What is Aging in CNC Machining?

In CNC machining, the term "aging" often appears. But what exactly does "aging" in CNC machining refer to?

In the field of CNC machining, to eliminate or minimize changes in the dimensions and shapes of precision gauges and molds that occur during long-term use, a process called "aging" is employed. This involves reheating the part to 100-150°C after a low-temperature tempering step, holding it at this temperature for 5-20 hours, and then performing finishing operations. This process is used to stabilize the quality of precision components. More importantly, under low-temperature or dynamic load processing conditions, CNC aging treatment is performed on the original steel material to stabilize the steel's structure and dimensions and to eliminate residual stress.

Aging can generally be divided into several methods: natural aging, artificial aging, thermal aging, and vibrational aging.

Natural Aging refers to the practice of placing castings outdoors for a long period, at least six months, to thoroughly eliminate residual stresses.

Artificial Aging involves heating castings to 550°C~650°C for stress relief through annealing. Compared to natural aging, artificial aging not only saves time but also more effectively eliminates stresses.

During processes like casting, welding, forging, and mechanical cutting, residual stresses can develop inside the part due to thermal expansion and contraction or mechanical forces. This leads to an unstable state that reduces dimensional stability and mechanical properties, potentially causing deformation and failure during later use. To eliminate these residual stresses, traditional methods include natural aging and thermal aging.

Natural Aging is the process of placing the part outdoors for a long time to use the varying external temperatures and time effects to completely release residual stresses.

In addition to these two common aging methods, there are also Thermal Aging and Vibrational Aging.

Thermal Aging (TSR) is a widely used traditional mechanical processing method. It involves heating the metal structure to a certain temperature in a furnace, maintaining the temperature, and then controlling the cooling process to eliminate residual stresses, ensuring processing precision and preventing crack formation. Thermal aging is a heat treatment method used for various alloy materials. It promotes the diffusion of atoms and ions within the solid at high temperatures, followed by a period of holding at room temperature to achieve a desired microstructure state. This process effectively changes the material's properties to improve hardness, strength, toughness, and corrosion resistance.

The Thermal Aging Process includes: heating - holding - water quenching or air cooling - finished product.

- Heating: The alloy material is heated to a high temperature in the furnace. Heating time and temperature vary based on the type and shape of the alloy.

- Holding: At high temperatures, the material is kept for a certain period to allow enough time for atoms and ions to diffuse and react. Holding time depends on factors such as material type, shape, and size.

- Water Quenching or Air Cooling: After processing, the alloy material must rapidly release heat, achieved through water quenching or air cooling.

- Finished Product: After heating, holding, and cooling, the alloy material reaches a specific microstructural state suitable for further processing or product manufacturing.

Vibrational Aging (VSR) is a process that can completely replace both thermal aging and natural aging. It uses vibrations to eliminate residual stresses, achieving results comparable to TSR methods and exceeding them in many performance indicators.

Additionally, there is a method called Ultrasonic Aging. Ultrasonic aging is used for eliminating residual stresses and strengthening components in mechanical repair processes. It is a promising technique in manufacturing and maintenance with features such as being the most thorough method for residual stress removal, having a simple process, stable and reliable results, and being environmentally friendly, energy-saving, and non-polluting. It is applicable on-site, during welding, and for various materials and component sizes.

In summary, depending on the actual needs of clients, different aging methods can be selected.