For welding repair of important steel castings, post weld heat treatment is generally required to eliminate thermal stress after welding repair. For general defects, local heating can be carried out to eliminate stress according to the flame heating or electric heating belt recommended in the table. During local heat treatment, the range of heat treatment should be at least 1.5 times the weld width on both sides of the weld repair area, or at least 100 mm on both sides of the weld repair area. Asbestos cover cooling should be used for heat treatment.
| Cast steel grade | Heat treatment status | General defects (℃) | Major defects (℃) |
| ZG230-450 | As-cast state | ≥ 5 | ≥ 150 |
| Grade B steel ZG310-570 | As-cast state | ≥ 5 | ≥ 150 |
| Grade C steel | Normalizing | ≥ 100 | 200 ～ 250 |
| Grade C steel | Quenching and tempering treatment | ≥ 180 | 200 ～ 250 |
| Grade E steel ZG25MnCrNiMo | Quenching and tempering treatment | ≥ 180 | 200 ～ 250 |
Unless otherwise specified in other technical conditions, major defects (single defects with a depth exceeding 15mm or a minimum dimension greater than 20% of the wall thickness of the steel casting, or groove areas exceeding 10cm ^ 2) shall be subjected to overall stress relief or re heat treatment after repair welding.
The time required for post weld heat treatment of steel castings can be calculated by adding 15min for every 6mm of weld repair thickness. For weld repair thicknesses less than 6mm, the post weld heat treatment time should not be less than 15min.