China · GB
25
GB/T 699:2015 — Quality carbon structure steels
Chemical composition
| Element | min | max | Similar | Remarks |
|---|---|---|---|---|
| C | 0.22 | 0.29 | ||
| Cr | 0.25 | |||
| Cu | 0.25 | 热压力加工用钢铜含量应不大于0.20% | 热压力加工用钢铜含量应不大于0.20% | |
| Mn | 0.5 | 0.8 | ||
| Ni | 0.3 | |||
| P | 0.035 | |||
| S | 0.035 | |||
| Si | 0.17 | 0.37 |
Mechanical properties
| Heat treatment / condition | Yield strength | Tensile strength | Elongation | Reduction of area | Impact energy | Hardness |
|---|---|---|---|---|---|---|
| steel bars, quenched and tempered, d = 25 mm, d - specimen | ≥275 | ≥450 | ≥23 | ≥50 | ≥70 | |
| steel bars, hot rolled or , d = 25 mm, d - specimen | HB ≤170 |
Heat treatment
| Type | 3 | 4 |
|---|---|---|
| Heat-treatment process | Tempered | 600℃±50℃回火不少于1h |
| Heat-treatment process | Quenched | 870℃±20℃，保温不少于30min，水冷 |
| Heat-treatment process | Normalized | 900℃±30℃，保温不少于30min，空冷 |