Why is the surface of stainless steel castings rough

The relationship between stainless steel temperature, molten metal pouring temperature and surface roughness of castings. With the increase of temperature and pouring temperature of molten metal, the filling performance of molten metal is improved, the depth of infiltration into surface pores is increased, and the surface roughness of stainless steel castings is increased.

1. First of all, in terms of materials, a large part of the roughness of the surface of stainless steel castings is due to the quality problem of the surface of stainless steel itself. Stainless steel is made of columnar crystal structure net and filled in the middle of the skeleton with refractory, additives and water. However, after drying and roasting, there are pores of different sizes on the surface, and the liquid metal penetrates into these pores, resulting in the roughness of the surface of stainless steel, Thus, the surface roughness of stainless steel castings is caused.

2. In terms of manufacturing industry, the casting process is an important link in casting stainless steel castings. The temperature of stainless steel, pouring temperature of molten metal, indenter, vacuum during pouring and other process parameters have an impact on the surface roughness of castings, especially the mold temperature and pouring temperature.

How to improve the surface roughness of stainless steel castings

1. To improve the smoothness of the stainless steel surface, the factor affecting the roughness of the stainless steel surface is that the liquid metal penetrates into some voids of the stainless steel surface. The crystal diameter, the average diameter of the surface pores and the radius of curvature of the alloy liquid surface will be important factors affecting the penetration depth of the liquid metal. Therefore, in order to obtain the stainless steel castings with smooth surface, it is necessary to reduce the diameter of the crystal and filler particles and the diameter of the surface pores; Or use additives that can be enriched on the surface to fill the larger pores to reduce the penetration depth of liquid metal.

2. Surface quality of pressing and investment mold. The surface roughness of investment mold is the most important link affecting the surface roughness of castings. It is also related to the surface quality of die, investment mold method and process parameters.

3. Due to the influence of the alloy, the thermal conductivity is small. After using stainless steel, the liquid metal is poured into the mold and cooled slowly. The grains of the casting are coarse. The concave groove between grains will make the surface of the casting rough, and the depth of the concave groove at the grain boundary will even reach 7 μ m。 Why is the surface of stainless steel castings rough?

4. The alloy should be modified, and zircon and other fillers with good thermal conductivity should be used to improve the cooling rate of stainless steel castings, make the grains on the surface layer of castings smaller, and reduce the surface roughness of castings.