Outokumpu Oyj

Eka Chemicals Ab

Avestapolarit Aktiebolag (publ)

Sven-Eric Lunner

Arne Frestad

Troy Berglind

Ye Guozhu

Charlotte Angel

Anders Waleij

Fredrik Hägg

The invention relates to a method in connection with steel production for handling of hydroxide sludge formed in the neutralization of spent metal-contaminated pickling agents from a pickling step for steel, preferably stainless steel and for using calcium fluoride in the hydroxide sludge to replace the natural fluorspar as a fluxing agent in connection with steel production. Accordingly, the addition of the reactive neutralization medium is monitored by the pH electrodes operated in continuous fashion, and the pH value is adjusted at the range between 9.0 and 9.5.

Method in connection with steel production

A method of producing a fluxing agent that can be used in production of steel, preferably stainless steel, employs as a raw material a hydroxide sludge that results from neutralization of metal-contaminated pickling liquid from a pickling step for a steel and contains at least one fluoride-containing compound. The hydroxide sludge is calcined. Steel, preferably stainless steel, is produced by decarburizing a steel heat, whereby a slag is formed on top of the steel heat, and adding a fluxing agent to the slag.

A long-time stable pickling agent for the removal of an oxide layer on a stainless steel after heat treatment, such as welding, which pickling agent comprises nitric acid and fillers and constitutes of a pickling paste or pickling gel to be coated on the heat treated stainless steel, or of a pickling liquid to be sprayed on the steel. According to the invention, the pickling agent also comprises urea for reduced formation of nitrous fumes when the pickling agent is used.

Pickling agent containing urea and method of producing it

The invention relates to a method at pickling of steel in an acidic aqueous pickling solution containing Fe,and Fe,, wherein the steel is contacted with pickling solution that continuously is brought to circulate through a conduit into which hydrogen peroxide is supplied to oxidize Fe,to Fe,.

Method at treatment of metals

The invention relates to a method for pickling steel in an acidic aqueous pickling solution containing Fe.sup.3+ and Fe.sup.2+, wherein the steel is contacted with pickling solution that continuously is brought to circulate through a conduit into which hydrogen peroxide is supplied to oxidize Fe.sup.2+ to Fe.sup.3+.

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Avesta, Sweden

Sven-Eric Lunner