US2719208A - Wrapped alloy core electrode - Google Patents

Description

p 1955 R. K. PlTLER 2,719,208

WRAPPED ALLOY CORE ELECTRODE Filed April 24, 1952 Fig. /0

IN VEN TOR. Richard K. Pit/er H/S A T TORNE Y5 United States Patent WRAPPED ALLOY CORE ELECTRODE Richard K. Pitler, Menands, N. Y., assignor t0 Allegheny Ludlurn Steel Corporation, Brackenridge, Pa., a corporation of Pennsylvania Application April 24, 1952, Serial No. 284,124

11 Claims. (Cl. 219-8) This invention relates to making compacted consumable electrode sticks of a base metal and alloy metal wherein the metal content is accurately proportioned and so arranged as to provide melted homogeneous alloy ingots of titanium or zirconium base metal.

Electrode sticks are fed into a melting crucible and thus must have a suflicient strength and hardness to be pressure fed without breakage, and be capable of being effectively supplied with melting current of one potential while they are being fed. The lower end of the electrode stick then forms a melting arc with metal in the crucible and in this manner, an ingot may be built up by progressively melting down the stick as it is fed. Metals of the base type here involved are known to be extremely sensitive to contamination from gases normally found in the atmosphere, such as nitrogen, oxygen and those containing carbon. For this reason, it is important to exclude contaminating gases or substances during the melting operation and to feed the electrode stick while at the same time preventing contamination.

Although titanium or zirconium sticks can be pressed out for such a purpose due to the characteristic of their particles to form a good mechanical bond under pressure, there has been a definite problem involved in endeavoring to provide alloying metals or materials in such sticks in requisite proportioned amounts, due to the fact that metals such as iron, nickel, manganese, magnesium, molybdenum, tungsten, chromium, cobalt, etc., in particle, powder, or granule form have little or no adherency with respect to each other or with respect to the base metal. In fact, they tend to flow through any crevices or interstices. It thus appears that the strength of an electrode stick or member containing alloying metals or materials must be dependent on the base metal, itself.

Further, it has been necessary to, in some way, enclose the alloying metals within the base metal, so that the former will not be lost and will retain its position during the feeding operation and during the progressive melting down of the end of the stick. The relatively lower melting points of the alloying materials must also be taken into consideration, as well as the need to provide a stick having an effective electrical conductivity. Hot fabrication of the electrode stick is not desirable because of the sensitivity of the base metal to contamination. A further factor is involved in providing a melt that is highly homogeneous and which will at the same time have the requisite proportioned amounts of the alloying materials.

It has thus been an object of my invention to provide a new and improved process for making consumable electrode sticks of titanium or zirconium base metal and alloying materials;

Another object has been to provide an arrangement for fabricating electrode sticks which will meet the factors or problems involved;

A further object has been to increase the effective strength of the electrode and particularly its electrical conductivity and to make it in such a way that it will utilize arc current in a more effective manner.

length of the stick and place it on a set of scales.

These and many other objects of my invention will appear to those skilled in the art from the following description.

In the drawings, Figure 1 is an end section in elevation through a forming die or mold assembly and illustrating a step in my forming or fabricating procedure wherein a layer of base metal material is provided;

Figure 2 is a longitudinal section in elevation of the assembly of Figure 1;

Figure 3 is a perspective view showing another step in my procedure where an aluminum sheath is laid out to receive alloying material;

Figures 4 and 4A are perspective views of assembled sheathed alloy cores illustrating a step of my procedure;

Figures 5 and 6 are, respectively, end and side sections in elevation of the mold assembly of Figure 1, but illustrating a further step in my procedure wherein the sheathed core of Figure 4 is placed in position on a preliminary or bottom layer of base metal;

Figures 7 and 8 are, respectively, end and side view in elevation of the mold assembly of Figure l, but illustrating a further step of my procedure wherein a top layer of base metal material has been added;

Figures 9 and 10 are, respectively, end and side sectional views in elevation illustrating a step of pressingout the materials assembled in the manner shown in Figures 7 and 8;

Figure 11 is a perspective side view of a completed electrode stick or member fabricated in accordance with my invention.

In carrying out my procedure, I give first consideration to the alloy content which is desired in the final ingot. From this, I then determine the requisite proportionate weight amounts of the base metal and the alloying material on the basis of the size of the electrode stick which is to be produced. Knowing the desired size of the stick, for example, 1.5 by 3 inches in cross-section, I determine the proportionate amount of alloying material which is needed per unit of length to provide the requisite content in the final ingot. Such determination is, of course, multiplied by the total length of the stick which may be 12 inches or more, for example. I then take an aluminum foil of a length substantially corresponding to the desired The alloy material is then added in the requisite weight quantity along a central longitudinal axis of the foil and the foil is then rolled or wrapped about the alloy material to form an enclosing sheath about an alloy core of substantially uniform cross-section lengthwise. In this connection, the ends of the foil may be lapped over and the excess length of the edges cut 011'. The use of aluminum foil (highly electrically conductive) is important because of its ease of wrapping, and because I have found that it is not deleterious as a small percentage impurity in the melt. In this connection, I find that aluminum foil of about .001 to .005 inch in thickness may be successfully employed and will produce in the melt an aluminum content of more than about .01 to .l0%. As an optimum, a thickness of foil of about .004 to .002 inch is highly satisfactory (present foil in use is about .002 inch).

