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When I bought my new Lincoln 216 welder, I also bought an 11 pound roll of ER-70S-6 wire.  I bought a metal gauge and estimated that the project at hand was about 1/4" metal thickness.  The chart on the machine called for a "D" setting which is about 4 out of 6 possible settings.  (Can't remember the wire feed speed off the top of my head.  Seemed to work out okay.)  Didn't get much splatter. 

 

If there are concerns over the integrity of a weld, how could one strengthen the weld?  Would you choose to build up a higher crown with a hotter setting, broaden the base of the weld, etc.?

 

David

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David...The width and depth of a weld determines the heat (voltage/amperage) setting.  Wire diameter is another factor.  The pace or travel speed of your weld, including the side-to-side or "C" movement of the torch, determines the weld puddle size and the amount of metal deposited.  For wire feed MIG welding, filler deposition is also a function of the wire spool-out speed.

 

So, in the weld project you just completed, the weld's width and depth determine the stamina of the weld.  A single pass is possible with this machine.  There is the option of making three passes:  1) a burn-in root pass, 2) a second pass from one side to just over the center of the "V", then 3) the opposite side weld burning into both of the other two passes.  Many avoid the structurally sound multi-pass approach because they want a single pass "look".  Large pipeline welding without voids is always multiple passes...Regardless of your motive, the single pass can work, especially on 1/4" depth metal, if you meet these criteria:

 

1)  The weld burns to the root or very bottom of the metal.  Whether a flat weld or the radius of tubing, burn into the metal enough to show filler reaching just through the bottom of the metal mating junction. If you do this, the finished piece will have more thickness at the welded section than those metal sections that are not welded.

 

2)  There is a "normal" crown on the weld.  A single pass crown should bridge the top of the "V".  There should, optimally, be no gaps at the weld edges.  The weld edges should look seamless with the two pieces of joined metal.

 

3)  Avoid undercut grooves at the weld edges.  Undercut is undesirable and usually indicates excessive travel speed of the arc rod or torch, or too little filler entering the puddle from lack of heat.  (Along with undercut, there is often a weld crown with an exaggerated height and narrower width.)  An undercut area would be a weakened section of the weld:  The thickness of the welded piece is thinner at the undercut areas, and this means the metal's strength has been diminished.  Avoid craters at the end of the weld bead(s) by allowing the filler to puddle there; the crown should be uniform height and width, even if you stop and restart a bead.  Something to practice.

 

The weld crown will be just right every time if the heat (voltage/amperage), feed speed and wire size are correct—and if you move the MIG torch at the right pace.  A MIG bead will appear right if you move the torch head properly.  Your new Lincoln machine's recommended settings are a reliable place to begin. 

 

On a butt weld with beveled edges, you can visualize the task as: 1) burn into the root of the "V" to establish full fusion of metal (which can also include fusion with a piece below the base of the "V") and 2) create a puddle without voids or occlusions, filling the entire "V" and also forming a correct crown—without weld edge undercutting.  Always penetrate the "V" root so that the weld is at least even with the bottom or backside of the piece.

 

Whether you succeed in doing this with a single pass or three passes, good results require the right machine settings and use of the right filler, correct heat and the right torch movement.  Other concerns with MIG (GMAW) are the shielding gas and positioning of the gas nozzle and tip.  This is critical.  In your shop, without moving air, there is less likelihood of losing your gas shield.  Be aware, all of this changes if there is moving air.  You need this gas shield to prevent oxidization, so make sure it's there!  To prove this point, run a practice bead on scrap metal both with and without the gas turned on.

 

Your use of ER-70S-6 is great for clean, new metal.  If you start fiddling with less than clean metal, you'll gravitate toward ER-70S-2.  As for any weld's integrity and strength, respect for metallurgy and the proper choice of materials is important.  Know the base metal's character and how your welds will impact tensile, ductility and the granular structure of the metal

 

I highly recommend some study of metals, their properties and how they change when welded.  Ignorance is not bliss.  For example, you're way ahead to know the difference between annealed, normalized and hardened (case or through hardening) metal properties.  Welding and the filler material impact the base metal, and the biggest concern is the character of the finished metal piece.

 

For judging a weld properly, there are three traditional tools.  When you practice with your new machine, consider these approaches: 

 

1) Cut the piece perpendicular to the weld with a band saw.  Examine the cross-section of your weld and the adjacent fused metal.  There should be no parting lines or voids, and the metal should look like one continuous, fused piece.

 

2) Bend the piece to the point of destruction to see the weld's character in that process.  Where did the metal fatigue?  Break?  Shear or stretch?  Keep in mind that welding is a fusion process, and metals should flow fully together.

 

3) X-ray analysis used in commercial, critical welding.  This is done on pipe and high strength aircraft, nuclear or steam welding.  Metal materials welded with specific filler get studied.  Finished pieces are sometimes X-rayed in place (like high pressure pipeline) to check integrity and make certain the pieces will hold up in service.  This is a commercial approach for specialized welds and weldor certification tests.

 

Your real concern with a weld is how well you fused the metal and how you impacted its metallurgy.  Proper weld machine settings, correct filler wire or rod choice and the method of cool down each play a role.  If the metal's tensile or surface hardness is critical, you must cool or treat the metal properly.  In special cases, this begins with a trip to the heat treating shop to normalize the pieces; following the welding process, there will be a return trip to the heat treating shop for heat treatment. 

 

These are some of the concerns with welding.  Let's continue the discussion as you use your new welder!

 

Moses

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