Armored Metal File Band And Production Thereof

Abstract

File band stock and production thereof, comprising: a flexible base metal strip having over at least a surface portion thereof, a strong, tough and adherent, abrasive armoring coating produced in situ from abrasive particles of hard, high melting material selected from the group consisting of metal carbides, borides, nitrides, silicides and combinations thereof, and particles of a matrix metal, said matrix metal particles being in said armoring coating, fusion bonded to each other, to said base metal strip and to said abrasive particles, and partially embedding and anchoring said abrasive particles therein with said particles projecting therefrom in the form of a series of sharp cutting edges, said armoring coating being preferably applied to said base metal strip in spaced regularly recurring pattern areas longitudinally of said strip.

Parent Case Text

This is a continuation, of application Ser. No. 803,561 filed Mar. 3, 1969 now abandoned.

Description

This invention pertains to armored abrading tools and the production thereof, comprising a structural base member composed of a base metal, such as steel, alloy steel or other metal or alloy characterized inherently by high strength, hardness and toughness or heat treatable to such, said structural base member having a hard wearing, ductile and abrasive surface coating produced in situ from powdered metal particles of a hard, refractory, brazing or matrix metal or metal alloy, such as a nickel-base or cobalt-base alloy, and abrasive particles of a hard, high melting material, such as metal carbides, borides, nitrides, silicides, or equivalent diamond substitute materials, said matrix metal particles being fusion bonded to each other, to said abrasive particles and to said base metal, and said abrasive particles being partially embedded or anchored in said matrix metal and projecting therefrom to provide a multiplicity of sharp cutting edges.

The invention provides a new tool of the above type and methods of producing the same, having a new field of utility, namely, flexible steel or steel alloy file band stock and bands thereof having surface portions armored as above, which are particularly adapted for high speed surface filing in standard band saw machines, of such refractory materials and metals as: glass, fiber glass, ceramics, cement asbestos, tiles, high temperature alloys, such as chrome-nickel alloys, titanium and titanium base alloys and the like.

Although flexible grinding belts are well known as constructed, for example, of an abrasively coated paper, cloth or other organic base strip material, they are commonly used only for surface grinding of relatively soft materials, such as wood, or other cellulosic products, unreinforced plastics, relatively soft metals such as aluminum, brass, mild steel and the like. Such belts are, moreover, of relatively short-lived utility, as the abrading particles, whatever their nature or mode of bonding to the base or substrate material, are soon dislodged and broken away in use with consequent loss of grinding action.

Owing to the recognized deficiencies of such belts in the surface grinding of harder materials, resort has been had to conventional file bands for such applications, but these likewise are best adapted for the surface grinding or filing of relatively soft metals, such as aluminum, brass, copper, unheat-treated steel, etc. Moreover, they are of such complicated construction as to be safely operable at only relatively low speeds and are fragile and hazardous in operation at best. Where a relatively high degree of accuracy and flatness is required, file bands are preferred over grinding belts.

Conventional file bands as used on standard band saw machines are made by riveting short, heavy and rigid individual file segments to a flexible steel band. A locking slot and rivet head is used to join the band ends into a continuous loop. There are a number of disadvantages inherent in this construction. A relatively short 10 foot length of standard file band consists of the following number of parts: One flexible spring steel band, 38 file segments, 38 spacers, 76 segment rivets, two dowel rivets or 155 parts in total. The maximum recommended velocity for a standard file band is about 150 ft./min. If this speed is exceeded, the heavy individual file segments may be torn loose from the spring steel band by centrifugal force as they travel around the drive wheels of the band saw machine. If a standard file band is inadvertently mounted in the wrong direction, it may be seriously damaged as well as create a definite safety hazard for the operator. The multiple piece riveted construction of a standard file band forms a large number of stress concentrating points with the resultant reduced fatigue life. Since a conventional file band is made up of 3 inch long, individual file segments, the overall length must be a multiple of these segments. If the band breaks, a special repair kit is required to splice and rivet in a new section. Also, the conventional file band must be ordered directly from the manufacturer in a length specified to fit a definite model of band saw machine. The individual sections of a conventional file band are essentially the same as conventional files, consequently, its use is limited to relatively soft materials such as unheat-treated steel, brass, aluminum, unreinforced plastics, and the like.

