Steel has now become an integral part of day-to-day life. It is an important invention for man-kind. We have studied in school about the, there are various types of steel available, and each one of them has their own types of chemical, physical, as well as environmental properties. Steel is the perfect amalgamation of carbon and iron, if you describe it in a layman’s term. To determine properties of steel, the amount of carbon plays some pivotal role along with additional alloy items and impurity levels. Types of steel
In general, steel is of primarily four types; alloy steel, carbon steel, stainless steel and tool steel.
- The carbon content can be within a range of 0.04% to 1.5% and such steel is called carbon steel. The first one of the sub-divided group is low carbon steel. It is also termed as mild steel and comprises of 0.3% of carbon.
- The second one is the medium steel. Here, the contents of carbon are within the range from 0.3% to 0.6%.
- The last one in the kitty is high carbon steel. Here, the amount of carbon will be more than 0.6%, and has highest component of carbon in it.
While alloy steel contains alloying elements other than carbon, such as, manganese, silicon, nickel, titanium, copper, chromium and aluminum
- This steel is widely used in the industry due to the cost factor & it’s also widely available. It also has good mechanical properties. Biggest advantage is this steel is responsive to heat and other chemical treatments. Hence, you will see the usage of alloy steels are in auto parts, pipelines, power generators, transformers and even in electric motors.
A quick story on this. In 1913, English metallurgist Harry Brearly, working on a project to improve rifle barrels, accidentally discovered that adding chromium to low carbon steel gives it stain resistance.
Stainless steels have traditionally been divided into types depending on their microstructure at room temperature, which gives a rough indication of their composition and properties.
With a chromium level between 10% and 20%, stainless steels are known for their high corrosion strength. As the amount of chromium is high, therefore; corrosion resistant power of steel is going to be 200 times more, if you compare it to mild steel fabrication. It is further divided into:
- Ferritic steels. It comprises of 12% to 17% of chromium, some nickel parts and carbon content, less than 0.1%.
Austenitic steel has 18% of chromium and less than 0.8% of carbon. It comprises of 18% of nickel. The austenitic grades are the largest type of stainless steel fabrication.
- The martensitic steel is the smallest group of stainless steels. For improved strength they have a higher carbon content compared to other grades. Nitrogen is added in some cases to further improve strength.
- Duplex stainless steel: – This steel has ferritic-austenitic microstructure that contributes to high strength and high resistance to stress corrosion cracking.
The last one in this group is tool steel. As the name suggests this is used to make tools. Specific tool applications are dies (stamping or extrusion), cutting, mold making, or impact applications like hammers (personal or industrial). It is also a common material used to make knives. It comprises of molybdenum, tungsten, vanadium and cobalt. It helps in increasing durability and heat resistance. This kind of steel is best suited for drilling and cutting equipment. You can further divide into segment into various types, depending on their shapes. From long tubular ones to flat steel, options are basically limitless. There are other types of steel products available such as fittings, valves and flanges.