Steel is an extremely versatile material. It is strong, durable, and ductile enough to be employed in a variety of applications, but construction is the most closely associated with it. Properties of steel have an impact on the design and construction of steel structures, hence understanding steel material properties is critical. This blog explores physical, chemical, and thermal properties of steel in the civil engineering field, which will help you to understand why steel plays such a key role in today’s construction industry.
What is Steel?
Steel is an alloy of iron and carbon, containing less than 2% carbon, about 1% manganese, and small amounts of silicon, phosphorus, sulphur, copper and oxygen. Despite steel’s low carbon content, carbon has a big influence on physical properties of steel, making it harder and more durable than pure iron.
Adding other elements like chromium, nickel, manganese, and vanadium can boost properties of steel even more. Common steel is created by the purification of iron and combining it with other metals and minerals. Steel is a vital material for the construction industry.
Properties of Steel:
Let’s understand in depth the physical properties, chemical properties and thermal properties of steel.
Physical Properties of Steel:
Steel has the capacity to support heavy weights without being heavy itself, and it shows resilience in tough environments without failing. Engineers and builders who understand these properties of steel can apply it more appropriately to address the requirements of modern structures and technological advancements.
Density:
One of the most essential physical properties of steel is its density. Density is the measurement of the ratio of matter in an object to its volume. Steel becomes stronger as its density increases. The density of steel varies from 7,850 to 8,050 kilograms per cubic metre.
Young’s Modulus:
Young’s modulus is an important physical property of steel. It shows how well steel goes back to its original shape after being pulled. Steel with a higher Young’s modulus can handle more force without bending. The Young’s modulus for steel is between 190 and 210 gigapascals.
Tensile Strength:
Tensile strength denotes how much force steel can take before it breaks apart. The higher the tensile strength, the tougher the material. Steel’s tensile strength varies in the range from 400 to 2,000 megapascals.
Shear Strength:
A material’s shear strength is defined as its capacity to withstand forces that cause the internal structure to slide against itself. The shear strength of steel is specified at the point of failure under shear stress, and it is approximately 0.57 times structural steel’s yield stress.
Ductility:
Ductility is one of the most important physical properties of steel that allows it to be hammered thin or stretched into wires without breaking. Steel can bend significantly before failure, which is critical for absorbing energy during collisions and seismic activity.
Yield Strength:
Yield strength is the highest stress that a material can withstand before permanently changing shape and failing to bounce back. This tests the material’s ‘ductile’ character. If the stress level does not exceed the yield strength point, the material will regain its original shape after the stress is relieved. High yield strength indicates that the material has high strength. The yield strength of steel can range between 250 and 1,500 megapascals.
Chemical Properties of Steel:
The chemical properties of steel are largely concerned with its composition and how its constituent elements affect its behaviour and performance. Steel has the following key chemical properties:
The Carbon Content:
The concentration of carbon in steel can range from less than 0.1% to more than 2%. It has a considerable impact on ductility, hardness, and strength of steel. Lower carbon steels are more ductile, but higher carbon steels are harder and more durable.
Alloying Elements
The following elements are present in steel composition:
- Manganese (Mn): Manganese, which is typically found in percentages ranging from 0.3 to 2%, enhances hardness, tensile strength, and wear and abrasion resistance. It also aids in the deoxidation of steel by eliminating sulphur and oxygen contaminants.
- Chromium (Cr): Chromium, which is in percentage ranging from 10% to 30%, is used in stainless steel to improve corrosion resistance, hardness, and wear resistance.
- Nickel (Ni): Nickel is added in steel in levels ranging from 2-20%. It improves hardness and corrosion resistance.
- Molybdenum (Mo): Found in trace levels (0.1-0.5%), molybdenum improves hardness, strength at high temperatures, and corrosion resistance.
- Vanadium (V): Added in trace levels (0.1-0.5%), vanadium increases strength, toughness, and wear resistance.
- Silicon (Si): Silicon improves strength and flexibility and is often found in concentrations ranging from 0.2 to 2%.
- Copper (Cu): Copper, when added to steel in moderate quantities (up to 0.4%), helps in improving the corrosion resistance of steel.
Thermal Properties of Steel:
Steel has several essential thermal properties that make it useful in a variety of applications, particularly construction and manufacturing. Here’s an overview:
Thermal conductivity:
Thermal conductivity refers to a material’s capacity to conduct and transfer heat. Materials with lower thermal conductivity provide better heat insulation. Carbon steel has a thermal conductivity of 45-60 W/m·K. Thermal conductivity, which is one of the important stainless steel properties, is about 15 W/m·K, which means it doesn’t conduct heat well.
Melting Point:
As there are different types of steel available in the market, there is no standard melting point for steel. The melting point of steel lies in the range of 1370-1510°C. Steel’s high melting point allows it to be employed in high-temperature applications like power plants and furnaces.
Thermal Expansion:
Thermal expansion describes the tendency of steel to expand when heated. The coefficient of thermal expansion of carbon steel has a range of 11x 10⁻⁶/°C to 13 x 10⁻⁶/°C. Stainless steel often has a somewhat higher coefficient.
Specific Heat:
The specific heat of an object is the amount of heat required to raise the temperature of a unit mass of the object by one degree. A high specific heat value means that the object has more heat insulation. The measurement units are Joules per Kilogram Kelvin. The specific heat of carbon steel ranges from 450 to 2081 J/kg-K, while that of structural alloy steel ranges from 452 to 1499 J/kg-K.
The above physical, chemical, and thermal properties of steel make it an excellent choice for a wide range of applications in the construction industry. It can hold heavy loads without weighing too much, and it stands up well to harsh conditions without breaking down. When engineers and builders know these properties of steel in civil engineering, they can use it better to meet the needs of today’s structures and aid with new technological advances.