US2510960A - Metal cutting rod and process - Google Patents

Description

June 13, 1950 F. G. DANHIER METAL CUTTING ROD AND PROCESS 3 Sheets-Sheet 1 Filed Nov. 1'7, 1947 June 13, 1950 F. e. DANHIER METAL CUTTING ROD AND PROCESS s Sheets-Sheet 2 Filed Nov. 17, 1947 Patented June 13, 1950 UNITED STATES PATENT OFFICE assignor to La Soudur e Electrique Autogene,

Societe Anonyme, Brussels, Belgium Application November 17, 1947, Serial No. 786,408 In Belgium January 16, 1945 6 Claims. 1

The cutting of iron and steel by oxidation by means of an oxygen jet, the reaction of oxidation being started and maintained by the heat developed by an electric arc is a. well known process.

The present application is a continuation-inpart of my copending application, Serial No. 597,- 508, filed in the United States June 4, 1945, based upon a convention date in Belgium of January 16, 1945, now abandoned.

Generally the oxygen was supplied through a hollow carbon electrode, the are being struck between the extremity of the electrode and the piece to be cut. This old process had also been improved by the adjunction of an aluminum rod as a flux.

It has also been known to cut metals under water by a hollow metallic rod through which an oxygen jet is passed, employing on the rod a carbonaceous coating which produces an envelope of gas.

It could also have been proposed to use, as a hollow electrode, a simple steel pipe, in which the oxygen stream passes and to cause the electric arc to be struck between the extremity of the pipe and the piece to be cut. This process would not be able to be developed industrially: firstly, on account of the great consumption of oxygen and pipes, with the resulting frequent interruption of the cutting operation to change the electrode, and especially because the slot or cut obtained would be very wide.

After many experiments the applicant has finally realized a process giving practical and unimpeachable results, in which no commercial pipes are used, but which consists in utilizing an oxygen jet through an inner passage reserving in a metal electrode, with respect to a given total cross section of said electrode, a greater metal section, so that for a sufficient strength of the electric current, a minimum of electrode length is consumed in the time unit for a maximum cutting length.

In other words, in the process according to the invention, an electrode of given and necessarily limited length, but responding to the above defined condition, makes it possible to operate a cutting of relatively great length, all conditions inner passage for the oxygen gas in form of one or several narrow channels, the total cross section of which in the preferred embodiment is smaller than the quarter of the net metal cross section of the electrode.

It has been found that the best ratio of the cross section of the passage for the oxygen to the total cross section of the metal and bore of the rod is between 4 and 20 per cent.

An important aspect of the invention is the character of coating which is employed to facilitate the cutting and minimize the consumption of rods. In accordance with the invention the coating which surrounds or extends along the metallic core of the rod consists practically entirely of inorganic ingredients which in the arc in the presence of oxygen form practically only products which are solid or liquid if considered at room temperature. This avoids the undesirable efiects of substantial evolution of fixed gases such as are obtained from conventional welding rod coatings and from the underwater cutting rod coatings.

The drawings show a few only of the numerous embodiments in which the invention may appear, the forms shown having been chosen from the standpoints of convenience in illustration, satisfactory operation and clear demonstration of the principles involved.

Figures 1 to i inclusive are enlarged diagrammatic cross sections of metal cutting rods in accordance with the invention.

Figures 8 and 9 are diagrammatic sectional illustrations of the cutting operation.

In carrying the invention into effect, the combustible metal electrode may be made of iron, for instance cast iron, but it can also be made of steel.

In a special embodiment, the oxy-electric cutting electrode according to the invention is made, for instance, of a steel strip or band 20 folded one or several times on itself and suitably compressed or drawn, in such a manner that one inner channel 2| (Figure 1) or several inner channels 22 (Figure 2) for the passage of the oxidizing gas (preferably at least commercially pure oxygen) will be formed.

