Welding Titanium

[vanci]

I will be autogenously welding .125" thick CP grade 2 titanium using the GTAW process. The surrounding atmosphere will be purged with 100% argon and cooled to below 800 degrees F before entering the outside atmosphere. The weldment will be post weld heat treated.

My question is: "is it possible to cool the weld too quickly?" Will the weld crack, etc if it is rapidly cooled?

Thanks in advance!

 

[metengr]

vanci;
Your post read fine until I saw that you mentioned PWHT. Cooling to below 800 deg F in a protective atmosphere after welding is highly recommended before introducing the welded component to atmosphere to avoid oxygen contamination. PWHT is not required nor recommended. Here is an excellent resource on welding titanium;

http://www.timet.com/Index2_content.html

 

[UconnMaterials]

vanci,

A PWHT is fine as long as it's done in a argon atmosphere. The problem is that oxygen and nitrogen are alpha-phase stabilizers. If the PWHT isn't done under an argon atmosphere you risk alpha-case formation.

It certainly is possible to cool a weld too quickly. Solidification cracking is always a possibility, but there is less of a chance in unalloyed materials because the only other elements are tramp impurities. The lower the alloy content, the narrower the freezing range, and thus the weld can be cooled at higher cooling rates without cracking.

 

[metengr]

UconnMaterials;
I would have to respectfully disagree with your statement regarding PWHT. In this case, PWHT is really not required for Ti alloys, and would serve no purpose. Typically, welding Ti under inert atmosphere is similar to welding austentic stainless steels and cooling rapidly after welding is not an issue. The issue is exposure of the weld region to atmosphere above 800 deg F.

 

[TVP]

What is the purpose of PWHT of CP/Grade 2 titanium? As metengr noted, Timet does not recommend this as a matter of course.

 

[moltenmetal]

At this thickness it would appear PWHT would merely add cost and risk of O2/N2 contamination of the part. Sometimes the "do nothing" option actually is both cheaper AND better.

 

[metengr]

I would suggest a literature search as indicated below may yield adverse effects of PWHT on Ti alloys;

http://www.google.com/search?hl=en&q=post+weld+heat+treatment+of+Ti&btnG=Google+Search

 

[UconnMaterials]

I would think if residual stresses are a concern a PWHT for stress relief would be appropriate.