US3729049A

US3729049A - Slipping cope assembly

Info

Publication number: US3729049A
Application number: US00154101A
Authority: US
Inventors: R Greenwood; W Tiley
Original assignee: Steel Corp
Current assignee: United States Steel Corp
Priority date: 1971-06-17
Filing date: 1971-06-17
Publication date: 1973-04-24
Anticipated expiration: 1990-04-24

Abstract

In the conventional casting of long rolls, contraction strains resulting in tears are avoided by use of a movable sleeve which is accurately machined to slide into the chill. Subsequent to pouring of the metal, supports holding the sleeve are removed and the sleeve then follows the shrinking metal, thus permitting the solidifying metal to contract without tearing. The subject invention provides an improved slipping cope assembly, which avoids contact with the solidifying metal and is readily adaptable to chills of varying diameters.

Description

United States Patent 1191 Greenwood et a1.

3,72 fl49 Apr. 24, 1973 SLllPPING COPE ASSEMBLY Inventors: Robert P. Greenwood; William L.

Tiley, both of Canton, Ohio United States Steel Corporation, Pittsburgh, Pa.

[731 Assignee:

Filed: June 17, 1971 Appl. No.: 154,101

11.5. c1 ..164/352, 249/198 1m. 01. ..B22d 15/02 Field 61 Search 164/127, 137, 342, 164/352, 366, 359, 363, 364, 122, 353, 356, 3.67, 373; 249/82, 105,106,111, 112, 19s,

[56] References Cited I UNITED STATES PATENTS Lobdell ..249/ l 98 Johns 164/352 1,500,732 7/1924 Howard 1 164/342 X 3,100,921 8/1963 Marie ..249/197 3,208,l l6 9/1965 Gathmann 164/125 Primary Examiner.l. Spencer Overholser Assistant Exdminer-John S. Brown Att0rneyArthur J. Greif ABSTRACT 1 Claim, 3 Drawing Figures Patented A ril 24, 1973 F/ G. 2. PRIOR ART SLIPPING COPE ASSEMBLY This invention relates to an improved method and apparatus for casting large metal articles and more specifically, relates to an improved slipping cope assembly for the casting of iron base rolls.

Of all the steel ingots produced today, greater than 99 percent are processed further by being passed through either cast iron or cast steel rolls. Iron base rolls differ from steel base rolls principally in their carbon content, the steel roll containing up to about 2.5 percent carbon, whereas the iron roll contains carbon in greater amounts. Both types of rolls are produced by the bottom pour swirl method, with the mold in the vertical position. The hot metal enters at the bottom of a dragneck through a gate which is placed tangentially to the periphery of the neck. This placement imparts a vigorous spin or swirl to the metal as it enters the mold. The spinning action throws the denser, purer metal to the surface, thus ensuring a cleaner working face. The less dense, dirtier metal is concentrated in the center of the rising metal and is subsequently carried to the top of the sink head. lronbase rolls are cast in a chill-type mold, in which the neck is cast in sand, but the body of the roll is formed by a heavy-walled cast iron cylinder called a chill. The chill, as its name implies, serves to cool the molten iron quickly, thereby producing a hard surface containing a minimum of graphite.

The metal is poured rapidly so as to set up the vigorous spin referred to above and to avoid steep thermal gradients in different parts of the roll, thereby preventing hot tears at such gradient points. Due to the enhanced cooling, effected by the metal chill, the molten metal solidifies more rapidly in that portion of the mold. This solidification results in the contraction of the casting, which in turn exerts a downward tension on the metal in the cope, still held within the sand portion of the mold and frequently results in hang cracks or tears and a defective casting. This defect is especially prevalent in long castings since the amount of shrinkage, or downward movement of the metal, is directly proportional to the length of the casting. To avoid such excessive strains on long rolls, the art has employed a sliding sleeve which is machined to fit inside the top of the chill. Set pins are employed to hold this sleeve in position, and are removed prior to initiation of solidification, so that the sleeve may follow the shrinking metal and avoid such hang cracks in the casting. This method has been found to be unsatisfactory since the tears are, in a number of instances, replaced by chill cracks," caused by the deep chill penetration at the point at which the roll body is in contact with the sliding sleeve. In addition, such sleeves are expensive, since they necessitate the use ofa different inner sleeve for each of the various diameters of roll bodies being cast and further require accurate machining to provide a close tolerance slip fit. Equally important, even when the extra expense is taken, the tolerances are rarely accurate enough to provide a fit which will prevent the liquid metal from rising into the area of misfit between the chill and the sleeve. This invention is therefore directed to a slipping cope assembly which avoids direct contact with the roll body and is adaptable to roll bodies of varying diameters. The improved assembly is also adapted to facilitate assembly of the entire mold in a manner not provided by the prior art.

These advantages as well as other objects of the invention will be better understood when read in conjunction with the appended claims and following description and drawings in which:

FIG. 1 is a cross-section of a conventional roll mold;

FIG. 2 shows a standard sliding sleeve assembly in cross-section; and

FIG. 3 shows the movable sleeve assembly of this invention in cross-section.

