As reported recently, here at Corewire we are delighted to announce the success of our Weldclad continuous caster roll trials. Our brand new Weldclad materials have been able to increase the lifetime of our customers’ continuous slab caster drive rolls by as much as 40%. But how exactly have we managed to do this? Let’s take a look.
The Continuous Casting Process
Continuous casting is a commonly used process within the steel industry. Essentially, continuous casters take molten steel and solidify it into designated profiles including, slabs, blooms and billets which are suitable for further processing and use within a wide range of industries.
Looking specifically at slab casting; the molten steel is fed into a mould, at the top of the continuous caster, forming the rectangular cross section. As it is carefully drawn vertically down the machine, it passes through a series of rollers positioned either side of the product on an inner (loose) and outer (fixed) face. These rollers support and maintain the shape of the product as it solidifies. The top zone of a caster typically consists of a vertical segment of rollers that traditionally lead into a series of further segments. The segments and rolls are positioned accurately on a 90 degree radius allowing the product to cool at a controlled rate whilst passing through the rolls from vertical, at the entry, to horizontal, at the exit. At the exit of the caster the slab has solidified sufficiently to allow it to be cut to length whilst the casting process continues.
Operating and Environmental Conditions Within a Slab Caster
Differing locations of rolls within the continuous caster are exposed to varied environments and operating conditions. The top zone, foot and bender entry rolls, for example, not only have to withstand high thermal cycling and high temperatures of the molten steel but also the high volume and potentially corrosive nature of the cooling water. As the slab moves down the casting machine, the steel begins to solidify which naturally increases the mechanical forces and abrasive wear on the rollers. This can be particularly evident on the inner face of the unbending segments where the cast product is straightened into the horizontal plane. In a similar manner, the drive rolls, that pinch the slab to maintain a set speed through the caster, typically experience greater mechanical force compared to the idle rolls. Our extensive research and development in conjunction with our customers has further reinforced the fact that if the metallurgical matrix of the roll surface is not suited to the environment in which it operates, the integrity of the rolls working surface becomes compromised and production life limited.
Maintenance and Increased Production
Reducing the frequency of segment removal, caster down time and lost production is essential. Removing a segment due to the premature wear of one roll is unacceptable and uneconomical. Cladding the roll surface with a material suited to its operating environment ensures consistent and even wear not only across one roll but also throughout the complete caster. At Corewire we have developed a range of Weldclad flux cored wires to achieve this.
Case Study and New Products
As a result of field trials with one of the largest global steel producers we have added a new product to our range of Weldclad roll cladding consumables. Specifically targeting the drive rolls in the caster, our in house metallurgists developed a composition suited to the high mechanical loading and abrasive wear witnessed by these rolls. The result was an increase in roll life of more than 40% vs. a traditional 414 type material but more significantly an increase in the consistency of wear across the complete segment. Further more, the roll surface displayed significantly reduced severity of cracking upon removal resulting in a reduction in rework required before returning the rolls to operation.
By understanding our customers, their equipment and requirements we continue to successfully develop and implement market leading products that produce significant roll life improvements and performance in operation.
For further information, please do contact the Corewire team on +44 (0) 1252 517 766.