First wack at 301 HH

[poolie_p]

Ok ,but stilll need some practice. I never weld ss, kinda fun though.

[Rocky D]

Looks good to me.

[ace4059]

bead looks good, but what was the color before you brushed it off. Black?, Gold?, Rainbow?

My welding Instructor never would accept a brushed SS weld due to not being able to see the color.

Rocky I have a question for ya. When you burn SS while welding it (turn it black) and wire brush it, does it take the impurities off. Becuase My welding Ins said that SS looses it stain-less ability when you burn it black (makes it where it may rust), but when you brush it, does it give its stain-less abilities back to it, since you took off that top coat of metal? Hope that wording makes sence.

Later
Ryan

[Rocky D]

...
My welding Instructor never would accept a brushed SS weld due to not being able to see the color.

Rocky I have a question for ya. When you burn SS while welding it (turn it black) and wire brush it, does it take the impurities off. Because My welding Ins said that SS looses it stain-less ability when you burn it black (makes it where it may rust), but when you brush it, does it give its stain-less abilities back to it, since you took off that top coat of metal? Hope that wording makes sense.

Later
Ryan
That's a great question, Ryan...no one ever asked me that before...there is a metallurgical answer that would be over both our heads.

First we need to be more specific as to burning it...welding without gas will certainly turn it black...in that case the weld would be no good...now to weld with torch gas and no backup produces "sugar" on the backside and that would need to be ground out.

To weld real fast with gas backup produces a dark brown weld, and I did that all the time on aircraft half-stampings, which were wire brushed and were in spec for that job. Now just a note on wire brushing stainless...you must use a stainless wire brush that has never been used on steel. Also you must not wire brush the metal to make it smear...that was a no-no for us, too. Never did understand why.

[poolie_p]

it looked like a rainbow! I have no idea about the brushing part though. I know if you get it to hot it will rust on the weld, then again everything rusts here in Florida it seams?

[ace4059]

Yes SS will still rust. It is just is supost to rust less than mild steel. Hince where the name comes from. Stainless steel. Thats why they dont call it Stainproof steel.;)

Rocky, Since when you "burn" SS and it looses is stain-less ability, Would you then call it stain-more. :rolleyes:

-Ryan

[ace4059]

First we need to be more specific as to burning it...welding without gas will certainly turn it black...in that case the weld would be no good...now to weld with torch gas and no backup produces "sugar" on the backside and that would need to be ground out.

Now just a note on wire brushing stainless...you must use a stainless wire brush that has never been used on steel. Also you must not wire brush the metal to make it smear...that was a no-no for us, too. Never did understand why.

I am not talking about the sugar coat, nor lack or gas coverage (which both are not good). I am talking about running VERY hot and the metal burns black.

The SS wire brush is so you dont imbead impurities into the metal. When you smear it contaminets (sp?) can also be trapped in the metal causing it to rust. It is kinda like why you dont sand blast AL before you weld it.

[B_C]

Just enough heat to create a puddle then run with it.....LOLhttp://img.photobucket.com/albums/v93/billcalicura/DSC00003-29.jpg

[urch55]

You done a great job Poolie_p :) . I will be happier than pig in crap if my welds looked that good..:D

Take Care...... Bob

[flamin]

ace4059

Wirebrushing a SS weld that has Carbide precipitation, or (sensitizing) will not return the base metal to its original state. The damage has occurred in the grain structure of the of the base metal, and the blackness you see is a result of the carbon drawing to the surface, and the result is loss of corrosion resistance. Now whether there is a process to reverse the effects, I don't know. In an ideal situation, achieving a straw colored weld would be optimal, once you start seeing blue and purple, carbide precipitation is on the verge of taking place. Keeping the metal cool is key. Lower amperage, smaller beads, using heat syncs can help.

[hotrodder]

Carbide precipitation is a very different beast to the the 'colouring' that occurs when welding/heating stainless. The colours (straws, blues, purples even grey) are just the result of the surface being exposed to air at elevated temps i.e. oxidation. Sugaring or coking is just oxidation taken to the extreme. They do effect corrosion resistance as (for maximum corrosion resistance) a chromium rich surface is required- a thin layer of chromium oxide layer is what 'protects' the material.

Pickling and passivation of stainless PDF (http://www.euro-inox.org/pdf/map/Passivating_Pickling_EN.pdf)

Carbide precipitation (http://www.azom.com/details.asp?ArticleID=1177#_Intergranular_Corrosio n) requires a source of carbon to react with the chromium and reduce corrosion resistance. For the common alloys (304, 316) the 'L' grades have even less carbon (down from around 0.08% to < 0.03% C) to reduce/eliminate the issue. Another way is to 'stabilise' the alloy with elements that have a higher affinity for C than chromium does, Ti is a popular choice (321 for example)

Under normal welding conditions the heat tint is a 'tell tale' of how hot the weld was, may or may not indicate that carbide precipitation could be an issue. Change the quality of the gas shielding and the heat tint will change even if the welds heat input stays the same. Use a trailing cup or put the weldment in a welding chamber and you could have a weld with no heat tint at all- if it was a high carbon flavour (say 304H) though and it was welded hot and slow carbide precipitation could still occur

[Rocky D]

Excellent post HR, you make it real clear.