Stress relieving is a critical heat treatment process designed to reduce and eliminate stresses in materials that arise on finished material after machining or while forming. These stresses, in the material can result in distortions, dimensional instability, or even material failure. For industries relying on precision and performance, stress relieving plays an indispensable role in ensuring the structural integrity and longevity of components.
This article provides a detailed overview of the stress-relieving process, its components, furnace types, and its application in various industrial sectors.
1.Process Briefing
The stress-relieving process involves heating materials to a specific temperature below their critical transformation point and holding them at this temperature for a predetermined period. This allows the material’s internal stresses to redistribute without altering its mechanical properties or causing phase transformations. The material is then cooled at a controlled rate to prevent the reintroduction of stresses.
Key Steps in the Stress-Relieving Process:
- Material Preparation: The component to be treated is cleaned to remove contaminants such as grease, oil, or dirt that could interfere with the process.
- Heating: The material is gradually heated in a stress relieving furnace to a temperature range suitable for its composition (typically 550°C to 700°C for steel). This controlled heating process ensures the material reaches the desired temperature for effective stress relieving and optimal performance.
- Soaking: The material is held at the target temperature long enough to ensure uniform stress relief. The soak time generally depends on the material thickness and is typically calculated as one hour per inch of thickness.
- Cooling: The component is cooled at a controlled rate, usually in still air, to avoid the reintroduction of residual stresses. Stress relieving is often performed on components after machining, welding, forging, or casting to ensure dimensional stability and improve performance.
2.Components Used in Stress Relieving
Stress relief benefit for large and complex welded assemblies, components with many processing steps or cast parts with large cross-sectional differences:
- Gears: Frequently used in automotive and industrial machinery,
- Shafts: For applications that involve rotation and stress, such as in engines or motors, shafts need a stress relieved for longevity and a soft core for flexibility.
- Camshafts and Crankshafts: Critical for internal combustion engines, these parts require enhanced durability to withstand high levels of friction.
- Tools and Dies: Precision tools need to be stress relieved post machining and forming to retain their strength during repeated use.
- Welded frames ,welded assemblies and fabricated parts.
Preferable Industrial Sectors
Stress relieving is a versatile process with applications across a wide array of industries. The following sectors particularly benefit from stress-relieving treatments:
- Automotive Industry: Stress relieving is critical for components such as gears, crankshafts, and engine blocks. It enhances fatigue resistance and ensures precision in high-performance vehicles.
- Aerospace Industry: Aerospace components, including turbine blades, structural frames, and landing gear, require stress-relieving processes to meet stringent safety and performance standards.
- Oil and Gas Industry: Equipment such as pipelines, pressure vessels, and drilling tools undergo stress relieving to withstand extreme operational conditions and prevent premature failures.
- Power Generation: Turbines, boilers, and other high-pressure components in power plants benefit from stress relieving, ensuring durability and efficiency.
- Construction and Heavy Equipment: Structural steel, crane components, and heavy machinery parts are treated to prevent distortion during use and enhance load-bearing capabilities.
- Medical Device Manufacturing: Surgical instruments and implantable devices often undergo stress relieving to maintain precision and biocompatibility.
Furnaces Used For Stress Relieving
Therelek Engineers as Industrial Furnace manufacturers, specialize in furnaces that ensure uniform heat distribution and atmosphere control conditions for Stress Relieving processes. The success and effectiveness of the stress relieving process rely is heavily on the furnaces used to perform this heat treatment. Each furnace is tailored to specific component sizes,output, as per production requirements. Below are some of the key furnace types recommended for stress relieving process.
Types of Furnaces Commonly Used:
1 .Continuous mesh belt OVENS & Continuous mesh belt FURNACES FOR stress relieving
Continuous mesh belt furnaces and continuous mesh belt ovens are designed for mass production, where large volumes of components are heat-treated continuously. It allows for components to pass through multiple heating and cooling zones, ensuring consistent treatment across batches. Depending on the job profile continuous conveyor ovens and continuous conveyor furnaces can be used instead of mesh belt with specially designed conveyors.
Features:
- Multi-zone heating controls ensure precise temperature management across different length of the furnace.
- Components are transported on a mesh belt or conveyor, allowing for continuous processing with consistent heat treatment results.
- Temperature for Stress relieving process is from 400℃ to 800℃.
Advantages:
- Highly energy efficientfor high-volume production environments.
- Ensures uniform stress relieving, particularly for small to medium-sized components.
Applications:
- Bearings, fasteners, small automotive parts, and tools that require stress relieving in high volumes.
- Industries such as automotive manufacturing, consumer goods, and precision engineering benefit greatly from this furnace.
- Standard springs, suspension springs, torsion springs, wire forms, valve springs, leaf springs are require stress relieving in high volumes.
The bogie hearth furnace is specifically designed for very large components that are loaded onto a moving “bogie” for transportation in and out of the furnace. It is ideal for components that are too large or heavy for traditional furnaces. Large welded structures and frames are post weld heat treated in bogie hearth furnaces to relieve stresses.
Features:
- Can be custom-designed to handle components of almost any size or weight.
- The bogie design ensures flexible loading and unloading of large parts, improving operational efficiency.
- High-temperature capability, making it ideal for stress relieving large castings and forged components.
Advantages:
- Can handle oversized parts with ease, such as massive forgings, castings, or welded assemblies.
- Customizable design ensures flexibility in handling a variety of large-scale heat treatment processes.
Applications:
- Large aerospace components, heavy-duty industrial parts, automotive frames and Post welding Heat Treatment.
- Perfect for industries such as heavy machinery, aerospace, and foundries where large, high-strength components are required.
3 Box Type Furnace
The box furnace or chamber furnace is a versatile furnace,which is ideal for batch processing and can accommodate various component sizes. The provide uniform heating and are equipped with advance temperature controls to ensure the uniform stress relieving in the parts.
Features:
- Customized capacity makes it suitable for a variety component for stress relieving processes.
- These furnace play a vital role in stress relieving, which involves heating a material to a specific temperature and then cooling it slowly to improve its ductility and reduce internal stresses.
Choosing the right furnace for the stress relieving process is critical to achieving the desired output production rate. Each furnace type offers tailored to different applications, from various industrial sectors continuous furnaces for mass-produced automotive and fastners components in continuous mesh belt furnaces and roller hearth furnaces for heavier continuous production Therelek engineers helps out in right furnace selection, delivers the robustness and longevity needed for today’s demanding industrial applications.
