Steel is primarily an alloy of iron and carbon and it is known to have been in use since 1800 BC. The right concentration of carbon in iron gives it immense tensile strength and at a very low cost. This is the main reason why it is one of the most widely used alloys in production today.
Steel manufacturing begins with the smelting of iron ore followed by removing impurities like phosphorus, silica, and sulphur. In the ore form, the concentration of carbon is more than the desired levels that give steel its unique properties. So, steel manufacturers reprocess the molten metal to reduce the carbon content to the required amount.
It is also at this point that other elements can be added to the smelted compound of iron ore that creates distinct varieties of steel. Each one of the types of steel can be used for specific industry applications ranging from construction to structure reinforcement. In order to keep a track of the salient features of steel, manufacturers have created a nomenclature system that is both systematic and exhaustive.
Keeping track of the different kinds of stainless steel that are available on the market can appear to be a daunting task at first but when you understand the naming system and the variable that determines the property of steel, it becomes extremely simple.
The Types of Steel
In order to understand the designations and nomenclature system of stainless steel, we must first take a look at the different types of stainless steel available on the market. The classification of different steel is done based on the arrangement of its molecules, also referred to as its crystalline structure.
The following are the three main types of steel;
- Martensitic Stainless Steel: This is one of the least common types of steel produced by manufacturers. It is characterised by its two primary grade types, 410 and 420. Martensitic stainless steel is known for its phenomenal anti-corrosive properties. It includes blends of elements like Molybdenum, Nickel, Boron and even Titanium in some cases.
- Ferritic Stainless Steel: This stainless steel class comes in the grades labelled 430 and 434. These are magnetic steel variants with low densities of chromium and nickel in them. They can be used in various applications ranging from kitchenware to industrial equipment, making them the best suited for engineering situations.
- Austenitic Stainless Steel: The most commonly used type of stainless steel is the Austenitic, with designated grades 304, 316 and 317. Of these predominantly used grade types, 316 stainless steel is the second most common of the 300 series. They are non-magnetic and corrosion-resistant. This property is why they are used in industrial and domestic situations
316/316L Stainless Steel: The ‘L’ Designation
Type 316 stainless steel is commonly used for engineering applications, especially in construction and fabrication, due to its corrosion-resistant properties. Type 316 stainless steel is manufactured in another grade due to its widespread potential, and it is differentiated by using the letter ‘L’ in its designation. The L denotes the low content of carbon in the steel. 316L is best known among fabricators for being resistant to cracks after completion of the welding. This makes 316L the preferred choice of fabricators who look to build metallic structures for industry applications.
There are other grade denotations such as F, N, H, and several others besides L that are used by tweaking composition specifications of carbon, manganese, silicon, phosphorus, sulphur, chromium, molybdenum, nickel, etc. for desired properties.
The typical applications of steel include;
- Food preparation equipment
- laboratory equipment
- chemical containers for transport
- heat exchangers
- screens for mining
- coastal architectural panelling
- boat fittings
- water filtration.
Steel has a property of cracking upon cooling wherever welding is required. The high temperatures of the welding process induce what is called ‘hot brittleness’ in the steel as it cools. This makes structures built using high carbon content steel more susceptible to damage due to the formation of cracks in the welded area of the metal.
The low carbon content of 316L provides an effective solution to this widespread engineering problem of 316 stainless steel. This little variation in the application can make a significant difference to your operational costs and quality assurance parameters as a business organisation.