Forging may be hot, cold, or warm depending on temperature. Hot forging is best for metal shaping. Steel forging manufacturers make use of hot forging extensively. During hot forging, the metal is heated beyond its recrystallization temperature. This temperature is the point at which new grains are created in the metal. This kind of intense heat is essential to prevent the metal from becoming too rigid as it is being shaped.
Friction is a significant factor in the hot forging manufacturing process
Friction is a significant factor in the industrial production process under actual operating circumstances. The frictional forces occurring at the contact between the die and the workpiece hinder the material from spreading along the surfaces, but the material in the center may expand with more ease. The outcome is the formation of a cylindrical shape for the component. The phenomenon described is often referred to as “barreling” in the context of metal forging.
Barreling is often undesired and may be mitigated by using efficient lubrication. Another factor to take into account in the hot forging manufacturing process is the heat transfer between the hot metal and the cooled die, which typically contributes to the barreling effect. The metal in proximity to the die surfaces undergoes more rapid cooling compared to the metal located toward the center of the component. The colder material exhibits more resistance to deformation and experiences a lower degree of expansion compared to the hotter material located in the center, hence resulting in a barreling effect.
The benefits of the hot forging manufacturing process
- The metal exhibits high strain rates, resulting in effortless flow
- Recrystallization and recuperation are feasible
- The needed forces are a little
The drawbacks of the hot forging manufacturing process include:
- High-temperature lubrication poses challenges
- The workpiece experiences oxidation and scaling
- Inadequate surface quality
- Narrower tolerances
- Potential deformation of the material during the cooling phase.
How to Identify the Hot Forging Process?
The hot forging manufacturing process takes place at temperatures higher than the recrystallization temperature of a metal. The term “homologous temperature” (TH) is used to differentiate it from the cold forging process. The equation TH = 0.6 x TS represents the relationship between TH (the temperature at which a material starts to melt) and TS (the melting temperature of the substance), with all values given in Kelvin (K). When the temperature of the process exceeds TH, it is categorized as hot forging.
This does not necessarily imply that the substance must be subjected to heat. Recrystallization occurs at room temperature in metals with low melting points, such as lead. Hot forming results in a substantial decrease in material strength (yield stress) when temperatures above TH. The forming component acquires a viscoelastic texture.
Recrystallization creates a new metal crystalline lattice structure, causing the phenomena. To produce outstanding formability:
- Reduce strain hardening in the metal
- Activate dislocations with thermal energy, and
- Facilitate recovery and recrystallization during and after forging.
Hot forging is used to attain intricate 3D shapes
Hot forging is used by automotive components manufacturers to attain intricate 3D shapes via the process of shaping. Furthermore, it facilitates the manipulation of materials that are difficult to shape, since they can only be created with certain restrictions under low temperatures. Hot forging circumstances result in a decrease in strength, which in turn reduces the force and effort required for the procedures, as compared to cold forming.
Recrystallization demonstrates the ideal amalgamation of robustness and malleability
Recrystallization is responsible for the development of a fine-grained microstructure by completely reforming the microstructure, maybe numerous times. It demonstrates the ideal amalgamation of robustness and malleability. Hot forging is considered a crucial manufacturing method for producing safety components that are subjected to high levels of stress.
Hot Forging is suitable for components that need to withstand high operating loads
The process of recrystallization occurs when exposed to high temperatures, resulting in improved formability and the ability to finely modify the microstructure. Hot die forging is a manufacturing method that may be designed to have superior strength and durability compared to other forming processes. It is particularly suitable for components that need to withstand high operating loads, both static and dynamic. Typically, these components are known as “Safety Critical Parts”. Hence, the automobile and aerospace industries are the primary consumer markets for hot forgings. This is the reason steel forging manufacturers around the globe embrace this technology.
Forged components designed for use in the automotive industry
The primary use of steel forging is in the automobile industry. The desire for lightweight construction is driving the use of wrought aluminum alloys, whereas the utilization of magnesium is uncommon. In the volume category, components are mostly manufactured by the top automotive components manufacturers in small to medium quantities using the closed die forging technique. This allows for the use of automotive components that possess exceptional durability and operational efficiency.
