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Classification of Steel


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Material Science and Engineering
Ferrous Materials
Classification of Steel
Low carbon steel
Medium Carbon steel
High carbon steel
Structural steel
stainless steel

Published in: Engineering
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Classification of Steel

  1. 1. MATERIAL SCIENCE AND ENGINEERING Classification Of Steels
  2. 2. REFERENCES  Materials Science and Engineering, V. Raghavan, Fifth Edition, Prentice Hall of India Pvt. Ltd., New Delhi, 2004.  Materials Science and Engineering: An Introduction, William D. Callister John Wiley & Sons, 2010. ONLINE - Nptel
  3. 3. Ferrous Materials Ferrous Steels Cast iron Low Alloy High Alloy Tool steel Stainless steel
  5. 5. FERROUS MATERIAL - STEELS . –Low Carbon (<0.25 wt% C) –Medium Carbon (0.25 to 0.60 wt% C) –High Carbon (0.6 to 1.4 wt% C) • Steels - alloys of iron-carbon. - May contain other alloying elements. • Several grades are available • Low Alloy (<10 wt%) – Stainless Steel (>11 wt% Cr) - Tool Steel •High Alloy
  7. 7. Low Carbon Steel - Also known as Mild Steel - Tensile strength of 555 N/mm - Hardness of 140 BHN - Bright fibrous structure - Tough , malleable , ductile and more elastic than wrought iron - Melting point 1410
  8. 8. Low Carbon Steel Plain carbon steels - very low content of alloying elements and small amounts of Mn. Most abundant grade of steel is low carbon steel – greatest quantity produced; least expensive. Not responsive to heat treatment; cold working needed to improve the strength. Good Weldability and machinability High Strength, Low Alloy (HSLA) steels - alloying elements (like Cu, V, Ni and Mo) up to 10 wt %; have higher strengths and may be heat treated.
  9. 9. LOW CARBON STEEL Compositions of some low carbon and low alloy steels
  10. 10. AISI - SAE CLASSIFICATION SYSTEM AISI XXXX American Iron and Steel Institute (AISI)  classifies alloys by chemistry  4 digit number  1st number is the major alloying element  2nd number designates the subgroup alloying element OR the relative percent of primary alloying element.  last two numbers approximate amount of carbon (expresses in 0.01%)
  11. 11. AISI - SAE CLASSIFICATION SYSTEM  letter prefix to designate the process used to produce the steel  E = electric furnace  X = indicates permissible variations  If a letter is inserted between the 2nd and 3rd number  B = boron has been added  L = lead has been added  Letter suffix  H = when hardenability is a major requirement  Other designation organizations  ASTM and MIL
  12. 12. MEDIUM CARBON STEEL Carbon content in the range of 0.3 – 0.6%. Can be heat treated - austenitizing, quenching and then tempering. Most often used in tempered condition – tempered martensite Medium carbon steels have low hardenability Addition of Cr, Ni, Mo improves the heat treating capacity Heat treated alloys are stronger but have lower ductility Typical applications – Railway wheels and tracks, gears, crankshafts.
  13. 13. MEDIUM CARBON STEEL - Bright fibrous structure when fractured - Tough and more elastic in comparison to wrought iron - Eaisly forged , welded , elongated due to ductility - Good malleability - Its tensile strength is better than cast iron and wrought iron - Compressive strength is better than wrought iron but lesser than cast iron
  15. 15. APPLICATIONS -
  16. 16. STRUCTURAL STEELS - Possess high strength and toughness - resistance to softening at elevated temperatures - resistance to corrosion - possess weldability , workability & high hardenability - principle alloying elements chromium , nickel , manganese
  18. 18. EFFECTS OF ALLOYING ELEMENTS ON STEEL  Manganese contributes to strength and hardness; dependent upon the carbon content. Increasing the manganese content decreases ductility and weldability. Manganese has a significant effect on the hardenability of steel.  Phosphorus increases strength and hardness and decreases ductility and notch impact toughness of steel. The adverse effects on ductility and toughness are greater in quenched and tempered higher-carbon steels.  Sulfur decreases ductility and notch impact toughness especially in the transverse direction. Weldability decreases with increasing sulfur content. Sulfur is found primarily in the form of sulfide inclusions.  Silicon is one of the principal deoxidizers used in steelmaking. Silicon is less effective than manganese in increasing as-rolled strength and hardness. In low- carbon steels, silicon is generally detrimental to surface quality.  Copper in significant amounts is detrimental to hot-working steels. Copper can be detrimental to surface quality. Copper is beneficial to atmospheric corrosion resistance when present in amounts exceeding 0.20%.  Nickel is a ferrite strengthener. Nickel does not form carbides in steel. It remains in solution in ferrite, strengthening and toughening the ferrite phase. Nickel increases the hardenability and impact strength of steels.  Molybdenum increases the hardenability of steel. It enhances the creep strength of low-alloy steels at elevated temperatures.