The combined company, to be named RHI Magnesita, will be established in the Netherlands and listed in London, with RHI ceasing its listing in Vienna.
The Brazilian steel producer said the hike reflects higher international prices and stronger demand for flat steel products abroad.
The operation, in the southeastern state of Espírito Santo, is expected to reach 8,000t/m by the end of a 12-month period, according to the state's official news service reported.
Improved mineral commodities prices, especially for iron ore, was the main reason for the growth, official data shows.
The move comes after the dismissal of 22 workers from the Brazilian steelmaker's Divinópolis plant.
The Asian powerhouse also managed to lower coal capacity by 6.59Mt, and reorganized coal plants with capacity totaling 13Mt over 1H17.
Exports of copper, gold, silver, zinc, lead, tin and molybdenum all rose in May as miners sought to take advantage of stronger metals prices.
Shipments of rolled iron and steel products, and mineral fertilizers, performed well in the first six months of the year.