Improving the technology for preparing a wire rod for drawing

Abstract

The quality of wire is determined to a considerable extent by how efficient the technological operation of preparing the metal for drawing is. Traditionally, the preparation of the surface of wire rods includes acid pickling, washing, and application of a lubricant carrier coating. The customarily used three-cascade counterflow washing after hydrochloric acid pickling does not ensure complete removal of the acid and iron salts from the surface of the metal [1]. Entry of the acid into the tanks for borax treatment and liming results in accumulation of chloride ions in the solution and on the surface of the metal, which activate pit corrosion. In the steel wire shop of the West Siberian ISW, a technology was implemented for preparing the surface of wire rods by neutralization and passivation in solutions of hydrolyzing salts with surfactant properties before applying a lubricant carrier coating. Before borax treatment, the rods were treated in a solution of a passivating salt that hydrolyzes in an aqueous solution. The alkaline medium of the solution neutralizes traces of the hydrochloric acid. The salt film remaining on the surface temporarily protects the metal from atmospheric corrosion between operations. Owing to its porosity, the salt sublayer retains the borax (lubricant carrier) very well. To obtain a structure of the borax pentahydrate that is optimum for drawing, the rods were heated to 100 180~ before borax treatment. A laminar precipitate appeared on the metal surface in the form of an amorphous (iron hydroxide) and crystalline salt phase having good adhesion to borax and to a soap-based lubricant. Before liming, the rods were treated in an alkaline solution containing anion-active surfactants.