What is the Difference Between Mild Steel and High Tensile Steel?

Steel is a commonly used construction material since the 17th century. With steady improvements in the quality and production process, steel has attained the status of the most popular construction material across the world.

Most concrete construction in the world is cast-in-place reinforced concrete. In reinforced concrete structures, steel reinforcement is placed into the concrete to provide the tensile resistance for carrying tensile loads.

Steel is a commonly used construction material across the world. From the earliest known production of steel in Anatolia in 1800 BC to the Wootz steel of South India in 6th century BC to quench- hardened steel of China of 200 BC, there has always been upgradation in quality and production process of this most sought after alloy of iron and carbon. Steel can significantly contribute to the strength and stiffness before cracks occurs in reinforced concrete. This behavior has led engineers to develop prestressed concrete, which uses high tensile steel to compensate compressive load.

The high tensile steel is the latent advancement in the construction field and is most popularly employed as supporting skeletons for the construction of large buildings and structures such as stadiums, skyscrapers and bridges. Steel is extensively used for medium to high-rise buildings, long span bridges, industrial structures, airports, transmission towers, overhead tanks, chimneys etc.

But how high tensile steel is different from the mild steel. Let see the difference between High Tensile Steel Vs Mild Steel.

Comparison of Mild Steel and High Tensile Steel

01. Definition

Mild Steel

High Tensile Steel

02. Synonyms

Mild Steel

  • Mild steel is also known as Low Carbon Steel OR Soft Steel.

High Tensile Steel

  • According to ‘S.K.Duggal’ (Author of Building Materials), High tensile steel is known as Medium Carbon Steel OR High Strength Steel. High tensile steel is also called as HT Steel.

03. Composition

Mild Steel

  • Carbon Steel is unalloyed steel, which contains elements such as Carbon, Manganese, Phosphorus, Sulphur and Silicon in traces. Mild steel is a type of carbon steel which contains 0.15 – 0.25 % carbon.

High Tensile Steel

  • The carbon content in high tensile steel is 0.60 – 0.80 %, Manganese 0.60 %, Silicon 0.20 %, Sulphur 0.05 % and Phosphorus 0.05%.

04. Strength

Strength of material is the capacity to resist a force, pressure or stress.

Mild Steel

  • Strength of mild steel is less than the high tensile steel.

High Tensile Steel

  • Strength of high tensile steel is more than mild steel.

05. Ultimate Tensile Strength

Ultimate tensile strength is the maximum stress a material can endure under a resultant tensile force or stress.

Mild Steel

  • The ultimate tensile strength of mild steel varies from 600 to 800 N/mm2.

High Tensile Steel

  • The ultimate tensile strength of high tensile steel is around 2000 N/mm2.

06. Hardness

Hardness is the ability of a material to resist the penetration by a harder body. According to ‘Er. M. K. Gupta’ (Author of Nabhi’s Practical Handbook on Building Construction), steel becomes harder as its carbon content gets increased.

Mild Steel

  • The hardness of mild steel is less than high tensile steel.

High Tensile Steel

  • The hardness of high tensile steel is more than mild steel.

07. Brittleness

Brittleness is a measure of how easily the given material breaks, characterized by little or no plastic deformation. A material which breaks into pieces or which can be easily reduced to powdered form is known as a brittle material. E.g. Glass. A deformation is said to be plastic when the solid deforms on loading, and the change in shape remains even after the load is removed.

Mild Steel

  • The brittleness of mild steel is less than high tensile steel.

High Tensile Steel

  • The brittleness of high tensile steel is more than mild steel.

08. Toughness

Toughness is a material property indicating the energy required to break a material. A material which does not easily break under a hammer is called tough material. According to ‘P. N. Khanna’ (Author of Indian Practical Civil Engineers’ Handbook), Toughness deceases with the increase in carbon content.

Mild Steel

  • The toughness of mild steel is more than high tensile steel.

High Tensile Steel

  • The toughness of high tensile steel is less than mild steel.

09. Malleability

Malleability of material is defined as its ability that material can be hammered or pressed into shape without breaking or cracking.

Mild Steel

  • The malleability of mild steel is more than high tensile steel.

High Tensile Steel

  • The malleability of high tensile steel is less than mild steel.

10. Ductility

Ductility is the ability of a material to undergo plastic deformation without cracking or breaking. According to ‘Francis D. K. Ching’ (Author of Building Construction Illustrated), with the increase in carbon content, the ductility decreases.

Mild Steel

  • Mild steel is more ductile than high tensile steel.

High Tensile Steel

  • High tensile steel is less ductile than mild steel.

11. Weldability

Weldability is an ability of metal or other material to get welded under specific condition.

Mild Steel

  • The weldability of mild steel is more than high tensile steel.

High Tensile Steel

  • The weldability of high tensile steel is less than mild steel.

12. Rusting

Rusting is a form of material degradation highly prevalent in metals, especially ferrous metals and usually initiated by the presence of oxygen and water.

Mild Steel

  • Mild steel rusts rapidly and easily than high tensile steel.

High Tensile Steel

  • High tensile steel does not rust easily.

13. Corrosion Resistance

Corrosion Resistance of material is defined as its ability to withstand contact with ambient natural factors without degradation or change in properties.

Mild Steel

  • The corrosion resistance of mild steel is more than high tensile steel.

High Tensile Steel

  • The corrosion resistance of high tensile steel is less than mild steel.

14. Uses

Mild Steel

  • Mild steel is used in the form of rolled sections, reinforcing bars, roof coverings and sheet piles etc.
Mild Steel Chequered Plate, Mild Steel Channels, Mild Steel I – Beam, Mild Steel Reinforcing Bars

High Tensile Steel

High Tensile Steel is used for

  • Pre tensioning or Post tensioning of prestressed concrete construction
  • Various kind of lifting, hoisting and pulling
  • Hydropower stations, atomic reactors and nuclear power stations.
High Tensile Steel Cable, High Tensile Steel Plate, Post Tensioning of High Tensile Steel

Final Thoughts:

In a nutshell, carbon, an essential constituent of steel, gives strength and hardness. But the increase in the percentage of carbon correspondingly reduces ductility, malleability and toughness. The article clearly explains the difference between Mild Steel with low carbon and High Tensile Steel with higher percentage of carbon. Mild steel and High tensile steel differ in their constituents, properties and uses. Mild steel is preferred when working with a low budget and strength, while high tensile steel is widely used in prestressed concrete constructions for bridges, large span structures etc.

Also Read:

HSLA Steel | Fundamentals of High Strength Steel

Image Courtesy – Image 2(a), Image 2(b), Image 2(c)

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