Page 1 of 16

Conticast® Group CONTICAST® TECHNOLOGY

CONTICAST Directors - Sandy Cochrane and Geoff Yeoman - give an overview & introduction to the Continuous Casting Technologies offered by CONTICAST INTERNATIONAL LIMITED. INTRODUCTION:- CONTICAST commenced building continuous casting machines of its own advanced technology designs in 2002. The technology kernel elements of CONTICAST® designs are broadly based on high quality performance furnaces which include the use of safe mains isolated-low voltage high intensity graphite resistance heaters, specially lined graphite crucible and submerged casting die assemblies which include coolers of special thermodynamic design (conticast ultracoolers®). At the heart of the latest system designs (conticast GraphCC®) thermal energy is transferred to the liquid metal by radiation, conduction & convection from a chain of heaters through the graphite crucible wall. The use of graphite as a crucible melt containment medium is especially convenient, as it is an extremely good high temperature heat susceptor, due to its inherently high thermal conductivity, which is higher than most metals. It is not wetted by most liquid metals & has also an increasing strength when operating at elevated temperatures with no practical upper limit of operation. Graphite systems however, react with water vapour & oxygen at elevated temperature, hence have to be protected from the factory normal atmosphere. In consequence, the whole system is contained in a hermetically sealed furnace case purged with a pure inert gas at low pressure & flow, to protect the graphite components. This gas vents over the top of the melt, giving a further benefit of an inert cover over the top of the liquid metal. Exceedingly high quality “world-class” non-ferrous semis CC products are obtained from such systems. Over the years since United Wire, Edinburgh’s (Unicast CC systems) concluded their interests in the promotion of CC technology machinery manufacture & sales, the original design was taken up by and advanced by CONTICAST® personnel, to where it is today. Significant design updates of process control, modern materials engineering, together with metallurgical process developments led to a greatly increased range of alloy material applications. This extended the use of the machines from the original brass and bronze market into production of many other coppers & precious metals based alloys in the forms of rod, strip, and hollow bars. Many applications, too numerous to mention, have been found in precious metals, where the benefits of high product quality and ease of operation by specialist users in the jewellery (Karat golds etc), electronics (10ppm Be doped high purity gold re-draw rod for drawing to ~30µ diameter electronic bonding wire), coin production (minting) and dental alloy fields (assorted alloys for prosthetics). A full list of castable alloys may be found on the downloads page at http://www.conticast.com

Page 2 of 16

FIG 1 Upwards Casting mode die assembly for the production of 6mm dia. copper alloy

wire rod immersed in melt held at 1250ºC

FIG 2 Production of 6mm diameter copper alloy redraw rod for drawing to welding wire

Page 3 of 16

OXYGEN FREE COPPER ROD (CuOF):- CONTICAST has now adapted its proven GraphCC® continuous casting system of RF HCC machines to create a range of vertically upwards mode casting machines, models RV700, 1050, 1800, 2200, and 3000, with the objective of production of the copper wire industry standard 8mm diameter, oxygen-free high conductivity copper (CuOF) re-draw rod. The application of CONTICAST GraphCC® systems to vertically upwards mode continuous casting gives many advantages as compared to horizontal casting methods:

• generally higher casting speeds • fast die changes hence higher plant productivities • plants are inherently more safe to operate.

The CONTICAST philosophy is to provide equipment which can be fed with cut grade A copper cathode. The inconvenience of having to shear the cathode, is more than compensated by:-

• the GraphCC® melting crucibles are of low unit cost. • the proven standard crucible design integrity guarantees long

system life without concerns of premature failures. • each casting system has two distinct & separate chambers. • Crucibles share a commonality with other standard CONTICAST

GraphCC® HCC models, hence are readily available.

The high temperature furnace technology supplied by CONTICAST utilises fully lined graphite containment systems for holding the bath of molten metal, in conjunction with using high thermal extraction efficiency submerged graphite casting dies and cooler assemblies (ULTRACOOLERS®).

