applications outside that industry, including power generation and heat transfer.
“Titanium’s springback is worse than
that of stainless steel, which is bad
enough, so forming it and welding it at
a typical mill line speed is tough,” Henricks said. Gilreath interpreted its characteristics as challenging, not problematic,
and worked titanium into the company’s
area of expertise.
A swimming pool heat pump illus-
trates the many benefits of titanium. In
a conventional pool heating system, the
refrigerant flows through coiled copper
tube. A twisted or spiraled titanium tube
provides more surface area, so heat trans-
fer is more efficient. Copper erodes away
because of the constant flow, whereas
titanium resists erosion. Also, titanium
resists scale buildup. A heat pump with
copper coils usually has a 3- to 5-year
warranty, Adams said. A titanium heat
exchanger has a lifetime warranty.
This doesn’t mean that titanium is a
primary or dominant alloy at G & L. In
fact, it would be hard to pin down any
one alloy that takes a lead role. The
company has decades of experience in
making products from austenitic stainless steels (SAE 304 and 304L, 316 and
316L, and 321), ferritic stainless steels
(SAE 409, 436, and 439), superferritic (
E-BRITE®), duplex alloys (SAE 2205, 2209,
2507, and 2102), high-nickel alloys (SAE
600, 625, and 825), and INCOLOY® and
MONEL® alloys (SAE 323 800, 840, and
400). The products are as diverse as the
alloys (see Figure 1).
Welded Tube Made Well. Tube and
pipe producers can use up to four modes
for testing the products they make: inline
nondestructive, offline nondestructive,
offline destructive, and metallurgical
analysis. G & L uses all four.
As the tube is running through the
mill, it is evaluated with eddy current.
Offline ultrasonic testing is used on
some products. These comprise the first
line of defense against defects.
Next is a thorough visual evaluation.
When he was a student at Tennessee
Tech, Gilreath learned about metallurgical inspection, and he brought this capability to G & L. The company has a
metallurgical lab that examines welds,
heat-affected zones, and parent materials, making micrographs up to 100 times
magnification to measure grain size and
evaluate weld profiles, thereby validating mill setups. And, although the company doesn’t do any fabrication, it knows
that many of its products go through
severe forming operations, so it puts its
products through a variety of destructive
tests to evaluate minimum yield strength,
ultimate tensile strength, and percentage
of elongation. Specific destructive tests
include flaring, flanging, flattening, reverse flattening, reverse bending, and
hardness testing. It also does corrosion-resistance testing.
Finally, for lengths of tube intended to
carry fluids, an air-under-water leak test
pinpoints any pinholes that slipped past
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