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PRACTICAL WELDING LETTER, Issue #001 -- How to Select Your Welder
September 01, 2003
We hope you will find this Letter interesting and useful. Let us know what you think of it.

Practical Issues, Creative Solutions
How to select your Welder.

This publication brings to the readers practical answers
to welding problems in an informal setting designed to be
helpful and informative. We actively seek feedback to make
it ever more useful and up to date. We encourage you to
comment and to contribute your experience, if you think
it may be useful to your fellow readers.

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Date: September 2003 - Practical Welding Letter - Issue No. 01

------------------------TABLE of CONTENTS------------------------

==> 1 - Introduction

==> 2 - Article: How to select your welder

==> 3 - How to do it well: Brazing Fittings

==> 4 - Filler Metal: Understanding AWS Classification

==> 5 - In the news: Recent Welding Articles

==> 6 - Terms and Definitions Reminder

==> 7 - Site Updating

==> 8 - Work in Progress

==> 9 - Readers' Contributions

==> 10 - Explorations: beyond the Welder

==> 11 - Correspondence: a few Comments

==> 12 - Bulletin Board

==>Unsubscribe link

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1 - INTRODUCTION

Welcome to the first issue of our Practical Welding Letter,
which we plan to publish regularly once per month.

We will try to concentrate on Practical aspects of the exciting
World of Welding, and provide useful information to our readers.

The Welding Wide World is brisk with new developments
and new applications: it stands out as a lively working place.
The importance of its contributions to Industry and Economy
cannot be overstated.

There is a place also for the individual and the small shop who
may not have ready and easy access to information and testing
facilities which are the normal working tools of Corporations.

We would like to cater to the interests and needs of these welding
people who normally are highly motivated and efficient, by providing
whatever help and directions they may need to realize their goals.

It will not take long to the alert reader to discover that our
attitude is quite conservative, and that we encourage learning and
practicing before jumping to rash decisions relative to selecting
processes and purchasing equipment. Other people may think in
different terms, but we believe this to be the right way to go.

We would greatly appreciate the feedback of whoever would like
to contribute his/her thoughts on the subjects exposed here,
for this would help us to produce a more focused publication.

To do that, just drop us a line, click here.

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2 - How to select Your Welder

A few letters asked us advice for selecting the most appropriate welder.
This subject looks surrounded with some mistery:
readers seem to prefer that somebody else take a decision.
One must remember that there will not be a single piece of
equipment capable of meeting the needs of every job.

Instead of aiming for a universal welder with all capabilities
included, it makes more sense to look for the bulk of work,
and keep out those rare and less important cases that shall need
individual attention outside the present acquisition.

In this article we shall deal with the most popular processes:
Shielded Metal Arc Welding (SMAW) known as stick welding,
and Gas Tungsten Arc Welding (GTAW) also known as Tig
(Tungsten Inert Gas).
Both processes can use the same power supply.

In a further issue we will deal with equipment for other processes.

The problem is not difficult in general, but it requires
1 - knowing for which purpose one needs a welder or
2 - deciding which option should be adopted.

One should not discount the help one can get from sales reps of
manufacturers: but their aims are different, and they may try to
push their more expensive equipment, even if it is not the most
appropriate decision for the customer. To get their best advice
one must know exactly what one wants and needs.

Furthermore one should either know or decide on the following:

  1. Materials:
    • For GTAW, Aluminum and Magnesium require Alternating
      Current (AC) possibly with superposed High Frequency
      stabilizing current.
      SMAW should not be attempted for these materials.
    • All other usual materials: carbon and low alloy steels,
      stainless steels, heat-resisting alloys by both
      processes (SMAW & GTAW) use AC or Direct Current (DC)
      with the polarity dictated by the electrode cover (SMAW)
      and other needs like penetration.

