Dear ALL,
Happy New Year.
I am encountering a strange situation. I am working with welders who are able to get spray transfer GMAW without any spatter. I am finding it hard to convince them in using not more than 20% CO 2 during spray transfer. I don't have much experience in GMAW. Would like to know if we can weld a .5 " thick groove using Spray Transfer GMAW with CO2 without any problem. Any thought in this direction will be helpful to me.
Thanking you in advance.
sri
An Argon rich mixture (>75%) is needed to phase into a spray arc transfer mode. When you reach the transition current, the spatter and noise will cease. I've run spray arc with a 75/25 mix, but the arc is not as stable or smooth and some spatter is still present. It may jump back and forth between globular and spray transfer if the parameters are not dialed in properly.
There are several factors which determine this arc transfer mode:
voltage
current (amperage)
wire feed speed
arc travel speed
shielding medium
Some gas mixes also have a small amount of Oxygen (92% Ar, 6% CO2 and 2% O) which further enhances the arc stabilty and makes for a very nice bead with excellent penetration. This is assuming your welding steel. You'll want to check out the duty cycle of your equipment also if you have a lot of welding to perform. Miller and Lincoln both have excellent (and cheap) books on this very subject, or go to your Welding Handbook. There are tables in the Handbook which give you parameters to achieve specific arc transfer modes and the required gases, etc.
Thank you very much for the immediate reply.
I am with a different doubt now. I don't see any spatter . I am sure they are doing with 100% CO 2. Now , is it possible to verify if for sure it is a spray transfer or not. I am under the understanding that to weld 0.5" thick steel we require spray transfer and globular transfer can't be used. Please clarify on these 2 points
(1) How to verify if it is spray transfer or not
(2) Is it possible to have a good weld on a 0.5" thick steel using globular or short circuit. --- the problems to be anticipated, if any.
Thank you
sri
There have been numerous posts on this subject, search through past threads and you may find specifics. In a nutshell, it is possible to weld a 1/2" plate with any GMAW arc transfer mode. If the welders are indeed in spray transfer, there will be little to no spatter and little noise except a smooth "hum". If they are in globular, there will be noticable spatter and noise.
Check the welding parameters against the tables I mentioned previously. You have to have a minimum voltage value for a given wire size (diameter), wire feed speed, etc. to phase into spray arc. If you have a amp/volt meter, these parameters may be confirmed.
By galdad
Date 01-20-2002 17:46
Your boys might think they're in Spray transfer, but they aren't.
You need Ar to get into spray because of it's ionizing potential.
By -
Date 01-03-2002 19:03
As far as I am concerned, you can not achieve spray transfer with 100% CO2.
To check in which transfer mode you are, let the welder set the machine as he would normally weld. Then check the voltage. If there is little spatter, I would assume it is actually in dip transfer. Dip transfer would typically be below about 24V.
If it is below this voltage, let them increase the voltage and see what the result is. I would guess that you will then start to move into globular transfer at which point the spatter would increase.
If you measured the voltage and found it around 28V or so, without spatter, then I would have to say that you are in spray transfer. In this case, make absolutely sure what gas you are using. I would guess that it is not 100% CO2.
Regards
Niekie Jooste
Thank you very much.
After going through Filler metal guide by AIRCO, Welding handbook and texts from www.taada.wsu.edu/2001/MIG/section2.html
a paper published by the US military , I think we are infact doing a buried arc classified under globular transfer .
It seems to be also called as repelling transfer wherein there is an initial thrust against the weld pool. This" reverse thrust is decimated by increasing current. This is suppose to increase spatter when used with 100% CO 2 , and so my welders have been getting closer to the weld pool. After saying all these, I hope it is burried arc of globular transfer.
I am trying the suggestions given by both DGXL & Niekie.
Thank you .
