The background
With green concerns reigning supreme, car manufacturers are looking for steel that gives their vehicles better performance, not to mention a smaller carbon footprint. In other words, they need steels that are lighter but stronger.

 

Steels alloyed with manganese, silicon and aluminium are called advanced high-strength steel (AHSS). These steels are used to make cars and other vehicles lightweight and, hence, more fuel efficient, yet safer thanks to better crash-resistance performance.

 

The Zodiac unit of Tata Steel’s Europe operations is a hot-dip strip steel galvanising plant at Llanwern, UK, that processes 420,000 tonnes of AHSS every year. Galvanisation is the process of applying a protective zinc coating to steel or iron in order to prevent rusting and corrosion.

 

What Zodiac does is heat treat the steel in a gas-fired furnace to produce a surface that is not oxidised, and then apply a galvanised coating by way of a molten zinc bath to protect the steel against corrosion.

 

The problem with conventional galvanisation techniques is that the steel produced is inconsistently or inadequately coated. There are always bare spots that are prone to rusting. In spite of talking to other galvanisers around the world, the Zodiac team could not find an easy solution. To change the existing techniques would have cost the unit at least £500,000 and possibly led to patent issues.

 

The Zodiac team put on its thinking cap to work out a new processing technique. In a completely in-house initiative, it has conceived, designed and implemented an innovative pre-oxidation technique that provides ‘wettability’ for successfully galvanising AHSS.

 

This solution is not just a much better process, it is also cheaper. The new technique and installed equipment provide cost-effective and improved galvanised coating quality and consistency, and no little bit of satisfaction.

 

This allows Zodiac to charge a price premium for its higher-quality product. It has already successfully commercialised one of its product lines and is working to develop other AHSS grades. And its customers — BMW, Jaguar Land Rover and Nissan — are already buying the new steel.

 

The innovation
Pre-oxidation is the best technique for galvanising AHSS. However, the standard practice is to achieve pre-oxidation by adjusting the combustion ratio control of direct fired burners.

 

What the Zodiac team did was to look at novel ways to “wet the surface” with zinc. Zodiac developed a new technique that involves applying a jet of gas at a specific oxygen concentration directly onto the strip surface within the annealing furnace.

 

New equipment has been designed to apply the gas mixture evenly across the strip surface. Additionally, a gas-mixing system was conceived to provide an accurate and consistent supply of oxygen.

 

The biggest concern during implementation was designing a system that was intrinsically safe and did not affect the integrity of the annealing furnace. A detailed hazard study was done and the technology was adapted for full safety.

 

In order to minimise downtime during the changeover, a full management-of-change study was done. All trials and modifications were conducted within the normal and scheduled maintenance periods.

 

The payoff
There are several benefits of Zodiac’s innovative technique. There is a cost saving in that the in-house developed solution was less expensive and cost only £150,000. Then there is the fact that Tata Europe can gain increases on the enhanced product over average hot dip galvanised sales values.

 

Zodiac is now the only known galvanising line in the world to use this solution. A patent has been filed and is in the process of being granted. Moreover, the team has developed a high degree of expertise in pre-oxidation technology, better than any other galvaniser in the world.

 

Then there is the very satisfying insight that solutions to problems can come from within. All that is needed is a sound understanding of the key principles of the problem and a thirst for developing a better solution.