welding on a disc from a plow...

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Are the metal discs on a metal farm plow made of a "hardened" metal ? I used one for a base on a fence wire roller project. I welded the disc to a frame , but my welds broke. I had what I thought was good penetration. It just came loose at the welds ?  Using a MM210 , plenty of heat..Any thoughts ?
Reply:This may be helpful.http://bbs.homeshopmachinist.net/thr...scs-made-from?
Reply:Pictures would help.Did it break in the middle of a weld or right next to the weld?Metal tends to break at the weakest point.  Once a crack starts, it only gets bigger.Did it break in use or just because you let it cool down?  Yes, depending on how fast something cools down, it could fracture depending on how its constrained.As for is it high strength steel.  Maybe.   Could also be stainless.   Most steels that are indended to hold an edge are of higher strength - typically hardened steel.  This is done by adding material like carbon, boron etc. to the steel and carefully controlling the crystal structure inside the steel by heat treating etc.How you weld something like that depends on what you want to do in the end.  If you are going to heat treat it again, your filler should be a very close match to the base material and/or contain a reasonable amount of nickle.   You'll find lots of options for welding different steels and cast irons in stick welding product catalogs.  Each of the rods will talk about pre and post treatment of the metal (pre-heat vs. post heat vs. post heat treat).If you are unsure.  A high nickle filler or 312 or 309 stainless (also high nickle) will probably get it done.   Again assuming enough heat to penetrate.Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:You could spark test the material to try to determine its carbon content.Another approach, that I learned from Jody at weldingtipsandtricks.com is to use a TIG gun to very quickly make a puddle on a section of the base metal, at a corner or edge, then immediately break the arc and let the puddle cool. If the metal is high-carbon, this will harden it, which can be determined by taking a file to the spot where you made the puddle. If it files easily after puddling, it's low-carbon. Of course, this approach requires a TIG gun, and, optimally, HF start.
Reply:I've heard to use er310 on high carbon steel (assuming it is high-carbon). With 25% Cr and 20% Ni it is very ductile, even if it picks up some carbon from the parent metal.
Reply:the discs are med carbon and are heat-treated. allied products ( now defunct) in south bend,in used to make some of them.they would pre-heat the round blanks in a furnace and hot stamp the disc--almost like a forging process,but it was just hot stamping.miller thunderbolt 250vlincoln square wave tig 175 prolincoln idealarc mig sp250everlast tig 210EXTeverlast power plasma 50chicago electric (hf) 130 tig/90 arcchicago electric 90 amp flux wire3 sets oxy/acet
Reply:I've welded mouldboards with 7018, and had real good luck.I think the reason I had good luck was that I used a mild steel backing.Was a break due to the mouldboard wearing thin where the soil scrubbed it over the years.  Shins are real bad about this tooI cut a rectangular piece out of the mouldboard, then placed the mild steel patch behind it, then welded it up.  I filled in the patch with padding, same 7018.From what I understand, 7018 is very good about allowing for an admixture of metals.  The base metal, and the filler metal.  It's a reason it's good for hard to weld metals.I would imagine the mild steel, filler metal, and base metal, combined at the weld, and produced a decent repair.  Over the years I had to repad the patch area because the 7018 wore with scrubbing, but the patch is still there to this day, and there's been no breakage."Any day above ground is a good day"http://www.farmersamm.com/
Reply:I have always used 7018 to weld to disc blades. Never for repair but for projects like hose holders, pipe bases for boat docks and disc blade cookers.  Never had a failure yet. Dan
Reply:The edges of the disc are considerably harder than the rest of it. If you keep the welds back from the edge a couple of inches and use 7018, you should be fine.