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In This Issue

1  Seasons Greetings
2  Gases for Hardfacing
3  Welding AR Plate with Postalloy® 3044 FCG
4  Humor: Memorable T-Shirts
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Seasons Greetings

I wanted to publish this newsletter prior to the Holidays, but just couldn't seem to get it done. But I am determined to publish before the year end. To all of you on behalf of all the Postle staff and employees, we want to wish you Seasons Greetings and a very Happy and Prosperous New Year.
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Gases for Hardfacing

In the last issue we discussed the role of Polarity as it pertains to Hardfacing, and it only seems fitting that we discuss the next important arc variable, welding gas.

We don't normally think of air as a conductor of electricity, but if you think about lightning strikes from thunder clouds it becomes a little more apparent. Air, does in fact conduct electricity. Sure it is not as good as copper, gold or silver, but it does conduct under the right conditions. All it takes is a voltage difference between two opposing poles in close proximity to one another. Of course, you say, this is how we weld. In fact you are right. The voltage drop across the electrode and work ionizes the air between them, and current flows, melting the electrode and work piece. So what is Ionization? It is simply the stripping off of electrons of the gas between the poles, and once we have stripped electrons, current flows. The ease at which ionization occurs in gases is known as the Ionization Potential. The lower the Ionization Potential, the easier current flows. Ranking of the common welding gases are as follows:

Note that Oxygen and Nitrogen, which are the major constituents have quite low Ionization Potentials. Argon is quite high and CO2 is quite low. These numbers are presented here only as a guideline, because things change dramatically when you consider the actual space between the electrodes. In reality, the space is filled with metal vapors, flux and other ingredients, all of which have their own Ionization potentials. So the actual Ionization Potential of the space between the electrodes is a combination of all the elements and not just the shielding gas being used. Also, some elements added to the wire fill actually produce their own gases, like Carbon, that make CO or CO2. I know it is getting to sound a little complicated, but we can make some generalizations about the shielding gases we use for hardfacing.

First, let's keep in mind that unlike joining applications, hardfacing wires like a globular or ball transfer, not a spray transfer. Globular transfers promote low dilution..... a good thing for hardfacing. An active gas like CO2 promotes a globular transfer and is a good choice for hardfacing applications. It's main drawback is a harsh arc and spatter. It has deep penetration characteristics but may be desirable in applications with thick sections, large heat sinks and fast travel speeds. Pure Argon also produces a harsh arc, and spatter can sometimes be troublesome, but dilution is low while bead shape is better than CO2 deposits. Additions of Oxygen to Argon tend to smooth out the arc, produce less spatter and wet the base metal better. Oxygen additions of 2,5, and 10% are acceptable, but there will no doubt be a change in welding parameters. Oxygen additions also lower the amperage at which a spray transfer occurs, so you must readjust parameters to compensate. Oxygen additions may also produce porosity on occasion, because the Oxygen forms Oxides and robs the deposit of deoxidizes. Argon/Oxygen deposits sometimes have a slight Oxide surface which may be undesirable in certain applications. CO2 can also be added to Argon and have somewhat the same affect on arc stability and bead shape. The main drawback of CO2 additions is the production of spatter. It is usually higher than with Oxygen mixtures to Argon. 75% AR/25% CO2 is a common gas and works well with hardfacing wires.

To summarize, the choice of gas is usually recommended by the manufacturer, but it is often a matter of personal preference, the type of deposit desired, and the application. My personal preferences in order are (most desirable first):

Argon/Oxygen - 2,5 &10% additions of Oxygen to Argon promote clean, spatter free deposits, with good wetting action and excellent bead shape. The heat of this gas also helps keep interpass temperatures up where they should be. Spray transfer is possible with some wires if so desired.

Argon/CO2 - 75% AR, 25% CO2 is a popular mixture. The addition of CO2 cools the weld slightly, produces more spatter than the Oxygen versions, as stated above, but does produce a deposit with a good bead shape and wetting characteristics. Spray transfer is possible if desired.

Argon - Pure Argon produces a rough arc with some spatter. It is hot, which helps with interpass temperatures. Dilution is low and wetting action is sometimes compromised. Spray transfer is possible if desired.

CO2 - Good penetration when needed, spatter is high, and bead shape is good. Probably the least expensive of the gases used for hardfacing.

No discussion on gases for hardfacing is complete without mentioning Air or Open Arc wires. These wires can be run without any shielding gas at all. Enough deoxidizers as well as a slag system is generally employed to produce porosity free deposits. The metal transfer is globular and occasionally quasi-spray. You can run these wires with a shielding gas, but keep in mind that because Oxygen is eliminated from the arc, slags and other attributes may not be realized in the final deposit. Metal transfer may also be compromised. There are some exceptions however, the Chromium Carbide family has no slag system to speak of and the addition of shielding gas has little affect on these wires. Always check with the manufacturer before using a shielding gas with an Open Arc wire.

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Welding AR Plate with Postalloy® 3044 FCG

I am often asked what to use to attach or join AR Plate. You ask, "What is AR Plate?". AR Plate is a through hardened plate that is typically used to combat abrasive wear. AR is an abbreviation for Abrasion Resistant, and is usually followed by a three digit number such as 400, 450, or 500. The three digit number stands for the nominal Brinell Hardness number. Therefore, AR 400 is a through hardened Abrasive Resistant plate having a hardness of 400 Brinell. The high hardness values usually throws people off regarding joining products, but it really is quite straight forward. Most AR plates are low in Carbon, which makes welding them a breeze. You could use something as simple as a 70,000 psi tensile strength product, but that is really too light. You really need something with more strength, like 1/16" or .045" diameter Postalloy® 3044 FCG. The high tensile strength (106,000 psi) and good ductility (35% Elongation) makes it ideal for high strength joining. Not only is it good for attaching and joining AR Plate, it is an excellent choice for repairing buckets, chutes, undercarriage parts, etc. All except Manganese steels. For that, consider Postalloy® 285 SPL or Postalloy® 2850 SPL. Whenever mild steel electrodes or wires aren't enough, choose Postalloy® 3044 FCG . Check out the data sheet below.

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The following T-Shirts were apparently observed in Maryland's Ocean City. This is one of the annual Washington Posts publishings.

1. I CHILD PROOFED MY HOUSE, BUT THEY STILL GET IN.

2. (On the front) 60 IS NOT OLD. (On the back) IF YOU'RE A TREE.

3. AT MY AGE, "GETTING LUCKY" MEANS FINDING MY CAR IN THE PARKING LOT.

5. MY REALITY CHECK JUST BOUNCED.

6. LIFE IS SHORT. MAKE FUN OF IT.

7. I'M NOT 50. I'M $49.95 PLUS TAX.

8. PHYSICALLY PFFFFFT!

9. IT'S MY CAT'S WORLD. I'M JUST HERE TO OPEN CANS.

10. EARTH IS THE INSANE ASYLUM OF THE UNIVERSE.

11. KEEP STARING....I MAY DO A TRICK.

12. WE GOT RID OF THE KIDS. THE CAT WAS ALLERGIC.

13. DANGEROUSLY UNDER-MEDICATED.

14. MY MIND WORKS LIKE LIGHTNING. ONE BRILLIANT FLASH AND
IT'S GONE.

15. LIVE YOUR LIFE SO THAT WHEN YOU DIE, THE PREACHER WON'T HAVE TO TELL LIES AT YOUR FUNERAL.

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