passivation and indispensable with reworked stainless steel?

[dandao]

Hello everyone,
I have the following problem,
I have to perform stainless steel parts aisi 304 (x5crni 1810)
that must be welded among themselves without being cleaned up,
if in the indications of supply is not specified , the liabilities must be made? that is, passivation and a normal operation included in the processing of stainless steel or a further processing that can be left out and made only if expressly requested?

Hello and thank you

 

[maxopus]

mah, being stainless steel, we are talking about an inactive alloy (that is, it does not tend spontaneously to oxidize).
so the process of passivation should be superfluous.
Typically passivation is used on active metals such as copper or stainless steel alloys oxidable after the process of decapture that bare the metal and thus exponentially accelerates oxidative phenomena.

 

[dandao]

thanks x the answer,
the doubt and that requiring quotes to my suppliers, one tells me the processing of passivation absolutely indispensable after the decay of the piece, while another tells me that it is enough the decappaggio
not knowing these works I am puzzled about who is right and doing research on the internet the doubt remains

Hi.

 

[maxopus]

I express my perplexity on this.
the only shortness you have to use is that when weld you have to use intake materials suitable for inox.
There is one thing to highlight, often it is led to think that the inexpressible material is not so.
definitely resists better than traditional steels as the nickel chrome alloy is self-passive, but they are nevertheless metals and therefore sensitive to acidic and saline environments.
There are several stainless alloys depending on the use.
For example in a marine environment it is much better to use a 316l aisi instead of a 304.

 

[sampom]

thanks x the answer,
the doubt and that requiring quotes to my suppliers, one tells me the processing of passivation absolutely indispensable after the decay of the piece,

Well yes,
referred to the welding zones then can stand there. .

greetings
Mar

 

[dandao]

grazie a maxopus e a sampom x le risposte

ciao

 

[sampom]

grazie a maxopus e a sampom x le risposte

ciao

..but it still depends on what you want to do with it and customer requests.
in the pharmaceutical definitely require it, as in part of the food and fruit and vegetable/conservative (lactorium; treatment of tomatoes and derivatives. . ).
but in these cases you would not use "simple" 304 and welds would have well defined specifications.

greetings
Mar

 

[Fulvio Romano]

mah, being stainless steel, we are talking about an inactive alloy (that is, it does not tend spontaneously to oxidize).
so the process of passivation should be superfluous.
Typically passivation is used on active metals such as copper or stainless steel alloys oxidable after the process of decapture that bare the metal and thus exponentially accelerates oxidative phenomena.

I throw it there... if you don't passive, metal can stain. is oxidation, even if it does not enter deep because it is stainless. passivation could give a more homogeneous look to the material.

 

[sampom]

I throw it there... if you don't passive, metal can stain. is oxidation, even if it does not enter deep because it is stainless. passivation could give a more homogeneous look to the material.

Well, it's not just an aesthetic question.
It is not simply superficial spots, but a real "snow" to oxidation/corrosion from the welded joint (with the consequent chemical/physical reactions and release of harmful elements in the surrounding "microenvironment". besides clearly losing the characteristics of steel), especially in a 304, rich (relatively) of carbon.
the passivation serves precisely to bring back the surface of the material to the "intoxicable" state or rather, it autooxidates only outside creating a "impermeable" layer to the external agents and therefore "impassive" to the trigger of the above reactions.

all in very poor and not too correct words:biggrin:

greetings
Mar

 

[Fulvio Romano]

Well, it's not just an aesthetic question.
it is not simply superficial spots,[cut]

No, of course, I didn't mean welding. that must be passive, or at least molated.
the "machines" I said can give aesthetic problems, triggering fatigue and pollution in the food case. I agree with you on this.

 

[AlbertoC]

Hello everyone,
I have the following problem,
I have to perform stainless steel parts aisi 304 (x5crni 1810)
that must be welded among themselves without being cleaned up,
if in the indications of supply is not specified , the liabilities must be made? that is, passivation and a normal operation included in the processing of stainless steel or a further processing that can be left out and made only if expressly requested?

Hello and thank you

if they have to be welded and then not cleaned a good shortness is "merge" in argon the 2 pieces of 304 during the welding, I have verified that you get very clean welds almost free from flaws of oxidation trigger.
because while passive and thus guaranteeing an excellent protection from oxidation, the aid is still suffering from triggers (such as micropiles).
Hi.

 

[sampom]

or at least sick. .

and already, do you soon:biggrin:
and with what mola would you harass him? (nice word game:wink::biggrin

greetings
Marco:smile:

 

[body]

I know that by welding, chrome evaporates, so the cord will not be resistant to oxidation.In fact I noticed external railings with rusty welds.better passive even only on the cord.

 

[maxopus]

I always express my perplexity... depends on how weld.
How come the tops of the stainless steel kitchens that have the tanks welded on the edge, and that are always in contact with the water, never present signs of oxidation ?
According to me for certain railings use a fake stainless steel (what they call 430 ferritic ... makes laugh I know but, it is actually ferritic and therefore attacks the magnet) or a 304 that, has no good characteristics like 316 and it is better not to use it for outdoors.

 

[body]

It is true that in these periods of crisis they sell you poor material, but an external railing requires at least aisi 304. I am convinced that the sinks of the house are treated as by manual: degreasing, pickling, passivation.obviously it will be done in the tub, perhaps with a single immersion.