CA1078133A - Method of repairing damaged ingot moid handling lugs - Google Patents

Abstract

METHOD OF REPAIRING DAMAGED
INGOT MOLD HANDLING LUGS
ABSTRACT OF THE DISCLOSURE
A method for repairing damaged ingot mold handling lugs wherein a refractory perimeter is placed around the damaged lug and sand is deposited against the undamaged surfaces of the existing lug so that a cavity is formed adjacent to the damaged surface of the lug. An aluminothermic reaction mixture is then placed within the perimeter and ignited causing molten metal to fill and solidify within the cavity. Finally, the refractory perimeter, sand and reaction product slag are removed, and the deposited metal shaped as desired.

Description

~17~l33 The present invention relates to the repair of damaged ingot mold handling lugs.
Generally, ingot molds are equipped with lugs for engagement by crane stirrups to permit handling of the molds.
Because the lugs sometimes known as ears, protrude from the body of the mold, they are prone to damage during handling. Further, new molds may be scrapped in the foundry because they were cast with unsatisfactory lugs or the lugs were damaged during foundry operations. In any event, if a mold lug is unusable, the lug must be repaired or the mold must be scrapped. Although, several methods for repairing mold handling lugs have been developed, these known methods are expensive and/or impractical.
That is, the repair cost may approach or even exceed the con-sumption cost, i.e. gross cost minus scrap value, of a particu-lar mold or the repair procedure may require the use of special materials, such as a ready supply of coke-oven gas for preheating and/or the services of highly skilled workers. Because of these deficiencies in known lug-repair techniques, lug repair is not - widely practiced. Consequently, many molds, which are in other-wise usable condition, are scrapped prematurely because they have damaged lugs.
Ac~ording to the present invention, there is provided a method of repairing damaged ingot mold handling lug comprising placing the ingot mold on its side such that the damaged lug to be repaired is in an uppermost position; placing a refractory ~l~71~133 perimeter around the damaged lug such that the inner surface of the refractory perimeter defines the perimeter of the intended lug; depositing a particulate refractory material within the refractory perimeter against a portion of the existing lug not in need of repair such that a cavity is formed within the refractory perimeter adjacent to a c~maged surface of the existing lug: depositing an aluminothermic reaction mixture within the cavity formed in refractory perimeter and over the particulate refractory material; ignit.ing said reaction mixture to cause molten iron and slag to be formed within the refrac-tory perimeter; allowing the molten metal and slag phases to ; separate such that the metal phase settles to the bottom against the damaged portion of the existing lug, and the slag phase forms ~hereover and over the particulate refractory material; allowing the two molten phases to cool and ~olidify; and removing the refracto.ry perimeter, the particulate refractory material and the solidified slag to expose the repaired lug.
The invention is further described, by way of example, with reference to the accompanying drawing which is a sectional side view of a portion of an ingot mold having the proper apparatus and materials in place for the practice of the invention.
In the preferred practice of this process, an ingot .
mold having a damaged lug is placed on its side with the damaged lug in the uppermost position. Reference to the figure illustrates, in section, a portion of the ingot mold wall 10 and the damaged ~078133 lug 12. A typical ingot mold handling lug has a sloping surface (shown in the drawing) extending from the top end of the mold wall to a downwardly projecting lobe which is engagable by a crane stirrup. The lobe has been broken off the damaged lug 12 shown in the drawing.
` Any large protrusions located immediately adjacent to the damaged lug 12 should be removed prior to repair by scarfing or grinding to facilitate positioning and sealing of the necessary apparatus as described below. Ideally, the mold should be placed so that the mold wall 10 is level. However, slight inclinations from end-to-end and/or side-to-side of up to about 10 degrees can be tolerated.
When the ingot mold is positioned as desired and cleaned of protrusions and foreign matter, a rectangular refrac-tory perimeter is placed around the damaged lug 12. The function of the perimeter system is to serve first as a container for aluminothermic reaction (ATR) mixture and subsequently as a mold for the ATR molten metal product. The perimeter system consists of two open-bottom boxes which are preferably fabri-cated from graphite plates. One box, inner perimeter 14, isfabricated preferably from 2-inch-thick graphite plates, and its inside dimensions are designed so that it fits around the largest common lug typically 12 inches by 17 inches.
Shorter and~or narrower lugs can be accommodated by simply install-~g78~L33 ing graphite insert plates along the inside walls and/or endwalls of the box. The height of the inner perimeter 14 is mad~ sufficiently tall to contain the required amount of reaction mixture. A 16-inch-tall perimeter is tall enough to contain the charge for most repairs. However, for ease of handling, it is preferred that two 8-inch-tall perimeters be stacked. In the usual case where even larger charges are required (approaching replacement of a complete lug), three or even four perimeters can be stacked. The walls of the perimeter 14 are preferably held together by, for example, screws and/or angle brackets.
