View source for HY-80

{{Short description|Alloy steel}}
[[File:Plunger (SSN-595) on the ways at Mare Island.jpg|thumb|upright|[[Permit-class submarine|''Permit'' class]] {{USS|Plunger|SSN-595|6}} on the building ways at [[Mare Island Naval Shipyard|Mare Island]]]]
'''HY-80''' is a high-tensile, high yield strength, low [[alloy]] [[steel]].  It was developed for use in naval applications, specifically the development of pressure hulls for the US nuclear [[submarine]] program and is still currently used in many naval applications.  It is valued for its [[strength to weight ratio]].{{Citation needed|date=February 2019}}

The "HY" steels are designed to possess a high [[yield strength]] (strength in resisting permanent plastic deformation).  HY-80 is accompanied by HY-100 and HY-130 with each of the 80, 100 and 130 referring to their yield strength in [[ksi (unit)|ksi]] (80,000 psi, 100,000 psi and 130,000 psi).  HY-80 and HY-100 are both weldable grades, whereas the HY-130 is generally considered unweldable.  Modern steel manufacturing methods that can precisely control time/temperature during processing of HY steels has made the cost to manufacture more economical.<ref name="Yayla, 2007" /> HY-80 is considered to have good corrosion resistance and has good formability to supplement being weldable.<ref name="Yayla, 2007" /> Using HY-80 steel requires careful consideration of the welding processes, filler metal selection and joint design to account for microstructure changes, distortion and stress concentration.

== Submarines ==
The need to develop improved steels was driven by a desire for deeper-diving submarines. To avoid detection by [[sonar]], submarines ideally operate at least 100 metres below the [[Sonic Layer Depth|sonic layer depth]].<ref name="FAS" /> World War II submarines operated at a total depth of rarely more than 100 metres. With the development of [[nuclear submarine]]s, their new independence from the surface for an air supply for their diesel engines meant that they could focus on hidden operation at depth, rather than operating largely as surface-cruising submersibles. The increased power of a nuclear reactor allowed their hulls to become larger and faster. Developments in sonar made them able to hunt effectively at depth, rather than relying on visual observations from [[periscope depth]]. All these factors drove a need for improved steels for stronger pressure hulls.

The strength of a submarine hull is constrained not merely by yield strength, but also fatigue strength.<ref name="Naval Engineers Journal" /> As well as the obvious need for a hull strong enough not to be crushed at depth, the cyclical effect of hundreds of dives over a submarine's lifetime{{efn-lr|{{USS|Tullibee|SSN-597|6}}, 730 dives during her time in commission.<ref>{{Cite web
  |title=USS ''Tullibee'' – History
  |url=http://www.usstullibee.com/tullibeehistory.html
  |access-date=2015-05-20
  |archive-url=https://web.archive.org/web/20140517121715/http://www.usstullibee.com/tullibeehistory.html
  |archive-date=2014-05-17
  |url-status=dead
  }}</ref> {{USS|Torsk|SS-423|6}}, a diesel training submarine, made 11,884 dives.<ref>{{Cite web
  |title=History of USS ''Torsk'' (SS-423)
  |url=http://www.usstorsk.org/history/423hist.htm
  |website= usstorsk.org
}}</ref>}} mean that [[Fatigue (material)|fatigue strength]] is also important. To provide sufficient resistance to fatigue, the hull must be designed so that the steel always operates below its [[Fatigue limit|endurance limit]]; that is, the stress due to pressure at depth remains less than the fatigue strength for an indefinite number of cycles.

