Casting and forging dies

In mold making, we usually hear casting and forging. What is the difference between the two manufacturing processes?

One casting

Casting is a process in which a metal is smelted into a liquid that meets certain requirements, poured into a mold, and cooled, solidified, and cleaned to obtain a casting (part or blank) having a predetermined shape, size, and performance. The basic process of industry.

The blank produced by casting has low cost, and it can show its economicality for parts with complicated shapes, especially those with complex inner cavity; at the same time, it has wide adaptability and good comprehensive mechanical properties. However, materials required for casting production (such as metal, wood, fuel, modeling materials, etc.) and equipment (such as metallurgical furnaces, sand mixers, molding machines, core making machines, falling sand machines, shot blasting machines, cast iron plates, etc.) It is polluted by dust, harmful gases and noise.

1. There are many kinds of castings, which are habitually divided according to the modeling method:

1 Ordinary sand casting, including wet sand type, dry sand type and chemical hardening sand type.

2Special casting, according to the modeling material, can be divided into special castings with natural mineral sandstone as the main modeling material (such as investment casting, clay casting, casting workshop shell casting, negative pressure casting, solid casting, ceramic casting). Etc.) and special castings with metal as the main casting material (such as metal casting, pressure casting, continuous casting, low pressure casting, centrifugal casting, etc.).

2. The casting process usually includes:

1 mold (to make liquid metal into a container for solid casting) preparation, mold can be divided into sand type, metal type, ceramic type, mud type, graphite type according to the materials used; can be divided into disposable type and semi-permanent type according to the number of times of use And permanent. The pros and cons of casting preparation are the main factors affecting the quality of castings;

2 melting and casting of cast metal, cast metal (casting alloy) mainly cast iron, cast steel and cast non-ferrous alloy;

3 casting processing and inspection, casting processing includes removal of core and casting surface foreign matter, refining riser, burr and burr and other projections, as well as heat treatment, shaping, anti-rust treatment and roughing.

2. Forging

Forging is a processing method that uses a forging machine to apply pressure to a metal blank to plastically deform it to obtain a forging with certain mechanical properties, a certain shape and size, and is one of the two major components of forging.

Through forging, it can eliminate the as-cast looseness and weld hole of the metal, and the mechanical properties of the forging are generally superior to those of the same material. For important parts with high load and severe working conditions in machinery, forgings are often used except for rolled sheets, profiles or welded parts that are simple in shape.

1. Forging according to the forming method

1 open forging (free forging)

The impact force or pressure is used to deform the metal between the upper and lower stellite irons (anvil) to obtain the required forgings, mainly hand forging and mechanical forging.

2 closed mode forging

The metal blank is subjected to compression deformation in a forging die having a certain shape to obtain a forged piece, which can be classified into die forging, cold heading, rotary forging, extrusion, and the like.

2. According to the deformation temperature

Forging can be further divided into hot forging (processing temperature is higher than the recrystallization temperature of the blank metal), warm forging (below the recrystallization temperature) and cold forging (normal temperature).

The forging materials are mainly carbon steel and alloy steel of various compositions, followed by aluminum, magnesium, titanium, copper and the like and alloys thereof. The raw state of the material is bar, ingot, metal powder and liquid metal. The ratio of the cross-sectional area of ​​the metal before deformation to the area of ​​the die after deformation is called the forging ratio. Proper selection of forging ratios has a lot to do with improving product quality and reducing costs.

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Mold forming process

Casting mold means that in order to obtain the structural shape of the part, the structural shape of the part is made in advance with other easily formed materials, and then the mold is placed in the sand type, so that a cavity having the same structural size as the part is formed in the sand type. A fluid liquid is then poured into the cavity, and the liquid is cooled and solidified to form a part identical to the shape of the mold.

According to different working conditions, it is mainly divided into the following types of processes:

1. Ordinary die forging:

Ordinary die forging is to place a heated or unheated metal blank in a mold cavity. Under the influence of impact or pressure. The geometry of the metal is varied to obtain a forging that is consistent with the cavity. Ordinary die forging includes hot forging and pier forging. Pier forging can also be divided into warm piers, cold piers, and hot piers;

2, squeeze:

Extrusion is the placement of a metallic material in an extruded mold cavity. Apply strong pressure to one end. The casting mold material is deformed in a state of being accepted in three directions. Thereby flowing out of the die hole at one end. Get parts of different shapes. Classified according to the direction of motion of the punch and material. Extrusion can be divided into positive extrusion, reverse extrusion, composite extrusion, radial extrusion and the like. According to the billet temperature, it can be divided into hot extrusion, cold extrusion and warm extrusion;

