In-House Aluminum Heat Treatment: Exploring T6 and Other Processes

Have you ever worried that your metal fabrications aren’t strong enough for your product? Have you had equipment fail due to untreated parts? We know the importance of having alloys that hold up to daily stresses. Aluminum heat treatment ensures that our casts have the highest degree of strength and durability. The experts at Boose Aluminum Foundry Co., Inc. have the knowledge and ability to perform in-house heat treatment after casting your goods, ensuring unmatched strength and durability.

You want to work with a foundry that will produce metal goods that can exceed your needs and specifications. Our foundry has been at work for more than four generations, providing excellent service and quality productions. After reading this post, you will have a better understanding of the in-house aluminum heat treatments that can be done for your aluminum cast products.

Why Do We Heat Treat Aluminum?

You might think that you can get away with untreated aluminum, but that would be a mistake. Untreated aluminum parts can fail, distort, or warp under stress. Aluminum is a relatively soft and malleable metal when compared to materials such as steel. However, its lightness and corrosion resistance make it a very desirable material across dozens of industries.

Heat treatments come in a variety of forms, but all involve some mixture of heating and stressing metal pieces to promote higher strength and proper form. Picture the classic image of a blacksmith sticking a sword or horseshoe into a forge and then quenching the piece in water. We have known the power of heat-treating metals for centuries. Today, the T system of classification separates and defines many different methods and processes of heat treatment. Each method has benefits and drawbacks to the resulting product.

Heat Treating Options at a Glance

For Improved Strength and Hardness – T6 Heat Treatment

T6 heat treatment is one of the most performed aluminum heat treatments. This method begins in a high-heat oven. Most heat treatments begin with “solution heat treatment,” which melts any alloy materials that have condensed after casting. This solid solution lets the alloys re-distribute through the casting, providing strength and support.

After being heated to just below the melting point of aluminum (1,221°F/660.3°C), the castings are quickly quenched and cooled. Quenching the piece will solidify the microstructure that forms in the solid solution phase. Quenching may cause mild distortion to the casting if the cooling is uneven, but the rapid cooling also results in a much stronger casting.

After quenching, the castings are artificially aged in an aluminum heat treat oven. Sometimes, this is also referred to as ‘precipitation hardening.’ This term means they are baked at nearly 310°F/154°C, well below the melting point of aluminum. This aging process allows the alloying elements to form chemical bonds within the casting, re-enforcing and strengthening the piece. Aluminum age hardening will happen naturally over time, but this process is sped up by baking the product.

Straightening and quality control measures are undertaken after the solution heat treatment process to ensure that the shape and form of the casting will meet all specifications.

For Welded Pieces – T4 Heat Treatment

For some materials, secondary baking is not necessary. In the T4 heat treatment process, the casting is heated to the solid solution stage. After it has reached a suitable temperature, the cast is then quenched and air-cooled. T4 heat treating provides natural aging rather than artificial aging via baking.

Natural aging takes time, but the process is preferable when the aluminum casting undergoes welding later. The heat and stress of welding can cause over-aging at the weld, making the weld more brittle and risking failure.

Over-aging can be undone by treating the entire piece again with heat, but this is costly and easily avoided.

For Precision Parts – T5 and T51 Heat Treatment

Rather than simply letting the casting air cool, they are artificially aged in an aluminum heat treat oven. This doesn’t involve rapid quenching, which is what causes warping and distortion that other heat-treatment options can risk. This is most used in aluminum casts that require a high degree of precision, such as medical instruments, electronics, and robotics parts.

The difference between T5 and T51 heat treatment is the temperature and duration of the aging. The second number in the T system indicates variations and secondary treatments. Many alloy materials are used during the aluminum casting process, and these materials sometimes precipitate at higher temperatures or take more time to form chemical bonds. Age-hardening aluminum certain alloys can require precise temperatures and times. For more information, call and learn directly from an expert what our heat treatment options can do for you.

For High-Stress and Heat – T7 and T71 Heat Treatment

T7 and T71 are very similar processes to T6. The castings are solution heat treated and then quenched to reduce the temperature. The primary difference between these three heat treatments is the temperature at which they are aged. While T6 heat treating involves baking the cast at around 310°F (154°C), T7 castings are aged at a higher temperature of 440˚F (227˚C). T71 requires an even higher 475˚F (204˚C). This high-heat baking causes alloying materials to precipitate fully. This results in the maximum hardness but also reduces tensile strength and yield strength.

This high-temperature baking is most often used for aluminum cast engine parts, valves, and other pieces that will undergo a great deal of stress and pressure. The over-aging process can result in a casting that is much more stable for long-term use. This creates a cast that has better mechanical properties, making it easier to finish. However, the tensile and yield strength is often reduced.

There are many other ways to heat-treat and form your metal goods, but those not discussed here involve cold-working the metal.

Trust the Experts at Boose Aluminum Co., Inc. for Your Aluminum Heat Treatment Needs

Heat treatment is a critical part of aluminum casting. If you find yourself searching for ‘aluminum heat treating near me,’ then look no further! You need aluminum pieces that won’t fail. Your products need to stand up against stress and corrosion in their day-to-day use.

Every treatment provides unique benefits and drawbacks to the product. We can provide a complete heat treatment service that will strengthen your castings to suit their usage. Call us today, and we can start the conversation about what we can cast for you and how to ensure you get the proper aluminum alloy heat treatment process for your products.

Resources:

• https://www.matweb.com/reference/aluminumtemper.aspx