Development Process for Casting Stainless Steel

In the casting production process, the mold plays a crucial role, as it allows the molten metal to solidify within it and form a casting. The surface of the mold cavity that comes into direct contact with the molten metal is called the working surface.

The quality of the mold is largely determined by the quality of the working surface, because during the pouring and solidification of the molten metal, a series of physical and chemical reactions occur at the interface between the molten metal and the working surface.

Under unfavorable conditions, the interaction between the mold and the molten metal at the interface can lead to a rough casting surface or even cause defects such as sand adhesion, sand holes, and pitting.

Currently, for the production of stainless steel castings, manufacturers generally use quartz water-glass sand and quartz resin sand; of course, for specific products, they may also use chromite water-glass sand, zircon resin sand, and other materials.

Applying coatings to the surfaces of sand molds and cores can enhance surface strength and resistance to sand adhesion. This is one of the most effective measures for preventing defects such as sand adhesion, sand inclusions, and sand holes; achieving castings with a smooth surface; reducing sand loss; and minimizing the labor required for casting cleanup.

In particular, the problem of sand adhesion in large cast steel parts is often resolved through the use of coatings. Therefore, coatings are crucial to the surface quality of castings.

Coatings should possess good resistance to sand adhesion as well as good processability, such as stability, brushability, strength at room temperature, high-temperature strength, and crack resistance. A coating must have good brushability to adhere uniformly to the surfaces of sand molds and cores.

They must also possess sufficient strength and thermal stability, namely high refractoriness and chemical inertness. These properties of the coatings are ensured by the quality of the raw materials, the appropriate selection of formulations, and correct preparation and application processes.　　

Since water glass binders are water-soluble, water glass sand molds and cores are not compatible with water-based coatings. When water-based coatings are applied to hardened water glass sand molds and cores, the moisture in the coating penetrates the hardened water glass sand, is absorbed, and causes the molds and cores to soften, thereby reducing their surface strength. Therefore, alcohol-based stainless steel coatings should be used for water glass sand molds.

Resin sand molds pose inherent toxicity risks during operation. From the perspective of operator health and safety, cost reduction for coatings, and the fact that burning alcohol-based coatings can somewhat compromise the surface strength of resin sand molds, water-based stainless steel coatings should be used.