Page 21 - HIWT Winter 2012 World of Welding

hiwt@welding.org HOBART INSTITUTE OF WELDING TECHNOLOGY

free MaCHining steel

By Elmer Swank, Jr.
CWI/CWE
HIWT Instructor

response:

The AISI 1144 is a resulfurized carbon steel containing
approximately 1.50% manganese and .24% to .33% sulfur to
make it free machining steel. The sulfur may improve the
machinability, but it causes hot cracking in the weld and heat
affected zone during welding. As the weld metal begins to
solidify, the sulfur forms liquid film around the metal grains
at the grain boundaries. The shrinkage in the weld area as
the weld cools creates enough stress to cause hot cracking.
Preheating and post-weld heat treatments will not correct this
problem. The sulfur may also cause porosity.

If welding is part of the fabrication procedure, free machining
Question: steels should not be used. Welds made on free machining steel
using any welding process or filler metal will be unreliable.
I would like to weld AISI 1144 steel, but it seems to have poor The elements that are in free machining steel, such as lead,
welding properties. I preheat it and weld with 70s TIG or sulfur, phosphorus, and selenium, are considered impurities in
MIG wires, but cracking is always a problem. Post heating most weldable steels and kept at a very low content.
is not practical many times, because of time factor and cost.
Many times, I am required to join it to A2 stainless, 1018, In non-critical applications, if free machining steel has to be
and other steels. In our full service job shop, we weld just welded, use low amperage to reduce base metal dilution, a
about everything. Can you provide any advice to make this slow travel speed, and plenty of filler wire.
application easier?

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