When it comes to aluminum heat treating, the question isn’t just about which types of aluminum can be heat treated–it’s about how to do it well. The process requires precision, expertise, and specialized equipment to prevent issues like warpage and ensure consistent results.
Jones Metal specializes in heat treating specific types of aluminum properly to ensure optimal strength and prevent warpage. Here, we review what types of aluminum are heat treatable and how to do it correctly.
Heat Treatable vs. Non-Heat Treatable Aluminum
Heat treatable aluminum alloys include:
- 6061
- 7075
- 2024
These materials can be hardened through the heat treating process, allowing manufacturers to use thinner gauge material while achieving the desired strength properties. This is particularly valuable in aerospace and defense applications where weight savings are crucial.
For example, you might be able to form a part using 30-thousandths thick 6061 aluminum and heat treat it to T6 condition to achieve the desired strength, whereas you’d need material nearly three times thicker (around 100-thousandths) in a non-heat treatable alloy to achieve comparable strength.
Non-heat treatable alloys include:
- 3002
- 3003
- 1100-O
- 5052
These alloys maintain their properties regardless of heat treatment. While they can be formed easily (such as through hydroforming), they typically require greater thickness to achieve the same strength as heat-treated alloys. They come from the mill at a specific hardness, and that’s what manufacturers have to work with.
Understanding Material Characteristics
Different aluminum alloys have distinct properties. For instance, 2024 aluminum is generally considered the hardest of the common heat-treatable alloys, making it more difficult to form than 7075 or 6061. The 7075 alloy falls somewhere between 2024 and 6061 in terms of formability, while 6061 in the O condition is typically the easiest to form among these three popular alloys.
The Complete Heat Treating Process
Starting Condition
Most heat treating begins with material in the O condition–the softest state available. This allows for initial forming operations before hardening. However, if O condition material isn’t available, it’s possible to start with harder material and heat treat it back to a more formable state.
Solution Heat Treatment
The process begins by heating the material to 985 degrees Fahrenheit in a specialized furnace. The material is held at this temperature for approximately one hour. This stage is critical and requires precise temperature control and timing.
Quenching Process
After heating, the material undergoes quenching–a rapid cooling process that’s more complex than it might appear:
- The bottom of the furnace opens, and the material basket drops into a quench tank.
- Depending on the alloy, the tank contains either a water-glycol solution or hot water (some alloys, like 2024, specifically require hot water quenching).
- Complete immersion must occur within seven seconds.
- The quenchant is carefully circulated to prevent air bubbles, which can cause uneven cooling and warpage.
- For optimal results, the glycol solution is maintained at a 15% concentration.
The W Condition
After quenching, the material enters what’s known as the W condition–a temporary state that offers unique advantages:
- Lasts only four hours in open air.
- Material remains formable during this period.
- Can be extended by freezing the material.
- Portable freezers allow for maintaining the W condition right up until forming operations.
Progression to T4
If left in open air for four hours, the material naturally progresses to T4 condition, which is a medium-hardness state. While some forming is still possible in T4, it’s significantly more difficult than in the W condition. If additional forming is needed after reaching T4, the material typically needs to be solution heat treated again.
Achieving T6 Condition
The final hardening to T6 condition occurs through aging:
- Material is placed in an oven (different from the initial furnace).
- Temperature range is 300-500 degrees Fahrenheit.
- Process takes 12-24 hours.
- Results in the hardest condition for most alloys.
Common Challenges and Solutions When Heat Treating Aluminum
Preventing Warpage
Warpage control is critical in heat treating. Several techniques help minimize this issue, including proper fixturing during quenching, controlled quenchant circulation, use of glycol solutions to reduce thermal shock, ability to perform additional forming operations while in W condition, and straightening capabilities when needed.
The T3 Condition Challenge
One common misconception about heat treating aluminum involves T3 condition aluminum. This condition can only be achieved during mill processing and cannot be replicated through post-manufacturing heat treatment. T3 condition is similar to T4, which is often an acceptable alternative.
What Happens When Aluminum Isn’t Heat Treated Properly?
One of the most common and frustrating issues with improper heat treating is a phenomenon called “potato chipping.” Just as the name suggests, your part can emerge from the furnace warped and wavy, similar to the shape of a potato chip. When this happens, the part becomes unusable, meaning all the money and work invested in the material and forming process is lost.
This type of warpage often occurs due to improper quenching techniques. If air bubbles get trapped under parts during the quenching process, it can cause uneven cooling–the top of the part will cool while the bottom remains hot, resulting in distortion. That’s why proper fixturing and quenching techniques are crucial to prevent air bubble formation during the process.
When working with defense and aerospace components, there’s no room for error in the heat treating process. Choosing a heat treating team that follows proper procedures and maintains strict quality control standards is essential to avoid costly scrapped parts and project delays.
Contact Jones Metal Today
Successful aluminum heat treating requires more than just the ability to heat and cool metal. It demands precise temperature control, careful timing, proper equipment maintenance, and deep understanding of material properties. When done correctly, heat treating allows manufacturers to achieve optimal material properties while minimizing waste and rework.
When you need dependable aluminum heat treating solutions from certified professionals, contact Jones Metal to discuss your project. Whether you need parts for aerospace, defense, healthcare, or other applications, we have the experience and equipment necessary to complete your aluminum heat treatin properly.
