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Steel is a fundamental material in the mechanical industry
Steel is an alloy of iron (Fe) and carbon (C) that is used in a variety of applications due to its strength and durability. The percentage of carbon varies between 0.01% and 2.11% by mass of its composition. If the alloy has a carbon concentration greater than 2.11%, castings are produced, which are much more fragile than steel and cannot be forged, but rather have to be molded. There are more than 5,000 different types of steel, each adapted to different needs in the industry, with their unique properties that make them suitable for certain applications.
Types of steel
Let’s look at the 3 most common types of steel:
Carbon Steel
It is the most basic type of steel. It represents approximately 90% of total steel production. It is classified based on the percentage of carbon, which can vary from approximately 0.2% to 2.1%, into three subtypes: low, medium and high. Carbon atoms distort the structure of the iron lattice, making it difficult for dislocations to move within the crystal lattice. Increasing the carbon content increases the proportion of cementite in the steel. Since cementite is relatively hard, the hardness of the steel increases. This results in a stronger, harder steel. Now, an increase in hardness can be accompanied by a decrease in ductility, which causes an increase in the brittleness of the steel. From a carbon concentration of 0.8%, additional precipitation of cementite occurs at the grain boundaries, resulting in an increase in brittleness. Therefore, it is important to control the hardness of the steel in its composition depending on its purpose.
Stainless steel
This type of steel contains a minimum of 10.5% chromium by mass. This chromium alloy is the minimum necessary to generate a self-healing surface protective layer (passive layer), which provides corrosion resistance. They may also contain other elements such as nickel, tungsten and molybdenum. These additional alloying elements can improve the properties of stainless steel, such as its corrosion resistance and mechanical strength. It is commonly used in applications where hygiene is required, such as in the food and medical industries.
Alloy Steel
As we have seen, steel is an alloy of iron and carbon, but the term alloy steel generally only refers to steels that contain other elements, such as vanadium, molybdenum, or cobalt, in sufficient quantities to alter the properties of the base steel. The alloy with these materials varies between 1.0% and 50% by weight with the aim of improving their mechanical properties, such as heat resistance and durability.
Use of steel in the mechanical industry
Steel is essential in the mechanical industry, where it is used to manufacture a variety of parts, including molds, dies and machining. Its strength and durability make it ideal for these applications, as it can withstand the high pressures and temperatures to which these parts are subjected. Now, the appropriate steel must be used, because the harder it is, the more difficult it is to machine.