[Hard-Surfacing Applications and Techniques]
[From the U.S. Government Publishing Office, www.gpo.gov]

HARD-SURFACING
APPLICATIONS AND TECHNIQUES
Prepared for vehicle maintenance section
DIVISION OF MOTOR TRANSPORT
OFFICE OF DEFENSE TRANSPORTATION
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by MAINTENANCE MËÏÔODS COORDINATING COMMITTEE
OF TRANSPORTATION A&Û MAINTENANCE ACTIVITY
SOCIETY OF AUTOMOTIVE ENGINEERS, INC.
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GOVERNMENT PRINTING OFFICE - WASHINGTON - 1943
SAE Maintenance Methods Coordinating Committee
W. J. Cumming, Chairman, Chief, Vehicle Maintenance Section Division of Motor Transport
Office of Defense Transportation E. P. Gohn, Test Engineer The Atlantic Refining Company M. E. Nuttila, Superintendent, Motor Vehicles Cities Service Oil Company
G. W. Laurie, Manager, Automotive Transportation Department The Atlantic Refining Company
J. Y. Ray, Supervisor, Automotive Equipment
Virginia Electric & Power Company
S. B. Shaw, Automotive Engineer Pacific Gas & Electric Company
W. A. Taussig, Automotive Engineer Burlington Transportation Company E. W. Templin, Automotive Engineer Los Angeles Department of Water and Power D. K. Wilson, Superintendent, Automotive Equipment New York Power & Light Corporation
A. M. Wolf,. Automotive Consultant
Subcommittee on Hard-Surfacing Applications and Techniques
August Martin, Chairman, Shop Superintendent Pacific Freight Lines
F. C. Emery, Engineering Supervisor Air Reduction Sales Company George Griffin, Jr., Welding Engineer The Stoody Company
E. V. Thurston, Service Engineer Haynes-Stellite Company
E. W. Templin, Project Chairman
(H)
Hard-Surfacing Applications and Techniques
INTRODUCTION
Hard-surfacing, or hard-facing as it is generally called in the welding industry, is the process of welding a hard, wear-resistant alloy on to a metal wearing surface. The deposited alloy can be in the form of a coating, edge, or point, depending on the size and shape of the wearing surface. Because of the nature of the process, the methods, equipment, and training of operators are, for the most part, similar to those employed in good welding practice.
The advantages of hard-surfacing are derived from the greater resistance to wear afforded by the hard alloy surface. Greater resistance to wear means longer life of parts, which reduces the need for frequent replacements. Replacement requires labor and means that machines and equipment are tied up. Thus, hard-surfacing saves manpower and helps to keep valuable apparatus in operation.
Additional advantages come from using hard-surfacing in salvaging worn parts; for frequently worn parts can be salvaged at low cost and made better than when they were new. Power is often saved and particularly when engine valves are hard-faced, fuel is conserved. Top power is available for longer periods after replacement. Moreover, valves of special steels, frequently critical materials, are made to serve the life of the engine.
EQUIPMENT REQUIRED
The oxy-acetylene welding flame, the metallic arc, or a carbon arc can be used to apply the standard hard-facing rods. The electric processes are at present widely used for coating large areas where surface finish is of little or no importance. Hence, for automobile and truck parts they are usually less suitable than the oxy-acetylene process, in which the flames provides better control over the molten puddle and results in less loss of alloy.
MAGNAFLUX TEST
• Before doing hard-facing work, it is desirable to determine if the base material is sound. This can be done by use of the Magnaflux method of test.
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Frequently, it is also advisable to check the hard-surfaced part after the work is completed to make sure that no defects have been introduced by the hard-facing process.
