WELDING HEAT TREATED 4130 Chrome Moly
(QUENCHED AND TEMPERED)
Why not Use a High
Strength, High Toughness Steel Easier to Weld Than 4130 Chrome Moly!
Still want to use
higher strength tubing? Have someone make an alloy like the Navy’s HY-130
or Hy-140 (same material usually heat treated differently) which would be
far better choice. I have worked with this product for over 30 years on a
number of applications requiring not only strength but excellent toughness,
i.e. for submarine hulls that can withstand a depth charge!
Some
of the tests the Navy requires such as the explosion bulge test must be
performed on a welded plate and when completed successfully the test
specimen looks like a WW I metal helmet! The weld and base material must
yield but show no fractures – even on thick material!
Unfortunately, to my
knowledge, this material is not being made in tubing. It will also
cost more than 4130 because of the alloy content and freedom from
undesirable impurities which can lead to cracking and reduced toughness. In
the chart below you’ll note the steel contains much lower carbon and far
lower undesirable residual elements such as sulfur and phosphorus. That
steel uses expensive elements like 2.5% Nickel and three times the 0.2%
Molybdenum found in 4130. It is much more weldable than 4130 and the Heat
Affected Zone (HAZ) properties will be satisfactory at normal welding heat
inputs.
This old statement
that 4130 is weldable stems from the 1940’s when folks used gas welding
(read lots of preheat and very slow cooling!) To achieve good weldability
carbon content in base materials and welding rods has reduced over the years and even
100,000 psi yield gas and oil transmission pipe has carbon levels of 0.10
and lower! this chart presents some chemistries and mechanical
properties: