20MnCr5 Forgings
20MnCr5 is the standard case hardening grade for transmission components. Low carbon keeps the core tough and ductile; manganese and chromium give the consistent carburising response that gear shops depend on.
- Carbon
- 0.17 – 0.22%
- Manganese
- 1.10 – 1.40%
- Chromium
- 1.00 – 1.30%
- Case Hardness
- 58 – 62 HRC
- Core Hardness
- 30 – 40 HRC
- Equivalent
- AISI 5120, SCr420, 20MnCr5
20MnCr5 Forgings at a glance
Quotable facts from Avadh Techno Forge, Gundasara, Gondal, Rajkot.
- Carbon: 0.17 – 0.22%
- Manganese: 1.10 – 1.40%
- Chromium: 1.00 – 1.30%
- Case Hardness: 58 – 62 HRC
- Core Hardness: 30 – 40 HRC
- Equivalent: AISI 5120, SCr420, 20MnCr5
Case and Core in One Part
Carburising builds a hard, wear-resistant case of 0.6–1.5 mm over a core that stays around 30–40 HRC. A gear tooth therefore resists surface pitting while its root retains the ductility to absorb shock.
- Case hardness 58–62 HRC
- Core hardness 30–40 HRC
- Case depth 0.6–1.5 mm typical
- Consistent carburising response
Forging Control for Consistent Case
Finish forging temperature and cooling rate influence grain size, which in turn influences case depth uniformity. We control both, because a gear shop receiving blanks with variable case response will blame the steel and change supplier.
Applications
Gear blanks, pinion shafts, splined shafts, universal joint crosses, sprockets, cam followers and any component wearing at the surface while loaded in the body.
20MnCr5 Chemical Composition and Case Properties
20MnCr5 (material number 1.7147) is the standard case hardening steel for transmission components, specified under EN ISO 683-3, with AISI 5120 and JIS SCr420 as close counterparts. Its low carbon keeps the core tough and ductile, while manganese and chromium give the consistent carburising response gear manufacturers depend on.
| Property | Typical value |
|---|---|
| Carbon | 0.17 – 0.22% |
| Manganese | 1.10 – 1.40% |
| Chromium | 1.00 – 1.30% |
| Silicon | 0.40% maximum |
| Case hardness after carburising | 58 – 62 HRC |
| Core hardness | ≈ 30 – 40 HRC |
| Typical effective case depth | 0.6 – 1.5 mm |
| Supply hardness for machining | Agreed band, commonly ≈ 170 – 210 HB |
Hardenability Bands and Why Gear Makers Specify Them
Two heats of 20MnCr5 within specification can still harden differently, and in gears that variation shows up as inconsistent core hardness and inconsistent distortion after carburising. Gear manufacturers therefore often specify a restricted hardenability band, designated +H, so that successive heats respond the same way. Hardenability itself is measured by the Jominy end-quench test under ASTM A255 or ISO 642. See forged gear blanks.
- +H grades guarantee a defined hardenability band
- Fine grain size, commonly ASTM 5 or finer, controls distortion
- Isothermal annealing of blanks gives uniform machinability
- Distortion consistency matters more than distortion magnitude
People also ask
What case depth does 20MnCr5 achieve?
0.6 to 1.5 mm effective case depth is typical for transmission gears, set by the carburising cycle.
What hardness do 20MnCr5 blanks arrive at for machining?
Typically 180 to 220 BHN normalised or annealed, suited to hobbing and turning.
Topics covered on this page
- 20MnCr5 forging manufacturer India
- case hardening steel forging
- gear steel forging supplier
- 20MnCr5 forged blanks Rajkot
Based on work carried out at our own forging plant at Gundasara, Gondal, Rajkot — operating since 2008.
Questions Answered
What case depth can be achieved?
+
0.6 to 1.5 mm is typical for transmission parts, set by the carburising cycle your heat treatment specifies.
Why is 20MnCr5 preferred for gears?
+
It gives a hard wear-resistant case over a tough core, with very consistent carburising response batch to batch.
Do you carburise in-house?
+
Forging, normalising and machining are in-house; carburising is arranged with qualified processors with records supplied.
What supply hardness do you provide blanks at?
+
Typically 180–220 BHN normalised or annealed, suited to hobbing and turning.