TorqBolt offers two different Zeron 100 round bar products to service the fastener industry with high strength, highly corrosion resistant products.
To provide a Zeron 100 bar products with increased tensile
properties the Zeron 100 FG variety was created. Lightly cold
working the bar to its final size provides higher strength. Zeron 100 FG meets
the requirements of ASTM A276 for UNS S32760 Condition S. “S” indicates the
strain hardened condition. For faster design purposes, Zeron 100 FG
meets the mechanical requirements of ASTM A193, Grade B7 material. ASTM A193 is a
specification covering alloy and stainless steel bolting for high temperature or
high pressure service. Zeron 100 is not specifically addressed in the
specification, so the B7 grade is referenced for mechanical property
information.
Zeron 100 is frequently specified for pipework systems handling
corrosive fluids. Although many pipes and fittings are joined by welding, in some
places it is necessary to use flange connections. Where corrosion of the flange
bolts may occur it is desirable to use corrosion resistant fasteners. Zeron 100
is available as a fastener in two different grades. FG grade meets the tensile
properties of ASTM A193 grade B7. In addition Zeron 100 is available as fasteners
in the solution annealed form. This has a lower yield and tensile strength
compared with FG, but headed fasteners can be manufactured more cheaply in the
solution annealed condition. This is because solution annealed bolts can be
headed by forging followed by solution annealing, while FG, whose properties are
produced by controlled strain hardening, must be machined from bar.
Galling
is often assumed to be a problem with stainless steels. The problem is
traditionally associated with 300 series austenitic alloys. Galling is less of a
problem with more highly alloyed austenitic and duplex alloys. Bar in Zeron 100 SA for nuts, is supplied in the solution
annealed condition. This typically has a hardness of 50HV less than that of cold
worked FG material. This will minimize the risk of galling. Zeron
100 bolts have been used for many years in submersible marine pumps and it
is common practice to coat fasteners with ~6μm of copper. This is produced by
electroplating and is usually applied to the male stud. This is to ensure ease in
dismantling for servicing of the pumps. In critical applications, where very high
torques are required, successful use has been reported of conventional
anti-galling sprays (e.g. Rocol), copper-loaded greases, and PTFE coatings. The
use of molybdenum disulphide lubricant should be avoided for elevated temperature
service, because of the risk of decomposition of the lubricant leading to
sulphide attack.
The Zeron 100 FG also meets the minimum Charpy impact
toughness values of 40 joules (29.5 ft-lbf) at -50°C (-58°F).