US submarines post-WWII, both conventional and nuclear, had improved designs compared to the earlier [[fleet submarine]]s. Their steel was also improved and was the equivalent of "HY-42".<ref name="FAS" /> Boats of this construction included {{USS|Nautilus|SSN-571|6}}, and the [[Skate-class submarine|''Skate''-class]], which were the first nuclear submarines, with the then-conventional hull shape. The later [[Skipjack-class submarine|''Skipjack'' class]], although of the new Albacore 'teardrop' hull form, also used these earlier steels. Such boats had normal operating depths of some {{convert|700|feet}}, and a [[crush depth]] of {{convert|1100|feet}}. [[Bureau of Ships]] conducted a research program for developing higher strength steel for ship and submarine construction. During testing, a variant of [[special treatment steel]] (STS), a homogeneous [[Krupp armour|Krupp-type armor]] steel developed by [[Carnegie Steel]] in 1910 and commonly used for deck protection, with modifications in carbon and nickel and the addition of [[molybdenum]], became known as "Low-carbon STS"; this steel showed the best combination of all the desirable properties. Low-carbon STS became the forerunner of HY-80,<ref>[https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1559-3584.1965.tb05346.x An Evaluation of HY-80 Steel as a Structural Material for Submarines.]</ref> and was first used in 1953 for the construction of {{USS|Albacore|AGSS-569|6}}, a small diesel research submarine. ''Albacore'' tested its eponymous teardrop hull shape, which would form a pattern for the following US nuclear classes.<ref>''Accelerating Utilization of New Materials''. National Research Council (U.S.). Committee on Accelerated Utilization of New Materials. pp. 77–78.</ref>

Although the operating depths of submarines are highly secret, their crush depth limits can be calculated approximately, solely from knowledge of the steel strength. With the stronger HY-80 steel, this depth increased to {{convert|1,800|feet}} and with HY-100 a depth of {{convert|2250|feet}}.<ref name="FAS" />

The first production submarines to use HY-80 steel were the [[Permit-class submarine|''Permit'' class]]. These reportedly had a normal operating depth of 1,300 feet, roughly two-thirds the crush depth limit imposed by the steel.<ref name="FAS" /> {{USS|Thresher|SSN-593|6}}, the lead boat of this class, was lost in an accident in 1963. At the time, this unexplained accident raised much controversy about its cause and the new HY-80 steel used was looked at suspiciously, especially for theories about weld cracking having been the cause of the loss.<ref name="Courant, 1991" /><ref name="Rickover Effect" /><ref name="Polmar, Thresher" />

HY-100 steel was introduced for the deeper diving [[Seawolf-class submarine|''Seawolf'' class]], although two of the preceding HY-80 ''Los Angeles'' class, {{USS|Albany|SSN-753|6}} (1987) and {{USS|Topeka|SSN-754|6}} (1988), had trialled HY-100 construction. {{USS|Seawolf|SSN-21|6}} is officially claimed to have a normal operating depth of "greater than 800 feet". Based on the reported operating depth of ''Thresher'', it may be assumed that the normal operating depth of ''Seawolf'' is roughly double the official figure.<ref name="FAS" />{{Copyright violation|date=May 2023}}{{Unreliable source|date=May 2023}}

HY-100 too was dogged by problems of weld cracking. ''Seawolf''{{'}}s construction suffered setbacks in 1991 and an estimated 15% or two years' work on hull construction had to be abandoned.<ref name="Courant, 1991" /> Although later solved, these extra costs (and the post-Soviet peace dividend) were a factor in reducing the planned 29 ''Seawolf'' submarines to just three constructed.<ref name="_8" />

== Metallurgy ==
HY-80 steel is a member of the low carbon, low alloy family of steels with [[nickel]], [[chromium]] and [[molybdenum]] (Ni-Cr-Mo) as alloying elements and is hardenable.  The weldability of the steel is good, though it does come with a set of challenges due to the carbon and alloy content.<ref name="ASTM, Welding" />  The carbon content can range from 0.12 to 0.20 wt% with an overall alloy content of up to 8 wt%.  It is also used extensively in military/navy applications with large thick plate sections that add to the potential weldability problems e.g. ease of heat treatment and residual stresses in thick plate.  The primary objective during the development of the HY- grades of steel was to create a class of steels that provide excellent yield strength and overall toughness, which is accomplished in part by quenching and tempering.  The steel is first heat treated at 900 degrees Celsius to [[austenite|austenitize]] the material before it is quenched.  The rapid cooling of the quenching process produces a very hard microstructure in the form of [[martensite]].<ref name="Roepke, 2009" /> Martensite is not desirable and thus it is necessary for the material to be tempered at approximately 650 degrees Celsius to reduce the overall hardness and form tempered martensite/[[bainite]].<ref name="Roepke, 2009" /><ref name=":4">{{Cite journal
  |last=Chae|first=D|date=September 2001|title=Failure Behavior of Heat-Affected Zones within HSLA-100 and HY-100 Steel Weldments
  |journal=[[Metallurgical and Materials Transactions|Metall. Mater. Trans.]]
  |volume=32A|pages=2001–2229
}}</ref>

The final microstructure of the weldment will be directly related to the composition of the material and the thermal cycle(s) it has endured, which will vary across the base material, Heat Affected Zone (HAZ) and Fusion Zone (FZ).  The microstructure of the material will directly correlate to the mechanical properties, weldability and service life/performance of the material/weldment.  Alloying elements, weld procedures and weldment design all need to be coordinated and considered when looking to use HY-80 steel.

