Stainless mig question

By ssbn727 (*****)

Date 11-02-2003 16:10

Hi Motohead1!
Whenever one welds mild stl. to 304 stainless or visa-versa, there is a difference in the 2 metals Coefficients of thermal expansion so certain countermeasures must be taken in order to avoid cracks that can occurr... However, you did say holes, am I correct?
If these are indeed holes then, gas mix, gas coverage as a result of your gas flow rate from your gun can cause what you're describing as porosity!!! A 90% helium with a balance of 10% Argon gas mix does'nt sound right to me and yet, could that be a typo on your part?
Check your gas mix/choice to make sure that it's the correct mix/choice for this application. If this is the correct mix/choice, then check your flow rate first at your flowmeter (Measured in cfh) and if it's the correct rate (I'm presuming that you know the correct flow rate) then concentrate on your connections from the flowmeter to the machine and from the gun connection to the machine all the way up to the inside where the gas diffuser, insulator inside where the the copper gas shielding cup fits on the gun itself to see if there is any blockage from spatter deposited on the surface of the diffuser (which could be blocking the orifices that enables the shielding gas to flow out from the cup), from previous welding...
Hope this helps!!! Look foward to reading more soon!!!

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By - Date 11-02-2003 16:30

what is a 135 "pro" millermatic?...is that new cuz never heard of pro word being used.where can i get a pro miller 135 mig?

By Motohead1 (*)

Date 11-02-2003 18:36

hey guys thanks for the replys. AS you can tell I am very new welding. :) According to the primitive chart in the manual 304 stainless calls for a tri-mix of 90% He/ 7.5% Ar/ 2.5% CO2. There is no chart for gas flow rate tho. I had it set at like 28psi witch now i beleve was the problem after seeing your reply and looking at the welds again. I think i had the gas set too high. also i was using .03 stainless wire on 20 gage 304 pipe. Is there anywhere i can get a chart for gas flow rates? or did i have the wrong gas mix to begin with? Man mild steel was easy but this stuff is kicking my butt! :)

BTW a 135 "pro" is a 135 with the reostate amperage knob on it instead of the selctor knob. also comes with a free cart too. Got it from national welders here in charlotte NC. ;)

By ssbn727 (*****)

Date 11-03-2003 19:09

Hi Motohead1!
Go check out: http://www,weldreality.com By world reknown MIG/Flux-cored expert, Ed Craig... I'm sure that you'll like what you'll find there!!!

You'll find the answers to most of your questions there!!!
As far as a chart goes, I looked at one in Howard B. Carey's book "Modern Welding Technology" 4th edition, published by Prentice Hall... I looked in the back at thesheetmetal welding schedules chart and I found that for 0.030 wire dia. is recommended for 22 & 24 gage sheetmetal so, that could also be a problem.. try using a 0.35 dia wire. This means that you'll have to check to see if you have to change your drive rolls & associated parts, gun conduit, and contact tip...The chart lists for 16 &20 gage, volts should be set at 18 for 16ga. and 17 for 20ga. Amperage parameters should be 80-110 for 16ga. and 55-85 for 20ga. Both gage thicknesses require 20 to 25 cfh (Cubic Feet per Hour gas flow rate) and around 25 cfh should work well for the gas you're using because of the lesser density in Helium which would require a slightly higher flow rate... Remember that these voltage and current settings are probably for mild steel and not stainless so, experiment first on scrap to get the desired results bfore you start on actual production!!!
On your gas regulator you have a flowmeter, you should have a knob to set your flow rate and you should be able to read on the flowmeter in cfh. Set the ball in the flowmeter so that the bottom of the ball is resting on the line that corresponds to 20 - 25cfh start with 20cfh and weld a sample bead or joint with some scrap if available, then inspect your result to see if you have sufficient coverage. if you still see porosity then set the ball in the flowmeter to 25cfh. this should setting should provide you with adequate gas coverage...
Normally I suggest to my students to set the ball in the flowmeter so that the ball (sphere) equator or the center is where the recommended flow rate should be set at but since you're using a shielding gas that for the most part, has a lighter density then, the ball rest on top of the recommended flow rate should used if your flowmeter only has settings for Argon and Carbon Dioxide. If yours does have a gauge for Helium then set it to that scale with the ball equator at the recommende setting... The chart I have also lists recommended travel speeds for both 16 and 20ga. sheet metal.. they are 32 ipm's (inches per minute) for 16ga. and 37 ipm's for 20ga. so this means you have to travel faster when you weld on the 20 ga. material...
On my Millermatic Calculator, for 16 ga. stainless stl., It recommends for short ciruit transfer which I presume you're using, the volts should be set at 19-20, amps or current at 70-80, wire feed speed at 180-205 if you're using 0.035 dia. wire with the same gas mix you're using... It does'nt have any recommended settings for 20 ga. but, it does have settings for 18 ga. stainless stl. so, if you like, you can adjust your settings to slightly lower than the low end of these settings!
They are: 19-20 volts (I would recommend 17-18 on this), 50-60 amps or current, 120-150 ipm's for your wire feed speed (I would recommend to start slightly lower at 110 ipm's then work your way up until you get the desired sound and feel) you'll know what's the correct welding schedule when you experiment on scrap first so, "tweak" around abit with your machine before you start welding on the actual work FIRST!!! Do'nt forget to visit Ed Craig's site first before you make your experiments so that you have the opportunity to see what you find there!!!
Good Luck and let us know your results!!!

