24 July 2021 Gear Steel Bar
20MnCr5 Gear Steel Bar
20MnCr5 is an alloy carburized steel, with high strength and toughness, and good hardenability. The performance after heat treatment is better than 20Cr. The quenching deformation is small, the low temperature toughness is good, and the machinability is good; but the welding performance is low. Generally used after carburizing, quenching or quenching and tempering. Used for manufacturing and heavy-duty hardened and tempered parts with large cross-sections and carburized parts with small cross-sections. It can also be used to manufacture small and medium-sized parts with medium load and low impact, instead of 20CrNi, such as gears, shafts, spindles, and friction wheels for variable speed equipment. , Worm, governor sleeve, etc.
20MnCr5 is a steel grade imported from Germany by China, which is equivalent to the Chinese standard 20CrMn steel. It is carburized steel and can also be used as quenched and tempered steel. The hardenability is good, the heat treatment deformation is small, the low temperature toughness is good, the cutting performance is good, but the weldability is poor. It can make carburized parts and hardened and tempered parts with larger cross-sections and higher loads, such as gears, shafts, worms, sleeves, friction wheels, etc., to manufacture mercury shafts and connecting rods under high-speed and high-bending load conditions. Gear mercury without strong impact load, water mercury rotor, clutch, bolts of high pressure vessel cover, etc.
Chemical Composition:
| С | Si | Mn | S | P | Cr |
| 0,17-0,22 | ≤0,40 | 1,10 - 1,40 | ≤0,035 | ≤0,025 | 1,00 - 1,30 |
Mechanical Properties:
Tensile Strength | Yield Strength | Impact Value KCU, 20°C | Hardness after tempering | Elongation | Thermal conductivity |
MPa | Mpa |
| HB | % | W/mK |
1000~1350 | ≥ 670 | KU 20J | ＜217 | 8 | 46.6 |
Heat Treatment:
Soft Annealing of 20MnCr5 steel
Heat to 650-700 oC.
Carburizing
Temperature 900-950 oC . Cooing from carburizing temperature: water, oil, air, thermal bath, cooling box.
Hardening
Core hardening 850 – 880 oC. Case hardening: 810 -840 oC. Quenching media: water, oil, air, thermal bath.
Tempering
Tempering temperature: 150-200 oC.
Forging
Hot Forming temperature: 1100-850 oC.
Rolling
Rolling temperature 1220 oC , Finishing Templerature > 900oC
Normalising
850-880 oC, air cool
Why use 20MnCr5 as raw material for gears manufacture?
20MnCr5 has a single alloying element, Chromium. It is a low alloy steel capable of being hardened upto HRC 41. This provides a tough core and can be case hardened by carburizing or carbonitriding to achieve a hard case. This alloy would be useful for items such as Spur gears and helical gears that require little or no size change during heat treatment and no post heat treatment finishing operations.