The above-mentioned limitations, complications and drawbacks of conventional grinding belts and file bands as above discussed, are completely eliminated with the armored file band construction of this invention, which in addition, has fields of utility which such conventional tools do not, namely, for the surface grinding or filing of such refractory materials as: glass, fiber glass, ceramics, cement asbestos, tiles, high temperature alloys, and other metals generally having high hardness inherently or as heat treated for use.

Since the file bands of the invention contain no rigid file segments, but are flexible throughout, they may safely be operated at speeds of up to about 3,000 ft/min. with consequent increased grinding efficiency. The tungsten carbide or equivalent abrading particles being partially embedded or anchored in a high strength matrix metal, which in turn is permanently bonded to the flexible base metal steel or alloy steel strip, are generally not torn loose or dulled in use. Moreover, the filing surface in general remains clean in operation and is not clogged with abraded material as occurs with conventional file bands. To the extent that clogging does occur with the file bands of the invention, they can easily be cleaned by the action of a wire brush or with chemicals or solvents which would disintegrate and destroy conventional grinding belts of paper, cloth or other organic materials. Particularly when filing friable materials like glass or ceramics, it is very unlikely that clogging will occur with the file band of the invention, in contrast to conventional file bands which have a positive rake and the individual file segments of which do not flex and hence which do not undergo the automatic cleansing action of the flexible file bands of this invention. To the extent that clogging does occur with the flexible file bands of this invention, the abrasive particles will still project and effect an abrading or filing action.

The armored file band stock of the invention being, furthermore, of unitary and flexible construction throughout its length, may be cut to any length and the ends joined into a loop by a simple welding operation to fit any band saw machine as required. Also, if any particular section of the file band becomes damaged, the damaged section may be quickly and easily cut out with hand shears and a new section welded in its place. Also, the armored file bands of the invention may be run in either direction, in contrast to the required unidirectional operation of conventional file bands. In addition, the unitary file band construction of the invention has no points of stress concentration, as in conventional file bands.

More particularly, in accordance with a preferred construction according to the invention, the armoring is applied to the base band stock over longitudinally and optionally also over laterally spaced pattern areas for assuring good flexibility and fatigue life of the armored band stock, and for providing unarmored areas for welding the material into bands. Such unarmored areas also function to provide spaces for the cut-off particles of the filed material to be carried out of contact between the file band and the work piece and thus prevented from interfering with the filing action. In addition, in accordance with a feature of the invention, the armoring coating is preferably so applied by the method described below, that the abrading grit particles are anchored in weldments of the matrix metal which are individual thereto and which may be spaced apart as desired for further enhancing the flexibility and fatigue life of the armored band stock. If the abrading grit particles are anchored in too close a proximity to one another, dissimilar cooling rates between these particles and the base stock may produce warpage of the base band stock or locked-in, undesirable stresses resulting from a tendency to warp.

A preferred method according to the invention for applying the armoring coating to the substrate band stock, and which also is of general application for armoring tools of other types, consists first in precoating the abrasive particles with a fluxing agent, such as borax, and with the brazing metal powders in the manner hereinafter described, the brazing metal powders being advantageously of much smaller particle size than the abrasive particles. A thin adhesive coating is next applied to the surface portion or portions of the substrate to be armored, preferably by a printing operation, employing printers ink or other adhesives as the coating materials, as described below. Before this coating becomes dry, the so-printed surface of the substrate is passed next beneath a falling curtain of the precoated abrasive particles at a rate of application adjusted to provide a preselected average spacing between the particles falling upon and adhering to the printed surface portions, non-adhering particles being removed thence by an air blast. In this way, the precoated abrasive particles may be applied to the printed surface portions in as dense or sparse a distribution as desired, depending on the character of the substrate being armored. For armoring the band file stock of the invention, a relatively sparse distribution is desired for reasons above mentioned.

