Thread: Best Welder for a job - How long is a piece of string

Originally Posted by PabloP

Has anyone tried welding Ali using a CIG 170 Inverter configured for TIG. I believe that the current needed is a bit more than this welder will provide.

Any bright ideas from anyone.

I am currrently using a CIGweld 170 at work and find in very good for stick welding.A couple of weeks ago we wanted to use it in TIG mode but found that it did not have standard fittings on the machine to couple the TIG torch to it. In another department we have a CIGWELD Transarc 145iVRD which a standard torch fits no problem.
Infact we have 2 others machines at two other sites.


I own a Transarc 145i without the Voltage reduction device (VRD) which I have owned an have used it in excess of 200 hours with out any problem
The ones at work being about 2 years younger proabily have done more hours being used 7 days a week

As for using them for welding they are DC machines
Welding Ali needs AC meaning a new machine worth more than $1000

Thanks Boilermaker. I have never welded Ali, but I saw a training session somewhere that said AC was best for Ali as it gave medium penetration, but that it could be done with DC with the polarity used impacting the penetration, -ve to Tip gave high penetration and +ve to tip giving poor penetration.

I will see if there are other replies, but clearly using the 170 should not be relied on for ali work.

I think that the mob that I purchased the 170 from said that they had suitable TIG attachments for the 170, but I haven't checked that area.

Thanks again.

Originally Posted by PabloP

I saw a training session somewhere that said AC was best for Ali as it gave medium penetration, but that it could be done with DC with the polarity used impacting the penetration, -ve to Tip gave high penetration and +ve to tip giving poor penetration.

You are correct, $600 bills won't buy what they want!

I think that while you can probably get DC to work,ask yourself why industry is not doing it this way .Hey if its cheaper and better ,they would be fools not to embrace it. People claim they have done it,or can do it ,but in the end talk is cheap and its the internet, so turn the BS filter up high.

How many of these characters are posting pics of the work done in this mode? Not any, I can find .
As you undoubtedly know by now a half decent AC/DC machine is $4k and better though as I have said before the Token Tools guys has a good rep around here ,so you might have a look there.

If any of the vendors claim the welder can weld Ali on DC, ask for a demo and take pics so we can all have a look.

Regards

Grahame

Thanks again Graeme. Good to hear that I have some support for my respone to them.

Rob P.

Lots of people including myself have welded aluminum with DC electrode Negative units.

In fact sometimes it's the only way to weld very heavy aluminum plate - because of the increased heat bias into the plate.

One of the issues is weld cleanliness - and most of this can be handled by the proper and quick cleaning of the surface of the aluminum with solvents and then wire brushing off the oxide layer. By quick cleaning I mean use as short time intervals between the thorough cleaning (of small sections) and the welding - as possible.

If the issue is a cosmetic appearance on the weld - a dirty and very heavy oxide layer is a bit ugly, but a thin fresh layer of oxide is generally not much of an issue.

But contamination - of which the AC cycle only removes the oxide from the aluminium oxide - must be removed as a matter of course for structural welds and certified welds as a matter of course.

It's the very heavy oxide layer - with it's microscopic pitting - that gives "the crust" on the weld pool as the pitting is filled with crap of assorted description.


http://en.wikipedia.org/wiki/Gas_tun..._and_magnesium

Aluminum and magnesium are most often welded using alternating current, but the use of direct current is also possible, depending on the properties desired. Before welding, the work area should be cleaned and may be preheated to 175 to 200 °C (350 to 400 °F) for aluminum or to a maximum of 150 °C (300 °F) for thick magnesium workpieces to improve penetration and increase travel speed. AC current can provide a self-cleaning effect, removing the thin, refractory aluminium oxide (sapphire) layer that forms on aluminium metal within minutes of exposure to air. This oxide layer must be removed for welding to occur. When alternating current is used, pure tungsten electrodes or zirconiated tungsten electrodes are preferred over thoriated electrodes, as the latter are more likely to "spit" electrode particles across the welding arc into the weld. Blunt electrode tips are preferred, and pure argon shielding gas should be employed for thin workpieces. Introducing helium allows for greater penetration in thicker workpieces, but can make arc starting difficult.
Direct current of either polarity, positive or negative, can be used to weld aluminum and magnesium as well. Direct current with a negatively charged electrode (DCEN) allows for high penetration. Argon is commonly used as a shielding gas for DCEN welding of aluminum. Shielding gases with high helium contents are often used for higher penetration in thicker materials. Thoriated electrodes are suitable for use in DCEN welding of aluminum. Direct current with a positively charged electrode (DCEP) is used primarily for shallow welds, especially those with a joint thickness of less than 1.6 millimeters (0.06 in). A thoriated tungsten electrode is commonly used, along with a pure argon shielding gas.[23]



Welding classes - including the teaching of the advantages of welding aluminum with DC.

http://www.toolingu.com/class-650310...um-alloys.html
Arc Welding Aluminum Alloys 310

Welding Training


Class Objectives

• Describe the properties of aluminum.
• Distinguish between wrought alloy and cast alloy designations.
• Classify common aluminum alloying elements according to their weldability.
• Describe common joint designs for aluminum.
• Explain the methods used to clean aluminum.
• Explain the importance of properly preheating aluminum.
• Explain the benefits of constant current power sources for welding aluminum.
• Describe the advantages of using DC on aluminum.
• Describe the advantages of using AC on aluminum.

