Metal transfer modes

[Echidna]

Hi experts!
I would like to ask you this.
How can someone switch to different modes of metal transfer in MIG? Are these modes distinct and easily switchable?

Short-Circuit Metal transfer
Globular transfer
Axial spray transfer
Pulsed spray transfer

Do i make a big mistake or it is impossible to switch to a different mode, unless there are some welding "conditions" present?

 

[ashy]

Take a look here mate, gives loads of info: http://www.esabna.com/EUWeb/MIG_handbook/592mig1_1.htm

 

[shenion]

There are two things to control the transfer: the gas and pulse mode.

Spray-arc will not occur with more than 15% CO2.
Pulsed MIG allows spray-arc at a lower average current.

Both are used to avoid globular transfer.

I was just at a shop that made large square tanks out of 3/16" steel. They were using current just at the spray-arc threshold. As most of the welds are vertical, they do not want spray-arc. The gas was 75/25 Ar/CO2.

 

[Drains]

You do get a pseudo spray arc with greater percentages of co2.

The different transfer types are attained by setting different voltages on your machine. If you didn't know, that's what is altered by the controls on migs (NOT current, as many people think)

Basically, at greater than 27v (or so) Open Circuit Voltage, you will get spray arc. A bit below that, globular, which is unstable and spattery, and below that, dip/short circuiting transfer.

For pulse transfer, you need a pulse mig set.

Most smaller DIY/ single phase Mig machines are only capable of dip transfer, as higher amps are necessary to support the greater wire speed needed with the high volts on spray.

Spray is also used only on downhand welding, with non flux cored wire.

Spray can be used on thinner materials, but a very fast travel speed is required.

 

[panaya]

Let me know,what is your wire diameter and I`ll tel you range of the spray transfer.

 

[Echidna]

Let me know,what is your wire diameter and I`ll tel you range of the spray transfer.

0.8mm

 

[matt1978]

Spray arc is not dictated by the Co2 values in the shielding gases. It is the Voltage that you are using from your mig set. It would be possible to get into Spray arc using 95/5 mix, but not preferable (But not impossible)

Anyway,

Short arc/Dip transfer is where the wire short circuits by touching the weld pool, this causes the short circuit, the current rises rapidly and then the wire breaks off/detaches. This arc phase is good for welding thin sheet or bridging gaps.

Globular/Mixed arc, is the phenomenon which occurs between the Short arc and Spray arc modes. Its not something that you would actually choose to weld in. Its when you have too much voltage to remain in Dip transfer, but not enough to be in spray arc. This condition gives a lot of spatter and quite an unstable arc.

Spray arc, is when the wire is detached in very fine balls, through the arc, so the wire does not actually come into contact with the work piece (Apart from ignition) as is the case with Short arc. This welding condition gives very little or no spatter but is only suitable for heavier section plate work (Beacuse of the Voltage and Wire speed required)

Pulsed arc, was developed to overcome the Mixed arc/Globular range of welding. It is a Artificially created spray arc, so it is possible to weld even thin sheet section with a type of Spray arc and does not give hardly and spatter. Its caused from using very high peak currents (Sometimes up too 600amps) but only for a very short time (Milliseconds). It gives really good results on Steel/Aluminium/CrNi etc. With Pulse it is possible to weld thin section with a large diameter wire (Eg, 1.2mm wire, to weld 0.9mm Sheet) However there is no real advantage on welding very heavy Steel sections 15mm > because it can actually be a slower process than could be achieved with conventional mig.

Additionally there is now Twinpulse. This was developed by Lorch, and it is conventional pulsed mig, with a low frequency pulse superimposed over the top of it. So you have pulsed mig, but the wire speed/Current is also pulsed. So you weld between a high value and a low value as with Pulse on tig. Apart from Metallurgical advantages on some materials, this process also makes the weld pool very controllable and offers a cosmetic finish comparable to tig welding. Especially on CrNi and Aluminium's.

 

[shenion]

Spray arc is not dictated by the Co2 values in the shielding gases. It is the Voltage that you are using from your mig set. It would be possible to get into Spray arc using 95/5 mix, but not preferable (But not impossible)

The gas has an effect. If you are running a voltage that would get into globular transfer, using a higher CO2 content will keep it in short arc transfer.

As CO2 has a lower arc current, it requires a higher voltage to reach the globular/spray modes.

I never meant the mix controls the mode, but that it effects the current/voltage levels that the modes occur.

 

[matt1978]

I never said that the mix does not have an effect I just said that it was not impossible to get into Spray with a low percentage of Co2.

 

[panaya]

Echidna,you can not achieve spray transfer with this diameter.You can use it only for small thicknesses<=0.9mm.For thicknesses>1mm you better use 1mm wire.With this diameter/1mm/ you can achieve spray transfer at 200amp and more /10.7m/min;25-28volts;wire stick out 16mm/ for thicnesses 2-3mm.
Success

 

[matt1978]

Echidna,you can not achieve spray transfer with this diameter.You can use it only for small thicknesses<=0.9mm.For thicknesses>1mm you better use 1mm wire.With this diameter/1mm/ you can achieve spray transfer at 200amp and more /10.7m/min;25-28volts;wire stick out 16mm/ for thicnesses 2-3mm.
Success

Every wire diameter can be got into a Spray arc. Even 0.8mm. Its when your welding around 3-4mm plate with 0.8mm dia wire, you will be in spray.

 

[Echidna]

So, to get into spray mode, what should be the thickness range of the plates, the diameter of the wire and what gas?

 

[irondarren]

if i remember correctly, spray transfer starts to occur at around 27-29 volts and on 1mm wire up wards, 27-29 volts is around 300 amps

 

[panaya]

Echidna,please look at http://weldreality.com/WELD PROGRAMS.htm and http://weldreality.com/spray_transfer_above100.htm

 

[matt1978]

if i remember correctly, spray transfer starts to occur at around 27-29 volts and on 1mm wire up wards, 27-29 volts is around 300 amps

Spot on, Spray arc is between 27-45 volts.

 

[Echidna]

How do you correlate Volts with Amperes?
My MIG is able to hold a 145A maximum. Should i forget spray transfer?

 

[irondarren]

If i remember correctly and i doubt i do the formula for mig is Base voltage 14 and then 0.05volts per amp there after. so at 30 amps it should be 30 x 0.05 + 14 = 15.5 volts at 145amps it is 145 x 0.05 +14 = 21.25 volts. Im not 100% sure if the formula is correct but i think its close, if your lucky someone might post the correct one. But at 21volts you are a long way from spray transfer, and stuck in dip transfer. hope that makes sense

 

[matt1978]

What thickness material are you looking to weld? If you repairing car bodies then this is all hyperthetical anyway, you wouldn't be able to get into spray arc welding such thin sheet because you would burn through.

 

[irondarren]

For such thin materials as Matt says, spray transfer is basically impossible because as it will burn holes in the sheet because of to much heat. The only way to achieve spray transfer on sheer is with a pulse synergic machine, which by clever electronics momentarily increase the voltage into the spray transfer area, then drops the power back down. This has the effect of producing spray transfer but at reduced heat. Having said that a pulse machine is likely to set you back close to £2000, or about 3200 euro's for a small basic machine a little expensive for car repairs

 

[TechnicAl]

How do you correlate Volts with Amperes?
My MIG is able to hold a 145A maximum. Should i forget spray transfer?

If you use 0.6mm wire and Argoshield gas you should be able to get into spray. Turn the thing upto max on both Wire Feed speed (current) and voltage.