  2. Range of thicknesses to weld in one pass:
    Note: Selecting this option will establish the range of
    Current (in Amperes) required.
    • (SMAW) One popular rule of thumb indicates that the
      number of amperes should be equal to the number of
      thousands of inch of the base metal thickness.
      Thicker material can be welded with more passes.
      Some power supplies request duty cycle of a given percentage
      (say 30%) at certain current levels.
      (This means continuous work for 3 minutes
      and 7 minutes of idling while equipment cools down).
      Note: This process is not applicable to very thin
      sheet or tube (18 gauge = 1.2 mm or thinner).

    • (GTAW) In this process the current employed is relative
      to the type and diameter of the tungsten electrode
      selected. These data are published in AWS 5.12.
      The actual electrode preferred for each thickness
      is a matter of individual experience and skill.

    See the following Table as a partial guide:

    Table
    Current in Amps relative to Electrode Size
    Electrode Dia. Tungsten Electrodes
    inchesmmStandardThoriated
    0.041.010 - 60 15 - 80
    1/161.650 - 100 70 - 150
    3/322.4100 - 160 140 - 235
    1/83.2150 - 210 225 - 325

  3. Positions
    Note: Welding is easiest in the flat position.
    Next comes the horizontal position, where the weld bead
    is horizontal on a vertical wall.

    • SMAW is appreciated for its ability to perform in all
      positions including overhead. This requires special
      skills on the welder's part and may reduce weld
      deposition rate and speed.

    • Also GTAW can be performed in all positions. Furthermore
      it permits welding of quite thin material. Argon gas
      is fit for aluminum, steel, stainless steel and other
      materials. High quality good looking beads are produced.

  4. Productivity needs

    • Do not forget in the calculation the allowed duty cycle,
      that is the percentage of cooling down time for the power supply,
      for every current level to be used, in any ten minutes interval.

    • Both SMAW and GTAW are versatile manual processes
      capable of high quality results. Productivity however
      is reduced by the intrinsic process limitations.

    • When productivity must be increased, other processes
      (like GMAW, FCAW or SAW) might be more attractive.
      Once the quality requirements are taken care of,
      the economics of the operation will prevail for
      process selection and implementation.

  5. Type of work

    • SMAW can be used indoors and outdoors because light
      drafts will not interfere.

    • GMAW however depends on the continuous shielding
      provided by the inert gas (argon): outdoors work
      would require complex protection from winds.

  6. Fixed or movable location

    • Weight and bulk of equipment should be considered
      if resetting is frequently required, otherwise
      it is of no consequence.

  7. Future expansion

    • Adding capability, like current type and maximum current
      carrying capacity, wave form control etc. to equipment
      specification can be an expensive proposition if there
      is little chance to use and exploit the additional features.

    • A conservative approach would suggest to care only for
      the work at hand, and provide for expanded capability
      later, when a real need reveals itself.

  8. Skill and experience

    • There is no alternative to training and gaining
      experience.
    • A modern piece of equipment cannot make up for lack of
      experience: it may even complicate the issue by
      generating frustration and obscuring the real causes
      of troubles.

  9. Budget available

    • The economic consideration should always prevail.
    • In any case the welder should be convinced that his/her
      selection is the most efficient for the intended use.
    • Therefore it seems that before committing to any expense
      the welder should make sure that the selection is right.
    • Ask the supplier where you can see the proposed equipment
      in action. Go there and inquire if it is good for you.
    • Get permission to practice hands on. Try to obtain it
      for a trial period (say two weeks) before buying.
      Look for used and reconditioned equipment.
      See if you can lease it for a period before purchasing.
    • Do not let anybody push you before you have proved that
      it meets your requirements.
    • Purchase only what fits you for the work you need now.

    Now to the point

    Normally both SMAW and GTAW are operated with a drooping,
    constant current power source.

    Obviously a larger current capability and wave form manipulation
    and control are available with more expensive equipment.
    Power sources of the following categories are arranged in order
    of increasing price.

