Cast iron blacksmith table

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I know cast iron is a chore to weld properly, but I have a limited amount of time to fix this guy's antique cast iron blacksmith table. It is the kind that you put hot coals in, it's almost like a dish in a way. It's 1/4" thick and has a large separated crack right down the middle of it, about 12 inches in length. It's been welded before but not very well so they guy brought it to me. I was wondering if I preheated it and used ni rod and then capped with silicon bronze if that would be a good mix or would the two clash? If not, should I just use one or the other?...I haven't done much cast iron work, and nothing that gets heated and cooled down constantly if that makes sense. He plans to keep using it so I want to do this job somewhat right. I do know it's a timely process though so any tips would be appreciated. Thanks! Miller Dynasty 200Millermatic 211Instagram?.... find me @ WELD_MEDIC
Reply:Is it a new crack or same place as first repair? Curious how hot the pot gets with coal in it, bronze may be a no-go.
Reply:What he has is a forge. Brazing is out. The fire will be too hot. A good sized fire in a forge is hot enough to melt steel. They use iron since it's more resistant to melting under the heat than steel would be.Option 1, bolts. My old rivet forge was repaired using patch plates and bolts. All you really need to do is hold the parts together. Not the prettiest repair, but very functional. You don't have to worry about cracking after welding. Even though I most likely have everything to weld mine back up, I see no point to taking the risk of doing so since my forge is perfectly functional as is. Option 2, Tig with high nickel filler. You'd want to do this as cold as possible. Weld only a small area say 1/2" to 1" max, then wait until the piece is cool enough to touch by bare hand before welding more. You can jump around a bit, but you want to avoid as much heat as possible.Option 3 Preheat, weld with nickel filler and then slow cool. If I absolutely had to weld this, I'd contact Castweld here and get his take on things. If anyone here is the master of cast iron repairs, it's him. he could tell you pre and post heat temps and cool down times. He might also recommend spray welding with a powder torch and OA as another option.One other thing, many of these old forges were originally designed to be clayed. An insulating layer of clay was applied over the cast iron base. This helped insulate the iron table of the forge from the heat of the fire. I'd have to see picts of the forge to make a suggestion on this. Iforgeiron is a good place to ask questions about forges and repairs, but most of the guys there will probably also recommend a cold type repair like bolts and plates vs welding because of how finicky cast iron can be. Welding will be farther down their repair list.Last edited by DSW; 02-28-2014 at 09:22 PM..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:Another point against welding is that the iron is probably heavily oxidized from repeated heat-cool cycles and would not weld worth a damn anyway.JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:DSW,thanks for the input I didn't even think about the silicon bronze melting...stupid Here's what I have:So yeah, it's quite the crack huh?...ha. I will try what I can with your suggestions, I don't think he wanted it fixed by bolts and plates or straps. I guess anything is better than what was done before....Miller Dynasty 200Millermatic 211Instagram?.... find me @ WELD_MEDIC
Reply:Ok good news. Technically  you are right, that is a "table". A separate fire pot goes in the round hole in the center and both together form the "forge". That means that the table itself is seldom exposed to the higher heat the fire pot is. It would only get super hot if he rakes out the fire to kill it when done. I still would not put brazing as my #1 choice, but it might be possible the way this is set up. Does he know how/why it cracked? I ask because unless it was dropped, 1st thing that comes to my mind is heat and water. Coal fires are often banked with water either to concentrate the heat and save fuel on the edges or when killing the fire. However cold water and hot/really warm cast iron do not play well together. I've seen plenty of cast iron forges damaged that way. Chances are high that's how someone originally damaged mine before I got it. If that is what happened, I'd be very leery of brass brazing because of the heat. ( remember if you braze you will not be able to weld later without removing material to get all the brass out.) 2nd