The alloy core as thus wrapped is then placed centrally between upper and lower enclosing layers of the base metal material which, of course, may also be weighed out to maintain the requisite proportions. it is necessary to have the sheathed core of a slightly lesser length than that of the stick, itself, or in other words, of the base metal layers; in this connection, about A to of an inch at each end is sufficient. This small end allowance does not upset the proportionate relationships of the metals from an overall standpoint of the complete stick and the amount of base metal at the ends is suflicient to provide a thin, adherent, closing and supporting layer for the core. After the materials have been assembled in the above manner, they are then subjected to compression to produce the desired shape of stick and to compress the base metal particles into a highly effective mechanical adherency. ,This operation is preferably carried out at room temperature, although the base metal may be heatedup to temperature of not more than 800 F. to reduce the overall pressure required. A relatively high unit pressure of about 1 to 25 tons per square inch is needed; 6 to 8 tons is a good optimum. The base metal material of titanium or zirconium may be in the form of powder, grain, particles, or sponge such as produced by a halidereducing operation. Particles which will pass a No. 2 mesh are highly satisfactory. Such metals are crystalline in nature and when their particles are compacted under sufiicient pressure, have a high mechanical adherency. The base metal should be relatively pure and it is desirable to provide alloying metals that are of relatively high purity to avoid contamination.

The resultant product which may be of any cross-sectional shape, although a rectangular shape has been shown, will not only withstand the mechanical stress and strains of a feeding operation and of any contact means for applying electrical current thereto, but is also believed to have a higher efiiciency of electrical conductivity due to the presence of the aluminum wrapper. As long as the core of the electrode (as completed) has a cross-sectional area of not greater than half the total cross-sectional area of base metal, the strength of the electrode stick has been found to be sufficient. The foil wrapper in addition to facilitating the measuring and insertion of the alloy metal which usually is in powdered form and may be in small particle or granular size, eliminates any sifting through of the alloy metal during the fabricating operation of the stick and maintains the alloy material in an accurately proportioned and aligned relationship with respect to the base metal material along the full length of the stick.

Although, it is not definitely known what all takes place to produce the improved results, it appears that the foil, as used, eliminates hot spots and minimizes heatingup of the electrode adjacent the current supply means thereto, such as shoes or rollers, and also provides a better type of melting-down action at the end of the electrode which is arcing within the crucible (produces a highly efiicient, power saving, arcing effect). In accordance with my theory, current flows down the sleeve-like center portion of the stick due to the high conductivity of the foil wrapper and then, concentrates the arc tufts between such foil wrapper and the outer edges of the base metal portions of the stick end. This appears to produce a somewhat annular type of tuft arrangement which concentrates the higher temperature portions of the melting are on the base metal. Thus, in accordance with my theory, the result is that the alloy metal in the center of the end is melted at substantially the same rate as the base metal, unmelted portions of the titanium are avoided, and a fully homogeneous mixture of the metals is effected in buildingup the ingot.

Consumable electrode sticks may be produced in accordance with my invention of any desired size or diameter or may be made in relatively smaller sizes and then secured together in an abutting relationship to form an integral group of sticks. Even in the latter case, the improvement in homogenity of the melt is apparent. If it is desired to provide alloying gases in relatively small proportioned amounts in the ingot, such as nitrogen and oxygen, I have also successfully utilized alloying metal oxide and nitride particles in the wrapped core.

Referring to Figures 1 and 2 of the drawings, I have shown a mold or die box 11 having a false or removable bottom 10 and a bottom or preliminary layer of base metal material a. In Figure 3, I have shown how alloy material c may be placed upon an aluminum foil [2 for weighing and subsequent wrapping. In Figures 4 and 4A, I have shown a wrapped or sheathed core I) which as shown in Figures 5 and 6, is laid on the lower or preliminary base metal layer a with its ends spaced from opposite end walls of the mold box 11. The shape of Figure 4 is preferred where the electrode is to have a cylindrical or substantially square crosssection and may be flattened, as shown in Figure 4A, where the electrode is to have a more rectangular cross-section.

In Figures 7 and 8, I have shown the next step which involves pouring-in a top or final base metal layer a to enclose the sheath b, preliminary to a compressing operation. In Figures 9 and 10, I have shown a presser 12 in its final stick-forming position wherein its end portion 12a has entered the mold l1 and formed a compressed stick 13. The resultant stick 13 is also shown in the perspective view of Figure 11, after the presser head 12 has been raised and the bottom 10 lowered to remove it from the confines of the mold 11.

