As-welded surface finish criterion???

Date 03-06-2007 16:41 Edited 03-06-2007 16:46

Jon, you may have a hard time actually measuring the surface finish of an as welded surface. There are instruments that will give you a value in numerical terms, but I think they will not produce accurate results if the surface is not flat (machined surface compared to a welded surface). The instruments are called.......dang it, i cant find it, but anyway, it works on the same principal as the needle pickup on a record player. If the weld has large crests and valleys, which is almost a given, this will be factored into the roughness average which will give you very high numbers.

A very common, more primative solution is by use of a comparison standard. The have roughness standards that can be "compared" to the actual surface, and the instrument in cases as these are your actual fingernail. I know that sounds wierd, but there are many machine shops that still use the human fingernail for roughness measurements.

I'm not sure if you are familiar with surface roughness and examples of what each would be. A 125rms finish is comaparable to the finish on a B16.5 flange...not the gasket sealing surface (the sealing surfave would be close to 250), but more of the OD, where you can see the machining "lines" where the speed of cutting was fairly quick. A 500 rms finish would be close to a flame cut edge. I would also go as far as to say a SAW weld that is smooth and ripple free, would and could be close to a 125.

If you need anymore help, let me know. I've worked in a few machine shops and am familiar with surface measurements.

edit - BTW, it is also very common to have subjectivity with surface measurements between two companies and inspectors. Surface measurements are not 100% accurate, and even the $5000 machines have variences between them. Oh yeah, those instruments that measure the surface and give you a number......ARE NOT CHEAP!!!!!

By jon20013 (*****)

Date 03-06-2007 17:09

Thanks new tito. I know the machine you're referring to (I think) a profilometer? We have one and beyond being EXTREMELY slow (and costly) they too are subjective, you have to measure the average between peaks and valleys... I also looked at the machined surface comparables that you can compare using a toothpick or fingernail... these also seem too subjective.

At the end of the day, the last thing we want is our customer to be dissatisfied and requiring rework that may consume dozens (or more) manhours. To that regard, we both want something of known value and to the least degree of subjectivity. I haven't got the latest edition of B46.1 but the edition I do have (1985) also seems to leave us exactly where we started.

The SAW specimens we've provided are extremely smooth down the center portion... one could probably say comparable to a 125 but that also leaves me stuck with trying to compare a weld to a machined surface. Hmmmm?

By new tito (***)

Date 03-06-2007 17:26

Yes, profilometer is correct. It's been about 2 years since I've been in a machine shop and the book I have did not give the term for the instrument.

Personally, I don't think you could have a 125 on an as welded surface. If you measure the entire length of weld, and if there is one little bump in a certain section, that section would be out of tolerance. I would think the only way to get that finish is by grinding flat to the desired finish. Is there a possiblity that the customer could provide you with examples and also do in-process and final inspection to avoid rework?

As for the profilometer, that is by far (that I know of) the most accurate way to determine surface finish. There has to be some type of agreement between the two of you. Like I said, with surface measurements there will always be the possiblity of subjectivity.....even with highly polished machined surfaces. Sometimes with finshes, every single square inch does not have to be exactly 125.....close, but not exactly.

I hate to sound negative, but I dont think you can get 100% results for what you're trying to accomplish.

By js55

Date 03-06-2007 17:34

Jon,
I'm not sure its valid to say an as-welded surface cannot be compared to a machined surface. What would be the basis of the argument? It seems to me it matters little what process caused the surface. A surface is a surface is a surface. Especially when your prime consideration is for corrosion service. The criteria is a quantitative one, pure and 'not so' simple. And even though B46.1 does not specifically mention welding, it does say 'processes such as', which to me implies that the processes to be considered should not be limited to those specifically mentioned.
I think that once you take the plunge to machine the 125 will be easy to achieve and any subjectivity issues can be elminated froma practical standpoint.
So your problem is just to verify a 125.
I hope I haven't just described the water to a drowning man here.

By jon20013 (*****)

Date 03-06-2007 18:01

Jeff, new tito, thank you both.

Oddly enough, every single reactor vessel and pipe I have crawled through during my years in the nuclear construction phase were all as-welded and all either Strip clad or Electrogas welded... I'm sure any oldtimers out there would concur!

Jeff, you haven't described water to a drowning man, lol!! new tito, I agree we will have difficulty complying with a 125 finish unless we machine. It well may be that we simply have to bite the bullet and do some surface finishing... I have only volunteered to see if there are any other "known" standards which could be better used than the 125.

The customers concern with the surface finish is not corrosion however... that said, the customer's concern is avoidance of radioactive contamination... and that's their main purpose in specifying a finish.