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By Motohead1 (*)

Date 11-03-2003 19:51

Wow excelent web link thanks thats the kind of info i was looking for. :) Hmm i have .030 and .024 wire and i now have a tank of strait argon. I talked to a a few experts down at the fab shop i get all my bends from. he looked at the welds and told me that with the 20gage pipe i should use strait argon and to also purge the inside of the pipe with argon too at only about 2 psi. He said the helium was to hot to use for a novice and that argon should be all i need and is actually what he uses. I ufortunetly dont have a flow meter on my regulator. just a PSI gauge. i can chage the PSI rate but i am not sure to what it corolates too. While i was at the shop they let me borrow the tig machine for a few minutes to weld my mild steal flages to the stainless. O man do i want a tig BAD. :) but its definetly not in the budget as of now. I am saving up though. :) I got a few more peices and i am gonna atemp it again after waer out a few of these scrap peices and find a way to purge the inside of the pipe with argon. I plan on just "T"ing off the outlet of an extra tank i have set at 2 psi. Anyway i will let ya know how it goes thanks guys. :)

Jay

By Motohead1 (*)

Date 11-04-2003 05:06

Wow you guys have been a great help i have learned alot in the past week. :) today i welded up a few new intercooler pipes in stainless and tried the purge method and used argon. It turned out great! :) porisity is not a factor now. :) I now know that i should just use argon from now on and stay away from the He/Ar/Co2 mix. its a waste and it burns too hot. Thanks again guys i am a happy man. :)

Jay

By kam

Date 11-05-2003 17:06

Are you sure about that gas mixture being 90% He? There are alot of mixtures out there. I sometimes use a 90% Argon 7.5% He & 2.5% CO2 which works great for stainless. I prefer a 95% Argon with 5% CO2. 100 % argon is generally not used with MIG due to unstability of the arc. I also us 98% Argon with 2% Oxy with great success.

Good Luck

kam

By ssbn727 (*****)

Date 11-05-2003 18:16

Hi Motohead1, Kam!
I would have to agree with Kam on his suggestion to at least try out the gas mix Kam was referring to...
Offhand, I do'nt remember the price difference so, you might want to check about that also to see if that could also become a determining factor... Although, arc stability should be of some importance when welding the intercooler tubes... I personally do'nt like to use even a little carbon dioxide with stainless if you get my meaning...
I would say the 2% oxygen in the mix should'nt hurt and only help in stabilizing the arc without the risk of introducing any extra carbon in the weld no matter how small the amount may be...
I do'nt know, maybe I'm overreacting with the carbon dioxide???
Anywho, I wonder what Ed Craig's website has to say about it???

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By Motohead1 (*)

Date 11-06-2003 06:18

yea i am sure about the 90% He. thats what the chart said. but as you can see in my above post i ended up using a Argon and 2% Oxygen mix. This is what was recomended on Ed Craigs site. ;) he goes on to say how much a waist it is to use the He tri mixes for stainless. with the argon i am now making very nice solid welds. :)

By sparx

Date 11-06-2003 13:52

The 90%he/7.5%ar/2.5%CO2 is a blend designed for short arc welding of austenitic stainless steel. (300 series) the trade names for a couple of gas companies is Helistar A-1025 for Praxair, Stainshield Light for BOC, Blueshield 9 for Air Liquide, HB Trimix for Airgas, along with a few others. You had mentioned a 90%AR mix with 7.5%he and 2.5% CO2. I am not familiar with this blend. I really don't see what the advantage of a small amount of helium would be in a particular mix, but I could be wrong. As mentioned earlier, and in spite of what Ed Craig might say, there are places in this world for three and four part mixes. Arc stability, penetration profile, impact properties, weldability, etc.. can all be improved or changed with the mix of shielding gas that is used. He mentions that the "sales" people use a lot of smoke and mirrors to sell three part mixes or four part mixes to unassuming gas customers. I think for the most part, some of this might be true, but I also realize some of the advantages of using a blend that will improve arc starts, or the penetration profile to help increase productivity, reduce re-work due to joint failure, clean up due to spatter, etc...etc....etc...........
just my 2cents worth.
have fun

