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Continuous sprayforming of electrotechnical steel strip
Journal of Magnetism and Magnetic Materials 112 (1992) 177-178 North-Holland
Continuous sprayforming of electrotechnical steel strip G.C. E a d i e British Steel Plc, C,rLr~Products Division, South Wales Electricity, Newport, UK
A controllable process is described for the continuous production of metallic strip by the spray method. An example of its application to silicon-iron elelectrotechnical steel is given.
The development of the more conventional non-oriented and oriented materials such as Hi-B and its successors has recently gone some way towards closing the gap between benefits derived from improved orientation coupled with domainsize control and amorphous material. Whether in relation to oriented or non-oriented material, the latest developments depend on increasing the specific resistance of the material. To produce high resistivity electrotechnical steel the author designed an experimental programme and devised a plant and working regime where the sprayforming techniqu~ originally developed by Professor Richard Sir~ger could be used. Because of a continuing commitment to customer service, British Steel and South Wales Electricity sponsored this work to demonstrate whether or not high resistivity electrotechnical steel could be formed continuously and with that degree of benefit. There were two physical problems to be solved: (a) control of strip width and thickness, (b) creation of the ability of the plar, t to produce strip continuously. Various stratagems and devices exist to spread particles over an area of target. The version used for electrotechnical steel is the scanning atomiser devised and supplied by Sprayforming Developments Ltd., a company set up by Professor Singer. The main thrust of the experimental proCorrespondence to: Dr. G. Eadie, British Steel Electricals, Orb Works, P.O. Box 30, Newport, C,went NP9 0XT, UK.
gramme therefore was directed to achievk~g continuity of strip production. A basic source of suitable particles was a plant constructed by PSI (Atomisers) Ltd. Using inert gas streams at supersonic speeds this unit produces spherical particles in the 1-450 lxm + range and permits the use of 'pusher' gas pressure to control delivery of metal while the atomisation gas pressure is separately controllable. Experiments with argon gas and various silicon contents indicated the best combinations of pusher and atomising pressures, nozzle to target distance, target temperaturt, t:~rget surface, particle size distribution etc. to 0.cliver material in an acceptable 'as-sprayed' co~dition. Experiments began with flat plates, then plates curved to match the curvature of the col!ector. This woF- eqtablished the footprint of the spray and sections taken from the various depositions indicated whether or not incremental casting was occurring, what degree of splat was achieved and the level to which gas was entrained. The target surfaces were prepared in various ways to prevent particle bounce off and improve releasability. For control of the process and effectivcr~ess of stripping and peeling, a small diameter co~iector roll of low thermal mass was designed and a knife blade of a specific angled section is preser.ted to the periphery at a specific point. The peeling at, ion is z~isted by a cracker roll whi zh p~events lift-off and run-back t6 the point of dcpcdtion. The collector roll is heated in order to "ontvd the metallurgical state of the deposited m-te~i~.
0304-8853/92/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights ieserved
G.C. Eadie / Continuous sprayforming of silicon steel strip
178
CRUCIBLE \
STOPPER ROD CONTAINNENT VESSEL
l
,
COHPACTOR
TO COILER
\ HEATER (ROLL) Fig. 1. Apparatus for continuous production of strip.
After generation the material is relatively cold and possesses some porosity so that reheating is essential. An in-line induction furnace provides re-heat prior to compaction after which the material is as dense as commercial material produced by conw~ntional processing. The final material has a rel~'tively good surface and is commercially acceptable, in the hot compacted condition. The e~perimental plant as presently evolved is illustrated schematically in fig. 1. Non-oriented material with up to and including 7% silicon has been prepared in widths up to 8 in. The improvement in power loss etc. is in
accord with resistivities of the order of 60 Ixf~ cm Of IllOfe.
It has been found that under certain conditions of composition and deposition higher silicon contents can be cold reduced with ease. (Examples of material prepared by the method described were exhibited at the Conference.)
