How to distinguish casting and forging

2022-08-14
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How to distinguish casting and forging

I. casting:

1. Casting: the process of melting metal into a liquid that meets certain requirements and pouring it into the mold. This kind of experimental machine has a small stroke. After cooling, solidification and cleaning, it can obtain castings (parts or blanks) with predetermined shape, size and performance. The basic technology of modern machinery manufacturing industry

2. The cost of blank produced by casting is low, which can show its economy for parts with complex shapes, especially those with complex cavities; At the same time, it has wide adaptability and good comprehensive mechanical properties

3. However, there are many materials (such as metal, wood, fuel, molding materials, etc.) and equipment (such as metallurgical furnace, sand mixer, molding machine, core making machine, desander, shot blasting machine, cast iron plate, etc.) required for casting production, and dust, harmful gases and noise will be produced to pollute the environment

4. Casting is a metal hot working process that human beings have mastered earlier, with a history of about 6000 years. In 3200 BC, copper frog castings appeared in Mesopotamia. From the 13th century BC to the 10th century BC, China has entered the heyday of bronze castings, and the technology has reached a quite high level. For example, the 875 kg Si Mu Wu Fang Ding of the Shang Dynasty, the Yi zunpan of marquis Zeng of the Warring States period, and the transparent mirror of the Western Han Dynasty are all representative products of ancient casting. Early 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 BC, China cast the world's first recorded iron casting, the Jin Ding (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 big industry. In the 20th century, casting has developed rapidly. Ductile iron, malleable iron, ultra-low carbon stainless steel, aluminum copper, aluminum silicon, aluminum magnesium alloys, titanium based, nickel based alloys and other casting metal materials have been developed successively, and a new process for inoculation treatment of gray cast iron has been invented. After the 1950s, new processes such as wet sand high-pressure molding, chemically hardened sand molding, coring, negative pressure molding, and other special casting and shot blasting appeared

5. There are many kinds of casting, which are customarily divided into: ① ordinary sand mold casting, including wet sand mold, dry sand mold and chemical hardening sand mold. ② According to the molding materials, special casting can be divided into two types: special casting with natural mineral sand as the main molding materials (such as investment casting, mud mold casting, shell mold casting in foundry, negative pressure casting, full mold casting, ceramic mold casting, etc.) and special casting with metal as the main molding materials (such as metal mold casting, pressure casting, continuous casting, low-pressure casting, centrifugal casting, etc.)

6. The casting process usually includes: ① preparation of the mold (the container that makes the liquid metal into the solid casting). The mold can be divided into sand mold, metal mold, ceramic mold, clay mold and graphite according to the materials used. How to choose a suitable tension machine? The following are the summarized steps: mold, etc., which can be divided into disposable mold, semi permanent mold and permanent mold according to the number of times of use. The quality of mold preparation is the main factor affecting the quality of castings; ② The melting and pouring of cast metals, cast metals (cast alloys) mainly include cast iron, cast steel and cast non-ferrous alloys; ③ Processing and inspection of castings, including removal of foreign matters on the core and surface of castings, removal of sprue and riser, chipping and grinding of burrs, seams and other protrusions, as well as heat treatment, shaping, rust prevention treatment and rough machining. Imported pump valve

II. Forging:

1. Forging: it is a processing method that uses forging machinery to exert pressure on metal blanks to produce plastic deformation, so as to obtain forgings with certain mechanical properties, certain shapes and sizes

2. One of the two major components of forging. Through forging, the loose as cast metal and welding holes can be eliminated. The mechanical properties of forgings are generally better than those of the same material. The main body of hydraulic universal material testing machine should use frame level or use the plumb bob in the attachment to calibrate the verticality of the column in two directions perpendicular to each other. For important parts with high load and severe working conditions in machinery, forgings are mostly used, except for rolled plates, profiles or weldments with simple shape

3. Forging can be divided into: ① open forging (free forging). The metal is deformed between the upper and lower buttresses (anvils) by impact or pressure to obtain the required forgings, mainly including manual forging and mechanical forging. ② Closed mode forging. Forgings are obtained by pressing and deforming metal blanks in a forging die chamber with a certain shape, which can be divided into die forging, cold heading, rotary forging, extrusion, etc. According to the deformation temperature, forging can be divided into hot forging (the processing temperature is higher than the recrystallization temperature of the blank metal), warm forging (lower than the recrystallization temperature) and cold forging (normal temperature)

4. The forging materials are mainly carbon steel and alloy steel with various components, followed by aluminum, magnesium, titanium, copper and their alloys. The original state of the material includes bar, ingot, metal powder and liquid metal. The error within all measuring ranges can be controlled within 0.5% in the same direction. The ratio of the cross-sectional area of the metal before deformation to the die sectional area after deformation is called the forging ratio. Correct selection of forging ratio has a great relationship with improving product quality and reducing cost

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