Hey Al!

Good of you to ask these questions...

1.) "As the AISI number goes up, is it true that the alloy content, i.e., chrome and nickel increase as well?"

Answer: Not necessarily... In fact the percentages fluctuates as one follows the Cr % Ni contents, and follows the chart as the AISI numbers go up specifically for the various stainless steel grades... Here's an example (Even though I'm using an SAE Chart the only difference between AISI & SAE is the AISI numbers usually have prefix letter indicate the steel making process used to manufacture the number grade otherwis they are the same system.):

SAE      UNS      % Cr    % Ni       % C         % Mn       % Si   % P    % S   % N            Other

201     S20100   16–18   3.5–5.5   0.15      5.5–7.5        0.75   0.06   0.03   0.25           -
202     S20200   17–19     4–6      0.15      7.5–10.0       0.75   0.06   0.03   0.25           -
205   S20500    16.5–18 1–1.75  0.12–0.25   14–15.5      0.75   0.06   0.03   0.32–0.40   -
254[8] S31254   20        18         0.02 max       -            -       -        -      0.20          6 Mo; 0.75 Cu; "Super austenitic"; All values nominal
301     S30100   16–18   6–8        0.15          2             0.75  0.045   0.03      -             -
302     S30200   17–19   8–10      0.15          2             0.75   0.045   0.03    0.1            -
302B   S30215    17–19  8–10       0.15          2         2.0–3.0  0.045   0.03      -             -
303    S30300   17–19   8–10       0.15          2             1       0.2      0.15 min  -           Mo 0.60 (optional)
303Se  S30323  17–19   8–10       0.15          2            1        0.2      0.06      -            0.15 Se min
304    S30400   18–20   8–10.50   0.08          2           0.75     0.045   0.03     0.1           -
304L   S30403   18–20   8–12       0.03          2           0.75     0.045   0.03     0.1           -
304Cu S30430   17–19   8–10       0.08          2           0.75     0.045   0.03      -            3–4 Cu
304N  S30451   18–20   8–10.50   0.08           2           0.75     0.045   0.03   0.10–0.16   -
305   S30500    17–19   10.50–13  0.12          2           0.75     0.045   0.03      -            -
308   S30800    19–21    10–12     0.08           2           1         0.045   0.03     -            -
309   S30900    22–24   12–15      0.2            2            1        0.045   0.03      -            -
309S  S30908   22–24   12–15      0.08           2           1         0.045   0.03      -            -
310   S31000    24–26   19–22      0.25           2           1.5      0.045   0.03      -            -
310S  S31008   24–26   19–22      0.08           2           1.5      0.045    0.03      -           -
314   S31400    23–26   19–22      0.25           2        1.5–3.0   0.045    0.03      -           -
316   S31600    16–18    10–14     0.08           2          0.75      0.045   0.03   0.10          2.0–3.0 Mo
316L  S31603   16–18   10–14      0.03            2          0.75      0.045   0.03   0.10          2.0–3.0 Mo
316F  S31620   16–18   10–14      0.08            2           1          0.2    0.10 min   -           1.75–2.50 Mo
316N  S31651   16–18   10–14     0.08             2           0.75     0.045   0.03   0.10–0.16   2.0–3.0 Mo
317   S31700    18–20   11–15     0.08             2           0.75     0.045   0.03   0.10 max     3.0–4.0 Mo
317L  S31703   18–20   11–15      0.03            2            0.75     0.045   0.03   0.10 max     3.0–4.0 Mo
321   S32100    17–19   9–12       0.08            2            0.75     0.045   0.03   0.10 max     Ti 5(C+N) min, 0.70 max
329   S32900    23–28   2.5–5      0.08            2            0.75      0.04    0.03      -            1–2 Mo
330   N08330    17–20   34–37     0.08             2        0.75–1.50   0.04   0.03      -                -
347   S34700    17–19   9–13       0.08            2            0.75      0.045   0.030    -            Nb + Ta, 10 x C min, 1 max
348   S34800    17–19   9–13       0.08            2            0.75      0.045   0.030    -            Nb + Ta, 10 x C min, 1 max, but 0.10 Ta max; 0.20 Ca
384   S38400    15–17   17–19     0.08             2            1          0.045   0.03     -                -
Ferritic
405   S40500    11.5–14.5   -       0.08            1            1           0.04    0.03       -            0.1–0.3 Al, 0.60 max
409   S40900   10.5–11.75  0.05   0.08            1            1          0.045    0.03      -           Ti 6 x C, but 0.75 max
429   S42900   14–16         0.75   0.12            1            1          0.04      0.03      -                -
430   S43000   16–18         0.75   0.12            1            1          0.04      0.03      -                -
430F  S43020   16–18          -      0.12          1.25          1          0.06   0.15 min   -            0.60 Mo (optional)
430FSe S43023 16–18          -     0.12           1.25         1          0.06      0.06       -            0.15 Se min
434   S43400   16–18           -     0.12            1             1          0.04     0.03       -            0.75–1.25 Mo
436   S43600   16–18           -     0.12            1             1          0.04     0.03       -            0.75–1.25 Mo; Nb+Ta 5 x C min, 0.70 max
442   S44200   18–23           -     0.2              1            1           0.04     0.03       -                -
446   S44600   23–27       0.25     0.2            1.5           1           0.04     0.03       -                -