The thus armored tool or substrate band stock is then allowed to travel for some distance or through a drying unit until the adhesive coating is died by removal of moisture therefrom and thence is passed next through an induction heating coil energized from a high frequency alternating current source for rapidly heating the tool or file band stock to temperature sufficiently high to melt the brazing metal powders coating each grit particle whereby the molten matrix metal flows about the base of each grit particle and onto the base metal substrate and by capillary action coalesces into a cup-like molten pool partially immersing the grit particle therein, with said particle projecting therefrom. The extent of this immersion is determined by the amount of brazing metal particles precoated onto the surface of each grit particle which is proportioned in accordance with the invention to provide only partial immersion of the grit particles therein. The extent of immersion of the grit particles is also controlled by the product of time and temperature occuring during brazing. Too high a temperature for too long a time can produce total immersion of the grit particles, while too low a temperature for too short a time can produce an insufficient and brittle fillet. The tool or file band stock is next subjected to rapid cooling in an inert atmosphere until cooled to temperature such that the molten cup of brazing metal surrounding the base of each grit solidifies and thus permanently anchors the grit base therein in bonded relation to the grit particle and to substrate base metal. This heating and cooling may also be such as to austenitize and thence transform to martensite the microstructure of the steel substrate which is thereafter subjected to a tempering treatment as described below. An alternative albeit less desirable procedure is to perform only the brazing operation in the induction heating coil, followed by an air cool and thence in a separate heating unit, heating the band stock to an austenitizing temperature, followed by quench and temper treatments.

Numerous advantages result from thus individually precoating the grits, each with its own supply of brazing metal and fluxing agent. The amount of brazing metal for each grit particle can be accurately controlled to partially embed the same only to an extent desired and to assure that each grit particle will project therefrom to provide a sharp, exposed cutting edge. The brazing metal for each grit particle bonds only to the grit particle coated thereby and also only to a relatively small area of the substrate base metal. This is of particular advantage in armoring applications requiring a flexible substrate with optimum fatigue properties as in the file band of the invention, and also as applied to band saws, sanding discs and the like. This is further facilitated by the fact that the precoated grits may, as stated, be applied to the substrate with a controlled average spacing between grits such that the bonded grits may be spaced apart sufficiently as not to impair the flexibility and fatigue life of the substrate band stock. The precoating also facilitates application of the armoring coating in spaced patterns in accordance with the preferred embodiment, whereby unarmored areas are retained to permit of welding sections of the band stock into bands suitable for use in standard band saw machines. The precoating of the grit particles is particularly efficacious where such particles are relatively large. Small grit particles are, however, more difficult to precoat and with respect to such, a satisfactory file band can be produced without precoating.

The advantages resulting from precoating the grit particles are less readily obtainable with other methods for applying an armoring coating, such as that wherein there is first applied to the substrate a thin layer of paste flux, then a layer of the brazing metal powders and finally an overlayer of the carbide grits, or that wherein a paste flux and the brazing metal powders are premixed and applied as an initial coating on the substrate base metal and an overcoating of the grit particles superimposed thereon. Such techniques tend to produce a layer of brazing metal which covers the substrate in varying the thickness throughout the armored area, depending on the amount of brazing metal initially applied and wherein it is difficult to control the extent of embedment of the grit particles. Also, where a flexible substrate is required, as in the case of the file band, the continuous layer of brazing metal reduces the flexibility and fatigue life because the physical properties of the brazing metal may not be compatible with those of the substrate. Also, the procedure for applying the flux, brazing metal and grit particles in two or three separate operations results in increased labor costs, while the excess braze metal not actually employed for anchoring the grit particles increases the material cost as compared to the grit precoating technique of this invention.

Having thus described the invention in general terms, reference will now be had for a more detailed description to the accompanying drawings, wherein:

FIG. 1 is a plan view of a fragmentary portion of steel or alloy steel flexible strip stock which is continuously armored on one surface longitudinally thereof, in accordance with one embodiment of the invention;

FIG. 2 is an enlarged sectional view of FIG. 1 as taken at 2--2 thereof;

FIG. 3 is a plan view similar to FIG. 1, wherein the base stock is armored in spaced rectangular areas with the armoring coating according to a more preferred embodiment of the invention;

FIGS. 4, 5 and 6 are plan views similar to FIG. 3 but showing various other preferred patterns of the armoring coating applied to the steel base stock;

FIG. 7 is a diagrammatic showing in flow sheet form illustrative of a method and apparatus for producing the armored grinding stock of any of FIGS. 1-7, inc., but more particularly that of FIG. 3;

FIG. 8 is a view in longitudinal, sectional elevation of a non-oxidizing atmosphere cooling and quenching apparatus employed in the flow sheet arrangement of FIG. 7; while FIG. 9 is a transverse sectional view in elevation through the quenching apparatus of FIG. 8, as taken at 9--9 thereof;

FIG. 10 is an enlarged diagrammatic view in elevation of the essential components of a strip drive and printer assembly forming part of the apparatus of FIG. 7, while

FIG. 11 is a perspective view of the printer unit as employed in the FIG. 7 flow sheet for producing armored band stock in accordance with the invention;

FIG. 12 is an enlarged view in elevation of a tungsten carbide particle coated with a flux such as borax and matrix metal particles; while FIG. 13 is a view in elevation of the coated carbide particle of FIG. 12 after fusion bonding to the base metal strip;

FIG. 14 is a diagrammatic view in side elevation of a band saw machine entraining an armor coated grinding band in accordance with the invention, for surface grinding a work piece in the manner illustrated.

