High Yielding Strength Deformed bars as Reinforcement; A Quick Outline

High Yielding Strength Deformed bars as Reinforcement; A Quick Outline

Ribbed bars or High Yield Strength Deformed (HYSD) bars are produced from the high strengthened ribbed or deformed steel. This steel is of immense strength and the bars fabricated will have ribs or projections on the exterior. The ribs ensure and enhance the bonding between concrete and the bar.  The bars are formed by controlled cold twisting of hot-rolled bars. Each bar is to be twisted separately and it is examined to fortify the standard specification and requirement. 

HYSD bars provide more tensile strength than the mild steel bars. The unique construction of the bars makes it resistant to corrosion and weldable. The HYSD rods are widely available in diameters varying from 6mm to 50mm with corresponding weights per meter length as 2.22 N and 154.10 N.  

High Yield Strength Deformed (HYSD) bars are widely used as reinforcement in mass concrete edifices such as constructing bridges, docks, and harbor buildings, roads, irrigation works, pile bases pre-cast concrete works, etc. Mild Steel is inexpensive and easy to form and it is radically used for remelting, alloying and casting of fabrication of steel formations. Mild steel is often used when massive quantities of steel are necessitated. The Steel is commonly made of low Carbon and Silicon. Mild steel has a comparatively low tensile strength. Therefore it is not used for specific purposes such as reinforcement and complicated structure building. For HYSD, its ribs on the surface increase the bond strength at least by 40%. As HYSD steel is stronger, it saves cost too. 

HYSD bars can be bend 180° without causing any crack or fracture in the exterior. This property of the bars enhances its flexibility and effectiveness. Certain types of HYSD bars can be weld by using electric flash butt welding or arc welding. The structural properties of the HYSD bars make it easier to design with higher stress and easy to identify. Since the bonding properties of these bars are pretty good, end hooks are not required for the construction. Cost-effectiveness is another advantage of HYSD bars. High Yield Strength Deformed bars are an efficient and economical reinforcement. They are quite flexible that the process of bending,  fixing and handling is simplified to a great degree. Hence it results in fewer labor charges too. 

The mechanical properties of HYSD bars as per IS standards is as follows. 

Property Fe

415

Fe 415D Fe

415S

Fe

500

Fe

500D

Fe

500S

Fe

550

Fe

550D

Fe

600

i 0.2 percent proof stress/ yield

stress, Min, N/mm2

415.0 415.0 415.0 500.0 500.0 500.0 550.0 550.0 600.0
ii 0.2 percent proof stress/ yield

stress, Max, N/mm2

540.0 625.0
iii TS/YS ratio1), N/mm2 ≥ 1.10, but

TS not less

than 485.0

N/mm2

≥ 1.12, but

TS not less

than 500.0

N/mm2

1.25 ≥ 1.08, but

TS not less

than 545.0

N/mm2

≥ 1.10, but

TS not less

than 565.0

N/mm2

1.25 ≥  1.06, but

TS not less

than 585

N/mm2

≥ 1.08, but

TS not less

than 600.0

N/mm2

≥ 1.06, but

TS not less

than 660

N/mm2

iv Elongation, percent, min. on

gauge length 5.65A, where A is

the cross-sectional area of the

test piece

14.5 18.0 20.0 12.0 16.0 18.0 10.0 14.5 10.0
v Total elongation at maximum

force, percent, Min, on gauge

length 5.65A, where A is the

cross-sectional area of the test

piece 

5 10 5 8 5

Although High Yeilding Strength Deformed Bars have more enhanced yield strength than Mild Steel, they are much inclined to deformations than TMT Steel bars. Both mild steel and HYSD bars are weaker than TMT Steel bars.

TMT stands for Thermo-Mechanical Treatment, a metallurgical technique that combines mechanical deformation like compression, forging or rolling with thermal processes like heat-treatment, quenching, etc. The steel rod that is freshly rolled is lessened rapidly of heat at its periphery by quenching. This creates a layer of a dense material called martensite. The rod gets compressed when it shrinks due to cooling which aligns the crystalline structure of it uniformly. This helps the rod achieve immense strength. After heat-treatment, the rod’s core persists heated, thus developing a ferrite-pearlite interior layer, causing the rod to be ductile. TMT process helps the steel rod gain its toughness and ductility, and it can be consolidated using heat restoration in the manufacturing process.

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