In employing aluminum foil, I provide a thin, lightweight means for supporting the alloy material during the weighing operation, for completely enclosing or sheathing it preliminary to its insertion in position on a preliminary layer of base metal, and for facilitating a substantially uniform cross-section of alloying material along the length of the stick to be produced. Further, its high conductivity is believed to be important from the standpoint of the melting operation and from the stand point of supplying electrical current to the electrode thereto during the melting operation. The resultant compact of Figure 11 thus consists of continuous shell of base metal material having a core of alloying additions accurately proportioned, so that any unit length of the compact contains the correct proportions of alloying additions and base metal. The foil wrapper also prevents any loss or sifting of fine alloying additions through coarser base metal particles while the die or mold is being filled or a danger of their uneven distribution in the compacted prod uct. There is no limit to the number of different alloying additions which may be placed in one package. A consumable electrode made in accordance with my invention automatically meters the correct proportions of alloy and base metal to an alloy melt, regardless of the melting rate, interruptions in the melting, or any other foreseeable variables.

I have used the terms stick and compact somewhat synonymously to indicate the product provided which, as previously intimated, may be an intermediate product in the sense that a group of such sticks or compacts may be secured together into an integral group to provide a consumable electrode of a desired size, extent or diam eter.

What I claim is:

l. A relatively hard compact for use in providing a consumable electrode which compact has a longitudinal shape, a centrally-l0ngitudinally-extending aluminum sheathed core of alloying material, and enclosing end, side, top and bottom wall portions of highly compacted and bonded base metal material of the class of titanium and zirconium.

2. A compact as defined in claim 1 wherein, the sheathed alloy core is held in compression within and along the enclosing wall portions of the base metal material, the aluminum sheath is of a thickness of about .00l to .005 inch, the ends of said sheathed alloy core terminate at about A to of an inch from the ends of the base metal material, and the sheathed alloy core is substantially axially-centrally positioned along the base metal material.

3. A compact as defined in claim 1 wherein the cross sectional area of said sheathed alloy core is less than half the cross-sectional area of the base metal material.

4. A compact as defined in claim 1 wherein the aluminum sheath is of a thickness of about .002 to .004 inch.

5. A relatively hard compact for use in providing a consumable electrode which compact has a longitudinal shape, alloying material particles sheathed as a centrallylongitudinally-extending core in a conductive metal foil, and wall portions of highly compacted and bonded base metal particles of base metal material of the class of titanium and Zirconium enclosing the sheathed core.

6. A compact as defined in claim 5 wherein, the foil sheath is of a thickness of about .001 to .005 inch, and the sheathed core is fully supported along its length and ends within and by said base metal wall portions.

7. A compact as defined in claim 5 wherein, the base metal particles are crystalline in form, the foil sheath has a relatively high conductivity, and the sheathed core has a cross-sectional area not substantially greater than one half the total cross-sectional area of said base metal wall portions.

8. A relatively hard compact for use in providing a consumable electrode which compact has a longitudinal shape, alloying material of the class of iron, nickel, manganese, magnesium, molybdenum, tungsten, chromium and cobalt as a centrally-longitudinally-extending core within an aluminum sheath, and wall portions of highly compacted and bonded base metal material of the class of titanium and zirconium enclosing the sheathed core.

9. A relatively hard consumable electrode of a base metal material of the class of titanium and zirconium which has a longitudinal shape, a centrally-longitudinallyextending aluminum-sheathed core of alloying material,

and wall portions of highly compacted and bonded base metal material enclosing the sheathed core; the aluminum sheath being of a thickness of about .001 to .005 inch.

10. An electrode as defined in claim 9 wherein the cross-sectional area of the sheathed core is less than one half the cross-sectional area of the base metal material.

11. A relatively hard compact for use in providing a consumable electrode which compact is of longitudinal shape and which comprises, alloying material particles sheathed as a centrally-longitudinally-extending core in a conductive metal foil, wall portions of highly compacted and bonded base metal particles of base metal material of the class of titanium and zirconium, and said wall portions enclosing and positioning the alloying material and metal foil as an intermediate unit therein.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A RELATIVELY HARD COMPACT FOR USE IN PROVIDING A CONSUMABLE ELECTRODE WHICH COMPACT HAS A LONGITUDINAL SHAPE, A CENTRALLY-LONGITUDINALLY-EXTENDING ALUMINUMSHEATHED CORE OF ALLOYING MATERIAL, AND ENCLOSING END, SIDE, TOP AND BOTTOM WALL PORTIONS OF HIGHLY COMPACTED AND BONDED BASE METAL MATERIAL OF THE CLASS OF TITANIUM AND ZIRCONIUM.

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