Referring to FIG. 1, a flexible strip of a base metal, such as a steel or alloy steel strip 10, is provided with an armoring coating 11 extending continuously thereof in the longitudinal direction. Referring to FIG. 2, the armoring coating comprises a myriad of tungsten carbide or other diamond substitute abrasive particles, as at 13, each of said particles being partially embedded in and bonded to a substantially meniscus shaped anchoring layer as at 14, of a matrix metal, such as a high melting, refractory, nickel-base or cobalt-base alloy, which anchoring layer of matrix metal is in turn bonded to and alloyed with the base metal 10.

Referring to FIG. 3, the armoring coating is applied to the base stock 10 over longitudinally spaced rectangular areas as at 16, 17 thereof. FIGS. 4 to 6, inc., illustrate by way of example, various other spaced pattern arrangements in which the armoring coating may be applied to the base metal strip stock as at 18, 19 and 20.

Advantages of employing these spaced pattern dispositions of the armoring coating, as shown in FIGS. 3-6, inc., as compared to the continuous application of the armoring coating throughout the length of the strip, as in FIG. 1, are that the pattern arrangement gives improved fatigue life to the abrasive band stock and it also provides uncoated areas between the pattern areas to facilitate welding of ends of the band stock into a continuous loop. The continuous armor coating arrangement of FIG. 1 may, however, be of advantage for use in hand files used with some materials, particularly when sections of each file are supported under tension in suitable holders.

Referring to FIG. 7, the following is a suitable sequence of manufacturing operations for the production of armored file band stock according to the invention. A coil of, for example, AISI 6150 alloy steel strip 0.025 inch thick .times. 1 inch wide is mounted on an unwind reel 30. By way of example, this coil may contain approximately 1,000 feet of strip. A frictional drag mechanism of conventional construction (not shown) restrains the unwind reel from turning prematurely in response to the spring energy contained in the wound up steel strip. The strip passes thence between a pair of rubber covered rolls 31, 32, which frictionally engage the strip and the upper roll of which is driven in order to move it forward against the resistance of the frictional drag mechanism. Thus, the upper roll 31 is driven by a variable speed electric motor 33 and geared head speed reducer 34, as described more in detail below, while the lower roll 32 functions as an idling back-up roll.

The strip then passes between a pair of rolls 35, 36 of an industrial roll type printing machine, shown generally at 37 as hereinafter described. This machine prints a desired pattern as shown, for example, in any of FIGS. 1-6, inc., on the top side of the strip using a viscous coating medium, as hereinafter described. The printing machine is driven via a chain drive 38 by the same motor and speed reducer 33, 34 that powers the drive wheel 31 so that the printing speed and strip speed are synchronized as hereinafter explained. While the printed pattern is still wet, the strip passes under a vibratory feed hopper 39, electromagnetically actuated in conventional fashion. This feed hopper covers the entire strip with a thin layer as at 40, of tunsten carbide or other abrasive particles which have been precoated with a suitable flux such as borax and the brazing metal powders, as described below. The strip covered with the thus precoated tungsten carbide particles travels next past an air blower 41. This blower removes the abrasive particles from all areas of the band other than those which stick to the printed pattern. Depending on such factors as strip speed or spacing between the feed hopper and the air blower, it may be necessary in some instances to include a dryer between the hopper and the air blower. Alternatively such a dryer, for example as an infra-red ray drying unit, may be disposed as at 42, following passage of the strip past the air blower 41.

The strip with the abrasively coated pattern passes next through a high frequency induction coil 43 energized from a high frequency current source 44, as for example of about 5.2 megacycles per second. This coil heats the strip to approximately 1,900.degree. F. to austenitize the steel of the substrate strip and to braze the tungsten carbide grit to the strip by causing the steel band to be inductively heated, this heat then by induction and radiation causing the matrix metal particles coating each carbide particle to melt and flow to and about the base of each particle in the manner shown in FIG. 2, as is more fully explained hereinafter with reference to FIGS. 12 and 13. The strip passes next through an atmosphere chamber 45 and thence through a slotted, water cooled, chill block 46 extending therefrom as hereinafter described with reference to FIGS. 8 and 9. As the strip passes out of the magnetic field of the induction coil and into the atmosphere chamber, the matrix metal cools and solidifies thereby permanently to anchor the grit particle therein and to band the matrix metal to the grit particle and to the base metal substrate. The chill block further cools the heated strip quickly to temperature below that of martensitic transformation of the steel substrate, thus to quench harden the same. The chill block is not required where the strip stock is made of a steel which hardens on air cooling from the austenitic state.

