SNCM431 4340 DIN 1.6580 30CrNiMo8 Hardened Steel
4340 SNCM431 DIN1.6580 30CrNiMo8 Hardened Steel
1. 4340 Applications
Alloyed heat treatable steel with a typical tensile strength of 1100 -1300 N/mm². Used for highly stressed components, where the combination of high strength with tenaciousness is of utmost importance. High cold formability: Parts of different shape can be manufactured, a favorable fibering for stress, a very good surface condition and an high dimensional accuracy. When cold formed the smooth surface leads to an increased fatigue and vibratory strength.
2.All Grades Comparison
| Material no. | DIN | BS | ASTM |
| 1.6580 | 30CrNiMo8 | 823M30 | 4340 |
| AFNOR | ISO | ГOCT | JIS |
| 30CND8 | 31CrNiMo8 | 3KH3M3F | SNCM431 |
3. 4340 Chemical Composition(%)
| Steel Grade | C | Mn | Si | P | S | Cr | Ni | Mo |
| 30CrNiMo8 | 0.26-0.34 | 0.50-0.80 | 0.40 max | 0.025 max | 0.035 max | 1.80-2.20 | 1.80-2.20 | 0.30-0.50 |
| 4340 | 0.38–0.43 | 0.60-0.80 | 0.15-0.35 | 0.035 max | 0.040 max | 0.70-0.90 | 1.65-2.00 | 0.20-0.30 |
| SNCM431 | 0.27-0.35 | 0.60-0.90 | 0.15-0.35 | 0.030 max | 0.030 max | 0.60-1.10 | 1.60-2.00 | 0.15-0.30 |
4. 4340 Mechanical Properties(T=20°C if not differently stated)
| Heat treatment state | Diameter(mm) | Rm (Mpa) | Rp0.2 (Mpa) | Fracture elongation A5 (%) | Notch impact energy ISO-V [J] | Hardness (HB) |
| SOFT ANNEALED | / | 844 min | / | / | / | 250 max |
| ISOTHERMAL ANNEALED | / | 615-815 | / | / | / | 183-242 |
| QUENCHED AND TEMPERED | 16 max | 880-1080 | 685 min | 16 min | 40 min | 289-347 |
| QUENCHED AND TEMPERED | 16-40 | 930-1080 | 735 min | 16 min | 40 min | 275-318 |
| QUENCHED AND TEMPERED | 40-100 | 880-1030 | 685 min | 17 min | 40 min | 261-303 |
| QUENCHED AND TEMPERED | 100-250 | 785-935 | 635 min | 18 min | 35 min | 233-276 |
| QUENCHED AND TEMPERED | 250-500 | 735-885 | 590 min | 16 min | 35 min | 218-262 |
5.HEAT TREATMENT AND HOT PLASTIC DEFORMATION TEMPERATURES
| – | TEMPERATURE ° C | Cooling Medium |
| Hot plastic deformation | 850-1100 | / |
| Normalizing | 850-880 | air |
| Soft Annealing | 650-690 | air |
| Quenching | 830-860 | oil |
| Tempering | 540-660 | air |
