Thread: Different welding processes compared for heat input

Multi pass MIG welding is something seldom ever mentioned...

I look at the chart on the 250 amp MIG I have.. All it has is steel thickness..

It gives you no indication that steel thicker then 6mm can be welded with a 250 amp machine... It does not seem to take into consideration multipass welding, so common with stick welders...

Originally Posted by .RC.

Multi pass MIG welding is something seldom ever mentioned...

I look at the chart on the 250 amp MIG I have.. All it has is steel thickness..

It gives you no indication that steel thicker then 6mm can be welded with a 250 amp machine... It does not seem to take into consideration multipass welding, so common with stick welders...

I think I mentioned in an earlier post that welder manufacturers are full of @#%* when it comes to their machines capabilities. Anything more than 3mm, you would be reaching for a grinder to do a bit of weld prep and at 6mm, you are into multipass territory for best quality welding.
When I undertook my WTIA 8G certification, I doubt that the 200A mark was passed at any time. The four welds reguired are 10-12mm HV fillet on 12mm plate, 10-12mm vertical fillet on 12mm plate, horizontal butt on 10mm plate with back gouge and backing run and finally a butt joint on pipe horizontal axis, rotated. All must achieve 100% penetration and are subjected to visual, root bend, face bend and nick break destructive testing.
As a matter of interest, I used .9mm wire and CO2 used for all welds. Mixed gas was an option, but was very prone to gas pores in the root of the fillet welds.

I think these days, the majority of welders ( I include non trade qualified welders that weld for a living anyway) are pretty poorly trained and have pretty poor depth of knoweledge...but that is pretty typical of all trades these days.

I recon your actual "tradesman welder" (a tradesman who's primary skill and training is welding) would be a pretty rare beast in this day and age....even rarer one who has good depth and breadth of knoweledge.....particularly seriously heavy stuff.

Sure there are still plenty of "Boilermakers" out there......but very few would have ever seen a boiler or even worked on a straight forward pressure vessel.....the majority would be involved in "light fabrication" and would never gain certification.

So much of the expectation is single pass welding with little or no preparation or clean up afterward...because it is fastest and cheapest..and that is what people (and accountants) want to hear.


All that goes before you even consider the matter of tallent and born hand skill.

No doubt, some of the amateur back yard welders here, will weld rings arround many current tradesmen....but that is true of so many things.

We are now probably into the third and forth generation of poorly skilled tradesmen.....most of the young blokes would be lucky to have seen or spoken to a true master tradesman.

Its forums like this that give us access to the last of the living masters.

Thanks to those who come to share what they know.

cheers

Originally Posted by soundman

I think these days, the majority of welders ( I include non trade qualified welders that weld for a living anyway) are pretty poorly trained and have pretty poor depth of knoweledge...but that is pretty typical of all trades these days.

I recon your actual "tradesman welder" (a tradesman who's primary skill and training is welding) would be a pretty rare beast in this day and age....even rarer one who has good depth and breadth of knoweledge.....particularly seriously heavy stuff.

Sure there are still plenty of "Boilermakers" out there......but very few would have ever seen a boiler or even worked on a straight forward pressure vessel.....the majority would be involved in "light fabrication" and would never gain certification.

So much of the expectation is single pass welding with little or no preparation or clean up afterward...because it is fastest and cheapest..and that is what people (and accountants) want to hear.


All that goes before you even consider the matter of tallent and born hand skill.

No doubt, some of the amateur back yard welders here, will weld rings arround many current tradesmen....but that is true of so many things.

We are now probably into the third and forth generation of poorly skilled tradesmen.....most of the young blokes would be lucky to have seen or spoken to a true master tradesman.

Its forums like this that give us access to the last of the living masters.

Thanks to those who come to share what they know.

cheers

Your generalities and lack of knowledge do not do you any favours as you do not know what is involved in the training of a certified welder. In fact any TAFE teacher would take strong exception to what you have written and you have no foundation for any of the assumptions you have drawn. You should get your facts right before entering into a debate you know nothing of.

I admit I don't know anything directly about TAFE but I know a several older TAFE teachers a who have gone in and out of TAFE and industry and they constantly complain about the way tradespeople are trained and how the graduates seem to know less than they once did when they graduated. I also know about a half dozen tradies who no longer take on recently completing apprentices. A common theme is that apprentices don't get enough supervised practice across a range of activities, with the tradies usually blaming TAFE and VV.

