America’s industry is built on steel and other metals, and we want our materials to be the strongest possible. Our buildings, cars, factories, and equipment all require the best materials possible to perform at their peak. Metals on their own can be hard and brittle, leaving room for failure and fracture, which can be dangerous in most scenarios. With different treatment processes, we can change the mechanical properties of metal to be maximized for different uses. A metal’s carbon content, alloy mixture, and elements such as chromium all contribute to the best application for that steel type. In this article, we will talk about one of the most-used processes to change metal’s durability and usefulness.
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What Is Annealing?
We strengthen our metal by altering its mechanical properties through processes like annealing. Annealing is a heat treatment process applied to create metal that is more supple and less brittle. Improving the metals’ ductility (ability to deform plastically without fracture) can be done by heating the metal and changing the crystal structure. The heating and cooling process restructures the crystals, creating fewer dislocations between them. The hot glowing metal is heated beyond its recrystallization temperature for a set amount of time, depending on the use.
Annealing may be required throughout the process of hot or cold working on the metal as that will change the material structure. Annealing prepares metal to be formed by shaping, forming, and stamping processes. By creating a more ductile material, we prevent dangerous fractures from occurring in critical places.
Why Is Metal Annealed and When It’s Required
Fabricators use annealing to create parts and items from steel that need a workable material. By this heating process, metal fabricators return parts to a workable state that makes it possible to form what they need. Changing metal to improve ductility and prevent brittle material is important for many other reasons:
● The annealing process helps to remove residual stresses. These stresses create mechanical complications and cracks in the material, so it is best to eliminate these through any means possible.
● Annealing improves the material’s ability to be machined. Brittle material causes the steel to wear out too quickly, so we improve tool wear by reducing the hardness with annealing.
● We improve the ability to form metal with annealing. With more ductile material, we can prevent brittle metal and instead have a material that is easier to bend and press.
Annealing is often required to undo the effects of work hardening during the processes of cold forming, bending, or drawing. If the steel becomes too brittle, it will make forming or shaping impossible without cracking.
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How is Annealing Done?
The annealing process occurs in three different stages as we change the mechanical properties of steel. We can control the annealing temperatures (steel annealing calculator)and heat the steel above its recrystallization point with a furnace. Cooling the metal will return it to a recrystallization state as the atoms reform rids the structure of dislocations.
Here are the three stages of annealing:
1) Recovery – In the recovery stage, steel is placed into a furnace or heated by other processes to raise the material to a temperature that relieves internal stresses.
2) Recrystallization – During recrystallization stages, steel will be heated above its recrystallization point but will be kept at a point below melting. Heating to this point will cause new grains to form in the steel without residual stresses.
3) Grain Growth – The grains that formed during the heating process will develop more as the metal cools. Grain growth can be controlled by having the material cool over set times. After the final step of annealing, other processes to alter mechanical properties can take place.
Which Alloys Can Be Annealed?
Annealing is a common process used on steel and other metals, but can it be used with alloys? The answer is yes. Although alloys may use slightly different temperatures, they can be annealed by using a partial or full process. However, 5000 series alloys are the exception, but they can still be given stabilization treatments at lower temperatures.
Alloys are usually annealed at 300-410℃ with times ranging from half an hour to three hours. These variables will depend on the size of the material and the type of alloy being heated. The cooling process should not exceed 20℃ until the metal cools to below 290℃. After the material cools to below 290℃, the cooling rate will no longer be important.
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Most Common Uses For Annealing
The advantages of annealing are mainly in improving the workability and ductility of metals. The process increases machinability and durability while reducing its hard and brittle properties. This makes annealing a very common process used in a variety of applications like:
● After Welding – Materials that have residual stresses from processes like welding. Annealing is used to combat the stresses by recreating uniform physical properties and structures.
● After Machining – Machining can cause an excess of heat to the material. Annealing is helpful to reform the crystal structures of the materials after machining.
● On Metal Wire – Annealing is often used on metal wire that has been drawn to a smaller size.
● On Work-hardened Materials – Materials like sheet metal and others that have undergone stamping or similar processes will need annealing to increase their ductility and durability.
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Now that you know everything about the annealing process, you can make better decisions on material choices for any project. South Austin Metals can help you fabricate anything metal that you can dream up! We also offer steel sales for all construction needs, including items like I-beams, sheets, edging, pipes, and much more. Since 1971 we have been providing the highest quality metals to the Austin construction industry. Find more information about us and why we are the best company to supply your business.