What Is Hot Casting?
Hot forging requires the metal to be heated above its recrystallization temperature. This allows for the flow stress and energy required to form the metal to lower, effectively increasing the rate of production (or strain rate). Hot forging aids in making the metal easier to shape as well as less likely to fracture.
Iron, along with its alloys, are almost always hot forged for two main reasons: #1) If work hardening progresses, hard materials (such as steel and iron) will become more difficult to work with, and #2) It is a more economical option to hot forge metals such as steel and then follow with heat treatment processes as metals such as steel can be strengthened through other processes (and not necessarily just cold working processes).
Average temperatures for hot forging includes: Aluminum (Al) Alloys – 360° (680°F) to 520°C (968°F); Copper (Cu) Alloys – 700°C (1 292°F) – 800°C (1 472°F); Steel – up to 1 150°C (2 102°F)
How are Hot Forgings Made?
During hot forging, the temperature reaches above the recrystallization point of the formed metal. As the step of plastically deforming the metal above the recrystallization temperature, these high temperatures are required in order to avoid strain hardening during deformation. This process typically involves heating the metal (above its recrystallization point) and then comminuting it into a mold that can also be heated as needed. Because the metal is hot, it is easy to “move” and enables manufacturers to make more complex shapes than cold forging.
For superalloys, which have low malleability, processes such as isothermal forging (deformation in a controlled atmosphere) are used to avoid oxidation. Isothermal forging, also known as hot forging, is a thermal processing process that keeps a workpiece at its maximum temperature throughout the forming process.
Maintaining this temperature is done by heating the mold – it will be at an elevated or slightly lower temperature of the workpiece. The force applied by the mold forms the workpiece, and because the mold is also at an elevated temperature, the cooling of the workpiece between the mold working interfaces is eliminated. This in turn leads to an improvement in the flow properties of the metal (work piece).
Advantages of Hot Forgings
- Increased ductility
- Complex shapes
- High precision
- Cost benefit
- Enhanced stiffness
- Size: 1 in to 30 in
- Weight: Ounces to more than 100 pounds
|Low Carbon and Low Alloy Steel||Easily processed
Good mechanical properties
Low material cost
|HSLA/Microalloy Steel||Good mechanical properties
Low material cost
Simple thermomechanical treatment
|Aluminum||Good strength-to-weight ratio
|Nickel-Base Superalloy||Oxidation resistance
Excellent corrosion resistance
Secondary Operations and Heat Treatment of Hot Forgings
- Punching, drilling, tapping, bending, milling
- Painting, anodizing, black oxide, powder coating
- Heat treatment
Hot Forging Parts
- American Foundry Society. “Investment Casting FAQs”, “Choosing Between Permanent Mold and Die Casting”, “Sand Molding Processes”
- Wikipedia. “Investment Casting“, “Sand Casting“
- efunda. “Sand Casting“
- FBSFittings, LLC. “Casting Fittings“
- The Investment Casting Institute. “What is Investment Casting?“
- FBSCasting, LLC. “Investment Casting Strainers“
- The Library of Manufacturing. “Investment Casting“
- BMG Titanium “Casting Titanium“
- FDCasting, LLC. “Stainless Steel Casting“
Our Internal Resources for Die Casting, Investment casting, Forging and Sand Casting
- Die Casting(Aluminum Die Casting, Zinc Die Casting)
- Investment Casting
- Hot Forging
- Cold Forging
- Stainless Steel Casting
- Duplex Stainless Steel Casting
- Super Duplex Stainless Steel Casting
- Titanium Casting
- Sand Casting (Aluminum Sand Casting, Ductile Iron Sand Casting, Gray Iron Sand Casting)