MARKET FORMS OF STEEL

Following are the standard shapes in which the rolled steel sections are available in the market-

1. Angle sections-

The Angle section may be equal legs or unequal legs. The equal angle sections are available in sizes varying from 20 mm x 20 mm x 3 mm to 200 mm x 200 mm x 25 mm. The corresponding weight per meter length are respectively 9 N and 736 N. The unequal angle sections are available in sizes varying from 30 mm x 20 mm x 3 mm to 200 mm x 150 mm x 18 mm. The corresponding weight per meter length are respectively 11 N and 469 N. The angle section extensively used in the structural steel work especially in the construction of steel roof trusses and filler joist floors.

2. Channel Section-

The channel section consist of a web with two equal flanges. A channel section is designated by the height of web and width of flange. These sections are available in sizes varying from 100 mm x 45 mm to 400 mm x 100 mm. The corresponding weights per metre length are respectively 58 N and 494 N. A channel section of size 300 mm x 100 mm with weight per metre length as 331 N. The Bureau of Indian Standards has classified channel sections as junior channel, light channel and medium channel and accordingly they are designated as I.S.J.C, I.S.L.C and I.S.M.C respectively. The channel sections are widely used as the structural members of the steel framed structures.

3. Expanded Metal

This form of steel is available in different shapes and sizes. It is prepared from sheets of mild steel which are machine cut and drawn out or expanded. A diamond mesh appearance is thus formed throughout the whole area of the sheet. The expanded metal is widely used for reinforcing concrete in foundation, roads, bridges etc. It is also used as lathing material and for partitions.

4. Corrugated Sheets

These are formed by passing steel sheets through grooves. These grooves bend and press steel sheets and corrugations are formed on the sheets. These corrugated sheets are usually galvanized and they are referred to as the galvanized sheets or G I sheets. These sheets are widely used for roof covering.

5. I- Sections

These are popularly known as the rolled steel joist or beams. It consist of two flanges connected by a web. It is designated by overall depth width of flange and weight per meter length. They are available in various sizes varying from 75 mm x 50 mm at 61 N to 600 mm x 210 mm at 995 N. Joist of size 300 mm x 150 mm at 377 N. The wide flange beams are available on sizes varying from 150 mm x 100 mm at 170 N to 600 mm x 250 mm at 1451 N. The beams suitable for columns are available in H- section which vary in sizes from 150 mm x 150 mm at 271 N to 450 mm x 250 mm at 925 N.  The Bureau of Indian Standard has classified the I section in to junior beams, light beams, medium beams, wide flange beams and heavy beams and they are accordingly desingated as ISJB, ISLB, ISMB, ISWB and ISHB respectively.

6. T- Sections

The shapes of this section is like that of letter T and it consist of flange and web. It is desingated by overall dimensions and thickness. These sections are availble in sizes varying from 20 mm x 20 mm x 3 mm to 150 mm x 150 mm x 10 mm. The coressponding weight per meter length are 9 N and 228 N respectively. T section of size 100 mm x 100 mm x 10 mm with weight per meter length as 150 N. The special T section with unequal sides bulbs at the bottom edge of web etc are also available. These sections are widely used as members of steel roof trusses and to form built up sections.

7. Plates

The plates section of steels are available in different sizes with thickness varying from 5 mm to 50 mm. The corresponding weights per square meter are 392 N and 3925 N respectively. They used mainly for the following purposes in the structural steel works.

Ø  To connect steel beams for extension of the length

Ø  To serve as tension members of steel roof truss

Ø  To form built up sections of steel

8. Ribbed Bars (HYSD Bars)

These bars are produced from the ribbed which is a deformed high strength steel. These bars have ribs or projection on their surface and they are produced by controlled cold twisting of hot rolled bars. Each bars is to be twisted individually and it is tested to conform the standard requirements. These bars are also called high yield strength deformed (HYSD) bars. the ribbed bars are available in sizes varying from 6 mm to 50 mm diameter with the corresponding weight per meter length as 2.22 N and 154.10 N. These bars are widely used as reinforcement in concrete structures such as buildings, bridge, docks and harbors structures, roads, irrigation works, piles foundations, pre-cast concrete works etc.

9. Round Bars

These are available in circular cross section with diameter varying from 5 mm to 250 mm. They are widely used as reinforcement in concrete structures, construction of steel grill work etc.  The commonly used cross-sections have diameters varying from 5 mm to 25 mm with the corresponding weights per meter length as 1.50 N and 38 N respectively.

10. Square Bars

These are available in square cross-section with sides varying from 5 mm to 250 mm. They are widely used in the construction of steel grill work for window, gates, etc. The commonly used cross-section have side varying from 5 mm to 25 mm with corresponding weight per meter length as 2 N and 49 N respectively.

11. Flat Bars

These are available in suitable widths varying from 10 mm to 400 mm with thickness varying from 3 mm to 40 mm. They are widely used in the construction of steel grill work for windows and gates.

12. Ribbed mild steel Bars

These are the hot rolled mild steel bars but during rolling steel rods, ribs are produced on them. These ribs increases the bond strength of bars. Such ribbed mild steel bars are not recommended in the code but are available in the market. They looks like high strength ribbed bars but the allowable stresses in these ribbed mild steel bars are much lower than the HYSD bars. Theses bars should not be used in RCC work.

13. Thermo-mechanically Treated Bars (TMT Bars)

Sudden quenching of red hot steel bars by a spray of water can produce steel bars with high strength at the structure with a core of mild steel. As the core of the wire is still hot the heat inside helps in tempering the surface. The result is a structure with tempered martensite on the periphery and a fine grained ferrite pearlite at the center. The combined strength of these materials raises the yield point of steel with the high percentage of elongation at ultimate failure. TMT bars are also rolled with ribs to increase the bond strength.

These are more corrosion resistance than cold twisted bars. Specially TMT-CRS (Thermo-mechanically Treated Corrosion Resistance Steel bars ) bars are also available in the market in which high corrosion resistance is achieved by adding corrosion resistant element like copper, phosphorous and chromium. These bars are produced in three grades like Fe415, Fe500, Fe550. 

14. Cold Twisted Deformed Bars (CTD Bars)

These were the first high strength steel bars introduced in India around 1960. These bars are first hot rolled out of high grade mild steel with three or more parallel straight ribs and other indentation on it. After cooling they are twisted by a separate operation so that the steel is stained beyond the elastic limit and then released. This operation raises the yield point of steel for subsequent tensile or compressive stresses. Thus its strength is increased. Normally welding is not in this type of steel as the strength of steel is increased due to cold working.

15. Welded Wire Fabrics (WWF Bars)

Welded wire fabric is fabricated from a series of wires arranged at right angles to each other and electrically welded at all intersections. It is made from medium tensile steel drawn out from higher diameter mild steel bars. It is much stronger than  mild steel are available in  different width rolls. Welded wire fabric has various uses in reinforeced concrete construction. It is mostly used for floor slabs on well compacted ground. Heavier fabrics supplied mainly in flat sheets, iis often also used in walls and for the primary reinforcement in structural floor slabs. It is also used in road and runway pavements, box culverts and small canal lining.

http://www.applechemie.com