THE OXY-ACETYLENE PROCESS
The equipment required for hard-surfacing comprises standard welding supplies, including sources of oxygen and acetylene, pressure regulators, hose, and a suitable welding blowpipe, all costing around $100 to $125. Also needed are safety auxiliaries such as gloves and goggles, a sturdy, fireproof welding table, and a good water supply; hard-facing welding rod and, in special work, a flux; and optionally, but preferably if large numbers of similar parts are to be hard-faced, suitable jigs or fixtures. Facilities for preheating are also desirable if large parts are to be hard-surfaced or if the parts to be hard-surfaced are of carbon or alloy -stpels containing over 0.50 percent carbon. Preheating equipment may consist of homemade, gas-fired,1 brick ’ furnaces or complex, commercial heating furnaces equipped with precision temperature control®; Fqr.The slow cooling of hard-surfaced parts, ;r large box containing lime or powdered mica is oftep useful.
All this equipment is usually found’ an progressive oxy-acetylene welding shop^v The only supplies consumed in the process .are 'gases and hard-facing alloy rod. While no problem is presented by the oxygen, acetylene, and heating gases, the selection of. hard-facing rod is important in assuring long, serviceable life in the hard-surfaced part.
THE ELECTRIC PROCESS
Heat is the medium used in both the electric and acetylene processes. If the article to be hard-surfaced by either process is preheated so that an equivalent amount of heat is present in the article during the hard-surfacing, there should be no difference in the final results.
The heat in the electric process is much higher and covers about one-tenth the area covered by the acetylene process. No preheating from the arc occurs when ordinary welding technique is employed. To (1)

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preheat the steel, as in the acetylene process, the welder must hold a long arc about inch in length. The machine setting should be 24 or higher on the volt-meter and the ampere setting should be high enough to turn the welding rod red its full length when welding. A circular motion about % to 1 inch in diameter should be used. To start the circular motion, strike the arc in what will be the center of the circle. Move slowly to the outer edge and continue the circle. The second and succeeding circles should advance 14 inch to the cycle. The idea is to keep the deposited hard-surfacing metal fluid long enough to raise all the impurities and oxides on the surface of the steel to the surface of the molten hard metal and allow it to solidify in a smooth, solid deposit. This post-heating on each cycle is the only way it can be done correctly.
If the welder advances more than 14 inch to the cycle or moves too fast, slag from the coating on the rod drops on the colder surface of the steel and solidifies. The hard metal will flow around it and leave a slag hole. To raise this slag, the arc must be held over it until it melts and flows back on the hard metal. It is necessary to go back over the previously deposited, hard-surfacing metal and come back out over the edge of the molten, hard-surfacing metal onto the steel surface. If the speed of the cycle is too great, the same condition results. The speed of the cycle is determined by the melting of the steel surface. The fluid hard-surfacing will flow into the surface of the steel as fast as it reaches the melting point . If the machine setting is correct and the proper length of arc is used, the cycle will require about 3 seconds;
SELECTION OF HARD-SURFACING ROD
Hard-surfacing rods‘fall into five major classes and the composition o of, «each of the classes is as follows:	*«•*•*
Class I—Alloy cast irons and steels containing less than 20 percent allbying constituents.
Class II—Iron-base alloys containing over 20 percent alloying constituents (such as chromium, tungsten, molybdenum, manganese, vanadium).
Class III—Nonferrous materials, such as cobalt-base alloys containing chromium and tungsten.
Class IV—Cast tungsten carbide which has been crushed, contained, or embedded in a high-strength steel binder.
Class V—Diamond substitutes consisting of small (usually % to 1)4 inch long) cast “inserts” of tungsten carbide.
Sources, descriptions including brand names, and recommendations as to use of hard-facing welding rods in each of the five classes described above and referred to throughout the instructions which follow in this pamphlet may be obtained from rod and welding materials jobbers and manufacturers.
The welding rod manufacturer should be consulted on the proper rod to use and the proper method of application for any job in hand.