As discussed more fully below, the atmosphere chamber is supplied with a circulating flow of nitrogen gas to minimize scaling or oxidation of the steel strip substrate until it is cooled below scaling or oxidizing temperature. The strip passes out of the chill block 46 through a slot 47, thence over an idler support roller 48 and through a tempering oven 49, wherein the strip is tempered at about 950.degree. F. The strip passes next past of counter 50, which continuously records the total length in feet or otherwise of the strip processed. The strip is next engaged by a take-up reel 51 driven by a motor 52. The take-up reel exerts only an intermittent pull on the band. It is intermittently activated by a tension arm 52a resting on the band stock 10, and applies tension when needed for coiling but avoids excessive pull which could stretch the file band at the point where it is red hot and weakly plastic in the induction heating coil.

Referring to FIGS. 7, 8 and 9 the atmosphere chamber 45 comprises a rectangular housing consisting of a base plate 53, and side walls 54, 55, made preferably of cement asbestos such as that sold under the trade name "Transite." The three-sided structure thus formed is closed at the top by a "laid on" glass plate 56. The housing is partitioned into a chamber 60 by end and partitioning walls 61, 62, which are centrally slotted, as at 63, 64 for passage of the armored strip 10 in the direction of the arrow thereon. The housing is provided at its base with an inlet pipe 65 for introducing nitrogen gas under pressure which flows as indicated by the arrows in chamber 60, and escapes through the strip feed slots 63, 64. The portion flowing through strip inlet slot 63 flows through and about the induction heating coil 43 and thus protects the strip 10 against oxidation as it is heated up by this coil. The portion flowing through the strip outlet slot 64 flows in turn through a slot extending through the chill block 46 in the manner and for the purposes as follows.

Referring to FIGS. 8 and 9, the chill block comprises a pair of substantially rectangular chill blocks 70, 71, made of metal of high thermal conductivity, such as copper or aluminum. These blocks are bolted together as at 72, 73 and supported on the base plate 53 of the atmosphere chamber housing and are otherwise mounted between the side walls 54, 55 thereof, with the glass cover plate 56, disposed in partially overlapping relation to the upper chill block 70 as shown. The chill blocks are longitudinally slotted medially thereof, as at 75, 76 to provide a passageway as at 77 for feeding the bank stock 10 therethrough. Within this passageway are disposed angle members, as at 79, 80 made preferably of the aforesaid "Transite" cement asbestos. These angle members are supported on the lower chill block 71 as shown in FIG. 9, and the band stock 10 is in turn slidably supported on the upper horizontal surfaces of the angle members. The primary purpose of the Transite supports 79, 80, is to center the band stock 10 in the chill block passageway 77 for more uniformly cooling the band stock. Thus, by virtue of these Transite supports, the file band 10 is not as drastically quenched in passing through the chill block passageway 77 as it would be if permitted directly to contact the chill blocks.

The side wall 55 is penetrated by a pipe connection 81 which connects with a passageway 82 formed of semicircular grooves machined in the upper and lower chill plates, as at 83, 84, this passageway extending to an opening into the strip passageway 77, in the manner shown at 83, 84 in FIG. 8. Nitrogen gas introduced under pressure through the pipe connection 81, flows through the passage 82 and into and through the file band passageway 77 to its exit end. Also, the portion of the nitrogen gas introduced into the atmosphere chamber 45 which flows through the file band exit slot 64, also flows through the strip passageway 77 to the exit end thereof. The nitrogen gas flow is thus directed along both the upper and lower surfaces of the file band and thus prevents oxidation thereof as the band is being cooled below that of martensitic transformation. The glass cover plate 46 is loosely laid on the atmosphere chamber to avoid strain from differential heating that would otherwise occur if clamped in place.