I'm skeptical enough to admit that "back in my day" is a recurring theme amongst folks above a certain age and the numbers may not support the facts but it would be good to hear direct from experienced TAFE teachers about whether the number of supervised practice hours have changed.

My own familiarity is with the university system. In the 70's, for subjects with a practical component we did an average of 3 hours a week for 28 weeks of the year of supervised laboratory. This year the average is 1 hour a week for 24 weeks of the year which is a reduction of 350%. There has been some substitution of hours devoted to "hands on" by computer simulations and data analysis but this is not what I call practical work. The reduction is of course driven by money but it has had a significant impact on what graduates are able to do by the time they graduate. I've always argued that stuff like computing can be picked up as required but supervised prac work is much harder to come by outside of training institutions.

Originally Posted by BobL

I admit I don't know anything directly about TAFE but I know a several older TAFE teachers a who have gone in and out of TAFE and industry and they constantly complain about the way tradespeople are trained and how the graduates seem to know less than they once did when they graduated. I also know about a half dozen tradies who no longer take on recently completing apprentices. A common theme is that apprentices don't get enough supervised practice across a range of activities, with the tradies usually blaming TAFE and VV.

I'm skeptical enough to admit that "back in my day" is a recurring theme amongst folks above a certain age and the numbers may not support the facts but it would be good to hear direct from experienced TAFE teachers about whether the number of supervised practice hours have changed.

My own familiarity is with the university system. In the 70's, for subjects with a practical component we did an average of 3 hours a week for 28 weeks of the year of supervised laboratory. This year the average is 1 hour a week for 24 weeks of the year which is a reduction of 350%. There has been some substitution of hours devoted to "hands on" by computer simulations and data analysis but this is not what I call practical work. The reduction is of course driven by money but it has had a significant impact on what graduates are able to do by the time they graduate. I've always argued that stuff like computing can be picked up as required but supervised prac work is much harder to come by outside of training institutions.

Thanks for your comments.

My biggest beef with current training is that due to the ability to custom tailor apprenticeship modules, traditional skills such as stick welding can be overlooked if your employer wishes. A previous employer of mine made the statement that nobody uses stick anymore. That may have been partially true for his workshop as it was primarily an aluminium workshop, but led to an apprentice who did not possess one of the most basic skills.
My next beef is that every second apprentice wants to be a "specialist welder", whatever that may be. They forget that one must first become a competent tradesman before you can branch off in any direction and are lost if they do not have access to a fully equipped workshop. Many have poor problem solving and improvisation skills.
As to the old tradies being better. Some are, some aren't. The tradies that keep up with developments within the trade are very well rounded, those that are stuck in 1950 are a damn menace.

My statements are mot definitely general.....and I believe they are accurate.

The demise of the large workshops right across all the trades has reduced the skill, experience and training level in the trades in general.

In addition to the trade school hours that the apprentices completed the big workshops had additional training both formal & informal and apprentices where generally rotated thru a wide variety of work and thru the tutilage of a range of master tradesmen......and in general there where more tradesmen than apprentices in almost all workshops.

These days a very large portion of apprentices are not even employed diretcly by the company that may be working for at the time.....group apprenticship schemes are in general operated as labour hire companies and the end use employers are not employing apprentices because they want to grow a tradesmen for future employment in their company, but because they are cheap labour.

As for not knowing about the industry or the TAFE system.

These days most of the basic trades are certificate 3 level qualifications that result from arround 21 weeks ( some a little more more) total formal training over 4 years and often it is pretty slow paced...lots of kids are comming out of highschool with cert 2 level qualifications....cutting that time down considerably.
Equavalent cert 3 qualifications in other areas can be knocked off in a couple of weeks full time.

I hold 4 certificate 3 level qualifications and a cert 4 in workplace training and assessment.

I have one family member and several close friends that are industrail trainers or tafe instructors of some sort, one runs a group apprenticship scheme.

I was speaking to one fellow who teaches manual arts ( or whatever they call it now) at high school.....his biggest beef is the concentration of teaching design rather than hand skills.....afterall the higherst majority of those who do manual arts at school and go on to a trade will never design anything....yet they lack the basic hand and tool skills required in the trades.

I do not have any metal trade qualifications, but there are several metalworkers in my family.