    • For Home and Hobby work the simplest one phase AC transformer
      with output from 20 to 170 Amps is generally suitable for
      common uses, not too thin, although this type do not include
      wave output control.

    • For more demanding light industrial use, a combined power supply
      of AC and DC of about the same output, up to less than
      200 Amps, with constant current characteristic but with adjusted
      wave shape control and fixed balance control between time with
      Electrode Negative (EN) for deeper penetration and Electrode
      Positive for cathodic cleaning action and shallow, wide bead,
      and with High Frequency for easy starts and arc stabilization.

    • Industrial use may demand higher current output up to 250 or
      350 or 500 Amps and may offer adjustable balance control.

    • Most advanced power supplies are currently those based on
      Inverter technology, that permits to the experienced welder
      to best adapt the output to the application requirements.
      Besides larger range balance control, claimed to increase
      travel speed and deposition rate, inverters offer output
      frequency adjustable in the range 20 to 250 Hz (as opposed
      to fixed 60 or 50 Hz of simple transformers) claimed to
      change the bead shape at will (the lower the frequency
      the wider the bead, the higher the frequency the narrower
      the weld bead).

    Accessories

    For SMAW only a pair of cables are needed (one connected
    to the electrode holder, the other to the ground clamp), apart from the
    usual welder's tools like hammer for slag removal and wire brush
    and protection gear (hat, helmet, gloves, apron, boots etc.)

    Torches for GTAW provide electric current for striking and
    keeping the arc and supply the protecting inert gas to the weld.
    Air cooling is sufficient for low currents. Above 200 Amp
    torches are water cooled. A switch is provided for starting
    gas flow and High Frequency current. When switching off the arc,
    the gas flow is maintained for a while till the weld cools down.

    Conclusion

    This presentation comes to an end. It is understood that it
    is only a guideline and that other questions may appear.
    We would like to suggest that every welder should try to
    obtain practical hands on test time before committing to
    a purchase, as indicated above.

    We will welcome your feedback and suggestions to be published
    in next issues if judged of value to other readers.

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    3 - How to do it well: Brazing Fittings

    Q: During torch brazing of a fitting onto a steel tube, it was found
    that the silver alloy filler covered the surface only in part, making the joint unacceptable. How can we improve?
    A: First, the clearance between the elements should be correct,
    between 0.05 and 0.10 mm (0.002" and 0.004") on the side.
    Second, both surfaces must be absolutely clean from dirt, paint,
    rust and oil or grease even when a flux is used.
    Third, rotating gently one element relative to the other for
    a quarter of a turn to the right (or to the left) and back while the braze is still liquid will most probably improve the results.

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    4 - Understanding AWS Classification of Welding Electrodes.

    The Classification of Electrodes (sticks) for Shielded Metal Arc Welding (SMAW) as established by AWS (American Welding Society) and adopted by industry at large,is used to identify the filler metal required in any given job.
    Here we shall present the data for low carbon steel.

    Standard diameters of the metal range from 1/16" to 5/16" and lengths are 9" to 18", with a bare length of 3/4" to 1-1/4" protruding from the shield coating, for making contact with the electrode holder.
    Electrodes are sold packaged in metal or cardboard boxes.

    The letter E indicates electrodes, and is followed by four or five digits the first two or three of which indicate the minimum tensile strength expressed in thousand pounds per square inch (psi) of deposited metal in as welded condition.

    The next to last digit is either 1, for all position welding or 2, for flat or horizontal position only. The last digit indicates the type of covering and the current to use.
    As the next to last digit modifies sometimes the meaning of the last digit, it is customary to present the Table with the last two digits.