(the nuclear industry in 1960)

http://www.osti.gov/energycitations/...sti_id=4128511

Title COMPARISON OF AC AND DC FOR WELDING ALUMINUM-CLAD FUEL ELEMENTS

Creator/Author Hanson, G.R. Publication Date1960 Aug 26 OSTI IdentifierOSTI ID: 4128511 Report Number(s)HW-66354 DOE Contract NumberAT(45-1)-1350 Resource TypeTechnical Report Resource RelationOther Information: Orig. Receipt Date: 31-DEC-64 Research OrgGeneral Electric Co. Hanford Atomic Products Operation, Richland, Wash.

SubjectMETALS, CERAMICS, AND OTHER MATERIALS; ALUMINUM; BRAZING; CRACKS; CURRENTS; DEFECTS; ECONOMICS; FUEL CANS; FUEL ELEMENTS; HELIUM; OXIDES; TESTING; WELDING

Description/Abstract
DC welding was found to be far superior to a-c welding for aluminum- clad fuel elements. Three comparison tests were made involving 1700 fuel elements, and it was found that with d-c there was a 77% decrease in pinholes, a 34% decrease in weld cracking, and a 44% increase in braze mixing. It was also found that d-c welding solved many of the present operating problems, such as obliteration of stamping, oxides due to poor arc strikes, melting of the contour, and oxide problems resulting from a deformed electrode. In addition, the weld height was found to be much more uniform than the height of the present a-c welds. Some revisions to the present weld-inspection standards will be required since the d-c weld had a thin film of oxide at the edges of the weld. There was a 19% decrease in total weld rejects with d-c. Thus, an increase in production weld rejects is not anticipated. About 3500 fuel elements were welded using varied welding conditions, and it was found that a double pass, 25-rpm weld using helium shielding gas was optimum for d-c welding. Additional helium will be required for this weld; however, no problems are anticipated in procuring the additional helium. There will be a reduction in the operating cost with d-c, but this reduction will be offset by the cost of the increased helium consumption. Consequently, it is expected that the welding costs for d-c will be about the same as for a-c.

(auth) Country of PublicationUnited States LanguageEnglish FormatMedium: X; Size: Pages: 21 System Entry Date2008 Feb 05


This guy has a heap of his pictures welding DC Electrode Negative on Aluminum - he builds aluminium ships with DC Electrode Neg.

http://weldingweb.com/showthread.php?t=29216&page=2


This guy builds cars with them.

http://forums.hybridz.org/showthread.php?t=102856

A considerable amount of our viewers ask about welding aluminum… Do I need AC and a High Frequency box? Well, the answer is no. You can actually weld aluminum with a low cost DC power supply.


The attached picture is from this site:

http://www.locostbuilders.co.uk/view....php?tid=50458

Hammahead,

I think you may have missed the point here.

PulpoP has asked about a welder suitable for an organisation that from the face of it, do not have a background or experience in welding let alone tig welding.
My response was to to advise on a best possible outcome for Pulpo and his organisation.

There is more than just the "is this possible " questions to be considered.
There are a number of practical considerations that apply.Total costs,skill and experience ,application ,time line factors are a few

Not stated is the application.That alone could open another can of worms .ie liability. Secondly $600 is the budget.At that level, even with DC your "bang for bucks" are limited

The cut and paste does not apply to their situation as far as I can see.

Note the comments in the cut and paste about helium. Have you bought it lately? It is expensive .

Add in to the whole exercise the fluffing about trying to "tune" the set up to get acceptable /workable quality and it becomes and it can be a very frustrating and drawn out exercise perhaps for someone not yet equipped to deal with it.

I am not saying its impossible but there is not a LOT of evidence to suggest the practice is widespread. It bobs up now and again in the yank welding boards. It appears to be a cost avoidance issue more than anything.

It may suit your owns needs very well but I would suggest on the basis of limited information available that it may not suit the needs of the user as outlined in the first post.

Please don't take offence as its not my intention to get into a piddling contest with any one.

Cheers
Grahame

Grahame

Thanks all for your assistance, the feedback from each of you is equally valuable in different ways, as it has broadened my information resources enormously. I have been stick welding for 50 years, but mainly simple stuff usually mild steel AC and never had the need or opportunity to look at MIG/TIG, etc.

What I may do is get a TIG set to use on the CIG 170 and do some playing around, just to see what it can do, but my main message to those asking for a recommendation on what welder to acquire, is that $500-$600 won't get them anything much other than a 170 or equivalnt and that a Gasless MIG is unlikely to do what they want.

The links from Hammahed show what is posible and also some of the issues and so is great background that I can use if need be during my feedback.

Thanks again,