Testing a welded joint....
Tue, 31 Aug 2021 16:23:32 GMT
I want to stress test some of the welds I've done and was wondering what I should do If I'm able to crack or even break apart a weld? I'm using 3/32 rod at around 150-180 amps right now.Should I re-weld the same joint(s) that failed with more current?or...Should I grind down the old weld-pool(s) on the failed joint(s) then start over with more current?or..Should I be doing something different?Thanks!
Reply:Something different. 1/8 rod runs around 125 amps so you already are running too hot. Are you getting a lot of spatter adjacent to the weld bead? More current is not the answer.
Reply:Assumptions and info needed: You are runnning stick (SMAW--from the word "rod"); your current is remotely accurate;You are running a common standard rod type (what rod are you running? 6010? 6011? 6013? 7018? 8018? 7014? 7024? a stailess? other?); the rod is really 3/32, not 1/8, 5/32, or 3/16Oy! 150 to 180 amps on 3/32? I don't know of any rod where this is not way too high a current (but will not exclude the possibility) for many common rod types (ex: 7018) 3/32 should be run at about 70 or 80 amps (typical range 60-100A) and some (like 6013) run a bit lower. At a current that high, you would have to run tremondously fast, the rod would rapidly be glowing and spalling flux, and the arc would be REAL angry, with tons of spatter. There wouldn'tt be a controlable puddle. Fusion would be erratic and the slag would not have a chance to float out, leaving crud and inclusions in the weld metal.Symproms that you are too cold (too low a current) are that the weld metal doesn't blend well, the bead tends to be proud and narrow, the puddle tends to be sluggish and tough to maintain. Note that the puddle should be visible as a shiny pool nearly under the arc. It has a different look than the molten slag. As you move the arc, you should see some of the base metal melt into the puddle at the arc boundry (most rods this is visible, but not extensive. Some more agressive rods, like 6010, it is quite pronounced and without practice, can make it difficult to get any fill in the weld) Try: starting at about 40A and run a few beads. Up the current 10 a at a time and run a few at each current up to, say, 150A. The speed at which you move with 3/32 should be such that you burn a full rod in about a minute. This will vary a fair bit from welder to welder and job to job, but if you are burning the whole rod in 15 seconds, you are WAY too hot. 3 minutes, way too cold. Ya, I'v seen both. Kinda fun to watch. For most steel rods, the motion should be fairly smooth and steady, with a ocnstant arc length about the same as the rod diameter (NOT including the flux) For a few rods (6010 and 6011 being common) yuo use a 'whip and pause' technique where you periodically whip the arc a few rod diameters ahead of the weld pool just long enough for hte pool to begin to solidify, then bring it back slightly ahead of the old pool. Typical whip time maybe 1/2 sec out and back, pause to form the pool about 1 sec (times are subjective. I never actually measured) A good welder can run a good weld with current setting a fair way from ideal by controing the arc length, rod position, travel rate, etc.
