GB2075380A

GB2075380A - Rectangular electrode

Info

Publication number: GB2075380A
Application number: GB8114155A
Authority: GB
Original assignee: Chemetron Corp
Current assignee: Chemetron Corp
Priority date: 1980-05-09
Filing date: 1981-05-08
Publication date: 1981-11-18
Also published as: JPS577398A; CA1152163A; AU6992781A; GB2075380B; AU541016B2

Abstract

A generally rectangular continuous electrode, for welding, soldering, brazing or hard-facing, has a width to thickness ratio of at least 4:1 and is made by forming sheet metal into a first continuous trough-shaped sheath (10), filling the trough with granular core materials (22) and enclosing the trough. The core materials (22) are restricted within the electrode by intermittently mechanically depressing a portion of at least one electrode wail (20, 12, 14 or 16) which defines the width of the electrode, inwardly of the electrode. <IMAGE>

Description

SPECIFICATION Rectangular electrode The present invention pertains to electrodes, wires, or rods which are typically used for welding, soldering, brazing or hard-facing applications and to a method of making same. Such electrodes typically contain filler materials therein along the length thereof. The filler ingredients in the cores of such electrodes may include base metals, alloys, flux forming ingredients, deoxidizers, arc stabilizers anc the like which are typically in particulate, powder or granular form.

A typical flux cored electrode of the prior art is disclosed in United State Patent No. 3,051,822. As taught therein such electrode is constructed of strip steel formed into tubular shape. The tube is formed of the metal to be consumed and transferred to a weld. The electrode further includes a core of alloy anc flux forming ingredients. After the tubular electrode is closed around the core the tube may be successively drawn-or rolled to smaller diameters. Such cold reduction of the cross section of the tube compacts the core materials, in place, and eliminates void spaces throughout the length of the electrode.

Compaction of the core materials inside such an electrode is necessary to ensure that the filler materials are distributed uniformly and held in position to prevent such materials from flowing from the core of the electrode during welding, soldering, brazing and hard-facing.

The prior art teaches various alternative methods of holding electrode core materials in place, including the following. United States Patent No. 1 ,650,905 teaches the preferred use of a carbonaceous binder to hold filler materials in a generally rectangular, open, trough-shaped welding rod Also United States Patent No. 1 891,546 teaches double sheathing of core materials to prevent the opening of a soldering or brazing rod during handling. United States Patent No. 4,137,446, which also pertains to the use of an inner metallic sheath to isolate the filler materials from the weld joint of an outer sheath, shows a welding wire having a rectangular configuration.

This invention pertains to a generally rectangular, two piece electrode housing granular core materials therein. The prior art methods of holding the granular electrode filler materials in position, as discussed above, are not considered adequate for the electrode of the present invention. Accordingly, ar electrode, and method of making such electrode are desired which ensures that granular electrode core materials are held in position within a two piece generally rectangular electrode.

The present invention provides a method of making a generally rectangular continuous electrode, having a width to thickness ratio of at least 4:1 comprising the steps of: forming sheet metal into a first continuous trough-shaped sheath, filling the trough-shaped sheath with granular electrode core materials, enclosing the sheath, and intermittently mechanically depressing a portion of at least one electrode wall which defines the width of the electrode, inwardly along the length of the electrode to restrict the electrode core materials within the electrode.

The invention also provides a generally rectangular, continuous electrode having a width to thickness ratio of at least 4:1 comprising: a continuous trough-shaped enclosed sheath of sheet metal, granular core materials disposed within the trough-shaped sheath, and intermittent, inwardly directed, mechanical depressions in at least one wall of the electrode which defines the width of the electrode, along the length thereof, restricting the core materials into individual compartments within the electrode.

An advantage of the present invention is that it provides a method of restricting electrode core materials within a two piece, generally rectangular electrode, particularly electrodes having a large width to thickness ratio, wherein conventional drawing or rolling is unable to prevent shifting of the filler materials in the core.

The invention will be more fully understood and appreciated with reference to the following description and the accompanying drawings, in which:~ Figures 1-5 show, sequentially, and in cross-section, various stages of a process for forming a two piece generally rectangular core filled electrode of the present invention.

Figure 6 is a cross-sectional view of an alternative electrode of the present invention prior to restriction of the core materials.

