Steel

Extensive in-process damage to the external diameter of the Tuyere Cooler component, used in Blast Furnace operations, is a common occurrence and can lead to reduced processing capability and equipment downtime. This is especially pertinent when the substrate damage results in the Tuyere becoming lodged in the parent housing and having to be forcibly removed. Tata Steel together with Castolin Eutectic have developed a thermal spray deposition which would help negate the potential damage to the component and thus extend its useful processing life by reducing the build up and adhesion of Blast furnace by-products.

After extensive trials a composite coating structure comprising of a High Velocity Oxy Fuel (HVOF) deposited Nickel-Chromium coating together with a thermally converted slurry addition was used to protect the affected external surface. This coating produces a pore-free surface which inhibits the adhesion of the process by-products whilst protecting the substrate from extensive wear by chemical erosion.

The CastCoat hard composite coating was developed by the advanced Castolin Eutectic workshop in Newcastle, UK, for steel industry applications in particular for coating continuous Caster copper mould plates, for more than 20 years. Tests have shown that the coating is tougher than any other copper mould plate coating available. It has a low coefficient of friction which helps reduce sticker alarms and the coating is inert to liquid steel and casting powders. The coating system has no effect on mould level detectors or electromagnetic stirrers. It has also been proven that the coating has negligible effect on heat transfer rates.

With years of field data behind the coating, significant copper plate life improvements have been demonstrated: 3 – 4 times for thick slab casters and up to 6 times for thin slab caster narrow plates, accompanied by improved product shape. In operation, the coating has been shown to enable extended casting runs through dramatic increases in wear resistance. Eventual progressive degradation of the coating occurs due to the thermal fatigue in high stress positions. Now a mature technology with a worldwide customer base, CastCoat continues to provide users with reduced costs/tonne.

By coating all four faces of the mould, dimensional stability is retained throughout the campaign, leading to sustained and effective product shape and shell growth. The lack of appreciable wear means longer campaigns are possible between mould exchanges, achieving higher caster availability. In addition, the protection offered by the coating gives extended copper plate life, resulting in annual copper savings and delivering significant reductions in both on and off-line maintenance costs. With the recent development of a compact HVOF device, the CastCoat Composite Coating can now be applied to tube moulds.