From: hollen@megatek.UUCP (Dion Hollenbeck)
Subject: Re: Oxy/Acet welding problems
Organization: Megatek Corporation, San Diego, California
	<1993Jan26.145929.19590@hellgate.utah.edu>
Date: Wed, 27 Jan 1993 19:20:46 GMT

>>>>> On 26 Jan 93 14:59:28 MST, ndmead%gr.cs.utah.edu@cs.utah.edu (Nathan Mead) said:

Nathan> In article <C1H4Bx.M96@dartvax.dartmouth.edu>, Charles.K.Scott@dartmouth.edu (Charles K. Scott) writes:

Nathan> Welding is all about carefully controlling the temperature at
Nathan> the weld puddle.  It needs to be hot enough to get the desired
Nathan> penetration and not so hot that it "blows out" or overheats
Nathan> the weld area.  

I was taught to vary the tip size and flame in the following manner.
You want a flame where there is the slightest feather beyond the inner
blue cone.  Light the gas and add oxy until blue cone, back off oxy
until feather just appears.  This is just the slightest bit of a
reducing flame.  You want the maximum amount of gas and oxy in these
proportions which will heat your puddle as quickly as possible WITHOUT
blowing spatters out of the puddle or burning a hole through the
metal.  If you are pushing too much gas/oxy out too small a tip, you
will have trouble getting a puddle to form and when it does, it will
blow metal out of the puddle.  The solution to this is to get a bigger
tip until you can form a puddle quickly without blowout.  Note that
you can also cause blowout with a correctly sized and adjusted tip by
getting it too close to the puddle.  By getting a bigger tip, you burn
more gas/oxy, but the "wind" created from the tip is less.

Nathan> In gas welding once a flame size is set temperature is
Nathan> controlled by the distance of the flame, the way the flame is
Nathan> moved about and by the addition of filler metal.  Generally
Nathan> the flame control is hardest to master and requires lots of
Nathan> practice.  However controlling the rate of addition of filler
Nathan> material should not be ignored.  Typically I heat the material
Nathan> up to where a puddel starts to form, add enough material to
Nathan> get a good puddle and then work the puddle down the joint.

Done correctly with joints which fit closely, you can generally work a
puddle down the entire length of a joint with no filler material at
all!  In this manner, you will achieve good penetration, however, you
will have a little depression because some of the metal from both
sides has flowed into the crack of the joint.  This is what filler rod
is for.  I find that if you get a good puddle and then place your
filler rod ahead of the puddle in the flame wash, the filler rod will
get hot and when it is needed, a little will jump off the rod and into
the puddle.  This is not a joke.  It takes fine control of distance of
rod from puddle, right size rod and angle of flame to get this to
occur and I don't do it all the time either, but when you get it
right, it is like magic.  You get a bead which is not too full, nor
has a depression.  The rod and the flame cooperate to transfer the
correct amount of rod to the puddle.  The rod to puddle distance is
generally less than 1/8" to get this to happen, but of course varies
with amount of flame, thickness of metal, size of puddle and size of
rod.  If you concentrate on puddle generation and slowly letting your
flame move the puddle down the joint, then you won't have to worry
about good penetration.  Filler rod is just that, it does not have
anything to do with penetration, it only has to do with providing
enough metal to fill the crack between pieces being joined.  You can
easily get a highly domed bead which has NO penetration at all because
you melted a lot of filler rod onto metal which was not properly
heated in the first place.  Also, you don't ever want to touch the
filler rod to the work, this the easiest way to get globs of filler
rod spattered to both sides of the bead,  Let the rod be "wicked" into
the puddle and you will have a smooth consistent bead.




-- 
Dion Hollenbeck                        Email: hollen@megatek.com
Senior Software Engineer                      megatek!hollen@uunet.uu.net
Megatek Corporation, San Diego, California    ucsd!megatek.uucp!hollen