I continue to attend training courses for varous reasons ( I attend one or two training courses per year on average) & I remain gob smacked at the level of knoweledge and intelect displayed by the other partisipants.....most of the time the courses have a trade prerequsite and the others should know more than me because they have higher trade qualifications and more experience in that particular area.
Without exception I am always in the first few finished the assessments and with the least errors.
I consider myself of average inteligence.

As I travel arround and work with others, Above all what strikes me right across the trades...is people who should know more than me but don't...even tough it is their trade and not mine.

People who do not know about methods, equipment and materials, what they can do for them or where they come from.

Im not talking about fancy complicated stuff either.....I'm talking about simple basics and that founded on them.

Back to the point about multipass welds.
All the books and the previous trade skill tells us how to get good penetration and how to weld effectivly thick material beyond the capacity of the machine.

but these days they want to cut it square, but it up and blast away in a single pass......and the big machines that will do that are way cheaper and more available these days....that is what is expected and that is what is sold......the suppliers sell to the expectation and the skill level.

cheers

My attention span isn't long enough

Chris parks .I was a qualified TAFE teacher and have trained students pressure vessel standard under AS 1796 - probably 200 of them in all processes. Listen to Karl BobL and soundman well, because they are on the money.


I'll throw my hat in the ring here. I support what Soundman, Karl and BobL have said.

Many certificates issued these days are truly not worth the paper they are written on. Too many safety based certs are issued on a tick and flick type test and you get get tested again and again until you get the question correct.

TAFES are being forced into this nonsense because of the overwhelming competition from private providers who get away with murder doing the same thing. Tafes now are at the point where they have the teachers go out to sell courses to maintain funding. To make the courses attractive to industry much has been removed on the basis of an outright cost cutting necessity. Industry only cares about the certificates and the cost involved in obtaining them and that's where it all stops.

Not too long ago I did some welding inspection on a batch of conveyor frames. With the different sets and configurations there were probably 6 or 7 hundred of them, which later had to be hot dipped galvanized for service on or near the marine environment. The construction company was one that had made conveyor frames for many years. The welders were a mix of tradesmen boilermakers and first class welders who had to pass a test and were issued a certificate in line with the requirements of the major international contractor.

Those trained and experienced people ( in general) could not or would not weld to the standard required. The process was gas assisted flux core using a mix of good quality machines but suitable for the task

Not real picky things mind you, but stuff well within the capabilities of trained welders, like this:

• No craters at the ends of runs or on the corners,
  
• No slag inclusions.
  
• No porosity greater than a specified level
  
• Weld profile (leg lengths) not to be less than a specified dimension.
  
• Cleaning the spatter from the job
  

The inspection team and I failed 50% of the initial inspections and 30% of the repairs. I spoke to a few of the welding operators to find the nature of the problem. Part of it was attitude and the belief that the certificate covered them and partly poor training.
In (my) smoko i watched a welder and what he did. The gas nozzle was not properly cleaned but permitted to load up with spatter. The technique was to hot dip the nozzle in the goop but not manually clean it when required. The built on spatter would self release when it loaded up enough and the lot fall out into the welding pool. In addition I noticed that the machine digital voltage display was miles off what I thought it should have been.
The rejections mainly were the responsibility of the person doing the job and their supervisor/s who then failed to apply a remedy to problem after the repeated fails. I informed the supervisor of what I saw, but my understanding was that not much was done about it. 50% failure in a production environment is dreadful and initially it was down the the welding operators.

The underlying cause (in my opinion) is the change to that part "New apprenticeship system where apprentices and now trainees and not trained in the broad spectrum of applicable trade skills ,but rather than, to those narrow band of skill sets required by the employer (at the time of apprenticeship or trainee ship). Thus when an apprentice or trainee moves away from that the original employer and becomes a tradesman he/she is left to their own devices as far as obtaining the extra training required to operate with in the parameters of the new employers skill set requirements. There is virtually no where to go to learn these extra but necessary skills as Tafes don't offer the evening courses in these skills, all that often due to funding and numbers.

To their credit some companies do institute internal training to compensate for this.

Grahame

I think " competency bassed training" has a lot to answer for.....and ALL of our trade training is competency bassed.

A student is either "competent" or "not yet competent"

There is no allowance, benifit, encouragment or means of measuring excelence...in fact it may be activly discouraged.