Figure 7 is a cross-sectional view of the electrode shown in Figure 6 after restriction of the core materials.

Figure 8 is a cross-sectional view of a trough-shaped sheath of the present invention as an alternative to the trough-shaped sheath shown in Figure 1.

Figure 9 is a cross-sectional view of an alternative electrode of the present invention.

Figures 10-12 and Figures 13-1 5 show alternative seaming arrangements for an electrode of the present invention in enlarged cross-section.

Figure 1 6 is a cross sectional view of an alternative seaming arrangement for an electrode formed from the trough-shaped sheath illustrated in Figure 8, prior to restriction of the core materials.

Figures 1 7-20 show sequentially, and in cross-section, various stages of a process for forming a one-piece generally circular trough into a generally rectangular electrode in accordance with the present invention.

The electrodes which are the subject of the present invention are those used in welding, soldering, brazing and hard-facing applications. It is conventional to construct such electrodes of a sheet metal housing or sheath disposed around and enclosing granular core materials in the central portion of the electrode. Common electrodes are generally of tubular construction, typically having a diameter of the order of about 1.5875 to 6.35 mm (1/16 to 1/4 inch). The present invention, on the other hand, is directed to a generally rectangular electrode having a width to thickness ratio of at least 4:1, and preferably at least 6:1. Such generally rectangular electrodes are particularly useful in applications such as overlay welding and cladding of a base metal with higher alloy materials for the purpose of enhancing wear resistance, corrosion resistance and the like.It should be understood that the term "generally rectangular" is to be given broad interpretation, and in particular, is meant to include ovular structures, as well as structures which do not have substantially planar walls, wherein the maximum width to maximum thickness ratio is at least 4:1.

Referring particularly to the drawings, Figures 1-5 illustrate sequentially, in cross-section, exemplary steps involved in making an electrode of the present invention. As shown in Figure 1, a first step in forming an electrode of the present invention may involve forming a strip of sheet metal into a rectangular, trough-shaped sheath 10 having a bottom wall 12 and sidewalls 14 and 16. As shown in Figure 2, the end portions of the sidewalls 14 and 1 6 may be formed into a ledge or step 18 for receiving a closure 20 for the electrode as explained in detail below. Forming sheet metal in accordance with the present invention is considered, in and of itself, known technology. Therefore, the tools and dies which may be utilized to form the sheet metal of the present invention are not illustrated herein.

The electrode of the present invention may be provided with a sheath of any metal which lends itself to the desired configuration as explained below. Typically, the sheath 10 is made of mild steel, stainless steel, copper, aluminium, nickel, cobalt or alloys thereof.

It should be apparent that the formation of the electrode of the present invention is a continuous operation. It is conventional that a coil of strip material would be continuously fed through appropriate tools and dies to form a trough-shaped sheath 10 such as that illustrated in Figure 1. After the strip is formed into the trough-shaped sheath, the sheath is fed through appropriate feeding mechanisms which fill the trough with appropriate filler materials, or core materials 22.

The core materials 22 are granular in form, including particulate and powder materials. Typical core ingredients for electrodes include slag forming ingredients, deoxidizers and various alloying ingredients. Additionally, weld metal powder such as iron powder may be added to the core of an electrode of the present invention. A typical core composition of an electrode of the present invention for an austenitic stainless steel weld deposit may consist of a mixture of the following ingredients: Weight Ingredient Per Cent Ferrochrome 61.50 Nickel 25.50 Manganese 2.00 Ferrosilicon 2.00 Iron Powder 9.00 Total 100.00 It is conventional to feed electrode core materials from a hopper through a metering feeder and onto a moving conveyor which feeds a trough-shaped sheath. By such conventional feeding equipment, the feed rate, in terms of volume, can be stringently controlled.It is also conventional to employ a scraper or doctor blade above the trough to remove any excess core materials from the trough prior to closing the core. In order to minimize void spaces in the core and to assist in compaction of the core, the doctor blade may be arranged to permit slight overfill of the core materials 22 into the trough-shaped sheath 10 as illustrated in Figure 2.

