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Up Topic Welding Industry / Technical Discussions / Z-loss.......
- - By bellaru (*) Date 04-11-2007 07:50
i understand  Z-loss  , but what does the actual "Z" mean......?
Parent - - By jwright650 (*****) Date 04-11-2007 10:20
bellaru,
The "Z" is actual dimension, they give that dimension an algebraic letter to designate it so that they don't have to draw a separate picture for each time the "Z" dimension changes. If you look at AWS D1.1:2006 Tables 2.2 and 2.8 you'll see that there are more than one dimension for various welding processes and joint configurations. A good pictorial of the "Z" loss is shown in AWS D1.1:2006 Figure 3.11(D).
Parent - - By bellaru (*) Date 04-23-2007 07:20
thank you John,,,,,,,,,but why is there "N/A" for GMAW...................?
Parent - - By jwright650 (*****) Date 04-23-2007 17:21
I think you might be referring to Table 2.2 and Table 2.8.
The GMAW isn't going to have info for Z-loss in the Vertical or Overhead positions...Horizontal and Flat only, which is in the next column over lists the Z-loss dimns.
Hope that I understood your question....
Parent - - By 803056 (*****) Date 04-24-2007 03:57
Come on JW, tell the man why there are no Z-loss values listed for the vertical and overhead positions for GMAW.

Best regards - Al
Parent - - By swnorris (****) Date 04-24-2007 14:07
The z loss factor is used to account for the likely incidence of poor quality welding in the root of a skewed joint.  The amount of poor quality weld in the root of the joint is a result of the combination of the dihedral angle, the welding process, and the position of welding.  For nontubular angles of joints between 30 and 60 degrees, the use of the GMAW process in the vertical and overhead positions is just not practical.  Once the z loss dimension has been determined, it's added to the required throat dimension.  Even though part of the weld in the root is considered to be of such poor quality as to be incapable of properly transferring stresses, the resulting weld will contain sufficient quality weld metal to permit the proper transfer of the imposed loads.  For the GMAW process in the vertical and overhead positions within the 30 to 60 degree range, the amount of poor quality weld metal in the root that is generated by the process, angle, and position cannot be replaced simply by increasing the throat dimension and still withstand the stresses that are imposed on the joint. 
Parent - - By 803056 (*****) Date 04-24-2007 14:25
That's still not the answer I was looking for.  Come on, why isn't Z-loss for GMAW in the vertical and overhead positions listed? This isn't a real tricky question. ;)

Al
Parent - - By jwright650 (*****) Date 04-24-2007 15:35 Edited 04-24-2007 16:27
Al,
You could go weld with spray transfer GMAW in those positions and report "the gravity" of your results back to us :-)(BTW wear your leather cape).
Parent - By 803056 (*****) Date 04-24-2007 16:26
Atta boy JW. Tell the whole story.

Al
Parent - - By js55 (*****) Date 04-24-2007 16:27
Nice pun John.
Parent - - By bellaru (*) Date 04-25-2007 07:23
what , so your saying that you can't make a V or H weld with those angles without the weld puddle falling out.....?

i just don't know about that......... what about with C02......?

isn't there a V & H test plate for limited thickness using GMAW..........?
Parent - - By jwright650 (*****) Date 04-25-2007 11:27
Yeah gravity plus the fact that there is no slag system with GMAW to help hold the really fluid puddle until it freezes. This is why they have pulsed machines and run in a short circuit transfer mode(which is not prequalified in D1.1) to run out of position with GMAW.

What you need to do is mock it up and weld it. Then section it and macro etch, so you can get an idea from this how much Z loss you are experiencing with your particular joint.
Parent - - By 803056 (*****) Date 04-25-2007 12:20
JW, I like your response.

Just one more question, how does the additional restriction added to the 2004 edition of D1.1 affect pulsing? I'm refering to paragraph 3.2.4.

Several of the pulsing machines on the market use "modern electronic technology" to produce a pulsing characteristic with power supplies that involve constant current rather than constant voltage and to make it more interesting, I believe some alternate between CV and CC as determined by the feed-back loop.

It ticks me off to no end that the manufacturers do not provide sufficient information to write a usable WPS with their pulsing machines. You have to accept what they provide in the way of canned programs or if you program them yourself, use an oscilloscope to really understand what the darn machine is doing. As one of the recent threads asked, "how do you calculate the actual heat input of the welding operation if you don't know what the machine is doing?" I have to agree with the question. I don't know the true answer.

