Basic Knowledge and Advantages and Disadvantages of Forging

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Forging is the use of machinery to apply pressure to the metal blank so that it produces plastic deformation to obtain certain mechanical properties, shapes, and sizes. The forging processing method is one of the components. Through forging, the casting looseness and other defects caused by the metal in the smelting process can be eliminated. The microstructure structure can be optimized. In addition to that, the mechanical properties of the forging are generally better than the casted parts due to the preservation of complete metal streamlines.

For machinery, important parts with high loads and severe working conditions are mostly forged. This is unless they are plates, profiles, or weldment that can be rolled with simple shapes.

Deformation temperature

The initial recrystallization temperature of steel is about 727 °c, but 800 °c is generally used as the dividing line. The one above 800 °c is hot forging, and between 300 and 800 °c is warm forging or semi-hot forging. Forging at room temperature is cold forging.

Forgings used in most industries are hot forging, warm forging, and cold forging. These forging methods application is in forging parts such as automobiles and general machinery. Warm forging and cold forging can effectively save materials.

Forging Category

As mentioned above, according to the forging temperature, there is hot forging, warm forging, and cold forging. According to the forming mechanism, forging can be divided into free forging, die forging, rolling ring, special forging.

1) Free Forging

Free forging refers to forgings’ processing method that uses simple universal tools. It includes directly applying an external force to the blank between the upper and lower anvils of forging equipment to deform the blank and obtain the required geometry and internal mass. Forgings produced by the free forging method are called free forgings.

Free forging is good for the production of forgings with small batches. The forging equipment such as forging hammers and hydraulic presses are used to form the blanks and obtain qualified forgings. The basic processes of free forging include upsetting, drawing, punching, cutting, bending, twisting, staggering, and forging. Free forging takes the form of hot forging.

2) Die Forging

Die forging is divided into open die forging and closed die forging. The metal blank is deformed by pressure in the forging chamber with a certain shape to obtain the forging. The die forging is generally used to produce parts with small weight and large batches. Die forging can be divided into hot die forging, warm forging, and cold forging. Warm forging and cold forging are the future development direction of die forging and represent the level of forging technology.

According to the material, die forging can also be divided into ferrous metal die forging, non-ferrous metal die forging, and powder product molding. As the name suggests, the materials are ferrous metals such as carbon steel, non-ferrous metals such as copper and aluminum, and powder metallurgy materials.

Extrusion should be attributed to die forging, which can be divided into the heavy metal extrusion and light metal extrusion. Closed die forging and closed upsetting forging belong to the two advanced processes of die forging. Because there is no flying edge, the utilization rate of the material is high. The finishing of complex forgings can complete in one process or several processes.

With no flying edges, the force area of the forging is smaller, and the required load is also smaller. However, it should be noted that the blank cannot be completely limited. So it is necessary to strictly control the volume of the blank, control the relative position of the forging die and measure the forging, and strive to reduce the wear of the forging die.

3) Mill Ring

The ring mill refers to the production of ring parts of different diameters through the special equipment ring-milling machine. The method produces wheel-shaped parts such as automobile wheel hubs and train wheels.

4) Special Forging

Special forging includes roll forging, wedge rolling, radial forging, liquid die forging, and other forging methods, which are more suitable for the production of certain special shapes of parts. For example, roller forging is a good effective performing process to reduce the subsequent forming pressure. Wedge rolling can produce steel balls, transmission shafts, and other parts. Lastly, radial forging can produce large barrels, step shafts, and other forgings.

5) Forging Die

According to the movement mode of the forging die, forging can be divided into pendulum rolling, pendulum rotary forging, roller forging, wedge rolling, roll ring, and oblique rolling. Swing rolls, pendulum swaggers, and rings are good for precision forging. In order to improve the utilization of materials, roller forging and cross rolling are good for pre-processing processing of slender materials.

Rotary forging, like free forging, is also locally formed. Its major advantage is that it can be molded with less forging force than the size of the forging. Including free forging, this forging method, when processing, the material expands from the nearby mold surface to the free surface. Therefore, it is difficult to ensure accuracy. Computers control the direction of motion of the forging die and the rotary swaging process.

