Repair Welding Process of Steel Castings

Repair welding process of steel castings
Low-alloy cast steel refers to cast steel whose total output value of alloy elements is less than 5%. It has very large impact toughness and very good performance parameters. These alloys are prone to cracks during electric welding. It must be noted that an effective welding repair process is critical to their properties.
1. Elimination of shortcomings
For the repair of the defects of steel castings, carbon arc gouging can be applied to eliminate the defects. In addition, the slag inclusions, oxide scale, rust, oil, moisture and other wastes in the welding repair area and the surrounding area within 20 mm are cleaned and cleaned, and the welding repair area is polished and polished into an arc surface, which is convenient for welding repair.
2. Welding wire
Welding wire with F5105. Before welding, air-dry at 350°C and heat insulation for 1h. The air-dried welding wire should be stored in the thermal insulation cylinder for use at any time, and the non-air-dried welding wire should not be used.
3. Heating before welding
Heating temperature control: For steel castings with carbon orders not exceeding 0.44%, the heating temperature is 120-200 °C; for steel castings with carbon equivalents exceeding 0.44%, the heating temperature should not be less than 200 °C.
4. Main parameters of electric welding
The diameter of the welding wire is 4mm, the welding current of electric welding is 90-240A, the working voltage is 25-30V, and the welding speed of electric welding is 4-20 cm/min.
5. Key points of practical operation
Welding repair should be carried out at the vertical welding part as much as possible; the swaying power of the welding wire during electric welding is lower than 3 times of the diameter of the commonly used welding wire; after the repair is completed, the surface of the electric welding welding should be polished and smooth, and the surface specifications should be considered.
6. Post-weld heat treatment
The heat treatment process for removing in-situ stress after welding repair of steel castings is as follows: the temperature of the heat treatment process is 550-650 °C. For the welding repair area is relatively small, and the cast steel is in the process of machining, the partial removal of ground stress heat treatment method can be used, that is, in the whole surface of the welding repair, the electric welding area and the surrounding 100 mm are heated The temperature shall not be less than 600℃, and the temperature difference between the thermal insulation area and the non-thermal insulation area shall not exceed 300℃. Every 25mm of electric welding is welded deep, the heat insulation time is not less than 10min, and slow cooling and violence are used.
7. Detection
After welding repair, magnetic inspection is carried out in the welding repair area and the surrounding area of 50 mm, and there are no defects such as cracks and air holes. According to practical experience, the low-alloy cast steel can meet the quality requirements by using the arc welding repair process.