Casting,the most complete introduction to the forming process of various metal materials

This article introduces several metal forming processes, including casting ((1) sand casting (2) investment casting (3) pressure casting (4) low-pressure casting (5) centrifugal casting (6) metal casting (7) vacuum die casting (8) extrusion casting (9) disappearing die casting (10) continuous casting), plastic forming ((1) forging (2) rolling (3) extrusion (4) drawing (5) stamping), machining, welding, powder metallurgy metal injection molding metal semi-solid molding 3D printing

The liquid metal is poured into the cavity of the mold that is compatible with the shape and size of the part, and then cooled and solidified to obtain a blank or part of the production method, usually called liquid metal forming or casting.

Process flow: liquid metal → filling → solidification shrinkage → casting

Process characteristics.

1.It can produce parts with any complex shape, especially the parts with complex internal cavity shape.

2, adaptable, the alloy type is not limited, the size of the casting is almost not limited.

3.Wide source of materials, scrap can be remelted, low investment in equipment.

4.High scrap rate, low surface quality and poor labor conditions.

Casting classification :

Sand casting; investment casting; pressure casting; low pressure casting; centrifugal casting; metal casting; vacuum casting; extrusion casting; disappearing mold casting; continuous casting

(1)sand casting

Sand casting: A casting method in which castings are produced in a sand mold. Steel, iron and most non-ferrous alloys castings can be obtained by sand casting method.

Process Flow:

Technical characteristics.

1, suitable for making blanks with complex shapes, especially those with complex internal cavities.

2, wide adaptability, low cost.

3, for certain materials with very poor plasticity, such as cast iron, sand casting is the only forming process to manufacture its parts or, blanks.

Applications: automotive engine cylinder block, cylinder head, crankshaft and other castings

(2)investment casting

Investment casting: Usually refers to the casting scheme in which the mold is made of fusible material, covered with several layers of refractory material on the surface of the mold to make the shell, and then the mold is melted and discharged from the shell, so as to obtain a cast without a parting surface, which can be filled with sand and poured after high temperature roasting. It is often called "lost wax casting".

Process Flow:

This article introduces several metal forming processes, including casting ((1) sand casting (2) investment casting (3) pressure casting (4) low-pressure casting (5) centrifugal casting (6) metal casting (7) vacuum die casting (8) extrusion casting (9) disappearing die casting (10) continuous casting), plastic forming ((1) forging (2) rolling (3) extrusion (4) drawing (5) stamping), machining, welding, powder metallurgy metal injection molding metal semi-solid molding 3D printing

(3)die casting

Die casting: It is the use of high pressure to press the metal liquid into a precision metal mold cavity at high speed, and the metal liquid cools and solidifies under pressure to form a casting.

Advantages.

1.High pressure on metal liquid during die-casting, fast flow rate

2, good product quality, dimensional stability, good interchangeability.

3, high production efficiency, die-casting die used more times.

4, suitable for mass production, good economic efficiency.

Disadvantages.

1, the casting is easy to produce small pores and shrinkage.

2, die casting plasticity is low, should not be in the case of shock load and vibration work.

3, high melting point alloy die casting, casting life is low, affecting the expansion of die-casting production.

Applications: die casting was first applied in the automotive industry and instrumentation industry, and later gradually expanded to various industries, such as agricultural machinery, machine tool industry, electronics industry, national defense industry, computers, medical equipment, clocks and watches, cameras and daily hardware and many other industries.

(4)low pressure casting

Low-pressure casting: It is a method of filling the casting mold with liquid metal under low pressure (0.02 to 0.06 MPa) and crystallizing under pressure to form a casting .

Process Flow:

Technical features: 1, the pressure and speed of pouring can be adjusted, so it can be applied to a variety of different casting types (such as metal type, sand type, etc.), casting a variety of alloys and various sizes of castings; 2, the use of bottom injection type filling, metal liquid filling smoothly, no splash phenomenon, can avoid the involvement of gas and the scouring of the wall and core, to improve the casting rate; 3, castings under pressure crystallization, casting organization dense, contour Clear, smooth surface, high mechanical properties, for large thin-walled parts of the casting is particularly beneficial; 4, eliminating the complementary shrinkage riser, metal utilization rate increased to 90 ~ 98%; 5, low labor intensity, good labor conditions, simple equipment, easy to achieve mechanization and automation. Application: mainly for traditional products (cylinder head, hub, cylinder frame, etc.).

(5)centrifugal casting

Centrifugal casting: It is a casting method in which the metal liquid is poured into the rotating casting mold and solidified by filling the mold under the action of centrifugal force.

