During construction, you may have to treat the steel you intend to use. There are several options you can explore. Two of the very popular ones are annealing and tempering. In this article, I will do a comparative analysis; thus, it will be annealing v tempering. In the end, you will perhaps have an in-depth knowledge of the benefits of each.
Before we get started, it might be necessary to understand what heat treatments are. This is a little like progressing from one grade to the other. The previous class provides the building blocks for the next. Let’s go!
Heat treatments refer to all the processes you use to alter the physical nature of steel. However, the process makes sure the shape of the item remains intact.
During heat treatments, you preserve some of the desirable qualities in the material. At the same time, you will be elongating the time it takes for processing. When you complete the cycle, you will have more useful material without an altered state.
Generally, heat treatments take the form of heating and cooling of the material.
Each of these processes has different effects on the materials. For instance, rapid cooling of steel would cause it to harden. However, the opposite reaction will affect another material, say aluminum. In fact, rapid cooling of aluminum results in hardening.
There are various reasons for employing heat treatment. They include improving strength, formability, ductility, elasticity, toughness, and hardness.
Annealing v Tempering
To have a fair understanding of both processes, we will need to examine them individually. Hence, you will then be able to pick out areas of similarities and differences. The first up is annealing.
Annealing is the process of heating steel to a specified temperature. This temperature is typically high. Afterward, the material is then cooled at a controlled rate.
To make it easier, imagine this process to be somewhat like when cooking with an oven. However, instead of taking the cooked food out, you let it cool inside the oven. The activities of heating and cooling are the same as what you do in annealing.
This process is mostly used for steel materials. Metals such as aluminum and brass undergo an entirely different process. This process is known as solution annealing.
The common instrument you can use for annealing is the oven. This is because it is the only space that could be perfect for that purpose. Hot air gets circulated around the materials when they are placed inside the oven. This means that if you intend to engage in this process, you need to find an oven that is big enough to contain the materials.
Stages of Annealing
During the annealing process, you encounter 3 unique stages. They are:
- Recovery Stage
- Recrystallization Stage
- Grain Growth Stage
Let’s consider them sequentially:
1. Recovery Stage
This is the stage where the metal gets heated up. You can use a variety of devices, although, as mentioned, an oven is the most popular. The goal here is to heat the metal to the point where it gets weakened.
2. Recrystallization Stage
You subject the metal to a lot more heating at this stage.
The heating stops at the sweet spot. The sweet spot is the point where you exceed the metal’s crystallization temperature. However, it is important to make sure you do not exceed the melting point.
When recrystallization happens, new grains develop within the material. We will explore this further in the next stage.
3. Grain Growth
This is the final stage of the annealing process. Here, the grains that started developing grow fully. It is the growth of these grains that produces a less hard material.
Benefits of Annealing
You may be wondering, what is the point of annealing metal? It might seem like a thorough waste of time to the bystander. Below, you will find some of the reasons why you ought to anneal your metal.
- Annealing reduces the wear and tear you experience with cutting tools. This reduces the cost you spend replacing tools you use during construction.
- When you anneal metal products, they become softer. This makes it easier to make use of the metal. Overall, this would then affect the production time. You can complete construction and other incidental processes at a faster rate than otherwise.
- You can shape and cut annealed products more quickly than you would otherwise. This makes manufacturing faster and smoother.
- If you are going to work with welded structures, annealing is ideal for that. This includes every form of wiring and sheet metal work.
Tempering involves heating the metal to just below the critical point. Typically, you temper metal after hardening to ensure that the material does not crack due to pressure. However, the metal remains very hard still.
While tempering, it is usually advisable to increase the heat slowly. This is to prevent unintended consequences such as cracking.
There are a couple of factors that impact tempering. The first is the nature of the metal you are tempering. Furthermore, the lower critical temperature of the metal is also very important. This will be explained fully in the next section.
Stages of Tempering
Basically, tempering involves two stages. Unlike annealing, these stages do not have specific designations. However, I will explain each one after the other.
The first stage is where the metal is heated. The amount of heating here is quite high. However, it does not exceed the lower critical temperature. This can be anything between 400 to 1,300 degrees. Each material actually has a lower critical temperature.
The other stage is the temperature maintenance stage. Here, once you achieve the lower critical temperature, you leave the metal at that stage for a length of time.
Benefits of Tempering
Below, you will find some of the benefits of tempering.
- Tempering creates more hardened materials. As a result, tempered steel is more durable than annealed steel.
- The tempering process eliminates impurities in the material. This has unique benefits, especially for welding. When you attempt to weld steel without tempering beforehand, you could totally damage the material. The metal could become warped and distorted.
- Tempering is ideal for materials that are used in high-stress situations. For instance, the steel used in the manufacture of cars is tempered. This is the only reason your car does not veer off the road at any point. Apply this same logic to construction to see how important tempering is.
You should also note that there is a potential downside to tempering. The brittleness that the metal experiences make it less than ideal for many situations. Thus, you have to confirm the process ideal for the product before you temper.
Differences Between Annealing and Tempering
- Annealing’s heating temperature is higher than what you use while tempering.
- You can cool tempered steel quickly in the open air. However, for annealed steel, you have to cool slowly. Furthermore, usually, you have to cool within the space where annealing took place, e.g., the oven.
- Annealing creates softer metal than tempering. These products are useful for certain manufacturing processes.
- Tempering creates metal that is brittle but not to a large extent. Tempered steel is useful for situations where toughness and strength are needed.
That’s all there is to know about annealing v tempering. This article reveals all you need to know about both processes.