What is casting? Casting refers to a process in which a solid metal is melted
into a liquid form and poured into a mold of a specific shape to be solidified
and formed. The metal to be cast includes: copper, iron, aluminum, tin, lead,
etc. The materials of the ordinary mold are raw sand, clay, water glass, resin
and other auxiliary materials. Special casting molds include: investment
casting, lost foam casting, metal casting, ceramic casting, etc. (Original sand
includes: quartz sand, magnesia sand, zircon sand, chromite sand, forsterite
sand, lanite sand, graphite sand, iron sand, etc.) Early castings are mostly
tools for agricultural production, religion, life, etc. Or utensils, artistic
color is strong.
After the industrial revolution of the 18th century, industries such as steam
engines, textile machines and railways rose, castings entered a new era of
service for large industries, and casting technology began to develop. In the
20th century, castings developed rapidly. One of the important factors is that
advances in product technology require better mechanical and physical properties
of castings, while still having good machining performance. Another reason is
the machinery industry itself and other industries. The development of such
industries as chemicals and meters has created favorable material conditions for
the foundry industry. For example, the development of testing methods ensures
the improvement and stability of casting quality and provides conditions for the
development of casting theory. Inventions such as electron microscopy have
helped people penetrate into the microscopic world of metals, explore the
mysteries of metal crystallization, study the theory of metal solidification,
and guide casting production. During this period, a large number of new cast
metal materials with excellent performance and rich variety, such as ductile
iron, weldable malleable cast iron, ultra-low carbon stainless steel,
aluminum-copper, aluminum-silicon, aluminum-magnesium alloy, titanium-based,
nickel-based alloy, etc.
And invented a new process for the inoculation of gray
cast iron, making the casting more adaptable. After the 1950s, there were new
technologies such as wet sand high pressure molding, chemical hardening sand
molding and core making, negative pressure molding (see negative pressure
casting) and other special casting and shot blasting (see casting cleaning),
which made the castings very high. The shape, dimensional accuracy and good
surface finish are also greatly improved in the foundry's working conditions and
environmental hygiene. In the major progress of the foundry industry since the
20th century, the two new processes of gray cast iron gestation treatment and
chemical hardening sand styling have special significance. These two inventions
have broken through the traditional methods that have lasted for thousands of
years, opening up new fields for the casting process and having a major impact
on improving the competitiveness of castings. Many structural parts and main
components of copper castings are made of castings, and they are closely related
to the quality and precision of copper. The quality of copper castings has a
vital impact on the quality, life and precision of machine tools. Copper
castings can be used in valves, speakers, injection molding machines, water
pipes, etc. .
There are many classification methods for castings: according to
the metal materials used, they are divided into steel castings, cast iron parts,
cast copper parts, cast aluminum parts, and copper castings. Each type of
casting can be further divided into different varieties according to its
chemical composition or metallographic structure. For example, cast iron parts
can be divided into gray cast iron parts, malleable cast iron parts, alloy cast
iron parts, etc.; according to the different molding methods, the castings can
be divided into ordinary sand castings, metal castings, die castings, ceramic
castings, electroslag remelting castings. Parts, bimetal castings, etc. Among
them, ordinary sand castings are the most widely used, accounting for about 80%
of all castings. Non-ferrous metal castings such as aluminum, magnesium and zinc
are mostly die-casting parts.
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