There is a wide variety of steel available on the market, and each type has its own unique properties and characteristics. Each property may affect how that steel will perform in a given task, so it is important to find a type of steel whose properties correlate with the project at hand. Some of the important properties of steel to consider include hardness, toughness, elongation, tensile strength, yield strength, fatigue strength, malleability, durability, lustre and corrosion resistance.
Hardness is a property that is important to consider during manufacturing processes. It measures the amount of resistance that the steel has to local plastic deformation due to mechanical indentation or abrasion. Plastic deformation refers to a change in the size and shape of a material as a result of a change in temperature or applied force. Materials with a high hardness result in less machinability, therefore, causing shorter tool life. Metals are usually hardened via heat treatment after they are formed or machined to meet required specifications while keeping manufacturing costs low.
Toughness refers to a material's ability to resist fracturing when force is applied. This means that the more a metal can deform before fracturing, the tougher it is. In simpler terms, metals that have a high toughness will be able to stretch to higher degrees before breaking than those with a low toughness level.
Elongation is a similar property to toughness. It is considered a mechanical property of a metal that is the degree to which a material may be bent, stretched, or compressed before it ruptures. It is a measure of ductility that provides confidence that metals can be formed without cracking or fracturing. It is a point between tensile strength and yield strength and it is expressed as a percentage of the original length of the steel.
Tensile strength is the amount of stress that a material can withstand before becoming structurally deformed. That material will continue to fracture unless the load is reduced meaning that this level of stress will eventually cause the material to fail over time. You can combat this by adding reinforcement, increasing the cross-sectional area, switching to a higher strength material, or reducing the load. Steel has a high tensile strength which makes it highly resistant to fracture or breakage. This is one of the key reasons steel is highly used in infrastructure building.
The yield strength of a material is the maximum amount of stress that can be applied to that material before it begins to undergo significant deformation. It is at this point that carbon steel and other ductile materials will begin to change shape permanently. If stress is added to the metal but does not reach the yield point, it will return to its original shape once the stress is released. Yield strength is an important property to be aware of because it represents the upper limit of the load that can be safely applied to the metal. Springs are a good representation of having a high yield strength which allows them to remain elastic and return to their original shape after compressions.
Fatigue strength differs from yield and tensile strength because it accounts for the number of cycles a material goes through as well as the stresses it encounters. A material experiences fatigue when it is weakened due to the application of fluctuating loads that damage the material's structure and result in eventual failure. This repeated application is known as the load cycle, or the number of repetitions of load assumed to act on a material during its lifetime. The American Society for Testing and Materials (ASTM) defines fatigue strength as the limiting value of stress at which failure occurs after a given number of load cycles. In order to figure out the fatigue strength of a material, one must know the number of cycles and the loading stresses that the material will undergo. Knowing the fatigue strength and cycle limit are important during machining and processing because they can prevent fatigue failure which happens instantaneously.
Malleability refers to a property of metals that defines their ability to deform under compression and take on a new shape. This property is important during processes such as is hammering, pressing, or rolling steel into thin sheets. A metal's malleability can be measured by how much compressive stress it can withstand without breaking. This physical property allows the steel to be compressed into sheets of variable size and thickness.
Durability can have many different definitions and interpretations depending on the material and the project at hand. Durability can refer to other properties such as strength, hardness, corrosion resistance, wear resistance, and impact toughness. It is important to communicate with all parties involved in a project when referring to the durability of a material This will prevent confusion and assure that all the right properties are taken into consideration. Steel is high in hardness which reflects its ability to resist strain. It is long-lasting and resistant to external wear and tear. These characteristics are why steel is considered a durable material.
Lustre is a property that defines how light is reflected on a mineral's surface. Metallic lustre refers to minerals that are opaque, translucent, and have the appearance of polished metal. A simple definition of lustre is the brightness that a shiny surface has. Steel has a very attractive outer appearance compared to other metals. It is silvery in color with a shiny, lustrous outer surface.
One of the final properties with significant importance in the steel industry is corrosion resistance. Corrosion happens to steel when rust forms on an exposed surface due to the iron molecules in the metal reacting with oxygen in the presence of water, acids or other harsh industrial chemicals to produce iron oxides. Corrosion Resistance in the terms of steel is the material's ability to protect the surface from corrosion. Stainless steels are steel alloys that contain a mix of different elements including iron and some amount of chromium. The chromium oxidizes quickly which forms a protective layer on the surface making it corrosion resistant. Resistance to corrosion can also be achieved by using products/substances such as paints, coatings, coatings or corrosion inhibitors.