Steel

• Mild steel • Carbon content – 0.25%• Sulphur - 0.055%• Phosphorous - 0.055%

• Medium carbon steel• Carbon - 0.25%-0.6%

• High carbon steel or hard steel• Carbon - 0.6%-1.5%

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

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

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

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. 

• 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

 

Structural steel

• Angle sections• Channel sections• Corrugated sheets • Expanded metal • T-sections • I-sections • Plates

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

Angle sections

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

Channel section

Corrugated sheets

• Generally galvanized they are named accordingly

• Widely used for roof covering

Corrugated sheets

Expanded metal

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

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

T-section

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

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

Plates

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)

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 154.10N

• They are used as reinforcement for all type of concrete work

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

•  

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

Square bars

Flat bars

• Available in suitable widths varying from 10mm to 400mm

• Generally available are 3mm to 40mm

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

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

• 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

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

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

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

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

Welded Wire Fabrics

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