7 - The manufacture of extruded MMA electrodes

Summary

As previously stated, almost all electrodes are produced by the extrusion process. The present day electrode consists of a core wire, centrally placed in a coating, usually silicate bonded (Vol. 1, p. 60). Double coated electrodes are also produced.

A semi-automatic production line may consist of the following:

1. Wire drawing. Non-slip hydraulic machines draw the wire through dies to the correct size, after which the wire is stored on reels.

2. Wire cutting. The wire is then straightened and cut to electrode length, giving burr-free wire rods of any required length which are stacked in bins.

3. The coating. The raw materials of the coatings are kept in raw material silos and from these the materials are sieved and dosed. It is the type and composition of these materials that determines the characteristic of the particular electrode. The dosing installations consist of a number of silos each fitted with a discharge system, dosing control and weighing facilities.

4. Silicate storing consists of tanks that are temperature controlled and from which the silicate is pumped to the mixer.

5. Dry blending and wet mixing. The batch is first thoroughly mixed in the dry state and then a measured quantity of silicate is added from a dosing unit. The wetted batch is then roughly mixed, emptied and removed to the slug press, where it is pressed into slugs ready for extrusion.

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