After the sheath 10 is filled with core materials 22, a separate cover, lid or closure 20 may be placed over the sheath 10. A typical closure 20 comprises a generally planar strip of sheet metal which is continuously disposed over the filled trough 10. It should be understood that the type of metal employed for the closure 20 may or may not be the same as that employed for the trough 10. The core materials should be completely enclosed within the electrode. As shown in Figure 4, the edges of the strip 20 are then mechanically bound with the edges of the sheath 10. This is typically accomplished by crimping or seaming the respective edges with one another.

A single seam, or crimp may be provided as shown in Figure 4 by folding the end portions of the sheath walls 1 4 and 1 6 over the edged portions of the strip 20. Alternatively, as shown in Figures 10, 11 and 12 and in Figures 13, 14 and 15 a double seam or side seam may be provided. Also, the bulk of the finished seam may be disposed above the closure 20 as shown in Figure 12, or adjacent the side walls 14 and 16 as shown in Figure 15. It should be understood that the various crimps or seams shown in the drawings may be further compressed with the appropriate equipment such as by passing the seam through a pair of flattening rolls. What is required of the crimp or seam of the present invention is that the closure 20 remain attached to the sheath 10 during subsequent forming operations and during handling, winding and operation of the electrode of the present invention.It should be further understood that the seamed area of the electrode of the present invention may be strengthened by spot welding or the like.

As explained above, the sheath 10 may be slightly overfilled, as shown in Figure 2, to accommodate a certain degree of compaction of filler materials 22 as the closure 20 is attached thereto. Despite such preliminary compaction of the filler materials, further compartmentalization must be effected to ensure that the core materials 22 remain in-place during the handling, coiling and operation of the electrode of the present invention. In accordance with the present invention, a portion of at least one electrode wall is intermittently, mechanically depressed inwardly toward the core 22 to restrict the electrode core materials 22 into compartments within the electrode.

Intermittent, mechanical depression of a portion of at least one wall of the electrode may be accomplished by a variety of methods. For example, a series of score lines may be provided in one or both electrode walls defining the width of the electrode. Such score lines may have the effect of thinning the metal wall in certain of the depressed areas, but should not cut through the metal wall.

The preferred method of restricting the electrode materials 22 is by knurling at least one wall of the electrode. Any knurlihg pattern which accomplishes the required restriction and, perhaps, densification of the core materials 22 may be employed, the most common being a diamond pattern.

Knurling efficiently creates a number of core compression pockets or cavities 24 (Figure 7) within the electrode each defined within each indentation pattern, or knurl pattern 26. As a result of knurling, the core materials 22 formerly located at the points of the knurl pattern 26 may be forced into a compression cavity, or pocket 24, in such a manner that the free flow of the core materials 22 is restricted.

As discussed above, the preferred process of mechanically depressing a rectangular electrode of the present invention is by knurling which compresses the granular core materials 22 into compartments such that free flow is restricted. This means that because of such compartmentalization the core materials 22 cannot flow freely from the tubular electrode without some form of external impact or agitation. The knurl pattern may be of any configuration, such as diamond, square or parallel, but must be able to restrict the flow of core materials 22.

The spacing of the knurl patterns may depend upon the thickness of the originally seamed electrode, the gauge of the metal sheath 10 and closure 20, the type of metal employed and the particle size of the granular core materials 22 inside the electrode. Typical spacings between knurl patterns can be expected to be less than about 12.7 mm (one-half inch), although larger patterns may be comprehended in certain conditions. It is also expected that the knurl patterns would be spaced at least about 1.5875 mm (one-sixteenth inch) from one another. It has been found that a mechanical depression must be provided within a spacing of about 25% of the width of the electrode in order for the core materials to be adequately restricted.In other words, the size of any undepressed area, at least on one side of the electrode which is provided with mechanical depressions, must have at least one dimension which does not exceed 25% of the maximum width of the electrode.

During knurling, precautions may be taken to hold the seam, or crimp, from dislodging or otherwise coming loose. In certain instances it may be necessary or helpful to weld the joint after seaming or crimping. It has been found that in some applications seam disassembly may be avoided by knurling the bottom wall 12 which is located more remotely from the seam than the cover 20.

