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Cold rolled ribbed steel bar is made of hot rolled wire rod by multichannel cold-rolled, reducing a rib rolling and after stress relief form of a steel bar with two or three surface crescent. Cold rolled ribbed steel bar is the upgrading production of cold drawn low carbon steel wire in prestressed concrete members. In cast-in-situ concrete structure, steel can be instead ofⅠgrade steel bar, in order to save steel, is better one in the same kind of cold rolled steel。
Cold-rolled ribbed steel grades by the CRB and reinforced the tensile strength of the minimum. C、R 、B, respectively (cold - rolled), cold-rolled ribbed (ribbed), steel bar (bars) three words of the first letter in English.CRB550, CRB650, cold rolled ribbed bar CRB800, CRB970 and CRB1170 five grades.CRB550 for ordinary reinforced concrete with steel.
Cold rolled ribbed bar has the following advantages.
1. high strength steel, It can save material and reduce the project cost.CRB550 compared with hot rolled round steel bar, used for cast-in-place structure (especially the floor roof) can save 35%-40% steel. Such as considering no hook, steel more savings. According to the steel market price, using a ton of cold rolled ribbed steel bar, can cut down the cost of steel 800 RMB.
2. cold-rolled ribbed steel bar the bond anchorage between reinforcement and concrete performance is good. Used in components, therefore, fundamentally eliminate the anchorage zone of cracking, steel wire slip and failure phenomenon, and improves the end bearing capacity and crack resistance of the component; In reinforced concrete structure, the crack width is better than round bar, even smaller than hot rolling thread steel.
3. Elongation than the same kind of cold steel cold rolled ribbed bar.
3.1 Steel Bar Grade and Chemical Composition
Wire Rod Size and Chemical Composition for Cold Rolled Ribbed Steel Bar
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Steel Bar Grade
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Wire rod Grade
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Chemical Composition (quality score)/%
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C
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Si
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Mn
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V、Ti
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S
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P
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CRB550
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Q215
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0.09~0.15
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≤0.30
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0.25~0.55
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-
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≤0.050
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≤0.045
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Q215
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0.14~0.22
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≤0.30
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0.25~0.55
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-
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≤0.050
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≤0.045
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2. Dynam Capability and Technic Capability for cold rolled ribbed steel bar
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Grade
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Rpo.2/Mpa
≥
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Rm/Mpa≥
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Tensility /％≥
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Bend Test 180。
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Bend Times
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The stress relaxation
initial value should be equivalent to 70% of the engineering tensile strength
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A 11.3
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A100
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1000h Relaxation /％≥
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CRB550
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500
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550
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8
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―
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D=3d
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―
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―
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Note: 1. In the table D for bending diameter, d for reinforced nominal diameter.
2. Steel bar by cold working status of delivery. Allow low temperature tempering treatment after cold rolling.
3.When to bend test, the bending parts surface shall not crack. Bending radius of repeated bending test: reinforced nominal diameter 4 mm, 5 mm, 6 mm, the bending radius 10 mm, 15 mm, 15 mm.
4. The strength of the reinforced than Rm/Rpo. 2 ratios should be 1.03 or higher. The supply and demand both sides agreement use Agt≥2.0％ available instead of A.
5. The supplier on the basis of guarantee 1000 h relaxation rate of qualified, allowed to use the method of determine 1000 h relaxation.
6. CRB550 reinforced nominal diameter in the range of 4 ~ 12 mm. CRB550 and above brand of nominal diameter 4 mm, 5 mm, 6 mm.
2. Dynam Capability and Technic Capability for cold rolled ribbed steel bar
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