A Sustainable Technology to Produce Green and Clean Steel by Hydrogen Plasma Smelting Reduction

Pravas Behera, Priyanka Rajput, Bhagyadhar Bhoi — Mon, 28 Mar 2022 16:22:29 +0530

It is now widely acknowledged by the world that reduction in emissions of CO₂ gas to control global warming is of paramount importance. The CO₂ gas accumulated in the atmosphere absorbs and retains heat in the infrared range. One ppm of CO₂ concentration is equivalent to an addition to the atmosphere of approximately 7.8 GtCO₂ (Giga tons of carbon dioxide). The proposed draft of the National Steel Policy has forecast the country’s steel-making capacity in the range of 244-281 million tons (MT) per annum by 2025. About 770 kg of coal is required to produce 1 ton of steel and therefore, it would require about 200 MT of coal to meet the target production by 2025. In the conventional process, 2.7 tons of CO₂ gas is generated per ton of crude steel production. These are staggering numbers, which call for the need to develop innovative and alternate method of steelmaking to replace the conventional method.

CSIR-IMMT, Bhubaneswar has developed a Hydrogen Plasma Smelting Reduction process in the laboratory scale to produce steel that completely eliminates CO₂ gas emission. It uses hydrogen gas as the source of heat energy to smelt iron ore in place of coke or coal that are used conventionally. Simultaneously, hydrogen is being looked upon as the future energy fuel that can be generated from water by using solar energy. The optimized laboratory scale parameters (hydrogen flow rate, argon flow rate, hydrogen volume, reduction time, feed rate and quantity) were replicated successfully in bench scale (10 kg) with the product obtained of 99.54% pure iron with negligible sulphur and phosphorous content.

Effect of Si Content on Phase Transition Temperature, Microstructure and Hardness in Medium Mn Steel

Mon, 28 Mar 2022 16:24:01 +0530

Medium Mn steels (C = 0.15–0.19 wt.%, Mn = 5.00–5.20 wt.%) with variation of Si content (1.9, 2.45, 3.4 wt.%) were prepared using vacuum induction melting furnace. The cast billets were forged and cooled to room temperature in air. Microstructural investigation of the forged alloys showed fully martensitic structure along with minor content of retained austenite. With Si content, the hardness of forged steel were found to be increasing. The transition temperatures (A_c1, A_c3, M_s, and M_f) were determined using differential scanning calorimetry (DSC) measurements. Increase of Si content raised A_c1 and A_c3and caused reduction in M_sand M_f. The forged samples were austenized at 900 °C for 15 min, followed by isothermal holding at 700 °C for 1 and 4 h and water quenched. The microstructure consisted of ferrite, martensite, and retained austenite. Microhardness measurements of heat-treated steels also showed significant enhancement of mechanical strength with increase of Si content.

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A Sustainable Technology to Produce Green and Clean Steel by Hydrogen Plasma Smelting Reduction

Effect of Si Content on Phase Transition Temperature, Microstructure and Hardness in Medium Mn Steel