GB1577681A - Method of repairing damaged ingot mould handlinmg lugs - Google Patents

Description

(54) METHOD OF REPAIRING DAMAGED INGOT MOLD HANDLING LUGS (71) We, Uss ENGINEERS AND CON SULTANTS, INC. a corporation organized and existing under the laws of the State of Delaware, United States of America, of 600 Grant Street, Pittsburgh, State of Pennsylvania, 15230, United States of America.

(Assignee of PAUL EUGENE HAMILL, ROBERT HENRY KACHIK AND ARTHUR JOIN PIGNOCCO), do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed. to be particularly described in and by the following statement: 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 crapped. 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 consumption cost, i.e. gross cost minus scrap value, of a particular 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 otherwise usable condition, are scrapped prematurely because they have damaged lugs.

According to the present invention, there is provided 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 enclosure around the damaged lug such that the inner surface of the refractory enclosure at least in part defines the surfaces of the eventual repair of the intended lug; depositing a particulate refractory material within the refractory enclosure against a portion of the existing lug not in need of repair such that a cavity is formed within the refractory enclosure adjacent to a damaged surface of the existing lug; depositing an aluminothermic reaction mixture within the cavity formed in the refractory enclosure and over the particulate refractory material; igniting said reaction mixture to cause molten iron and slag to be formed within the refractory enclosure; 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 enclosure, 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 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 engageable 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 refractory enclosure system is placed around the damaged lug 12. The function of the enclosure 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 enclosure system consists of two open-bottom boxes which are preferably fabricated from graphite plates. One box, constituting inner enclosure 14, is fabricated 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 installing graphite insert plates along the side walls and/or end walls of the box.

The height of the inner enclosure 14 is made sufficiently tall to contain the required amount of reaction mixture. A 16-inch-tall enclosure is tall enough to contain the charge for most repairs. However, for ease of handling, it is preferred that two 8-inch-tall enclosures be stacked. In the usual case where even larger charges are required (approaching replacement of a complete lug). three or even four enclosures can be stacked. The walls of the inner enclosure 14 are preferably held together by, for example, screws and/or angle brackets.

The other box, constituting an outer enclosure 16, is fabricated from 1 inch thick, 12-inch high graphite plates and is made oversize to surround the inner enclosure 14 and to provide about a 3-inch-wide space 18 all around between the inner enclosure 14 and the outer enclosure 16. The space between the two boxes is filled with a dry particulate refractory 20, such as sand. The 12-inch-tall outer enclosure 16 is sufficiently tall for use with a 16-inch-tall inner enclosure 14. If a taller inner enclosure is required, thus in turn demanding a taller outer enclosure, one or more additional outer enclosures can be stacked on the first such enclosure. 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 sufficiently long to rest on the short, end walls of the inner enclosure 14. The function of the lid 24 is to conserve heat and minimize splashing during the aluminothermic (ATR) reaction.

It is of course necessary that the enclosures 14 and 16 be suitably sealed to prevent leaks. Prior to placing the enclosures therefore, it is preferred that the inner enclosure 14 is first inverted and a layer of high temperature mortar is applied to the bottom surfaces of the enclosure walls.

The enclosure 14 is then picked up, returned to the upright position, placed to surround the lug 12, and then pressed down to squeeze out any excess mortar. All excess mortar is then removed from the inside of the enclosure. The enclosure 14 is positioned such that one end wall thereof is flush against the tapered undamaged end of the lug 12, and the lug 12 is centred in the enclosure 14 from side-to-side. Any gaps remaining between the enclosure 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 case, the inside surface only of the end wall will contact the mold. This joint must be sealed with a bead of mortar.

The inner enclosure is preferably designed to fit snugly against the sides of a 12-inchwide lug. When repairing 10-inch-wide lugs, two 1-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 alternative method for installing the side insert plates is to position the inner enclosure 14 with one long wall snugly against one side of the lug, such that the enclosure 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 other long graphite wall. The length of the inserts should be about 1!/2 inch shorter than the inside length of the inner enclosure 14 itself to ensure easy insertion.

After buttering the bottom edges of the inserts with mortar, they are simply pressed into place. Any large gaps between the insert ends and main enclosure walls are filled with mortar.