There is no measure permitted where students can be compered for relative merit.....they are either competent or not yet competent.

And there is no acknoledgement that any given student may never be competent.

Skill, aptitude or dilagence are simply not acknoledged as being a factor or even existing.

cheers

Originally Posted by soundman

I think " competency bassed training" has a lot to answer for.....

I thought it just might have been that some employees simply do not give a rats...

I have read in these very forums some people in a metal working trade that give the impression that given doing it all again they would not choose metal working as a trade to make a living with... If you do not like your job, you are less likely to give a damn about it.. Especially if it is difficult to get sacked as can be the case..


I have talked with a few business owners that employ greater then 50 people and they often comment that getting decent workers can be difficult today..

I know I myself have quite a few tickets to my name, these were ones I had to have to do a job... Most of them were paid for by the employer at the time at not a small sum of money...

Most in my opinion were a complete waste of money as most followed the same process.. You went to a class room... You got told a heap of stuff 99% of which was totally irrelevant to your job, then you do a class exam, where all questions are answered as a group, then you write the answer down on the paper...

Everyone passes all the time... And you get your certificate and the employer is now covered and you have forgotten most of what was said at the training...

Originally Posted by .RC.

I grab my 240V 250amp MIG.. Crank it right up with 0.9mm wire and it simply does not seem to put the same heat into the weld that the stick does...

It can't the MIG CV power source that's flat bikky at 250 amps does not compare with the CC power source that by definition at 300 amps must be running a somewhere near a 6mm stick electrode. Comparing heat input of a 1.6 mm solid wire against that of 6mm.Simply put it takes a lot more to burn the 6mm and the heat is dissipated into the weld area.

So what would be a comparable MIG sized machined compared to a stick machine, to get the same amount of heat input into the weld and penetration.. I realize MIG has a lot more variables to choose from...

I would like to get a mig comparable to what say a 300 amp stick welder can do. Do you have 3 phase in the big shed you built. I am thinking 3 phase and am not up to speed with current models but inverter at least..

My apologies about the thread hijack -I did get a bit carried away there for a moment.

The question really about what you want your selected process to achieve.

When you are running your mig machine flat out - (spray mode) is still has a small ish wire diameter- granted you can go up to 1.2mm but for any bigger you are talking 3 phase.250 amps is about your limit and then you pay a duty cycle penalty-you have to stop to let it cool-(that info will be on your machine specs somewhere) Yes you can obtain a flux core wire (hollow flux filled tubular wire with/without gas) which is what is most used in industry for cost speed and quality but your machine will need to support that by having the ability to reverse polarity for the FCAW wire-

Note that,by changing the polarity ,wire and driver rolls but now your once mig is now a Flux core welding machine-technically not a MIG process (solid wire with gas) but again your limit is still 250 amps .


I suspect if you have a 300 amp stick welder you would running it on 3 phase and you would be running 5 or 6 mm electrodes or possibly is it a mobile tractor powered or diesel powered towed mobile unit..

So fabrication in industry uses flux cored wire....

I would have thought it would be cheaper gas process.. Flux cored wire is many $$$..

I have an AS400 welder Graeme... 400 amps DC perkins engine driven... it is old and looks like scrap, but it works..

I also have a Miller Bluestar DX welder.... Supposed to be 180 amps output DC, again engine driven.. We did measure it putting out 220 amps though with a clamp meter..

The MIG is a transmig 250SE... Separate wire feeder unit.. With a 32 amp input 250 amps is 50% duty cycle... It has an overload light on it... I assume it works, I have never had it come on...

I am not sure how to get into spray mode.... I know if I turn the volts all the way up and turn the feed down all I get is a humming sound, no crackle... Turn the feed up and it starts crackling again... I usually run Coregas 5/2 5% CO2, 2% O2 remainder argon... Although I emptied my bottle and have not yet got a refill but in the meantime I got given a half full G size bottle of BOC universal gas to empty..

Years ago I used a LN25 on an old 225 amp linc weldenpower and flux cored wire to build a 30M X 18M shed out of universal beam... I did all the welding on it, it is still standing I have read though that CC power sources with wire feeders are only good for heavy sections in the horizontal position...

I have been up very close and personal with medium sized container ships.... It is interesting seeing the welding on the hull.... Many multiple runs, looks like it was done by dave the apprentice as they go all over the place, there is no way they are robotic welded.... These ships are made in China...