HY-80 and HY-100 are covered in the following US military specifications:
*MIL S-16216<ref name="MIL-S-16216" />
*MIL S-21952<ref name="MIL S-21952" />

=== Alloy content ===
The alloy content will vary slightly according to the thickness of the plate material.  Thicker plate will be more restrictive in its compositional alloy ranges due to the added weldability challenges created by enhanced stress concentrations in connective joints.<ref name="Lippold, 2015">{{Cite book
  |title=Welding Metallurgy and Weldability
  |last=Lippold  |first=John
  |publisher=Wiley
  |year=2015
  |isbn=978-1-118-23070-1
  |location=United States of America
  |pages=288–300
}}</ref>

==== Importance of key alloying elements ====

Carbon – Controls the peak hardness of the material and is an austenite stabiliser,{{sfnp|Lippold|2015|page=226}} which is necessary for martensite formation.  HY-80 is prone to the formation of martensite and martensite's peak hardness is dependent on its carbon content. HY-80 is an [[face-centred cubic|FCC]] material that allows carbon to more readily diffuse than in FCC materials such as [[austenitic stainless steel]].

Nickel – Adds to toughness and ductility to the HY-80 and is also an austenite stabilizer.

Manganese – Cleans impurities in steels (most commonly used to tie up sulfur) and also forms oxides that are necessary for the nucleation of acicular ferrite.  Acicular ferrite is desirable in HY-80 steels because it promotes excellent yield strength and toughness.<ref>{{Cite book
  |title=Welding Metallurgy
  |last=Kou  |first=Sindo
  |publisher=Wiley-Interscience  |location=United States of America
  |year=2003
  |isbn=978-0-471-43491-7
  |pages=74–84
}}</ref>

Silicon – Oxide former that serves to clean and provide nucleation points for acicular ferrite.

Chromium – Is a ferrite stabilizer and can combine with carbon to form chromium carbides for increased strength of the material.

==== Trace elements ====

Antimony, tin and arsenic are potentially dangerous elements to have in the compositional makeup due to their ability to form [[eutectic]]s and suppress local melting temperatures.  This is an increasing problem with the increased used of scrap in the making of steel in the [[electric arc furnace]] (EAF) process.

The precise range of permitted alloy content varies slightly according to the thickness of the sheet. The figures here are for thicker sheets, {{convert|3|inch}} and over, which are the more restrictive compositions.

{| class="wikitable" style="text-align: center;"
|-
|
! HY-80 
! HY-100
|-
! colspan=3 | Alloying elements 
|-
! [[Carbon]] 
| 0.13–0.18% || 0.14–0.20%
|-
! [[Manganese]] 
| colspan=2 | 0.10–0.40%
|-
! [[Phosphorus]] 
| colspan=2 | 0.015% max
|-
! [[Sulfur]]
| colspan=2 | 0.008% max
|-
! [[Silicon]]
| colspan=2 | 0.15–0.38%
|-
! [[Nickel]]
| colspan=2 | 3.00–3.50%
|-
! [[Chromium]] 
| colspan=2 | 1.50–1.90%
|-
! [[Molybdenum]] 
| colspan=2 | 0.50–0.65%
|-
! colspan=3 | Residual elements{{efn-lr|name=Trace elements|Elements not added deliberately}}
|-
! [[Vanadium]] 
|colspan=2 | 0.03% max 
|-
! [[Titanium]] 
|colspan=2 |  0.02% max 
|-
! [[Copper]]
| colspan=2 | 0.25% max
|-
! colspan=3 | Trace elements{{efn-lr|name=Trace elements}}
|-
! [[Antimony]]
| colspan=2 | 0.025% max
|-
! [[Arsenic]]
| colspan=2 | 0.025% max 
|-
! [[Tin]] 
| colspan=2 | 0.030% max 
|}

