Rolling Mill Production Line: Forging VS Casting

Thursday, May 19, 2022

Forging VS Casting

1. Differences between Forging and Casting:

1.1 Different Definitions:

Forging: use hammering and other methods to make the metal material in the plastic state into a workpiece with a certain shape and size, and change its physical properties.

Casting: the processing method of melting metal into a liquid, pouring it into the mold, cooling, solidification, and cleaning to obtain the casting with the required shape. It can be made into various objects with complex shapes.

1.2 Different Manufacturing Processes:

Forging: it is a processing method that uses forging machinery to exert pressure on the metal blank and make it produce plastic deformation to obtain forgings with certain mechanical properties, certain shapes, and sizes. It is one of the two components of forging (forging and stamping).

Casting: it is a method of casting liquid metal into the casting cavity corresponding to the shape of the part, and obtaining the part or blank after it is cooled and solidified.

2. Forging and Casting Purposes:

Forging is generally used in the processing of forgings with a certain shape and size.

Casting is an economical blank forming method, which is generally used in parts with complex shapes.

3. Advantages and Disadvantages of Forging and Casting:

3.1 Forging Advantages:

Forging can eliminate the defects such as cast porosity in the smelting process and optimize the microstructure. At the same time, due to the preservation of a complete metal streamline, the mechanical properties of forgings are generally better than those of castings of the same material. For important parts with high load and severe working conditions in relevant machinery, forgings are mostly used, except for rolled plates, profiles, or weldments with a simple shape.

3.2 Casting Advantages:

1）It can produce parts with complex shapes, especially blanks with complex cavities.

2) Wide adaptability. Metal materials commonly used in industry can be cast, ranging from a few grams to hundreds of tons.

3) Raw materials come from a wide range of sources and are cheap, such as scrap steel, scrap parts, chips, etc.

4) The shape and size of the casting are very close to the parts, which reduces the cutting amount and belongs to non-cutting processing.

5) It is widely used. 40% ~ 70% of the weight of agricultural machinery and 70% ~ 80% of the weight of machine tools are castings.

3.3 Forging Disadvantages:

In forging production, trauma accidents are easy to occur.

3.4 Casting Disadvantages:

1) The mechanical properties are not as good as forgings, such as coarse structure, many defects, etc.

2) In sand casting, single-piece and small-batch production have high labor intensity.

3) The casting quality is unstable, there are many processes, and the influencing factors are complex, which is easy to produce many defects.

Forging is one of the important methods of metal plastic processing. The main purpose of forging is forming and modification (improvement of mechanical properties and internal structure). The latter is difficult to realize by other process methods. In addition, forging production also has the advantages of metal saving, high production efficiency, and great flexibility.

Through forging, the porosity and pores in the casting structure can be compacted, and the coarse casting structure (dendritic grains) can be broken into fine grains to firm fiber structure. When the fiber structure is reasonably distributed along the contour of the part, the mechanical properties of the part can be improved. Therefore, the forged parts have high strength and can withstand greater impact load.

Under the same impact load, the size of forged parts can be reduced, that is, metal can be saved. For example, the United States uses a 315mn hydraulic press to die to forge 272 parts and 3200 screws of F-102 J, which reduces the weight of the aircraft and replaces 45.5 ~ 54.5kg.

Casting is a manufacturing process in which molten metal liquid is poured into the mold and cooled and solidified to obtain the required shape and properties. Casting is a common manufacturing method with low manufacturing costs and great process flexibility. It can obtain complex shapes and large castings. It accounts for a large proportion of mechanical manufacturing, such as machine tools account for 60 ~ 80%, automobiles account for 25% and tractors account for 50 ~ 60%.

Due to the improvement of casting quality, casting precision, casting cost, and casting automation, casting technology is developing towards precision, large-scale, high-quality, automation, and cleaning. For example, China has developed rapidly in precision casting technology, continuous casting technology, special casting technology, casting automation, and casting molding simulation technology in recent years.

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