By js55

Date 03-06-2007 18:13

Ah, I forgot its a nukey.
This thought, perhaps you could contact your pipe or plate supplier and inquire as to what method and criteria they use for finished materials, which don't trigger a special surface roughness requirement for nukey's. At least not in my experience.

By yorkiepap (***)

Date 03-06-2007 21:28

Hey jon20013,
You've introduced a fascinating issue and I am quite interested in the answers posted by all the respondents so far. I can understand their replies, and as a retired machinist, comprehend the factors that determine and establish a surface grading system. I do remember we even had variances and standards according to the material, ie: steel, SS, Al, brass, bronze, etc; and each differed. Each type has a standardized table of criteria to determine finish. Since welding has a multitude of variables and processes, has there ever been any attempt to formulate a grading system? As js55 responded, "a surface is a surface is a surface" unless a definition has been established throughout the manufacturing industry. If a customer pre-requires a finish parameter, how do you determine if a manual operation is necessary and additional work acceptable to his request? Does AWS have such criteria established or defined? Hope there is much more input on this subject....Denny

By jon20013 (*****)

Date 03-06-2007 21:34

Thanks Denny, although I've been around for a while myself, I'm hoping there's some wise old souls out there who may be able to provide some guidance... at the end of the day, if I have to do a machined surface well, so be it, but as a welding society we really ought to think about defining welds a little better than some of the old verbiage like "course ripples, valleys and grooves" or "ropey"... not that those terms didn't work in the good old days... it's just nowdays folks are all asking for more and better definitions...

By thcqci

Date 03-06-2007 21:58

MSC has surface profile comparator samples as was mentioned above.
http://www1.mscdirect.com/CGI/N2DRVSH?SISHNO=3009049&SISRCH=2&SIS0NO=525885&SIT4NO=19136058&SIOR=1

By js55

Date 03-06-2007 22:11

Doug,
Those, I think are a step in the right direction but I'm not sure it eliminates the 'subjectivity' issue Jon is concerned with, since the evaluations are visual. And how would they apply to welds for say radioactivity impingment or for corrosion/erosion quantitative verification? Is there language attached to these comparators that could provide a starting point?

By jon20013 (*****)

Date 03-07-2007 12:50

Thanks, we have a few of those comparators around but for some reason, my QA VP doesn't think they are appropriate for welded surfaces...

By js55

Date 03-06-2007 22:07

Jon,
Help me out here, I don't think I fully understand your dilema, other than a lack of uncomplicated measuring methods. Is this true?
Denny is right, as well as yourself, this is an important issue.
Are you proposing that the AWS develope some surface description clarity, and perhaps a more convenient method more amenable to welding, as opposed to wazoo stylus methods and such.
I'mnot sure how that would play out othetr than the quantitative evaluations there. Perhaps just a better way of doing it? I'm confused.

By eekpod

Date 03-06-2007 22:44

I have a wild suggestion, but do you have the AWS plastic thermal cut profile guide? Its a small plastic compariter that is used to show the four different acceptable thermal cut profiles when cutting plates. I don't have it here at home, it's in my office and I use it when we hire new fitters to show them what profile is acceptable depending on the thickness of the material.
You might be able to use it as a guide, and also to show it to your client and say, "we'll shoot for profile #3, how's that sound?" and this way it's measurable, comparable, and easy to relate to. Just a suggestion, good luck, Chris

By jon20013 (*****)

Date 03-07-2007 18:54 Edited 03-07-2007 18:57

Chris; I am familiar with the AWS plastic thermal cut profile guide you mention and it's not totally wild, it's a good thought, but in my mind it would still be like comparing lemons and tangerines. Still, it's just that type of "outside the box" thinking I believe I'm looking for! <Just think up some way to define numberic values that go hand-in-hand with weld surfaces instead of cut surfaces>.

By jon20013 (*****)

Date 03-07-2007 13:06

Jeff, my dilema is quite possibly just an uncomplicated, inexpensive method to objectively evaluate the surface of a finished weld. While I'd love to suggest AWS (or others) define some "objective" criteria to define my situation, my situation really only applies to welds deposited by strip clad SAW method and if such a standard were to be developed it would be of admittedly limted use; to that end I can't truly justify such a request. That said, our world is evolving very rapidly and there will come a time (guarenteed) when someone wishes to have weld surfaces defined much better than they currently are.

My client is simply concerned with how to adequately define the surface of a weld which will minimize retention of radioactive contamination, also know as "fleas," thus reducing radiation in general. Their concern has nothing to do with minimization of corrosion or anything else we might consider "normal" concerns. My concern, with respect to my customer, is finding a standard or definition that will be relatively simple to use and understand while simulataneously allowing repeat of measurements; i.e., verification by others. In my working world (nukies) there are many, many, many parties that will check the work we've performed... and we all know how opinions are... I may think a surface looks just like the comparator plate while another may see one groove I overlooked and latch onto that as his/her Waterloo.

