The Benefits of Vertical Heat Treatment for Aerospace Requirements

Achieving the precise material properties imposed by the aerospace industry requires advanced manufacturing processes, and the heat treating process is one of the most critical steps. For long, slender, or complex-shaped components where minimizing distortion is essential, vertical heat treatment has emerged as a superior solution. 

The specific heat treating process (hardening and tempering for alloy steels; solution treating and age hardening for Titanium and Inconel alloys) varies depending on the alloy. However, by leveraging gravity to its advantage, the vertical heat treating method provides more uniform heating and quenching, ensuring parts meet exacting standards with greater consistency and reliability. 

In this blog, we will explore the specific benefits of vertical heat treatment and how it directly addresses the unique challenges of aerospace manufacturing.

Why Choose Vertical Heat Treatment?

The decision to use a vertical furnace is primarily driven by the part's geometry and the need to maintain straightness, minimize distortion, and quench uniformly. You would choose a vertical orientation when your component is:

• Long and slender (e.g., shafts, rods, landing gear).
• Large in diameter with a thin wall (e.g., rings, cylinders, cases).
• Prone to sagging or warping under its weight when heated horizontally.

By hanging the part vertically, gravity works to your advantage by ensuring the part remains straight and true throughout the thermal cycle.

Aerospace Specifications and Stringent Requirements

Aerospace requirements and specifications are among the most rigorous in any industry. These form a comprehensive framework that dictates every aspect of a part's lifecycle, from raw material to final installation. 

These standards, often influenced by organizations such as The Boeing Company and Raytheon, and detailed in specifications like AMS (Aerospace Material Specifications), are not merely guidelines but strict, non-negotiable mandates. Companies that offer heat treatment for this industry are accredited by NADCAP, and they strive to maintain it.

Specifications, alongside customer-specific drawings and requirements, define the required mechanical properties, such as tensile strength, fatigue resistance, and fracture toughness, ensuring a component can withstand the extreme temperatures, pressures, and stresses of flight.

Importance of Heat Treating for Aerospace

In most aerospace applications, companies turn to heat treating to achieve greater hardness, improve ductility, enhance fatigue strength, or overall better material performance. 

By adding the vertical process to heat treating, these aerospace companies can ensure that their parts and products meet all of the various specifications and stringent requirements. The safety of aerospace vehicles is dependent on heat treating the metal alloys to make them stronger and more adept at handling the stress of their environment.

The Benefits of Choosing Vertical Heat Treatment

By aligning a component with the force of gravity instead of fighting against it, vertical heat treatment provides unique advantages that directly translate into higher quality parts and greater reliability. Let's explore the specific benefits that make this process essential for meeting the stringent demands of industries like aerospace.

Minimized Distortion and Sagging

A primary advantage of vertical heat treatment lies in its ability to prevent distortion. Horizontally heat treating long, slender, or large-diameter, thin-walled components, such as shafts, landing gear parts, and rocket cases, can lead to sagging or warping due to their weight at high temperatures.

For aerospace components specifically, this method reduces the need for costly and complex post-treatment straightening and machining, preserving the part's intended design and dimensional accuracy.

Uniform Temperature and Microstructure

Advanced vertical furnaces use sophisticated airflow or atmosphere management systems and strategically placed heating elements to ensure the entire length of the component is uniformly heated and cooled. This leads to a consistent and homogenous grain structure throughout the part.

In aerospace applications, this uniformity guarantees that the mechanical properties—such as hardness, toughness, and tensile strength—are consistent across the entire component, which is crucial for predictable performance and reliability under extreme stress.

Consistent and Uniform Quenching

Quenching (rapid cooling) is a critical step that locks in the desired material properties. A uniform quench is essential to prevent internal stresses and distortion. By racking or fixturing the part in a vertical position, the quenching medium can flow evenly over the entire surface. This avoids uneven cooling like a horizontally racked part may experience.

A uniform quench results in predictable, consistent hardness and strength while minimizing the risk of quench-induced cracking or distortion. This helps ensure the part meets strict aerospace specifications like AMS 2759, AMS 2774, AMS-H-81200, or OEM specifications like BPS4212, BAC 5613, PWA 11, and many others.

Ideal for Specific Part Geometries

Many aerospace components are not simple blocks of metal. Vertical heat treating is uniquely suited for parts that are:

• Long and Slender: Such as drive shafts, actuators, and structural rods.
• Large and Cylindrical: Like rocket motor cases or large rings.
• Complex or Asymmetrical: Where horizontal support could create stress points.

By accommodating these shapes naturally, the vertical process avoids the need for complex and costly fixturing that can interfere with uniform heating and cooling.

The Rex Heat Treat Difference

When it comes to vertical heat treating for aerospace alloys, Rex Heat Treat has been in the business for over 65 years. Because we design and build our vertical furnaces, we have the flexibility and adaptability that allows us to adjust our equipment, tooling, and processes to keep up with changing standards and industry needs.

Our vertical heat treatment capabilities enable efficient and uniform heat treatment of large and complex components up to 20 ft, ensuring consistent results across all surfaces and dimensions for large parts. Customers appreciate our process for its precision and quality of output. 

Contact us today if you are interested in our vertical heat treating process and want to learn more.