Heat treatment enables manufacturers to modify the physical properties of metals in important ways. For example, case hardening and induction hardening both transform metal surfaces, causing them to harden.
Yet some heat treating processes soften certain metals to reduce brittleness and enhance ductility. Annealing changes the properties of many metallic constituents in this way, including silver and copper. It allows industrial parts manufacturers to work with metals more easily. Many manufacturers use a specialized form of annealing, normalizing, to enhance the ductility of steel and other ferrous metals comparatively inexpensively.
Annealing offers a process for softening and toughening metals, enhancing ductility and reducing brittleness. Generally, a manufacturer first re-heats metal to a designated temperature above the point of crystallization for a specified period of time and then cools it.
Manufacturers have devised several different specialized annealing processes for working with different metals and metal alloys. These take place in some fabrication environments. The processes include normalizing, sub-critical annealing, process annealing, and stress relief annealing.
The Normalizing Process
Industrial parts makers frequently perform normalizing in order to soften steels and ferrous metals while also further refining the size of the grains to obtain a tougher, more ductile consistency. This process proves far more cost-effective than some other forms of annealing. It has attained fairly widespread commercial use today.
Typically, normalizing occurs before finishing and after casting, forging or cold-rolling. Steels and other ferrous metals benefit from this process. They might otherwise remain brittle and prone to fracturing after hardening.
During normalizing, a manufacturer re-heats the metal to a temperature slightly above the critical re-crystallization point. This temperature varies depending upon the alloys involved. However, it generally occurs between 810 degrees Centigrade and 930 degrees Centigrade.
Sometimes referred to as the "soaking temperature", this point also may vary in some cases based upon the thickness of the metal work piece. Manufacturers don't want to cause the entire work piece to liquefy since this result would result in dimensional distortions. After re-heating and "soaking", the manufacturer removes the metal from the heat source and allows it to cool gradually at ambient room temperatures. Cooling permits molten metals to recrystallize again.
This process helps refine the grains of the metal at a microscopic level. Normalizing permits the production of more finely grained steels and ferrous metals with fewer air bubbles and thick-grained inclusions than castings. The reheating process allows entrapped gases to escape and enables the metal to form finer grains during re-cooling.
As a result, normalized steels and ferrous alloys soften and grow more ductile. Yet these metals retain greater strength and hardness than materials which undergo some other annealing processes. Normalizing has become widespread today in many metal parts fabrication environments.
Materials And Applications
Today, metal parts manufacturers frequently employ this process to help maintain strong, workable steel components.
Normalizing requires the capability to re-heat steels and other ferrous metal alloys to very high temperatures. However, most manufacturing facilities which perform casting frequently can perform normalizing without investing in extensive additional tools or materials. Perhaps for this reason, normalizing constitutes one of the most cost-effective post-casting or forging processes.
In many situations, manufacturers place parts outdoors during the cooling stage. In some cases, normalizing represents simply one step in more complex post-casting finishing processes. Steels cooled at ambient temperatures eventually may return to the production floor for further processing or machining.
Numerous applications exist for utilizing normalized steel and ferrous metal industrial parts. Their added ductility makes these products more attractive in many markets. Normalized components display greater resistance to brittleness after hardening, for instance, making them desirable in numerous settings compared to non-normalized steel parts.
Some popular applications include metal bars used in building construction and fence posts. Additionally, manufacturers today usually normalize heavy steel forgings, such as the axles and wheels of heavy machinery equipment and railroad cars.
Key Advantages of Normalizing
Normalizing steels and ferrous metals after casting, forging or cold rolling offers a number of key advantages. Just consider some of the most important reasons to conduct normalizing:
- This process occurs comparatively cost-effectively. Unlike some other softening processes, such as full annealing, a production facility can re-cool metals fairly easily during normalizing. They do not need to maintain a specialized bath or keep the furnace operating for a protracted period of time during the cooling phase. This aspect contributes to the low-cost of normalizing compared with some technologies.
- Normalizing enables manufacturers to soften steels and ferrous alloys effectively, creating more ductile, easily manipulated work pieces. The softening process allows the metal to meet specifications for some tools and industrial components better as a result.
- Normalization softens metals without sacrificing the benefits of previous hardening processes. Case hardening with carburization or nitriding may contribute to the creation of harder surfaces which display scratch and abrasion-resistance, but also suffer from increased brittleness. By normalizing steel parts, a manufacturer can reduce the effects of brittleness (which sometimes cause premature fracturing).
- Normalizing enables manufacturers to refine the grain structure of steels and ferrous metals after casting. It may help disperse pockets of gases which form unwanted inclusions near the surface of cast parts, for instance. While normalizing won't achieve uniform internal refinement, it does offer a fairly cost-effective means for accomplishing the removal of air pockets and the refinement of steel grain structures. Currently, normalizing has gained wide popularity.