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What is the Difference Between Forging and Casting?

Many people don't know what forging and casting are and don't know the difference between forging and casting? Today let's take a look together:


1. Casting:


(1). Casting: It is the process of melting metal into a liquid that meets certain requirements and pouring it into a mold. After cooling, solidification, and cleaning, a casting (part or blank) with a predetermined shape, size and performance is obtained. Casting process is the basic technology of modern machinery manufacturing industry.


(2). The cost of casting blanks is low, and for parts with complex shapes, especially with complicated inner cavities, its economy is more prominent; At the same time, it has wide adaptability and better comprehensive mechanical properties.


(3). There many materials (such as metal, wood, fuel, modeling materials, etc.) and equipments (such as metallurgical furnaces, sand mixers, molding machines, core making machines, shakeout machines, shot blasting machines, cast iron plates, etc.) requiring for casting process and they will produce dust, harmful gas and noise which causes environmental pollution.


(4). Casting is a kind of metal hot working-casting craft  that has a history of about 6000 years. In 3200 BC, copper frog castings appeared in Mesopotamia. Early casting was greatly influenced by pottery. Most of the castings were tools or utensils used in agricultural production, religion, and life, with a strong artistic color. In 513 BC, China produced the world's first iron casting in written records-the Jin Kingdom cast tripod (approximately 270 kg). Around the 8th century, Europe began to produce iron castings. After the Industrial Revolution in the 18th century, castings entered a new period of serving large industries. In the 20th century, the rapid development of casting has been developed rapidly. Ductile cast iron, malleable cast iron, ultra-low carbon stainless steel, aluminum copper aluminum silicon aluminum magnesium alloy, titanium base and nickel base alloy and other cast metal materials have been developed and new craft technology to process grey-iron castings have been created. After the 1950s, new technologies such as

wet sand molding under high pressure, chemical hardening sand molding and core forming negative pressure molding and other special casting shot blasting cleaning and so on gradually emerged .


(5). There are many types of casting. According to modeling method they  can be divided into following categories:

① Common sand casting, including wet sand, dry sand and chemical hardened sand.

② Special casting, according to the modeling material, can be divided into two kinds of special casting: one is with natural mineral sand and gravel as the main modeling material (such as investment casting, clay mold casting, shell mold casting in foundry , negative pressure casting, solid mold casting, ceramic mold casting, etc.) and another one with metal as the main mold material (such as metal mold casting, pressure casting, continuous casting, low pressure casting, centrifugal casting, etc.).


(6). Casting process usually includes:

① Casting molds (containers that make liquid metal into solid castings) preparation. The molds can be divided into sand, metal, ceramic, mud, graphite, etc., according to the materials used. And according to the number of uses they can be divided into disposable and semi-permanent and permanent molds. The quality of mold preparation is the main factor affecting the quality of castings;

②Melting and pouring of metal casting, casting metals (cast alloys) mainly include cast iron, cast steel and cast non-ferrous alloys;

③ Casting processing and inspection. Casting processing includes removal of foreign-bodies on the core and surface of castings, removal of pouring risers, shoveling of salients like burrs and drape seams, as well as heat treatment, shaping, anti-rust treatment and rough machining.


2. Forging:


(1). Forging: It is a processing method that uses forging machinery to apply pressure to metal blanks so as to cause plastic deformation to let forging material have certain mechanical properties, certain shapes and sizes.


(2). One of the two major components of forging and pressing. Through forging, the as-cast looseness of metal and welding holes can be eliminated, and the mechanical properties of forgings are generally better than those of castings of the same material. For the important parts of machinery in high load and severe working conditions, forgings are mostly used except for plate, section bar and weldment with simpler shapes that can be rolled.


(3). Forging can be divided into according to the forming method:

①. Open forging (free forging). Using impact or pressure to deform the metal between the upper and lower anvils (anvil block) to produce the required forgings, there are mainly manual forging and mechanical forging.

②. Closed forging. The blank metal is compressed and deformed in a forging die with a certain shape to become forgings, which can be divided into die forging, cold forging, rotary forging, and extrusion, etc. According to the deformation temperature, forging can be divided into heat forge (processing temperature is higher than the recrystallization temperature of the blank metal), warm forge (below the recrystallization temperature) and cold forge (normal temperature).


(4). Forging materials are mainly carbon steel and alloy steel with various compositions, followed by aluminum, magnesium, titanium, copper, etc. and their alloys. The raw state of the material includes bar stock, ingot, metal powder and liquid metal. The ratio of the cross-sectional area of the metal before deformation to the cross-sectional area after deformation is called the forging ratio. The correct selection of forging ratios has a lot to do with improving product quality and reducing costs.