Dear Sirs,
We are welding SS304(5mm) to MS(8mm) sheets since last one month, using ER70S6 MIG wire with 80-20 Ar-CO2 gas mixture. Welding quality appearance is OK. But theory says ER309 is required as a filler metal for SS to MS welding. Ours is a sturctural application and not a pressure part. Hope I am not moving on the wrong path.
Can anyone throw more focus in depth please???
There is a ton of material on this dissimilar in the forum. Try a search. Bottom line, do not use 70S-anything for a MS to SS weld.
Because you are welding relatively thin plates, you might not have had any prolems yet because residual stresses are lower. However, due to the potential brittle microstructure that is formed it the weld, the welds have the potential to fail during loading in service. You have a problem on your hands.
Hello JAYDESAI, I am neither a metallurgist or an engineer so I cannot remember the specifics of this. Yet, I do recall earlier discussions on the topic that considered puddle dilution between SS and MS, the 309 had a higher percentage of a certain component that would minimize the dilution of the weld pool and the requirements of the SS side of the weld joint, at the same time it would not adversely affect the MS side. If the process was reversed and done with a MS filler the filler didn't possess any of this particular component and thus it could lead to issues with the weld deposit and the adjacent zone of fusion on the SS side of the weld metal. I hope I have explained this understandably and somewhat correctly. Hopefully some of the other more well versed metallurgist or engineer types can add to this. Best regards, aevald
Generally you would like to see a minimum of 18% chrome and 8% nickel in the diluted weld deposit. By using ER70S-X as the filler metal, assuming the weld deposit is 70% filler metal, 15% SS and 15% mild steel, the diluted weld would be deficient in both chrome and nickel.
AWS D1.6 has the WRC diagram as modified by Kotecki and Lippold. The new diagram allows you to plot the chrome equivalent for both the mild steel and the stainess steel as well as the filler metal. Using tie lines, you can find a graphical solution to the approximate amount of ferrite in the weld and the microstructure of the HAZ and mode of solidification, that is whether the weld solidifies as austenite and transforms to ferrite, ferrite to austenite, etc. You would like to see some ferrite in the weld to prevent fissuring due to low melting point consituents. Typically to shoot for ferrite number of 3 to 10.
Good luck.
Al
Hello again JAYDESAI, to go along with what 803056 has posted you might consider using the search function of the forum and typing in "Chuck Meadows" in the poster field, Chuck has since passed away and we all miss his insight greatly, but he was a wealth of information on SS and other such materials and if you get a chance to read many of his posts you will come away much better informed. Chuck was also employed by Avesta which is a large supplier of SS welding electrodes and other related items. Best regards, aevald
Dear All,
I tried welding SS to MS by MIG using 80-20 Ar-CO2 ratio and ER309 as filler. But the weld behavior is erratic, can't stabilize the arc. Weld appearance is also not acceptable. Is that a fault with the gas ratio selection? Any special care to be taken?
98 Ar 2 CO2 is the general reccomendation for SS and SS-MS but it should be weldable with 80-20.
With 80-20 you will have a very hard time establishing spray arc transfer. Erratic weld behavior is most likely due to machine settings in the unstable globular transfer mode. My suggestion would be 98-2. What is your wire size?
A common gas mix I see with stainless using GMAW is 7.5% argon, 2.5% CO2, remainder helium.
You haven't told us what the other parameters are. There's a lot of reasons you could be having problems.
Best regards - Al
wire size- 1.2mm
current 60-80 amps
voltage- 24v
Pulsed transfer mode
It looks like your heat input is on the LOW side.
Best regard - Al
hello sir
i read your full history of job normally SS to MS nobody use ER-70S-6.
in your welding parameters i think your current is little bit low as per the voltage range you given
with warm regards
raghubir singh
What are your pulse parameters? Also, what make & model welding power source/system are you using?
Respectfully,
Henry
Dear Henry,
Parameters i have written in last post. Make of welding machine- Froneus 270.
Regards.
I respectfully disagree because, you only listed the current (Amperes) and voltage settings on the last post as opposed to the "Pulse" parameters such as your peak and background settings. ;)
However, you're in luck because one of my favorite friends in this forum - Stephan as well as one or two other folks in here are very intimately familiar with the "Fronius" brand of welding equipment, and they will probably chime in soon enough. :) :) :)
Respectfully,
Henry
In my experiences the trimix gas that was mentioned wets out the er309L better then the 98/2. 98/2 works well with er308L and can be used for the ER309L with decent results in the short arc or spray transfer. 98/2 will spray the 309L as good as any other, I was refering to short arc characteristics as being a bit sketchy with the 309L.
Hi Jay,
Mixing 70s-6 with stainless on one side and MS on the other can lead to a weldment that will form martensite depending on cooling rate. Check hardness of welds with a hardness trace and make sure it is within your spec. Using 309L should avoid that problem.
Current of 60-70 amps is very low for a 70s-6 1.2 mm wire. Should be of the order of 250 amps or more.
Try using a 98/2 Argon-Oxygen mix for arc stability.
Hope that helps.
Girish
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