Carbonaceous cover

MELTING SECTION CASTING SECTION

FIG 3 CONTICAST model RV machine general section

CAST STRANDS

CASTING DIE ASSEMBLIES

SCRAP & VIRGIN METALS FEEDSTOCK

LIQUID COPPER

HEATERS

GRAPHITE FILTER & BED SYSTEM

Page 4 of 16

The melt holding system of the RV machine is divided into two discrete separate but connected sections, (a melting chamber and a casting chamber, joined at the bottom) so that the molten copper is not exposed to atmosphere at any stage. The surface of the melt in the holding casting section is covered with graphite flake, whilst the melt surface in the melting section is covered by a blend of charcoal and flake graphite. Cut cathodes are lowered either manually or automatically into the melting chamber at a rate predetermined by the designed casting output for the system. The copper rod is cast out through the submerged casting dies in the casting chamber at a similar rate. Fluctuations in the metal level as batch feeding of cathode is converted to continuous production of rod are accommodated by some rise and fall in the level of molten metal in the crucible system. The casting dies as immersed in the casting chamber, are arranged to move up or down to maintain a constant cupro-static head, as the level of metal in the crucible rises or falls. The process as designed for production of oxygen-free copper (CuOF), uses principally grade A Copper cathode feed stock, which will make products to Cu-OF re-draw rod quality at 10ppm maximum oxygen content. The cathode will typically have an oxygen content of 60-90 ppm, which the process auto-deoxidatavely reduces <10ppm and generally to levels of <5ppm. Features of the RV process contributing to the reduction of oxygen content are:-

• the totally enclosed nature of the process, with no air exposed hot metal transfers

• graphite crucible, whereby the copper is exposed only to a massive carbon-based containment environment

• only very short holding time is required for liquid copper in contact with massive carbon in order to reduce the liquid copper oxygen levels to CuOF numbers. (refer to table below)

• special graphite filter beds in the casting chamber Calculated time to reduce the oxygen content of liquid copper to one tenth of its value, by reaction with carbon crucible or top cover. Deoxidation at top Deoxidation at Melt Size (hrs) crucible (hrs) 10Kg 0.59 0.06 100Kg 1.30 0.14 1 tonne 2.70 0.31

FIG 4 CONTICAST model RV machine general section

(courtesy of/acknowledgement to INCRA, table 3.2.1 taken from INCRA monograph XI The Metallurgy of Copper.)

The copper rod products emanating from this type of process are essentially rendered oxygen free, & have normal oxygen contents typ. 1 - 4 ppm.

Page 5 of 16

SYSTEM INSTRUMENTATION:- The process design is environmentally, operationally and in terms of maintenance, very friendly, being carried out in a totally enclosed, inert gas protected furnace and in an energy conserving environment. State-of-the-art Windows based PC (SCADA) monitoring and microprocessor control systems ensure the systems operation eliminates all potential aspects of human error and permits highly accurate control of the process variables. As the “Window” into which one can view the bigger picture, many system temperatures are monitored in both the melting & casting sections of the unit. A typical touch-screen is shown as at Fig 6. Where systems are fitted with AC servo drives, PC control and monitoring of these also is carried out and a full pre-programmed library of parameters can be made available to cover any given casting campaign parameter set up. Fig 7, shows a typical PC touch-screen.

FIG 5 TYPICAL PC SCREEN showing (upper) graphical trending and (lower) a partial

page of temperature channel information, which can be snap shot & downloaded at varying frequencies, into an MS Excel® spread sheet file, as part of the system

process quality batch measurements.

Page 6 of 16

FIG 6 TYPICAL PC SCREEN showing AC servo drive controls

These PC control and monitoring features contribute significantly to a repetitive-reliable product output, of consistency to a first quality. CASTING DIE INSERTS:- Casting die inserts are made in high density fine grained graphite and are fitted into special copper alloy cooler assemblies (ULTRACOOLERS®), cooled by a high velocity internal water flow. The melt initially solidifies as rod in the primary casting insert then in turn exits the die assembly through a series of secondary cooling inserts. The rod exit temperature is normally ~ 80ºC. DIE LIFE:- Casting die insert life can be expected as ca. 7 - 11 days in continuous production of 8mm CuOF rod. Casting dies are normally changed as a set, coinciding with the completion of a batch of coils. This takes approximately one hour to complete. In the event of a rod break, an individual casting die can be changed at any time, without affecting production of the remaining strands. Rod withdrawal is by pinch rolls, powered by an electromechanical indexing drive. One or two independent drives are provided, depending on the size of machine. A standard machine is configured for production of rods 8.0mm to 12.7mm diameter. Machines can be specified for production at up to 30mm diameter if required.

Page 7 of 16

COILING:-

FIG 7 Coiling copper alloy wire rod at 6mm diameter as cast condition.

After casting, the rods are guided from the machine into rod coilers. Normal coil dimensions for 8mm rod are ~1.8m OD x 0.8m ID, with a coil weights of 250 – 4000 kg as required. Coiling rates are fully synchronised to casting production speed by means of a loop controller. Facilities are provided for wax coating of the rod surface as required. SAFETY FEATURES:- AA The basic concept of having the high temperature melt reservoir with its high degree of stored energy, underneath the casting system, automatically imparts one critical safety attribute to the upwards vertical CC process. BB In CONTICAST RV machines, mains isolated – safe low voltages are used to power the furnace heaters. This varies between 24 - 40 volts (according to model). CC All the system operating parameters, incl cooling water, inert gas, furnace & die temperatures etc. are monitored – connected to an alarm system.