The number and size of end inserts required depends on the length of the lug.

Normally a minimum of about 2 inches of metal sshould 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 enclosure 14 should be 19 inches, and one 2-inch-thick end insert is used appropriately to reduce the inside length of the enclosure. Similarly, when repairing a 14-inch-long lug. the inside length should be 16 inches, and two 2-inchthick and one 1-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 some care must be exercised to avoid getting large amounts of mortar in the repair area. The presence of large amounts of mortar could adversely affect the repair.

If necessary, an extension of the inner enclosure 14 is then installed. After buttering the bottom edges of a similar enclosure 14A with mortar, the additional enclosure is simply stacked on top of the first enclosure 14 and pressed into place. Any remaining gaps between the enclosures are then sealed with additional mortar. No additional inserts are required, since the function of the second enclosure 14A is simply to provide sufficient volume to contain the ATR mixture. The shape of the weld is defined by the bottom enclosure section. If the charge calculation indicates that more than 200 pounds of charge will be required, a third 8-inch-tall inner enclosure should be stacked on top of the first two sections.

Further, the use of even a fourth enclosure section may be desirable to prevent the loss of material from a "boil-over" during reaction.

As previously described, the outer enclosure 16 is designed to surround the inner enclosure 14 and provide a 3-inch-wide space 18 all around, which is to be filled with dry sand or particulate refractory 18. Although the demands on the outer enclosure 16 are not nearly as severe as those on the inner enclosure 14, the outer enclosure 16 must, nevertheless, be sealed tightly against tthe mold surface to prevent leakage of loose sand. Because the bottom edges of the outer enclosure must fit against the mold surface, which is not flat, the use of an enclosure with straight bottom edges would leave large gaps. Accordingly, the bottom edge of one end enclosure 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 enclosure wall is usually more complicated. As previously described, the outside surface of one of the inner enclosure end walls is either substantially flush with the top end of the mold as shown in the drawings or about 2 inches beyond the top end of the mold wall 10 where the mold construction is such that the inside surface only of the enclosure end wall contacts the mold. To provide a 3-inch-wide space this end to accommodate the refractory 20 at, it is necessary to install a bottom in the outside enclosure at this spot.

To this end, a l-inch-thick graphite plate 26 is attached to the underside of the enclosure 16. The plate 26 spans the width of the outer enclosure 16.

After the outer enclosure 16 has been properly positioned, it is sealed to the mold by applying beads of mortar between the bottom edges of the enclosure and the mold surface. If necessary, any very large gaps between tthe enclosure and mold surface can be partially filled with steel shims before the mortar is applied. Thereafter, sand or other particulate refractory 20 is poured into the space 18.

Because contact of the molten, super heated ATR products with easily vaporized materials such as water could produce violent results, the enclosure system may be dried before use. Accordingly, a baking operation is accomplished by using a flame from a natural gas burner. Normally, the inner enclosure 14 is baked for about 30 minutes. The outer enclosure 16 is then baked for about 15 minutes. Finally, the inner esclosure 14 is baked again for an additional 15 minutes.

When a full or nearly full lug is being 'replaced, no additional work on the inner enclosure is required. However, when only a portion of a lug is being replaced as shown in the drawing, 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. To prevent this, a par ticulate 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 the enclosure 14, bound on three sides by the walls of that enclosure 14 and on the fourth side by the damaged surface of lug 12. In some cases it is advisable to use a refractory insert (not shown) spanning the width of the inner enclosure 14 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 mixture required for the repair should be calculated by estimating the volume of metal required and using the relationship 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 dismantling the assembly and repeat ing the procedure. The calculated amount of ATR mixture 32 is then introduced into the enclosure 14 filling the cavity adjacent the damaged lug 12, and of course filling in over sand fill 30. The ATR mixture 32 is typically astoichiometric mixture of granulated iron oxide and aluminum.

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 folowing 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 amount 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 mixture 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 tip 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 seconds or less.

Occasionally, some of the superheated, molten reaction products may boil up over the top of the enclosure system and be lost.

This is particularly likely to happen when large charges are burned. Generally, the loss of material from "boil-over" is negligible. but it can be essentially eliminated, as previously mentioned, by using a sufficient number of inner enclosure sections.

