Stainless Steel for Structural Applications 3

[ralphi]

What is your say (or experience) about stainless steel 304 especially its welding techniques and sensitivity compared to iron steel and how strong is it in structural applications? Tips you could share? Thank you.

 

[thaidavid40]

You are asking such generalized questions that entire books have been devoted to such subjects. Suffice to say, anything said here would be so brief as to not adequately begin to answer your broad questions. Is there a more narrow, specific question in your mind? Or is this a fishing expedition for a school paper?

Thaidavid

 

[KootK]

AISC publishes an entire design guide on stainless that you might want to check out: Link.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[ralphi]

You are asking such generalized questions that entire books have been devoted to such subjects. Suffice to say, anything said here would be so brief as to not adequately begin to answer your broad questions. Is there a more narrow, specific question in your mind? Or is this a fishing expedition for a school paper?

There is this welder who only welds ordinary steel using arc welding... he tried to weld stainless steel.. i'm asking how much sensitive is stainless steel welding compared to steel..

Also why is there no wide flange made of stainless steel? Is the welding generally more brittle?

 

[KootK]

This extensive stainless steel design guide probably contains the information that you seek: Link. There are a number of issues that complicate stainless steel welding but most are resolveable with the right equipment and procedures.

Here's a source for stainless steel wide flange sections: Link

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[thaidavid40]

@ralphi -
Yes, there are stainless wide-flanged sections readily available (at least in the US).
When welding stainless, it is more sensitive to heat input than plain carbon steel. Too much heat (amperage) and the stainless will have tell-tale burn marks that will ruin any appearance effects that you might be aiming for in exposed stainless applications.
Dave

Thaidavid

 

[ralphi]

If there is a 200Ampere and 300Amepre Arc Welding Machine.. can you adjust (how often is it adjustable?) the 300Ampere so it can become 200Ampere or do you have to buy exclusively 200Ampere for Stainless steel welding especially only 0.06" (1.5mm) thickness?

 

[thaidavid40]

All of the electric welding machines that I have ever seen have current adjustment dials, so that the amperage can be adjusted within selected preset ranges. The welder should make trial welds with similar materials until an appropriate heat input setting is identified, then use those settings for the production welding.
Dave

Thaidavid

 

[EngineeringEric]

If you have a welder that doesn't know how to weld Stainless Steel than it shouldn't be considered structural. To be structural the welder needs to be certified and competent.

Welding something that thin also requires a skilled welder, there are lower strength welds that should be used for less heat generation which effect the capacity.... so lets just say the area you seem to be dealing with should not be considered structural (no substantial loads, no live load, no life impact upon failure)

 

[racookpe1978]

Your welder is not qualified to weld stainless, and your weld process control is dangerously bad IF YOU are considering asking "How do I adjust the weld machine so my welder does not burn the stainless he is trying to weld?"

There are explicit qualification controls and testing for welders and the weld process spec those welders are using. Those qualifications require proof (test pieces and certifications) for different metal (stainless steel and carbon specifically) and different weld geometries and thickness. In my judgement, neither the weld qualification nor the weld process control is adequate for a safe structure in this case.

 

[Bagman2524]

There is also a European Design Manual for Structural Steel. "Design Manual for the Structural Design of Stainless Steel".

Nearly all men can stand adversity, but if you want to test a man's character, give him power. Abraham Lincoln

 

[ralphi]

It take long time to polish newly welded stainless steel. Is this extensive polishing required only for appearance (to make it look pretty) or is it required to avoid corrossion and rust? I heard if carbon is left in stainless steel.. it can attract rust. Do the welds have carbon and is full polishing purpose to remove the carbon?

 

[thaidavid40]

To my understanding, ALL steels - stainless or alloy - have a carbon content, so I do not fully understand your question. The weld electrode material should be selected for the best match to the stainless grade(s) to be welded. Call your local welding supplier to get a good recommendation, if you are not experienced in this subject. So far as I know, removing burn marks is strictly for appearance, and not for corrosion protection.
Dave

Thaidavid

 

[ralphi]

To my understanding, ALL steels - stainless or alloy - have a carbon content, so I do not fully understand your question. The weld electrode material should be selected for the best match to the stainless grade(s) to be welded. Call your local welding supplier to get a good recommendation, if you are not experienced in this subject. So far as I know, removing burn marks is strictly for appearance, and not for corrosion protection.
Dave

I read the following excerpt below, It says "trace amounts carbon steel can become embedded in stainless steels, causing it to rust" and "Carbon steel dust suspended in the air can land on nearby stainless steel and lead to rusting." How true is this and what happens to the own carbon contents of the stainless steel?

http://www.thefabricator.com/article/metalsmaterials/the-wide-world-of-welding-stainless-steel

"Preparing to Weld
As in any type of welding, it is important to clean stainless steel before welding it. What you may not realize, however, is how important it is to use tools, such as hammers and brushes, only on stainless steel because of how sensitive the material is to the presence of any carbon steel. For example, if you use a stainless steel brush to clean carbon steel, don’t use it again on any stainless steel. The same is true of stainless hammers and clamps. Why? Because trace amounts of carbon steel can become embedded in stainless steels, causing it to rust.
Similarly, grinding carbon steel in proximity to stainless steel can result in problems. Carbon steel dust suspended in the air can land on nearby stainless steel and lead to rusting. This is why it’s a good idea to keep carbon steel and stainless steel work areas separate.
"