Chemistry question

Date 08-20-2007 16:07

Why did you do the chemistry testing...is it a corrosion resistant overlay application? What is the base metal and filler metal spec?

By dmilesdot (**)

Date 08-20-2007 16:15

base metal is A709 Gr. 50 W, filler metal spec is AWS A 5.23. It is a weathering steel PQR. We are required to have the chemistry done on the weld metal.
Dave

By HgTX

Date 08-20-2007 18:30

From what spec are you getting the chemistry requirement?

Hg

By dmilesdot (**)

Date 08-20-2007 18:47

The chemistry comes from the A5.23

By Bill M

Date 08-20-2007 19:31

What is the nickle content of the base metal?
Was the chemistry taken from an "all weld metal" sample, or could have some of the "extra" nickle come from dilution with the base metal?

By CWI555

Date 08-21-2007 06:19

If a proper weld pad test was performed there would be no dilution. SFA 5.23 is identical to AWS A5.23 and in it for chemical analysis Fig 2 it's 4 weld bead layers high, and 3 wide for 5 inches of weld material only. Top layer is removed and sample taken from the next layer, testing to ASTM 350. Now if the base of the test had elevated nickel and the wrong layer of the pad was used for sampling then dilution would be possible. All in all it sounds like the wrong filler was used even though I doubt that addition count of nickel would really mean much.

By RonG

Date 08-20-2007 20:04 Edited 08-20-2007 20:13

A5.23 is for Low Alloy electrodes & Flux for SAW. There are many chemistries and flux wire combinations s in that section. Which are you looking at? F3 has a Ni requirement of .70-1.10. The extra Ni should enhance the mechanical & other properties. Does your PQR meet the or exceed the requirements?

By HgTX

Date 08-20-2007 21:44

How kosher is it to apply A5.23 requirements to a D1.1 qualification test? A5.23 tests are typically performed by the electrode manufacturer.

By CWI555

Date 08-21-2007 06:26

Read 1.1 of the scope of D1.1. Contract documents and or the cognizant engineer can make specific exceptions or modifications to any part of D1.1. If either stipulated this test, it then becomes a requirement based on the code.

By dmilesdot (**)

Date 08-21-2007 11:23

Our code is the New York State Steel Construction Manual and the chemical analysis of the all weld metal is requireed on weathering steel applications. We refer to the AWS 5.23 for a chemical analysis. My question was, what would it mean to the quality of the weld if the Nickel percentages were high? ( or low) Typically when we reject a PQR for weathering steel it is because the Nickel doesnt meet the range given in A 5.23. Im not sure wheather the fab shops retest the original sample or if they weld a new one. Which raises another question, what parameters do they change (assuming that they are within allowable percentages) to alter chemistry?
Dave

By PhilThomas (**)

Date 08-21-2007 12:17

The higher nickel content can change the way the weld "weathers" which is one of the reasons it is specified. Higher nickel will reduce the weathering appearance. Having said that - will it make a weld unacceptable? I don't know.

You can adjust parameters to increase or decrease the alloys "burned out" across the arc, but nickel is one of the more difficult alloying elements to burn out. Things like silicon and carbon can quite easily be affected by parameters but nickel and tungsten are less influenced by the heat of the welding arc.

You say "the PQR was rejected for nickel" but later you say it was all weld metal...those statements seem contradictory. If you are going to compare the filler metal to the specification it needs to be done using the undiluted pad specified in A5.23 to remove the influence of the base metals. Have you tried that using this lot of wire?

By dmilesdot (**)

Date 08-21-2007 17:41

Is there a reference guide that I should be using for PQR's to determine the correct chemistry on weathering applications? Typically a fabricator will use portions of a Charpy specimen or all weld metal specimen after they have been mechanically tested. Until now I have used the chemcial analysis that was listed in A5.28 for Sub Arc.
Thanks
Dave

By js55

Date 08-21-2007 19:38

I have to say this thread has me a bit confused. I'm not sure how actual 5.23 chemistry factors into a PQR, other than to state simply spec/class. You can specify exact chemistries if you wish, for perhaps a job specific requirement, but it isn't code binding. Corrosion overlays and non spec/class fillers and weld metals are different, and will have chemistries specified.
And there still seems to be no indication where the extra nickel came from that would justify its specification beyond 5.23. Unless I missed it.

By PhilThomas (**)

Date 08-22-2007 00:05

I agree. I can tell you that given the current price for nickel, no manufacturer is intentionally exceeding the intended classification requirement. If anything it would be more towards a lean chemistry.

By js55

Date 08-22-2007 13:11

Phil,
Ain't that the truth. Nickel is insane. And since seldom is the price of the filler alloy consider before award of a contract there is natural gravity toward the cheaper leaner alloys. But the gravity going the other way is that for the design engineers the price of nickel is an issue too, and they are attempting to save as much as possible. If a service is jsut barely above whereit needs to be the weld may be the weakest link with mathcing fillers.
Whatever consideration there is for corrosion alloys should not be taken without consulting manufacturers such as yourself with reference to a specific service. I always thought that knowledgeable fabricators should consider themselves a second line of defense and research the application just as responsibly as the end user or general contractor. Corosion applications are confusing and difficult enough withut due consideration.

By js55

Date 08-22-2007 13:47

Wow! Am I in the wrong thread or what? Refer to the C-276.

By GRoberts (***)

Date 08-23-2007 02:57

The chemical requriements for AWS D1.1 and D1.5 for weathering steel only require a 1% nickel minimum. Are you sure you are supposed to be comparing to the original electrode specificatoin?

By VeryMetal Date 08-23-2007 17:54

Added nickel should improve impact toughness and reduce cracking in the weld metal, especially in low-alloy fillers.

By HgTX

Date 08-23-2007 19:07

The New York State Steel Construction Manual doesn't follow D1.5 (though it was the original basis for D1.5). They have separate chemical requirements for weathering steel chemistry (similar but not identical to the A5.23 requirements for those particular designations), and the chemistry is to be taken from the AWMT specimen or the broken ends of the Charpy specimens. This actually is in keeping with the A5.23 alternative of taking the chemistry from the reduced section tension test specimen. Though A5.23 does say, "In case of dispute, the weld pad shall be the referee method." So dmilesdot might want to contemplate doing an A5.23 weld pad for chemistry. (I know, that's not what dmilesdot was asking.)

Dmilesdot doesn't say which flux-electrode combination is being used, but A5.23 has a range of 0.75-1.10 for Ni1, so let's assume that's it. NYS SCM requirement for Ni1 is 0.80-1.10, a little more restrictive (and the PQR would still fail). But I'm not sure how fair it is for the NYS SCM (if I may dare question the NYS SCM...) to require similar chemistry with a weld procedure qualification test performed with A 709 Gr. 50W (or A 588) base metal, where nickel might be as high as 0.50%, as an A5.23 chemistry test that might use A 537 for the base metal, with nickel no higher than 0.28%. In theory, the middle of that groove should show little to no base metal dilution, but if that were a completely safe bet, why would they bother with the weld pad?

Hg