Laser cutting - heat affected zone

[geoffthehammer]

We currently have som parts made from 304 stainless steel. These aparts are approximately 3mm thick. Our supplier has asked if he can supply them as laser cut (as opposed to having machined edges). I am concerened that the heat affected zone will show as a brown discolouration band around the edge. In previous trials of similar laser-cut components, the discolouration always returns after polishing.

Is there a way of permanently preventing the discolouration?

 

[TVP]

What type of polishing? Did you have the parts fully passivated according to ASTM A 967?

 

[geoffthehammer]

Polishing - just a gentle polish e.g. chrome polish, nothing too abrasive.

I thought that the HAZ is a microstructural change in the metal, would passivation undo this change? Excuse my ignorance in this area.

 

[unclesyd]

What you probably have is heat tint + a little iron dust from the laser cutting process. Depending on the equipment used from cutting this can often be a very tenacious scale.

A quick thing to try is go by a motorcycle shop and get a container of "Blue Away" or small package of Semichrome and try these two. Blue away is the more agressive product.
If either of these material don't get the job done you may have to pickle and passivate the part to clear this up.

 

[TVP]

There is definitely a microstructural change in the HAZ, but the discoloration part of this can be influenced by electropolishing and/or passivating.

 

[SMF1964]

Could the laser cut surface be sensitized? This might explain why the discoloration returns after polishing, especially if the heat affected zone from the laser cut is deeper than the polish removal depths.

 

[tomwalz]

There is definite change after laser cutting. We see this in saw brazing. You can’t braze successfully, reliably to laser cut saw plate unless you grind away the heat affected area.

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessor.com

 

[MikeHalloran]

You can't get a reliably good weld on a lasercut edge, either. A kiss with an 80 grit wheel takes care of it, so the HAZ must be very localized, but it's there.



Mike Halloran
Pembroke Pines, FL, USA

 

[GRoberts]

Another option besides machining that would not discolor or have a HAZ would be water jet cutting.

 

[EdStainless]

I would look into pickling some parts and seeing if that takes care of it.
The sensitizatio itself will not change the look of the material. I lean toward the heat tint as the cause.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

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