The other box, the outex perimeter 16, is fabricated from 1 inch thick, 12-inch high graphite plates and is made oversize to curround the inner perimeter 14 and to provide about a 3-inch-wide space 18 all around between the perimeter 14 and 16. The space 16 between boxes is filled with a dry particulate refractory 20, such as sand. The 12-inch-tall outer perimeter 18 is sufficiently tall for use with a 16-inch tall inner perimeter 16~ If a taller inner perimeter is required, one or 20 more additional outer perimeters can be stacked on the first perimeter. Finally, a piece of graphite plate having a hole 22 drilled through its thickness at about midpoint, is used as a lid 24. The lid 24 must be sifficiently long to rest on the shorter walls of the inner perimeter 14. The function of the lid 3L~78~L33 24 is to conserve heat and minimize splashing during the ATR
reaction.
It is of course necessary that the perimeters 14 and 16 be suitably sealed to prevent leaks. Prior to placing the perimeters therefore, it is preferred that the inner perimeter 14 is first inverted and a lyaer of high-temperature mortar is applied to the bottom sur~aces of the perimeter walls. The perimeter 14 is then picked up, returned to the upright position, placed to su~round the lug 12, and then pressed down to squeeze out any excess mortar. All excess mortar is then removed from the inside of the perimeter. The perimeter 14 is positioned such that one end wall of the perimeter is flush against the tapered undamaged end of the lug 12, and the lug 12 is centered in the perimeter 14 from side-to-side. Any gaps remaining between the perimeter 14 and the mold surface are then filled by applying additional mortar as needed. Some molds are constructed such that the tapered end of the lug coincides with the end of the mold. In this casel only the inside surface of the end perimeter wall will contact the mold. This joint must be sealed with a bead of mortar.
The inner perimeter is preferably designed to fit snugly against the sides of a 12-inch-wide lug. When repairing 10-inch-wide lugs, two l-inch-thick graphite plates (not shown) are inserted, one on each side of the lug; and when repairing 8-inch-wide lugs, two 2-inch-thick graphite plates are inserted. An ~7t3~33 alternative method for installiny the side insert plates is to position the main perimeter such that one long perimeter wall is snugly against one side of the lug, such that the perimeter is not centered. The required number and thickness of graphite plates is then inserted in the gap between the other side of the lug and the othex long graphite wall. The length of the inserts should be about l/2 inch shorter than the inside length of the main perim-eter to ensure easy insertion. After buttering the bottom edges of the inserts with mortar, they are simply pressed into place~
10 Any large gaps between the insert ends and main perimeter walls are filled with mortar.
The number and siæe of end inserts required depends on the length of the lug. Normally a minimum of about 2 inches of metal should be added to the working end of a lug in addition to the metal required to restore the lug. Thus, for a 17-inch-long lug, the inside length of the perimeter should be l9 inches, and One 2-inch-thick end insert is used to reduce the inside length of the main perimeter to this length. Similarly, when repairing a 14-inch-long lug, the inside length should be 16 inches, and 20 two 2-inch-thick and one l-inch-thick inserts are required. In the case where both side and end inserts are needed, the end inserts should be installed first because the side inserts would then press against the end inserts and preclude the possibility of their falling in on the repair area. The end inserts are installed in the same manner as the side inserts, except that ~8~33 some caremust be exercised to avoid getting large amounts of mort~r in the repair area. The presence of large amounts of mortar could adversely affect the repair.
I~ necessary, an extension of the inner perimeter 14 is then installed. After ~uttering the bottom edqes of a similar perimeter 14A with mortar, the perimeter is simply stacked on top of the first perimeter 14 and pressed into place. Any re-maining gaps between perimeters are then sealed with additional mortar. No additional inserts are required, since the function of the second perimeter 14A section is simply to provide suffi-cient volume to contain the ATR reaction mixture. The shape of the weld is defined by the bottom perimeter section. If the charge calculation indicates that more than 200 pounds of charge will be required, a third 8-inch-tall inner perimeter should be stacked on top of the first two sections. Further, the use of even a fourth perimeter section may be desirable to prevent the loss of material from a "boil-over" during reaction.
As previously described, the outer perimeter 16 is designed to surround the inner perimeter 14 and provide a 3-inch-wide space 18 all around, which is to be filled with dry sand orparticulate refractory 18. Although the demands on the outer perimeter 16 are not nearly as severe as those on the inner perimeter 14, the outer perimeter 16 must, nevertheless, be sealed tightly against the mold surface to prevent leakage of loose sand.

