Research collaboration improves consistency of thin coatings for BlueScope products

Researchers at the ARC Research Hub for Australian Steel Manufacturing, based at the University of Wollongong (UOW), are engaging with BlueScope Steel and other partners from Australia’s steel industry to solve complex problems in the manufacturing process for steel.

One of these critical challenges being addressed by a joint UOW-BlueScope-University of Queensland research team at the Hub involves the production of smooth, uniform, thin metallic alloy coatings on high-quality coated steel products.

Coated steel products—such as corrosion-resistant metallic alloy coated steels—are important for Australian steel manufacturers, particularly in building applications that must withstand the demands of the harsh Australian climate for extended periods.

The metallic alloy coating is applied to the steel strip by first passing the strip through a molten alloy bath, such as in hot-dip galvanising; then, as the strip passes out of the bath, an air jet knife is used to blow or ‘wipe’ away the excess coating material to achieve the desired coating thickness and uniformity.

While the process sounds simple, tuning the system correctly involves understanding and predicting the effects of several process variables, such as the speed of the steel strip, the pressure of the air jets and the coating material itself.

This poses a constant challenge for steelmakers in delivering high-quality coated products that meet product specifications and customer requirements.

Associate Professor Buyung Kosasih, a Chief Investigator within the Steel Research Hub, from UOW’s Faculty of Engineering and Information Sciences (EIS), said that the research team had developed mathematical and numerical models that enable the prediction of the coating response under different operating conditions.

“This represents a key modelling tool for BlueScope operational personnel to produce quality coatings,” he said.

“The mathematical model is the first that links instability of the air jet knife to potential non-uniformities in the coating surface.”

Using the numerical model, the unsteadiness of the actual air jet knife was mimicked. The result highlighted a critical operating threshold that produced either a smooth or rough coating finish of the metallic alloy coating. 

This identified link between jet fluctuation frequencies and coating thickness response has now been employed in the planning of laboratory-scale experiments carried out at BlueScope facilities and can be used to assist selection of air jet knife operational settings in industry and optimisation of jet design.

A complimentary experimental approach to this challenge was also undertaken, through the development of a test rig to simulate the air jet knife. The test rig has proven capable of reproducing the results of simulations, and so has further validated the models.

Associate Professor Kosasih said the outcome was a result of a most fruitful collaboration and engagement between industry personnel and researchers.

“By closely working within a collaborative team comprised of industry, and researchers from multidisciplinary backgrounds, we can approach the challenges from multiple angles and provide skills that BlueScope does not currently have in-house, such as advanced modelling and experimental techniques,” he said.

“As researchers, we benefit significantly from such engagement.”

“First, the opportunity to carry out fundamental research, in this case, modelling the stability of impinging planar jet and thin-coating film, which is close to real-world applications; and second, the opportunity to build relationships with industry via routine face-to-face discussions.”

The Steel Research Hub is funded through the ARC’s Industrial Transformation Research Program, with additional funding from BlueScope and five other industry partners. The Hub was launched in 2015, with $13.5 million cash and $12 million in-kind contributions over five years.

BlueScope Process Development Leader Wayne Renshaw said: “The Steel Research Hub provides ready access to researchers with advanced skill sets, a deeper understanding of the scientific fundamentals and a different way of thinking.

“This, along with a willingness to understand the specifics of the industry challenge and genuinely collaborate, is proving valuable.”

The Steel Research Hub’s vision was to bring together teams of internationally-recognised research and industry talent, to deliver innovative solutions and breakthrough technologies in steel manufacturing and product development, and to help ensure sustainable growth in the Australian steel industry.

The collaborative R&D project described above is one of a number of tremendous and very encouraging examples in the Steel Research Hub, where challenging industry issues were solved through innovative research. 

Overall, the Steel Research Hub is an excellent example of the success of the ARC’s Industrial Transformation Research Program and its objectives. 

 

Images (Top): Andrew Johnston and Buyung Kosasih, assessing the performance of the Mark I slotted air jet laboratory equipment. Credit: Paul Jones.

(Bottom): Buyung Kosasih, Andrew Johnstone, Le Quang Phan, and Rubel Ahmed Laboratory test equipment at UOW for impinging planar jet research: 1:1 scale to industry jet. Credit: Craig Holbrook.