    Table
    Last two digitsType of coveringType of current
    10High cellulose, sodiumDCRP
    11High cellulose, potassiumAC or DCRP
    12High titania, sodiumAC or DCSP
    13High titania, potassiumAC or DC
    14Iron powder, titaniaAC or DC
    15Low hydrogen, sodiumDCRP
    16Low hydrogen, potassiumAC or DCRP
    18Iron powder, low hydrogenAC or DCRP
    20High iron oxideAC or DC (1)
    22High titania, sodiumAC or DCSP
    24Iron powder, titaniaAC or DC
    27Iron powder, iron oxideAC or DC (1)
    28Iron powder, low hydrogenAC or DCRP
    (1) Either polarity for flat welds, DCSP for horizontal welds.
    DC = Direct Current, Either Polarity
    DCSP = Direct Current, Straight Polarity (Electrode Negative)
    DCRP = Direct Current, Reverse Polarity (Electrode Positive)
    AC = Alternating Current

    While Electrodes designated for AC can be used also with DC, the opposite is not true: DC electrodes must be used with DC only.
    E6010 and E6011 are popular selections, providing deep penetration and good mechanical properties.
    E6012 and E6013 provide medium penetrating arc and permit welding
    even with poor fit up.
    E6020 can be welded only in flat or horizontal position, provide medium to heavy penetration and permit high deposition rate.
    Low Hydrogen electrodes should be always kept free of moisture,
    and baked when necessary if exposed to the atmosphere;
    they are used to prevent cracking in hard to weld steels.

    The document dealing with this matter is:
    AWS A5.1 - SPECIFICATION FOR CARBON STEEL ELECTRODES
    FOR SHIELDED METAL ARC WELDING

    Is this article helpful? Let us have your comments by e- mail. Click here.

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    5 - In the news: Recent Welding and Cutting Articles

    Reference to articles on welding and cutting subjects.

    Notes: - The following links, that were active when this publication was released, are no longer supported by AWS.
    You may be able to find the articles through their title and the date of their publication in the Welding Journal of August 2003.

    News from AWS:

    ...precision laser cutting of special steel plates up to 16 mm (0.63 in) thick.

    ...Lasers and solid wire filler metal repair turbine blades.

    ...2 kW Laser assisted oxygen system cuts up to 3" (75 mm) and
    potentially up to 4" (100 mm) steel plates in a fraction of time.

    News from TWI:

    ...hybrid laser/gas metal arc welding for pipelines.
    The article was unfortunately removed.
    It may still be available by searching the TWI site.
    Note: TWI requests a subscription without charge before opening its articles to the public.

    News from Newport News:

    ...The Welding School of Northrop Grumman Corporation received
    an award from the American Society for Training and Development.
    Read article by clicking here.

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    6 - Terms and Definitions Reminder

    Do you remember what is meant by...

    Forehand Welding?
    It is a term used in oxy-acetylene welding for indicating a technique
    consisting in directing the flame away from the deposited weld.
    This produces important heating of the base metal and a greater proportion is melted.
    This technique is usually preferred for welding thin sheets. Its opposite, called

    Backhand welding
    means the technique directing the flame against the weld just deposited.
    Usually there is less melting of the edges of the joint and better retention
    of chemistry and properties of the filler rod. Cooling of weld is slower.
    Those preferring this technique affirm that it permits saving of time
    and consumables, even for beveled joints.

    And what about...

    Keyhole technique?

    It is a term used to indicate the piercing of a hole
    through the thickness of the work by the heat source at joint edges.
    Moving the heat source along the joint permits the molten metal to fill the hole.
    Used generally for intense heat sources like Plasma Arc, Electron Beam Welding and
    Laser Beam Welding, this technique finds an application in a much less
    energy intensive process, like oxyacetylene welding in the particular situations of
    Vertical Up or overhead welding. Welder's skill is here of utmost importance.

    Would you want other terms being presented in next issues?
    Let us have your feedback by sending your e-mail. Click here.

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    7 - Site Updating

    We are continuing to review and add new pages on the Site:
    recently we added a page on Magnesium welding, and we are preparing a bunch of new pages where we want to deal in detail with welding of Carbon steels, of High Alloy Steels and of Tool Steels.

