AISI 8620 ALLOY STEEL | DIN 1.6523 | 20NICRMO2-2
AISI 8620 is a case-hardening steel which has at least 0.4% Cr, 0.15% Mo and 0.4% Ni as strengthening alloy elements.Compared with grades 8615 and 8617,it offers good core strength and toughness in small to medium sections with case hardness up to Rc62 when carburized, hardened and tempered.AISI 8620 is generally supplied as annealed condition with HB 255max.Pre hardened and tempered (uncarburized) 8620 can be further surface hardened by nitriding,but flame or induction hardening is not recommended due to its low carbon content.AISI 8620 is easily machined following suitable cooling from forging or subsequent heat treatment,and can be readily welded in the as rolled condition with the correct procedure, but welding in the case hardened or through hardened condition is not recommended.
1.AISI 8620 steel Supply Form & Size
| Form of Supply | Size(mm) | Length(mm) |
| Round bar | Φ6-Φ1,000 | 3,000-10,000 |
| Square bar | 100x100-600x600 | 3,000-6,000 |
| Plate/Sheet |
Thickness :20-400 Width:80-1,000 |
2,000-6,000 |
| Flat bar/Blcoks |
Thickness :120-800 Width:120-1,500 |
2,000-6,000 |
2.Surface Finish&Tolerance
| Surface Finish | Black-Forged | Black-Rolled | Turned | Grinding | Polished | Peeled | Cold Drawn |
| Tolerance | (0，+5mm) | (0，+1mm) | (0，+3mm) | Best h9 | Best h11 | Best H11 | Best H11 |
3.Chemical Composition&Related Specifications
| C | Mn | P | S | Si | Ni | Cr | Mo |
| 0.18-0.23 | 0.7-0.9 | ≤ 0.035 | ≤ 0.04 | 0.15-0.35 | 0.4-0.7 | 0.4-0.6 | 0.15-0.25 |
| Germany | UK | China | Japan |
| 1.6523/20CrNiMo2-2 | 805M20 | 20CrNiMoA | SNCM220 |
4.Mechanical Property
Section Size 25 mm, Water Quenched at 830°C
| Tempering Temperature °C | Tensile Strength Mpa | Yield Strength Mpa | Elongation % | Impact Izod J | Hardness HB |
| 205 | 1050 | 765 | 18 | 80 | 311 |
| 425 | 930 | 800 | 20 | 110 | 275 |
| 650 | 700 | 556 | 30 | 140 | 207 |
AISI 8620 Mechanical Property -Normalizing(+N) Vs Annealing(+A)
| Tensile,Mpa | Yield,Mpa | Elongation,% | Reduction,% | Charpy Impact, J | Brinell Hardness,HB | |
| +N | ≥635 | ≥355 | ≥26.3 | ≥60 | ≥100 | 183 |
| +A | ≥535 | ≥385 | ≥31.3 | ≥62 | ≥112 | 149 |
5.Forging for AISI 8620
- Heat the temperature to 1150-1200°C uniformly and slowly;
- Keep the temperature stable for steel to be heated throughout the section;
- Reheat the steel when forging temperature below 850°C;
- Cool slowly in ashes or sand after forged
6.Heat Treatment
- Normalizing：900°C – 925°C ,Cooling in air
- Annealing: 820°C – 850°C,Cooling in furnace
- Caburizing: 900°C – 925°C
- Core Refine:Reheat temperature to 840°C – 870°C during slow cooling after carburized,hold enough time for the steel to be heated uniformly, quench as required in water, oil or air cool.
- Case Hardening:Reheat the steel to 780°C – 820°C after core refining, hold enough time for the steel to be heated uniformly, and quench in oil.Followed by tempering as soon as possible.
- Tempering:150°C – 200°C,cool in still air
- Nitriding:490°C – 530°C,slow cooling
7.Application
AISI 8620 is used extensively by all industry sectors for light to medium stressed components and shafts requiring high surface wear resistance with reasonable core strength and impact properties,and can be used for high tensile applications uncarburised but through hardened and tempered.Typical uses are: Arbors, Bearings, Bushings, Cam Shafts, Differential Pinions, Guide Pins, King Pins, Pistons Pins, Splined Shafts, Ratchets, Sleeves etc