Heat Treating for Castings
Quality Processing for Castings
Casting is a cost-effective, efficient way to yield near-net-shape metal parts. Most castings, however, require heat treating to give them the characteristics they need to perform in the field.
The microstructure in cast parts is typically more heterogeneous and porous than those we see in other methods such as forging. When heat treating anomalous microstructures as seen in cast parts, we use various methods to limit porosity and distortion while enhancing tensile strength and case depth.
Cast Irons
Cast iron is a common material across agriculture and other applications where parts act as strong structural components and are required to withstand constant back and forth motion. Toughness is typically a primary concern when preparing cast iron parts for market. We use austempering to reliably bring parts up to spec.
Cast Steels
A cast part’s application determines what qualities heat treatment needs to bring out. In some cases, the part requires a hard case with a softer core for toughness, and sometimes, tensile strength and ease of machinability are the desired outcomes. With both case hardening and precipitation hardening capabilities, we can ensure your parts meet your specifications.
Cast Nickel-based Alloys
Processes such as hot isostatic pressing help reduce the porosity of investment castings without risking distortion. Precipitation hardening is also used on cast nickel-based alloys to increase tensile strength and bring parts into spec.
Castings We Process
- Automotive Components
- Engine blocks (cast iron and cast aluminum)
- Brake rotors (cast iron)
- Aerospace Components
- Turbine blades
- Vanes for jet engines
- Firearms Components
- Triggers
- Trigger guards
- Safeties
- Medical Devices
- Surgical implants
- Mining machinery
- Railroad components
Casting Techniques
Investment Casting
Also referred to as “lost wax process” or shell mold casting, investment casting uses a sacrificial ceramic mold made from a wax template. Advantages of investment casting include its ability to yield parts with high dimensional accuracy and geometric accuracy. This technique is often used for small parts with complex geometries or other parts that are difficult or impossible to shape with machining such as turbine engine blades.
Die Casting
Die casting usually features short cycle times where molten metal is subjected to varying degrees of pressure in the die, followed by rapid cooling via internal channels in the tooling. This technique is suitable for high-volume parts that require an excellent surface finish and need to be produced near-net shape. Die castings are common in the automotive market, especially for electric vehicles because they are lightweight. Engine components such as casings, engine blocks, and bracketery are all produced using die casting methods including high-pressure die casting and permanent mold casting. Aging or a combination of solution and aging are the most common heat treatments for die castings.
Sand Casting
Sand casting is a cost-effective manufacturing method used for components such as brake rotors in addition to some aluminum parts. Components made using sand casting are usually treated with solution and aging, ferritic nitrocarburizing, through hardening, and annealing (or stress-relieving).
Permanent Mold Castings
Permanent mold casting is predominantly used in aluminum for parts such as cylinder heads for cars. A more cost-effective casting method when compared to high-pressure die casting, permanent mold casting allows for the use of salt cores which reduces the cost of the tooling required.
Heat Treating Processes for Castings
Hot Isostatic Pressing (HIP)
HIP is well-suited for castings, specifically investment castings, because of its ability to reduce porosity in metal parts. During the HIP process, parts are subjected to pressures up to 30,000 psi, which gives the process the ability to render parts with 100% theoretical density. We can help you maximize the value of your jobs by combining HIP with heat treating in a single cycle, which also helps reduce turnaround times.
Annealing
Annealing enhances the ductility and reduces the hardness of metal parts, making it a commonly used process for castings that undergo further machine operations after heat treatment.
Ferritic Nitrocarburizing
Ferritic nitrocarburizing (FNC) is conducted at relatively low temperatures when compared to other case hardening processes such as carburizing and carbonitriding. Conducted while steel is still in the ferritic phase, FNC is typically performed between 950 degrees Fahrenheit and 1100 degrees Fahrenheit. The lower temperature of the process minimizes distortion resulting from thermal processing while still yielding good case hardness and corrosion resistance, making this process an ideal choice for near-net-shape parts.
Precipitation Hardening
This process is often done for aerospace castings that require higher tensile strength than can be achieved by case hardening. Also known as aging, we often combine precipitation hardening with solution treatment to yield parts that can withstand high heat and tensile stress during service.
Quenching
The quench media and the temperature of the media determine the outcomes of the quenching process for castings. As a rule, the more severe the quench, the higher the hardness in the resulting part—but with water or caustic soda quenching, the risk of part distortion and quench cracking also rises. Our team can help you determine which quench media is right for your application to achieve the ideal results for your parts.
Tempering
While annealing reduces the hardness of metal parts, tempering is carried out to increase their toughness by holding parts at their critical temperature for specified periods of time.
Brazing
For bright, clean parts and flawless metal joining, we offer both hydrogen brazing and vacuum furnace brazing. When tolerances matter, brazing produces superior results to welding.
Hot Isostatic Pressing (HIP)
HIP is well-suited for castings, specifically investment castings, because of its ability to reduce porosity in metal parts. During the HIP process, parts are subjected to pressures up to 30,000 psi, which gives the process the ability to render parts with 100% theoretical density. We can help you maximize the value of your jobs by combining HIP with heat treating in a single cycle, which also helps reduce turnaround times.
Annealing
Annealing enhances the ductility and reduces the hardness of metal parts, making it a commonly used process for castings that undergo further machine operations after heat treatment.
Ferritic Nitrocarburizing
Ferritic nitrocarburizing (FNC) is conducted at relatively low temperatures when compared to other case hardening processes such as carburizing and carbonitriding. Conducted while steel is still in the ferritic phase, FNC is typically performed between 950 degrees Fahrenheit and 1100 degrees Fahrenheit. The lower temperature of the process minimizes distortion resulting from thermal processing while still yielding good case hardness and corrosion resistance, making this process an ideal choice for near-net-shape parts.
Precipitation Hardening
This process is often done for aerospace castings that require higher tensile strength than can be achieved by case hardening. Also known as aging, we often combine precipitation hardening with solution treatment to yield parts that can withstand high heat and tensile stress during service.
Quenching
The quench media and the temperature of the media determine the outcomes of the quenching process for castings. As a rule, the more severe the quench, the higher the hardness in the resulting part—but with water or caustic soda quenching, the risk of part distortion and quench cracking also rises. Our team can help you determine which quench media is right for your application to achieve the ideal results for your parts.
Tempering
While annealing reduces the hardness of metal parts, tempering is carried out to increase their toughness by holding parts at their critical temperature for specified periods of time.
Brazing
For bright, clean parts and flawless metal joining, we offer both hydrogen brazing and vacuum furnace brazing. When tolerances matter, brazing produces superior results to welding.
Materials Used in Casting
- Stainless Steel
- Carbon Steel
- Cast Iron
- Copper-Based Alloy
- Nickel-Based Alloy
- Aluminum Alloy
Metallurgy Support for Castings
Are you experiencing quench cracking, distortion, or out-of-spec hardness results in your parts? We love to solve problems. Bring your challenges to our metallurgy team and let’s get your production back on track.
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