Casting process the most complete explanation!

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

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

Process characteristics:

1, can produce any complex shape parts, especially the shape of the cavity complex parts.

2, strong adaptability, alloy types are not limited, casting size is almost unlimited.

3, a wide range of material sources, waste can be remelted, equipment investment is low.

4, high scrap rate, low surface quality, poor labor conditions.

Casting classification:

(1)sand casting

Sand casting: Casting method for producing castings in sand molds. Steel, iron, and most nonferrous alloy castings can be obtained by sand casting.

Technical Features:

1. Suitable for making blanks with complex shapes, especially with complex cavities;

2. Wide adaptability and low cost;

For some materials with poor plasticity, such as cast iron, sand casting is the only forming process for manufacturing parts or blanks.

Application: Automobile engine cylinder block, cylinder head, crankshaft and other castings

(2)investment casting

Investment casting: usually refers to the pattern made of fusible materials, coated with several layers of refractory materials on the surface of the pattern to make a shell, and then melted out of the shell to obtain a mold without parting surface. After high temperature baking, it can be filled with sand casting. Often referred to as "lost wax casting."

process characteristics

Advantages:

1. High size accuracy and geometric accuracy;

2, high surface roughness;

3, can cast complex shape castings, and casting alloys are not limited.

Disadvantages: complicated process, high cost

Application: It is suitable for producing small parts with complex shape, high precision requirements, or difficult to process other parts, such as turbine engine blades.

(3)die casting

Die-casting: is the use of high pressure liquid metal high-speed pressure into a precision metal mold cavity, liquid metal cooling solidification under pressure to form castings.

process characteristics

Advantages:

1. High pressure and fast flow rate of metal liquid during die-casting

2. Good product quality, stable size and good interchangeability;

3, high production efficiency, die-casting mold use times;

4, suitable for mass production, good economic benefits.

Disadvantages:

1, castings are easy to produce fine pores and shrinkage.

2, die casting low plasticity, not suitable for impact load and vibration under the circumstances of work;

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

Application: Die casting was first used in the automotive industry and instrument industry, and later gradually expanded to various industries, such as agricultural machinery, machine tool industry, electronics industry, defense industry, computers, medical equipment, watches, cameras and daily hardware and other industries.

(4)Low pressure casting

Low pressure casting: refers to the method of filling the mold with liquid metal under low pressure (0.02~0.06MPa) and crystallizing under pressure to form castings.

Technical Features:

1. The pressure and speed of casting can be adjusted, so it can be applied to various molds (such as metal molds, sand molds, etc.), casting various alloys and castings of various sizes;

2, the use of bottom injection type filling, metal liquid filling stable, no splash phenomenon, can avoid gas involvement and scouring of the mold wall and core, improve the qualified rate of castings;

3, casting crystallization under pressure, casting structure dense, clear outline, smooth surface, high mechanical properties, especially beneficial for the casting of large thin-walled parts;

4, eliminating the feeding riser, metal utilization increased to 90~98%;

5, low labor intensity, good working conditions, simple equipment, easy to achieve mechanization and automation.

Application: Mainly traditional products (cylinder head, wheel hub, cylinder frame, etc.).

(5)centrifugal casting

Centrifugal casting: pouring molten metal into a rotating mold, filling the mold and solidifying it under centrifugal force.

process characteristics

Advantages:

1. There is almost no metal consumption in the gating system and riser system, and the process yield is improved;

2, the production of hollow castings can not be used core, so in the production of long tubular castings can greatly improve the metal filling ability;

3. High casting density, few defects such as porosity and slag inclusion, and high mechanical properties;

4, easy to manufacture cylinder, sleeve composite metal castings.

Disadvantages:

1. There are certain limitations when it is used for the production of special-shaped castings;

2. The diameter of the inner hole of the casting is inaccurate, the surface of the inner hole is rough, the quality is poor, and the machining allowance is large;

3, castings easy to produce specific gravity segregation.

Applications:

Centrifugal casting was first used to produce cast pipes. Centrifugal casting technology was used in metallurgy, mining, transportation, drainage machinery, aviation, national defense, automobile and other industries at home and abroad to produce steel, iron and non-iron carbon alloy castings. Among them, centrifugal cast iron pipe, internal combustion engine cylinder liner and sleeve casting production is the most common.

