In 1910 Hugh Tiemann wrote the following concise description of the manufacture of steel wire. The boldface emphases are his.
Wire.--- This is the name given to small metal filaments (usually round) produced in pieces of considerable length by drawing, i.e., successively reducing (and thereby extending) the section by repeatedly pulling it cold (cold drawing) through tapered holes in a die or draw plate (block, die plate). Drawing is necessary as it is impracticable to roll such small sections commercially.
Billets are first reduced, in a rolling mill, to wire rods (rounds) about 0.2″ to 0.3″ in diameter, which are coiled up into bundles. These bundles are placed in a pickling bath of dilute sulphuric acid, heated by steam, to remove the scale, and are then transferred to the rinsing bath to remove the greater part of the acid, after which they are put on a revolving frame and sprayed with water to still further remove the acid; this causes a certain amount of rust to form on the surface, which acts later as a slight lubricant and is known as a rust coating or water coating. The last traces of acid are eliminated by treatment in the lime bath (liming), after which the bundles are dried (baked) at a low temperature in a furnace called the baker. If the wire is to be bright finished (i.e., unannealed), it is transferred from the rinsing bath immediately to the lime bath.
The draw plate is a piece of hard (high carbon) steel (more rarely cast iron) containing a number of holes through which the wire is drawn. Usually all those in one plate are of the same size and the wire is passed through successive plates, each hole serving for one (sometimes two) bundles. After use the plates are annealed (as the metal around the holes has been hardened), the holes reduced by hammering and then opened up to the exact size by punching (pricking). The plates used for the first few reductions are sometimes referred to as the roughing blocks, nipping blocks, or nippers; those for the last, as finishing blocks.
Drawing is performed on the draw bench, which comprises the draw plate and a
power reel for pulling the wire through. To start the wire through the
hole, it must be pointed either with a small hammer, or by a pair of small
rollers with grooves of different sizes, given a rocking movement (like an
alligator shears) by an eccentric. The wire is then pulled through by a
pair of tongs (grippers or nippers) attached to a crank shaft, giving a
reciprocating (back and forth) movement, until there is a sufficient length to
attach it to the power reel. The term ratch is used for the
pull of the wire through the die at one operation where a straight pull and not
a reel is used. The plate is sometimes tilted backward at a slight angle
to kill the wire, i.e., prevent the tendency to spring out into an unmanageably
large coil on removal from the reel. To reduce the friction in drawing,
the wire must be coated with some substance which acts as a lubricant. In dry
drawing, grease is employed: it is piled against the back of the draw plate
around the hole, and one application serves for a number of reductions. In
wet drawing, the wire is given a lees coating by passing it through lees liquor
composed of water and some kind of flour, sometimes fermented and sometimes
mixed with milk of lime. A copper coating (lacquer) is obtained by
treating the wire with a weak acidulated solution of copper sulphate, and then
usually passing it through lees liquor before drawing. After this treatment it
is known as lacquered, straw-tinted, or coppered wire; this method is sometimes
called the liquor-bright process. If the finished wire is to be
coppered, it must receive an additional treatment.
Multiple drawing is where the wire is drawn through a number of dies simultaneously, being reeled up only after passing through the last, instead of after each plate. In this case, to avoid breaking, it is necessary to provide a power reel between each pair of holes, around which the wire is given a couple of turns. Passing the wire through the various dies and around the reels is called stringing up. After about 8 to 10 holes (hole in this sense means pass or reduction) the wire is so much hardened that it must be reannealed, etc., before drawing can be continued. This fine wire is sometimes batted, i.e., beaten with wooden sticks while being washed after pickling.
Plain drawn wire (bench hardened wire) is wire in the condition in which it leaves the last hole, without any further treatment.; Plain annealed wire is where it is annealed in closed iron pots to render it soft and pliable. Galvanized wire is annealed and then coated with zinc (spelter). In galvanizing, the wire is passed (a) through a lead bath to anneal it; (b) through a weak pickling solution to remove the scale formed; (c) through a rinsing bath; and (d) through the molten spelter contained in the galvanizing pan. The excess of zinc is removed by drawing it through plugs of asbestos, called wipers. The wire is kept below the surface of the zinc by passing it under heavy toothed bars called sinkers. In modern practice a number of wires or strands are treated simultaneously, the whole series of operations being continuous, and one power reel serving to pull each strand through (Bedson's continuous galvanizing process). Attempts have been made to produce bright annealed wire by annealing in a reducing atmosphere so no oxide or scale will be formed. Tinman's wire is a soft bright-drawn wire used in the manufacture of various tin plate goods. Improved steel wire or patented steel wire, after finishing in the usual manner, is heated in a muffle, quenched in oil, and tempered in molten lead. Plow steel wire is made from a fine grade of high-carbon, crucible steel, and is so called because it was originally used for dragging steam plows. Gun screw wire is a name sometimes employed for wire made from a high grade of refined wrought iron. B. B. wire, E. B. B. wire, or four-sided charcoal wire were grades in England, used for telegraphic work, made of fagots composed of puddled billets in the center, and four flats outside, of (a) best, best puddled iron (b) or top and bottom of charcoal iron with sides of best, best puddled iron, or (c) charcoal iron all around, respectively. Instead of cleaning wire with acid, it is sometimes put into a scouring barrel, in which it is rotated with some cleaning material.
Hugh P. Tiemann.
Iron and Steel. A Pocket Encyclopedia.
New York: McGraw-Hill Book Company, 1910.
Copyright © 2001 Sizes, Inc. All rights reserved.
Last revised: 10 August 2001.