Heat treatment process of impeller investment casting sand casting

In order to improve the mechanical properties of zg1cr18ni9ti stainless steel impeller investment casting sand casting, reduce segregation and improve corrosion resistance. Solid solution treatment (as cast) → stabilization heat treatment process was selected in the experimental process. 75kW air electric furnace is selected for heating.

1. Solution treatment

Solid solution treatment is to heat the steel above the ES line to dissolve the carbide strengthening phase. When all carbides are dissolved in austenite, then quickly cool (water cooling), so that the austenite has no time to precipitate carbides or phase transformation in the cooling process, so as to improve the corrosion resistance of the material.

According to the characteristics of impeller investment casting sand casting material, shape and size, select < 300 ℃ to enter the furnace, and the heating temperature is between 1050 ~ 1100 ℃; The heating speed is 200 ~ 300 ℃ / h. during heating, the process of low-temperature preheating first and then rapid heating to the solid solution temperature should be adopted to reduce the temperature difference between the impeller investment casting sand mold casting surface and the core during the heating process. The holding time depends on the wall thickness of the impeller, and 3 ~ 4H should be selected to ensure the heat penetration of all sections of the impeller casting.

During solution treatment, clear water is used as the medium for rapid cooling. Impeller investment casting – sand casting shall be cleaned to remove oil stain on the surface before entering the furnace, so as to avoid Carburization on the material surface during heating. The process of solid solution treatment is shown in Figure 1.

2. Stabilization treatment

In order to prevent the precipitation of Cr23C6 at the grain boundary when zg1cr18ni9ti is heated and prevent the phenomenon of Cr deficiency at the grain boundary, so as to eliminate the tendency of intergranular corrosion. After the solid fusion treatment, the stabilization treatment was carried out. The stabilization treatment process is shown in Figure 2. The heating temperature is 850 ℃~ 950 ℃, and air cooling is carried out after holding for 2 ~ 4H.