Acknowledgements The author wishes to acknowledge the work of the experimental team D. Campbell, G. Richards and S. Hall.
Continuous sprayforming of electrotechnical steel strip G.C. E a d i e British Steel Plc, C,rLr~Products Division, South Wales Electricity, Newport, UK
A controllable process is described for the continuous production of metallic strip by the spray method. An example of its application to silicon-iron elelectrotechnical steel is given.
The development of the more conventional non-oriented and oriented materials such as Hi-B and its successors has recently gone some way towards closing the gap between benefits derived from improved orientation coupled with domainsize control and amorphous material. Whether in relation to oriented or non-oriented material, the latest developments depend on increasing the specific resistance of the material. To produce high resistivity electrotechnical steel the author designed an experimental programme and devised a plant and working regime where the sprayforming techniqu~ originally developed by Professor Richard Sir~ger could be used. Because of a continuing commitment to customer service, British Steel and South Wales Electricity sponsored this work to demonstrate whether or not high resistivity electrotechnical steel could be formed continuously and with that degree of benefit. There were two physical problems to be solved: (a) control of strip width and thickness, (b) creation of the ability of the plar, t to produce strip continuously. Various stratagems and devices exist to spread particles over an area of target. The version used for electrotechnical steel is the scanning atomiser devised and supplied by Sprayforming Developments Ltd., a company set up by Professor Singer. The main thrust of the experimental proCorrespondence to: Dr. G. Eadie, British Steel Electricals, Orb Works, P.O. Box 30, Newport, C,went NP9 0XT, UK.
gramme therefore was directed to achievk~g continuity of strip production. A basic source of suitable particles was a plant constructed by PSI (Atomisers) Ltd. Using inert gas streams at supersonic speeds this unit produces spherical particles in the 1-450 lxm + range and permits the use of 'pusher' gas pressure to control delivery of metal while the atomisation gas pressure is separately controllable. Experiments with argon gas and various silicon contents indicated the best combinations of pusher and atomising pressures, nozzle to target distance, target temperaturt, t:~rget surface, particle size distribution etc. to 0.cliver material in an acceptable 'as-sprayed' co~dition. Experiments began with flat plates, then plates curved to match the curvature of the col!ector. This woF- eqtablished the footprint of the spray and sections taken from the various depositions indicated whether or not incremental casting was occurring, what degree of splat was achieved and the level to which gas was entrained. The target surfaces were prepared in various ways to prevent particle bounce off and improve releasability. For control of the process and effectivcr~ess of stripping and peeling, a small diameter co~iector roll of low thermal mass was designed and a knife blade of a specific angled section is preser.ted to the periphery at a specific point. The peeling at, ion is z~isted by a cracker roll whi zh p~events lift-off and run-back t6 the point of dcpcdtion. The collector roll is heated in order to "ontvd the metallurgical state of the deposited m-te~i~.
0304-8853/92/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights ieserved
G.C. Eadie / Continuous sprayforming of silicon steel strip
178
CRUCIBLE \
STOPPER ROD CONTAINNENT VESSEL
l
,
COHPACTOR
TO COILER
\ HEATER (ROLL) Fig. 1. Apparatus for continuous production of strip.
After generation the material is relatively cold and possesses some porosity so that reheating is essential. An in-line induction furnace provides re-heat prior to compaction after which the material is as dense as commercial material produced by conw~ntional processing. The final material has a rel~'tively good surface and is commercially acceptable, in the hot compacted condition. The e~perimental plant as presently evolved is illustrated schematically in fig. 1. Non-oriented material with up to and including 7% silicon has been prepared in widths up to 8 in. The improvement in power loss etc. is in
accord with resistivities of the order of 60 Ixf~ cm Of IllOfe.
It has been found that under certain conditions of composition and deposition higher silicon contents can be cold reduced with ease. (Examples of material prepared by the method described were exhibited at the Conference.)
Acknowledgements The author wishes to acknowledge the work of the experimental team D. Campbell, G. Richards and S. Hall.