As the smelting stage is necessary to obtain alloys and shape the product, direct reduction processes are frequently combined with downstream smelting facilities.
Most pre-reduced iron ore is smelted in electric furnaces: in 2003, 49 of the 50 Mt produced went into electric furnaces. Process integration is generally highly advanced, to take advantage of the high temperature (over 600 °C) of the prereduct from the direct reduction reactor.
One idea is to carry out the entire reduction-melting process in the arc furnace installed downstream of the reduction plant. Several plasma processes operating above 1530 °C have been devised and sometimes tested. Furnaces can be either non-transferred arc (Plasmasmelt, Plasmared) or transferred arc (ELRED, EPP, SSP, The Toronto System, falling plasma film reactor). All these processes share the electric furnace's advantage of low investment cost, and its disadvantage of using an expensive energy source. In the case of direct reduction, this disadvantage is outweighed by the fact that a great deal of heat is required, both for the reduction process and because of the gangue to be melted.
An alternative to the electric furnace is to melt the pre-reduction with a fuel. The cupola furnace is ideally suited to this task, but since one reason for the existence of direct reduction processes is the non-use of coke, other melting furnaces have emerged. The COREX process, in operation since 1987, consists of a direct-reduction shaft reactor feeding a blast furnace crucible, in which the pre-reduced ore is brought to a liquid smelting state, consuming only coal. This process also produces a hot reducing gas, which can be valorized in a Midrex-type unit. An equivalent to COREX, based on the FINMET fluidized bed instead of the Midrex vessel, is the Korean FINEX process (a contraction of FINMET and COREX). Both processes are in industrial operation at several plants around the world.
Last but not least, a number of reduction-melting furnaces in the same reactor have been studied, but have not yet led to industrial development. For example, the ISARNA process and its derivative HISARNA (a combination of the ISARNA and HISMELT processes), is a cyclonic reactor that performs melting before reduction. These processes have culminated in an industrial demonstrator tested in the Netherlands since 2011. Similarly, Japanese steelmakers joined forces in the 1990s to develop the DIOS process which, like many reduction-fusion processes, is similar to oxygen converters. The TECNORED process, studied in Brazil, also performs reduction-melting in the same vessel, but is more akin to a blast furnace modified to adapt to any type of solid fuel. Of all the processes of this type that have been developed, a single ISASMELT-type industrial unit built in Australia, with a capacity of 0.8 Mt/year, operated from 2005 to 2008 before being dismantled and shipped to China, where it was restarted in 2016.