On Saturday 21 November 2009, Peter blodow wrote:
>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.
>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.
>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.
>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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