Each of the chill blocks 70, 71, is longitudinally bored, as at 90, 91, these bores extending from openings at one end thereof, as at 92, 93, FIG. 8, but terminating short of the opposite end, as at 94, 95. These closed ends are connected respectively by bores normal thereto, as at 96, 97, which extend through the chill blocks and thence through the side wall 54, of the atmosphere housing, where they are joined by a U-shaped tubular coupling 98. The open ends 92, 93 of the bores 90, 91, are tapped to pipe fittings, as at 99, 100, comprising inlet and outlet connections for circulating flow of coolant liquid, such as cold water, from an inlet connection, such as 99, thence in order through bores 91, 97, through coupling 98 and bores 96, 90 to the outlet connection 100. In this way, the chill blocks are maintained at temperature sufficiently low to effect the desired quenching action of the file band stock as it is fed through the passage 77.

The printing unit 37 of FIG. 7 being of conventional construction, is shown diagrammatically in its barest essentials in side elevation in FIG. 10, and in perspective in FIG. 11. Referring thereto, the motor and geared head speed reducer 33, 34 drives the upper feed roll 31 to feed the steel substrate strip stock 10 in the direction of the arrow. Mounted on the shaft of the feed roll 31, is a sprocket 110 encircled by drive chain 38, which also extends about a sprocket 111 of the same diameter, mounted on the shaft of an inking roll 112 which is thus driven in the direction of the arrow thereon by the feed roll 31. The inking roll dips into a bath 113 of a viscous coating liquid, such, for example, as printing ink, contained in a well 114. The ink roll 112 is geared with a 1:1 ratio to the shaft of an intermediate, rubber covered inking roll 115 of the same diameter as roll 112. The intermediate inking roll 115 is geared with a 1:1 ratio to the shaft of a printing roll 35 of the same diameter. The printing roll has embossed thereon as at 117, the armoring pattern to be printed on the band stock 10, such for example, as any of the patterns illustrated in FIGS. 1 and 3-7, inc., among others, that shown in FIGS. 10 and 11 corresponding to the pattern of FIG. 3. The print roll 35 lightly engages the upper surface of the strip stock as described below, the strip at the point of engagement with said printing roll, passing over an idler back-up roll 36.

Thus, as the printer is driven as above described, the inking roll 112 which is continuously coated with the coated liquid from bath 113, progressively applies the same to the intermediate inking roll 115, which in turn applies the liquid to the embossed pattern 117 of the print roll 35, which in turn progressively prints the pattern on to the moving file band strip, as at 119. Since all of the rolls 112, 115 and 35 of the printer are of the same diameter and are geared to one another with unity ratio gearing, and since the feed rolls 31, 32 are likewise of the same diameter as the printer rolls and are geared at unity ratio to the printer rolls via the chain drive and sprockets 38, 110, 111, the print roll 35 will be driven at the same surface speed that the strip 10 is fed.

Referring to FIG. 11, the housing 120 of the printer has extending from its far end, a shaft 121, the opposite ends of which are journalled to stanchions, as at 122, whereby the printer unit is pivotally supported. At its near end, the housing 120 has secured thereto, an angle member 123, through which is tapped an adjusting screw 124, the lower end of which bears against a fixed support 125. Thus, by appropriately manipulating the adjusting screw 124, the pressure exerted by the print roll 35 on the band stock 10 may be so adjusted that the print roll prints the viscous coating liquid onto the band stock 10 in patterned areas which are precisely in accordance with the embossments 117 of the print roll, and in the manner shown at 119, with no overflow along the edges of the patterned areas but with the coating applied uniformly throughout the printed areas.

For applying extremely viscous coating liquids, the rolls of the printer are arranged as shown in the drawings, wherein the dip roll 112 coats first the plain, rubber covered roll 115, and wherein the latter roll is adjusted out of surface-to-surface contact with the dip roll in order that the plain roll 115 may accumulate and build up on its peripheral surface a thick coating of the adhesive liquid. The print roll 35 is then adjusted sufficiently away from the surface of roll 115, in turn to pick up and carry on its embossed surfaces 117, a rather thick coating of the adhesive coating liquid. Roll 35 is then adjusted by means of screw 124, until its embossed surfaces pass nearly in contact with the upper surface of the band stock 10 as roll 35 rotates. These adjustments prevent a squeezing out of adhesive coating liquids which are relatively slow drying and very viscous.

For printing with fast drying coating liquids, the print roll 35 and the plain roll 115 may be interchanged, so that the dip roll 112 first coats the embossed areas 117 of the print roll 35, which in turn prints the coated areas thereof onto the plain roll 115, which in turn prints the so-coated areas thereof onto the band stock 10 by an offset printing operation.