In terms of resistance to wear where there is no accompanying impact or shock, the protection afforded by these classes of alloys ranges from class I, with the least resistance, to class V, with the greatest. This order is, in general, also that of their cost per pound, which ranges from approximately 50 cents to $5. If impact must be resisted, the order is reversed, alloys of class I being tougher than those of class V. For surfaces where smoothness or precision tolerances are not required, the choice of what alloy to use is determined by a balance of the factors of wear resistance, impact resistance, and cost. If a smooth or precision surface is necessary, only alloys in classes I, H, and III can be considered. Since most automotive uses require a smooth hard-faced part, the most wear-resistant of the first three classes would normally be chosen.
OPERATOR TRAINING
Any experienced welder can, with a little practice, produce hard-faced parts that are excellent in qualities of bond, freedom from impurities or blowholes, and surface smoothness.. To apply the alloys of the classes II and III, only a few variations of standard steel welding procedures are necessary. The following variations are given as examples of the modifications hard-facing may require:
Whenever possible, class II and III alloys are applied on steel without penetration into the base metal; this is very important as it makes it possible to avoid dilution of the alloy with iron and thus to preserve unimpaired the abrasion-resisting qualities of the alloy. The operation is carried out with an oxy-acetylene flame containing an excess of acetylene and adjusted so that the flare or outer cone of the flame extends two or three times the length of the inner cone. With this flame, a small area of the surface to be hard-faced is brought to a sweating temperature; and the end of the rod is brought into the flame, allowed to melt, and spread evenly over the sweating area. The rod is not stirred or puddled; instead, additional alloy is spread in the desired direction on the base metal by means of the flame at the surface-sweating temperature.
Usually the coating can be built up to the required thickness in one operation, ana this is most desirable.
The operator may need some special training or experience to do general hard-facing successfully. The following example based on experience will emphasize the point: In a certain shop, there were four welders hard-facing the same kind of parts. These parts were finished by grinding to dimension. The thickness of the hard-facing was )4 inch. In checking these parts, they varied as much as 10
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points in hardness on the Rockwell C scale; the iron dilution ran as high as 20 percent, as determined by analysis; the life’s wear of the parts averaged 140 hours.
> Using the same make of hard-facing rod but with proper welding (hard-facing) technique resulting in only 3 to 4 percent iron dilution, the parts showed only two points variation on the Rockwell C scale and the life’s wear increased to 300 hours.
COSTS OF HARD-SURFACING
Deposits of hard-facing alloy generally range from %6 to 14 inch in thickness. Parts requiring a deposit thicker than 14 inch are frequently rebuilt with steel or an alloy of class I to within y16 to 14 inch of finished size before the hard-facing. The amount of alloy required for hard-facing any particular part can be estimated rapidly by referring to the following table:
Approximate weight of alloy per square inch of surface
Pound
%6 inch thick__________________________________ 0.	02
14 inch thick__________________________________ 0.	04
%6 inch thick__________________________________ 0.	06
14 inch thick__________________________________ 0.	08
AUTOMOTIVE PARTS REGULARLY HARD-FACED
Representative automotive parts which are hard-faced by fleet owners, or by job-welding shops for owners or operators, are clutch parts, including release yokes, pressure plates, throw-out fingers, and release-bearing housings; tappets, valve stems and stem ends, and rocker arms; transmission-shifting fingers; and both water- and fuel-pump shafts. Diesel engines often have several valve and injector parts hard-faced in their manufacture.
Figure 1.—Hard-faced fuel-pump cam rocker from a Diesel engine.
Exhaust valves and exhaust-valve seat inserts are hard-faced in large numbers by valve manufacturers for the engines of buses, trucks, and other commercial vehicles. There are 46 sizes of hard-faced replacement valves. The hard-facing of valves and valve seat inserts is rarely done except by valve manufacturers because of the necessity for specialized
technique and finishing equipment and because of the need for close heat control to maintain the neces-
Figure 2.—Typical automotive parts that have been hard-faced successfully.
sary properties and condition of the steel from which valves and inserts are made. Figures 3 and 4 show a valve being hard-faced in a well-equipped maintenance shop.