Best regards - Al
Parent - By js55 (*****) Date 04-25-2007 13:54
Al,
Marketing departments don't want us really knowing much about the technologies they sell.
Parent - By jwright650 (*****) Date 04-25-2007 14:16
Al,
I hear what you're saying.....

The Commentary has this to say AWS D1.1:2006 C3.2.4:
"CV ower sources have volt-amper relationships that yield large current changes from small voltage chnges. Constant current (CC) power sources have a volt-ampere relationship that yield small current changes from large arc voltage changes. Best welding results for FCAW and GMAW are normally achieved using CV output. CC may be used for either FCAW or GMAW, providing WPSs are qualified by test in accordance with Section 4."

Regarding Short Ciruiting transfer(GMAW-S), the Commentary has a good description in the 2006 version of D1.1 C3.2.1
Parent - - By jwright650 (*****) Date 04-25-2007 14:23
If you want to see a couple pics of a macro etch check out this post...

http://aws.org/cgi-bin/mwf/topic_show.pl?pid=61008;hl=#pid61008
Parent - - By 803056 (*****) Date 04-26-2007 02:36
You got my point. Only GMAW and FCAW with a CV power supply are considered to be prequalified.

If you don't know how the new programmable power supplies work, you can't simply assume it is CV.

I had a real go around with Lincoln and Miller about this. Their reply was that most people don't get into it that deep. I do, because the bottom line is that a WPS qualified on Brand X, model C, program Y is only qualified for Brand X, model C, program Y.

Great photos by the way.

Best regards - Al
Parent - - By js55 (*****) Date 04-26-2007 14:37
If I may chime in, you make a very significant point there Al, in my opinion. It has always been a source of annoyance to me that the manufacturers seem to 'overlook' the necessity of informing their customers properly. The statement that most don't get into it that deep is no excuse. You won't find those provisos in any marketing brochure. But you will find yourself skewed, blued, and tattood when an informed inspector denies your WPS's and your deliveries are suppose to have been yesterday.
Of course this doesn't relieve the welding engineer of his own responsibility for staying informed, but hey, this industry is so huge you can't know everything. We all need help.
Parent - - By 803056 (*****) Date 04-27-2007 01:56
I have Lincoln's program for monitoring their PowerWave. Its helps a lot to see what the machine is doing. The problem is that everytime I reformat the hard drive on my laptop, I have to get a new code from Lincoln. I've gone a bout six months without the program because I'm too lazy to call them again (three times is enough.

I guess the next step is to buy an oscilliscope.

Best regards - Al
Parent - By js55 (*****) Date 04-27-2007 13:21
Funny where this welding world is going, having to use oscilliscopes to evaluate the operation of your power sources.
Parent - - By BryonLewis (****) Date 12-04-2008 14:12
I am reading D1.1 now and am confused about Z-loss.  Is it just a void in the weld at the weld root on dihedral joints?  I'm looking at some of the figures in the code to figure it out and it seems to be a void that is calculated into the weld metal that equals theoretical throat?  I can't seem to find a good definition for Z-loss. 
Any help will be very appreciated.
Thanks
Parent - - By jwright650 (*****) Date 12-04-2008 14:19
With the Pre-qualifieds.....Time has proven that the area at the root is not dependably welded, so they don't figure it at all in the calculations when figuring the weld size required.....so if you happen to get penetration to the root, it is just an added bonus. AWS has tested this over the years and just found that you just can't count on getting the penetration needed every time due to restriction to the bottom on those angles, so they won't allow you to count on it without testing(qualifying the joint).
Parent - - By BryonLewis (****) Date 12-04-2008 15:53
Cool. That makes more sense.
Parent - - By swnorris (****) Date 12-04-2008 17:31
Z loss reduction is a dimension to account for lack of penetration to the root of partial joint penetration welds.  Z loss dimensions will vary for nontubular and tubular connections for different angles, welding processes, and positions.

Take a look at this link:

http://www.aisc.org/Content/ContentGroups/Engineering_and_Research/Research1/AISC_Final_Report_Part_D.pdf
Parent - By supermoto (***) Date 12-18-2008 14:41
What are the different parameters, process, what changed to get more penetration?
Up Topic Welding Industry / Technical Discussions / Z-loss.......

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