Stainless steel casting is not only suitable for casting of various types and alloys, but also produces castings with higher dimensional accuracy and surface quality than other casting methods, and even complex, high temperature resistant, and difficult to cast castings that are difficult to cast by other casting methods. The processed castings can be cast by investment casting. The so-called investment casting process, simply put, is to use fusible materials (such as wax or plastic) to make a fusible model (referred to as investment mold or model), and apply several layers of special refractory coatings on it, which are dried and hardened. After forming an integral mold shell, the mold is melted from the mold shell with steam or hot water, and then the mold shell is placed in a sand box, filled with dry sand molding around it, and finally the mold is placed in a roasting furnace for high temperature. Roasting (for example, when a high-strength mold is used, the mold after demolding can be directly fired without molding), after the mold or mold is fired, molten metal is poured into it to obtain a casting.

The dimensional accuracy of investment castings is relatively high, generally reaching CT4-6 (CT10~13 for sand casting and CT5~7 for die casting). Of course, due to the complex process of investment casting, there are many factors that affect the dimensional accuracy of castings , such as the shrinkage of the mold material, the deformation of the investment mold, the linear change of the shell during heating and cooling, the shrinkage rate of the alloy, and the deformation of the casting during the solidification process, so the dimensional accuracy of ordinary investment castings is higher. , but its consistency still needs to be improved (the dimensional consistency of castings using medium and high temperature waxes is much improved).

1. Cast iron

Cast iron and steel are both iron-carbon alloys, and their difference is mainly in the carbon content. Iron-carbon alloys with a carbon content of less than 2% are called steels, and those with a carbon content of more than 2% are called cast irons. Cast iron has appropriate fusibility and good liquid fluidity, so it can be cast into parts with complex shapes. In addition, its shock absorption, wear resistance, machinability (referring to gray cast iron) are good and the cost is low, so it is widely used in machinery manufacturing. Commonly used cast irons are: gray cast iron, ductile iron, malleable cast iron, alloy cast iron, etc. Among them, gray cast iron and ductile iron are brittle materials and cannot be rolled and forged. Among the above cast irons, gray cast iron is the most widely used, followed by ductile iron.  

2. Steel

Compared with cast iron, steel has high strength, toughness and plasticity, and its mechanical properties and processing properties can be improved by heat treatment. The blanks of steel parts can be obtained by forging, stamping, welding or casting, so they are widely used. According to the application, steel can be divided into structural steel, tool steel and special steel. Structural steel is used to manufacture various mechanical parts and components of engineering structures; tool steel is mainly used to manufacture various cutting tools, molds and measuring tools; special steel (such as stainless steel, heat-resistant steel, acid-resistant steel, etc.) is used to manufacture in special environments working parts. According to the chemical composition, steel can be divided into carbon steel and alloy steel. The properties of carbon steel mainly depend on the carbon content. The higher the carbon content, the higher the strength of the steel, but the lower the plasticity. In order to improve the properties of steel, steels with some alloying elements are specially added are called alloy steels. 1) The carbon content of carbon structural steel is generally not more than 0.7%. Low carbon steel with a carbon content of less than 0.25% has low strength limit and yield limit, high plasticity, and good weldability. It is suitable for stamping and welding. It is often used to make screws, nuts, washers, shafts, Valve guides and welded components, etc. Low carbon steel with carbon content of 0.1% to 0.2% is also used to make carburized parts, such as gears, piston pins, sprockets, etc. Through carburizing and quenching, the surface of the part can be hard and wear-resistant, and the core is tough and impact-resistant. If higher strength and impact resistance are required, low carbon gold bearing steels can be used. carbon content in 0.3%~0.5% medium carbon steel, it has good comprehensive mechanical properties, not only high strength, but also certain plasticity and toughness. It is often used as bolts, nuts, keys, gears and shafts with high stress Components. High carbon steel with a carbon content of 0.55% to 0.7% has high strength and elasticity, and is mostly used to make ordinary leaf springs, coil springs or wire ropes.