Extensive Guide of Heat Treatment in Metal Processing
In general terms, heat treatment processing is a method of cooling and heating metals. At Creatingway, we use certain methods of treatment to get any desired properties from metals. It works for both non-ferrous and ferrous metals especially before being used in manufacturing. Over the years, manufactures have been developing several different methods. This improves the cost efficiency and final outcome of these processes. Notably, cycles and new schedules can now make several grades of metals. Hence, here is a further look into the steps of the heat treatment process and its benefits.
What’re The Steps of Heat Treatment?
The heat treatment process simply involves three key steps i.e. first heating the metal, then holding it at that temperature, and lastly cooling it back. We aim at altering the mechanical properties of the metal with these steps. The science behind it is that the high temperatures change the microstructure of the metal. The microstructure is the determiner of mechanical properties. The metal properties changed include ductility, hardness, electrical resistance, corrosion resistance, brittleness, and toughness.
The Heating Treatment
We perform heating using a predetermined thermal profile. This is because the heating process changes the microstructure of the alloys. Alloys exist in three different states during this step. Either a solid solution, mechanical mixture, or a combination of the two. The solid solution is the homogenous mix of all the components. A mechanical mixture is a heterogeneous mix with two metals still distinguishable in the mix.
The Holding Treatment
At this step, we maintain the metal at the achieved temperature. However, it is the period at which we hold the metal that determines its outcome. For instance, if we require only to harden the surface of a metal part, then it will take a short period. Compare this to metal parts that require uniform hardening requiring a longer holding period. Furthermore, the holding time id also dependent on the part size and material type.
The Cooling Treatment
This is the next step after completing the holding step. We cool the metal in a prescribed way. Structural changes occur due to the rate of cooling. Media used for cooling include water, oil, forced air, or brine. Interestingly, the air absorbs heat slowest while brine does this faster.
There exist several factors that determine the final outcome of the metal. They include the rate of cooling, duration of heating, time of holding the metal, and surrounding conditions. However, these factors are dependent on part size, heat treatment method, and type of metal.
What’re The Methods of Heat Treatment In Metal Processing?
The different heating techniques bring out the desired properties in metals. They include:
- Stress relieving
Aging increases the yield strength of malleable metals such as aluminum. The change in properties occurs due to the uniform dispersion of particles within the microstructure of the metals. Some metal age naturally (at room temperature) while others only artificially. Therefore, it is important to store naturally aging metals at lower temperatures.
Stress-relieving releases stress in metals from previous processes such as rolling, machining, straightening, or forming. It is common for parts such as accumulators, air bottles, and boiler parts. The process involves raising the temperatures of the metal to its lower critical borders, then cooling it slowly. So, this achieves uniform stress relief.
Carburization involves heating the metal in the presence of a material that emits carbon upon decomposition. The surface of the metal absorbs the released carbon. The surface is now harder than the inner core due to the increase in its carbon content.
Normalizing relieves internal stresses created by processes such as quenching, welding, and casting. Normalized steel exhibit increased hardness and strength. This is especially useful for parts requiring support or impact strength.
The annealing process involves heating the metal above its upper critical temperature. However, we then cool it at a slow rate. The process improves toughness, maintainability, and ductility. This makes the metal suitable for forming and cold working.
The tempering process involves lowering brittleness by reducing the hardness of the metal. This makes the metal suitable for use in applications requiring these properties.
Hardening is the most common heat-treating process. We use it to elevate the hardness of any metal. Especially for metal surfaces. Hence, we do this by hearing the workpiece to a specific temperature then cooling quickly in a cooling media. The submerging liquid can be brine, water, or oil. However, we sacrifice the metal’s brittleness for hardness and strength. An alternate form is this method is case hardening. It involves making hard the outer layer of the workpiece yet still maintaining a softcore.
What’re The Benefits of Heat Treatment In Metal Processing?
- Makes the metal soft or hard
- Improve electrical and heat conductivity of the metals
- Relieve stresses from initial cold working processes
- Achieve desirable chemical properties from metals
At Creatingway, we emphasize on the importance of heat treating metals. It only improves the properties of the metal to better suit your application needs. For any inquiries concerning metal manufacturing, kindly contact Creatingway now.
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