A further steel, HY-130, also includes vanadium as an alloying element.<ref name="ASTM, Welding" /> Welding of HY-130 is considered to be more restricted, as it is difficult to obtain filler materials that can provide comparable performance.<ref name="ASTM, Welding" />

=== Characteristics ===
{| class="wikitable" style="text-align: center;"
|+Physical Properties of HY-80, HY-100, and HY-130 Steel<ref name="AD-A233 061" />
|
!HY-80 steel
!HY-100 steel
!HY-130 steel
|-
!Tensile [[yield strength]]
|80 ksi
({{convert|80,000|psi|MPa|abbr=on|disp=out}})
|100 ksi
({{convert|100,000|psi|MPa|abbr=on|disp=out}})
|130 ksi
({{convert|130,000|psi|MPa|abbr=on|disp=out}})
|-
![[Hardness]] ([[Rockwell hardness|Rockwell]])
|C-21
|C-25
|C-30
|-
! colspan="4" |Elastic Properties
|-
![[Elastic modulus]]
<math>E</math> ([[Gigapascal|GPa]])
| colspan="3" |207
|-
![[Poisson's Ratio]]
<math>\nu</math>
| colspan="3" |.30
|-
![[Shear modulus]]
<math>G = E / 2 (1 + \nu)</math> (GPa)
| colspan="3" |79
|-
![[Bulk modulus]]
<math>K = E / 3 (1 - 2\nu)</math> (GPa)
| colspan="3" |172
|-
! colspan="4" |Thermal Properties
|-
![[Density]]
<math>\rho</math> (kg/m<sup>3</sup>)
|7746
|7748
|7885
|-
![[Thermal conductivity|Conductivity]]
<math>k</math> (W/mK)
| colspan=2 |34
|27
|-
![[Specific heat]]
<math>c_p</math> (J/kgK)
| colspan=2 |502
|489
|-
![[Thermal diffusivity|Diffusivity]]
<math>k / \rho c_p</math> (m<sup>2</sup>/s)
| colspan=2 |.000009
|.000007
|-
![[Coefficient of expansion]] ([[Volumetric|vol.]])
<math>\alpha</math> (K<sup>−1</sup>)
|.000011
|.000014
|.000013
|-
![[Melting point]]
<math>T_{melt}</math> (K)
| colspan=3 | 1793
|}

== Weldability ==

HY-80 steel can be welded without incident provided proper precautions are taken to avoid potential weldability issues.  The fact that HY-80 is a hardenable steel raises concerns over the formation of untempered martensite in both the Fusion Zone (FZ) and the ''[[Heat-affected zone|heat affected zone]]'' (HAZ).<ref name="Roepke, 2009" /> The process of welding can create steep ''[[temperature gradient]]s'' and rapid cooling that are necessary for the formation of untempered martensite, so precautions must be taken to avoid this.  Further complicating the weldability issue is the general application of HY-80 steels in thick plate or large weldments for naval use.  These thick plates, large weldments and rigorous service environment all pose additional risks due to both intrinsic and extrinsic stress concentration at the weld joint.{{sfnp|Lippold|2015|pages=288–297}}

HIC or [[Hydrogen embrittlement|''HAC'']] - hydrogen induced or hydrogen assisted cracking is a real weldability concern that must be addressed in HY-80 steels.  Hydrogen embrittlement is a high risk under all conditions for HY-80 and falls into zone 3 for the AWS method.<ref>{{Cite book
  |title=ASM Metals Handbook 
  |volume=6
  |publisher=ASM International
  |year=1993
  |isbn=978-0-87170-377-4
  |location=United States of America
  |pages=184–188
}}</ref> HAC/HIC can occur in either the Fusion Zone or the Heat Affected Zone.{{sfnp|Lippold|2015|pages=213–262}} As mentioned previously the HAZ and FZ are both susceptible to the formation of martensite and thus are at risk for HAC/HIC. The Fusion Zone HIC/HAC can be addressed with the use of a proper filler metal, while the HAZ HIC/HAC must be addressed with preheat and weld procedures.  Low hydrogen practice is always recommended when welding on HY-80 steels.<ref name="Roepke, 2009" />

