HY 100 Steel Details
HY 100 was used in the construction of the Seawolf Class nuclear powered fast attack submarines where
the design dictated that the craft had to operate at greater depths than previous designs and hence withstand
increased hull pressure.
In addition the alloy had to have a high degree of toughness and impact strength to withstand the massive
changes in pressure and has excellent fabrication properties to allow the welding of complex structures.
The alloy has high strength, a minimum of 100ksi proof stress, which is obtained by a water quench and
ageing heat treatment.
This low alloy martensitic steel contains small additions of chromium and nickel to help with corrosion
resistance and is supplied in the Type B condition bright finish.
Owing to the rigorous requirements of the end application, all material is electric arc melted and vacuumed
degassed with argon. All bar stock is ultrasonically tested to MIL STD 271,(NAVSEA T9074-AS-GIB-010/
271) and has full Level I Subsea traceability.
Diversified Metals Inc also has the capabilities of supplying gun drilled tubing.
The alloy has since found wider applications in the construction of pressure vessels, armor plating, the
petrochemical industry and many other applications requiring greater strength and high integrity material .
Weldments of HY-80 are noted for good ductility, notch toughness and strength. It is recommended to weld
using the metal-arc process with low hydrogen electrodes of Type E-10018 or E-11018. It is important to
use approved weld procedures, so that the correct heat input per inch of weld bead is introduced, which
would otherwise cause degradation of notch toughness. Electrodes should be warmed before use to drive
off any moisture to avoid hydrogen pick-up in the weld. Preheating is not required, except for very heavy
section thickness welds or heavily constrained welds. Post-heating is not required but a stress relief anneal,
after welding of sections of 1-1/2″ thick or greater, is desirable. However the alloy may be used in the as-
High pressure tubing can be made from HY 100 and HY 80 bars up to 30 feet in length. Tubes can be
welded together to achieve longer lengths. The material’s superior combination of ductility and fracture
toughness make it a great choice for pressures as high as 14,000 PSIG operating pressure or more depending
on wall thickness. The tubes have been tested up to 21,000 PSGI. Typical operating temperatures are 500o
F to -20o F. The tubes can be bent up to 180 degrees with a maximum allowable thinning of 10% and
flattening of 8% depending on tube OD and wall thickness and will maintain their physical properties. ID
surface finishes of 64 micro or greater can be achieved. Straightness tolerances of .015″ per foot can be
maintained. Bars can be ultrasonically tested in immersion and/or Mag Particle tested to ensure integrity
High Strength HY100 steel has a well documented history in pressure vessel applications particularly in
Submarine hull construction.
Under arduous working conditions the steel has to have excellent low cycle fatigue properties and in conjunction with a high resistance to crack propagation.
Recent work conducted by Diversified Metals Inc on 3.5” solid bar stock has confirmed the excellent fracture toughness properties of HY 100
Tests were performed to ASTM E 1820 C(T) geometry and C-R orientation at a temperature of 73ºc in air.
Initiation toughness values J1c ranged from 1341-1999 lbf-in/in
With Fracture toughness KJ1c values ranging from 210-257 ksi√2
These were taken from bars with a range of mechanical properties
Mechanical Properties of HY 100 Steel
|Ultimate Tensile Strength*
||0.2% Yield Strength
||Elong in 2″ (Min)
||Reduction of Area (Min)
||18 (L) 16 (T)
||50 (L) 45 (T)
* Not a requirement of the specification
Impact Properties of HY 100 Steel
||Charpy V-notch Longitudinal
||Charpy V-notch Transverse**
||ft lbs Joules
||ft lbs Joules
**Transverse properties only required for 4″ (100mm) dia or greater
The properties shown below are for guidance only and are not intended for specification purposes.
Physical Properties of HY 100 Steel
|Mean Liner Expansion 0-200ºc
|Mean Liner Expansion 0-400 ºF
||0.010 in/in/ ºF x10³
| Poisson€s ratio
|Modulus of Elasticity 10³
|Shear Modulus 10³
The data is believed to be accurate but Diversified Metals Inc makes no representation or warranty of any kind (expressed or implied) and assumes no responsibility with respect to its accuracy and values should only be used as a guide.