The shape of complex and high-precision products can be obtained with a lower forging force, such as the production of forgings such as steam turbine blades with many varieties and large sizes. The mold movement of forging equipment is inconsistent with the degree of freedom and may be divided into the following four forms:

Limit the form of forging force

Quasi-stroke restriction mode

Stroke restriction mode

Energy restriction mode

In order to obtain high precision, take care to prevent overload at the lower dead spot, control the speed and mold position. Because these can all have an impact on forging tolerances, shape accuracy, and die life. In addition, in order to maintain accuracy, pay attention to adjusting the slider rail clearance, ensuring stiffness, adjusting the lower dead spot, and using subsidy transmissions.

There are also vertical and horizontal movements of the slider (for forging of slender parts, lubrication cooling, and forging of parts for high-speed production), and the use of compensation devices can increase the movement in other directions.

The above methods are different. The required forging force, process, material utilization, yield, dimensional tolerances, and lubrication cooling methods are also different. These factors are also factors that affect the level of automation.

Forging Materials

Forging materials are mainly carbon steels and alloy steels of various components, followed by aluminum, magnesium, copper, titanium, and their alloys. The original state of the material is bar stock, ingot, metal powder, and liquid metal. The ratio of the cross-sectional area of the metal before deformation to the cross-sectional area after deformation is called the forging ratio. Correct selection of forging ratio, reasonable heating temperature and holding time, reasonable forging temperature and final forging temperature, reasonable deformation amount, and deformation speed has a lot to do with improving product quality and reducing costs.

Generally, small and medium-sized forgings use round or square bar stock as blanks. The grain structure and mechanical properties of the bar stock should be uniform and good. The shape and size are accurate, and the surface quality is good, which is convenient for mass production of the tissue. As long as the heating temperature and deformation conditions are reasonably controlled, you can forge without large forging deformation.

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Ingots are only used for large forgings. Ingots are cast structures with large columnar crystals and loose centers. Therefore, it is necessary to break the columnar crystals into fine grains through large plastic deformation. Then loosen and compact them in order to obtain excellent metal microstructure and mechanical properties.

Powder metallurgy material forging

Powder metallurgy prefabricated blanks formed by pressing and sintering can be made into powder forgings by flyless die forging in the hot state. Forging powder is close to the density of general die forgings, has good mechanical properties and high precision, which can reduce subsequent cutting processing. The powder forgings are evenly organized internally and have no segregation. Therefore, they are good for manufacturing workpieces such as small gears. However, the price of powder is much higher than the price of general rods. Application in production is also limited to a certain extent.

Apply static pressure to the liquid metal poured into the mold chamber so that it solidifies, crystallizes, flows, plastic deformation, and molding under pressure. That way, the desired shape and performance of the die forging can be obtained. Liquid metal die forging is a forming method between die-casting and die forging. It is suitable for complex thin-walled parts that are difficult to form in general die forging.

Other materials

In addition to the usual materials and aluminum, magnesium, copper, titanium, etc., and their alloys, iron-based superalloys, nickel-based superalloys, cobalt-based superalloys of the deformation alloy are also forged or rolled to complete. But these alloys, due to their relatively narrow plastic area, forging difficulty will be relatively large. The heating temperature of different materials, the forging temperature, and the final forging temperature have strict requirements.

Process

Different forging methods have different processes, of which the hot die forging process is the longest. The general order is: forging blanking → forging blank heating → roll forging blank → die forging forming → cutting edge → punching → correction → intermediate inspection, an inspection of forging size and surface defects → forging heat treatment, to eliminate forging stress, improve metal cutting performance → cleaning, mainly to remove surface oxide scale→ correction → inspection. General forgings to go through appearance and hardness inspection. Important forgings also need to undergo chemical composition analysis, mechanical properties, residual stress, and other tests and non-destructive testing.

Forging Features

Compared with castings, forging metals improve their microstructure and mechanical properties. After the casting structure is deformed by the forging method, due to the deformation and recrystallization of the metal, the original coarse dendrites and columnar grains become isotylic recrystallization structures with finer grains and uniform size.

So the original segregation, looseness, porosity, slag clamping, and other compaction and welding in the steel ingots, and its structure becomes more compact. This improves the plasticity and mechanical properties of the metal.

The mechanical properties of castings are lower than those of forgings of the same material. In addition, forging processing can ensure the continuity of the metal fiber structure. So the fiber structure of the forging is consistent with the shape of the forging. The metal streamline is complete, and the forgings produced by precision die forging, cold extrusion, warm extrusion, and other processes guarantee the parts have good mechanical properties and a long service life, which are incomparable to the castings.

