Customized cast steel parts for ships: Low alloy cast steel refers to cast steel with a total alloy element content of less than 5%, which has high impact toughness and good performance, and is widely used in industries such as railways, engineering machinery, automobiles, and ships. This type of alloy is prone to cracking during welding, and it should be noted that a reasonable repair welding process is crucial for its performance. Generally, the following methods are used:
1. Defect cleaning
For the repair of defects in cast steel parts, carbon arc gouging can be used to remove the defects. At the same time, clean the sand, oxide scale, rust, oil, moisture and other dirt in the welding area and within a 20mm range around it, and polish the welding area into a circular arc surface for welding repair.
2. Welding rod
Use F5105 for welding rods. Dry at 350 ℃ and keep warm for 1 hour before welding. After drying, the welding rods should be stored in the insulation cylinder and taken as needed. Non dried welding rods are not allowed to be used.
3. Preheating before welding
Preheating temperature control: For cast steel parts with a carbon content not exceeding 0.44%, the preheating temperature is 120-200 ℃; For cast steel parts with a carbon equivalent exceeding 0.44%, the preheating temperature shall not be lower than 200 ℃.
4. Welding parameters
The diameter of the welding rod is 4mm, the welding current is 90-240A, the voltage is 25-30V, and the welding speed is 4-20cm/min.
5. Operation points
Repair welding should be carried out in the flat welding position as much as possible; The swing amplitude of the welding rod during welding is less than three times the diameter of the welding rod used; After the repair is completed, the welding surface should be polished smooth, and the surface size should meet the requirements of the drawing.
6. Post weld heat treatment
The stress relief heat treatment for steel castings after welding repair is: the heat treatment temperature is 550-650 ℃. For relatively small repair welding areas and cast steel in the final stage of machining, local stress relief heat treatment method can be used, which means that the heating temperature within the welding area and its surrounding 100mm range on all surfaces of the repair welding should not be lower than 600 ℃, and the temperature difference between the insulation area and the non insulation area should not exceed 300 ℃. For every 25mm welding depth, the insulation time shall not be less than 10 minutes, and slow cooling treatment shall be adopted.
7. Inspection
After welding repair, magnetic inspection was conducted on the welding area and its surrounding 50mm area, and no defects such as cracks or pores were found.
Practice has proven that the above-mentioned welding rod arc welding repair process can meet the quality requirements for low-alloy cast steel.
Changshu Hongqiao Cast Steel Co., Ltd. mainly produces various specifications of carbon steel, high, medium and low alloy steel, stainless steel, heat-resistant steel, high manganese steel, and high chromium cast iron. We provide high-quality cast steel parts for industries such as petroleum, chemical, metallurgical, mining machinery, coal mining machinery, wind power, nuclear power, and marine. We also offer customized marine cast steel parts, ABS marine engineering services, and cast steel for export overseas.