1~71~33 Because the bottom Pdges of the outer perimeter must fit against the mold surface, which is not flat, the use of a perimeter with straight bottom edges would leave large gaps. Accordingly, the bottom edge of one end perimeter wall is contoured to the approximate curvature of most mold surfaces. The side walls generally fit reasonably well and no contouring is required. The fit of the remaining end perimeter ~all is usually more compli-cated. As previously described, the outside surface of one of the inner perimeter end walls is either substantially flush with the top end of the mold or about 2 inches beyond the top end of the mold wall 10. To provide a 3-inch-wide space 20 at this end, it is necessary to install a bottom in the outside perimeter at this spot. To this end, a l-inch-thick graphite plate 26 is attached to the underside of the perimeter 16. The plate 26 spans the width of the outer perimeter 16.
After the outer perimeter 16 has been properly positioned, the perimeter is sealed to the mold by applying beads of mortar between the bottom edqes of the perimeter and the mold surface.
If necessary, any very large gaps between the perimeter and mold surface can be partially filled with steel shims before the mortar is applied. Thereafter, sand or other particulate r~frac-tory 20 is poured into the space 18.
Because contact of the molten, superheated ATR reaction products with easily vaporized materials such as water could produce violent results, the perimeter system may be dried before _ g ~

1(~7~ 3 use. Accordingly, a baking operation is accomplished by using a flame from a natural gas burner. Normally, the inner perimeter 16 is baked for about 30 minutes. The outer perimeter 18 is then baked for about 15 minutes. Finally, the inner perimeter 16 is baked again for an additional lS minutes.
When a full or nearly full lug is being replaced, no additional work on the inner perimeter 16 is required. However, when only a portion of a lug is being replaced as shown in the figure, some means must be used to prevent deposited metal from collecting at the undamaged tapered end of the lug 12. Any metal added to the tapered end of the lug is wasted and may have to be burned off. Th prevent this, a particulate refractory such as sand 30 is poured on top of the tapered end of the lug until the sand level is about flush with the thickest part of the undamaged section of lug 12. Care must be exercised to ensure that no sand accumulates on the damaged surface of the lug.
Hence, a single cavity results within perimeter 14, bound on three sides by the walls of perimeter 14 and on the fourth side by the damaged surface of lug 12. In some cases it is advisable to use a refractory in~ert (not shown) spanning the width of the inner perimeter to serve as a sand barrier. This will permit sand 30 to be poured to a greater depth without the risk of sand accumulating on the damaged surface of the lug.
The weight of ATR reaction mixture required for the ,:

