INS Vikrant’s first victory: being built from Indian steel

By Ajai Shukla

Bhilai Steel Plant, Chhattisgarh

However one dresses it up, a steel plant is not a pretty place. A blast of heat hits us as we enter the gigantic shed that houses Bhilai Steel Plant’s largest blast furnace, which converts ore into pig iron. Our eyes still attuned to the bright Chhattisgarh sunlight outside, we peer into a smoky version of what can only be described as Dante’s inferno. Amidst the deafening hiss of steam-operated machinery, a gleaming rivulet of molten pig iron flows past us and into an enormous ladle. Sparks dance up from the molten metal, iron particles that are literally aflame. Another glowing rivulet of slag, the waste material left after ore becomes iron, flows away into a murky darkness. Suddenly, sheets of flame shoot out of the base of the furnace as helmeted steelworkers “tap” the melt.

In this hellish battleground, defence indigenisation has won a significant victory. Bhilai Steel Plant and its sister plants of the Steel Authority of India (SAIL) --- at Rourkela, Durgapur and Bokaro --- have manufactured 26,000 tonnes of high-grade “warship steel” that has gone into INS Vikrant, India’s first indigenous aircraft carrier that will be launched into water at Cochin Shipyard on Monday.

Simultaneously, SAIL supplied steel for four corvettes that Garden Reach Shipbuilders and Engineers, Kolkata, is building under Project 28. And Essar Steel is providing steel for four destroyers that Mazagon Dock, Mumbai is building under the Indian Navy’s Project 15B.

“Warship steel” is a challenging specialty metal. It must be hard and also tough, just as a champion gymnast must be strong as well as flexible. It must remain so at temperatures of minus 60 degree Celsius, when normal metal plates shatter easily. In its maritime working environment, it must resist endless corrosion from seawater and air.

Small wonder then that India has long relied on Russia, Poland, the UK and others for steel for its warships. But that created two major problems: firstly, warship production was often delayed due to the whims of steel suppliers. And secondly, multiple sourcing, with multiple specifications, created logistical problems over the four-decade service life of a warship, with a multitude of different spare plates and welding consumables required, often in tiny quantities, sometimes from sources that had shut down.

Says Commodore Saibal Sen, who is overseeing the construction of INS Vikrant, “Developing our own warship steel was a technological imperative”.

And so the Defence R&D Organisation (DRDO) took up a project in 1999 to develop and mass-produce warship grade steel. Russia provided the chemical formula of warship steel called ABA, but the challenge in steelmaking is to translate science into manufacture.

There was little time to lose. The 37,500 tonne INS Vikrant needed to start construction but awaited confirmation that indigenous steel could be supplied. Also in the pipeline were a series of warships --- four 2,500-tonne corvettes of Project 28; four 6,800-tonne destroyers of Project 15B; and seven 4,900-tonne frigates of Project 17A.

The Defence Metallurgical Research Laboratory (DMRL), a part of DRDO, began working with SAIL, finding a way to produce warship steel cheaply in quantities that ran into tens of thousands of tonnes. Rourkela Steel Plant found that “tempering and quenching” --- which involves heating steel to red heat and then plunging it into water --- gave the required grain structure, but would cost too much. And then came the breakthrough: Bhilai Steel Plant developed a “continuous casting” process and warship grade steel was now affordable. In 2004, Cochin Shipyard was given the green signal and INS Vikrant started taking shape.

Says SAIL chairperson, CS Verma: “Our steel costs twice as much as normal steel, but is still half the cost of imported warship steel. As volumes increase, and our production techniques are refined, we hope the cost will come down.”

Today, Bhilai Steel Plant casts warship steel plates of up to 20 millimetres thickness without quenching or tempering, supplying the bulk of the requirement for large warships. But thicker steel plates are also required, albeit in smaller quantities. That is done at the Special Plate Plant (SPP) in Rourkela, which produces plates up to 120 millimetre thick through quenching and tempering.

Special Plate Plant, Rourkela is emerging as a major special steels centre for defence equipment. It produces armoured plate for the T-90 and Arjun tanks, and the BMP-II infantry combat vehicle, which are built at Avadi and Medak respectively by the Ordnance Factory Board. Its annual capacity of 2,000 tonnes is being upped to 12,000 tonnes.

“(The DRDO’s) research project worth about Rs 14.2 crore has now led to the supply of steel worth about Rs 550 crore,” points out Dr G Malkondaiah, former DMRL Director who oversaw this project closely.

Being used on the INS Vikrant are three special steels --- DMR 249A for the hull and body; and DMR 249B, a more resilient steel, which is used for the flight deck that must take the repeated impact of 20-30 tonne fighter aircraft landing. In 2008, DMR Z25 was developed for the floor of compartments that housed heavy equipment like engines and generators. This absorbs the compression and decompression from the heavy equipment.

In the pipeline now is DMR 292A, which will be used for the hull of submarines. This could be used in six conventional submarines that will be built under Project 75I, and in India’s entire fleet of nuclear submarines.