°C (2,723 °F).
Mechanical14
20# CARB has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 640 MPa (92.8 ksi) — stronger than 53% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
20# CARB is rated for continuous service to 425°C (797 °F). It conducts heat at 51 W/m·K (29.5 BTU/hr·ft·°F), better than 92% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical3
20# CARB conducts electricity at 10.8 % IACS, better than 94% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 87% of steel grades.
Sustainability4
Producing a kilogram of 20# 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%.
Manufacturability8
20# CARB's machinability is not recommended (12/100, worse than 99% of steel grades); weldability poor (25/100); formability good (60/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 20# tempers and conditions
20# is also supplied in 5 other conditions. The full side-by-side table is on the 20# overview.
- CDDefaultDefault stock condition for small round bar, shafting and precision tube; best dimensional accuracy, surface finish and machinability.395 MPa yield · 160 HB
- CARBChoose for small gears, cams, bushings and wear pins needing a 0.3–1.2 mm hard case over a tough low-carbon core.450 MPa yield · 59 HRC
- QTUsed on small pins and fasteners where a modest strength lift is wanted; hardenability is poor, so section size must stay under ~15 mm.430 MPa yield · 14 HRC
- NStandard reference condition of GB/T 699 test bars; uniform fine grain, best toughness/strength balance for pressure parts.275 MPa yield · 140 HB
- HRCheapest form for welded structures, flanges and machined parts where scale and looser tolerance are acceptable.265 MPa yield · 145 HB
- ASoftest condition — pick for deep drawing, severe cold forming or stress relief before carburizing.250 MPa yield · 121 HB
Working with 20# CARB
Is 20# easy to machine?
Free machining is limited by gummy low-carbon ferrite — use sharp positive-rake tools, high speeds and good coolant; cold-drawn bar cuts and finishes far better than hot-rolled or annealed stock.
Can 20# be welded?
Excellent weldability by all arc, resistance and gas processes with no preheat below ~25 mm (CE ≈ 0.3); use ER70S-6 / E4303-E5015 class consumables.
Can 20# be formed, bent or molded?
Very good cold formability — deep drawing, bending to tight radii and cold heading are routine in annealed or hot-rolled condition; hot working range ~850–1200 °C.
What surface finishes work on 20#?
No anodizing; protect with zinc/electro-galvanizing, phosphate + oil, black oxide, hard chrome or paint — bare surfaces rust within days in humid air.
20# 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 | 0.17 – 0.23 | 0.2 |
| Si | 0.17 – 0.37 | 0.27 |
| Mn | 0.35 – 0.65 | 0.5 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.04 | 0.02 |
| Crresidual | ≤ 0.25 | 0.05 |
| Niresidual | ≤ 0.3 | 0.05 |
| Curesidual | ≤ 0.25 | 0.05 |
| Fe | balance | — |
20# CARB — frequently asked
What is 20# CARB used for?
20# CARB is typically used for general fabrication, brackets and welded plate. In short: cold-drawn carbon plate.
What is the yield strength of 20# CARB?
20# CARB has a typical yield strength of 450 MPa (65.3 ksi) and a tensile strength of 640 MPa (92.8 ksi) — stronger than 53% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is 20# CARB easy to machine?
Not especially — machinability is rated not recommended (12/100, worse than 99% of steel grades). Free machining is limited by gummy low-carbon ferrite — use sharp positive-rake tools, high speeds and good coolant; cold-drawn bar cuts and finishes far better than hot-rolled or annealed stock.
Can 20# CARB be welded?
Not readily — weldability is rated poor (25/100). Excellent weldability by all arc, resistance and gas processes with no preheat below ~25 mm (CE ≈ 0.3); use ER70S-6 / E4303-E5015 class consumables.
What surface finishes work on 20# CARB?
No anodizing; protect with zinc/electro-galvanizing, phosphate + oil, black oxide, hard chrome or paint — bare surfaces rust within days in humid air.
Can 20# CARB be formed, bent or molded?
Very good cold formability — deep drawing, bending to tight radii and cold heading are routine in annealed or hot-rolled condition; hot working range ~850–1200 °C.
What is the maximum service temperature of 20# CARB?
20# CARB is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 20#-CD and 20#-A?
CD is the default condition — default stock condition for small round bar, shafting and precision tube; best dimensional accuracy, surface finish and machinability. A: softest condition — pick for deep drawing, severe cold forming or stress relief before carburizing. Yield strength is 395 MPa in CD versus 250 MPa in A.
Can FabDigit make parts in 20# CARB?
Yes — 20# CARB is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — 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.