Hazelett Strip-casting Corporation

Norman J Bergeron

R William Hazelett

Dean A Boozan

Wojtek S Szczypiorski

S Richard Hazelett

Thomas S Graham

Jerome B Allyn

John E Pennucci

George Desorcie

J F Wood

James G Villa

Thomas E Brennan

Electrostatic application of a dusting of dry, electrostatically adherable, thermally insulative powder particles over a workface of a continuous metal-casting machine in which the mold surface or surfaces which provide the workface or workfaces revolve in a generally oval course. A dry dusting of protective powdery refractory material is applied to the workface after being entrained in an air stream and electrostatically charged by suitable electrostatic apparatus. The workface to be dusted is electrically grounded for attracting the charged powder particles for adhering them to the workface. The resultant coating formed by the dusting so deposited is remarkably uniform over a substantial area of the workface, a phenomenon explainable by mutual electrostatic repulsion of the dry powder particles being deposited. Continuously re-applied dusting over the workface during a continuous cast provides an immediately useful repair or replacement of dusting powder lost from the coating on the workface of a revolving mold surface during casting. The dusting may be removed at will by means of an air knife.

Method and apparatus for continuous casting of metal

Electrostatic application of a dusting of dry, self-adhering, thermally and electrically insulative powder particles over a work face of an endless, thin, flexible, water-cooled, metallic casting belt advantageous for use in a continuous metal-casting machine. A dry dusting of protective powdery refractory substance is applied to the belt after being rendered airborne and electrostatically charged by various embodiments of suitable electrostatic apparatus. The casting belt to be dusted is electrically grounded for attracting the charged powder particles for adhering them to the casting belt. The dusting so deposited is remarkably uniform over a substantial area, a phenomenon explainable by mutual electrostatic repulsion of the dry powder particles being deposited. Continuously re-applied dusting over the work face of an endless casting belt during a cast provides an immediately useful repair of lost dusting powder. The dusting may be removed at will by means of an air knife. Certain powders that are effectively soft afford high thermal insulativity for the metallic casting belt, and desirably they cause only minimal interference with further mechanical processing of a cast metallic product into which they might inadvertently become entrained.

Electrostatic application of insulative refractory dust or powder to

The flatness of a casting belt in a continuous metal casting machine is continuously monitored and thereby also the condition of its thermal protective coating. One or more non-contacting eddy-current sensing probes are placed in proximity to the reverse or coolant side of a belt for sensing and measuring the distance of the belt from the probe to reveal irregularities in the flatness of the belt while it travels past the probe. A deficiency of insulative belt coating can cause variations in belt flatness during casting. By monitoring such variations an operator of the continuous casting machine is alerted that the coating needs to be retouched or replaced without interrupting the casting process. Or such monitoring can alert the operator that the belt has become inherently not flat. A similar proximity sensing probe is utilized for the purpose of supplying an instant report of the initial entrance of molten metal into the casting cavity adjacent to a casting belt at the start of a cast. In this way, forward travel of the casting belt is initiated in synchronized relationship with introduction of the molten metal into the casting cavity by starting the forward belt motion at the appropriate instant before the entrained plug ('dummy bar') which is positioned between the two casting belts is moved out of position.

Method and apparatus for sensing the condition of casting belt and belt

The wide, thin, revolvable, flexible, metallic casting belts are made to incorporate differential patterns of residual internal longitudinal tensile and compressive stresses. The two marginal areas are residually longitudinally stretched more than the main middle area straddled by these margins. This main middle area is used as a moving mold and is expected to contact molten metal. Thus, the treated belts have two marginal areas in a state of mild longitudinal compression straddling the main middle area in a state of mild residual longitudinal tension. During casting, when hot metal comes into contact with the main middle area of such treated belt, the main middle area expands. Because of the built-in differential compensating stresses, the stresses throughout such belt during casting advantageously become balanced or equalized across the whole belt width. This equalized stress condition during casting assures that the critical moving belt mold area will be flatter than experienced with belts not having differential stress treatment. Thus, cast metal product typically will be improved in flatness, surface finish, section uniformity, soundness and metallurgy. Two methods are described for longitudinally stretching marginal areas relative to the middle area: (A) Use a work roller effectively of larger diameter toward its end than its middle for stretching both margins relative to the main middle area; (B) Use conventional cylindrical work rollers and heat (for expanding and slacking) the middle area during roller-stretching while leaving cold margins for residually stretching both margins relative to the main middle area.

Method and apparatus for introducing differential stresses in endless

A unitary-layer partially metallic, suitably adherent, mechanically and thermally durable, non-wetting, fusion-bonded matrix coating on endless, flexible metallic casting belts for continuous casting machines is described. This fusion-bonded matrix coating is also advantageous for coating other molten-metal-contacting surfaces, in continuous casting machines, such as edge-dam blocks that define moving side walls of a mold cavity. The fusion-bonded matrix (or reticulum) coating provides advantageous accessible porosity throughout the coating and comprises a nonmetallic refractory material interspersed substantially uniformly throughout a matrix of heat-resistant metal or metal alloy, for example nickel or nickel alloy, which is fusion-bonded to the grit-blasted surface of the belt and anchors and holds the nonmetallic material. The coating is applied by thermally spraying a powdered mixture directly on the roughened surface. The result is to insulate and protect the underlying belt from intimate molten metal contact, from heat stress and consequent distortion and from chemical or stress-corrosive action by the molten metal or its oxides or slags. The nonmetallic material may be present, at least partly, in the form of isolated particles encased within the metallic reticulum and/or in the form of a second reticulum intertwined with the metallic reticulum. The life of the coated belts is dramatically increased, and the surface quality and properties of the cast product are significantly improved. The coating controls and renders more uniform the rate of freezing of the metal being cast, resulting in improved metallurgical properties. Formulations are described and a method of forming such coatings by thermal spraying.

Matrix coatings on endless flexible metallic belts for continuous

Laterally 'floating' thermal spray gun traversing apparatus and system for laterally tracking a revolving casting belt being thermal spray coated for applying uniformly spaced passes of thermal spraying on the revolving casting belt regardless of any lateral (edgewise) movements of the casting belt in either direction and regardless of any chamber in the edge of the belt. The thermal spray gun is traversed by a leadscrew and an adjustable speed drive for the leadscrew, both the leadscrew and its adjustable drive being carried by a frame mounted on a carriage freely movable along a trackway extending parallel to the axis of the leadscrew. A roller senses the lateral position of the edge of the revolving belt, and the carriage is moved by a source of motive power responsive to the sensed lateral position of the belt for causing the carriage together with the frame, leadscrew and leadscrew drive automatically to track the belt. This source of motive power is shown as a spring acting in a direction for urging the roller into contact with the edge of the revolving belt.

Laterally floating thermal spray gun traversing apparatus and system for

Machine for producing insulative and protective coatings on endless flexible metallic belts of continuous casting machines is described. The coating is applied to a revolving belt being supported and driven by pulleys in the machine. The coating is applied by thermally spraying a powdered mixture directly onto the roughened casting surface of the belt. The machine holds the revolving belt under tension and applies cooling to the rear (inner) surface of the revolving belt opposite to the region where the thermal spray gun is applying the coating to the belt.

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Burlington, VT, United States of America

Norman J Bergeron