The coating liquid may be conventional printers ink minus the coloring matter, compositions for which are described in standard texts, such as Chemical and Metallurgical Engineering 47.544 (1940), Kingzett's "Chemical Encyclopaedia," 1940 Ed., page 520, and Shreves "Chemical Process Industries," 1945 Ed., page 509. As stated in these publications, printing ink consists essentially of a suspension of pigments, such as paint pigments, in a drying oil, such as linseed oil, or petroleum oils, to which may be added various natural or synthetic resins, waxes, gums, water insoluble soaps, driers, antioxidants, bitumen, asphalt or stearin pitch, etc.

In addition to the conventional printing inks, applicants have found the following adhesive printing admixtures to be suitable for purposes of this invention.

EXAMPLE I

Admix 71/2 oz. "Nicrobraz" Flux, 80 milliliters Corn Syrup, 10 milliliters Lube Well D-100, water soluble oil used as an emulsifier and to promote wetting, 20 milliliters ethylene glycol to slow up drying action, and 25 milliliters water. This mixture is suitable for use in a printing unit arranged as shown in the FIGS. 10 and 11 drawings and as above described with reference thereto.

EXAMPLE II

Admix 7 oz. "Nicrobraz" Flux with 80 milliliters glycerin.

The flux is used in the above examples as the solid in suspension to prevent squeegee action during printing which otherwise causes the adhesive to push out around the print pattern thus destroying the precise pattern. The addition of extra solids makes room between the printer and the surface being printed so that an adequate thickness of adhesive material may be applied. Flux is compatible with the process where many other types of solids for the purpose leave harmful incusions in the finished product. The "Nicrobraz Flux" referred to in the examples is a boride-fluoride flux put out under that designation by the Wall Colmonoy Company, Detroit, Mich.

As above stated, the preferred material applied to the steel or alloy steel base metal band stock for purposes of armoring comprises tungsten carbide particles precoated with a suitable flux, such as borax, and also with the brazing metal powders. The materials employed for the brazing metal are preferably powders of hard, refractory alloys, such as nickel-base or coblat-base alloys, capable of providing a matrix metal which wets the surfaces of and bonds to the tungsten carbide or other diamond substitute particles and also which fusion bonds to and alloys with the steel or alloy steel base metal band stock. Suitable such brazing alloys are "Stellite," a cobalt-chromium tungsten alloy of well known composition; also that sold by the Wall Colomony Corporation, as "LM Nicrobraz" comprising an alloy consisting of 13.5 percent Cr, 3.5 percent B, 4.5 percent Si, 2.5 percent Fe and the balance nickel. A suitable particle size for the brazing metal powders is -300 mesh. A suitable particle size for the carbide particles is that which passes through a 30 mesh screen but is held on a 40 mesh screen. Thus, the particle size of the carbide particles is considerably greater than for the brazing metal powders.

The following is a suitable procedure for precoating the tungsten carbide or other abrasive grit particles with a fluxing agent and with the matrix metal powders, although the proportions given below may be varied within fairly wide limits with satisfactory results. Assuming tungsten carbide grit of relatively coarse grit size, for example 30-40 mesh, is required, the procedure is to admix in a container approximately 1 lb. tungsten carbide grits, 1.4 oz. Oxweld Brazo Flux (borax), 4 oz. 300 mesh braze alloy granules and 50 ml. water. Where relatively fine (70-100 mesh) tungsten carbide grits are required, an admixture in approximately the following proportions is suitable, 1 lb. tungsten carbide grits, 1.4 oz. Oxweld Brazo Flux (borax), 4 oz. 300 mesh braze alloy granules and 65 ml. water. In either case, the water is boiled off until a thick slurry is formed while stirring continuously to keep the solids from sticking to the bottom and sides of the container. The slurry is then spread on a flat surface and trowelled to a thickness of three-sixteenths inch, which is sliced into small squares and allowed to dry to a solid cake. The dry cake is crushed and screened through a sieve of a mesh adapted to pass single tungsten carbide grits coated with brazing alloy, but not to pass a multiplicity of such grits stuck together. The larger crushed dry cake particles retained on the sieve are recrushed and rescreened. This procedure is repeated until all of the dry cake particles are crushed adequately to pass through the sieve. Any excessive braze alloy granules which do not adhere to the tungsten carbide grits are screened out on a sieve size substantially smaller than the coated tungsten carbide grits. The adherence of the brazing alloy granules to the tungsten carbide grits may be improved by gently hand mixing shellac with the small dried cake squares prior to crushing. For this purpose, approximately 12 milliliters of shellac may suitably be used for each pound of coarse (30-40 mesh) tungsten carbide grits in the original mixture, or 15 ml. of shellac for each pound of fine (70-100 mesh) tungsten carbide grits in the original mixture. After the shellac dries, the remaining procedure is the same as above described.

