1. Steel Mild steel Medium carbon steel High carbon steel or hard steel
Carbon content – 0.25%
Sulphur %
Phosphorous %
Medium carbon steel
Carbon %-0.6%
High carbon steel or hard steel
Carbon %-1.5%

2. Uses of mild steel
As rolled steel sections like angle, channel, plates, I and T and bar sections used in construction work
Mild steel round bars are used as steel reinforcement
Sheet made of tubes are used as roof coverings

3. Iron Iron constitutes about4.60 parts of the crust of earth
It is also contained in the leaves plant
It is basically responsible for the red color in the blood of animals
Iron ores are present in the following forms
Haematite –Fe2O3
Limnonite-2Fe2 O3.3H2O
Magnetite-Fe3 O4
Pyrite FeS2
Siderite-FeCO3

4. Factors Affecting The Physical Properties Of Steel
Carbon content- carbon increases strength but decrease ductility
Presence of impurities –impurities affect the quality of steel
Heat treatment processes –varies depending upon the type of treatment

5. Mild steel
Mild Steel is general purpose steel grade, basically used for remelting, alloying and manufacturing of fabrication of various structures.
The Steel generally made of low Carbon and Silicon.
The yield strength values are very low for Mild Steel as the name suggest.  Therefore it is not used for special purpose of reinforcing and heavy structure manufacturing. 

6. Where as, HYSD is High Yield Strength Deformed Bars have ribs on the surface and this increases the bond strength at least by 40%.  These are made of different grades and types.
Mild steel contains low Carbon content whereas HYSD is High Yield Strength Deformed bars contains more carbon content.
 Mild steel strength is low but ductile (easy to shape) and more weldable. 
HYSD is used where tensile strength requirements are high. 
HYSD is more brittle depending on the carbon content

10. Structural steel Angle sections Channel sections Corrugated sheets
Expanded metal
T-sections
I-sections
Plates

11. Angle sections May be of equal leg or unequal leg
Equal leg sections are available in varying sizes from size 20mm* m20mm*3mm to 200mm*200m m*25mm
Unequal angle sections are available from 30 mm*20mm*3mm to 200mm *150mm *18mm

12. Angle sections

13. Channel sections Available in sections 100mm*45mm to 400mm*100mm
Bureau of Indian Standard has classified the channel a junior channel ,light channel ,Medium channel

14. Channel section

15. Corrugated sheets Generally galvanized they are named accordingly
Widely used for roof covering

16. Corrugated sheets

17. Expanded metal
This form of steel is available in different shapes and sizes
Used for reinforcing foundations
diamond mesh like appearance is formed

18. T-Sections The shape of the section is that of the letter T
It is designated by overall dimension and thickness
Available varying from in sizes from 20mm*20mm*3mm to 150mm*150mm*10
Mainly used as members as steel roof truss and to form built up sections

19. T-section

20. I-Sections Known as rolled steel joist or beams
Consist of two flanges connected by a web
Designated by overall depth , width of flange and weight per meter length
Available in various sizes 75mm*50mm at 61N to 600mm*210mm at 995N
They are mainly used for beams and columns
Bureau of indian standard classify Isections in to Junior beams ,light beams ,medium beams ,wideflange beams and heavy beams and they are accordingly designated as I.S.J.B,I.S.L.B,I.S.W.B,I.S.H.B.
Used for floor beams lintels and columns

23. Plates
Plate sections are available in thickness varying from 5mm to 50mm with the corresponding weight of 392N and 3925N
They are mainly used for connecting steel beams for extension of length , to form as a tension member of steel roof truss, to form built up sections of steel

24. Plates

25. Reinforcing steel
The various types of reinforcement bars are as follows
Ribbed (HYSD ) bars
Round bars
Square bars
Flat bars
Ribbed mild steel bars
Thermo mechanically treated bars
Cold twisted deformed bars
Welded wire fabrics (WWF)

26. Ribbed (HYSD ) bars
high yield strength Deformed steel having ribs or projections in their surface
They are produced by controlled cold twisting of hot rolled bars
Available in sizes varying 6mm to 50mm with corresponding weight 2.22Nand N
They are used as reinforcement for all type of concrete work

28. Round bars
Available in circular cross- sections varying from 5mm to 250mm
Used as reinforcement in concrete structures , steel grill work
Commonly used are 5mm to 25mm dia weight 1.5N and 38N

30. Square bars Square bars
They are available in square section from 5mm to 250mm
Used in construction of steel grill work, for windows
General cross section vary from 5mm to 25mm

31. Square bars

32. Flat bars Available in suitable widths varying from 10mm to 400mm
Generally available are 3mm to 40mm

34. Ribbed mild steel bars
Hot rolled mild steel bars and during rolling ribs are produced in them . it increases the bond strength
Not recommended in the code but used
They look like HYSD bars but tensile strength will be less
Should not be used in RCC work

35. Thermomechanically treated bars TMT bars
Sudden quenching of red hot steel with spray off water can produce steel with high strength
It allows high percentage of elongation at ultimate stage
Also rolled with ribs to increase the strength

36. Corrosion resistance is more compared to cold twisted bars
Special TMT-CRS( thermo- Mechanically treated corrosion resistant steel bars ) area also available in the market
Corrosion resistance is achieved by adding corrosion resisting materials like copper phosphorous and aluminum

39. Cold twisted deformed bars
The cold rolled sections are formed from sheets, plates or flats in rolling machines or by press braking
Used in car bodies, railway coaches and different types of steel structures
The different types of cold formed sections are angle sections, channel sections, I sections, T sections, flats, tubular sections, plates, round and square bars etc

40. Advantages of cold formed steel sections
Lightness
High strength and stiffness
Ease of fabrication and mass production
Fast and easy erection and installation
High strength to weight ratio
Uniform quality
Non – shrinking and non- creeping at ambient temperature

41. Cold formed sections (light gauge steel sections )
Made from uniform steel sheets of uniform thickness by a process in cold state
These steel sheets are coated with zinc or aluminium and subsequently made into thin walled sections by cold forming process
Their thickness is normally less than 2mm

43. Welded wire fabrics
Series of wires arranged at right angles and electrically welded at all intersections
Made from medium tensile steel drawn from higher diameter density bars , in ferro-cement constructions , floor slabs etc
Can be used in reinforced concrete constructions in floor

44. Welded Wire Fabrics

45. Built up sections
When single structural steel sections are not sufficient to provide the required strength and stability for structural members, a combination of same or different steel sections are joined together to form built up sections
Made with same or different types of individual members like angles, channel, I sections or plates etc of different sizes
Joined using welding or riveting