New to forum, question w/o war, weld ss to steel

When I first heard of this site I thought it be great. But it's a shame how some of these people reply to questions. You can only learn If you ask. We all have to start somewhere, we're not born with college degrees.

Anyway, I don't want to start anything, but what is the best rod for welding stainless to steel? I've always heard people say 309 is best for dissimalar. I've got a 1 3/8" round bar that I want to add 5" of stainless on the end of it. I'd like to use stainless because it will be female threaded and in harsh conditions and I don't want the threads to rust. Thanks, Farmall MD nut

You didn't give use alot to go on as to the type of SS and the weld process your using. That being then I would use E307 as it adds a touch of Mo to cover a wider range of compatibility, mostly to stop weld cracking.

7018 would be a poor choice as your need to add Cr & Ni back into the weld that is lost during the welding process.

I would also suggest you butter weld the mild steel face then fit the joint together then weld with E307 or E309.

T_Bone

You mentioned "a touch of Mo". Are you refering to Molybdenem?(I"m not sure i spelled it right) If I remember right the chromium and nickle are in most of the stainless rods correct? You said butter weld. Is that welding a hot stalled puddle on the end of the steel?

Mo= molybdenum

To butter base metal means to add a independnt layer of filler rod before the main weld is completed. Look at this preweld as a transistion to the base metal to the adjoining piece to be added. This will stop alot of weld cracking and/or weld tear out under severe use.

So in your joint we would butter the mild steel rod face with E307/E309 as then when the final weldment is made you would be joining two grades of SS and not one mild steel and one SS. You might consider using SMAW using E307/E309.

Butter welding also is common on dirt buckets before hardface rod is put on. This would keep base metal shock lower while using the bucket in rocky soil.

E308 will probably fail at some point well before maximum design stress as it doesn't have the additional Cr & Ni that's needed. You should also use Ar-95/O2-5 or Ar-97/o2-3 for a shielding gas for your joint design. With o2 added too the Ar would achive deep penetration. You should also consider using a post pruge cup on the bottom of the weld zone to keep porosity out of the weldment.

The addition of HE would not react well with the mild steel. The HE would cause the carbon to pool in the weld puddle and make it brittle.

T_Bone

Boy I must be in some kinda mood tonight;)

I'm not criticizing because I assume that it's me who's missing something here, but except for your last line I didn't understand any of that. I let a whole day go by in the hope that it would suddenly become clear to me, but I don't think it's going to. What do those names mean, and what new folks have been belittled? EBay? Some like it and some hate it, about like anything. (I like it, but so what?)

All the best, Stan

Good point about the word wars; I'm not proud to say I'm one of the worst, if not THE worst, in that regard. Despite that, this is a pretty friendly site. We sometimes argue about each other's information, but rarely or never criticize or belittle anyone for their lack of experience.

What I've heard and found to be true about joining stainless to mild steel is that it doesn't matter whether you use SS rod or mild steel rod. At some point the two varieties of steel have to mix because that's what welding is. SS filler carries the fusion slightly further into the mild steel, and vice versa.

On a related topic, are you aware that if you use the same grinding wheel or disk, or the same wire wheel or brush on both mild steel and stainless steel, the stainless will lose much of its corrosion resistance? You need to have a new grinding wheel or disk which is used only for stainless, and your wire wheel or brush not only has to never be used on mild steel, but has to to be stainless itself.

All the best, Stan

I was still in the process of writing my previous post when Dave, 135 Fan, posted his. Of the two of us, my recommendation would be to go with what Dave says; besides having a keen, analytical mind he has a wealth of real world experience (as do T_Bone, and DNWELDERMAN), while my hands-on welding experience is far less. I know from experience that what I told you will work, but Dave probably can tell you why the way he says to do something has a benefit that isn't obvious to someone who hasn't seen it in a variety of applications.

I generally use mild steel electrodes to join SS to mild steel, but I've never had to do so in an application where there were dynamic stresses involved. It could be that in that situation different factors would have to be considered. If it were my project I'd probably weld one up with 7018 and then torture test it beyond the limits you would expect it to encounter in use. If it held up, and the application wasn't one in which failure would be catastrophic, I'd go with it. If it was a structural component on something like a vehicle that was going to be used to transport nuns and puppies and orphans, I'd try to get some better advice.

When I weld rod together lengthwise I like to taper both ends, at least one end to a fine point, preheat a little, and be fastidious about not entrapping any slag. That generally takes care of it.

All the best, Stan

Plain steel bolts (with a little carbon in them) are worked soft (annealed) and then heat treated to harden them. Thus they are harder and have higher strength than stainless. Different levels of carbon and different heat treatment profiles give you the different grades.

Cliff (VA)