Casting is an integral casting of material in the die. Its stress distribution is uniform and there is no restriction on the direction of compression. The forging is made of the same direction of force, its internal stress has a directional, can only bear directional pressure.
1. Casting: The process of melting metal into a liquid that meets certain requirements and pouring it into the casting mould. After cooling, solidification and cleaning, the casting (parts or blanks) with predetermined shape, size and properties can be obtained. The basic technology of modern machinery manufacturing industry.
2. The cost of casting blank is low, and it is more economical for parts with complex shape, especially those with complex inner cavity. At the same time, it has wide adaptability and good comprehensive mechanical properties.
3. However, the materials and equipment needed for foundry production (such as metallurgical furnace, sand mixer, moulding machine, core-making machine, sand blasting machine, shot blasting machine, cast iron plate, etc.) are more, and dust, harmful gases and noise will be produced, which will pollute the environment.
4. Foundry is a kind of metal hot-working technology which has been mastered by human beings for about 6,000 years. In 3200 B.C., bronze frog castings appeared in Mesopotamia. Between the 13th and 10th centuries B.C., China has entered the heyday of bronze castings and reached a fairly high level in technology, such as the 875 kg Simuwu Ding in the Shang Dynasty, the Zeng Hou Yi Zunpan in the Warring States Period and the transmission mirror in the Western Han Dynasty, which are all representative products of ancient casting. Earlier casting was greatly influenced by pottery. Most of the castings were tools or appliances for agricultural production, religion, life and other aspects, with strong artistic color. In 513 B.C., China cast the first iron castings in the world, the Jin casting tripod (weighing about 270 kg). Around the 8th century, Europe began to produce iron castings. After the Industrial Revolution in the 18th century, castings entered a new era of serving the large industry. In the 20th century, casting has developed rapidly. Nodular cast iron, malleable cast iron, ultra-low carbon stainless steel and cast metal materials such as Al-Cu, Al-Si, Al-Mg alloy, Ti-based and Ni-based alloys have been developed successively, and a new process for inoculating gray cast iron has been invented. After the 1950s, new technologies such as high pressure moulding of wet sand, chemical hardening sand moulding and core-making, negative pressure moulding and other special foundry and shot blasting cleaning appeared.
5. There are many kinds of foundry, which are customarily divided into:
(1) Ordinary sand mold casting, including wet sand mold, dry sand mold and chemical hardening sand mold. (2) Special casting can be divided into special casting with natural mineral sand and stone as main moulding materials (such as investment casting, clay casting, shell casting in foundry workshop, negative pressure casting, solid casting, ceramic casting, etc.) and special casting with metal as main moulding materials (such as metal mould casting, pressure casting, continuous casting, low pressure casting, centrifugal casting, etc.). The two category.
6. Casting process usually includes:
(1) The preparation of casting mould (making liquid metal a container for solid casting) can be divided into sand mould, metal mould, ceramic mould, mud mould and graphite mould according to the materials used, and can be divided into disposable mould, semi-permanent mould and permanent mould according to the number of times used. The quality of casting preparation is the main factor affecting the quality of casting.
(2) Melting and pouring of casting metals, casting metals (casting alloys) mainly include cast iron, cast steel and cast non-ferrous alloys;
(3) Casting treatment and inspection, including removal of foreign bodies from core and surface of castings, removal of gating risers, relief burrs and drapes, heat treatment, shaping, rust prevention and rough processing.