Comparative tests have shown that for an equal area of the cross section of the passage for the oxygen and provided the above specified relation between the metal to be burned and the oxygen passage is maintained, good results can be obtained with various forms of passage cross sec tions other than the circular form, especially with passages of triangular cross section'as shown at 23 (Figure 3).

For preventing the displacement of the arc at the extremity of the rod forming the gas electrode, the single or multiple channel may be distinctly eccentric with respect to the section of the electrode as at 2i or 25, in order to leave on one side a bigger mass of metal supporting the electric arc (Figures 4 and 5).

The bore may also take the form of two triangular longitudinal passages 28 as shown in Figure 6.

The core is surrounded by a coating 21 as shown in Figures 1 to '7, which performs a number of different functions as later explained. In accordance with the invention the coating is of mineral type and differs from the conventional arc-welding mineral coatings in that it consists practically entirely of inorganic ingredients which in the arc in the presence of oxygen form practically only products which are solid or liquid if considered at room temperature. In other words, the coating does not evolve substantial quantities of fixed gases such as carbon monoxide, carbon dioxide or the like which are so generally desired and widely used to surround arc-welding operations and are accordingly formed from ingredients included in conventional arc-welding coatings. The presence of such fixed gases in the cutting operation in accordance with the present invention definitely slows up the cutting by diluting the stream of at least commercially pure oxygen which passes through the arc, thereby reducing the calorific intensity of combustion of the rod and work, and also carries away sensible heat needlessly in such fixed gases. ponents of the combustion of the rod of the present invention will be limited to vapors of metals, silicon, etc., which may be formed in the arc, and minor contents of vapor or gas from water or other impurities which may be unintentionally or undesirably present.

In the underwater cutting rods substantial amounts of carbonaceous material have been included in the coatings so that any mineral, if present at all, was not effective in aiding cutting. The coating of the present invention is for all practical purposes entirely mineral, providing a heavy liquid or solid which is projected forward by the arc and the oxygen stream into the cut. This stream of mineral from the coat- 5 ing aids cutting in a number of respects. Many of the alloys out such as chromium alloys, form refractory oxides at thesurface of the cut and thus tend to form a refractory skin which impedes further cutting. When carbonaceous and chromium oxide, and also a chemical fiuxing action exerted particularly by silicates and the like in the coating. Furthermore solid products of combustion result from the burning of the core and work in the oxygen stream, and these tend to clog the kerf, whereas the mineral ingredients from the coating aid in fluxing away such products of combustion. The net effect of the mineral coating is to produce a much narrower kerf than would be possible were a carbonaceous containing coating used as in the In general the gaseous com- Ell prior art practice with underwater cutting or the conventional arc-welding practice.

There is a tendency also for the oxygen stream and. the arc to project or propel metal from the rod into the work, and the propulsion of this metal stream also contributes to the propulsion of the coating products and has a tendency to break up the refractory oxide skin and carry away products of combustion from the kerf.

A further important function which will be emphasized in consideration of Figures 8 and 9 is the effect of the coating in sealing the oxygen jet to the work and forming a crucible, since the .core of the rod will burn out more rapidly than the mineral type coating.

The oxygen jet exerts substantial cooling effect and has a marked tendency to extinguish the are even when direct current is used. It is, therefore, very desirable on direct current, and most important on alternating current, to include an ionizing substance in the coating, to stabilize the arc and prevent extinguishing of the arc notwithstanding the effect of variation in the arc length and of the oxygen jet.

The coated rod of the present invention, unlike the underwater cutting rods, is capable of effective use in air with alternating current.

The coating also performs an important function of insulating the core at all times. For example, in piercing it insulates the side wall from the edge of the hole being pierced. Likewise when cutting is accomplished in a space close to side walls, the coating insulates from such side walls. Furthermore, the coating insulates from the kerf walls in deep cutting of thick'members, and permits re-establishing the are at the bottom of the kerf when several rods are used in a single cut. Due to the fact that the core burns off more rapidly than the coating, the coating automatically holds a suitable arc spacing, and it is merely necessary for the operator to hold the end of the coating in contact with the work at all times. Thus there is in ordinary cutting no conscious effort involved in holding the are.