Ideally, the inner enclosure 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, if 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 enclosure 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 enclosure sections 14. The sand 20 will drain from the space 18 between the enclosures during removal of the outer enclosure. Also, care should be exercised during the handling of the outer enclosure sections to ensure that they do not get chipped, cracked or otherwise damaged.

Next, the graphite lid 24 is removed and the inner enclosure sections are successively removed, starting with the top section. The enclosure sections are separated by gently prying at the junctions between them.

Again, care must be exercised to ensure that the enclosures do not get seriously damaged.

Because the bottom enclosure 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 it be partially dismantled before removal. By, for example, removing several screws (not shown). the inner enclosure can be separated into two L-shaped halves, which can be easily removed. The enclosure is then reassembled by simply reinstalling the screws.

All of the enclosure sections are then prepared for the next run by simply chipping away the excess mortar from all the surfaces which must seal against other enclosure sections and/or the mold surface and removing any ATR products which may adhere to the inside walls of the enclosure. Any large gaps, chips, or cracks which may have developed in the enclosures 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 elges of the slag phase with a hammer to loosen it and/ or produce a gap for prying.

The top surface of the metal deposit is usually found to be very 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 and removing excess metal which might prevent proper engagement of the lug by the crane stirrups. Because 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.

WHAT WE CLAIM IS:- 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 enclosure around the damaged lug such that the inner surface of the refractory enclosure at least in part defines the surfaces of the eventual repair of the intended lug; depositing a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. damaged lug 12, and of course filling in over sand fill 30. The ATR mixture 32 is typically astoichiometric mixture of granulated iron oxide and aluminum. 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 folowing 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 amount 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 mixture 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 tip 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 seconds or less. Occasionally, some of the superheated, molten reaction products may boil up over the top of the enclosure system and be lost. This is particularly likely to happen when large charges are burned. Generally, the loss of material from "boil-over" is negligible. but it can be essentially eliminated, as previously mentioned, by using a sufficient number of inner enclosure sections. Ideally, the inner enclosure 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, if 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 enclosure 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 enclosure sections 14. The sand 20 will drain from the space 18 between the enclosures during removal of the outer enclosure. Also, care should be exercised during the handling of the outer enclosure sections to ensure that they do not get chipped, cracked or otherwise damaged. Next, the graphite lid 24 is removed and the inner enclosure sections are successively removed, starting with the top section. The enclosure sections are separated by gently prying at the junctions between them. Again, care must be exercised to ensure that the enclosures do not get seriously damaged. Because the bottom enclosure 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 it be partially dismantled before removal. By, for example, removing several screws (not shown). the inner enclosure can be separated into two L-shaped halves, which can be easily removed. The enclosure is then reassembled by simply reinstalling the screws. All of the enclosure sections are then prepared for the next run by simply chipping away the excess mortar from all the surfaces which must seal against other enclosure sections and/or the mold surface and removing any ATR products which may adhere to the inside walls of the enclosure. Any large gaps, chips, or cracks which may have developed in the enclosures 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 elges of the slag phase with a hammer to loosen it and/ or produce a gap for prying. The top surface of the metal deposit is usually found to be very 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 and removing excess metal which might prevent proper engagement of the lug by the crane stirrups. Because 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. WHAT WE CLAIM IS:-

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 enclosure around the damaged lug such that the inner surface of the refractory enclosure at least in part defines the surfaces of the eventual repair of the intended lug; depositing a

particulate refractory material within the refractory enclosure against a portion of the existing lug not in need of repair such that a cavity is formed within owe refractory enclosure adjacent to a damaged surface of the existing lug; depositing an aluminothermic reaction mixture within the cavity formed in the refractory enclosure and over the particulate refractory material; igniting said reaction mixture to cause molten iron and slag to be formed within the refractory enclosure 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 enclosure the particulate refractory material and the solidified slag to expose the repaired lug.

2. A method as claimed in claim 1 in which the refractory enclosure 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 space is provided between the two graphite frames and a particulate refractory material is deposited within the said space.

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

5. A method of repairing a damaged ingot mold handling lug substantially as hereinbefore described with reference to the accompanying drawing.