Post by Peter blodow
I take this discussion about welding and combustibles as an oopportunity
to clarify a few things.
1. CO2 is used in arc welding only for old soft iron (mild steel) in order
to maintain the percentage of carbon of the components also in the seam
material. It's a balance reaction of consuming carbon by oxidation and
returnig this amount by decomposing CO2. Without this, the properties of
the material would be strongly affected, e.g. iron turning brittle
jeopardizing constructions. Therefore, there are welding gases on the
market containing different amounts of CO2 mixed with argon. Linde AG gave
it the brand name of CORGON. For all other metals including stainless steel
welding a pure inert gas is used, preferably argon because of the low
price. It is obtained in the process of air liquefying as a byproduct. That
means, it should cost nothing at all because air is actually liquefied to
obtain liquid oxygen and nitrogen....:-)
I am very well aware of the control one has over the finished weld that can
be had by flame adjustments when using a smith wrench. I took welding lessons
from the fellow that used a smith wrench to plug the con-rod hole in that big
6 mercury block, which is Mag. Admittedly that was 55 years ago, but not
much has changed. If I find myself working with scrap bed rail, use a hard,
high oxygen flame to soften the brittleness, or on mill run steel, leave a
bit of a feather on the flame to add carbon to the puddle. Tools of the
trade so to speak.
And I'm aware that the argon should be a throwaway, and what they don't sell
probably is vented, but it seems outrageous to me that a little bottle, the
same size your grandmother might carry over her shoulder with o2 in it for
half an afternoons shopping or a league bowling session, should cost me $125.
That is purely a case of what the traffic will bear pricing. Of course these
same folks are also charging about 90$ for a T2 sized bottle of dry nitrogen,
something broadcasters use to keep the transmission lines pressurized to
about 2 psi so any leaks won't suck in water when it rains as water=a line
burnout & a few days off the air while you get a crew in to pull the lines
off the tower, clean up the mess that burnt teflon leaves behind, and replace
the burnt teflon. I got tired of that and we did it ourselves the last time,
finding about a pint of water sitting in an elbow at the tower top that a
previous crew hadn't cleaned out after leaving it open overnight while it
rained about 2" in the night. Job security I guess. We used an old gravely
tractor/lawn mower for the lifter, and had 1k feet of 1/8" aircraft cable
rigged over an 8" pully at the tower top to do the line lifting/lowering, 2,
20' pieces at a time. I might add that was a decade back, no repeats since.
That all boils down to "if you want the job done right, do it yourself". And
the tower company that did that to us has never gotten another dime from us,
with the reason being carefully explained in 1 and 2 syllable words every
time their sales force calls us looking to get a painting job or whatever.
Post by Peter blodow
2.) Thermite is a mixture or aluminium powder and iron oxides. When
kindled, It develops temperatures above 3000 degrees C (5400 F) by burning
(oxidizing) the Alu and in turn reducing the iron oxides to metallic iron
with sufficient surplus energy to melt this iron at the instant and even
melt the surrounding substances such as railway tracks. However, the
thermite mix can't be started with a simple match, so a small strip of
magnesium sheet is used as an iginiter. Alu is so reactive and, at the same
time, safe, that today, it's the main component of rock blasting.
3.) CO2 is a common fire extinguishing agent especially for strange and
rare combustibles. It can't give off oxygen at the temperatures considered.
It is, however, dangerous for alll personell around and, at least
hereabouts, there must be a alarm time before the CO2 cylinders are fired.
This delay might be detrimetal to the success of fire extinguishing. Some
substances like thermite can't be extinguished because they carry their
4.) I don't think there is much use in applying mist to machine tools.
There is way too little effect compared with flooding. Modern lathes and
mills are capsuled and coolant is directed with high pressure from as many
of 10 to 20 nozzles from all directions onto the tools. This makes it
possible to mill stainless steel with, say, 15.000 rpm or Alu with up to
100.000. I bought a CNC mill some years ago and all the elder statesmen in
the shop shook their heads when they first saw what happened. Point is: the
machine adjusts its speed automatically to tool diameter and material to be
processed, and all the workers, with their lifetime experience, believed
that the machine must be in error and the tools won't make it longer than
And you had to jack some jaws back up off the floor. I have enjoyed the hell
out of doing that to supposedly educated broadcast engineers myself.
Post by Peter blodow
5.) I can't see what all this has to do with electronic machine
It doesn't, but the machining is just part of the process of 'making', and I
believe on balance we all learn from these conversations, enough to tolerate
if not enjoy them.
Post by Peter blodow
Greeting from Germany
(and don't call me wise guy, I used to be the head of a rather special
scientific work shop for more than 30 years)
Wouldn't think of it, Peter. You, like everyone else on this list, has
contributed to my education, such as it is. Formally, it stops at the 8th
grade, but most know better than that, my education has never stopped.
As the grey matter gets old, CRS sets in, so the process _is_ slower at 75
than it was at 15, but I would like to think it still continues. :-)
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