Stainless San Mai questions

[fleur de lis]

So I've been laid up with an nasty infection for the last few weeks & have had some time for planning some projects. Bores out of my blasted mind. 

I'm been trying to make a hunter / skinner in stainless steel san mai ( stainless / carbon / stainless ). Every time I've attempted this, I've been unable to get the welds to take. Delamination city. 

I've got access to literally as much stainless as I want. But it's all 304/304L, 316/316L, with smaller amounts of duplex 2205, monell 400, & hastalloy (can probably guess what I do for a day job)

I've only  tried with the 316ss with 1095 or 1084 for the core. I know the 400 series stainless should work better. But until I can get some cash inflow again (blasted infection), I'm stuck with the 300 series stainless. 

 

Can someone please explain how to forge weld san mai with the materials available to me. Should I be trying to forge weld this like regular simple carbon steel? Maybe weld the whole parameter electrically first. In a can? This is vexing me & I'm hoping the doctor will sign off on me friday so I can get working again. 

 

Thanks for any advice y'all. 

[Steve Sells]

you said nothing about flux or fuel or prep

[Buzzkill]

15 minutes ago, fleur de lis said:

Should I be trying to forge weld this like regular simple carbon steel?

The short answer to this question is NO. 

I have not forge welded stainless steel, but I do know that what makes it stainless is the formation of Chromium oxide on the surface which (mostly) prevents oxidation of the iron underneath.  This invisible layer of chromium oxide forms rather quickly even in open air without additional heat.  In order to forge weld the material you will have to keep that layer from forming. 

The research I have done into what you are attempting to do suggests that you need a very aggressive flux (which may be toxic), a canister type weld with well prepared stock, or a forge  with an inert gas atmosphere (which would probably mean an electrical furnace/forge and require you to set the weld without removing the steel). Explosive welding would also work, but has its own set of dangers and requirements.  I believe some members on here have forge welded stainless to simple alloys and may be able to provide more information.

[fleur de lis]

18 minutes ago, Steve Sells said:

you said nothing about flux or fuel or prep

Gas forge. After that I'm open minded

[Steve Sells]

open minded has nothing to do with it, what did you try to do to get it to weld?  If you refuse to tell me how your trying to forge weld I cant help

[ThomasPowers]

OK let's try to cut the 20 questions short:

I used this alloy for the stainless outside:

I used this alloy for the high carbon inside:

I prepped it like this:

I am heating it in this type of forge:

I am using this type of flux:

I apply it:       ;     ;     ;     ;

I am heating it till the steel/flux  looks like:

I am applying the welding force with this:

I am applying the welding force like this:

Other Questions Steve et al?

BTW Hope you continue to do better; nothing worse to have time to think about stuff your health won't allow you to do!

 

[fleur de lis]

I believe that my open minded comment was read incorrectly. I'm open on what to do. 

As for what I have done. Always have used the gas forge for these attempts. Combination 316L with a 1095 core. Cleaned each side on the grinder to 120 then cleaned again with acetone. Stacked & tacked the corners with a mig welder. Borax for a flux. Attempted to weld the same as a regular stack of carbon steel. 

Next attempt was the same as before with the exception of  welding the whole parameter. 

Third attempt was prepared the same as above but not tack welded. I tried to use a can. Can was coated inside with titanium dioxide and thinned wood glue. This is the only try using the power hammer. 

Tried a few other times, but I can't remember  the details.

Thomas, I ended up with a case of cellulitis from a stray cat. I didnt know what that was, so like a idiot I didnt go to the doctor until it was almost to late to save my right arm. Was just shy of gangrenous they said. Whole lot of good times right there. All from a little cat scratch. But, getting better every day. 

[Steve Sells]

I have my own I published in  my book, but James Hrisoulas once posted this flux recipe:

5 parts Anhydrous Borax
2 parts powdered Boric Acid
1 part powdered iron oxide
1/2 part Flourspar
1/4 part Sal Ammoniac

This stuff sticks most anything together  but the flourspar can kill you  so read the MSDS

[ThomasPowers]

IIRC he called it "Steel Glue".

Strays can be killers; one of the Scandinavian countries just had their first Rabies death reported in 200 years from a stray dog that was handled on a trip to the Philippines IIRC. I picked another tick off last night; but that was most likely from my AR trip. I find I do not approve of seed ticks at my stage of life where I'm not flexible enough/good vision to see them.

