Manufacture and chemical composition of steel TMT Bars

MANUFACTURE AND CHEMICAL COMPOSITION

Steel shall be manufactured by the open-hearth, electric, duplex, basic-oxygen, or a combination of these processes. In case any other process is employed by the manufacturer, prior approval of the purchaser should be obtained.

• Steel shall be supplied semi-killed or killed.
• The bars/wires shall be manufactured from properly identified heats of mould cast, continuously cast steel or rolled semis.
• The steel bars/wires for concrete reinforcement shall be manufactured by the process of hot-rolling. It may be followed by a suitable method of cooling and/or cold working.

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Chemical Composition 

The ladle analysis of steel when made as per relevant parts of IS: 228 shall be as follows:

1.1

NOTE 1- For guaranteed weldability, the percentage of carbon shall be restricted to 0-25 percent, maximum.

NOTE 2- Addition of micro alloying elements is not mandatory for any of the above grades. When strengthening elements like Nb, V, B and Ti are used individually or in combination, the total contents shall not exceed 0-30 percent; in such case manufacturer shall supply the purchaser or his authorized representative a certificate stating that the total contents of the strengthening elements in the steel do not exceed the specified limit.

In case of product analysis, the permissible variation from the limits specified under 1.1 shall be as follows:

1.2

For welding of cold-worked deformed bars, the recommendations. of IS: 9417-1979 shall be followed.

In case of deviations from the specified maximum, two additional test samples shall be taken from the same batch and subjected to the test or tests in which the original sample failed. Should both additional test samples pass the test, the batch from which they were taken shall be deemed to comply with this standard. Should either of them fail," batch shall be deemed not to comply with this standard.

Rolling and Cold-Working of Bars/Wires

1) All bars/wires shall be well and cleanly rolled and shall be sound and free from surface defects and pipe, or other defects detrimen tal to its subsequent processing and to its end use. Rust, seams, surface irregularities or mill scale shall not be the cause for rejection provided a hard wire brushed test specimen fulfils all the requirements of this specification.

2) Stretching may or may not be combined with cold-working. The unworked length at each end of the bar/wire shall not exceed 100 mm or 4 times the nominal diameter, whichever is greater.