Among the parts readily hard-faced in fleet maintenance shops are the wearing surfaces of clutch mechanisms. Clutch throw-out yokes are hard-sui-faced by the application of alloy %6 inch thick to the ends of the yoke fingers. The smooth surface of the alloy, with its low coefficient of friction, results in less wear on the clutch wheel surfaces.
Clutch plates are hard-surfaced with suitable grades of class II or III alloy rods at three spots, each about % inch in diameter, where the clutch-adjusting studs bear on the moving plate. Other wearing parts in the clutch are hard-surfaced just on those areas which otherwise wear at rates such as require frequent adjustment or replacement.
Valve tappets, stems and stem ends, as well as rocker arms, are frequently hard-surfaced to minimize wear. These applications follow the general procedure and can be made by any experienced operator. It is suggested, however, in regard to valve-seating surfaces that, if available, the valves and inserts be purchased already hard-faced by the manufacturers, because of the equipment and experience necessary to produce a thoroughly satisfactory hard-faced product. Shops having such equipment and expert personnel are nevertheless turning out good and satisfactory work.
Water-pump shafts are faced over the bearing surfaces, particularly if the pump is packed. The application is most frequently made by the “skip” method, wherein longitudinal beads of a suitable grade of class II or III alloy rod are applied first on one side of the shaft, then on the other, to minimize warpage caused by the heat of the welding flame. Shafts can sometimes be hard-faced successfully by the “spiral” method, wherein the bead is applied in the form of a helix. This can also be accomplished with little warpage from the heat of the flame. Not only do shafts hard-faced by either
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method last up to four times as long as steel shafts, but the need for tightening or replacing the packing is minimized, because the smoothness and low coefficient of friction and freedom from rust or corrosion of class II and III alloys result in considerably reduced wear of the packing.
Trailer pintle hooks and eyes, tire chains, fifthwheel pins, chain sprockets, brake cam shafts, etc., are also repaired by hard-facing.
MACHINE PARTS IN MAINTENANCE SHOPS
Many parts of machines used for automotive maintenance are protected from wear by hard-surfacing. Typical are cams, lugs, and wearing surfaces of automatic machinery, lathe and grinder centers, boringbar wear strips, hot-flash shaving tools, and dies of many types for hot-drawing, blanking, shearing, trimming, forming, and upsetting. Dies for hot-working are generally hard-faced with a suitable grade of class III alloy rod.
With most other machine parts, the hard-facing follows usual practice as outlined above. To assure best results with complex dies or other intricate parts which may require special care, additional recommendations can be obtained from manufacturers of hard-facing alloys.
INSTRUCTIONS FOR SPECIFIC HARD-FACING APPLICATIONS
TRACTOR DRIVE SPROCKETS
Tractor drive sprockets are not hard-faced when new, but are allowed to wear until play develops between sprocket teeth and track pad bushings. Sprockets are then rebuilt to original size and shape with a suitable class I, hard-facing rod.
Material requirements (for two drive sprockets from Rd 8 Caterpillar tractor).—Twenty-five to thirty pounds of %6-inch diameter, coated, class I, hard-facing rod (depending on extent of wear).
Figure 5.—Method of hard-facing tractor sprocket: (1) High carbon deposit; (2) class I hard-facing.
Hard-facing procedure (see fig. 5).—Leave sprockets on tractor, but block it up so the sprocket wheel
can be turned during the welding operation. Fill in worn areas with %6-inch diameter, coated, class I rod, using template made from new sprocket wheel to obtain proper shape. Bead should be applied transversely and the deposit of each rod peened while still hot. In cases of extreme wear, it is sometimes necessary to rebuild with high carbon before applying hard-facing alloy.
Result.—The application of class I hard-facing rod to a sprocket wheel extends its life by two to three times that of one not protected. Because the hard metal deposit has a low coefficient of friction, hard-facing also reduces wear on track pad bushings, which are both expensive and difficult to replace.
TRACTOR TRACK RAILS
The hard-facing of tractor track rails is limited to those which can be rebuilt by the application of one layer of metal.