To summarize some of the important effects of the coating of the invention, it will be seen that it aids in cutting by removing refractory oxide and by fiuidifying combustion products, by sealing the oxygen jet to the work, and by stabilizing the arc in the presence of oxygen and particularly on alternating current. The are stabilizing effect is evident in spite of the use of low currents, which are favorable for slower combustion of the rod.

When the electrode according to the invention is, for instance, constituted by a steel band or ribbon simply formed into a roll, so as to form a single narrow channel for the passage of the oxygen gas under pressure, this coating may also serve the purpose to secure the tightness of the electrode channel at 28 (Figure 7). Figure '7 is similar to Figure 7 except that the bore is eccentric in Figure 7 and concentric in Figure 7 The coating will be made from inorganic materials, a wide variety of which are suitable. Inorganic materials such as the carbonates which under the arc in oxygen yield a material which is gaseous at ordinary room temperature should be avoided, and likewise carbonaceous combustible materials such as cellulose should be eliminated. I Suitable coating materials include silicates of' calcium, magnesium, potassium, sodium, zirconium and iron and complex silicates of two or more of the same, titanates of potassium, sodium, strontium and iron; metallic oxides such as titanium dioxide (rutile) manganese dioxide, and magnetite; silicate glasses such as alkaline powdered silicate glass; monazite sand (cerium phosphate), clay in minor proportions to aid extrusion or in larger proportion to act as a flux and oxidizable metal powders with insulating ingredients.

Of the materials referred to, it is preferable to include an ionizer in each coating. Suitable ionizers are potassium titanate, titanium dioxide, manganese dioxide, potassium zirconium silicate, sodium silicate, calcium silicate and potassium silicate.

It will also be desirable to include a flux such as one of the silicates or silica.

It will also be desirable to include in the coating a conductor of the second class which will be insulating at moderate temperature and therefore will permit the coating to be insulating except at the hot end, and will be conducting in the hot end to aid in re-establishing the arc by bringing the hot end of the coating in contact with the work. Suitable conductors of the second class are ilmenite and magnetite.

The following are examples of coating compositions which are suitable to use with a core of iron, steel or stainless steel for cutting iron, steel, stainless steel, high chromium and high nickel alloys, brass, bronze and other ferrous and nonferrous structural metals and alloys.

ExampleI Per cent Magnetite Wollastonite Anhydrous clay Potassium titanate Potassium silicate 12 In this case the magnetite acts as a conductor of the second class as well as a flux, and the wollastonite acts as an ionizer and a flux, while the potassium titanate acts as an ionizer.

Example II Per cent Ilmenite Potassium zirconium silicate Powdered silicate glass Anhydrous clay Sodium silicate Here ilmenite acts as a conductor of the second class and a flux, potassium zirconium silicate, powdered silicate glass and sodium silicate act as 6 Example IV Per cent Magnetite 44 Rutile 31 Powdered silicate glass 13 Potassium silicate 12 In this case magnetite acts as a conductor of the second class and a flux, and the remaining ingredients act as ionizers and fluxes.

It will be evident, of course, that other coatings may be made up using entirely other inorganic materials which will not form any product which is gaseous at room temperature.