    We want to add the subject of Braze-Welding as soon as possible.
    Other subjects are too far down the line to be mentioned here.
    And we plan also to add a page About Us, to come closer to our readers and to let them better know us.

    If you would like a particular subject to be presented in the Site just let us know: drop us a line by e-mail: click here.

    This is to say that any time you go back to the Site you may find
    new information added: click here.

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    8 - Work in Progress

    We want to pay attention to readers' comments and feedback in future issues of Practical Welding Letter and we will do our best to make it more helpful and interesting.
    We will present more articles on Selection of Welders, to cover other processes, and new items as they come to our attention.
    We will report on recent updates of the Site.

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    9 - Readers' Contributions

    We would welcome contributions of our readers with articles of general interest.
    In particular, personal experiences may be interesting to a larger public.
    We must reserve the right of accepting, editing or rejecting readers' writings, in order to keep control on the level and integrity of the publication but we feel that the voice of the practical welder should be heard and listened to.

    So you are invited to contribute with your thoughts and experience, by e-mail: click here.

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    10 - Explorations: beyond the Welder.

    We would like to recommend a few Sites of general interest that might take you over to new horizons, in unlimited Exploration trips,
    for discoveries, learning and pleasure.

    The excellent Site of Scientific American can be browsed by clicking here.

    To see another very interesting Site, that of NASA, with subjects appealing to many people click here.

    For the curious and the adventurous person, see what the Site of SBI has to offer to anyone ready to take the plunge in the Internet. Click here

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    11 - Correspondence: a few Comments

    We are glad to report that many people use the links provided
    in the Site for submitting us the most diverse questions.

    It is encouraging to see a growing number of interested browsers
    who are ready to check if any good could come to them
    from a direct question to somebody hitherto completely unknown.

    We welcome all questions and will do our best to provide useful and practical answers.

    This said we must stress that we seldom find all the basic data
    in the messages we receive.
    Either they are considered not important, or they are not known,
    or they are simply forgotten.
    It must be understood however that we cannot guess
    the real situation if we are not given all relevant data on
    materials, condition, welding process, parameters etc.

    A few questions are clearly school assignments:
    nothing wrong with that except that we would like to see a short note to this effect.
    It would be easier for us to address the inquirer to pertinent literature to be studied.

    Other questions are part of cloudy development projects whose details must be kept secret lest somebody might steel the idea:
    it is very difficult to provide practical advice when the purpose of the development is not enounced.

    A very frank reader complained that while looking in the Site
    for advice on which equipment to buy, he came out more confused then helped. (He did not however clearly state his needs):
    I am indebted to this reader for the decision to include in this issue
    the article on How to Select Your Welder. I hope this makes clear that a number of decisions must be taken before operating the selection.

    We would gladly publish questions and answer of general interest
    but it seems that up to now our readers have very specific questions: that may change, though.

    Keep on asking, we all are learning.

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    12 - Bulletin Board

    12.1 - A few readers sent us attachments to their messages.
    We must inform you all that, as a matter of policy and of self protection, we will not open attachments at all.
    It might be too dangerous.
    So you are invited to append your photo or sketch
    at the end of your message and avoid sending attachments.

    12.2 - We would like to inform you that we will be unable
    to respond quickly to all questions submitted during the third week of September 2003 because of a brief absence for personal reasons.
    All messages will be answered the following week.

    12.3 - We would like to let you know that we know and use an exceptional facility prepared to let anybody with no previous experience, build a successful Site
    on the Internet. We recommend it because it works. See for yourself. Click here.

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    Visit the Welding Advisers Site at
    http://www.welding-advisers.com/
    and browse the several updated pages
    Covering Welding Processes, Equipment, Materials,
    Jobs and Careers, Quality, Safety and Related
    Processes/Applications.
    Free Subscription and Download. Questions welcomed.
    Contact us at questions@welding-advisers.com.

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    Copyright © 2003, by Elia E. Levi and welding-advisers.com, all rights reserved

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