[fleur de lis]

Thank you. I'll give that a try once I'm off this blasted medical. 

We've had lots of ticks in the area this year. I hate ticks. 

[Jclonts82]

I had success with a heavy walled 316 stainless pipe, 1" outer diameter, 0.74.." inner diameter, and a piece of W1 round stock at 0.75..

I took a 1/4 round mild steel rod, cut a slit on the end, then put a piece of 50 grit sand paper in the slit, chucked it in a drill and bored the inner diameter of the pipe until the W1 round would just barely fit with some 'gentle' persuasion. once the stainless sleeve was on, and flush on both ends, I mig welded it completely around both ends. effectively making a canister, with the 316 on the outside.

Heated it to welding temp. I judge it by color, to me its a bright yellow... use whatever you want, you could even slap some borax on the outside to make sure its bubbling vigorously just to use as a temp gauge, not needed for the weld, just a temp indicator.

Took it to the power hammer and away I went. hammer to shape, hammer in bevels, grind through the stainless and expose the W1 cutting edge.

I had to experiment with the quench. I had to use a slower, room temp canola oil. I cut some test pieces at 1/2: wide, 1.5" long , ground through the stainless to make a bevel exposing the W1. I tested in Water, Mcmaster carr quench oil, heated canola, and room temp canola oil. 

The room temp canola is the only one that didn't crack the W1... I think the stainless cooled and shrunk quite a bit, and it actually pulled the W1 apart, the welds held, but the w1 ended up with a crack in the middle of it, like it was pulled in 2... lol

[Buzzkill]

Thanks for sharing the info and pics.  I may have to try that with some O1.

I have a couple questions though for anyone who knows about these things.

Do other elements such as chromium migrate through the steel the way carbon does?

Does carbon migrate into stainless roughly the same way it does with non-stainless alloys?

Is there a good way to reasonably predict the ending carbon content of the edge material using this method.  Can we use the ratio of starting volumes of the alloys and their starting carbon content to get pretty close to the carbon content after forge welding and forging?

[ThomasPowers]

Other elements can migrate at high temperatures through a solid phase weld; HOWEVER some of them may require *years* to migrate as far as carbon does in minutes at the same temperature..

 

[Buzzkill]

The main reason for asking that question was to determine whether it was likely that the chromium content would be diluted enough to fall below the threshold for remaining corrosion resistant on the outer layers of the billet/blade.

[Steve Sells]

no, it wont

[ThomasPowers]

Will you be passivating the stainless?

[Buzzkill]

Right now I'm still in the information gathering/planning stages.  Passivation is one of the last things in the sequence to be concerned about, but probably a good idea to clean up any free iron on the surface  from hammer, anvil, etc.

[ThomasPowers]

Just checking; there's a reason it's "stainless" instead of "stain-never".

[fleur de lis]

Thank you Jclonts. 

I've got a 20' stick of 316 1" sch 40 sitting out back (with no idea where or why I got it). I'll  be  ordering some W1 promptly. Gonna blatantly copy your method. 

[Jclonts82]

Right on. Go ahead and try a few different inner cores if you have the time/resources, post results. I only had 2x12” sections of pipe. 

[Benona blacksmith]

Try mig welding the entire perimeter of the billet to stop chromium oxide from forming.

[Steve Sells]

you do realize that the full thickness of chrome oxide forms with in few minutes of grinding the surface. it doesnt take much air to do it

[basher]

I have gad good results grinding surfaces clean at 36 grit then applying wd40 and immediately welding around the billet (MIG). then soaking at welding head and heavy forging under press and power hammer , the important thing is to increase the weld surface area a lot at least double it. i forge strait to finished knife thickness as thick billets will tend to crack the core.

Ive also used argon and oil and weld is easier.

 

[Steve Sells]

good point about the oil coating Owen.

[fleur de lis]

Got far more W1 in today than I need for practicing this. Told the purchasing guy at the shop that I wanted a single piece of W1 round bar 1" x 3". So now I've got 9' of the stuff. Oh well, I'll make some other blades I suppose. 

 

I'll turn down a foot or three to fit my pipe in a few days & give it a go. With variations of both Jclonts & basher's methods described. Not like I dont have a lot more material to play with than anticipated. 

 

Thank you everyone  for the advice and  pointers.