Process flow:

Advantages: 1, almost no metal consumption of the pouring system and riser system, improve the process yield; 2, the production of hollow castings without core, so in the production of long tube-shaped castings can significantly improve the metal filling capacity; 3, high density of castings, porosity, slag and other defects, high mechanical properties; 4, easy to manufacture barrels, sleeves and other composite metal castings. Disadvantages: 1, used in the production of shaped castings have certain limitations; 2, the casting bore diameter is not accurate, the bore surface is relatively rough, poor quality, large machining allowance; 3, the casting is easy to produce specific gravity segregation. Applications: centrifugal casting was first used in the production of cast pipes, domestic and foreign in metallurgy, mining, transportation, drainage machinery, aviation, national defense, automotive and other industries are using centrifugal casting process to produce steel, iron and non-ferrous carbon alloy castings. In particular, centrifugal cast iron pipes, internal combustion engine cylinder liners and bushings and other castings are the most common production.

Advantages: 1, almost no metal consumption of the pouring system and riser system, improve the process yield; 2, the production of hollow castings without core, so in the production of long tube-shaped castings can significantly improve the metal filling capacity; 3, high density of castings, porosity, slag and other defects, high mechanical properties; 4, easy to manufacture barrels, sleeves and other composite metal castings.

(6)gravity die casting

Metal Casting: A molding method in which liquid metal is filled with metal castings under the action of gravity and cooled and solidified in the type to obtain castings.

Process flow.

Advantages: 1, the thermal conductivity and heat capacity of the metal type is large, the cooling rate is fast, the casting organization is dense, the mechanical properties are about 15% higher than sand castings. 2, can obtain higher dimensional accuracy and lower surface roughness value of the casting, and good quality stability. 3, because of the use of sand core and rarely, improve the environment, reduce dust and harmful gases, reduce labor intensity. Disadvantages: 1, the metal type itself is not breathable, must adopt certain measures to export the air in the cavity and the gas generated by the sand core; 2, the metal type is not yielding, the casting is easy to produce cracks when solidifying; 3, the metal type manufacturing cycle is long, the cost is higher. Therefore, it can show good economic effect only when mass production in batches. Application: Metal type casting is suitable for both mass production of non-ferrous alloy castings such as aluminum alloy and magnesium alloy with complex shapes, and also for the production of castings and ingots of iron and steel metals.

(7)vacuum die casting

Vacuum casting: Advanced die casting process that eliminates or significantly reduces the porosity and dissolved gas in die casting by removing the gas in the die cavity during the die casting process, thus improving the mechanical properties and surface quality of die castings.

Process flow.

Advantages: 1, eliminate or reduce the internal pores of die casting, improve the mechanical properties and surface quality of die casting, improve the coating performance; 2, reduce the cavity back pressure, can use lower specific pressure and casting performance of poor alloy, it is possible to use small machine die casting larger castings; 3, improve the filling conditions, can die casting thinner castings; disadvantages: 1, mold sealing structure is complex, manufacturing and installation is more difficult, so the cost is higher; 2, vacuum die casting method, such as improper control, the effect is not significant. Therefore, the cost is higher; 2, vacuum die-casting method such as improper control, the effect is not very significant.

(8)squeezing die casting

Extrusion casting: It is a method to make liquid or semi-solid metal solidify and flow into shape under high pressure, and directly obtain the manufactured parts or blanks. It has the advantages of high utilization rate of liquid metal, simplification of process and stable quality, etc. It is an energy-saving and potentially promising metal forming technology.

Process flow.

Direct extrusion casting: spraying paint, pouring alloy, closing mold, pressurizing, holding pressure, releasing pressure, parting mold, blank demolding and resetting; indirect extrusion casting: spraying paint, closing mold, feeding material, filling, pressurizing, holding pressure, releasing pressure, parting mold, blank demolding and resetting. Technical features: 1.It can eliminate internal defects such as porosity, shrinkage and shrinkage; 2.Low surface roughness and high dimensional accuracy; 3.It can prevent the generation of casting cracks; 4.It is easy to realize mechanization and automation. Application: It can be used to produce various types of alloys, such as aluminum alloy, zinc alloy, copper alloy, ductile iron, etc.

(9)Lost foam casting

Disappearing mold casting (also called solid casting): is a new casting method in which paraffin or foam models of similar size and shape to the casting are bonded and combined into a model cluster, brushed with refractory coating and dried, buried in dry quartz sand, vibrating and modeled, poured under negative pressure, so that the model is vaporized, liquid metal occupies the model position, solidified and cooled to form the casting.

Process flow: pre-foaming → foaming molding → dipping coating → drying → modeling → pouring → falling sand → cleaning

Technical features: 1, high accuracy of castings, no sand core, reducing processing time; 2, no parting surface, flexible design, high freedom; 3, clean production, no pollution; 4, reduce investment and production costs. Application: suitable for producing various sizes of more precise castings with complex structure, with unlimited alloy types and unlimited production batches. Such as gray cast iron engine cases, high manganese steel bends, etc.