~7~33 repair should be calculated by estimating the volume of metal required and using the relati~nship that 1 pound of charge will yield about 2 cubic inches of metal. This estimate should be deliberately on the high side, since excess metal can be removed, but additional metal can be added only after dismantiling the assembly and repeating the procedure. The calculated amount of ATR mixture 32 is then added within perimeter 14 filling the cavity adjacent to damaged lug 12, and of c~urse filling in over sand fill 30. The ATR mixture 32 is typically a stoichiometric mixture of granulated iron oxide and hluminum.
The graphite plate lid 24 is then placed on top of the inner perimeter 14. A special ignition device may be installed in the lid using the following procedure (not shown): A small sheet of aluminum foil is pressed into the ignition hole 22 in the lid 24 to form a small cup. The resulting cup is then filled with reaction mixture and a small am~unt of primer mixture is then sprinkled on top of the charge pile. Typically, primer mixtures consist of 90~ barium peroxide and 10% aluminum. The primer mix-ture ignites easily when contacted by a flame from a burning fuse.
This reaction, in turn, ignites the charge material in the aluminum cup. When the charge in the cup burns through the aluminum cup, the hot reaction products fall on top of the main charge and ignite it.
Once the ATR mixture 32 is ignited its burn will gradually increase in intensity, reaching its peak in about 30 8~L33 seconds or less. Occasionally, some of the superheated, molten ATR reaction products may boil up over the top of the perimeter system and be lost. This is particularly likely to happen when large charges are burned. Generally, the 105s of material from "boil-over" is negligible, but it can be essentially eliminated, as previously mentioned, by using a sufficient num~er of inner perimeter sections. Ideally, the inner perimeter should extend about 12 inches above the top surface of the charge.
After ignition of ATR mixture 32, the assembly is allowed to stand, undisturbed, until it is cool enough to permit work thereon. Usually it is convenient to cool the assembly overnight. However, i~ such a delay cannot be tolerated, the assembly can be dismantled after about 1 hour, provided the workers are equipped with heat-resistant safety gear.
The outer perimeter 16 is removed first, working from top to bottom, by simply prying the sections loose from each other and then from the mold surface and lifting them up over the inner peri~eter sections 14. The sand 26 will drain from the ` space 18 between perimetersduring removal of the outer perimeter.
Also, care should be exercised during the handling of the outer perimeter sections to ensure that they do not ge~ chipped, cracked or otherwise damaged.
Next, the graphite lid 24 is removed and the inner perimeter sections are successively removed, starting with the top section. The perimeters ar~ separated by gently prying at the junction between perimeters. Again, care must be exercised to ensure that the perimeters do not get seriously damaged. Because the bottom perimeter section 14, which contains the bulk of the products from the reaction, usually cannot be easily removed by simply prying it loose from the mold surface, it is preferred that the perimeter section be partially dismantled before removal.
By, for example, removing several screws, the perimeter can be separated into two L-shaped halves, which can be easily removed.
The perimeter is then reassembled by simply reinstalling the screws. All of the perimeter sections are then prepared for the next run by simply chipping away the excess mortar from all the surfaces which must seal against other perimeters and/or the mold surface and removing any ATR reaction products which may adhere to the inside walls of the perimeter. Any large gaps, chips, or cracks which may have developed in the perimeters during the repair, should be filled with mortar.
The ATR slag phase, which forms on top of the metal deposit, can normally be removed by prying with a chisel or crowbar at the junction between the slag phase and the top surface of the metal deposit. Normally, the slag phase comes loose in one large piece. In some cases, the slag phase may adhere fairly strongly and it might be necessary to strike the edges of the slag phase with a hammer to loosen it and/or produce a gap for prying.

~'78~33 The top surface of the metal deposit is usually found to be vary rough and may contain pieces of entrapped slag. There is no need to painstakingly remove all slag, since its presence does not interfere with the performance of the repaired lug.
If necessary the repaired lug is then trimmed to restore it to the general shape and position of a normal lug. This operation need not be painstaking and should consist primarily of reshaping the working end of the lug and removing excess metal which might prevent proper engagement of the lug by the crane stirrups. ~ecause the composition of the deposited metal is that of steel rather than mold iron, the lug can be quickly and easily trimmed using a conventional burning torch~ In some situations the repaired lug may be suitable for use as cast without trimming or shaping.

Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE AS FOLLOWS:

1. A method of repairing a damaged ingot mold handling lug comprising placing the ingot mold on its side such that the damaged lug to be repaired is in an uppermost position; placing a refractory perimeter around the damaged lug such that the inner surface of the refractory perimeter defines the perimeter of the intended lug; depositing a particulate refractory material within the refractory perimeter against a portion of the existing lug not in need of repair such that a cavity is formed within the refractory perimeter adjacent to a damaged surface of the existing lug; depositing an aluminothermic reaction mixture within the cavity formed in refractory perimeter and over the particualte refractory material; igniting said reaction mixture to cause molten iron and slag to be formed within the refractory perimeter;
allowing the molten metal and slag phases to separate such that the metal phase settles to the bottom against the damaged portion of the existing lug, and the slag phase forms thereover and over the particulate refractory material; allowing the two molten phases to cool and solidify; and removing the refractory perimeter, the particulate refractory material and the solidifed slag to expose the repaired lug.

2. A method as claimed in claim 1 in which the refrac-tory perimeter consists of a rectangular graphite frame, and including the step of sealing said frame against the side of the ingot mold with a high temperature mortar.

3. A method as claimed in claim 2 in which a second rectangular graphite frame is placed around the first graphite frame such that a perimeter space is provided between the two graphite frames and a particulate refractory material is deposited within the perimeter space.

4. A method as claimed in any one of claims 1 to 3 in which a cover plate is placed over said refractory perimeter, said plate having a small hole through which the aluminothermic reaction mixture is ignited.