Introduction

Since its establishment in 1978, the Scotland-based company Rautomead International Ltd has become a leading specialist in the design and manufacture of continuous casting equipment for the processing of non-ferrous metals and in particular in plant for the production of oxygen-free copper and semi-finished rods, sections, hollows and bars in a wide range of copper-based alloys - all of the very highest quality.

Sir Michael Nairn, chairman of Rautomead International Ltd holding the IWMA's H.W Bennett President's Trophy for his recent technical conference: “Prevention is better than cure, a graphite-based technology in continuous casting of re-draw rod for multiwire drawing machines”

Indeed, Rautomead’s acknowledged expertise in electrical resistance heating technology and the use of a naturally oxygen-reducing graphite crucible has been found to offer significant benefits and major cost savings across the international wire and cable industry.

For an efficient production of superfine wires

With the global trend towards the use of the highest quality 8.0mm diameter wire rod as feedstock for the wire drawing process, Rautomead’s technology ensures efficient production of both fine and superfine wires, whilst virtually eliminating the occurrence of wire breaks resulting from non-metallic inclusions in the rod. Requiring no special foundations or superstructures, and consequently no complex civil engineering work, Rautomead’s continuous and casting machines have always required relatively low capital investment and have rewarded the user with significantly lower operating costs than associated with other systems.

RS6000 copper wire rod machine featuring a production of 12,000 tonnes per year

Where other manufacturers have relied on ceramic-lined, induction-heated furnaces, Rautomead’s melting and casting models have used high-intensity electrical resistance heating, a system involving the use of low-voltages, which is much safer to use and provides a high-degree of efficiency and control. This process, combined with the use of a graphite crucible has been proven to generate a large “heat sink” and highly accurate and very stable melt temperatures for the production of the very highest quality oxygen-free copper rod. With a single furnace providing both the melting and casting functions, the Rautomead process has offered safety, convenience, economy and product quality.

Limitations of scale-up potential

However, driven by customer demand for greater output machines, Rautomead recognised an output limitation of around 15,000 tonnes per year for its resistance-heated graphite furnace technology, constrained by the maximum size of the graphite blocks commercially available and sought alternative solutions.

Innovative new solution

With an increasing global requirement for casting technology capable of producing greater volumes of high-quality copper rod, Rautomead, therefore, committed itself to develop a solution that would meet the greater volumes desired by many industrial sectors, yet still provide the quality benefits of full oxygen reduction - an intrinsic feature of Rautomead technology and the company’s continuous casting process. Committed to providing high quality, low operating costs, convenience and safety, the company was also reluctant to pursue the route of separate melting and casting furnaces, as offered by competitors.

Close working relationship

In order to achieve its goal of creating a Rautomead model capable of casting in the region of 20,000 tonnes per year, in the millennium year 2000, Rautomead approached German induction heating specialists, Induga-GmbH. The outcome was a unique technical collaboration that was to result in the development of a brand new Rautomead series of machines and a totally new means of copper rod casting.

Already acknowledged as experts in the field of furnace technology, and manufacturers of process-optimised, high-performance, highly durable, environmentally friendly and inexpensive melting units, Induga was able to provide Rautomead with its highly cost-effective induction heating technology as used in its proven channel-type induction melting furnace offering high electro-thermal efficiency.

20,000 tonnes per year of 8.0mm Ø Cu-Of redraw rod

Resulting from the working partnership with Induga and designated the Rautomead RDG series, the new copper rod machine represents a significant leap forward in the production of copper rod production (in the field of 8.0mm to 12.7mm Ø) from a cathode feedstock.

Schema showing Rautomead RDG 3 machine that is designed to
produce 20,000 tonne per year of 8.00mm Ø Cu-Of redraw rod

The RDG model also incorporates the advantages of Rautomead’s graphite furnace technology with Induga-GmbH’s induction heating expertise, all combined in a single melting, holding and casting furnace for best quality and low-cost operation.

Twenty-strand casting capacity
Rated at 1,000kW and designed to produce up to 3 tonnes of high-quality oxygen-free copper rod re-draw per hour, or approximately 20,000 tonnes per year, the RDG 3 machine comprises an automatic cathode feed, a single 1,000kVA channel-type induction furnace, with separate melting and holding baths, a twenty-strand casting station and five-tonne capacity rod coilers. By employing integrated melting and casting in a single furnace, operating costs are also reduced by comparison with other systems that involve separate furnaces for these procedures.

20-strand casting station

The integrated furnace in the RDG 3 machine has a capacity of approximately 12 tonnes of copper and a tapping weight of 8 tonnes. Cathodes of up to 120kg are automatically weighed, preheated and then fed into the furnace that incorporates separate melting and casting chambers.

Oxygen reduction
Alumina linings are used in the induction furnace, with a sleeved graphite inner lining in the holding and casting chamber and a special graphite filter bed for conditioning of the molten copper prior to casting. A charcoal cover is used over the melting side and a graphite flake cover over the casting side of the furnace. These features ensure full oxygen reduction.

