Metal deforming – By use of tool acting during relative rotation between tool... – Spherical tool
Patent
1994-11-07
1997-01-28
Sheehan, John
Metal deforming
By use of tool acting during relative rotation between tool...
Spherical tool
72215, 72220, 148111, B21B 100
Patent
active
055968961
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of and apparatus for effecting domain refinement of electrical steels and especially, but not exclusively, high-permeability grain-oriented electrical steels. In particular, but not exclusively, the invention concerns apparatus operable to produce within steel strip and sheet lines of local plastic deformation which refine the strip or sheet's domain structures and reduce power loss without causing damage to the insulation coating of the strip or sheet thereby removing the need for recoating after treatment.
2. Discussion of the Prior Art
It is known that the magnetic properties of grain-oriented electrical steels can be enhanced by processing in a known manner which effects preferential alignment of grains within the steel.
One problem associated with known techniques for producing enhanced magnetic properties is that effecting optimum grain alignment tends simultaneously to produce larger than optimum grain sizes, this resulting in higher power losses than would have been the case with smaller grain sizes and domain wall spacings.
Known techniques for effecting domain refinement by creation of artificial grain boundaries include mechanical methods, lasers or high voltage discharge systems.
Hitherto, mechanical methods have not been found to be susceptible to commercial use with the result that relatively expensive laser systems are conventionally employed commercially. A relatively inexpensive spark ablation method (high voltage discharge system) is being utilised but this system tends to be rather slow for successful commercial use.
Although domain refinement can be achieved by a method known as mechanical ball scratching in which very small balls of diameter of the order of 0.7 mm are employed which are forced into contact with the surface of a sheet under treatment, the method is difficult to maintain and operate on a commercial basis. Also, scratching of the surface of the steel occurs, and recoating of the steel after treatment is necessary.
SUMMARY OF THE INVENTION
This invention sets out to provide a method and apparatus for refining the domain structure of high permeability grain-oriented electrical steels in which high localised pressure is applied to the surface of the steel to produce lines of plastic deformation in the form of lines spaced approximately 5 mm apart in directions generally perpendicular to the rolling direction of the sheet or strip.
A method of effecting domain refinement of a strip or sheet of electrical steel which is characterised by the steps of creating in the strip lines of local plastic deformation by moving a plurality of resiliently mounted spaced balls of diameter of at least 10 mm in to contact therewith.
Apparatus for effecting domain refinement of electrical steels comprising an assembly of an array of rotatable members mounted within a supporting structure and movable into direct contact with the surface of a strip or sheet of electrical steel to create lines of local plastic deformation which extend substantially across the width of the strip or sheet to effect domain refinement thereof, and means operable to impart relative linear movement between the members and the steel strip or sheet, the apparatus being characterised in that the rotatable members are spaced one from another such that the spacing between the lines of plastic deformation created by the rotatable members is at least 5 mm and in that means are provided for resiliently biassing the rotatable members away from the supporting structure.
The rotatable member preferably comprises a ball of relatively large diameter in contact with a relatively large number of smaller balls, which is resiliently biased away from its supporting structure and into contact with the surface of the steel strip or sheet. Each ball may be produced from any suitable hard wearing material, for example chrome steel or silicon nitride. It is preferable that the electrical steel is supported on a relatively hard surface/substrate during
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patent: 4513597 (1985-04-01), Kimoto et al.
patent: 4770720 (1988-09-01), Kobayashi et al.
Orb Electrical Steels Limited
Sheehan John
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