The operation will be better understood by reference to Figures 8 and 9 which show an electric-arc oxygen open air metal cutting rod 30 having an interior bore 3i through which at least commercially pure oxygen is passing under suitable pressure (for example 5 to 200 p. s. i.) and suitable rate of flow. The bore is formed in the interior of a core 20 in this case of steel, preferably of plain carbon low-carbon grade. The outside of the core is provided with a coating 32 surrounding the core. The coating is entirely inorganic and free from materials which would produce products which are gaseous at room temperatures. An arc 33 has been established at the end in contact with a metal plate or other work 34 which is being cut. The metal plate or other work here shown may be iron, steel, stainless steel, high chromium or high nickel alloy, brass, bronze or the like. The direction Of travel of the rod 35 is from right to left and a kerf 36 has been formed in cutting through the plate. Serrations 31 on the edge of the kerf are typical of the very slight irregularities which may be produced. The are acting at 39 has burned away the core more rapidly than the coating and more rapidly at the center 40' than at the edge. The coating then extends beyond the core at the end at 4!, and portions of the core at 42 and the coating at 43 are melted and projected forward into the cut, tending to cut away the leading edge 44 and carry oxide, slag and molten metal away from the combustion zone 45 in globules 46. The surface pre-heated by the are alone is shown at 47 and the layer pre-heated by the arc and combustion of the core is shown at 48. The products of the combustion are substantially entirely solid or liquid at room temperature, since substantially no carbonaceous material is available in the coating and the carbon in the Work will ordinarily be a negligible factor. It will be noted that the coating aids in the cutting by removing the skin of refractory oxide which forms on the leading edge and by carrying away products of ,cbmbustion through erosion and fluxing. As shown, the coating seals the jet around the are at 4|, preventing loss of gas and loss of heat. Coating also as shown at 4| automatically tends to restrict and concentrate the arc and in case of piercing or contact with walls of the work at the side will prevent undesired side arcing.

Thus as shown, a metallic arc with direct or alternating current is established to the work, a stream of oxygen is passed through the interior of the arc to the work, and the mineral coating consisting practically entirely of inorganic ingredients, which in the arc in the presence of oxygen form practically only products which are solid or liquid if considered at room temperature,

electrodes.

the cutting into the layers of the stack beyond the first layer is not present. In this form the coating particles tend to carry the cut through the subsequent plates to and e and beyondthe gaps- 5 1 and 5-2.

The following comparative tests have been run using rods as follows:

1- The rod. of. the present invention.

2'. The: underwater cutting.v rod with a. Scotch tape coating according to Ronay U. S. Patent 2,410,461.

3.. A standard gas shielded arc-welding, electrode coating on. a. steel tubular core. 3a. A standard gas shielded arc-welding electrode coating with a, waterproof vinyl resin coating following- Jensen U. S. Patent 2,394,550.

4.. A Complete. vinyl resin type coating following Jensen U. S. Patent 2,394,550.

The rod according to the present inventionwas an open seamed tubular steel core rod covered with a non-gas forming silicate type coating, as herein described.

All the other experimental rods were made with the same tubular metallic core as that used for the rod of the present invention. The Ronay type rod was covered according to the procedure recommended. by the U. S. Navy for the preparation of Ronay type rods for underwater cutting, using Scotch tape of type. MES as recommended bythe Navy;

The Jensen type rod using a standard arc welding electrode coating'plus a waterproof vinyl resin coating was prepared in the manner of the rods manufactured for the U. S. Nav for underwater cutting. The standard welding electrode formula USEdIfOI" the slag forming portion or the coating was of the limestone type used for arc-welding This coating produces a gaseous shield to' protect the weld metal in its transfer across the arc and a protective slag toprotect-the weld bead; while it is cooling. The waterproof covering was a vinyl resin known as Ucilon (United Chromium Company)" reinforced with lime inthe manner recommended by Jensen for producing underwater cutting rods.

The completely vinyl resin typeof covering according te 'Jensen was prepared with the vinyl resin and lim-e mixture as recommended by Jensen. The thicknesses were adjusted to give the most favorable performance of this rod.

