Choosing Forging Materials
Forged components are known for their superior strength, impact resistance, and toughness. Part of this is due to the forging process itself, which involves heating the metal to a predetermined temperature before deforming it with a press, hammer, or ring roller. The key difference between forging and other metal fabrication processes like casting is controlled deformation. The controlled deformation during forging results in an intentional grain flow, or directional alignment.
In addition to the forging process itself, the materials that are used during forging also influence the final component’s mechanical properties.
Which Materials Can Be Forged?
It would be impossible to cover every single material that can be forged, as almost all types of metals can be forged. In this article, we’ll focus on four common materials we work with at Trenton Forging: carbon steel, microalloyed steel, alloy steels, and stainless steel.
Carbon steel is essentially steel with various amounts of carbon integrated into it. There are three primary categories of carbon steel: low-carbon steel, medium-carbon, and high-carbon.
Low-carbon steel contains 0.5% to 0.25% carbon. Medium-carbon steel contains 0.29% to 0.54% carbon, and high-carbon steels have carbon levels between 0.55% and 0.95%. The percentage of carbon in the steel will affect the component’s strength and hardness. So, applications that require high strength and hardness will need high-carbon steel.
In general, carbon steel doesn’t require high amounts of other metals or alloys to attain its superior mechanical properties. Its own existing grain structure makes it one of the best forging materials to use for high-load applications that require components with heavy stress and impact resistance. Carbon steel is also naturally resistant to environmental damage, so it is also well-suited for applications that require corrosion-resistant components.
Sometimes referred to as high-strength, low-alloy steels (HSLA), microalloyed steels contain trace amounts (0.05% or less) of alloying elements. The composition of microalloyed steels varies based on the steel’s grade and customer requirements. However, all micro alloys contain some small percentages of carbon, manganese, phosphorus, sulfur, silicon, and other alloying elements.
Microalloyed steel usually has similar mechanical properties to many carbon and other low-alloy steels. However, when compared to carbon steel and other low-alloy steels, microalloyed steel may be the preferred material choice for applications that require components with better strength-to-weight ratios.
The primary benefit of forging with microalloyed steel is that the component will have high strength and hardness without any post-treatment methods.
The type of HSLA used during the forging process will depend on various application requirements, including thickness reduction ratio, strength, toughness, etc.
Next, alloy steel refers to any type of steel that conta
ins carbon and is alloyed (or mixed) with other elements, including chromium, silicon, nickel, and vanadium. Alloy steels can be typically split into two categories: low-alloy and high-alloy, but low-alloy steels are primarily used in forging.
These two categories can be further split into several grades. These grades are defined by the AISI/SAE system and based on the composition of the alloy steel. The types of alloying elements contained in the steel define its mechanical properties, which are then further enhanced by the forging process. For example, nickel-silicon improves strength and ductility while nickel on its own improves corrosion/oxidation resistance and creep-rupture strength.
Lastly, stainless steel is another common type of material used in forging.
Technically, there are three core groups of steel: alloy steels, micro alloy steels, and carbon steels. However, the mechanical properties of stainless steel are so unique that they’re often considered a separate group entirely.
Stainless steel is typically categorized by its microstructure and is therefore considered either ferritic, martensitic, austenitic, or duplex (combination of austenitic and ferritic). Additionally, just like any steel, stainless steel is categorized into many grades based on chemical composition. Many stainless steel alloys are considered austenitic, including series 200 and 300.
Regardless of its microstructure and defined grade, stainless steel as a whole is known for its exceptional fatigue strength and corrosion resistance. The forging process itself will enhance these mechanical properties. It’s also important to note that any alloying elements added to stainless steel, including nickel and chromium, may affect certain properties, including tensile strength, hardness, and yield strength. Any post-treatments, including quenching and annealing, may also affect these mechanical properties.
Generally, stainless steel forgings are most often used in high-temperature, high-stress applications and in corrosive environments.
Selecting the Right Forging Materials
Deciding which material best suits your needs largely depends on your application and the environment your component will be in. You must also understand how well your chosen material will perform during the forging process is essential. Lastly, don’t limit your selection only to a base metal’s mechanical properties; forging will have an effect on these properties, as well as the material’s microstructure.
The best way to select the right material is to consult with a professional engineer or metallurgist. They have the expertise and education required to help you select the right alloy based on your application needs.
Contact Us at Trenton Forging
Get in touch with our team at Trenton Forging for your forging needs.
Founded in 1967, we’re an ISO 9001-certified American forging company specializing in impression die forging. Our experienced engineers and technicians can create custom asymmetrical and symmetrical forgings from stainless steel, carbon steel, alloy steels, and microalloyed steel. Our additional capabilities include 3D printing, 3D laser scanning, die welding, machining, and reverse engineering.
If you have questions about the forging process, or would like to request a project consultation, please fill out our online form today.