braze welding cast iron crack help needed.

admin

Hi all,I am a pretty inexperienced welder who needs to do a cast iron repair.  It's a crack about 6" tall from the bottom of the casting in the picture to the black felt pen line drawn on the casting. The casting is approx 1/4" thick at the crackI am going to O/A braze it as I believe this to be the highest chance of success for me. Haven't brazed since my college welding class so need some detailed information.I will drill and chamfer a stop hole at the top of the crack then vee out the crack to 60-90 degrees included.  I'll heat up the veed area to a dull red to burn off the graphite/carbon then after it cools I'll SS brush off the area and clean with acetone.I will use an AW206 (or AW 208?) tip in my Smith Airline torch  - good for 3/16 (or 1/4")I'll heat the veed out area to a dull red, sprinkle some flux on the joint  then........So far so good I think - here's where I need help. I remember brazing using capiliary action, but this is braze welding and there are issues I am unsure of.1) What size brass rod should I use?  I am assuming 1/8".2) Should I buy some prefluxed rods (any particular make?) or use straight brass rod and use the Peterson #1 blue flux that I have.2) Do I tin the joint length as I go (inch by inch) or is this a preliminary step where I tin the entire length of the "crack" first?3) Do I rely on the heat of the casting to melt the brass as in brazing or do I wash the torch over the brass to aid in melting it and building up a bead?4) For 1/4" veed out crack should I attempt to do it in one pass or two?5) If you do two passes, do you allow the brass to cool, wire brush off and then remelt it, or do you do the two "passes" inch by inch before the first pass has fully cooled.Thanks in advance - obviously I'll practice on scrap first, but too many questions at the moment!ken Attached Images
Reply:Are you sure you have cast iron and not cast steel. I really like torch work, but Braze Welding with SMAW, GMAW or even  Carbon Arc can allow you to keep your total heat in put down. If the torch is it, then I suggest you tin as you go and either using the flux coated rod or adding flux is OK.Silicon Bronze will eleiminate the need for flux, aluminum bronze is stronger but I am not sure if you need a flux. Silicon bronze and aluminum bronze SMAW have save several castings including engine blocks, grates and machinery pedestals.
Reply:What is going on with this forum, Suirebit did you gave up?!Common peopleElectric adjustable beds prices frame | Air adjustable bed mattress | Electric adjustable beds prices
Reply:Weldinglifer,Yep, it's cast iron. drilling it gives a dust.  One of the other areas I have to braze consists of a square steel bar about 1-1/2" square and 4ft long and a casting.  I can't get enough heat into it to get it hot enough to braze, even with an aw208 tip - good for 1/4" welding and about the lartgest tip I can use with my size of acetylene tank. I was hoping for other experienced cast welders/brazers to chime in  also.I  guess next time I'll post an interesting question like "Should I buy a Miller 180 or a Hobart 187?"
Reply:PM member:  castweldhe can help you  i would think   ni rod and stick weld itidealarc 250/250 ac-dc tigidealarc 250/250 ac-dc tig #2 used for sticklincoln sp100hh125dual arbor grinder polisher30 yrs of hand tools52 pitch blocks 6p-26prake gauge -pitch gaugeG&D prop repair 918-207-6938Hulbert,okla 74441
Reply:Originally Posted by kenc184Weldinglifer,Yep, it's cast iron. drilling it gives a dust.  One of the other areas I have to braze consists of a square steel bar about 1-1/2" square and 4ft long and a casting.  I can't get enough heat into it to get it hot enough to braze, even with an aw208 tip - good for 1/4" welding and about the lartgest tip I can use with my size of acetylene tank. I was hoping for other experienced cast welders/brazers to chime in  also.I  guess next time I'll post an interesting question like "Should I buy a Miller 180 or a Hobart 187?"
Reply:a carbon arc torch will give you the heat you need.