Forging heat treatment is used to modify and enhance the physical qualities of a specific material. Annealing, normalising, quenching, and tempering are typical heat treatment procedures performed on steel forgings. Moreover, applying precipitation hardening to superalloys, titanium, and certain PH stainless steels.
To achieve the required characteristics and microstructure, various forging heat treatment methods may be used alone or in combination. In this article, we’ll discuss the different methods and how they are done.
Annealing
Annealing is a rather broad word that refers to heating metal over its critical temperature and cooling it exceptionally slowly and at a pace that produces a refined microstructure. Usually, the rate of cooling during annealing is sluggish. Most commonly, annealing softens metal to enhance its machinability and create a homogeneous microstructure.
Normalising
Normalising is performed in a heat-treating forging to ensure grain size consistency across an alloy metal. During normalisation, the metals are heated to a temperature slightly over their higher critical point and kept for a sufficient amount of time to allow the formation of smaller and more homogeneous metallic grains. This change is known as grain refining, resulting in the development of a more homogeneous metal object with enhanced tensile strength. After the steel has been heated past its critical temperature, it is cooled by air until it reaches room temperature.
Stress Relieving
Stress relieving is a forging process used to eliminate or minimise internal strains in the metal. These stresses may result from various causes, including cold working and non-uniform cooling after forging. Typically, stress relief is achieved by heating a metal below its lower critical temperature and cooling it evenly.
Quenching
Metal is heated over its upper critical temperature and then rapidly cooled during quenching. Several cooling techniques may be used depending on the alloy and other factors, such as concern for maximum hardness against cracking and distortion. Moreover, the quench techniques with the quickest cooling rates include saltwater, polymers, freshwater, oil, and forced air. Since quenching some steels too quickly might result in cracking, a suitable quench medium is essential.
Tempering
Untempered martensitic steel is solid but too brittle for almost all applications. Tempering is used to achieve the desired mix of hardness, strength, and toughness in steels or to reduce the brittleness of completely hardened steels. In forging, quenching and tempering are essential for producing robust pieces.
In addition to reducing the hardness to a given range, tempering helps alleviate tensions induced by quenching. In addition, it is utilised to fulfil mechanical property criteria for specific steels. Tempering is reheating steel at a relatively low temperature over a specified time to achieve the desired final properties of particular steel. The outcome is a component with the optimal mix of hardness, strength, and tenacity for the desired application.
Hardening of Precipitation
Some metals may become more assertive and harder by forming second phase particles scattered throughout the parent matrix. Precipitates are the name for these new phase particles. To the parent matrix, these precipitates must be coherent. These precipitates obstruct dislocation motion, raising the pressures necessary to get through them and ultimately hardening and strengthening the alloy.
Case Hardening
Specific components need surfaces to be harder than their cores. In fact, forged automotive gears are often case-hardened. Surface hardening, which solely hardens the cover or casing, is used for such features. This enhances the component’s resilience to wear and tear.
Advantages Of Heat-Treated Aluminium In Many Industries
The industry for heat-treated aluminium forgings is expanding quickly. The steel industry has forged everything—from gears and engines to wheel spindles for the aerospace, military, and marine sectors.
Heat-treated aluminium forgings provide a solid yet lightweight metal for speed and energy economy, making them perfect for many industrial applications. These qualities are necessary for manufacturers to produce high-quality goods, and heat-treated aluminium makes this process more profitable.
Other advantages of forged aluminium are:
- has a low density and is lightweight
- design adaptability
- substantial thermal conductivity
- good weight-to-strength ratio
- satisfactory finish
- qualities of cryogenics
Forging Heat-Treated Aluminium Into Steel Stacks
When aluminium is forged and heat-treated, it acquires mechanical qualities equivalent to steel forgings. Based on the processing, aluminium may be forged even harder than some types of steel. The most significant benefit is that it is about one-third the weight of steel. This implies that aluminium components may be thicker and tougher without increasing weight.
Steel and aluminium forgings undergo heat treatment for the same purpose. The method alleviates mental tensions in castings, enhances mechanical qualities, and facilitates machining or welding. In addition, heat treatment is relatively uniform and generates virtually constant characteristics throughout the forging. It provides all of these advantages at a lesser price than steel forging.
Conclusion
Forging heat treatment is a process that uses heat to change the properties of stainless steel closed die forging like carbon steel or alloy steel. It is used to change the hardness, softness, or other properties of materials whose crystal structures differ at high and low temperatures. The change depends on how hot the material is heated, how fast it is heated, how long it is heated, how hot it is when it is first cooled, and how quickly it is cooled.
