Steel wire
transformation
processes

THE STEEL WIRE MANUFACTURING PROCESS IS AN ARDUOUS JOURNEY, ESPECIALLY ALL THE WORK THAT GOES INTO IT.

We wish to highlight six of the different types of steel wire transformation process to give you an overall understanding.

Acid cleaning and steel coating

Scale is removed using hydrochloric or sulfuric acid cleaning using four cascading tanks. By automating the cleaning process, tank residence times and concentration ensure greater product consistency. Once the wire has been cleaned, it is rinsed, then coated.

A coating is chosen based on the requirements of the process or the product. Among the coatings available are zinc phosphate, lime, lube, and borax. The coating can be applied within the production process and at the end (coating at finish).

Annealing

Sivaco performs spheroidize annealing which consists of softening the steel by heating it to subcritical temperature levels and holding it until it transforms from a lamella (pearlite) structure to a matrix containing cementite spheroids. The steel is then slowly lowered in temperature to maintain the newly acquired microstructure. The ductility attained with this structure allows the steel to be cold headed or stamped.

Annealing practices have been developed for a variety of steel alloy grades, boron steels, and high carbon steels (with a carbon content above .45%). Mechanical properties are emphasized according to ASTM F2282, and inert and rich carbon atmospheres are used to prevent decarburization during the treatment. For certain practices, bright and black surface finishes are available.

Drawing

Wire drawing is a cold deformation operation that involves pulling steel through a die to create a new cross-sectional area. Depending on how much cold working is done, the mechanical properties of the material will vary. Wire drawing equipment at Sivaco uses dry soaps and has a great variety of equipment allowing for greater product diversity.

A machine's selection will be determined based on the mechanical properties, the final wire size, as well as the raw material used. Wire sizes range from .039" to .725", and can be used for low, high, and alloy carbon steels.

Depending on the coating used on the pickling line, some products can have a plating finish (very little residue, brilliant appearance). A smooth surface and tighter diameter tolerance can also be achieved by drawing material after galvanizing.

Galvanizing

Galvanizing is the steel wire transformation process of coating steel wire with zinc to prevent corrosion. Corrosion resistance will occur through 1) zinc being a physical barrier between the environment and the steel and 2) cathodic protection, where zinc acts as a sacrificial anode for steel.

Prior to the hot dip zinc coating process, the steel could undergo thermal treatment before acid cleaning. Achieving greater flexibility in mechanical properties (soft, medium, and hard temper). Then, within the hot dip process, an intermetallic layer of Fe/Zn is formed creating a strong metallurgical bond between steel and zinc. Afterward, forming lubricity and corrosion protection can be provided by coating the wire with a water-soluble wax.

Sivaco offers two coating processes, one of which can provide a zinc coating with 1.2 ounces of coating per square foot, and the other of which can provide 0.15 ounces per square foot. Zinc coated wires are produced by both processes in accordance with ASTM A641. In addition, a Galfan coating is available which offers three times more corrosion protection. Galfan is a zinc and aluminum alloy containing mishmetals that complies with ASTM B750.

Patenting

The patenting process involves a high temperature treatment, which produces a uniform austenite phase in steel. The wire is then cooled in a liquid medium to obtain a fine pearlite microstructure. Parameters are controlled for high carbon grades that do not contain alloys.

By patenting the rod, the cooled Stelmor® microstructure will be strengthened and become more ductile. The result is a longer cycle life. Also, patenting can be used after drawing (patented in steel wire transformation process) to further produce smaller wire diameters that have specific mechanical properties. The process complies with ASTM A228 Type 2, JIS G3521, JIS 3522, EN 10270-1, and DIN 17223.

Spooling

Through our operation, wire can be transferred from carrier or stem to spool, or between spools. Throughout the winding process, care is taken to wind evenly and with consistent tension. With this equipment, steel, wood, or cardboard spools can be handled with bore sizes ranging from 1" to 5".

Typical spooled wire weights range from 500 to 4000 lbs, and wire sizes range from .039" to .225". Spooling operations are sometimes performed in line with our drawing equipment.

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