The four types of arc oxygen: cutting: rods above described were tested under identicalconditions, but adjustments to produce the conditions most favorable to Ronay and Jensen were required. All cuts were made in open air at normal room temperature. Oxygen was supplied from a standard tank through a reducing valve at '75 pounds per square. inch when cutting mild steel and at pounds per square inch (except for two instances at 20. pounds per square inch) when cutting. stainless steel. The current supplied to the arc was obtained from .a standard welding source. The direct current was supplied by a motor generator set and the alternating current was supplied by 7o were tested in stack cutting.

a. welding transformer. The current was approximately 200 amperes in each test. The machine settings were identical in each case but because of different characteristics in the rods some operated on less current than others. As shown in the accompanying table the currents ranged from to 208 amperes and the voltages varied from 28 to 50 volts, but most of the tests fell in the range from 160 to 200 amperes' and 30 to 35 volts. The materials out were A" thick mild steel plate, thick mild steel strips stacked three high with a & air gap between the strips and /1" thick type 347 (18% Cr, 9% Ni, 1% Cb) stainless steel plates.

Cutting of mild steel The following, table shows. the result in cutting mild steel:

GuttingData for 4" Mild Steel Rod CmrentRangcs Ave Burmofl 7 Speed, Ratio, Amps Volts V inlmin. in. cut/in.

1 Present invc 190-204 31-35 25. 4 1.19 2 Scotch tape 160-200 4450 22. 0 0. 96 3 Gas shielded"v 200 34 22.2 i 1.06 3a Gas shielded water prooied- Jensen 190-208- 29-34 17.4 0. 75 4 Allvinyl'resin-Jcnsen -208 28-35' l4. 3 0'. 73

Under the conditions of these tests the rod of the present invention shows definite superiority in. cutting mild steel. The speed in cutting mild steelplate is 10. to. 77% faster than the speed with. other typesof. rod The efiiciency of the. rod of the present invention as. measured by the distance cutper unit lengthof. rod is ID to 60% better than. the efficiency of the. other rods. The closest approach to the rod of the present invention in efiiciency is neither the Ronay nor Jensen types but the gas shielded welding rod type of coating.

Cutting stainless steel As shown in the table, the rod. of the present invention was more rapid and more eflicient in cutting of type 347 stainless steel than any ofthe other rods.

Staclc cutting Because of the unsatisfactory performance of the Jensen type rods on solid mild steel in open air, only the rodof the presentinvention, the rodwith the gasshielded mineral type welding rodcoating and the Scotch tape Ronay type rod thick and 2" wide mild steel strips were stacked three high separated by /64" to leave two air gaps between the. three strips. Cuts were attempted while dragging the rod across the upper surface of. the top strip as though the plate were solid, but with both the Scotch tape and gas shielded rod it was necessary to work the rod down into the kerf to cut the lower pieces. The following results were obtained:

Cutting Data for Stack Cutting Rod Current Ranges Ave. Burn-oil Speed in./min.

Amps. Volts Present invention. Scotch tape-Ronay... Gas shielded ODNH NOW

With the rod of the present invention there was no trouble in stack cutting, the power of the arc-oxygen stream and the coating bridging the gaps with ease. The amperage and voltage were normal. With the gas shielded arc-welding type of coating without waterproof layers, the performance was fair but the speed was definitely lower. The operating amperage and voltage were normal. With the Scotch tape type of Ronay coating, the performance was quite unsatisfac- 2 tory. The voltage and amperage swung violently from low to high values, so much so that the arc was extinguished briefly about seven times during seconds of operation. The speed of cutting was slow.

Alternating current Of all of the rods described the type of the present invention was far superior in operation 35 bined in obtaining the average speed and average burn-off rate of this rod. The rod with the gas shielded arc Welding type of coating was unsatisfactory for operation with alternating current, since the arc was so unstable that a simple dragging operation was not possible and see-saw action was necessary to keep the are going. The same coating protected with the outer Waterproof layer according to the Jensen patent showed a stability of are increased only enough so that drag cutting was barely possible. The Ronay Scotch tape coating operated about as well with alternating current as with direct current but in each case it was unsatisfactory in open air cutting. The operator experienced great difficulty in restriking the are after the rod and the plate being cut became heated since the coating softened and burned off at the tip to expose the bare core which froze fast to the plate. Moderate overheating caused the Scotch tape coating to soften and be blown completely 01f the rod.