Page 8 of 16

DD At the contract placement stage and certainly before going live, a full consultation discussion between Conticast and the client will occur, in order to ascertain the degree and likely-hood of power disruption events. This will be to analyse & determine the fail safe and critical back up requirements for the plant, EG whether a simple UPS system only will be required, or whether plant protection and productivity will be best served by means of a stand-by power generator. EE In the event of any large scale emergency, the furnace melt contents can be safely and quickly emptied out, by the use of a manually operated valve and tap-hole at the side of the furnace. ANCILLARY EQUIPMENT OFFERED:-

1. primary water cooling

FIG 8

Page 9 of 16

Primary water cooling (twin) pump module

FIG 9 Twin cooling pump module with expansion tank.

Water recirculation circuits which cool the casting die assemblies, transfers a great deal of the system thermal energy. In consequence, an ultra clean & chemically pure (completely salts-free) water fluid is required. CONTICAST offers adequately sized pumped modules which supply a closed circuit pumped primary water cooling system, which is site filled with distilled or deionised pure water. This primary system is fitted with a water-to-water heat exchanger, ready for connection to a pumped cooling tower, airblast type or borehole secondary cooling system.

2. Inert gas supply

The use of an inert gas atmosphere – usually pure nitrogen - within the furnace is necessary for the protection of the graphite heaters, crucible and internal furnace structural members operating at high temperatures. If supplies of oxygen-free nitrogen (<5vpm O2 and H20) are not available, then CONTICAST can offer to supply a nitrogen generator, which manufactures nitrogen from compressed air by psa (pressure swing absorption) method.

Page 10 of 16

FIG 10 PSA Nitrogen Generator

3. Stand-by power

FIG 11 typical back up – stand by power generator (ack. John Deere)

Back-up generators can be supplied with capacity available to normally operate the plant, or alternatively to maintain the furnace at a standby temperature.

a) quality control

Page 11 of 16

Conticast recommend that in using grade A cathode or other certified feedstock, an oxygen analyser may be considered, together with a SIGMATESTER unit in order to measure the %IACS levels in the product. A tensile testing machine may be useful. In addition to the above, if regular use is made of scrap feedstock, then some form of spectrometer will be necessary in order to measure and control specific impurities in the alloy. CONTICAST can advise and/or supply all the necessary quality control equipment to use with the casting machine.

PRODUCT QUALITY:- The rod produced by the RV process is a fully soft as-cast material and is ready for immediate drawing or rolling to wire or strip products.

FIG 12

8mm dia. CuOF wire rod 12mm dia. CuOF wire rod FIG 13. shows the typical longitudinal and transverse section grain structure of as cast 8mm and 12mm diameter Cu-OF product. The rod exhibits a characteristic layer of chill grains close to the rod surface, long columnar grains and an equiaxial crystal core. The structure is symmetrical, with a central casting “eye”, showing an even influence of the solidification cooling

Page 12 of 16

around the circumference of the rod. Typical physical properties of the as-cast 8mm rod are Tensile strength 175 N mm2 Elongation 50% + As an as-cast product, there are no inclusions and/or other faults associated with rod rolling, such as “rolled in” non-metallic and/or constructional steel particles. Attributes required for a higher quality as cast wire rod for drawing to fine wire sizes include a wholly homogenous metallurgical structure, with no shrinkage or gas porosity present. The as cast 8mm wire rod is processed on a conventional rod break-down machine and is usually annealed in-line as a last stage in the breakdown machine, at around 2.0 – 2.6 mm diameter. At that stage, the “as cast” structure has been completely broken down and recrystallised, with typical physical properties as under: Elongation 40% + Conductvity 101 % IACS Where enamelled wire is to be produced, the rod is drawn down to the final size without annealing, followed by enamel coating and then annealed as a part of the high temperature enamel stoving / curing process. FINE WIRE DRAWING:- A complete absence of suspended oxides, porosity and surface imperfections in the CONTICAST RV CuOF re-draw rod make it ideal for wire drawing to superfine wire sizes. For example, at 0.050mm diameter, a wire break performance of <1 wire-break in each 300kg wire processed has been reported as being readily achievable. MAGNET WIRE:- Production of magnet wire calls for close attention to rod surface quality, in terms of roundness, cleanliness and a total absence of all surface singularities. Because RV re-draw exits the casting die assembly at <80ºC, the surface oxide layer on the as-cast rod is exceedingly low, & usually measures at <20 Ä. thickness, making it particularly suitable for magnet wire applications. COPPER ALLOYS:- CONTICASTS’ RV process is also eminently suitable for production of some of the higher strength alloy coppers:- CuCd1.0 automotive, robotics & trolley wire Cu Sn0.4 trolley wire & robotics CuMg0.3 trolley wire & robotics CuSi3 welding wire

CuSn5 phosphor bronze Cu64.5Ni18Zn nickel brass CuAg0.1 high temp. conductors applications.