It is not possible to [[autogenous weld]] HY-80 due to the formation of untempered martensite.<ref name="Roepke, 2009" /> Use of filler metals is required to introduce alloying materials that serve to form oxides that promote the nucleation of acicular ferrite.<ref name="Roepke, 2009" /> The HAZ is still a concern that must be addressed with proper preheat and weld procedures to control the cooling rates. Slow cooling rates can be as detrimental as rapid cooling rates in the HAZ. Rapid cooling will form untempered martensite; however, very slow cooling rates caused by high preheat or a combination of preheat and high heat input from the weld procedures can create a very brittle martensite due to high carbon concentrations that form in the HAZ.<ref name="Roepke, 2009" />

Preheating should be considered to allow diffusible hydrogen to diffuse and to reduce the cooling temperature gradient.<ref name=":10" >{{Cite web
  |last=Patella|first=Gregory
  |date=December 2014
  |title=A Review of Welding Processes, Mechanical Properties, and Weldability of HY-80 Castings
  |publisher=Graduate Program Rensselaer Polytechnic Institute
  |pages=13–14
  |url=http://www.ewp.rpi.edu/hartford/~gutiee/SPR/Patella-FinalReport.pdf
}}</ref>  The slower cooling rate will reduce the likelihood of martensite formation.  If the preheat temperature is not high enough the cooling temperature gradient will be too steep and it will create brittle welds.<ref name=":10" />  Multipass welds require a minimum and maximum inter-pass temperature with the purpose to maintain yield strength and to prevent cracking.<ref name=":10" />  The preheat and inter-pass temperatures will depend on the thickness of the material.

=== Welding filler metal ===

Generally, HY-80 is welded with an AWS ER100S-1 welding wire.  The ER100S-1 has a lower Carbon and Nickel content to assist in the dilutive effect during welding discussed previously.<ref>{{Cite web
  |url=http://www.weldingwire.com/Images/Interior/documentlibrary/100s-1.pdf
  |title=Technical Data Sheets
  |last=Washington Alloy
}}</ref>  An important function of the filler metal is to nucleate ''[[acicular ferrite]].''  Acicular ferrite is formed with the presence of oxides and the composition of the filler metal can increase the formation of these critical nucleation sites.{{sfnp|Kou|2003|pages=66–97}}

=== Welding processes ===

The selection of the welding process can have a significant impact on the areas affected by welding.  The heat input can alter the microstructure in HAZ and the fusion zone alike and weld metal/HAZ toughness is a key consideration/requirement for HY-80 weldments.  It is important to consider the totality of the weldment when selecting a process because thick plate generally requires multi-pass welds and additional passes can alter previously deposited weld metal.  Different methods ([[SMAW (welding)|SMAW]], [[Gas metal arc welding|GMAW]], [[Submerged arc welding|SAW]]) can have a significant influence of the fracture toughness of the material.<ref name="Yayla, 2007" /> SAW as an example can temper previous weld passes due to its generally high heat input characteristics.  The detailed hardness profiles of HY-80 weldments varies with different processes (gradients vary dramatically), but the peak values for hardness remains constant among the different processes.<ref name="Yayla, 2007" /> This holds true for both HAZ and weld metal.

=== Distortion and stress ===

Given the compositional differences between the base material and the composite zone of the weld it is reasonable to expect that there will be potential ''[[Distortion]]'' due to non-uniform expansion and contraction.  This mechanical effect can cause residual stresses that can lead to a variety of failures immediately after the weld or in service failures when put under load.  In HY-80 steels the level of distortion is proportional to the level of weld heat input, the higher the heat input the higher levels of distortion.  HY-80 has been found to have less in-plane weld shrinkage and less out-of-plane distortion than the common ABS Grade DH-36.<ref name=":21">{{Cite journal
  |last=Yang|first=YP|date=November 2014
  |title=Material Strength Effect on Weld Shrinkage and Distortion
  |journal=[[Welding Journal|Weld. J.]]
  |volume=93|pages=421s–430s
}}</ref>

==Testing==
The testing of HY-80 steel can be divided into the categories of destructive and non-destructive evaluation. A variety of destructive tests from [[Charpy impact test|Charpy V-notch]] to explosion bulge can be performed. Destructive testing is not practical for inspecting completed weldments prior to being placed in service; therefore, [[Nondestructive testing|NDE]] is preferred for this case. Non-destructive evaluation includes many techniques or methods: visual inspection, X-ray, ultrasonic inspection, [[magnetic particle inspection]] and [[eddy-current testing|eddy-current]] inspection.