A so-coated carbide particle is shown in enlarged view in FIG. 12, wherein the grit particle is shown at 130, the flux coating at 131 and the brazing or matrix metal particles at 132. As the so-coated carbide particle passes through the high frequency induction coil, the matrix metal powders become molten and under the fluxing action of the borax and flow to and about the base of the carbide particle and against the base metal in the manner illustrated in FIG. 13, wherein the carbide particle is shown at 130, the fused brazing metal at 133 and the base metal at 134. On subsequent cooling, the matrix metal solidifies and alloys with the base metal and also bonds to the carbide particle, thereby permanently anchoring the base of the carbide particle in the matrix metal, with the carbide particle projecting therefrom to provide exposed sharp cutting or abrading edges, as at 135.

Referring to FIG. 3, in a practical embodiment of the invention, the steel strip 10 may be made of a suitable grade of heat treatable steel or alloy steel, such as AISI 6150, of 1 inch in width and 0.020-0.035 inch in thickness, and the rectangular armored portions 16, 17 may cover areas of 15/16 inch wide .times. 0.25 inch in length and spaced apart longitudinally of the strip preferably by about nine thirty-seconds inch.

A dimensional characteristic which is common to all of the patterned areas of FIGS. 3-6 inc., is a longitudinal separation between successive areas of each pattern group by about nine thirty-seconds inch, as at A-D, inc. This spacing between groups allows for cutting the band stock with shears and welding into a loop while retaining the spacing of about nine thirty-seconds inch between patterned areas contiguous to the weldment. As above stated, this spacing also provides blank spaces between the armored areas in which ground off particles of the workpiece can be carried away and out of the tool workpiece contact area.

Referring to FIG. 14, the armored file band stock may be employed for filing applications by forming a section of the stock into a closed band by welding the opposite ends together. This band, as at 140, is then spanned over and about a pair of spaced sheaves, 141, 142, with the armored surface of the band on the outside. The lower sheave 142 or the sheave which pulls the file band through the cut is power driven. Mounted intermediate the sheaves is a work table, as at 143, for slideable support of a workpiece, as at 144, this table being slotted as at 143a for passage of the file band. For filing the workpiece 144, it is manually forced against the armored band 140. In some applications it may be found advantageous to mount a back-up block as at 145, on the rear side of the file band, the block being bolted to the work table as at 146, to provide a back up for the file band where heavy pressure is required for filing the workpiece. During the filing opertion, liquid coolants may be employed to prevent overheating of the file band and workpiece.

Claims

What is claimed is:

1. A flexible file band comprising: a flexible strip of a hardenable and temperable steel having over at least a surface portion thereof, a strong, tough, and adherent abrasive armoring coating produced in situ from abrasive particles of hard, high melting point, refractory metal-carbides, precoated with particles of a high melting and tough brazing metal selected from the group consisting of cobalt-base and nickel-base alloys and combinations thereof, said brazing metal particles being fusion bonded to each other and to said steel strip and alloyed therewith into weldments individual to and partially embedding said abrasive particles bonded to and, with said abrasive particles projecting from said weldments to form sharp cutting edges, said armoring coating being applied to said steel strip in longitudinally spaced pattern areas for increasing flexibility and fatigue life thereof.

2. A file band according to claim 1 wherein said weldments are spaced apart for increasing flexibility and fatigue life thereof.

3. A file band according to claim 1 having unarmored opposite ends welded together to form said band into a continuous loop.

4. A file band according to claim 1 wherein said weldments of fused matrix metal comprise about one-fourth the weight of the abrasive particles partially embedded therein respectively for exposing sharp edges of said particles.

5. A file band according to claim 1 wherein the average grain size of said abrasive particles exceeds the average grain size of said brazing metal particles in ratios ranging from about 4:1 to 12:1.

6. A file band according to claim 5 wherein said abrasive particles have an average grain size of about 0.006 to 0.023 inch.