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Unique features of BSRM Xtreme bars:

1. High design yield strength of 500 Mpa (72500psi) (Min)
2. Requires 15% less steel in construction compared to Grade 60 rebars available in the market.
3. The bars have superior bendability and can be safely bent without cracking.
4. All bar sizes are rolled to a very close tolerance (possible on a DANIELIcomputerized rolling mill) so that customers get more meters of steel per ton - more value for money without having to sacrifice structural integrity. Estimated savings: 0.5%.
5. De-scaled bars have better bonding with concrete and less wastage at site. Estimated savings : 0.5%
6. Xtreme bars are safely weldable under field conditions.Another 0.5% to 1.5% of steel is saved by avoiding large splices.
7. The bars are needle-straight, thanks to the Danieli QTB process - no need for straighteningon the construction site.

Quality Assurance Report

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Product Information

Typical Mechanical Properties:
Yield Strength: 500 mpa (min) [72,500 psi]
Ultimate Tensile Strength: 575 mpa (min) [83,375 psi]
Elongation A 5 [%]: 14% (min)



REFERENCED STANDARDS
Mechanical Properties


Code

Yield Strength or 0.2% Proof Stress
Mpa( Min)

Tensile Strength
Mpa (Min )

Elongation % on        5D G.L
(Min)

Elongation At Maximum Force
(Min )

Bending Pin Dia
(mm)

Re-bend Pin Dia
(mm )

ISO 6935

500

575

14%

7%

(3D-7D)

(5D-10D)

BDS-ISO 6935

500

575

14%

7%

(3D-7D)

(5D-10D)

BS 4449 Gr.B500 C

500-650

15% more than Y.S

--------

7.5%

---------

(4D-7D)

JIS G 3112 SD 390

390-510

560

16%

--------

2.5D

--------

DIN 488 Bst 500

500

550

10% on D 10

 

5D to 8D

 



THE PROCESS
Equipment of the Water Box


The above schematic illustrates the exclusive DANIELI QTB process which converts low carbon steel into high strength bars with a guaranteed yield strength of 500 mpa. In Bangladesh, BSRM is the first company to procure and implement this technology commercially and successfully.


Mechanical Graph


High strength, ductility and weldabilty together was an almost impossible combination - a civil engineer’s dream, and a steel metallurgist’s nightmare. The unique heat treatment technology in the DANIELI QTB process makes this possible. BSRM rebars have typically high strengths, shown in the stress-strain graph above, yet retain the modulus of plain carbon steel, 210 Gpa [29,000,000 psi].

The Danieli, Italy QTB process at BSRM Steels Ltd.



How the QTB process works




BSRM Xtreme rebars are hot-rolled from prime quality steel billets and subjected to on-line thermo-mechanical treatment in three successive stages.

(a) Quenching: The hot rolled bar leaving the final mill stand is rapidly quenched by high pressure water in special venturi tubes. This hardens the surface of the bar to a depth optimized for each section through formation of martensitic rim, while the core remains hot and austenitic.

(b) Self Tempering: As the bar leaves the quenching venturi tube the core remains hot compared to the surface, allowing heat to flow from the core to the surface which causes tempering of the outer martensitic layer into a structure called Tempered Martensite. The core still remains austenitic at this stage.

(c) Atmospheric cooling: This takes place on the cooling bed, where the austenitic core is transformed into a ductile ferrite-pearlite structure. Thus the final structure consists of an optimum combination of strong outer layer (tempered martensite) with a ductile core (ferrite-pearlite). This gives BSRM Xtreme bars a unique combination of high strength and ductility.


A close-up view of the dual phase rebar made by BSRM Steels Ltd - a hard outer shell of tempered martensite and an inner core of very tough and ductile ferrite-pearlite core. This unique technology at BSRM enables very high strength in the reinforcing bar without sacrificing ductility and weldability. 


WELDING GUIDE

BSRM Xtreme 500W is weldable under field conditions with any marine grade all position electrodes. Special low hydrogen electrodes are recommended for welding in wet weather conditions.

1. Smaller diameter bars can be strap-welded, as shown in the illustration.
2. Column and beam bars can be efficiently lap-welded at reduced lapping lengths, as shown in the diagram.


Procedures for Specific Weld Types 
Electrode Type: Under-matching strength electrodes are preferred, but matching strength may be used.

Weld Length: This should not be less than the size of the smaller bar.

General Notes: These are usually used for positioning and holding purposes, and in prefabricated elements.They must not be used for lifting purposes unless prior approval has been obtained from the design engineer. They do not affect the strength of Grade 500. 
Electrode Type: Matching and under-matching strength electrodes may be used.

Weld Length: Minimum total weld length is 5d.

General Notes: The short length of conventional double sided lap splice welds may cause excessive rotation at the splice when loaded in tension, and thus contributes to concrete spalling. Longer weld lengths than that required to develop full strength have therefore been recommended. This tendency to rotate can be further minimised by forming the weld in two parts as shown, thus increasing the effective geometric length. In this case, the gap between lap welds should not exceed the total weld length.  
Electrode Type: Matching and under-matching strength electrodes may be used.

Weld Lengths: • Matching strength electrodes: 8d • Under-matching W50x (E48xx) type electrodes: 9d • Under-matching W41x (E41xx) type electrodes: 10d

General Notes: Single sided lap welds, because of their greater length, have less tendency to rotate, but should only be used with the permission of the supervising engineer when access to the second side is not available or impractical. These welds may also be formed in two parts as shown, provided total weld lengths noted above are used.  
Electrode Type: Matching and under-matching strength electrodes may be used.

Weld Lengths: • Welded one side: 5d for each individual weld • Welded both sides: 3d for each individual weld

General Notes: Full parent bar properties are generated by strap welds. The total cross sectional area of the splice bars must not be less than the cross sectional area of the parent bar. The gap between parent bars must not exceed 20mm. Strap welds may be welded either on only one side or both sides, noting minimum effective weld lengths above. Strap welds are bulkier than lap or butt splice joints, thus they may not be suitable for use in applications where concrete cover is minimal. Where doubt exists, verify suitability with the supervising engineer.  
Electrode Type: Matching strength electrodes are essential to develop full strength in the butt weld.

General Notes: Observe 200 C maximum interpass temperature by allowing weld to cool between runs, particularly towards end of welding.  


THE STEEL REVOLUTION STARTS HERE
Towering skyscrapers
Soaring flyovers
Mighty bridges
All made possible, with the power of BSRM Xtreme
-the next generation steel
 
 
 
   
 

   

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