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CQ vs BS/SIRIM Steel Bars

posted Sep 6, 2021, 7:47 AM by jeffery jim
CQ or Commercial Quality produced mild steel and and high tensile steel with similar size grading. Both are certified steel bars for industrial purposes, where CQ are based on ISO standard H8 which has higher industrial tolerance as shown below. Unlike CQ, BS or SIRIM uses have better tolerance range compare to CQ. A CQ bar is allowed to deviated for more than 10% which for mass deviation for SIRIM steel bars is under 4.5% for steel larger than 8mm.

The code for local steel with SIRIM accreditation usually start with 1X9 or now X9 is a good way to recognize these bars when come in bundles apart from the mill certificate. The last three digit marks the manufacturer of the steel locally.

The advantages of SIRIM rebars would be the high tensile strength and within range yield strength. Just so you know, MS146 sets a limit of 460 to 650 for yield strength in order to ensure ductility apart from bend and rebend test. Else, ratio of tensile strength/yield strength and elongation ratio will be useful in quality control and conformance.

Although BS or SIRIM reinforcement bars is much superior, there are also cases of noncompliance. One needs to have trained skills to detect good and defective bars. CQ bars? I will try to avoid it as much as I can for building construction.

Nevertheless, please understand at times, some local steel mills import CQ because they need to fabricate other steel-related products.

ADDENDUM:
CQ tensile strength is 340 MPa, BS is usually 550MPa or >500Mpa. Yield strength of CQ is half of BS.
This made CQ easier to bend and bad for engineering.

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