Reply:Enlpck,Thanks so much for the info. What you''re saying is exactly what I've been doing. I was using 7014 3/32 rod on a stick machine up to 200 amps. I was using a high current because at lower settings the rod would just stick to the work I was trying to weld. Last night I tried dropping the current down to 100 AMPS and I found it hard to strike and get an ARC without it sticking, but after trying for awhile I got the hang of it (I was tapping the tip of the rod, rather than striking it like a match -- I remember someone saying it was more like striking a match and it seems much easier that way) Anyway, after figuring out how to strike an ARC, I noticed it was MUCH MUCH more controllable. I could actually see my Weld pool form -- Before the ARC was very "angry" like you described and I had to move very fast otherwise I'd burn through the material. I think I;ve also been doing something else terribly wrong. I've been making several passes on my weld joints without chipping of the slag in-between each pass. Do you know what the result of that is? It appears after I realized you need to remove the slag, I've found that my multi-pass welds look very pitted, and cratered, etc. I assume this is because I was welding over the slag from my previous passes? Thanks so much for your help because I've really noticed a major improvement running at 100 AMP vs. 200 AMP. I think I need to understand better what I need to do for multi-passes, and building up welds that require more than one pass, etc. Originally posted by enlpck Assumptions and info needed: You are runnning stick (SMAW--from the word "rod"); your current is remotely accurate;You are running a common standard rod type (what rod are you running? 6010? 6011? 6013? 7018? 8018? 7014? 7024? a stailess? other?); the rod is really 3/32, not 1/8, 5/32, or 3/16Oy! 150 to 180 amps on 3/32? I don't know of any rod where this is not way too high a current (but will not exclude the possibility) for many common rod types (ex: 7018) 3/32 should be run at about 70 or 80 amps (typical range 60-100A) and some (like 6013) run a bit lower. At a current that high, you would have to run tremondously fast, the rod would rapidly be glowing and spalling flux, and the arc would be REAL angry, with tons of spatter. There wouldn'tt be a controlable puddle. Fusion would be erratic and the slag would not have a chance to float out, leaving crud and inclusions in the weld metal.Symproms that you are too cold (too low a current) are that the weld metal doesn't blend well, the bead tends to be proud and narrow, the puddle tends to be sluggish and tough to maintain. Note that the puddle should be visible as a shiny pool nearly under the arc. It has a different look than the molten slag. As you move the arc, you should see some of the base metal melt into the puddle at the arc boundry (most rods this is visible, but not extensive. Some more agressive rods, like 6010, it is quite pronounced and without practice, can make it difficult to get any fill in the weld) Try: starting at about 40A and run a few beads. Up the current 10 a at a time and run a few at each current up to, say, 150A. The speed at which you move with 3/32 should be such that you burn a full rod in about a minute. This will vary a fair bit from welder to welder and job to job, but if you are burning the whole rod in 15 seconds, you are WAY too hot. 3 minutes, way too cold. Ya, I'v seen both. Kinda fun to watch. For most steel rods, the motion should be fairly smooth and steady, with a ocnstant arc length about the same as the rod diameter (NOT including the flux) For a few rods (6010 and 6011 being common) yuo use a 'whip and pause' technique where you periodically whip the arc a few rod diameters ahead of the weld pool just long enough for hte pool to begin to solidify, then bring it back slightly ahead of the old pool. Typical whip time maybe 1/2 sec out and back, pause to form the pool about 1 sec (times are subjective. I never actually measured) A good welder can run a good weld with current setting a fair way from ideal by controing the arc length, rod position, travel rate, etc.
Reply:Ok. Now I see where you are at with the process....Some rods strike by tapping ok, others won't at all. 7014 is a little sticky, and is easiest (for me) with a small scratch. I tend to scrath in the direction of travel, rapidly back up to the start point for the weld, wait for the pool to form, then move. Does your machine have a voltage control (sometimes labeled arc force, dig, or other various things, though these controls vary more than just voltage) This controls the open circuit voltage which affects most prominantly ease of strike (higher voltage is easier), the arc stiffness (roughly how the current varies with arc length, higher voltage giving more variation, leading to the dig effect), and the digging action (related to the current variation with arc length-more dig tends to burn in more because as the arc is shortened, current rises more) try different settings if it does and oobserve the effects. There is a balance between many of the characteristics, and many modern machines have 'hot start', which gives a higher votage for a brief time at the strike to ease arc initiation, then backs off a bit for a more stable current and softer arc (tech point: wht is actually varied on modern machine is the relationship between voltage and current: the curve is steep for the hot-start portion, giving more current variation with arc length and higher initial open circ voltage, then flattened during the running portion of the weld. Ain't modern electronics great?) Some rod also have a hot start designed into them, which essentioally is a flux treatment that helps with the strike.I grew up with an ancient transformer machine with plug select current and no voltage control. Damn did I love moving on to machines with some operator controls.
Reply:Originally posted by Plasma Pancake Enlpck,I think I;ve also been doing something else terribly wrong. I've been making several passes on my weld joints without chipping of the slag in-between each pass. Do you know what the result of that is? It appears after I realized you need to remove the slag, I've found that my multi-pass welds look very pitted, and cratered, etc. I assume this is because I was welding over the slag from my previous passes? .
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