Steel 20CrMo4 +TH
Hardness band
EN 20CrMo4
+TH = treated to a specified hardness range
Ordered when the mill must guarantee a narrow hardness band for automated turning/hobbing lines before carburizing.
Values for the +TH condition
Other 20CrMo4 tempers and conditions
20CrMo4 is listed in 10 conditions; see the grade overview at 20CrMo4.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Spheroidize annealed | Choose for cold extrusion/cold heading of gear blanks and pinions — lowest hardness and best cold flow. | 310 | 490 | 26 | 145 HB | — |
Treated for high shearability | Choose for billets that must be cold-sheared into slugs without cracking or burr-tearing on the press line. | 320 | 510 | 25 | 150 HB | 7.5 % IACS |
+ADefault Annealed | Standard stock condition for bar and tube: soft enough for general machining before carburizing. | 360 | 570 | 22 | 170 HB | — |
Treated to ferrite-pearlite structure and hardness range | Pick when a uniform ferrite-pearlite microstructure and predictable chip control for high-volume automatic machining are required. | 370 | 580 | 21 | 165 HB | 7.5 % IACS |
Restricted hardenability (Jominy band) grade, supplied in +A/+TH | Order +H (or +HH/+HL) when case depth and core hardness after carburizing must be statistically repeatable batch to batch. | 370 | 580 | 21 | 43 HRC | 7.5 % IACS |
+THThis page Treated to a specified hardness range | Ordered when the mill must guarantee a narrow hardness band for automated turning/hobbing lines before carburizing. | 400 | 620 | 20 | 180 HB | 7.5 % IACS |
Normalized | Grain-refined condition used after forging to homogenize structure and minimize carburizing distortion. | 430 | 670 | 20 | 195 HB | — |
Cold drawn | Bright-drawn bar for close tolerance shafts and pins where minimal turning stock is wanted. | 600 | 720 | 11 | 215 HB | — |
Q&T | Used for shafts and fasteners in thin sections where no case is needed but higher core strength than normalized is required. | 800 | 1,000 | 14 | 32 HRC | — |
Carburized, hardened and low-temperature tempered | Final service condition for gears, splines and bearing races: hard wear-resistant case with tough core and high bending fatigue strength. | 850 | 1,150 | 11 | 60 HRC | — |
What is 20CrMo4 +TH?
20CrMo4 +TH is 20CrMo4 heat treated to +TH — ordered when the mill must guarantee a narrow hardness band for automated turning/hobbing lines before carburizing. 20CrMo4 +TH has a yield strength of 400 MPa (58 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 60% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi). 20CrMo4 +TH 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; +TH is available on request or by drawing note.
20CrMo4 +TH properties
Typical room-temperature values for 20CrMo4 +TH; 22 are specific to this condition. Other listed values are 20CrMo4 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
20CrMo4 +TH 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
20CrMo4 +TH has a yield strength of 400 MPa (58 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 60% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
20CrMo4 +TH is rated for continuous service to 400°C (752 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical3
20CrMo4 +TH conducts electricity at 7.5 % IACS, worse than 67% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 20CrMo4 +TH takes about 30 MJ of energy and emits 2.1 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 30%.
Manufacturability7
20CrMo4 +TH's machinability is good (60/100, better than 83% of steel grades); weldability good (55/100); formability fair (50/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 20CrMo4 +TH
Is 20CrMo4 easy to machine?
Machine in +A/+FP/+TH before carburizing — carbide inserts, 120–180 m/min turning; after case hardening only grinding, EDM or CBN turning is practical.
Can 20CrMo4 be welded?
Weldable with low-hydrogen consumables at CE ≈ 0.55: preheat 150–250 °C and PWHT at 600–650 °C; never weld carburized surfaces.
Can 20CrMo4 be formed, bent or molded?
Cold heading and extrusion are routine in the +AC/+S spheroidized conditions; hot forge 1150–850 °C followed by normalizing to refine grain.
What surface finishes work on 20CrMo4?
No anodizing — use Mn/Zn phosphating, black oxide, zinc or Zn-Ni plating (bake to avoid hydrogen embrittlement above 1000 MPa); shot peening after grinding boosts gear-root fatigue life.
20CrMo4 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 |
|---|---|---|
| Ccase-hardening carbon level | 0.17 – 0.23 | 0.2 |
| Si | 0.1 – 0.4 | 0.25 |
| MnGB 20CrMo runs lower, 0.40–0.70 | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | — |
| Smax; S-grades to 0.020–0.040 for machinability | ≤ 0.04 | — |
| Cr | 0.9 – 1.2 | 1.05 |
| Mo | 0.15 – 0.25 | 0.2 |
| Fe | balance | — |
20CrMo4 +TH — frequently asked
What is 20CrMo4 +TH used for?
20CrMo4 +TH is typically used for gears, shafts, bearing races and camshafts. In short: standard Cr-Mo case-hardening steel; 4118 / SCM420 equivalent; hard case, tough core.
What is the yield strength of 20CrMo4 +TH?
20CrMo4 +TH has a typical yield strength of 400 MPa (58 ksi) and a tensile strength of 620 MPa (89.9 ksi) — weaker than 60% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 20CrMo4 +TH easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Machine in +A/+FP/+TH before carburizing — carbide inserts, 120–180 m/min turning; after case hardening only grinding, EDM or CBN turning is practical.
Can 20CrMo4 +TH be welded?
Yes — weldability is rated good (55/100). Weldable with low-hydrogen consumables at CE ≈ 0.55: preheat 150–250 °C and PWHT at 600–650 °C; never weld carburized surfaces.
What surface finishes work on 20CrMo4 +TH?
No anodizing — use Mn/Zn phosphating, black oxide, zinc or Zn-Ni plating (bake to avoid hydrogen embrittlement above 1000 MPa); shot peening after grinding boosts gear-root fatigue life.
Can 20CrMo4 +TH be formed, bent or molded?
Cold heading and extrusion are routine in the +AC/+S spheroidized conditions; hot forge 1150–850 °C followed by normalizing to refine grain.
What is the maximum service temperature of 20CrMo4 +TH?
20CrMo4 +TH 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 20CrMo4 +A and 20CrMo4 CARB?
+A is the default condition — standard stock condition for bar and tube: soft enough for general machining before carburizing. CARB: final service condition for gears, splines and bearing races: hard wear-resistant case with tough core and high bending fatigue strength. Yield strength is 360 MPa in +A versus 850 MPa in CARB.
Sources
- EN 10084 — Case hardening steels: technical delivery conditions — CEN (2008)
- GB/T 3077 — Alloy structural steels (20CrMo) — SAC (2015)
- JIS G 4053 — Low-alloyed structural steels (SCM420) — JISC (2016)
- SAE J404 / ASTM A29 — AISI 4118 chemical composition — 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 (carburizing) — ASM International (2013)
- Case-hardening steel bar datasheets (Cr-Mo grades) — Ovako / Böhler / Dörrenberg (2022)
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.