Material requirements (for rails from Rd 8 Caterpillar tractor).—Twenty pounds of %6-inch diameter, high carbon, welding rod; 40 pounds of %6-irich diameter, coated, class I, hard-facing rod ; and 15 pounds of %6-inch diameter, coated, mild steel electrodes.
Figure 6.—Method of hard-facing tractor track rails: (1) High carbon deposit; (2) class I hard-facing.
Rebuilding and hard-facing procedure (see fig. 6).—Lay track out on floor. Apply guide bead of high carbon rod to one side of 12 rails as shown in step 1, figure 6. Return and apply bead to opposite sides of 12 rails as in step 2, figure 6. Apply weaving bead of %6-inch diameter, coated, class I, hard-facing rod between- guide beads as in step 3, figure 6. Peen deposit of each rod of coated, class I rod while still hot. Apply “tie-in” bead of coated, mild steel to sides of rails as in step 4, figure 6. Check rail ends for proper clearance, removing excess metal with cutting torch.
Result.—Worn tractor rails, reconditioned as explained above, outlast new rails 25 to 50 percent. The hard-facing application can be repeated when necessary.
TRACTOR IDLER WHEELS
Tractor idler wheels are usually allowed to wear until they no longer operate efficiently. They are
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then repaired by the application of high carbon steel electrodes and given a final overlay of suitable, class I, hard-facing rod. This is another operation that can be repeated many times before the part is finally scrapped.
Material requirements (for two idlers from Rd 8 Caterpillar tractor).—Fifty pounds of %6-inch diameter, high carbon electrodes and 30 pounds of %6-inch diameter, coated, class I, hard-facing rod.
Figure 7.—Method of hard-facing tractor idler wheels: (1) High carbon deposit; (2) class I hard-facing.
Rebuilding and hard-facing procedure (see fig. 7).—Idler wheels are often left on the tractor during the rebuilding operation, but if desired, they can be removed and mounted into a fixture. In either event, low spots on guides and shoulders are filled in with high carbon, steel electrodes and a final overlay of coated, class I, hard-facing rod, applied to retard future wear.
Result.—A worn idler, hard-faced with class I, hard-facing rod, will outlast two new idlers. Amount of material required for the application is approximately 15 percent of the weight of the idler.
TRACTOR TRACK ROLLERS
The hard-facing of tractor track rollers is strictly a rebuilding operation. Any type of steel roller can He rebuilt with satisfactory results. The hard-facing of cast-iron rollers is not recommended.
Material requirements (per roller from Rd 8 Caterpillar tractor).—Six to eight pounds of %6 inch diameter, coated, class I, hard-facing rod (depending on extent of wear).
Figure 8.—Hard-facing caterpiller tractor roller, sketches 1, 2, and 3.
Hard-facing procedure (see fig. 8).—Construct jig so that rollers can be turned during the welding operation. Clean area to be rebuilt on buffer or grinding wheel. If roller is single-flange type, apply guide bead to outer edge as in sketch 1, figure • 8. Apply one or two layers of suitable, class I, hard-facing rod between guide bead and flange as in sketch 2, figure 8. Apply weaving bead to flange as in sketch 3, figure 8. For best results, deposit of each rod should be peened while still hot. If desired, hard metal deposits may be rough-ground, but grinding is not absolutely necessary.
Result.—Hard-faced rollers will outlast the best type of new roller obtainable on an average of 200 percent. The hard-facing operation can be repeated as often as necessary. Rollers on a large tractor weigh more than 1,000 pounds. To reclaim these rollers by hard-facing requires a maximum of 96 pounds of rods.
TRACTOR GROUSERS
To minimize wear on tractor grousers, top of cleats should be hard-faced with suitable I4"incb diameter, coated, class I, hard-facing rod before the tractor is put into service. When this deposit wears away, the grouser should immediately be hard-faced again. Worn grousers may also be hard-faced, but cleats should first be rebuilt to original size by welding on a steel bar of the proper size and length.
