brazing cast iron (or not)

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Ok so im attempting a repair on a piece of cast iron. The item is between 61 and 81 years old cast iron.To first practice my brazing skills im first attempting a repair on a cheap cast iron table. I wire brushed the work piece. Im using aluminum bronze wire and oxyacetalyne torch. Im able to get the cast cherry red and melt the al-cu-si wire but it just wont stick to the cast iron. I didnt use flux.Any suggestions on where to start?I have a tig available if more heat is required. I didnt notice any cracking from heating and cooling.Thanks!
Reply:20 Mule Team Borax should work for flux. (Or it does for silicon bronze!) You can get it at WalMart. If you can't find borax, you might try boric acid ant/roach powder. You can get it at the dollar store. I've had better luck using O/A than TIG for brazing for some reason.
Reply:Wow cool. I have some borax already.Also I was just on youtube and I think my wire brushing may not have been enough. I think ill hit it with the flap disc and make it shiny (didnt know cast could shine).Thanks!
Reply:The blacksmith would tell you 20 Mule Team also. I have a can of Cast Iron Flux that was in my Grandfathers shop. Don't know what it is but its a red powder.
Reply:I'd try these:http://www.lowes.com/pd_26298-1703-K...7C1&facetInfo=Kick around the Lincoln website for additional info."Cherry" red may be a bit too warm.... Watch the puddle.You may want to "V" out the crack to allow better penetration and a larger bonding surface.Lincoln SA200's... at least 15 - 20. They come and go. Growing partial to the "Short Hoods" in my old age. Last count on Short Hoods was 13 in possession.
Reply:If you get it too hot, you'll burn the iron oxide & the brass won't tin.(if it doesn't tin & flow nice, the joint will likely fail.) You should never see the iron puddle! Then you'll need to regrind the area of the joint that got too hot. Once the brass tins, it will flow by capillary action. Def. use flux! I always powder the joint after preheating for a while, and I even dip coated brass rods in the flux can while I'm brazing.http://www.facebook.com/LockhartMetalArthttp://www.facebook.com/pages/Grumpy...44306259043484
Reply:Yep, the flux is important.  Definitely V the groove and don't overheat.  The bronze rod will flow like solder when you get it right.Miller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:Brazing cast iron? Yes! Definitely. Originally Posted by clearchris. . .Im using aluminum bronze wire and oxyacetalyne torch. Im able to get the cast cherry red and melt the al-cu-si wire but it just wont stick to the cast iron. I didnt use flux. . . .
Reply:The problems I've had with brazing cast iron seem to stem from the surface not beingclean enough.Grinding dust from prep contains carbon that prevents filler from sticking.Best results seemed to come from 1.thorough cleaning of part.  2.V-ing out and grindingsurface of crack, and  grinding well around crack,3.more cleaning(I used alcohol).4.pre-heating 5.brazingOh yeah-I used borax powder for fluxMiller a/c-d/c Thunderbolt XLMillermatic 180 Purox O/ASmith Littletorch O/AHobart Champion Elite
Reply:Ok. I think I had some cleaning issues. I also think my puny hvac brazing rig is not up to the task. I think im going to have to use my tig on this.
Reply:The cast is getting cherry red, that's plenty of heat.It's most likely the lack of flux and probably the filler's (in?) compatibility with cast.Good Luck
Reply:Yeah im giving up on the table.Im going to see if I can make this wire stick with some mild plate with tig. If that works I move up to the goal:For reference thats an 8" spool in the background.
Reply:You might want to look up aametalmasters posts on cast-iron MIG wire. He posts in various forums including this one.http://www.practicalmachinist.com/vb...nifold-241622/He's done a bunch of stuff with the Crown Alloys wire and it kicks azz.
Reply:I would heat the bejesuses out of it, TIG it with 309ss then post heat and throw it in the rod oven overnight and forget about it. Pull it the next day, wrap it in a blanket and let it cool nice and slowDisclaimer; "I am just an a$$hole welder, don't take it personally ."