Referring to FIG. 1, in conventional roll casting, the liquid metal is poured through spout l and into gate 2, which is set tangential to the periphery of neck 3. The hot metal rises through the mold and contacts chill 4, promoting a hard, refined outer skin at the contact areas. The metal thereafter rises through neck 5 and into the sinkhead area 6. As the molten metal in chill 4 solidifies, it contracts in both diameter and length. The

contraction in length exerts a downward tension on the partially solidified metal in neck 5, which is held within the sand 7 in the cope 8. Unable to effectively move, the metal in the neck of the casting tends to tear at various points 9, thus producing a hang crack.

To avoid such contraction strains on long rolls, the art has employed a sliding sleeve system as shown in cross-section in FIG. 2. The sleeve 11 is machined to provide a close fit with the inside of the chill 4. Subsequent to pouring of the casting, support members 12, holding this sleeve in position are removed and the sleeve is then free to follow the shrinking metal, thereby avoiding such hang cracks. In this system, the end of the cast roll body is exposed to metal contact (that of the sliding sleeve) on both the vertical and horizontal planes, this contact causing an undesirable rapid heat loss and deep chilling which may result in a chill crack.

A further disadvantage in employing the above sliding sleeve system is encountered during assembly of the mold itself. Assembly of the entire mold such as is shown in FIG. 1 is generally accomplished in the following manner. The roll pattern and flask are set on a base plate and aligned by the use of predrilled holes. Depending on the particular taper of the pattern, sand is then rammed with the mold in either the upright or inverted position. After this ramming, the mold assembly is inverted and the pattern is drawn. The sand mold is finished manually by troweling and is then coated with a refractory wash to avoid burn on of the molten metal. The coated mold is then baked to remove moisture and to set up the mold properties. Subsequently, the mold is removed from the baking oven and the ingate assembly, drag and chill are placed in position in the pouring pit. The cope and sliding sleeve assembly are then carried by crane and placed on top of the chill 4 (as shown in FIGS. 1 and 2). It may, therefore, be seen that the sleeve assembly must be turned downwardly prior to being placed on top of the chill. Since there is no barrier to protect the sand at the lower portion 13 of the assembly, there is a tendency for at least a portion of this sand to fall and thereby result in a defective mold.

The means by which the slip cope system of this invention overcomes the various disadvantages of the above sleeve assembly may be seen in FIG. 3. A cylinder 11a (with flanges for attaching other flask elements) is machined to fit within a guide cylinder 14, so

that the entire assemblage above 11a will slide downward as the metal in the cavity cools and shrinks. Here, however, the bottom of the sleeve is shorter so that the end of the roll is molded against sand, not

cope.

We claim: 1. In a mold for casting ferrous base rolls which comprises a flask system including a chill member, and an metal, thereby eliminating the danger of a resultant upper cope member for containing a bonded sand chill crack. It is desirable that the inner diameter of guide 14 be as large as that of the largest roll being cast, thereby overcoming the necessity of machining a different sliding cylinder for every diameter chill.

The initial assembly of a mold utilizing the above slipping cope is accomplished in the same manner as in the prior art, up to the point at which the drag and ingate assembly are placed in the pouring pit. Here, however, the cope assembly (including the slipping portion thereof) is inverted on the set up floor, so that the unrestricted portion of sand at 13 points upwardly. The chill 4 is then placed on top of this assembly and clamped to it. The cope-chill unit is then rolled over and placed upright on the drag assembly in the pit. In this case, the chill 4 itself aids in support of the sand and thereby prevents it from falling when the cope system is in the upright position. As in the prior art method, subsequent to pouring, the supports 12 holding the slipping cope in position, are removed and the cope is then free to exert pressure on the sand to follow the contracting metal. It has been found that the weight of the cope above is often insufficient and an additional force (such as weights or jacks) may be employed to aid the downward movement of the slipping cylinder. Such devices are readily adaptable to the instant slip body, said sand body having a generally cylindrical cavity in which the roll necks are formed;

the improvement which comprises a lower cope system interposed between said chill and said upper cope members, which consists of a guide cylinder and a movable cylinder adapted to fit slidingly within said guide cylinder;

said guide cylinder having an inner diameter equal to or greater than that of said chill member and being of a height which permits the interposition between said chill and said upper cope a support member and a flange joined to said movable cylinder;

said flange serving to sustain a support member which is interposed between said flange and said guide cylinder to restrict the downward motion of said movable cylinder, the inner diameter and height of said movable cylinder being such as to prevent direct contact with said cavity; whereby subsequent to the pouring of molten metal to form said iron roll, said support member may be removed so as to permit said movable cylinder to exert pressure on the portion of the sand body surrounding said cavity.

Claims

1. In a mold for casting ferrous base rolls which comprises a flask system including a chill member, and an upper cope member for containing a bonded sand body, said sand body having a generally cylindrical cavity in which the roll necks are formed; the improvement which comprises a lower cope system interposed between said chill and said upper cope members, which consists of a guide cylinder and a movable cylinder adapted to fit slidingly within said guide cylinder; said guide cylinder having an inner diameter equal to or greater than that of said chill member and being of a height which permits the interposition between said chill and said upper cope a support member and a flange joined to said movable cylinder; said flange serving to sustain a support member which is interposed between said flange and said guide cylinder to restrict the downward motion of said movable cylinder, the inner diameter and height of said movable cylinder being such as to prevent direct contact with said cavity; whereby subsequent to the pouring of molten metal to form said iron roll, said support member may be removed so as to permit said movable cylinder to exert pressure on the portion of the sand body surrounding said cavity.