dry ice

By - Date 08-05-2005 15:37

I have no environmental documentation to back this up, but GMAW will expose you to more welding fumes, if thats what you're talking about. As you probably know, there is litigation going on right now concerning manganese and chromium residing in the welding fumes. I assume the dry ice is used to counteract the distortion, as you stated. What is going to happen is the weld and HAZ is going to cool down very rapidly. If you're asking if this is going to cause any metallurgical disadvantages, the answer is probably "no". I said "probably" not. If you do have any problems, it will most likely be a rapid solidification of the weld bead that can possibly lead to a center-line crack due to the inability of the molten weld pool to completely solidify before cooling.

Chuck

By thedoctor (*)

Date 08-08-2005 22:17

If you are concerned with chromium drifting about the welding arena, you do not want to TIG or TGAW the joint. The CO2 ice packed around the weld will only reduce the weld's corrosion-resistant properties. MIG or GMAW produces the least floating chromium but has a tendancy to make you over-weld in order to make the desired product.

By - Date 08-08-2005 22:43

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By Jim Hughes (***)

Date 08-08-2005 23:14

I totally agree with you Chuck!! What??????????????????????

Jim

By - Date 08-09-2005 00:25

Jim,
I have no idea what he is talking about. I must have slept through too many metallurgy classes in school.

Chuck

By Lawrence (*****)

Date 08-09-2005 00:34

No way doc

The welding arc and pool in GTAW has less disturbance and smoke by a factor than GMAW. Pulsed GMAW trials prove reduced smoke levels over traditional spray transfer. But no way does GTAW produce more airborne anything than GMAW.

Wait. GTAW does produce more ozone per amp due to the lack of smoke!

By - Date 08-09-2005 01:20

Lawrence,
I agree completely about GMAW producing more smoke. That is exactly what the litigation is all about. I don't have a clue about all this other stuff he is talking about. I totally disagree about the scenario about chill bars reducing the corossion resistance of stainless steel. That MIGHT be true in a duplex SS where it is prevalent to maintain a ferrite/austenitic 2 phase balance, but not in the normal austenitic SS grades.

By Lawrence (*****)

Date 08-09-2005 03:06

A water cooled copper block would be way more efficient than CO2 for a number of reasons.

Top reason is:
Copper can be worked/machined to make a 100% snug fit (full contact) where CO2 is going to sublime at critical areas causing inconstincies.

The metellurgy is over my head, but distortion control with block CO2 will be inconsistant.

By sparx

Date 08-09-2005 15:40

Has anybody thought about the effect of the carbon dioxide affecting the weld? As far as I know, 100% CO2 isn't the best shielding or purging gas for stainless steel welding, and if the dry ice is placed on the back side of the weldment, wouldn't that equate to having a CO2 'purge' area on the back side of the weld?
just a thought

By - Date 08-09-2005 19:29

Sparx,
You are absolutely correct about straight (100%) CO2 not being recommended for a purge of SS. Very good point. I have seen dry ice used as a chill block, but it was not immediately on the open butt area, it was placed about 2-3 inches from the root opening (on each side) but was enclosed in an airtight bag.

CM