Defects and remedial measures of stainless steel castings after heat treatment

For box type and trolley type resistance furnace plates, a high temperature tempering should be carried out before use, and the temperature should be controlled above 950 degrees as far as possible, so as to eliminate the internal stress in the casting process. Moreover, in the process of using the furnace plate, it is necessary to ensure that the workpieces are placed evenly, and the workpieces cannot be stacked in a certain local position, otherwise, it will cause uneven heat dissipation of the furnace plate in the process of heating up, which is easy to cause deformation and cracking of the furnace plate, and reduce the service life of the furnace bottom plate.

The manufacture of stainless steel castings is completed by smelting, casting and heat treatment. The steel used for castings shall be melted in the Ayong induction furnace, electric arc furnace, ladle refining furnace or other smelting methods that meet the requirements. In the process of casting, if the demander has no special requirements, the supplier shall determine by itself. The method of heat treatment is that the castings shall be subject to heat treatment. Generally, the heat treatment shall be carried out by the supplier. In case of defect removal and repair welding, we shall implement the following regulations:

1. The castings should be opened after cooling to a certain temperature in the mold, and the visible defects on the surface of martensitic steel should be removed after softening annealing.

2. When removing defects, the minimum preheating temperature of castings shall be as specified in Table 2.

3. Casting defects are allowed to be repaired by repair welding. Before repair welding, all defects shall be removed to expose the surface of dense metal.

4. Repair welding shall be carried out with the same or similar welding rod as the casting material.

5. When repairing welding with martensitic electrode of the same material, defects and remedial measures after heat treatment of stainless steel castings are generally carried out after softening annealing and before final heat treatment. Unless otherwise specified, stress relief treatment shall be carried out after welding with martensitic electrode.

6. For chromium, manganese and nitrogen steel castings requiring intergranular corrosion tendency test or impact toughness test or both, solution treatment shall be carried out after repair welding.

The chemical composition of stainless steel castings shall meet the national regulations. When the demander needs to analyze the chemical composition of the finished product, the allowable deviation of chemical composition shall meet the regulations in Table 4. The mechanical properties of the castings after heat treatment shall meet the requirements of table 5, and the surface hardness is not used as the basis for acceptance. The surface roughness of stainless steel castings shall meet the requirements of GB / T 6060.1. Casting defects such as cracks, cold shuts, porosity and sand sticking are allowed on the surface of castings. The dimensional tolerance of castings shall comply with the provisions of GB / T 6414.