Maximum Interpass temperature for A36

By 803056

Date 10-22-2013 14:33

What welding standard are you using Big Bob and is notch toughness imposed by the Engineer/Owner/code?

Al

By BIGBOB

Date 10-22-2013 14:57

We are welding to D1.1 There are no notch toughness requirements imposed.

By 803056

Date 10-22-2013 15:28

You can take a look at the footnotes found at the end of Table 3.2 contained in AWS D1.1-2010. There are limitations on the maximum interpass temperature for several specific base metal specifications listed in the footnote. If the material specification for the material you are welding is not listed, there is no maximum interpass temperature limitation imposed by the code.

Best regards - Al

By BIGBOB

Date 10-22-2013 15:52

Thanks for your response Al. I had read that earlier but thought that maybe there was information elsewhere that I had not found. Do you know of ANY code that would limit the maximum interpass temp in A36 carbon steel?

By 803056

Date 10-22-2013 16:12

There may be, but when there is a maximum interpass temperature limitation imposed, it is typically because there are additional requirements for notch toughness.

Best regards - Al

By SCOTTN

Date 10-22-2013 17:14

The yield and ultimate tensile strengths of the weld metal are both a function of the interpass temperature. Higher interpass temperatures typically provide a finer grain structure and improved CVN notch toughness transition temperatures, but when interpass temperatures exceed 500 degrees F, this trend may be reversed. Several years ago, the AWS Position on the Northridge Earthquake recommended that the interpass temperature should not exceed 550 degrees F when notch toughness is a requirement, however, a maximum interpass temperature is not always required, and to my knowledge, D1.1 does not impose such control, with the exception of A709 HP570W and A852 that Al had previously alluded to.

By BIGBOB

Date 10-22-2013 17:27

Thanks so much guys. There is a world of informative people on these forums!

By Joey

Date 10-30-2013 09:18

Try API RECOMMENDED PRACTICE 582
Welding Guidelines for the Chemical, Oil, and Gas Industries

Table 8-1—Recommended
Maximum Interpass Temperatures

Carbon and low alloy steels 600deg F (315degC)

By welderbrent (*****)

Date 10-23-2013 01:25

Okay,

Now that that has been covered by the others, you have asked a couple of questions regarding the possible use of another code. Why would that be a consideration?

The first place you need to look with the information currently available to us is in the Contract Documents/Job Specifications.

There is a code that requires a maximum interpass temp. But until I know more from your end I will not disclose which one. Why would one be looking for information from any code when we work with specifics?

Have a Great Day, Brent

By BIGBOB

Date 10-23-2013 14:37

Brent,

There is no contract, the question was asked in general about max interpass temps for A36. One of my Co-Engineers was asking so I wanted to give him what AWS D1.1 would require, being as that is the code we (our company) work, or refer to most often. Then that got my curiosity going and that is when I asked if there were any codes that listed a max interpass temps

Thanks,
Bob

By jwright650 (*****)

Date 10-23-2013 16:10

I suppose the whole crux of the issue is how much/wide of a HAZ can you live with? You need enough heat being input to maintain the min preheat temperature(I'm thinking about large, thick[4" up] weldments). Another angle to check into would be limiting the interpass temps to 1200F per Clause 5.26.2 to avoid the possibilities of an undesirable microstructure or deterioration of mechanical properties in the surrounding material(HAZ).

By welderbrent (*****)

Date 10-23-2013 17:08 Edited 10-23-2013 17:12

Bob,

Okay, curiosity is a good thing in order to better understand both the materials as well as the codes we deal with and the things we sometimes hear and wonder- 'where did that come from?' and/or 'does that apply to anything I am or may be doing?' So here is why I was doing some double checking...

John is headed the correct way, at least as it applies to my thoughts on your question. Microstructure and phase transformations.

So, if you want to know where any references you may have heard along the way MAY have come from, look in D1.8 the Seismic Supplement to be used usually in conjunction with D1.1. It most definitely calls out a maximum inter-pass temp of 550°.

Remember, #1- D1.1 is a minimum standard code. #2- D1.8 is a supplement code. #3- Thus, D1.8 can take D1.1 to tighter tolerances and restrictions in order to produce slightly more quality control that will go even further to insure the soundness of the finished product. If I remember correctly D1.5 for Bridges has similar restrictions.