Cu-DHP for tubes/general other applications.

Page 13 of 16

A full list of CC process castable alloys may be found on the downloads page at http://www.conticast.com Conticast equipment for the production of alloys, is essentially similar to that used for pure Cu-OF rod production. Special ventilation systems are required to handle any toxic fumes e.g. cadmium fume in the production of CuCd1 alloy. In alloy production the assorted ingredients require to be weighed and these weighed amounts are sequentially fed to the CC machine. Alloy addition is made using master alloys or hardeners and melt compositional homogeneity in the casting chamber is achieved by use of the complex routings for the liquid metal through the crucible ducts & internal baffle system. The use of a combined - integrated melting & casting process without external to process exposure of the melt, gives great benefits in the “fade loss” of readily oxidisable elements. e.g. in the production of CuMg0.1- 0.3ght tolerances. Also with producing brass ( CuZn ) alloys, integrated melting and casting almost eliminates zinc vapour fume emission. The RV machines can be configured to produce up to 50mm diameter rod, although at this size and above, vertical or horizontal mode machines may be more convenient to use in the context of bar handling, strand cutting & c. TOTAL ENABLING TECHNOLOGY SUPPORT:- CONTICAST provides the highest quality of metallurgical plant and process hardware in the world today. In addition CONTICAST acknowledges the critical importance of impartation of “know-how” and technology data in training of users operating personnel. Uniquely, CONTICAST have both metallurgically trained and highly skilled engineering personnel, who will be closely involve with all aspects of start-up and operation of any plant supplied. CONTICAST’S engineers will give total support during plant start-up & this will continue to the point of plant handover. MODEL RANGES AVAILABLE:-

Model typ T/yr. output RV 700 RV 1050

600 1000

RV 1800 1800 RV 2200 2000 RV 3000 4000

(above outputs are based on 6000 available production hours per year, excluding maintenance.) Multiples of the above optimised designs of plant size can be combined to give overall growth in output capacity as demand rises. EG for an 8000 tonnes per year output requirement schedule, 2 x RV3000 plants may be combined.

SPACE REQUIREMENTS:- The plants are compact and of relatively low footprint. Layouts can be adapted & adjusted to fit into the customer's existing buildings.

Page 14 of 16

CONTICAST will provide layout drawings as a normal part of the overall plant engineering service to contract customers.

FIG 16 Typical Layout model RV2200 Operating height is ~7 m., over the immediate area at the furnace. No floor excavations are necessary & the plants can be conveniently positioned on top of a level 150mm thick air-entrained reinforced (standard) concrete floor. CUSTOMER SERVICE:- CONTICAST is in business for the longer term & nothing less than a total customer satisfaction is paramount. CONTICAST at all times, endeavours to maintain a close active working relationship with customers, & will give customers the benefits of CONTICAST’S ongoing improvements/advances in technology. IN BRIEF • CONTICAST OFFER A RANGE OF CC PLANTS FOR THE PRODUCTION OF

OXYGEN FREE COPPER & COPPER ALLOY REDRAW ROD. • ESTABLISHED GRAPHITE FURNACE “STILL BATH” FURNACE TECHNOLOGY

WITH NEW IMPROVED MELT CONTAINMENT DESIGN. • PROBABLY THE BEST SYSTEM IN THE WORLD TODAY, FOR THE

PRODUCTION OF OXYGEN FREE COPPER & ALLOY ROD FOR DRAWING TO MAGNET & SUPERFINE WIRES.

• TOTAL PACKAGES, INCLUDING ALL TECHNOLOGY (KNOW-HOW) TRANSFER.

Page 15 of 16

APPENDIX page 1 of 2

Page 16 of 16

APPENDIX page 2 of 2

All rights reserved and all trade marks are acknowledged. Copyright MMVI: Conticast Group.

This article is provided for general information purposes only. No warranty or guarantee is implied by way of any of its material content, which expresses only the views of its authors. The article may be freely copied. The authors would welcome comment-discussion on any of the topics contained within the article. Contacts are conticast@sacomet.com and conticast@aol.com

Authors: Sandy Cochrane and Geoff Yeoman, Directors, Conticast Group.