Cleaning - Single Wire

In line high-speed single-wire cleaning system in which compact equipment operates in front of and in-line with a wire drawing machine. The operation is based on either a hot water process or electrolytic pickling, and can handle sizes ranging from rolled wire rod to fine-gauge wire. The plant is available in a standard version, but with a multitude of variants. Typical applications include cleaning of cable wire, stainless steel wire, CO2 welding wire, wire of various copper alloys, and cleaning before drawing.

Candojet patented single-wire cleaning system
Courtesy of Outokumpu WTT AB

Cleaning - Multi-Wire

While batch cleaning lines are still widely used modern wire cleaning lines are continuous and can be supplied either as standard units or as customized systems. The plants have several parallel wire tracks and is based on either bipolar electrolytic cleaning or ultrasonic cleaning, or combinations of these two methods. The system is suitable for both degreasing (alkaline cleaning) and pickling (acidic cleaning). Typical applications include cleaning before annealing, hot-dip tin plating, and hot-dip galvanizing.

Chemical (caustic and acid) cleaning.

Prior to plating the wire surface needs to be cleaned and lubricant residue removed from the surface. A clean wire surface is imperative to obtain good adhesion to the wire surface of the plating metal. Batch cleaning lines are still widely in use but continuous single and multistrand process lines is the widely accepted state of the art for wire cleaning be it a chemical, electrolytic ultrasound or aggitated process. The Q.E.D. Multiple Stage High Turbulence™ Pickling System is a patented state of the art high speed wire cleaning process. With tanks constructed of composite materials and using advanced fluid flow technology, the design guarantees reliability and efficient pickling within a minimum length. This environmentally friendly system is a totally enclosed design that prevents acid fume escape.

Features Highly Turbulent acid flow Multiple stage cleaning Straight through wire path Double water curtain sealing Three stage cascading rinse Threading & Wiping Systems Self draining acid trays Low maintenance design Rugged construction

HighTurbulence™ - Exceptional Cleaning at High Wire speeds!

The High Turbulence™ acid section represents the latest development in acid cleaning technology. The carefully designed flow patterns effectively break down the boundary layer pocket of spent acid adjacent to the wires, thus continuously supplying fresh acid to their surface. Pickling speed is further increased by the effective scrubbing action of the turbulent acid flow. In keeping with today’s energy conservation concerns the acid section is designed in a series of modular stages, with each section having a separate optimally sized corrosion resistant pump, turbulence tray and re-circulating loop. The multiple stage design allows for lower acid consumption, by the efficient "stepping" of acid concentration levels. The modular system also ensures a lower spare parts inventory cost and eliminates the need of costly back-up pumps. The system can be operated at temperatures of up to 85 0C (185 0F) with a maximum of 20% HCl acid concentration. The two entrance curtains and two rinse curtains are supplied with re-circulated water through special corrosion resistant pumps. The smooth laminar flow curtains effectively seal in the acid fumes and flood the rinse trays. The final rinse is accomplished by high pressure water spray.

Optional Features Acid Heat-Exchanger Quick lift-off hood Temperature control system Cooling Tower Computer interface package

All pictures on this page courtesy of Q.E.D.

Rod cleaning and preparation prior to drawing

That there are many ways to skin a cat is certainly true when it comes to removal of mill scale and surface oxide.The scale is the Fe3o4 blue oxide that forms on the wire as it cools following the rolling process.

Fe2O3 is the red surface oxide or rust that forms during shipping and storage.

Both oxides need to be removed prior to drawing.

You can do this by 4 basically different methods.

• Acid pickling

• Mechanical de-scaling

• Abrasive Blasting or Sanding

• Shaving.

Acid pickling in turn can be divided up in 2 major sub methods

1. Chemical acid pickling

and

2. Electrolytic pickling

Conventional chemical acid pickling is done by submerging the rod bundles in sulfuric or hydrochloric acid.

The iron ions will then go into solution as hydrogen gas is formed on the steel surface "blasting" off the iron oxide.

Following the acid dip, the rod bundle is submerged in a rinse water tank followed by a lime or borax tank.

The rod is then placed in a baker where the crystal water in the lime or borax is removed.

The wire rod is then ready for processing in the wire mill.

Continous Pickling Line

View of Line through Tunnel Hood

Manually operated crane pickling line

Electrolytic cleaning or bipolar cleaning. (see sketch )

Electric current will always take the pass where the electrical resistance is the lowest. In an electrolytic bipolar cleaning tank, most of the current will flow from the cathode to through the electrolyte to the nearest point of the wire. The current will then pass through the wire to the point where the wire is closest to the anode, where it will exit the wire and again pass through the electrolyte on to the anode.

At the point where the current enters the wire Oxygen gas will form on the steel surface and where the current exits the wire Hydrogen gas will form on the steel surface breaking off the scale.

In order to reduce the amount of acid and electric energy needed, it is common to first mechanically de-scale (see below) the rod before it enters the bipolar cleaning process.

Mechanical de-scaling.

In this process the wire rod is pulled through a set pulleys (normally 5) 2 guide wheels and 3 breaker wheels of approximately 3 inch diameter with the axis of rotation offset 90 degrees.

As the wire is bent over the breaker wheels as much as 80 % of the mill scale is removed.

Scale breaker unit

View of Combination Line with scale breaker followed by steel brushes.

Most (often all) of the remaining undesirable scale residue can then be removed by a water/air jet cleaner using a combination of a water wash/air dry sequence.

or

The wire rod can be passed through an electrolytic bipolar cleaning process.

Electrolytic Bi-polar cleaning unit

Mechanical descaling followed by electrolytic cleaning borax coating and pull through capstan

or

The wire rod can be passed through a cavity cleaner Paraorbital unit where water at high pressure causes the wire rod to vibrate hence removing residual scale.

It is also common in certain applications like bed spring wire to let the wire rod pass through a set of abrasive belt sanders that polishes the rod surface while removing any remaining scale residue.

Abrasive Blasting or Sanding

Yet another method used is so called abrasive blast cleaning where abrasive material is "blasted" on the wire rod surface.

Sand Blasting Unit

Shaving.

Shaving is a method by which the rod is pulled through a shaving die that removes or shaves off surface imperfections at the same time as the mill scale is removed. This method has predominantly been used for stainless steel wire rods.