Alternatively, either or both sidewalls 14 and 16 of an electrode as shown in Figures 8 and 16 may be knurled with little or no effect on the seam. However, it should be understood that the present invention applies to the knurling, or other mechanical depression of either electrode wall, or both electrode walls, defining the larger width dimension w of the electrode of the present invention over the continuous length of the electrode. Those skilled in the art should appreciate that the entire length of an electrode may be provided with mechanical depressions by intermittently alternating the side that is depressed or knurled. Consideration may have to be given to the particular knurl pattern employed to restrict the core materials. For example if the rectangular electrode of the present invention is to be coiled, a knurl pattern which compliments coiling should be used.A rectangular knurl pattern disposed with its rectangle length parallel with the longitudinal axis of the electrode may create stress patterns in the sheet metal which resist coiling. Alternatively, rectangular knurl patterns disposed with the rectangle length perpendicular to the longitudinal axis of the electrode may contribute to the efficient coiling of the electrode.

A further result of knurling can be bulging of the sidewalls 1 4 and 1 6 of the electrode as illustrated in Figure 7. However, if desired such sidewalls 14 and 16 may be given side support during knurling to prevent bulging during knurling and to produce an electrode such as that shown in Figure 9 with generally planar sidewalls.

In certain instances it may be beneficial to sinter the core materials 22 or to utilize binders in the core. Such methods would contribute to the restriction of the free flow of the granular materials from the generally rectangular electrode of the present invention. Additionally, resistance welding, spot welding, multiple seam welding, electron beam welding and laser welding may be utilized to assist in holding the granular filler materials 22 and the seam in position in the electrode.

In an alternative embodiment, as illustrated in Figures 17-20, a generally circular trough is filled with core materials 22. Then the edge portions are bound, such as by interlocking seam or crimp arrangement shown in Figure 18. After seaming, the electrode may be flattened into a generally rectangular structure having a width to thickness ratio of at least 4:1 and preferably at least 6:1, as shown in Figure 1 9. Thereafter, at least one side of the rectangular electrode is mechanically depressed to restrict the core materials 22, in place, in the electrode. It should be understood that the flattening and the knurling operation may be performed simultaneously. Also, the flattening operation may have the beneficial effect of tightening the electrode seam.

Rectangular electrodes are generally used for the same purpose as conventional tubular electrodes. However, it has been found that electrodes of rectangular construction may deposit a greater amount of weld metal over a wide area at one time with a minimum of dilution of the base metal into the weld metal. A rectangular electrode has the advantage of spreading a great amount of power over a greater area. With conventional tubular electrodes this can only be accomplished by manually or automatically oscillating the electrode. The possibility of a defect in the weld metal is thus reduced with the rectangular electrode of the present invention as compared to oscillating applications with tubular electrodes.

Typical rectangular electrodes of the present invention would have the following characteristics: Example 1 Example 2 Sheath: AISI alloy: 1002 1008 dimension mm (inch) trough: 0.2794 x 42.44 0.2794 x 42.44 (.011 x1.671) (.011 x1.671) cover: 0.2794 x 34.04 0.2794 x 34.04 (.011 x1.340) (.011 x1.340) Core: Composition (Weight Per Cent) FeCr (73.8% Cr) 61.50 FeMn (77% Mn; 6.6% C) ~ 3.50 FeMo (62% Mo) ~ 3.75 FeSi (50% Si) 2.00 11.25 Ni 25.00 Mn 2.00 Cr (86.5% Cr; 10.5% C) ~ 62.25 Graphite ~ 4.25 Fe Powder 9.00 15.00 Total 100.00 100.00 Fill (Weight Per Cent) 55% 50% Density (g/cc) 3.25 3.00 Type of Deposit Austenitic Stainless Hard-Facing

Claims

1. A method of making a generally rectangular continuous electrode, having a width to thickness ratio of at least 4:1 comprising the steps of: forming sheet metal into a first continuous trough-shaped sheath, filling the trough-shaped sheath with granular electrode core materials, enclosing the sheath, and intermittently mechanically depressing a portion of at least one electrode wall which defines the width of the electrode, inwardly along the length of the electrode to restrict the electrode core materials within the electrode.

2. A method according to claim 1, wherein the trough-shaped sheath is generally rectangular.

3. A method according to claim 1, wherein the trough-shaped sheath is generally circular.

4. A method according to claim 1,2 or 3 wherein the sheath is enclosed by mechanically binding the edge portions of the trough with one another along the length of the electrode.