Comparator plates are just fine, I've used them many, many times in the past but like my QA VP, it's hard for me to really say "this 125 finish looks just like the weld surface I'm looking at. Heck, the center of our SAW beads are probably "smoother" than the 125 finish... but with extended ripples...

I don't think there are any simple answers but I'm very pleased to see the interest in this topic!

Perhaps as a start, we might all ask ourselves how we would define "coarse ripples and valleys" or "ropey" to the welder we've just busted out after an all night drive to the test booth...

By CWI555

Date 03-07-2007 04:20 Edited 03-07-2007 04:29

Jon,

You've struck on something that has been cause some grief for me the last few years. "course valleys and ripples, smooth transition, ropey, and multiple other terms coined in various codes without a definition. There was a time when most you meet understood and agreed with what it was. Now it has to be defined as basic common sense doesn't stand up to a production schedule these days. These 'subjective' terms just won't cut it any more.

I did have an answer in here, but It occurred to me some of that answer might be proprietary. I suggest making a standard that all agree on and using an optical laser profilometer. It should give you quantitative and qualitative data sufficient to meet your needs.
Regards,
Gerald

By yorkiepap (***)

Date 03-07-2007 04:30

Hey Jon,
Since this post really got the mental gears spinning, and a real challenge, I would really like to see the minds of the ever-thinking welders who get involved here, get some kind of process initiated to establish a "welding surface chart", or something to that effect. Since I keep my mental processing on "simple", because it is so much easier that way and generally works best, I feel a visual chart, depicting the various weld configurations by surface appearance would be a start. Just as a welding drawing indicates connecting weld specifications by established parameters, a surface chart would also indicate physical parameters for appearance. I do see, at times, non-welding engineers do not fully interpret the physical changes in metal when welding. There was a recent past post discussing length shrinkage after welding and the lack of engineering expertise to foresee this factor.

After researching my small welding library, I estimated there were close to 1000 photos of welds. I am sure in the vast arsenal of literature in the AWS, enough photos of welds that show physical attributes could be used to set up a grading/numbering system to indicate a surface definition that could be used by a manufacturing engineer to indicate a weld surface appearance that is acceptable for his project. I'm confident that the staff of AWS combined with weld engineers could provide a chart as this, and possibly have an addendum to the AWS Welding Manual.

I believe js55 is on the right track saying "AWS develop some surface description clarity", and it would entail physical dimensions of height and width, all that would be in the guidelines of a proper AWS defined weld. And I believe those guidelines were established for weld integrity, correct???

Anyway, I'm rambling, but the curiosity is really an itch.... I guess, as a welder, the appearance of a weld is quite important to most of us, as is the integrity of that weld. Gotta admit, nothing like looking at a 20' length of sweet bead on those big beams. Ok guys/gals... your turn... let's start something.....Denny

By js55

Date 03-07-2007 14:39

Visual comparators are not the answer. I think what Jon is indicating is that something quantitative, something that can be hard measured, something that can be tied into engineering standards and equations is required. Visual references won't do that. We have methods in existence to do what Jon needs its just that they are to complicated and inconvenient. I think that's because they were developed by industries unrelated to welding.
Comparators won't work because when evaluating, say, a corrosion rate (for example weight loss per unit volume per increment of time), an engineer cannot quantify that rate with a subjective visual reference no matter how precise it may seem. There needs to be a 'number' tha can be tied into an equation. We have this, its just that its not amenable to a more convenient approach to welding applications.

By js55

Date 03-07-2007 14:50

I guess a simpler way of putting it is that visual comparators are fine for quality control but not for quantitative engineering design. The sophistacted methods availabe are good for quantitative engineering design but not for production. We need something simpler and more convenient, like Equitips and Nitons. And with a language to go along with it.

By jon20013 (*****)

Date 03-07-2007 15:06

Well said, as usual Jeff!

I've just gotten off from a long phone call with my Customer. In the end, I think we both agreed that some workmanship samples will be made. That doesn't make the concern go away, it just takes the monkey off my back. One day, maybe 20 years from now, maybe less, all of the old-timers of the future may have to address similar issues. My Customer is very accommodating, the Customers of our members future may not be nearly so accommodating.

Those who would be the technical authors of the future, those who would further the codes and standards of today need to think about these things... Our current standards have worked just fine for the current and recent past but may not have appropriately defined criterion for the future.

There are an awful lot of great minds in this Forum, I hope this thread will receive a bit more input before closing it, only to be reopened at some later date...

By Lawrence (*****)

Date 03-07-2007 15:18

Jon,

I think the notion of workmanship samples is a winner.

ISO often integrates workmanship samples into it's language for quality validation purposes, and they are as strict about methods as anybody eh?

