Document 0qnK9mV8EMVp4aojm8MNNvGjb

DOING THE JOB t,iw 4--Spread Alloy in Paste; Form as if Icing a Cake Reverse, ovarlop the pre vious stringer, os shown Some herd-facing materials come in pane form, these is chromium-boride, which reads 68 to 72 on R< C scale. It has good resistance to extreme abroj found in materinla-handling chutes, fan blades, pt,n| lart, scraper blades, cmsber rings, screw conveyer^, In addition to resisting abrasion, chromium berlde against corrosion and impact, has hot-hardness qmfo easy to apply, by carbon are or oxyacetylene torch. Applying Paste. Clean base metal thoroughly. |{ scale or rust, remove by grinding, shot-blasting w with abrasive cloth. Amount of preparation needed on previous service of material to be coated. Watch problems like oil-soaked castings. If not baked oqi, cause herd-surfacing Job to fail. Ordinarily, preheat the work to about 100 F. Play tene flame or blow torch back and forth across pi heats up sloVly and evenly. Paata comes in cans, mixed with water. If it's too, add water and stir to the right consistency. Then ipi on metal with a putty knife, a stiff brush or a piece Coaling thickness runs about 1/16 in. Puti/ng on i is much like icing a cake. Next, let paste dry. The evoporates the water quickly. Sweating. If metal to be coated is 14-gage or li oxyacetylene or earbon arc torch. Spread paste about 1 Heat base metal up to sweating temperature. Fusing . metal and paste will show as a dark Una ahead of the. flame. Move torch across work, keeping the dark line of the flame. For metal of over 14-gage, use standard catkoa eh of S/16, % or % in. die, depending on thiekneu metal. Have straight polarity with just enough cm maintain arc. Hold carbon about 80 deg to the Using Carbon Arc. Work with a quarter-moon lion, not over 2% times diameter of earbon. Point cat pencil sharpener or by holding against grinding b handled right, carbon melts so point stays as it should, about 3 in. of carbon slicking out ol bolder. Keep black spot of carbon floating on the surface j< from of the point. After sweoling-on Aral weave, pan work and return with about half the width of the weave overlapping the first. U you get porosity on th of the weave, pay no attention. It will disappear whe overlap the next weave. Use poste made of chromium-boride crystals only so work that is not to be finished. Sweating-On Powder. Chromium carbide comes powder, mixed with (lux. Sprinkle it on the base m*ts', fuse with a carbon arc or carbon arc torch for a smooth* abrasion.resisting surface, which can bo a* thin is Hardness depends on mixing with bate metal, runs 54-61 Rockwell C lor one layer and 57-63 for aeeond. M develops full hardness In resisting scaling at high t[ turet. Corrosion resistance is like that of stainless Don't use this type of alloy where impact is great. SLANT OPERAIION AND MAINTENANCE SECTION 2 flux vjifoee of the bate metal with. brush. Before fluxing, dean In car bon tetrachloride. Degreasing, Cleaning and grit-blasting must be dona properly 3 Position sifver-tofder strips ofter flux ing. Ploce one strip on base metal, a copper screen on the. solder strip ond second solder strip on copper: flux ths tungstan-corbldo Inserts In jei bn top of "tondwkh" of illSf.'itrlps'ond copper screen. Six loro' butted together on this |ob 5Heotlng to 13S0-1400 F by the pro* pone-olr burners ogolnst underside of 6 Attochlng hard-foced poq to moving rotor of coot pulveriser. Cool gats base motol bonds the Inserts. Test pulverised by impact and ofMHon be bond by tone of o hammer blow ot shown tween moving and stationary pegs shown 5--Brazing Tungsten-Carbide Plates ISufvand-tubiiitute alloys of Type Mdsee p ]12) coma as Inserts of sshipes, Some contain 90 to 95% carbide. Remaining 5 to 10$> --jysl. cobalt, iron or other elements Bgj^dia desired properties. Kfiie these carbide plates to wearing *" *3* because bratlng heat (torch Jjkjlll not melt the carbide maleC^cy do "wet" easily, so can be g[ito metal surfaces. stationary and moving grindaKfs.of the coal pulveriser shown Punishment from impact and *e*r, they are hard faced with inserts of tungsten carbide. Here are steps in typical application: Operation!. (1) Machine surface of base metal to be hard-faced. (2) De grease with trlchlorethylene, clean with earbon tetreehleride. (3) Crit-blest tungsten-carbide inserts with siliconcarbide grit to remove surface oxides and other films. ' (4) Flux machined surface of base metal with brush. (5) Cut strip silver (silver solder) to site and dip in flux. Tben put in position on base metal.'(6) Dip a copper screen or `copper sheet In fhix and place on strip silver. Because insert's coefficient of expansion is not the same as the base metal's, always put copper between. This also lakes im pact shock, as inserts ore hard, with no "give.** (7) Flux seeond strip of sil ver alloy and place on copper. (0) Put inserts in position on top layer ol strip J|ver. (9) Druse by directing flame un der base metal until both strips of silver melt. (10) Test bond by tapping in serts with a hammer. Tone indicates the quality ol the bond. Tungsten oarbide can also be used to tip your maintenance tools. Tech nique Is ssme as explained on this page. PLANT OPERATION AND MAINTENANCE SECTION 12) I