By ssbn727 (*****)

Date 11-06-2003 15:38

Hi Sparx!
I hear what you're saying and yet, what it generally comes down to is the application!!! Motohead1's application does'nt require that much scrutiny unless he's working to a code or standard where product liability issues may become a concern... Something to think about Motohead1!!!
I asked these types of questions to representatives from Harley Davidson (welding engineers) when they did a presentation on how they weld their motorcycle frames made of a different material than what Motohead1 is using but, nonetheless they said that they did'nt incorporate any specific welding codes or standards into the design of their frames and their welding procedures did'nt have to follow any governing code or standard for their application because there were'nt any existing at that time!!!
I found that hard to believe myself but, since they were our guests at the AWS Pittsburgh section meeting in April, I decided not to push the issue any further at that time...

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By Motohead1 (*)

Date 11-18-2003 04:31

Ok guys i am still having trouble welding 20 gauge pipe to steel flanges. I dont understand the welds are fine i just have tiny holes everywere? this is not good for intercooler piping witch is all i am using this Mig machin for. I didnt think it would be so dificult? I use to use a tig back in school to make piping and had no problems and maby had to spot one or 2 tiny pin holes. now i have 50 little pin holes. :( Do i need to just save up for a tig? I hate to shell out all that money if theres any way to do this with a mig. I dont get it. why can i tig weld this stuff but Mig is just not happening? Anyone that does intercooler piping any sugestions?

Jay

By jwright650 (*****)

Date 11-18-2003 11:07

Have you checked your gas flow? Too much - too little will cause porosity. Dirty joint?
John Wright

By kam

Date 11-18-2003 12:51

Tiny little holes generally means that you have a gas coverage problem. Usually the porosity you get from oily or dirty parts gives much bigger sized holes. I weld ss to low carbon parts everyday with mig and have few problems.

Just a few things for you to check:
1) Pull off your nozzel and make sure spatter is not causing you to lose your gas flow.
2) Make sure your nozzel is seated properly on your gun so that it is not sucking air in from behind
3) Could be you are welding to fast and out running your gas
4) Look around and make sure you dont have a fan or something blowing your gas away
5) Try a different type of nozzle with a smaller diameter orfice
6) bump up you gase flow rate to about 35
7) try changing your torch angle
8) replace diffuser
9) reduce tip to work distance

Hope this helps, let us know what you find out. Might want to post your parameters so we can take a look.

Regards

kam

By Motohead1 (*)

Date 11-18-2003 13:45

Hmm i will try buming up the gas a little its at 20 right now. I have no problems at all welding pipe together. its the flanges that are giving me hell. settings are:

millar 135
.024 solid
setting 3 on voltage
setting 30 or a little less on wire speed
argon at 20
welding mild steal 20 gauge pipe to steal flanges.

By Niekie3 (***)

Date 11-18-2003 19:37

Hi Motohead1

I am a "metric boy", so off-hand I am not sure what thickness material you are talking of here. (20 gauge?) At any rate, it sounds rather thin. Probably below 1mm?

Often these types of materials in the auto trade are not austenitic stainless steels, but ferritic. Just make sure that you have the right wire to weld this, if this is the case. (Is it magnetic? If it is, it is probably ferritc.)

Also, for stainless this thin, backing gas is absolutely critical. If you do not get proper coverage on the back of the joint, you will have all kinds of problems. As I can not picture your weld configuration, I can not give advice on how to ensure proper backing gas coverage, but just remember that Ar is heavier than air, so build your "dam" in such a way that you are not welding at a point higher than where the Ar can leak out on its way to the floor. Also, high flow rates can lead to "mixing" of the gas which means that you are not eliminating the oxygen, merely re-cycling it.

Hope this helps.

Regards
Niekie Jooste
Fabristruct Solutions

By Motohead1 (*)

Date 11-19-2003 03:46

Yea sounds about right. I am making a little purge setup to bleed 2psi of argon inside the pipe. thing is i am having no trouble at all welding two pipe together. its only at the flanges were the problems are at and a purge line inside wont do to much good since i will be welding a 1/4 inch away from the end of the pipe. kinda hard to plug that end and still have room to weld. anyway i wont find out for a week or so causei am waiting on more flanges. till then i will cut the old ones off and practice and try to find out what the hell i am doing wrong. :) O and BTW i am back to mild steel pipe. that 304 stainless gets expencive to make mistakes with.

Jay