Introduction of steel (types, mechanical properties, stress-strain curve, advantages and disadvantages).

Steel -
  • It is an important structural material which is broadly used to construct structural member.
  • It is an alloy of pure iron, carbon, chromium, Nickel and some other elements.
  • In the steel, corrosion exists.
Stainless steel -
  • It is the alloy of pure iron and chromium. 11% chromium content are present.
  • It is a corrosion resistance material.
Types of steel -



Effect of carbon content on steel characteristics-
  • If carbon content in steel increases, the strength, hardness and brittleness will increase.
  • If carbon content in steel decreases, the strength of steel will decrease and ductility of the steel will increase. Steel becomes soft.
Stress-strain curve of Mild steel -


  1. OAB - It represents a straight line curve. The strain produced is proportional to the stress producing it. i.e, it obeys Hooke's law.
  2. A - represents the limit of proportionality - the stress beyond which linear variation ceases.
  3. B - represents the elastic limit - the maximum stress up to which a specimen regains its original length on removal of the applied load. This stress in general, is not measured and B is assumed to coincide with A.
  4. C'C - represents the upper, lower yield point - the stress at which there is a definite increase in strain without any further increase in stress.(0.0012)
  5. CD - represents plastic yielding - it is the strain which occurs after the yield point, with no increase in stress.(0.014)
  6. DE - represents strain hardening - it is a range where additional stress produces additional strain. Strain increases fast with stress till ultimate load is reached.
  7. E - represents the ultimate stress - the stress corresponding to the ultimate load. The initial slope of this region is about 4% of young's modulus. At a strain of at least 0.2, the stress reaches its maximum value E.
  8. EF - stress falls with rapid increase in strain till the specimen breaks.
  9. F - represents breaking stress - the stress corresponding to the breaking load.
Mechanical properties of structural steels -


Advantages of steel as a structural material -
  • Steel members have high strength per unit weight.
  • Being light, they can be conveniently handled and transported.
  • They have a long life.
  • Its properties do not change with time.
  • It does not fail suddenly, but gives visible evidence of impending failure by large deflections.
  • They can be erected at a faster rate.
  • Steel has highest scrap value among all building materials.
Disadvantages of steel as a structural material -
  • Steel structures are subjected to corrosion, if they are placed in exposed conditions.
  • They require fire proof treatment, frequent painting and skilled labour to be established. So, they are costly. 

Thank you.

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