By js55

Date 03-07-2007 15:39

Jon,
Could you explain how your workmanship sample has provided a resolution for you and your customer? I've never done that before. Maybethere is something here that could fill in some gaps in my understanding

Lawrence,
How are workmanship sample integrated in ISO?

By jon20013 (*****)

Date 03-07-2007 16:00

Jeff, I'm somewhat surprized you've not encountered workmanship samples before? I have run into it dozens of times in my past. At a few shops they actually had weld samples at various locations around the shop with statements under each "Acceptable" and "Unacceptable." In each instance of "unacceptable" the fault would be identiified... "undercut" "overlap" "crack" "porosity" etc.

In the case of my customer, we all know what type of surface is requested, we're only having trouble with definitions. That said, the Customer has suggested we submit samples ranging from "good" to "bad" with a few relative finishes... retention of those specimens will be in their court. The Customer is also planning NUMEROUS hold points in our shop so the inspectors or engineers will have an opportunity to see what the surfaces will look like before visiting and they can also physically bring the sample with them as a visual comparator... one which has been evaluated and "pre-blessed" by their QA/QC Department.

Once all work has been completed and accepted, the burden of "proving" acceptability becomes theirs.

By js55

Date 03-07-2007 16:33

It is interesting isn't it. My encountering workmanship samples has been limited to instructional demos and such. And few at that. I have never encountered a situation where they were incorporated into a QC system, widely distributed in the plant, or used to disposition a customers concerns.
I keep digging on this thing because I think you have really struck upon an important issue. And one I think may be a next generation QC priority, especially given the increased aggressiveness of corrosion mediums, the increase utilization of overlays, and of course the possibility of increased nukey work (for radioactive capture) here in the States.
Having said that, I would be interested to hear how your customer 'conceptualizes' or 'quantifies' the workmanship samples into an idea of realizing a low level of radioactive capture in service. Not sure I've made my question clear.
As far as your customer is conerned how is he planning on integrating your 125 RMS requirement into the workmanship samples as a resolution?
I mean, if you achieve 125 do you need the samples, or has the sample agreement allowed you to eliminate the 125?
I know once your customer gives the OK you guys are good to go, since I'm sure the radioactive capture is not your engineering concern. I suppose the idea is what are they thinking.

By jon20013 (*****)

Date 03-07-2007 16:47

Jeff, I appreciate you thinking this is an important issue. I think our younger members will have to face this one day.

As for our customer is intending to 'conceptualize' or 'quantify' the workmanship samples, it's my intent to send them perhaps as many as 1/2 dozen samples ranging from as-welded to a full 125 finish with varying degress of grinding in between. Their QA/QC Department will compare the samples to the surface comparators and "bless" a few, which would give their inspectors (as Lawrence indicated) somewhat of a go-no go.

This doesn't solve the issue, as I mentioned earlier, it only takes the ownership off my back and places it on theirs to provide a better definition of an acceptance standard.

By js55

Date 03-07-2007 18:15

Jon,
This is an important issue. The services are getting nastier, the temperatures and pressures higher, corrosion testing more sophisticated and specific, end users more confused about what they really want, and the alloys are getting diverse to the point of being downright confusing.
Nobody can predict how a specific alloy will react in an environment of which there is no empirical data. And every environment is virtually unique. The added variable of surface roughness aggravates the problem.

By jon20013 (*****)

Date 03-07-2007 18:45

I'm sure the HP Folks might have some good guidance on the degree of smoothness required to produce a reduction of contamination. In my feeble mind, I can't imagine smooth ripples having any play in the matter but certainly could in those areas that might be rough enough to retain any residual particulates; i.e., perhaps the toes. Even in saying that, I don't know how such could be adequately defined in measureable terms?

By Lawrence (*****)

Date 03-07-2007 16:13 Edited 03-07-2007 17:39

Jeff,

I can't quote chapter and verse out of ISO doccumentation because at the time I was involved I was occupying a lower position on the food chain. But workmanship samples of good and bad welds were asked for with several repair types at the turban engine rework facility I was employed by. The examples could be comparators of surface prep, fit up, titanium tints, weld progression or types of sequencing steps in a complex repair, you name it... Much like a go no go gauge.

We were told the auditors responded favorably but again thats the extent of my knowledge of the audit... The FAA also took note of our examples and training practices and reccomended them to others in the same field.

Edit: We also developed "welding technique sheets" WTS for a number of projects that had custom fixtures or argon backups designed for that job alone. They were noted on the class 1 repair doccuments as were the backups and kits. The kits often contained photographs of correct fixturing or set-ups. Not exactly a WPS and not exactly a Weld Schedule. Just a tool... but often times very valuable.

By js55

Date 03-07-2007 16:34

Lawrence,
Interesting idea. Thanks. Not enough ISO experience on my part.