Hazelett Strip-casting Corporation

Other

Usx Corporation

J F Wood

R William Hazelett

Charles D Dykes

Jerome B Allyn

James G Villa

Norman J Bergeron

Wojtek S Szczypiorski

Charles R Simon

Sabah S Daniel

Woitek Szczypiorski

Steering, tensioning and driving a revolving metallic casting belt in continuous casting machines wherein the belt travels along a generally straight casting plane P. Two two-axis robotic mechanisms are positioned at opposite ends of an exit-pulley drum, each including a 'floating' housing carrying a bearing rotatably supporting a journal at the respective drum end. A drive shaft connected to one of the journals rotates the drum for revolving the belt. The robotic mechanisms adjustably position opposite ends of a rotating drum in X--X plane parallel with plane P for tensioning the belt and in Y--Y plane perpendicular to plane P for steering the revolving belt. These robotic mechanisms are controlled to operate in any of several modes: (1) 'Walking-tilt' steering keeps the belt much closer to an exiting product than prior art, the belt being flatter and in better contact with the product for improving casting speed and quality. Mode (2) provides a 'virtual squaring shaft' causing a drum to simulate being constrained by a rigid mechanical squaring shaft for synchronizing downstream movements of both drum ends for regularizing tension fully across a 'cylindrical' casting belt. In modes (3), (4) and (5) the rigidity of the virtual squaring shaft may be 'softened,' or re-zeroed or eliminated, to accommodate small 'frustro-conical' errors in belt manufacture. Moreover, even a small error in built-in length dimensions of a belt carriage may effectively be canceled by mode adjustments which effectively 'twist' the virtual squaring shaft.

Steering, tensing and driving a revolving casting belt using an

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 method and belt composition for improving the performance and flatness of thin revolving flexible casting belts of continuous casting machines wherein at least one wall of the moving mold is provided by a thin flexible endless metallic casting belt having a permanent insulative coating with fluid-accessible porosity in this permanent coating. Contrary to prior methods and apparatus which have sought to protect the wide thin casting belts, the present method for improving belt flatness and performance involves providing a Helium-containing gaseous film between the metal and the front face of the casting belt which is coated with a permanent insulative porous coating. For significantly improved results, this gaseous film contains at least 8 percent and preferably 15 percent and optimally 20 percent or more of Helium by volume and is non-reactive with the metal being cast, resulting in a controlled increase in the rate of heat transfer and for causing such heat transfer to become more nearly uniform and stabilized across the width of the flexible casting belt than in prior continuous casting machines of the same moving mold cross-sectional shape and size. The freezing rate advantageously becomes stabilized at a substantially higher and more uniform rate, the belt flatness becomes stabilized and the cast metallic product is thereby substantially improved both in metallurgy and surface appearance. Also, copper or copper alloy casting belts are used in certain embodiments for enhancing heat-transfer effects and belt flatness. During casting at a given speed, the freezing rate and exit temperature of the metal being continuously cast can be controlled by varying the helium percentage in the gaseous film itself. In twin-belt machines, relative heat-transfer rates into upper and lower belts are controlled by adjusting the relative helium percentages in their respective gas films.

Belt composition for improving performance and flatness of thin

In continuously casting molten metal into cast product by a twin-belt machine, it is desirable to achieve dramatic increases in speed (linear feet per minute) at which cast product exits the machine, particularly in installations where steel cast product is intended to feed a downstream regular rolling mill (as distinct from a planetary mill) operating in tandem with the twin-belt caster. Such high-speed casting produces product with a relatively thin shell and molten interior, and the shell tends to bulge outwardly due to metallostatic head pressure of the molten center. A number of cooperative features enable high-speed, twin-belt casting: (1) Each casting belt is slidably supported adjacent to the caster exit pulley for bulge control and enhanced cooling of cast product. (2) Lateral skew steering of each belt provides an effective increase in moving mold length plus a continuity of heat transfer not obtained with prior art belt steering apparatus. (3) The exiting slab is contained and supported downstream from the casting machine to prevent bulging of the shell of the cast product, and (4) spray cooling is incorporated in the exit containment apparatus for secondary cooling of cast product.

Twin-belt continuous caster with containment and cooling of the exiting

Method and belt composition for improving performance and flatness in

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Burlington, VT, United States of America

J F Wood