This is one reason several CWI's will write a WPS with a max inter-pass temp of 550° so that both D1.1 and D1.8 are covered by the one WPS. Besides, that little QC issue will show clients who know anything at all about metallurgy and microstructures that the fabricator/erector is giving their best efforts into a quality and safe product.

Now, having said that, this is where confusion also comes from because someone hears something when they are around a shop monitoring the max interpass or when around other inspectors who work on seismic jobs or when they are on a job where either the engineer or someone has referenced this max temp without realizing that it is specific to Seismic or the Contract Documents.

Have a Great Day, Brent

By js55

Date 10-29-2013 19:55

There is little that interpass temperature can do to deteriorate the properties of A36 material. A36 is a large grained hot rolled plate. Even SAW regimes will see grain refinement in the HAZ.
Personally if I had a concern for impacts I would not even mess with A36. I'd go with SA-516 or some similar grain refined material in which case the heat regime DOES become an issue.

By 803056

Date 10-30-2013 16:21

I am in agreement with js55 on this issue.

Al

By welderbrent (*****)

Date 10-30-2013 18:14

First off, I would point out that they asked a follow up question as to rather there were 'ANY' AWS codes that may limit inter-pass max temps. Which D1.8 does.

Second, D1.8 does not specify a particular material grade so it includes even the very forgiving A 36 steels in that restriction.

Third, I agree overall but with the following considerations:
a. Even A36 can be negatively affected by too much heat especially if occurring repeatedly.
b. There are many structural members that are dual (and multiple) rated for A36/ A 572-50/ A992/ A 529/ A709 etc. (not all at once but two or more often, I hope I didn't throw a wrong number in there but hopefully you get the idea). Thus, while one may ask about A36 it may include steels with other compositions as well.
c. Using these steels and even pure A36 (is there such a thing anymore?) as continuity plates, stiffeners, connection plates, base plates, etc would indicate the need to be careful even of a forgiving A36 so as to produce the highest quality product when it comes to bridges and/or tall, people containing structures. That is, after all, why the restriction is there.
d. I'm thinking of this more from a code aspect than a metallurgical aspect mainly as I am not a metallurgist. But I have seen A36 material really messed up by those who tried to do something because A36 was thought so lowly of as to it's metallurgical quality.

Have a Great Day, Brent

By BIGBOB

Date 10-31-2013 11:18

Thanks Brent,

That is what I was looking for, an answer that is in writing in an AWS code book. It's difficult to answer a question of "where did that maximum interpass temperature come from?" when you don't really know.

We list a max interpass temperature on our WPS's of 500F for low carbon steel but no one could determine where that was from, now I have a reference document!

Thanks,

Learning something new everyday!

Bob

By welderbrent (*****)

Date 10-31-2013 12:38

Bob,

It is entirely possible that it came from someone's whim, someone's overhearing of a conversation where others didn't really know, or maybe from the General Notes, Job Specificaitons, Contract Documents, Engineer, etc.

But, it does exist in one code anyway. It is not mandatory in D1.1. It is mandatory in D1.8. When D1.8 is a supplement to D1.1 for special conditions, EARTHQUAKES, does it not make sense that it improves the chances of high quality structures?

Again, D1.1 is a MINIMUM standard. D1.8 improves upon that. Any person desiring to reduce the odds for catastrophe should desire to know how to accomplish that. It doesn't take that much time to make sure heat does not go over a certain temperature. They have to be measuring for minimum pre-heat and inter-pass temps anyway. Why not continue to monitor for this maximum?

I don't argue the points that js and Al made about the forgiveness of A36 for maximum temps. But, as you mainly wanted to know where this 500° (actually 550) number came from, I believe we have answered your question. Hopefully others have found this helpful as well. And again, D1.8 does not remove A36 from this restriction.

I also have that number written into most of the WPS's that I write and use in my own shop. Limits the number of WPS's I need on file for one thing. Improves chances of quality work for another. If it ever saves one life, of which I may never know the truth of the matter, it is worth it.

Have a Great Day, Brent