The presence of gas forming ingredients in these other coatings is believed to be an essential reason for the deficient behavior in the tests de scribed. The completely inorganic character of the coating of the present invention is of significant importance in accomplishing stack cutting.

in view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the structure and process shown, and I therefore claim all such insofar as they fall within the reasonable spirit and scope of my claims.

Having thus described my invention what I 7 claim as new and desire to secure by Letters Patent is:

1'. An electric-arc oxygen open-air metal cutting rod comprising a tube-like metallic core having an interior longitudinal oxygen bore and a mineral non-oxygen-liberating type coating, fusible in the cutting are, supported on and extending longitudinall along the core and the coating consisting practically entirely of inorganic ingredients which in the arc in the presence of oxygen form practically only products which are solid or liquid if considered at room temperature, the coating comprising an ionizing substance.

2. An electric-arc oxygen open-air metal cutting rod comprising a tube-like metallic core having an interior longitudinal oxygen bore and a mineral non-oxygen-liberating type coating, fusible in the cutting are, supported on and extending longitudinally along the core and the coating consisting practically entirely of inorganic ingredients which in the arc in the presence of oxygen form practically onl products which are solid or liquid if considered at room temperature, the coating comprising a conductor of the second class.

3. An e1ectric-arc oxygen open-air metal cutting rod comprising a tube-like ferrous metal core having an interior longitudinal oxygen bore of diameter between 4 and 25 percent of the net metal cross section and a mineral non-oxygenliberating type coating, fusible in the cutting arc, surrounding the core and consisting practically entirely of inorganic ingredients which in the are in the presence of oxygen form practically only products which are solid or liquid if considered at room temperature.

4. The process of cutting metal in open air, which comprises establishing an alternating current metallic are from a core to the work, passing a stream of oxygen in open air throu h the interior of the alternating current are to the work, fusing in the arc the core and an ionizing mineral non-oxygen-liberating coating consisting practically entirely of inorganic ingredients which in the arc in the presence of oxygen form practically only products which are solid or liquid if considered at room temperature and projecting the fused products of the coating and core into the out under the action of the arc and the stream of oxygen.

5. The process of stack cutting metal in the open air, which comprises establishing a metallic arc to a stack of work having gaps between the work and directed across the stack, passing a stream of oxygen through the interior of the are directed against the stack in the direction across the stack, fusing in the are a mineral non-oxygenliberating coating consisting practically entirely of inorganic ingredients which in the arc in the presence of oxygen form practically only products which are solid or liquid if considered at room temperature, ionizing the coating in the arc and projectin the fused products of the coating into the cut and across the gaps of the stack to cut across such gaps.

6. The process of stack cutting metal in the open air, which comprises establishing an alternating current metallic arc to a stack of work having gaps between the work and directed across the stack, passing a stream of oxygen through the interior of the are directed against the stack in the direction across the stack, fusing in the are a mineral non-oxygen-liberatin coating consisting practically entirely of inorganic ingredi- 2,510,960 12 ents which in the are in the presence of oxygen REFERENCES CITED form practically only product's which aresoltdior The following references are of record in the liquid if-considered at room temperature, ionizing me of this patent: the coating to maintain the arc in the presence of the oxygen stream and of the alternating cur- 5 UNITED STATES PATENTS rent and projecting the fused products of the Number Name Date coating across the gaps of the stack tocut across 1,321 ,309 Holslag Nov. 11, 1919 such gaps. 1,451,392 Holslag Apr. 10, 1923 FR'ANQOIS GEORGES .DANHIER. 2,394,550 Jensen Feb. 12, 1945

Images