5. A method according to any one of the preceding claims, wherein the sheath is enclosed by placing a continuous strip of metal over the trough-shaped sheath and the edges of the strip are mechanically bound with the edge portions of the trough along the length of the electrode.

6. A method according to claim 5, wherein the edges of the strip are crimped with the edges of the sheath.

7. A method according to claim 5, wherein the edges of the strip are seamed with the edges of the sheath.

8. A method according to claim 7, wherein the seam is subsequently compressed against the electrode.

9. A method according to any one of the preceding claims, wherein the cross-sectional width to thickness ratio of the generally rectangular electrode is at least 6:1.

10. A method according to claim 5, wherein the trough-shaped sheath is enclosed with a strip having a cross-sectional width defining the approximate width of the electrode.

11. A method according to claim 5, wherein the trough-shaped sheath is enclosed with a strip having a cross-sectional width defining the approximate thickness of the electrode.

12. A method according to any one of the preceding claims, wherein the intermittent mechanical depression is provided by knurling.

13. A method according to any one of the preceding claims, wherein the size of any undepressed area at least on one side of the electrode which is provided with intermittent mechanical depressions, has at least one dimension which does not exceed 25% of the width of the electrode.

14. A method according to claim 12, wherein the distance between knurl patterns is at least 1.5875 mm (one-sixteenth inch).

15. A method according to claim 12 or 14, wherein the distance between knurl patterns is less than 12.7 mm (one-half inch).

16. A method according to claim 3, wherein the generally circular trough-shaped sheath is flattened into a generally rectangular electrode after enclosing the filled sheath.

17. A method according to claim 16, wherein the intermittent mechanical depressions are provided simultaneously with flattening.

18. A generally rectangular, continuous electrode having a width to thickness ratio of at least 4:1 comprising: a continuous trough-shaped enclosed sheath of sheet metal, granular core materials disposed within the trough-shaped sheath, and intermittent, inwardly directed, mechanical depressions in at least one wall of the electrode which defines the width of the electrode, along the length thereof, restricting the core materials into individual compartments within the electrode.

19. An electrode according to claim 18, wherein the edge portions of the sheath are crimped together along the length of the electrode.

20. An electrode according to claim 1 8, wherein the edge portions of the sheath are seamed together along the length of the electrode.

21. An electrode according to claim 1 8, 1 9 or 20, wherein the edge portions of the sheath are welded together along the length of the electrode.

22. An electrode according to claim 18, wherein said continuous trough-shaped enclosed sheath comprises: a continuous trough-shaped sheath of sheet metal, and a continuous strip of sheet metal closing the trough.

23. An electrode according to claim 22, wherein the edges of the strip are crimped with the edges of the sheath.

24. An electrode according to claim 22, wherein the edges of the strip are seamed with the edges of the sheath.

25. An electrode according to any one of the preceding claims 18 to 24, wherein the crosssectional width to thickness ratio is at least 6:1.

26. An electrode according to claim 22, wherein the strip has a cross-sectional width defining the approximate width of the electrode.

27. An electrode according to claim 22, wherein the strip has a cross-sectional width defining the approximate thickness of the electrode.

28. An electrode according to any one of the preceding claims, wherein the mechanical depressions comprise knurl patterns.

29. An electrode according to any one of the preceding claims 18 to 28, wherein the size of any undepressed area at least on one side of the electrode which is provided with intermittent mechanical depressions, has at least one dimension which does not exceed 25% of the width of the electrode.

30. An electrode according to claim 28, wherein the distance between knurl patterns is at least 1.5875 mm (one-sixteenth inch).

31. An electrode according to claim 28 or 30, wherein the distance between knurl patterns is less than 12.7 mm (one-half inch).

32. A method of making a generally rectangular continuous electrode, substantially as herein described with reference to Figures 1 to 5, Figures 6 and 7, Figure 8, Figure 9, Figures 10 to 12, Figures 13 to 15, Figure 16 or Figures 17 to 20 of the accompanying drawings.

33. A generally rectangular continuous electrode substantially as herein described with reference to Figures 1 to 5, Figures 6 and 7, Figure 8, Figure 9, Figures 10 to 12, Figures 13 to 15, Figure 16 or Figures 17 to 20 of the accompanying drawings.