Material requirements for rebuilding and hard-facing (per grouser).—
Worn grousers: Mild steel bar stock, % by 1 inch; 1 pound of %6_incb, coated, mild steel electrodes; % pound of 14-inch diameter, coated, class I, hard-facing rod.
New grousers: % pound of %-inch diameter, coated, class I, hard-facing rod.
Figure 9.—Placement of bar stock for welding on worn grouser cleat.
Procedure for reclaiming worn grousers (see fig.
9).—Rebuild worn cleat to original height by cutting * % by 1-inch bar stock to proper length and welding on with coated, mild steel electrodes. Top of cleat should then be hard-faced with coated, class I, hard-facing rod to prevent future wear.
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Procedure for hard-facing new grousers (see fig. 10).—New grousers are hard-faced as illustrated in sketch 1, figure 10, using ^-inch diameter, coated, class I, hard-facing rod. Danger of breaking * grousers under severe operating conditions is minimized by allowing 1%-inch spaces between deposits as shown in sketch 2, figure 10.
Figure 10.—Method of hard-facing new grouser cleats, sketches 1 and 2.
Result.—Class I, hard-facing rod is so much more wear-resistant than ordinary steel that one layer applied to the top of the cleat will extend grouser life 100 percent. Since the hard-facing operation can be repeated four or five times before the grouser is finally discarded and since each deposit represents only one-fiftieth of the weight of a new grouser, this application also saves steel and eliminates transporting several sets of spare grouser plates.
BULLDOZER TIPS
To obtain maximum service life from bulldozer tips, it is essential that the hard metal be applied to the corners and edges while the tip is still new. Worn tips may also be hard-faced, but it is necessary that new comers made from scrap grader-blade steel be welded onto the bulldozer end with coated mild steel electrodes before the hard metal is applied.
Material requirements (for one bulldozer tip).— Two pounds of /^-inch diameter, coated, class I hard-facing rod.
Figure 11.—Method of hard-facing bulldozer tip.
Ha^rd-facing procedure (see fig. 11).—Clean area exposed to wear on grinder or buffer. Place bulldozer tip in flat position and apply T^-inch diam-eter, coated, class I, hard-facing rod, covering areas shown in figure 11.
Result.—Hard-faced bulldozer tips last up to six times longer than those not protected. This is another case where a small amount of hard metal (2
pounds) multiplies the life of a wearing part (dozer tips weight 25 to 40 pounds, depending on size).
DIPPER FRONTS
The best way to make dipper fronts last is to hard-face them before they are put into service and to replace the hard metal as it wears away. Buckets thus protected last months and even years. Worn buckets may also be hard-faced, but it is first necessary to replace metal worn away. This may be done by welding in sections of old grader blades, scrap manganese blades, or by the addition of nickel-manganese rod deposits. Whatever the method, an overlay of coated, class I, hard-facing rod should be applied after the bucket has been rebuilt to retard future wear.
Material requirements (for new 2^/2-yard dipper front).—Fifty pounds of T3K-inch diameter, coated, class I, hard-iacing rod.
Figure 12.—Hard-faced dipper front : (2) class I hard-facing.
Hard-facing procedure (see fig. 12).—Hard-face front of lip solidly with single layer of coated, class I, hard-facing rod. Use the skip-and-jump method of welding to avoid overheating the manganese casting. Apply stringer beads of coated, class I, hard-facing rod behind the solid deposit, spacing the beads at intervals of approximately 1 inch. Hard-face sides and bottom of lip in same manner. For best results, each rod should be peened while still hot.
Result.—Hard-facing provides the best means of keeping bucket lips in good repair. Because the hard-facing operation can be repeated many times, replacement lips are unnecessary.
SHOVEL-DRIVING TUMBLERS
Driving tumblers are not hard-faced when new, but are allowed to wear until they no longer operate efficiently. Worn areas are then filled in with steel
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electrodes and a final layer of coated, class I, hard-facing rod is applied to reduce future wear. The rebuilding and hard-facing operation can be repeated as often as necessary.