way I'd have seen this happen is if the fit between the pot and the table was too tight. When the fire pot got hot, it expanded. However the table was still cool and didn't move, so it cracked the table. That's the 2nd suggestion I got on my rivet  forge. Mine looks like someone replaced the center grate ( not shown in the picts) and it might have been too tight and made of steel vs iron like the original one was.Oh because of the 2nd issue suggested, make sure you have the pot to make sure things line up when doing the repair. If that table is splayed open for some reason, the bolts may no longer line up when the pot is installed. If that is the case, it may crack when he fires it up and the pot expands and exerts pressure on the table thru the bolts. I would be careful trying to close that gap if that's the way it wants to sit, but the big crack could simply be from your prep.The huge crack will be an issue however in repairing this. It's quite wide at the edge. I'd be very tempted to use tig and high nickel filler and do this as cold as possible. I have seen  mig used to do similar repairs, but with that size, I wouldn't trust it not to crack when done even doing small welds and keeping it cold. Stainless mig would have a better chance vs E 70 wire because the added nickel in the stainless would add more "give" to the material.PM Castweld. I'd be curious to see if my thoughts matched what Peter thinks. If he says brazing is good to go, I'd trust his judgement. If he has a different suggestion, I'd love to hear it so I can learn some also.Last edited by DSW; 03-02-2014 at 07:39 PM..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:Yeah, I'd bolt and strap underneath as fear is, it will break in half right in front of a bunch of people whilst doing a Smithing demo or worse yet, drop fire on a wooden floor.
Reply:Talked to the guy again today. He said he doesn't want straps and bolts so the ni alloy rod it is then. Also, he said that the area gets very hot so si bronze is definitely out of the question. Where is the best place to buy? Local welding shop doesn't have any. I will order some and weld and show pictures with results.Miller Dynasty 200Millermatic 211Instagram?.... find me @ WELD_MEDIC
Reply:tig 21If you are determined on welding I would close the gap first.On a substantial surface dog the table and construct fixturing to draw the gap closed by heat the intact hinge area with a rose-bud.Heating the section will require the largest Victor Journeyman size rose-bud that a large Ox bottle will fire.  Anything smaller is just awaste of OA.Your fixturing is to hold the split pan sections flat, when pulling the sections together under heat.Brazing apps aside, unless it is imported junk yard art, I only use Nickel rod for cast.  Depending upon nickel content you may have $50.00 to $100.00+ in rod.Opus
Reply:That looks like a bad dream! If it were mine I'd wrap a piece of flat bar around it and rivet it to it. Be careful when welding. It can act as though it's all going well until you hear loud pop and you find it in two pieces. Good luck!Miller trailblazer301gLincoln sa200Miller251Miller spectrum 625Victor oxy-acc2002 Chevy duramax 3500 dually 4x4
Reply:Personally, I wouldn't hesitate to braze weld that forge table with SiB. It's not going to get all that hot where the cracks are (nor even in the firepot since the blast air is normally fed from below, which cools the firepot). Silicon bronze melts around 1600-1800°F so unless he's getting that table damn near YELLOW hot (and this is HOT, Jack, waaaaaaay hotter than any forge table should ever get) he shouldn't have trouble. (Then again, maybe the owner of the table is building much larger fires on it than he should, and that's why it cracked in the first place.)My coal forge firepot is made from an old steel wheel. I have no trouble with the fire melting the steel or even making it red hot (cherry red is around 1400°F). The heat is in (and above) the fire, not below it.All that said, riveting in or bolting on fish plates like DSW has shown is probably the simplest, most reliable repair.With welding, I'd be more concerned about the weld confining stresses/strain to the point where, the next time the owner built a too-big fire on it, he'd get a catastrophic failure and the whole thing would break into pieces.Last edited by Kelvin; 03-05-2014 at 06:01 AM.
Reply:Tractor Supply, Farm & Fleet, Fleet/Farm and the one down South King Ranch(?)All these "Farm" supply stores carry small amounts of Cast Iron Welding rod.If your insistent on welding it, I have used Hobarts "Noma-Cast" with good success on difficult Cast Iron.