The ultimate tensile strength of these steels is considered secondary to their yield strength. Where this is required to meet a particular value, it is specified for each order.

Notch toughness is a measure of [[tear resistance]], a steel's ability to resist further tearing from a pre-existing notch. It is usually evaluated as the [[tear-yield ratio]], the ratio of tear resistance to yield strength.<ref name="Kaufman, 38"/><ref name="_2" /><ref name="_4" /><ref name="_5" />

Wrought HY-80 steels are produced by, amongst others, [[ArcelorMittal]] in the USA,<ref name="AASteel" /><ref name="ArcelorMittal"/> forgings and castings in HY-80 by [[Sheffield Forgemasters]]<ref>{{Cite web
  |url=https://www.sheffieldforgemasters.com/capabilities/steel-grades
  |title=Sheffield Forgemasters Steel Grades
  |website=Sheffield Forgemasters
}}</ref> and castings in HY80 by [[Goodwin Steel Castings]] in the UK.<ref>{{Cite web
  |url=http://www.goodwinsteelcastings.com/downloads/GSC-Defence.pdf
  |title=GSC Defence supply materials
  |website=Goodwin Steel Castings Ltd
}}</ref>

== References ==
{{Notelist-lr}}

{{Reflist
|refs=

<ref name="Roepke, 2009" >{{Cite journal
  |last=Roepke|first=C
  |date=August 2009
  |title=Hybrid Laser Arc Welding of HY-80 Steel
  |url=https://app.aws.org/wj/supplement/wj0809-159.pdf
  |journal=Supplement to Weld. J.
  |volume=88
  |pages=159–167
}}</ref>

<ref name="ASTM, Welding">{{Cite book
  |title=Welding the HY Steels
  |year=1971
  |last1=Flax  |first1=R.W.
  |last2=Keith  |first2=R.E.
  |last3=Randall  |first3=M.D.
  |publisher=American Society for testing and Materials (ASTM)
  |id=ASTM Special Technical Publication 494
  |isbn=978-0-8031-0073-2
  |url=http://www.astm.org/DIGITAL_LIBRARY/STP/SOURCE_PAGES/STP494_foreword.pdf
}}</ref>

<ref name="_2">{{Cite web
  |title=Properties of HY-100 Steel for Naval Construction
  |url=http://dtic.mil/dtic/tr/fulltext/u2/a209135.pdf
|archive-url=https://web.archive.org/web/20150521012838/http://dtic.mil/dtic/tr/fulltext/u2/a209135.pdf
|url-status=dead
|archive-date=May 21, 2015
}}</ref>

<ref name="AD-A233 061">{{Cite web
  |title=Strength and Fracture Characteristics of HY-80, HY-100, and HY-130 Steels Subjected to Various Strains, Strain Rates, Temperatures, and Pressures
  |id=AD-A233 061
  |date=September 1987
  |last=Holmquist  |first=T.J
  |ref={{SfnRef|AD-A233 061}}
  |url=http://apps.dtic.mil/dtic/tr/fulltext/u2/a233061.pdf
|archive-url=https://web.archive.org/web/20150521011609/http://www.dtic.mil/dtic/tr/fulltext/u2/a233061.pdf
|url-status=live
|archive-date=May 21, 2015
}}</ref>

<ref name="_4">{{Cite web
  |title=Tensile Properties of HY80 Steel Welds Containing Defects Correlated With Ultrasonic And Radiographic Evaluation
  |date=April 1972
  |url=https://app.aws.org/wj/supplement/WJ_1972_04_s198.pdf
}}</ref>

<ref name="_5">{{Cite web
  |title=Alloy Steels HY80
  |url=http://www.suppliersonline.com/propertypages/HY80.asp
}}</ref>

<ref name="AASteel">{{Cite web
  |title=HY 80 / 100 (MIL-S-16216)
  |publisher=American Alloy Steel
  |url=https://www.aasteel.com/hy-80-100/
}}</ref>