Martensitic         % Cr         % Ni       % C         % Mn       % Si     % P     % S       % N            Other

403   S40300   11.5–13.0       0.60       0.15          1             0.5    0.04    0.03         -                 -
410   S41000   11.5–13.5       0.75       0.15          1               1     0.04    0.03         -                 -
414   S41400   11.5–13.5   1.25–2.50    0.15          1              1     0.04    0.03          -                 -
416   S41600   12–14              -          0.15        1.25            1     0.06   0.15 min     -           0.060 Mo (optional)
416Se S41623  12–14             -           0.15        1.25            1     0.06   0.06          -           0.15 Se min
420    S42000  12–14              -        0.15 min      1               1     0.04   0.03          -                 -
420F  S42020   12–14             -        0.15 min     1.25            1     0.06   0.15 min     -           0.60 Mo max (optional)
422   S42200   11.0–12.5   0.50–1.0   0.20–0.25   0.5–1.0       0.5   0.025   0.025        -           0.90–1.25 Mo; 0.20–0.30 V; 0.90–1.25 W
431   S41623   15–17       1.25–2.50     0.2           1               1     0.04   0.03           -                 -
440A   S44002  16–18             -        0.60–0.75    1               1     0.04   0.03           -           0.75 Mo
440B   S44003  16–18             -        0.75–0.95    1               1     0.04   0.03           -           0.75 Mo
440C   S44004  16–18             -        0.95–1.20    1               1     0.04   0.03           -           0.75 Mo
Heat resisting
501   S50100      4–6              -         0.10 min     1               1     0.04   0.03           -           0.40–0.65 Mo
502   S50200      4–6              -          0.1           1               1     0.04   0.03           -           0.40–0.65 Mo
Duplex
2205[8]  S31803
S32205              22               5          0.03 max    -               -       -       -            0.15        3 Mo; All values nominal
Super duplex
2507[8] S32750   25               7          0.03 max    -               -       -       -            0.28        4 Mo; All values nominal

Refer to these links for reference:
http://en.wikipedia.org/wiki/AISI_steel_grades 
http://www.brazing.com/products/Weld_Stainless/chem_composition.asp
http://www.engineersedge.com/stainless_steel.htm 
http://chemistry.about.com/gi/dynamic/offsite.htm?site=http://www.hghouston.com/ssdata.html
http://www.ssina.com/view_a_file/designguidelines.pdf

2.) "Cr + Ni is higher for 308 than 304, Cr + Ni for 312 is higher than for 308, 316 higher than 312, 321 higher than 316, 347 higher than 321 and so on...True or False?"

Answer: False! Reason: Refer to chart and some of the reference links above.

3.) "The easiest way to tell if a base metal is ferrous or nonferrous is to apply a magnet to the metal. If it sticks, the base metal is ferrous. If it doesn't stick, the base metal is nonferrous... True or False?"

Answer: False... Reason: There is not a simple answer in determining whether a base metal is magnetic or nonmagnetic especially when referring to certain alloys that do have a certain percentage of Iron or Nickel as part of their composition...

For a metal (or any other substance) to be magnetic, it must have electron spin. This gives the substance an electronic angular momentum to interact with the magnetic field. Some metals, like the lanthanides, consistently have unpaired electrons due to the Pauli Exclusion Principle, and so are typically strongly magnetic. But other metals may be magnetic or not magnetic depending upon what substance they are found.

Alloys made of nominally magnetic metals such as Fe and Ni may become non-magnetic in certain alloys grouped together as "stainless steel". In addition, the term "magnetic" is not very precise. Some substances become "magnetic" in the presence of a magnetic field, but are not magnetic in the absence of a magnetic field. These are called "paramagnetic".