Rod withdrawal and casting
The twenty-strand casting station employed in the RDG 3 is a back-to-back arrangement of casting die and cooler assemblies, mounted on a carriage that adjusts itself automatically up and down for changes in the level of the molten metal. Rod withdrawal is by four separate, fast acting cam indexer drives, capable of generating over 1,000 cycles per minute.

Advanced Siemens control
In an era where total accountability and trace-ability are seen as key aspects in virtually every manufacturing and production process, the RDG 3 model boasts a state-of-the-art Siemens PLC and monitoring suite which provides the operator with a full picture of the casting process at all times, with automatic data logging and trace-ability. All key production parameters are monitored and alarmed via linked island controls providing accurate, timely data for cathode feed, rod withdrawal, coilers and cooling water service.

Highest product quality

With the very highest quality oxygen-free, as-cast copper re-draw rod in the diameter range of 8.0mm to 12.7mm for drawing to wire of British Standard 4109 CI03 and American ASTM Specification B1, B2, B3, CI0200 being achieved by using a LME Grade A copper-cathode feedstock and an O2 content in the rod of less than 5ppm, Rautomead has demonstrated that its continuous casting process for quality CU-OF re-draw can be extended to the requirements of industries requiring larger annual outputs.

Table I: The Rautomead RDG 3 at a glance

Table II: RDG 3 services

Other new Rautomead machines launched during 2002

In addition to the RDG 3 model, Rautomead has also introduced two other new continuous casting models during 2002. First is the RFS (Rod from Scrap) series machine. Following numerous requests for a continuous casting machine that can economically utilise scrap from feedstock, the new RFS series models have been designed to operate as integrated melting and casting units, providing one-stop conversion from selected grades of scrap to high-quality copper re-draw rod. 100% clean mill scrap - in the form of baled wire or briquetted granulated scrap - may be used, blended with a proportion of grade A cathode. Rated at 240kVA, the RFS machine will melt and cast at a rate of up to 300kg per hour on a continuous basis, with casting speed dependent on end product size and number of strands.

RFS series to redraw copper rod from scrap

Another new Rautomead model, the RST, developed for the continuous vertical casting of copper shapes, has also been launched during the year, and provides an innovative new option for the production of copper and copper alloy rod, strip and tube products. The first new model in the RST series range is rated at 240kVA and will continuously melt and cast at a rate of up to 400kg per hour. The withdrawal unit may be fitted with dies and coolers to produce single strands of strip and multiple rods and tubes, with strand output depending on size.

A tradition of quality and service

Marketed and supported exclusively by Rautomead, with active background technical support from Induga, the new RDG model benefits from the same high standards of service and customer after-care as with every Rautomead machine. Whilst Rautomead technology is both safe and straightforward to operate, the company recognises that users require specialist training and on-going technical advice, not only concerning the process itself, but also in such topics as planning the installation, selection of materials and in the down-stream working of the cast products.

During the latter stages of construction and testing of a new machine - and before delivery - a new customer will almost invariably send one or two of their key operating personnel for training. Quite apart from the opportunity for hands-on experience, such visits are important in establishing good personal relations with Rautomead’s engineering and customer service staff. After delivery, Rautomead will normally send one or more engineers to the customer’s works to check the installation, to supervise commissioning and to continue the training process. The result of this good planning is a smoothly executed commissioning programme.

Following hand-over, responsibility within Rautomead transfers from engineering to customer service. A customer service engineer will normally visit the new installation within six to eight weeks to review the status of the plant, answer customer’s queries, establish an on-going personal link, advise on consumable materials, on quality control procedures, on component identification and on stocking and usage of spares. At this time, clear lines of communication are established with those responsible for production management. Any shortcomings in the scope of supply, design issues or service to that date are also carefully noted for immediate review at head office. For larger machines, such as the RDG, Rautomead aims to maintain the pattern of service engineer visits on a six-monthly basis. Such visits are often planned to also coincide with a cold maintenance inspection programme.

Next-day spares and consumables back-up

Backing up this technical service presence, Rautomead operates a next-day delivery service for standard spares and consumables. This implies a significant and growing commitment to inventory and a highly developed, computer-based control system. Performance is constantly monitored and reasons for any failures to achieving next-day service are examined and addressed. Using air-courier service, specific components can generally reach customers anywhere in the world within three or four days. The engineering and manufacturing departments at Rautomead are constantly examining the scope for improved materials and component designs. Model improvements, updates and changes, however, are introduced only when thoroughly tested, with due consideration to the implications for all existing customers, whose machines would be affected. Technical improvements are made available to existing users without charge, except for the cost of the components involved.

The company views its relationship with customers in the nature of a long-term partnership. A customer’s success is no less important to the company concerned than to Rautomead itself. In a similar way, service and support by Rautomead are considered of no lesser importance, than the selection by the customer of good technology in the initial purchase.