Preheating is a key process to ensure the welding repair performance and quality of steel castings. The preheating temperature required for the welding repair area should be determined based on factors such as the material of the cast steel components to be welded and the environmental temperature of the welding site. The recommended preheating temperatures for welding repair areas of different cast steel component materials are shown in the table, while the preheating temperatures for welding repair of other cast steel components can be determined by reference.
| Cast steel grade | Heat treatment status | General defects (℃) | Major defects (℃) |
| ZG230-450 | Cast state | ≥ 5 | ≥ 150 |
| B-grade steel ZG310-570 | Cast state | ≥ 5 | ≥ 150 |
| C-grade steel | Normalization | ≥ 100 | 200 ～ 250 |
| C-grade steel E-grade steel ZG25MnCrNiMo | Tempering treatment | ≥ 180 | 200 ～ 250 |
For cast steel components that require preheating treatment before welding repair, priority should be given to overall preheating, such as using a resistance furnace for overall heating; When the overall preheating method is limited, local preheating can also be used, with the preheating range extending at least three times the width of the weld section thickness to both sides of the weld.