Below is a list of common automobile forgings. The examples are relevant for both passenger automobiles and commercial vehicles.
- Engine parts include pistons, connecting rods, camshafts, crankshafts, valves, distributor housings, and balance shafts.
- Driving gear includes pinions, synchronizer rings, and CVTs.
- The powertrain has flange yokes, peg carriers, wheel hubs, driving shafts, universal joints, and joint discs.
- The undercarriage includes wheel carriers, axle journals, pivot bearings, axle and ball stubs, steering levers, front axle beams, and wishbones.
- Brake plates, carriers, cylinders, and handles comprise the braking system.
Forgings for aerospace usage with exceptional temperature resistance
- The fuselage comprises several components, including door and wing fittings, ribs, and window frames.
- The engine consists of turbine blades, a thrust cone, discs, and control levers.
- Components and tracks for the tail assembly
- The landing gear consists of a carrier, fasteners, and pins.
- Components of rotor systems include fittings, rotor heads, and gearbox covers.
In the aerospace industry, in addition to steel forgings, specialized materials with high strength and temperature resistance, such as nickel-based and titanium alloys are used. Furthermore, lightweight construction materials such as wrought aluminum alloys and magnesium are also employed.
Supplementary Application Fields
Hot forging is applicable outside the automobile and aerospace industries. In addition, hot forgings may demonstrate their merits in several other significant application areas.
- Building sector
- Engineering discipline that applies principles of physics, mathematics, and materials science to design, analyze, and manufacture mechanical systems.
- Agriculture and the defense industry.
- Steel construction in the offshore industry.
- Public health sector
- The field of precision engineering and horology
What are the advantages of hot forging over steel casting?
Steel casting involves heating the steel to its melting point and then pouring the molten steel into a mold to produce the required form and size. On the other hand, steel forging alters the shape of the metal while it is in a solid state by applying intense thermal and mechanical force.
Through the steel forging process, the inherent coarse grain structure of the metal faces disruption and gets substitution with a more refined grain structure. Steel forging, carried out by the leading steel forging manufacturers enhances structural integrity and yields steel components that are superior in strength and reliability compared to cast steel equivalents. The steel forging method is more economically efficient in comparison to other metalworking techniques.
Conversely, casting yields steel components that are more susceptible to flaws. Possible causes of these flaws include the following:
- Uneven cooling
- Mold failure
- Low metal temperature
- Inadequate venting
- The use of cold dies
- Contaminated metal, and
- Excessive lubrication.
The primary benefits of using forged steel components
Forged steel components provide superior strength. Cast steel parts surpass in strength, durability, and impact resistance by these components, owing to their dense structure and controlled alignment of metal grains. Furthermore, the forging process effectively eradicates any internal gaps, reduces the porosity of the products, and ensures the appropriate alignment of grain flow, resulting in exceptional directional, structural, impact strength, and fatigue resistance.
Forged steel components exhibit higher reliability and greater ductility. The forging technique effectively avoids metallurgical flaws, including cracks, hot tears, hot spots, cold shuts, shrinkage, misruns, and inclusions. This makes it highly suitable for manufacturing more crucial components. Due to all these upsides, steel forging manufacturers around the globe prefer this technology to others.
Hot forging is a more economical option. Forging necessitates a smaller initial amount of material and generates minimum waste. Additionally, it requires fewer machining efforts to get the appropriate surface quality, resulting in decreased production time and diminished equipment deterioration.
Furthermore, steel forging offers enhanced manufacturing efficiency and reduced rates of rejection. Manufacturing efficiency and cost-effectiveness need enhancement through the use of ingots or billets of varying sizes to produce identical components. Forging, due to its ability to create steel parts with strong structural integrity, greatly decreases the occurrence of rejected components.
Utilizations and Practical Implementations
Cars and trucks employ forged steel powertrains, axle beams, shafts, wheel spindles, and kingpins. Manufacturers of valves, fittings, hand tools, hardware, industrial, heavy construction, and mining equipment use them. Forged components find applications in the ordnance, shipbuilding, and aerospace sectors.