Reply:TIG on cast iron with that rod you have (aluminum bronze) works great - I'd use it for your cast iron repair job for sure.  Clean the cast iron first, I sand it with a flap wheel to get it shiny.  Then use AC TIG (DC also can work but AC will keep the AL-bronze puddle a bit cleaner), and focus the heat on the bronze rod, getting it to "wet out" over the cast - try to avoid having the arc directly on the cast.  If you do it properly, no need to get the bronze rod, or the cast iron even cherry hot.  I believe it makes for much better control over the heat, and less heat input than with oxy-acetylene. And, no need for flux with inert gas shielding.I build up some poorly dimensioned wearing surfaces on a vice I am restoring with Aluminum bronze A2 rod and AC TIG - see attached pics.  Best of luck Attached Images
Reply:Ok so made some progress.First I got the tig dialed in by melting the bronze on a plate of 1/8 mild. I ended up aroubd 70 amps with the pulser set at 10 pulse/sec and 50% peak. I basically got it just hot enouhh to melt the bronze.While that was going on I heated the cast. 20 mins at 250, 20 at 375, and an hour at 450F. When I pulled the cast it was a golden color.Seemed to be doing ok. Dropped some bird poop looking bronze on there, then got the hang of it. Then I ran out of argon. @#$/^&*!Back on the heat. 375 for 20 mins, 200 for 20 then covered it with my welding gloves.I think I did melt the cast a little. I didnt experience any burn back of the cast or any problems aside from my poor positioning.  Not sure if the bronze melted into the crack or is sitting on top. I think I got it in there some.In the picture the closer part is where I think I was getting it right.Now to hook up a co2 tank and find the argon leak Comments anyone?Edit: wierd, pic is upside down. Last edited by clearchris; 12-03-2012 at 11:46 PM.
Reply:Probably going to take h*ll for this but hear goes....I was once told that if you pre heat cast, that you can weld it with 7018.  I did it once and it seemed to work pretty well but it wasn't a structural piece.  Just had to hold in a seal.
Reply:Heh. Im probably the only  guy on weldingweb with  a tig that has never stick welded. This is definitely not the piece for me to learn on. I think ill be fine with a new tank of argon. That and I need to v out the groove a bit, none of the braze penetrated.
Reply:I would advise using Silicon Bronze rather than Aluminum Bronze, I've had better luck with it. I'd start with some pre-heat of the base material, then light your arc on the filler and generally keep it there.Lincoln 175HD
Reply:Ok this time worked better. Its nothing resume worthy but I think it will hold. I cranked the heat up to 110-120amps and figured out I was holding the tungsten too far off the work. Once I held it in really close the al bronze flowed nicely.Theres some cold spots on the piece but I think its good enough.Btw I somehow managed to juice myself. I had the ground attached to the table, I accidentally welded my braze wire to the tungsten and the wire touched my leg which in turn was touching the table.  Wierd thing is that im almost certain I didnt have my foot on the pedal. Is the high frequency always on?Thanks!
Reply:Hard to say if the HF is always on. It's certainly possible on some machines that could be the case. Also remember if the machine only  has HF start, as soon as the arc goes out, the machine gets ready to restart the arc. It doesn't know how long it might be until you try and restart the arc, so it may have just reset and then when you touched the table with the rod, it thought you were trying to go weld some where else.I can't remember what machine you have, so I can't really guess to much on this..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Originally Posted by denrepThe cast is getting cherry red, that's plenty of heat.
Reply:Miller Synchrowave 180, the kind before the digital readout. That sounds right then. It wasnt painful but I nearly jumped out of my skin when I felt it.Lincoln HD3200 MIGMiller Synchrowave 180 TIG
Reply:Painted and reinstalled. I should have ground it down a bit but there were no sharp edges so I just painted it. Thanks guys!Lincoln HD3200 MIGMiller Synchrowave 180 TIG
Reply:Originally Posted by clearchrisHeh. Im probably the only  guy on weldingweb with  a tig that has never stick welded.