(6)permanent mold casting

Metal mold casting: refers to the liquid metal under gravity filling metal mold and cooling solidification in the mold to obtain a casting method.

process characteristics

Pros:

1, metal mold thermal conductivity and heat capacity is large, cooling speed is fast, casting structure is dense, mechanical properties are about 15% higher than sand casting.

2. castings with higher size accuracy and lower surface roughness values can be obtained, and the quality stability is good.

3, due to the use of sand core and rarely, improve the environment, reduce dust and harmful gases, reduce labor intensity.

Disadvantages:

1, the metal mold itself has no permeability, must adopt certain measures to export the air in the cavity and the gas generated by the sand core;

2, metal mold without concession, casting solidification is easy to produce cracks;

3, metal mold manufacturing cycle is longer, the cost is higher. Therefore, only in mass production, in order to show good economic results.

Application: Metal mold casting is not only suitable for mass production of aluminum alloy, magnesium alloy and other non-ferrous alloy castings with complex shapes, but also suitable for the production of iron and steel castings, ingots, etc.

(7)vacuum die casting

Vacuum casting: advanced die-casting process that eliminates or significantly reduces pores and dissolved gases in die castings by removing gases from die casting mold cavities during die-casting, thereby improving mechanical properties and surface quality of die castings.

process characteristics

Advantages:

1. Eliminate or reduce the porosity inside the die casting, improve the mechanical properties and surface quality of the die casting, and improve the plating performance;

2, reduce the back pressure of the cavity, you can use a lower specific pressure and casting performance of the alloy, it is possible to use a small machine die-casting larger castings;

3, improve the filling conditions, die-casting thinner castings;

Disadvantages:

1. The mold seal structure is complex, and it is difficult to manufacture and install, so the cost is higher;

2, vacuum die-casting method such as improper control, the effect is not very significant.

(8)squeeze casting

Squeeze casting: is to make liquid or semi-solid metal solidification under high pressure, flow forming, directly obtain parts or blank method. It has the advantages of high utilization rate of liquid metal, simplified process and stable quality. It is an energy-saving metal forming technology with potential application prospects.

Direct squeeze casting: spray coating, alloy casting, mold closing, pressurization, pressure maintenance, pressure relief, mold parting, blank stripping, reset;

Indirect squeeze casting: spray coating, mold closing, feeding, filling, pressurization, pressure maintenance, pressure relief, mold parting, blank stripping, reset.

Technical Features:

1, can eliminate internal pores, shrinkage and porosity and other defects;

2. Low surface roughness and high size accuracy;

3, can prevent the production of casting cracks;

4, easy to achieve mechanization, automation.

Application: Can be used to produce various types of alloys, such as aluminum alloy, zinc alloy, copper alloy, ductile iron, etc.

(9)expendable casting process

Lost foam casting (also known as solid casting): it is a new casting method that combines paraffin or foam models similar to casting size into model clusters, brushes refractory coatings and dries, embeds them in dry quartz sand for vibration molding, pours under negative pressure, vaporizes the model, liquid metal occupies the model position, and solidifies and cools to form castings.

Process flow: pre-foaming → foaming molding → dipping coating → drying → molding → casting → shakeout → cleaning

Technical Features:

1, casting precision is high, no sand core, reducing the processing time;

2, no parting surface, flexible design, high degree of freedom;

3, clean production, no pollution;

Reduce investment and production costs.

Application: Suitable for producing precision castings of various sizes with complex structure, alloy types are not limited, and production batches are not limited. Such as gray cast iron engine box, high manganese steel elbow, etc.

(10)Continuous casting: is an advanced casting method, the principle is to melt the metal, continuously poured into a special metal mold called crystallizer, solidified (crust) castings, continuously pulled out from the other end of the crystallizer, it can obtain any length or specific length of castings.

Technical Features:

1, because the metal is rapidly cooled, crystallization dense, uniform organization, good mechanical properties;

2. Save metal and improve recovery rate;

3, simplify the process, eliminate modeling and other processes, thus reducing the labor intensity; the required production area is also greatly reduced;

Continuous casting production is easy to realize mechanization and automation, and improve production efficiency.

Application: Continuous casting method can be used to cast steel, iron, copper alloy, aluminum alloy, magnesium alloy and other long castings with constant cross section shape, such as ingots, slabs, billets, tubes, etc.