Heat treatment is one of the most common process used by CNC machining manufacturer. It can change the material properties of your metal. This means that the metal’s strength and toughness are increased to make it more resistant to extreme conditions. Certain heat treatment processes, like annealing, can decrease the metal’s hardness.
Let’s look at different heat treatment methods.
Hardening
The process of hardening is used to make the metal more durable. Higher hardness indicates that the metal is less likely to be damaged or rust when impacted. The metal’s tensile strength, or the point at which it fails to break, is also increased by heat treatment. A material with higher strength is more suitable for specific applications.
The workpiece must be heated to a temperature higher than the metal’s critical temperature. After that, the metal will be chilled in water, oil, or brine. The specific alloy of the metal determines the quenching liquid. Each quenching fluid has a different cooling rate, so choose the one that will cool your metal the fastest.
Case Hardening
Case hardening, a type that does not affect the material’s outer surface, is a form of hardening. This is usually done after machining to create a durable outer layer. You can adjust the process parameters to alter the depth of hardening.
Precipitation Hardening
Precipitation hardening can be used to treat specific metals with certain alloying elements. These elements include titanium, aluminum, phosphorus, and copper. These elements can precipitate or form particles in the metal if the material is heated for a long time. This alters the grain structure and increases the material’s strength.
Annealing
Annealing, used to soften metals, relieve stress, and increase flexibility, has been mentioned. This makes the metal much easier for the machine.
An anneal process involves slowly heating a metal to a temperature above the material’s critical temperature. The metal is then kept at this temperature for a long time before being cooled down. Slow cooling is achieved by placing the metal in an insulation material or keeping it in a furnace until the metal cool down.
Relieving Stress for Large Plate Machining
The material is heated to a specific temperature and then cooled slowly, stress relieving is very similar to annealing. Stress relieving is different. The temperature is much lower than the critical temperature. The material is then air-cooled.
The process reduces stress from cold work or shearing but does not alter the metal’s physical properties. Although the physical properties of the metal don’t change significantly, it is important to relieve this stress so that there are no dimensional changes or warping during further machining or when the part is used.
Tempering
Tempering a metal involves heating it to a temperature lower than its critical temperature and cooling it in the air. Although this is similar to stress relieving, the final temperature isn’t as high. Tempering improves the toughness and retains most of the hardness added to the material through hardening.
When to use heat treatment
After CNC machining, heat treatment should be considered. You might also consider pre-heating material. You don’t need to choose one over another. You can influence the material properties, the machining process, and the tolerances of your part by how you heat treat and machine it.
Heat treatment can affect your machining. Harder materials are more difficult to machine and wear down tools more quicker, increasing costs. You can remove the hardened layer depending on how deep the heat treatment was applied. This will negate the purpose of using hardened steel in the first place. The heat generated during machining may increase the hardness. Some materials, such as stainless steel, are more susceptible to being work-hardened during machining. Extra care is required to avoid this.
Pre-heat treatment metals have their advantages. Pre-heat-treated metals can be more difficult to source, which allows for tighter tolerances. Heat-treating can be a time-consuming process if it is not done after the part has been machined.
On the other hand, heat treating after machining gives you greater control of the process. There are many types of heat treatment, so you can choose which one you prefer to achieve the desired material properties — the heat treatment effects after machining are uniform across your part. Pre-heat-treated materials may only have affected the material to certain depths. Therefore, machining may be necessary to remove hardened material from some areas.
