Italy · UNI
C 55
UNI 7874:1979 — UNI 7874
Chemical composition
| Element | min | max | Similar | Remarks |
|---|---|---|---|---|
| C | 0.5 | 0.62 | ||
| Mn | 0.56 | 0.94 | ||
| P | 0.04 | |||
| S | 0.04 | |||
| Si | 0.12 | 0.42 |
Mechanical properties
| Heat treatment / condition | Yield strength | Tensile strength | Elongation | Reduction of area | Impact energy | Hardness |
|---|---|---|---|---|---|---|
| bars, not heat treated | ≥880 | HB ≤268 | ||||
| bars, normalized | ≥305；≥315；≥335；≥355；≥365 | 665–825；685–835；695–845；705–855；715–865 | ≥10；≥12；≥13；≥11 | ≥20 KCU；≥10 KCU；≥13 KCU；≥15 KCU | HB 200–254；HB 206–257；HB 209–259；HB 212–262；HB 215–265 | |
| bars, quenched and tempered | ≥410；≥430；≥490；≥510；≥540 | 725–855；755–885；765–895；785–905；590–935 | ≥13；≥15；≥14；≥12 | ≥10 KCU；≥15 KCU | HB 225–270；HB 228–274；HB 234–278；HB 242–286 | |
| bars, annealed | ≥800 | HB ≤244 |
Fatigue
| Item | Detail |
|---|---|
| Product | Semi Finished products; Thickness: <= 16 mm; +QT |
| Experiment | Reversed bending; T: 20°C |
| Specimen |
| Property | Value |
|---|---|
| Yield strength (MPa) | 550.0 |
| Tensile strength (MPa) | 800.0 950.0 |
| Elongation (%) | 12.0 |
| Reduction of area (%) | 30.0 |
| No. | Cycles |
|---|---|
| 1 | 1E7 |
Heat treatment
| Type | 1 |
|---|---|
| Heat-treatment curve | Hardness-Tempering |