<ref name="MIL-S-16216">{{Cite web
  |title=Military Specification: Steel Plate, Alloy, Structural, High Yield Strength (HY-80 and HY-100)
  |id=MIL-S-16216
  |date=19 June 1987
  |url=http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-S/download.php?spec=MIL-S-16216K.011494.PDF
}}</ref>

<ref name="MIL S-21952">{{Cite web
  |title=Military Specification: Steel (HY-80 and HY-100) Bars, Alloy
  |id=MIL S-21952
  |date=5 June 2003
  |url=http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-S/download.php?spec=MIL-S-21952D_NOTICE-1.038234.pdf
}}</ref>

<ref name="FAS">{{Cite web
  |title=Run Silent, Run Deep
  |date=8 December 1998
  |publisher=Federation of American Scientists
  |work=Military Analysis Network
  |url=http://fas.org/man/dod-101/sys/ship/deep.htm
}}</ref>

<ref name="Naval Engineers Journal">{{Cite journal
  |title=An Evaluation of HY-80 Steel as a Structural Material for Submarines
  |journal=Naval Engineers Journal
  |volume=77|  issue=1
  |pages=29–44
  |date=February 1965
  |last1=Heller  |first1=Captain S. R. Jr.
  |last2=Fioriti  |first2=Ivo
  |last3=Vasta  |first3=John
  |doi=10.1111/j.1559-3584.1965.tb05644.x
  }}</ref>

<ref name="Courant, 1991">{{Cite news
  |title=Subs' Hull Problems Resurfacing
  |newspaper=Hartford Courant
  |date=8 September 1991
  |author=Lyn Bixby
  |url=http://articles.courant.com/1991-09-08/news/0000212322_1_steels-seawolf-submarine
}}</ref>

<ref name="Rickover Effect">{{Cite book
  |title=The Rickover Effect
  |year=2002
  |last=Rockwell  |first=Theodore
  |author-link=Theodore Rockwell
  |publisher=iUniverse
  |isbn=978-0-595-25270-1
  |page=316
  |url=https://books.google.com/books?id=U4kjnYL7-igC&q=thresher+HY-80&pg=PA316
}}</ref>

<ref name="Polmar, Thresher">{{Cite book
  |title=The Death of the USS Thresher
  |year=2004
  |last=Polmar  |first=Norman
  |author-link=Norman Polmar
  |publisher=Globe Pequot
  |isbn=978-0-7627-9613-7
  |pages=1–2
  |url=https://books.google.com/books?id=-nHkGUoSk2MC&q=thresher+HY-80&pg=PT11
}}</ref>

<ref name="_8">{{Cite web
  |title=HY-80 Steel Fabrication in Submarine Construction
  |date=21–22 March 1960
  |publisher=[[Bureau of Ships|Bu. Ships]]
  |url=http://www.dtic.mil/dtic/tr/fulltext/u2/258306.pdf
|archive-url=https://web.archive.org/web/20150521012155/http://www.dtic.mil/dtic/tr/fulltext/u2/258306.pdf
|url-status=dead
|archive-date=May 21, 2015
}}</ref>

<ref name="ArcelorMittal">{{Cite web
  |title=Armor: Steels for National Defense
  |publisher=ArcelorMittal USA
  |url=http://www.arcelormittalna.com/plateinformation/documents/en/Inlandflats/ProductBrochure/ARCELORMITTAL%20ARMOR.pdf
}}</ref>

<ref name="Kaufman, 38">{{cite book
  |title=Fracture Resistance of Aluminum Alloys: Notch Toughness, Tear Resistance
  |publisher=ASM International
  |first=John Gilbert  |last=Kaufman
  |year=2001
  |page=38
  |url=https://books.google.com/books?id=nd9_99j0oioC&pg=PA38
  |isbn=978-0-87170-732-1
}}</ref>

<ref name="Yayla, 2007" >{{Cite journal
  |last=Yayla  |first=P
  |date=Summer 2007
  |title=Effects of Welding Processes on the Mechanical Properties of HY80 Steel Weldments
  |journal=[[Materials & Design]]
  |volume=28
  |issue=6
  |pages=1898–1906
  |doi=10.1016/j.matdes.2006.03.028
}}</ref>

}}

{{US submarine classes after 1945}}

[[Category:Steel alloys]]
[[Category:Submarine components]]