Forgings

Forgings are objects where metal is pressure applied to shape the required shape or suitable compressive force through plastic deformation. This force is typically achieved through the use of a hammer or pressure. The forging process builds a delicate granular structure and improves the physical properties of the metal. In the real-world use of parts, a correct design allows particles to flow in the direction of the main pressure.

Casting

Casting is a metal molded object obtained by various casting methods. It involves a smelted liquid metal injected into the pre-prepared mold by pouring, injection, or other casting methods. It is cooled by sand fall, cleaning, post-treatment, etc., the obtained objects with a certain shape, size, and performance.

The Advantages of Steel Forging vs Casting

Steel casting and steel forging are two distinct processes for manufacturing metal parts, each with advantages and limitations. While both casting and forging processes influence the final shape of a metal workpiece through unique heating and shaping techniques, they feature significant differences. There are many factors to consider when selecting the best method for manufacturing your product, including materials, production volume, product strength requirements, and more. So, which process will best suit your project specifications: casting or forging?

Essential Factors When Considering Forging vs Casting Services

Before deciding which process is best for your application, it's important to consider the differing capabilities of forging vs casting, as well as your project's requirements. Casting vs forging considerations include:

• Material type: Forging often utilizes high-strength steel and stainless steel materials, while casting can use a wide range of metals in producing components
• Temperature sensitivity: Forging requires high heat exposure, while casting has more variation options in heat levels
• Amount of detail required: Forging is ideal for creating relatively simple, large parts, while casting is used for creating highly detailed components
• Strength requirements: Forging excels at producing metal parts with higher strength than casted parts
• Tolerance tightness: Casting can create parts with much tighter tolerances than forged pieces
• Net waste: Casting typically produces far more net waste than forging, as forging avoids excessive material removal

By learning about the advantages and disadvantages of forging vs casting, you can choose the best process for your specific application.

The Steel Forging Process: Advantages & Disadvantages

The steel and stainless steel forging process creates parts and components in various shapes and sizes. The steel forging process produces parts with increased strength, better consistency, a tighter grain structure, and increased lifespans through the use of dies, compressive forces, and varying temperatures. There are several different forging processes, including hot, warm, and cold forging, which can be utilized in open-die and closed-die forging. The following table identifies some of the strengths and weaknesses of steel forging.

Open Die Forging

The Steel Casting Process: Advantages & Disadvantages

Casting processes utilize a mold that is injected or filled with molten metal. The metal within the mold then cools and solidifies into the form of a molded product. Steel castings are used to create parts that are too complex and intricate for forging processes. Some of the different steel casting processes include die casting, investment casting, and sand casting. The following table identifies some of the strengths and weaknesses of steel casting.

Casting vs Forging: Which is Better?

After considering the capabilities and limitations of each process, it's clear that one method isn't necessarily better than the other; instead, it depends on each project's specification requirements. So, which process is suitable for your project?

Forging is Ideal For Low-Volume, High-Strength Metal Parts

Forging is an excellent choice if your part or component requires increased strength and reliability with a cost-saving advantage. Forging is versatile and able to create high-strength custom shapes for heavy-duty applications. It is also compatible with many grades of steel and stainless steel. Industries that frequently utilize forging processes to manufacture custom parts include:

• Aerospace
• Construction
• Mining
• Oil and gas processing
• Power generation
• Press repair

Custom Forged Parts

Casting is Ideal for High-Volume Production Requiring Tight Tolerances

If increased production rates and higher tolerances are needed, casting may be the best option. While casting requires additional time and cost at the front end of the process to create the cast, high-volume production runs can move quickly once the cast is made. Casting can also produce exceptionally tight tolerances, making it an ideal process for small, intricate components. Industries that rely on casting for high-volume production of parts include:

• Automotive
• Consumer goods
• Electronics
• Manufacturing
• Medical

Contact Us to Learn More About Forging Vs Casting

At Great Lakes Forge, we specialize in producing open-die forged parts and components in a wide range of materials. Not sure if forging or casting is the right process for your application? Contact us online or call 800-748-, and our team of metal forging experts will help you determine if forging or casting is the best process for your application. For all your custom forging needs, choose Great Lakes Forge.

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