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Electrolytic Cleaning Line

High Current Density Electrolytic Cleaning Lines (ECL)

Cold rolled coils processed in cold rolling mills have a thin film of residual rolling oil on the surface after rolling. The alkaline cleaning of cold rolled coils by the use of high current density (HCD) ensures totally clean surface of the strip before annealing. This electro-chemical cleaning process is called Electrolytic Cleaning and the processing line the Electrolytic Cleaning Line.

These techniques are more effective in cleaning cold rolled steel than conventional cleaning processes used on high speed electro tinning and alkaline-cleaning lines.

A cleaning of 92% was achieved by Essar Indonesia using Dassnagar's high-current-density Electrolytic Cleaning lines.

CASE STUDY
Tata Ryerson Continuous Roll Forming Line
Tata Steel Coil Dividing Line
Raymond Steel Normalising Line

The Technology

An ECL line cleans the strip surface of oil and dirt by chemical action, using an alkaline solution. The strip passes between electrodes which are immersed in tanks containing the electrolyte. This technique is more effective in cleaning cold rolled steel than conventional cleaning processes used on high speed electro tinning and alkaline-cleaning lines.

Classification

They are categorized into two types :

  • High Current Density (HCD) Electrolytic cleaning lines
  • Low Current Density (LCD) Electrolytic cleaning lines

The Dilemma !

A "Low Current density" Electrolytic cleaning line with multiple mechanical brushing units remove about 80% of the black Carbon patches, resulting on cracking of rolling mill lubricants during the annealing phase. These sheets are not acceptable in sectors where aesthetics ("Look and Feel" after painting) is desired. But being a cheaper solution often used by processors who look for economy.

On the other hand a "High current density" Electrolytic cleaning line with multi brushing roll units can clean cold rolled annealed strips often upto 98% purity. But lines with two sets of Brushing units are too expensive and thus not recommended.

A compromise can be made by using  Dassnagar's  high-current-density electrolytic cleaning lines, encapsulating a single brushing unit.  A cleanliness of 92% has been achieved at a continuous line speed of  250 MPM. Higher speeds can be achieved based on system design. The chemical technology is based on Nippon Steel-Japan, pioneers of chemical cleaning technology. Low current density lines are also available on request.

Fact sheet

Following figures have been achieved :

Contaminants Incoming Strip Outgoing Clean Strip
Oil and Dirt 800 mg / sq. meter 20 mg / sq. meter
Iron Fines 200 mg / sq. meter

Cleanliness : 95%

Cleaning solution used :  Na4SiO4

Salient Features

  • wide processing range 0.40 mm to 4.6 mm
  • productivity > 300,000 tpa, line speed 350 mpm, 
  • cold rolled annealed strip cleaning upto 95%,
  • electrodes below strip have sufficient clearance to allow sag between sink rolls,
  • gauge measuring system after breaker unit,
  • strip lead & tail end joining - ADS Indexing, double row strip stitcher,
  • auto tail out function ensures that the coil is processed till its tail,
  • bridle roll units provides tension to avoid sagging,
  • uncoiling tension - by DC motor - drag generator principle,
  • side trimming or slitting possible online
  • automation - level 1, 2 or 3
  • in house manufacturing of all equipment to maintain quality,
  • servicing within 48 hrs in any corner of the world,
  • readily shippable spare parts
chemical cleaning principle
Process Lines - For Sale
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