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RE: Torch Cutting Steel

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See below.

Harold Sprague, PE
Krawinkler, Luth & Assoc.

-----Original Message-----
From:	Serroels, Chris/SAC [SMTP:CSerroel(--nospam--at)]
Sent:	Thursday, June 25, 1998 12:30 PM
To:	'seaoc(--nospam--at)'
Subject:	RE: Torch Cutting Steel

The steel being cut is a low-alloy steel, A242 Grade 45.  The plates are 1 1/2 inches thick.

What are the adverse effects on alloy steel?  
[Harold Sprague]  Alloyed steel has several elemental components that are essentially frozen in a matrix to create a particular type of grain structure.  Heating the alloy steel above specified alloying temperature limits can cause changes in the grain structure and deposits of various elements, markedly changing the mechanical properties in the heat effected areas.

Any special considerations  considering the type of steel involved and the thickness of the plates being cut?
[Harold Sprague]  This is a weathering steel and cutting this steel with ox-acetylene should not be a problem.  Depending on the length and looking at the plate thickness I would suggest mounting the burner on a track to get a nice smooth cut.  Done correctly it will look like a saw cut.


> -----Original Message-----
> From:	hsprague(--nospam--at) [mailto:hsprague(--nospam--at)] On Behalf Of
> hsprague(--nospam--at)
> Sent:	Thursday, June 25, 1998 10:54 AM
> To:	'seaoc(--nospam--at)'
> Subject:	RE: Torch Cutting Steel
> See below.
> Harold Sprague, PE
> Krawinkler, Luth & Assoc.
> 	-----Original Message-----
> 	From:	Serroels, Chris/SAC [SMTP:CSerroel(--nospam--at)]
> 	Sent:	Thursday, June 25, 1998 10:46 AM
> 	To:	'SEAOC'
> 	Subject:	Torch Cutting Steel
> 	I have a project where we are cutting off a portion of the
> bottom of a
> 	steel tower to install
> 	a taller bearing.  I am wondering what effect the torching will
> have on
> 	the steel that remains.
> 	Will the heat generated by torching have a detrimental effect?
> 	[Harold Sprague]  The heat will only have a very localized
> effect on normal carbon structural steel.  The only adverse effect is
> on heat treated or alloy steels.  Keep in mind that ox-acetylene
> cutting is a high temperature chemical reaction, and not a melting
> process.  As opposed to air-arc or plasma arc.
> 	Other engineers have suggested that during torching the only
> significant
> 	heat generation
> 	occurs when burning the initial hole.  Once the cut is initiated
> the
> 	heat dissipates quickly.
> 	Is this an accurate assessment?
> 	[Harold Sprague]  Yes.
> 	What other options exist?  I heard of a method called
> air-arc'ing but am
> 	unfamiliar with it.
> 	[Harold Sprague]  Air arc is a process by which you use a carbon
> electrode and strike the arc and melt the metal.  Compressed air is
> blown on the molten metal clearing it from the cut. 
> 	Chris