Some New Technologies for Steel Reinforcement Bars

Ministeel Plants in India are comparatively of small capacity with an average annual production capacity of 100000 TPA to 300000 TPA. The capital cost and running cost are very high for these plants because the technology available in India for converting the liquid steel to final products are still expensive.

There are many smaller plants in India with 5 to 6 T melting furnaces which can produce about 60 TPD. These are closed mainly because production costs are high and. With the proposed process here, we can make these small plants profitable.

Reinforcement bars (TMT bars) – a comparison conventional vs proposed process

Conventional process	Proposed process	Remarks
Liquid Steel	Liquid Steel	Consider the process of melting and getting the metal ready for continuous casting the same.
50000 - 60000 TPA	50000 - 60000 TPA	Consider production capacity same.
Continuous caster – 100 mm sq billets	Continuous caster – 20 mm dia rounds The casting is a double process of casting and rolling. Effective casting starts with 36 x 36 square. But the process is such that the output size is 20 mm dia round.	Cost of casting is more in conventional process mainly because of cost of mould. The saving will be about Rs. 50 per T. The 20 mm dia round has already undergone hot rolling with 4 times reduction.
Reheating in most plants , but in some new plants direct rolling without reheating is being done.	No reheating	Complete reheating cost will be saved – almost to the tune of about Rs. 2000 per T. Many plants use pulverized coke for reheating which cost them about Rs. 700 to 800 per T
Hot Rolling from 100 mm sq to 8 to 12 mm	Hot  rolling from 20 mm to 8 to 12 mm Effective hot rolling is from 36 mm sq to 8 to 12 mm round	Electrical energy saving will be about 70 kwh per T, which is about Rs. 400 per T
Since the hot billet is cut to 6 m or 3 m, each billet will have head cut and tail cut twice during rolling.	Since it is continuous endless rolling, no head or tail cut is required	Yield improves tremendously
There is scale loss in the furnace and more exposure	Practically no scale loss	Yield improves further
TMT	TMT – less water required since speed is less.

Almost 4 million units of electricity and 1.5 million litres of fuel oil per annum is saved. Plants with 5 to 6 T furnaces which are closed due to non-profitability can be restarted and made into profitable ventures. Considering the savings involved, this is definitely worth pursuing.

If more production is needed, we can have two strand or 3 strand caster and two or three strand rolling mills.

One doubt being expressed is whether we can get the qualities required by rebars or other applications, because the area reduction in hot rolling is less. But in this process, part of the rolling takes place during casting itself. As we pour the metal to the caster rolls, when the solidified section above what we call the kissing point of the rolls, is around 36 x 36, and after that to 36 x 15 oval and then to 20 mm round, it is getting rolled. So the actual reduction for a 12 mm dia rebar is 36 x 36 / 108 = 12 times and for 16mm dia rebar is 36 x 36 / 192 about 7 times. This reduction is actually enough for the bar to get the required properties. On a crude pilot machine for trials, we have already made 36 x 15 oval.

Apart from TMT bars, this process can produce plain round bars upto 16 mm dia for making bright bars.

The same machine can produce strips as thin as 3 to 6 mm, about 40 to 60 mm wide. These strips have many applications such as GI earthing strips, cable trays etc.

Further Development works

We do not intend to stop here. There is much more work that can be done. Our next plan is to develop a high reduction rolling mill stand to roll 20 mm to 6 – 16 mm dia in just one stand. Adding another finishing stand can get a finished product in just 2 stands. There are mills like the planetary mills which reduces 55 mm thick slab to 3 mm thick sheet in one stand, and if we sensibly apply this technology to rounds, it looks a real possibility.

Anybody who is interested may please contact A K Narayanan at akn@nyanzengg.com or call +91 7895623546. We have a detailed project report with all the preliminary drawings and techno economic feasibility, ready with us.