Steels are alloys of iron and carbon along with other elements like silicon, manganese, and nickel. Steels are classified as plain carbon steels, which contain up to 1.5% carbon, and alloy steels, which contain additional alloying elements above 1.5% carbon. Plain carbon steels are further divided into low carbon (<0.25% C), medium carbon (0.25-0.6% C), and high carbon (>0.6% C) grades based on their carbon content and the properties it provides such as strength, hardness, and machinability for different applications. Alloy steels add additional elements like chromium, nickel, and molybdenum to further improve properties

1. STEELS
• Steels are alloys of IRON and CARBON, not only carbon
other elements like silicon, manganese, sulphur, nickel, etc.
• CLASSIFICATION OF STEELS
1. PLAIN CARBON (NON-ALLOY) STEELS
1. Low carbon steels
2. Medium carbon steels
3. High carbon steels
2. ALLOY STEELS
1. Low alloy steels
2. High alloy steels
CARBON

2. PLAIN CARBON STEELS
• DEF: Carbon is the alloying element that essentially
controls the properties of alloys, and in which the
amount of manganese cannot exceed 1.65% and
copper and silicon must be less than 0.6%
• COMPOSITION:
– CARBON UP TO 1.5% COPPER UP TO 0.6%
– MANGANESE UP TO 1.65% SILICON UP TO 0.6%

3. PLAIN CARBON STEELS
• CHARACTERISTICS:
– Moderately priced steels (Due to absence of large
amount of alloying elements)
– Sufficiently ductile
– PRODUCTS: Sheet, Plates, Tube, Wire.
• APPLICATIONS:
– Mass production in automobile appliances.
– Ball bearings, base plates, structural members, etc.

4. CLASSIFICATION OF PLAIN CARBON STEELS
1. LOW-CARBON STEELS
– Less than 0.25% carbon containing
2. MEDIUM-CARBON STEELS
– Containing between 0.25% to 0.60%carbon
3. HIGH-CARBON STEELS
– Containing more than 0.60% carbon

5. LOW CARBON STEELS
• Low carbon steels that contain less than 0.25%
carbon
• Low carbon steels are knows as MILD STEELS.
• CHARACTERISTICS:
– Soft and weak, outstanding ductility and toughness
– Good formability and weldability
– Least expensive to produce
• APPLICATIONS:
– Automobile body components, Bridges
– Structural shapes( I- beams etc)
– Pipelines, Buildings, tin cans.

6. MEDIUM CARBON STEELS
• Low carbon steels that contain between 0.25%
and 0.60% carbon
• These steels may be Heat treated by
Austenitizing, Quenching and then tempering to
improve MECHANICAL PROPERTIES.
• CHARACTERISTICS:
– Low hardenabilities
– High strength and hardness properties are
achieved.(Sacrifice of Ductility and Toughness)
• APPLICATIONS:
– Railway tracks, Railway wheels gears, crankshafts.

7. HIGH CARBON STEELS
• High carbon steels that contain more than 0.60%
carbon.
• CHARACTERISTICS:
– Hardest and strongest Least ductile( more brittle)
– More wear resistant
– Sharp cutting edge tools.
• APPLICATIONS:
– Cutting tools and dies
– Knives
– Blades
– High strength Wire

8. ALLOY STEELS
• Alloy steels mean any steels other than CARBON
STEELS.
• ALLOYING ELEMENTS:
– Chromium, nickel, tungsten
– Molybdenium, vanadium, cobalt
– Boron, copper others
• PURPOSE OF ALLOYING:
– To increase strength, To improve hardness
– To improve Toughness, Machinability, Ductility
– To improve resistance to abrasion and wear
– To enhance grain size control.

9. CLASSIFICATION OF ALLOY
STEELS
1. LOW ALLOY STEELS
1. AISI steels
2. HSLA steels
2. HIGH ALLOY STEELS
1. Tool and die steels
2. Stainless steels
STEELS

10. LOW ALLOY STEELS
• Low alloy steels are steels which contain upto 3 to
4% of one or more alloying elements
• They have similar microstructure and require
similar heat treatment like plain carbon steels.
• Presence of alloying elements increase strength
and hardenability.

11. TYPES OF LOW ALLOY STEELS
1. AISI STEELS
• American Iron and Steel Institute steels that are generally
used in machine construction.
• AISI steels normally have LESS THAN 5% of total addition
elements such as Cr, Ni, V, etc,.
2. HSLA STEELS
• High Strength and Low Alloy steels is also knows as
micro alloyed steels
• Elements are Al,V, etc.

12. HIGH ALLOY STEELS
• High alloy steels are steels which contain more
than 5% of one or more alloying elements
• They have similar microstructure and require
different heat treatment than of plain carbon steels.
• The room temperature structures after normalizing
may be austenitic, martensitic

13. TYPES OF HIGH ALLOY STEELS
1. TOOLAND DIE STEELS
• High quality alloys are used which require special
characteristics like HARDENABILITY, WEAR
RESISTANCE, TO SOFTENIG ON HEATING.
2. STAINLESS STEELS
• Used for improving corrosion resistance.