Material requirements for rebuilding and hard-facing (two tumblers from 2^-yard shovel).—Sixty to one hundred pounds of ^-inch diameter, high carbon rods (depending on wear) and fifty pounds of ^-inch diameter coated, class I, hard-facing rod.
Figure 13.—Method of hard-facing shovel-driving tumbler : (1) High carbon deposit; (2) class I hard-facing.
Procedure for rebuilding and hard-facing (see fig. 13).—Leave tumbler assembled, blocking it up so it can be turned during the welding operation. Rebuild to original shape and within % inch of size with ^-inch diameter, high carbon electrodes. Finish with final layer of coated, class I, hard-facing rod. Use template made from new tumbler to obtain proper dimensions.
Result.—Driving tumblers, rebuilt and hard-faced as explained above, outlast the best new tumblers obtainable 200 percent or more. The weight of weld metal and hard-facing rods, required for the reconditioning operation, represents but 15 percent of the weight of a new tumbler.
SHOVEL TEETH
The proper way to protect any type of shovel tooth against abrasion is to hard-face wearing surfaces before the teeth are put into service. By replacing the hard metal deposits before they wear entirely away, abrasive materials are prevented from coming into contact with the parent metal. Worn teeth may be rebuilt either by the addition of weld metal or by the use of steel bars; but the real economy results from hard-facing new teeth before they are placed in service, thus avoiding replacing worn-away metal.
Material requirements (per tooth from 2^/2-yard bucket).—One pound of %6-inch diameter, 20- to 30-mesh, class IV, hard-facing rod, and 1 pound of %6-inch diameter, coated, class I, hard-facing rod.
Procedure for hard-facing shovel teeth (see fig. 14).—Hard-face teeth on all four sides with class IV,
hard-facing rod. Deposit should extend 2 inches upward from point. Apply stringer beads with %6-inch diameter, coated, class I, hard-facing rod to top sides of teeth as indicated. Spaces between stringer beads should not exceed % inch.
Figure 14.—Method of hard-facing shovel tooth : (1) Class I hard-facing rod ; (2) class IV hard-facing rod (4 sides).
Result.—Hard-facing keeps shovel teeth sharp and extends their life two to five times over unprotected teeth, thus eliminating frequent changing of teeth and reducing spare-parts inventory.
SHOVEL CRAWLER PADS
Shovel pads are not hard-faced when new but are usually operated until considerable play develops between driving tumbler and pads. Worn surfaces are then rebuilt with ordinary electrodes and a final layer of hard-facing metal applied to retard future wear.
Material requirements (per pad from 2^/2-yard shovel).—Five pounds of %6_inch diameter, high carbon electrodes (may vary according to wear) and 2^ pounds of %6-inch diameter, coated, class I, hard-facing rod.
Figure 15.—Hard-facing shovel crawler pad : (1) High carbon deposit; (2) class I hard-facing deposit.
Rebuilding and hard-facing procedure (see fig. 15).—Lay track out flat and rebuild pads to original shape and within y8 inch of size, using high carbon electrodes. Apply final layer of coated, class I,
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hard-facing rod. Peen deposit of each rod while still hot.
Result.—Worn pads, costing $40 each and weighing over 100 pounds, can be rebuilt in 2 to 3 hours with only 6 to 8 pounds of metal. Furthermore, pads reconditioned and hard-faced by this method outlast new pads 200 percent.
CARRY-ALL BLADES
Carry-all blades should be hard-faced while new. There are two or three types of metal that can be used for this purpose, but class IV hard-facing rod is superior to others because it is made ot cast tungsten carbide (the hardest known metal) contained in steel tubes. Deposits of class IV rod not only offer maximum resistance to wear, but also have the ability to cut hard earth formations.
Material requirements (for one 8-foot blade, two edges).—Seven pounds of %6-inch diameter, 20- to 30-mesh, class IV, hard-facing rod.
Figure 16.—Application of class IV rod deposit to carry-all blade.
