AWS D1.1 minimum preheat requirements for below freezing

By csd72 Date 01-23-2008 13:45

I have a client that needs to do a weld to an exposed external column half way up a building. The temperatures will be below freezing, probably in the low 20s.

Table 4.3 note 4 says that if the temperature of the steel is below 32 then the steel needs to be heated to 70 degrees. So according to this rule, if it is 33 degrees it is okay, but if it is 31 degrees then it needs to be heated to 70! Seems to be a bit inconsistent.

Can anyone shed some light on this inconsistency and the reasons why.

By jwright650 (*****)

Date 01-23-2008 14:01

I think the idea is to make sure moisture hasn't condensed and frozen to the surface.

By swnorris (****)

Date 01-23-2008 14:28

I don't see where Table 4.3 applies. The preheat temperatures in Table 3.2 are absolute minimum temperatures that should be used as a minimum "guideline", however, the actual welding conditions as well as experience in welding in those conditions may dictate the need for a higher preheat temperature. Obviously, the cooling rate is faster in colder temperatures, so preheat at a higher temperature than the minimum is not a bad idea. Other factors, such as the chemical composition of the steel, joint restraint, heat dissapation, and arc heat are affected by the amount of preheat, and as John mentioned, the presence of hydrogen in the weld metal as a result of insufficient preheat.

By jwright650 (*****)

Date 01-23-2008 14:43

When you're talking about preheat...AWS D1.1:2006 Paragraph 3.5 and C3.5 along with Paragraph 4.7.4 talk about the reasons for requiring preheat and maintaining interpass temps...basically what Scott has already talked about. And Table 3.2 gives the temps to remain prequalified. And then there is Annex I that gives even more reasoning on this subject.....

By Kix

Date 01-23-2008 14:49

What code are you working to? This is a good question! If it's 32 or even 40 deg out it would still be good practice to sweat all the moisture out in my opinion.

By csd72 Date 01-23-2008 15:02

I am using D1.1 - 94.

By jwright650 (*****)

Date 01-23-2008 15:13

I would grab a copy of D1.1:2008 when it finally is available(I have my order in already)....lots of these paragraphs and Tables have changed since the 1994 edition of D1.1 was released.

For instance: AWS D1.1:94 Table 4.3 was changed to Table 3.2 in AWS D1.1:96......