3/4" Plate

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I need a starting point for welding some 3/4" plate steel on an industrial washing machine (machine capacity 400 lb/hr). A few of the factory welds have cracked due to age, vibration, etc. The deck around the bearing support is cracked in the center of the weld. The end result is I need to air arc the old welds and reweld them. Would one of you who is used to working on heavy steel like this kindly let me know what size rod and amperage would most likely be required.Thanks in advanceWashman
Reply:My 1" test plates were done at 117 amps with 1/8" E7018 DC+, multi-pass, in the vertical. Overhead was done @ 120 amps. Lincoln V350 inverter.Edit:- Preheat the weld zone to 150 degrees.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:The Lincoln procedure handbook of arcwelding recommends 4 passes of 1/4" 7028 @ 350 amps for a fillet in the horizontal position.   OR for the same position, 4 passes of 1/4" 7024 @ 375 amps.Verticle up fillet, 2 Passes 5/32 7018 @ 150 amps. ( I can do it at 140 amps but not 150 ) 5/8 size fillet.Verticle up fillet 3 passes 3/16" 6010 @ 160 amps.Flat position fillet 4 passes 1/4" 7018 @ 350 amps.The above are for production welding on that size plate. There are more and the out of position joints are more sensible size electrodes and amperage.I could go on.  If you run 1/8" 7018  I would go for at least 140 amps, up to 160 amps if its flat.  Preheat would help reduce stress and cracking.  We don't know what the plate is, so I ASSume its mild steel.  I do quite a bit of out of position with 3/4" plate.  Everything depends on exactly what you are doing.  If its flat you can crank up the heat, but you can also over heat the plate or pull it out of alignment especially since you are holding a bearing.I would gouge the old stuff out, grind if you can and weld it with 7018.  Take your time and make many passes.  What position?  What type of joint was it? Got pics?DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Thanks for your help guys.....I certainly appreciate the input... Half of the welds are vertical under the washer behind piping that can not be removed ..... Seems to be the way a lot of machinery repairs go ...unable to get to the problem to do it properly.The material is mild steel, exact composition is unknown.I tried some of the vertical welding with 7018 at about 120-135 amps.... I first tried 135 then 120 amps. With the higher aperage it melts the rod quite easily but the base metal is a little harder to bring to the melting temperatureas you might suspect. In other words the edge of the puddle area is somewhat cold while the filler part of the puddle is too hot and tends to sagConsequently it is very hard to get a vertical up weld without sags in the bead and poor penetration along the edges..The problem I was experienceing was more of an issure of a cold edge on the weld bead. Although it appears to be a very solid weld it does not appear to be properly fused at the margins (the edges).I thought perhaps that a larger rod would melt slower and allow more heat to be used in order to properly blend or fuse the edges of the weld.I thought that perhaps if I could use more amperage and a larger rod I could get a little more heat into the weld to properly fuse the edges (you know melt them in) seems like 1/8" rod melts to easily when doing vertical on this size material.It sounds like I need to try a 5/32" rod with approximately the same amperage setting.Thanks guys for taking your time to help out with this..... Washman
Reply:Well, Let me start by asking, are you welding with an upward progression, or downward?  I personally would take a 1/8th around 130 amps welding vertical up.  Sounds to me more like a problem with your technique. When you weave you need to angle your rod into the edges and pause slightly before moving back across to the other side.  If you stay in the middle too long you will see the puddle fall back and drip.  if you can't apply enough heat to the joint for proper fusion then you need to pre heat or go up in rod size and amerage.  But keep in mind a larger rod will be harder to control.  If you could post some pics it might help in diagnosing.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:I agree, it sounds like a technique issue. Hold the rod pointed into the edge, also known as the "toe". Hold it there until the puddle just fills the new crater you just dug. When the puddle fills the crater, move slowly but deliberately to the other edge and repeat. Lead the puddle. Don't hesitate in the middle, he who hesitates, will sag! Rotate your wrist, as well as pointing into the edge, sort of like a parade wave, this helps to burn away the fingernail of flux at your rod tip.  Short arc gap now, almost scraping the puddle.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Originally Posted by tanglediver he who hesitates, will sag!
Reply:First I would like to say thanks guys trying to help out.That's what makes this web site so valuable, people who aren't afraid to help each other. I'm sure you have all worked with someone that would never give you a straight answer..... You know, they were always worrying about their job security. tanglediver  ....  thanks for the input I did think of preheating but the machine is fully assembled, painted and wired .... really can't preheat You are right however that I'm sure would help some.David R  ....  All good advice and it seems to go along with what I was thinking. To fill in a little more information ... The weld is in a corner it is vertical filet. There is a 4" pipe about 4" to the right of the area to be welded and the weld is approx six inches behind the pipe, under the machine and in a corner (in other words jambed behind the pipe). Hammack_Welding  ....  Definately up, bottom to top (don't quite see how anyone could do it top to bottom) although I'm sure some people here could do it.Preheating was my first thought but had to rule that out due to the machine being fully assembled and installed. That is why I asked about larger rod and perhaps more amperage. The biggest problem I see is that you can't angle the rod into the corners at the proper angle due to the piping that is in the way.David R  ....  Yeah buddy I like that one too .."He who hesitates will sag" I need to stop in at another customer a few blocks away in Atlanta so I will try to take some pictures. I didn't have the camera with me last visit.Thanks to all of you for taking your time to try to help out. You guys are great.  ......No smoke just fact..lolWashman
Reply:Yea, sometimes an obstruction in the way can be a pain as far as your rod movement.  Sometimes you can bend your rod, and get enough room to move your stinger.  It just wastes a lot of the rod, but you got to do what you got to do.  If that doesn't work you might be able to whip a 6010 or 6011 in that small area, but a low hydrogen rod is what really needs to be used in that situation.  I see you are in Georgia also.  What part of the Atlanta area are you in? ~JacksonI'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:You are welcome, of course! I know some of the pretzel logic behind contortionism and welding. We get to try a bit of overhead/under the axle/ next to the leaf spring/ up against the holding tank/inbetween the wire loom/just in front of the fuel line/sort of welding sometimes also! This is my classmate/workmate Adam, he hates overhead! City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Hammack _Welding:Yeah, It sure can add to the fun having something obstruct where your trying to weld thats for sure.. Of course I've seen guys welding in the mirror and do a beautiful job... personally I couldn't pick my nose in the mirror.  LOLOooo and I'm over in Lilburn east of Atlanta close to Stone Mountain.Tanglediver:I had to laugh out loud when I read your response about working under the truck .... so funny but yet so darn true...Bye the way I'm sure somebody must like to do overhead, but I haven't ever met him or her.Washman
Reply:If it can handle the heat of welding on 3/4" plate then you can preheat it.  Ditch the weedburner and use an oxy/acetylene torch and keep it on a low setting.  You only need to get it to 150 degrees.  Paint won't even burn at that temperature so it shouldn't be a problem.
Reply:For preheat, try electric strip heat pads. Borrow, rent, or buy. Quite handy, and makes a huge difference. Example:http://www.mcmaster.com/ctlg/DisplCt...MMainWidth=920