Casting parts Definition
- Casting-Molding methodof smelt metal, manufacture molds, and pour molten metal into the molds,after solidification, obtain rough metal parts with certain shape, size and performance.
- Casting is the process of smelting metal into a liquid that meets certain requirements and pouring it into a mold. After cooling, solidification, and cleaning, a casting with a predetermined shape, size and performance is obtained. Because the casting blank is almost formed, it can achieve the purpose of avoiding machining or a small amount of processing, reducing the cost and reducing the production time to a certain extent. Casting is one of the basic processes of modern device manufacturing industry.
Casting parts classification
There are two main categories: sand casting and special casting.
- Ordinary sand casting uses sand as the mold material, including 3 types of green sand casting, dry sand casting and chemically hardened sand casting, but not all sand can be used for casting. The advantage is that the cost is lower, because the sand used in the mold can be reused. The disadvantage is that the production of the mold is time-consuming, the mold itself cannot be reused, and the finished product can only be obtained after destruction.
- Sand mold (core) casting : green sand mold, resin self-hardening sand mold, sodium silicate sand mold, dry mold and surface dry mold, solid mold casting, negative pressure mold.
- Sand core manufacturing method: It is selected according to the size, shape, production batch and specific production conditions of the sand core. In production, it can be divided into manual core making and machine core making .
- Special casting, according to the modeling material, can be divided into special casting with natural mineral sand and gravel as the main modeling material (such as investment casting, mud casting, shell casting, negative pressure casting, solid casting, ceramic casting, etc.) ) And special casting with metal as the main casting material (such as metal mold casting, pressure casting, continuous casting, low pressure casting, centrifugal casting, etc.).
Metal mold casting method
Use a metal with a higher melting point than the raw material to make a mold. Which is subdivided into gravity casting method, low pressure casting method and high pressure casting method.
Subject to the melting point of the mold, the metal that can be cast is also limited.
Dewaxing casting method
This method can be the outer film casting method and the solid casting method.
Copy the object to be cast with wax first, then immerse it in a pool containing ceramics (or silica sol) and wait for it to dry, so that the wax replica is covered with a ceramic outer film. Repeat the steps until the outer film is sufficient to support the casting Process (about 1/4 inch to 1/8 inch), then melt the wax in the mold and pull out of the mold. After that, the mold needs to be heated many times to increase the hardness before it can be used for casting.
This method has good accuracy and can be used for casting high melting point metals (such as titanium). However, due to the high price of ceramics, and the need for multiple heating and complicated production, the cost is quite expensive.
- Gravity casting: sand casting, hard mold casting. Rely on the gravity of the metal to pour molten metal into the cavity.
- Pressure casting: low pressure casting, high pressure casting. Rely on the additional pressure to instantly press the molten metal into the casting cavity.
The casting process usually includes
- Preparation of molds (containers that make liquid metal into solid castings). The molds can be divided into sand, metal, ceramic, clay, graphite, etc. according to the materials used, and can be divided into disposable and semi-permanent types according to the number of uses And permanent mold, the pros and cons of mold preparation are the main factors affecting the quality of castings;
- Melting and pouring of cast metals, cast metals (casting alloys) mainly include various types of cast iron, cast steel, and cast non-ferrous metals and alloys;
- Casting processing and inspection. Casting processing includes removal of foreign bodies on the core and surface of the casting, removal of pouring risers, shovel grinding of burrs and drape seams and other protrusions, as well as heat treatment, shaping, rust prevention treatment and rough machining.
The casting process can be divided into three basic parts, namely casting metal preparation, mold preparation and casting processing. Casting metal refers to the metal material used for casting castings in the production of casting. It is an alloy composed of a metal element as the main component and added with other metals or non-metal elements. It is customarily called a casting alloy, mainly including cast iron, Cast steel and cast non-ferrous alloys.