US3290741A - Methods of bending casting in a continuous casting process - Google Patents

Description

Dec. 13,

METHODS OF BENDING CASTING IN A CONTINUOUS CASTING PROCESS Filed Nov. 14, 1961 MOLD CASTING C o o l 2 C3 sfiemeHfENme ROLLS 1 O o o Q GUIDE ROLL INVENTOR ERIK ALLAN OLSSON QMJ' ATTORNEYS United States Patent 3,290,741 METHODS OF BENDING CASTING IN A CONTINUOUS CASTING PROCESS Erik Allan Olsson, 66 Zurichstrasse, Kusnacht, Zurich, Switzerland Filed Nov. 14, 1961, Ser. No. 152,161 Claims priority, application Sweden, Nov. 18, 1960, 11,125/ 60 1 Claim. (Cl. 22200.1)

Reference is made to my copending application Serial No. 152,259, filed of even date herewith, now abandoned, and disclosing an apparatus suitable to carry out the method ofthe present invention.

In vertical continuous casting the molten metal is supplied continuously to a cooled vertical open-ended mold, from which the metal which is at least partly solidified to form a solid marginal zone is withdrawn more or less continuously and is passed through a cooling zone wherein solidification of the metal continues at least to an extent such as to allow the casting to be gripped and advanced by means of one or more pairs of driven rolls without the casting being undesirably distorted or deformed by the action of the roll pressure required to achieve the friction necessary to advance the casting. In order to decrease the vertical dimension of the casting installation and to achieve a greater operational reliability, the casting which leaves the mold in a more or less vertical direction is often bent to a horizontal or substantially horizontal direction by means of a pressure roll or other bending means, whereupon the casting is straightened before it is cut to desired lengths. The greater operational reliability resides in the circumstance that failure to cut the continuous casting and operational disturbances in the means for advancing the casting after it has left the mold do not affect the casting process as such, since it is easier to provide sufficient space for advancing an uncut casting than in the case when the casting moves vertically towards a confining floor.

However, the well-known fact that bending can cause cracks or fissures on account of the elongation of the outward side of the bend, limits the possibility of choosing an arbitrarily small bending radius. Apart from the usual visible cracking in the surface area, which is due to the tensile strength of the material being exceeded in the portion thereof which is most subjected to elongation, internal defects may occur in the casting when it is bent on account of the fact that the internal temperature of the casting in particular in the transition zone between solid and fluid material, has not had time to fall to such a level that the material has achieved an appreciable strength. Since different materials, e.g., different grades of steel, behave differently in this respect, a casting machine used to cast several different materials must be constructed with a view to the material which is most subject to cracking. In addition, the size of the casting is, of course, a major factor in the choice of a suitable bending radius. For a constant stress in the surface layer the minimum permissible bending radius increases in proportion to the cross-sectional area of the casting. Considering the fact that certain layers within the casting are particularly sensitive to tension on account of a too high temperature and that these layers approach the centerline of the casting or the neutral line of the bending as solidification proceeds, a smaller bending radius might be permitted if the bendingoperation starts closer to the point of complete solidification.

The knowledge of the strength of various grades of steel at the high temperatures involved here is very limited and the rate of influence of various impurities or alloying additives on the susceptibility to cracking is not completely known. In a general manner it can be said that the stresses which are permitted to appear as a result of the bending of the casting should be kept as small as possible. In no circumstances, the bending radius chosen for the casting should be permitted to result in an elongation of the material at a distance from the neutral line such that the tensile strength of the material at the temperature involved is exceeded.

The novel features that are considered characteristic of the invention are set forth with particularity in the appended claim. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiment when read in connection with the accompanying drawing having a single figure only.

The present invention relates to a method of bending the casting which leaves the mold in a substantially vertical direction, to a substantially horizontal direction with the smallest possible local stresses in the casting and with the smallest possible need of space to carry out the bending operation. The method of this invention comprises carrying out the bending of the casting to the desired substantially horizontal direction progressively or stepwise. Thereby the elongation to which the material in the casting is subjected in the bending method used hitherto, can be reduced considerably, in that the bending is caused to take place progressively or is increased step by step as the temperature of the casting falls and solidification proceeds. In some cases, the casting may obtain a paraboliform bending configuration during passage through the bending means.

In the accompanying drawing is diagrammatically illustrated one embodiment of the method according to the invention described above. The casting is shown as emerging vertically from a mold and being bent in four steps to the horizontal at which point it is straightened by conventional straightening rolls. In the first bending step the roll B with companion roll B being moved to the left, bends the casting through the arc 1 about a fulcrum formed by roll A into a curve having approximately the radius R Roll A is an opposition roll which retains the casting against the fulcrum roll A The companion rolls D D are conventional powered Withdrawal rolls. In the next bending step companion rolls E and E bend the casting about fulcrum roll B through are 2 having approximately the radius R For this bending step rolls A and B are opposition rolls which retain the casting against the fulcrum roll B Roll F next bends the casting through are 3 having substantially the radius R roll B acting as the opposing roll to maintain the casting against fulcrum roll E In the fourth bending step roll F further bends the casting about the fulcrum F through the arc 4 having approximately the radius R roll E acting as an opposing roll to hold the casting against the fulcrum roll F and roll G being merely a guide roll. C -C are thecenters of radii R R respectively.

I claim:

The method of bending a casting which leaves a continuous casting mold, from a substantially vertical direction to a substantially horizontal direction, which comprises performing the bending in a plurality of steps, the amount 3 4 of bending increasing as the temperature of the casting 2,698,467 1/ 1955 Tarquinee et a1 22200.1 falls and solidification thereof proceeds. 2,947,075 8/1960 Schneckenburger et a1.

' 2257.3 X References Cited by the Examiner 5 J. SPENCER OVERHOLSER, Primary Examiner.

UNITED STATES PATENTS WINSTON A. DOUGLAS, MARCUS U. LYONS, WIL- 1,209,039' 12/ 1916 Rowley 2257.2 LIAM J. STEPHENSON, Examiners. 2 264 288 12/1941 Betterton et a1 2257.2

H. W. CUMMINGS, R. A. SANDLER, 2,338,781 1/1944 Porter 22--57.2

Assistant Examiners.

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