Vertical uphill MIG

[Mid Wales welder]

I tried to do some uphill welding for the first time in years the other day & all though i got plenty of penetration it was beading up in the midle! I think that my technique is fine (upside down V & getting into the sides well) but just can't seem to get the setup right. I'm using a kempoweld 4000 with the 400 wire feeder set on 3,2 & wire speed 6 m/min (sorry I don't know how many amps that is) & I was welding 6mm plate in the T-fillet position. would anyone be able to shed some light on the problem please? Any info would be much appreciated! Thanks.

 

[backpurge]

At each point of the V pause for a count of around 2 seconds then move as quickly as you can to the next point of the V without breaking the arc

With regard power settings, the same set up as you would use on sheet metal usually give you a good start point, once you get it running something like, try playing around with the inductance settings

You didn't say what gas you were using but Argoshield Light or equivalent aill be easier to use than gases with a higher CO2 content

Some piccies may help as well

 

[matt1978]

Higher C02 levels are easier for positional welding, Lower percentage mixes tend to be very fluid and not great for doing vertical, but your right in the sense that Argo light etc is generally best suited for thin sheet

 

[Mid Wales welder]

At each point of the V pause for a count of around 2 seconds then move as quickly as you can to the next point of the V without breaking the arc

With regard power settings, the same set up as you would use on sheet metal usually give you a good start point, once you get it running something like, try playing around with the inductance settings

You didn't say what gas you were using but Argoshield Light or equivalent aill be easier to use than gases with a higher CO2 content

Some piccies may help as well

Thanks for the info, I had another go today briefly, turned the setting down to 18volts & wire @ 5 m/min, didn't pause for as long as two seconds tho maybe about a second counting 1001, 1002 etc moving quickly as possible to each point. Turned out pretty well, quite smooth! Guna keep practicing tho! The only way I can control the inductance is putting the earth in either the I or II socket, I had it in the I socket for lower inductance which am I write in thinking is better for uphill? Oh yeh, I was using argosheild light gas set on 18.

Regards

Dave

 

[matt1978]

You want the higher inductance setting because you are in short arc/dip transfer

 

[Mid Wales welder]

You want the higher inductance setting because you are in short arc/dip transfer

Rite ok, I new it had to be 1 or the other! Is that coz higher inductance makes the pool less fluid? Like I said in last post the way I can set inductance is by swapping the earth over & it's hard to do with my welder coz the leads a bit dodgy, I'll giv it a go tho! Low inductance is best for thinner metal upto 1mm wire, is that right? Or is it the other way round?

Regards

Dave.

 

[shenion]

Higher inductance give a more fluid weld pool. It increases the arc current (vs the short current).

It depends on how low the "low" setting is. Most with two settings, the low inductance is too low for dip transfer to be smooth as it is intended for spray transfer.

 

[backpurge]

Higher inductance give a more fluid weld pool. It increases the arc current (vs the short current).

It depends on how low the "low" setting is. Most with two settings, the low inductance is too low for dip transfer to be smooth as it is intended for spray transfer.

You learn something new every day, I had always thought inductance controlled the speed with which the wire heats up when it short circuits and therefore would not make any difference when you are in spray as the only time the wire short circuits is when you initially strike up. Ta for that

 

[matt1978]

Inductance controls the "current rise time" so you want a higher inductance for dip transfer due to the constant short circuiting of the wire with the work piece.

With Spray you don't need a high inductance because apart from the initial strike up the wire shouldn't touch the weld pool much as the higher voltage levels burn the wire off much faster

 

[shenion]

Yeah, spray will work with just about anything. I have done it on my Airco that has a huge inductor (size of a car battery.)

I have seen this but can't fine a reference to it: the lower inductance seems to cause the mode to transition from short-arc to spray faster. On the Airco, there eas 2-3 pops before it went silent in spray. My Miller on the low inductance setting would just pop once.

I get the feeling it is to prevent a ball from forming at the end of the wire on the first hit.

You are right, the inductance controls the time the current ramps up in short-arc. Without it, the current spikes so high as to explode the weld pool and throw bit of wire all over. When the ball melts off the end of the wire and an arc forms; the energy store in the inductance maintains a higher arc current. This added current wets out the weld as it provides heat to the weld pool.

My Miller did not have inductance as it was spray-only (but never said do in manual.) Spent a day scratching my head as it left cold welds and spattered everywhere and sounded nasty. I wrapped about 10 turns of the return lead around an old crankshaft. Welds were now smooth with a soft buzz. The current meter nearly doubled.

 

[backpurge]

Going off topic I know but back in the day when we used to stove full pen root runs in 36" pipe connectors for the offshore industry we always used to use the lowest inductance setting so the weld "held up", but hey, if we were doing it wrong we were doing it wrong, still never had owt fail bombing, must have been lucky I suppose

 

[Mid Wales welder]

Thanks to everyone for all the info, very interesting! I work as welder fabricator (with the enthasis on fabricator) so do alot of mug welding but all just straight forward stuff so all the welders i'v ever used in the workplace have always been pretty simple so never really heard of 'dip transfer' & 'spray transfer'. Would I be right in thinking that these are terms for when you weave the weld (dip transfer) & when laying a straight bead (spray)? Also is it low or high inductance that controls spatter? also what does the term short arc mean? Sorry for all the questions & I'm sure i sound really dense about all this! I did welding for two years in college but didn't go straight into work & that was 10 years ago so I have forgotten everything. I found my passion for it all again now tho! again all the info is great, thanks!

Regards

Dave.

 

[shenion]

In dip transfer (also known as short-arc) mode, the wire touches the weld pool, the current goes way up and a ball forms at the end of the wire, The high current pinches off the ball. An arc forms as the wire melts back to form another ball. During the time the arc is present, the weld pool is further heated and it flattens out. The short-then-arc gives the charactistic buzz and sizzle of the mode. It is a rather violent process and there is usually some spatter.

In spray transfer the wire never touches the weld pool. There is always an arc. The current is high enough to pinch off small droplets of wire (about the diameter of the wire). These droplets are propelled to the work via electrostatic force. The arc sounds like a soft hiss. A much higher voltage than short-arc is needed for this to work. As argon conducts current better than CO2, a low CO2 gas is used. As there is always a hot arc, spray transfer has a lot of heat and penetration.

Because the droplets are transferred by the weak electrostatic force, spray transfer does not work well for positional welding. Horizontal and sometimes vertical daown are all that are used.

Not mentioned is globular mode transfer. This is between the two. It may look like spray but the droplets are erratic sized and don't transfer well. There will be considerable spatter. It is avoided by using different size wires and high-CO2 gas mixes to keep the mode in short-arc.

Short-arc transfer needs the inductance, spray transfer works better with less.

Spray usually occurs around 200 amps and up. The actual current/voltage depends on the wire size. So it is not use for thin metal. New "Pulse" MIG machines can do short pulses of high current to do spray but keep the average current low. They can also do dip transfer in a more controlled fashion. One pulse per droplet.

 

[tombardier]

This 'pulsed arc' transfer is actually spray transfer then? (cool vid btw)

http://www.youtube.com/watch?v=LMnRRx1popU