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stainless steel

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is there a certain way to forge stainless steel? certain tools, forge, fuels whatever. or is it the same as other steel. i have a coal forge. do i need to get a gas forge to do it? let me know thanks.

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One can forge some grades SS in a coal forge. The main thing to remember is that nickel loves to suck up sulfur, also some grades of stainless are not able to be forged well by any method.

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You may need to do the proper heat treat and passivisation to get it to it's max stainlessness though.

I just did a set of hooks for a hunter friend to butcher large game, Elk, out of stainless; takes more work to hammer, more abrasives to clean and then I'll passivate with citric acid as I told him he could pop them in the dishwasher when he's done.

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I have forge quite a bit of SS for ornamental items. All of it was the low or no carbon SS. Your log in name makes me wonder if you are talking about forging high carbon SS for blades. If that is the case it is different. I have never done that, and that is for a reason. A study I read long ago found that almost all knife grade SS will have cracks through out the piece after forging even if the forging heat is kept correct. I do not remember the source of that study. They did say that 440C SS did not do this if done at the correct forging temp.. You can find lots of info by googling the individual SS you wish to learn about. Like 440c. Most always that information will give the forging temps. How you determine those temps in the shop is a whole 'nother story. As is passivation of SS after forging.

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440 is in my experience the most forgeable grade backshop, though the stuff is really tough to work with. It feels alot like 5160 under the hammer. However, I find for jewelry, that plain old mild steel tends to be just fine for most folks, as the oils in your skin and the constant movement of the body and clothing tend to keep it rust free. The only time I really even use stainless is if I am making cutlery for re-enactors, as it tends to be relatively dishwasher safe with no need for a finish other than the wire wheel...

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All automotive exhaust valves are forged from a stainless steel alloy. ( Can't remember which one. )

Intake valves are not always made from stainless steel, ... and all automotive valves are likely to have a .100" thick "wafer" of 4140 welded on the stem end, as a wear surface, ... and some also have a layer of "Stellite".hard surface weld, applied to the seat area.

Still, as long as you're aware of these "inclusions", scrapped engine valves are a good source of high quality, malleable material.


.

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I have forged some ss before. I assume it was something along the lines of 304 (a freebie from one of my stainless suppliers). I was making a steak turner out of 1/2" round, heating it in a coal forge. I guess I wasn't paying close enough attention and the stainless didn't give off the 'sparklers' like mild steel does as it approaches burning heat, and it melted quickly. Next time I will be watching closer...

As well, I think the stainless I was using has a tighter heat range. I was putting a twist into it and it developed cracks at a temperature that mild wouldn't have cracked.

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I have lots of experience with 316SS and both 410 and 416SS. The #16 in the 316L grade is nice to arc weld, forges well, but at a lemon yellow heat and takes at least 50% more effort. The surface needs clean up and passivisation to remain stainless. Most folks forge too cold on the 300 series. Remember that these are in the 18% chrome and 8% nickel range and are therefore hot hard and hot strong. The 410 forges nicely and is just a little easier to move. It is a 13% chrome and about 3% nickel. It too needs the surface cleaned post forge but can be heat treated to about Rc38-42.
Both will polish nicely. The 410 is stainless until elevated temps, well above any natural environment.

A caution on exhaust valves. Big engine valves, and most aircraft piston engine exhaust valve are hollow in the stem and are sodium filled to improve stem cooling. NOT a good choice in the forge.

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sweet guys thanks for the info. biggest take away came from ptree here, though others contributed to my blade making think engine here as well. 

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