Other substances form "permanent" magnets and have their own intrinsic magnetic field. These are called "ferromagnetic" materials because iron metal is the "typical" example. Yet other substances have a structure in which some of the electrons point in one direction and another layer of domain point in the opposite direction.

These more complex structures are called "antiferromagnetic". A further complication is that the magnetic behavior depends upon the temperature. So at low temperature a substance may have one kind of magnetic properties but at a higher temperature may have another type of magnetic behavior.

The bottom line is that the magnetic properties of a substance is complicated, and it is hard to assign metals as being strictly magnetic and others to be strictly non-magnetic.certain grades of stainless steels can be either paramagnetic, ferromagnetic, or antiferromagnetic and it depends as to whether or not they are ferrous or nonferrous. I say this because no matter what type of grade stainless we are talking about ,there is always a certain amount of Iron in it's chemical composition.. Hence the word steel which is iron and carbon so, stainless steels no matter which grade always have those two elements as well as others which can influence them to behave similar to true nonferrous metal alloys that would not contain any elements such as: Iron, Nickel, Cobalt, Gadolinium, Dyprosium in their chemical compositions...

As for whether they are magnetic, the answer is that it depends. There are several families of stainless steels with different physical properties. A basic stainless steel has a 'ferritic' structure and is magnetic. These are formed from the addition of chromium and can be hardened through the addition of carbon (making them 'martensitic') and are often used in cutlery. However, the most common stainless steels are 'austenitic' - these have a higher chromium content and nickel is also added. It is the nickel which modifies the physical structure of the steel and makes it non-magnetic... Does it depend on the amount of chromium, or nickel alloy? The answer is yes, the magnetic properties of stainless steel are very dependent on the elements added into the alloy, and specifically the addition of nickel can change the structure from magnetic to non-magnetic.

In summary, the easiest way to determine whether or not a base metal is ferrous, or nonferrous is to study the specific base metal's chemical composition... That is - if it's available. ;) Remember that certain Nickel alloys may not even have any Iron in it's chemical composition and yet, if a magnet is used to verify that it is nonferrous and the individual doesn't know that Nickel is also has ferromagnetic properties althoug the person is unaware of this, then the individual will certainly scratch their heads when they notice the reaction of placing a magnet to the base metal and watching it stick!!! So know the elements in the chemical compositions and determine whether or not their certain chemicals that may or may not have certain magnetic propertiesand finally, it can sometimes also depend on the type, size and strength of the magnet one is using. :) :) :)

4.) "One easy way to reclaim a low hydrogen electrode that has been exposed to humidity is to short it out against the workpiese and heat it up to drive out the moisture.
True or False?"

Answer: False... Reason: The moisture is absorbed from the atmosphere by the flux coating surrounding the filler metal grade in the core so, one would have to heat up the electrode hot enough to ensure that the flux coating is "baked enough" via the method mentioned in the original question which would then cause the flux coating to dry up unevenly and shrink in size causing the coating to crack and fall off thereby exposing the filler metal core to the atmosphere which could then attract moisture to condensate on the surface of the filler metal core!!! So this method of attempting to "cook' any moisture/humidity via shorting it out against the workpiece and heat it up to drive out the moisture would cause more humidity to come in contact with the exposed filler metal core as a result in attempting this foolhardy technique!!! :( ;) :)

5.) "And the last one of the day: Before welding thick steel, it should be heated to drive the moisture out of the pores!!! True or False?"

Answer: TOTALLY AND WHOLEHEARTEDLY FALSE!!! Reason: There are no pores in thick or thin steel - PERIOD!!! The moisture is a result of condensation on the surface of the "Thick steel" or thin steel for that matter... No matter how thin or thick the layer of condensation may be!!!:) :) :)

Finally, in certain circumstances if there is a condition where the base metal is contaminated with enough hydrocarbons as a layer on the surface as a result of not preparing the metal via proper cleaning... the ionization that can occur, coupled with the addition of or not - of residual contaminants found within the GTAW torch parts themselves, or even on the surface of the improperly cleaned tungsten can cause such a condition to occur whereby the carbon from either source can attract tungsten to bond with it and partially vaporize into the arc plume, and eventually combine with the weld pool yet, the conditions must be favorable for this to happen at all. ;)

I hope I answered your questions properly Al :) :) :)

Respectfully,
Henry