3, pull:

At the time of drawing, the material was pressed in both directions and was always pulled. Formed by casting a die hole in the mold. Obtain blanks, profiles, and parts of the required shape and size. Pulling can be divided into extubation, drawing, and the like. The products obtained by drawing have higher precision and lower surface roughness, and are often used for reworking of rolled bars and tubes to improve quality;

4, stamping:

Stamping is the use of a die to deform or separate the material. Thereby obtaining a processing method of the part. Stamping can obtain parts with complex shapes, good surface quality and high precision. Casting molds have high productivity and low cost, and stamping can be mainly divided into two types: forming process and separation process. The separation process includes punching, blanking, trimming, trimming, etc.; the forming process includes drawing, bending, expanding, tumbling, and schooling;

5, die casting:

Die casting is a process in which a molten metal is injected at a high pressure into a cavity of a die-casting mold at a high pressure and solidified under pressure to form a casting;

6, plastic molding:

The plastic molding is under the action of pressure, and the casting mold molds the powder or the heavier plastic in the mold to obtain a plastic product of a desired shape and size. Plastic molding can be divided into extrusion molding, compression molding, injection molding and other processes.

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What are the effects of lost foam coatings?

Lost foam casting has many kinds of processing methods in China. Different lost foam casting methods have different requirements on coating properties. The casting system and casting body have different requirements on the properties of the material. The gas permeability of the lost foam coating is accurate. It should be permeability, and the permeability of the medium temperature zone has practical value. In the selection of aggregates, the higher the refractoriness, the better. In order to ensure the good permeability of the sand, there are new requirements for the stripping property of the coating. The method of making and using the paint has an effect on the workability and process performance of the paint.

1, the role of lost foam coating

The function of the lost foam coating is to support and protect the foam model, prevent the liquid metal from infiltrating into the sand and sand, absorb the cracked product and allow the cracked gas to pass through the coating, keep the cavity air gap formed by the foam model cracking intact, and hold the liquid Metal heat does not dissipate quickly. Therefore, the use of the lost foam coating can reduce the surface roughness of the casting, ensure the accuracy of the casting, reduce or prevent the casting sand, sand holes, pores, metal penetration, cold insulation, pouring, carbon deposition and other defects. Therefore, the lost foam coating should have sufficient refractoriness, certain mechanical strength, proper thermal and thermal conductivity, proper gas permeability and ability to absorb liquid cracking products, smooth surface, sufficient coating performance, and no foam model. A chemical reaction occurs.

2, the performance of the lost foam coating

The properties of lost foam coatings include many indicators: strength, gas permeability, refractoriness, thermal insulation, rapid cooling resistance, rapid heat, wettability, thixotropy, varnishing, dripping, suspension, etc. These performance indicators can be Classified into two categories: work performance and process performance

Coating strength, gas permeability, refractoriness, thermal insulation, and resistance to rapid cooling and heat are all workability. The most important of these are strength and breathability. Lost foam coatings require high strength and high gas permeability, which is different from other foundry coatings.

The coating properties, dripping properties and suspension properties of the coatings are process properties. In order to reduce the cost of foam casting, water-based coatings are often used. Therefore, water-based coatings and organic foam moldings do not wet, and it is necessary to improve the coating properties of coatings, which is a major process performance of lost foam coatings. Another major process performance is the dripping of the coating. After the dipping coating, the pattern is generally suspended and dried. It is hoped that the coating can be leveled and not dripped as much as possible to ensure a uniform coating of a certain thickness, making full use of the coating without polluting the environment.

3. Composition design of lost foam coating

The basic components of the coating for lost foam casting include refractory materials, carriers, binders, suspending agents, preservatives, surfactants, defoamers, and the like.

Luoyang Liu’s mold reminds you to pay attention to: (1) the selection of coatings should be considered from the aspects of coating performance, preparation operation and procurement cost; (2) the permeability of coatings with alumina as the main aggregate is relatively high; (3) Poor gas permeability makes it possible to add a certain amount of organic binder and organic binder to burn in the foot-filling process to increase the micropores of the coating, which not only increases the gas permeability, but also increases the room temperature strength of the coating.

The above is the knowledge about the lost foam coating summarized by Luoyang Liu’s mold. For more details about the lost foam coating, please contact us.

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