Hard-facing procedure (see fig. 16).—Bolt blade to carry all. Adjust machine for 150 to 175 amperes straight polarity and apply class IV, hard-facing rod, using a weaving motion. Deposit need not exceed IV2 inches in width.
Result.—Carry-all blades, hard-faced with class IV, hard-facing rod, outlast ordinary blades as much as six to one and maintain a sharp cutting edge as long as any of the hard metal remains. Weight of class IV rod, required for the application, is roughly 3 percent of the weight of an 8-foot scraper blade.
SHEEPSFOOT TAMPERS
Any type of sheepsfoot tamper, whether it is removable or stationary, should be hard-faced before it is put into service. When the tamping area is reduced below regulation size, tamps should be rebuilt with high carbon electrode and a second deposit of class I, hard-facing rod, applied in the same manner as the first.
Material requirements for rebuilding and hard-facing (per tamp).—
Worn tamps: % pound of %6'inch diameter, high carbon electrodes and Vs pound of %6-inch diameter, coated, class I, hard-facing rod.
New tamps: Vs pound of %6-ineh diameter, coated, class I, hard-facing rod.
Figure 17.—-Method of rebuilding worn sheepsfoot tamp.
Procedure for rebuilding worn sheepsfoot tamps (see fig. 17).—If tamps are removable, build fixture so that tamps can be slipped into position and rebuild to size against a copper form. The rebuilding operation is done with high carbon electrodes. When the tamp is built out to size, apply a single layer of 3/i6-inch diameter, coated, class I, hard-facing rod. If tamps are stationary, entire roller must be blocked up so it can be turned.
Procedure for ha,rd-facing new sheepsfoot tamps (see figs. 18 and 19).—To hard-face new tamps, simply cover areas shown in figure 18, making sure that corners and edges of each tamp are well covered.
Result.—There are several cases on record where one application of class I, hard-facing rod has prolonged tamp life 400 percent. Since the hard-facing application requires only Vs pound of hard metal and 5 minutes welding time, savings in time and material over using ordinary tamps cannot be questioned.
GRADER BLADES
Most grader blades are made of high carbon steel and are heat-treated. If hard-faced in the heat-treated condition, they are likely to break if subjected to impact. For this reason, it is advisable to anneal blades before applying hard-facing.
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Material requirements (per foot of deposit, 2 inches wide).—Six ounces of %6-inch diameter, 20-to 30-mesh, class IV, hard-facing rod.
Hard-facing procedure (see fig. 20).—Bolt two blades back to back. If possible, blades should be annealed before hard-facing and kept hot while the class IV rod is being applied. Machine should be adjusted for 150 to 175 amperes straight polarity and class IV rod deposited with a weaving motion. Deposit should not extend up from edge more than 2 inches. When application is finished, allow to cool in still air.
Figure 20.—Class IV rod application to grader blade.
Result.—Blades, hard-faced with class IV, hard-facing rod, will retain a sharp cutting edge and outlast ordinary steel blades up to seven times.
SCARIFIER TEETH
Either a new or worn scarifier tooth may be hard-faced. All that is necessary is that the tooth be
sharp and the top side of the point cleaned on a buffer or grinding wheel to remove oxides.
Material requirements (25 teeth, 1 inch wide).— One pound of %6-inch diameter, 20- to 30-mesh, class IV, hard-facing rod.	•
Figure 21.—Class IV rod deposit on scarifier tooth.
Hard-facing procedure (see fig. 21).—Prop teeth against brick so that the area to be hard-faced will be level. Deposit of class IV rod need extent no more than 2 inches upward from the point. Deposit should not exceed more than inch in thickness, and may be as thin as % 6 inch. Where heat treatment is necessary, quench in oil. Avoid use of water.
Result.—Scarifier teeth, hard-faced with class IV, hard-facing rod, will stay sharp 30 to 40 times longer than unprotected teeth. The hard-facing application can be repeated four or five times before the tooth becomes too short for further service.