This includes analytical and laboratory studies to validate
physically the analytical predictions of separate elements of the
INCO continued the development of improved “NiCuAge” steel for
improved weldability and low-temperature toughness in heavy section plates and
forgings and, in 1972, marketed the steel designated IN-787 for offshore
platforms and ship hull plates. The American Society for Testing and Materials
(ASTM) Standard Specification A710, Grade A, based on IN-787 steel, was issued
in 1975. Armco Steel Corporation produced a plate to ASTM A710, Grade A, under
the trade name “NI-COP” steel.
The primary reason for preheat in the welding of High Yield
Strength (HY)-80 and HY-100 steels is to mitigate underbead cracking (hydrogen
related) in the hard, martensitic heat-affected zone (HAZ). The Navy
High-Strength Low-Alloy (HSLA)-80, an optimized version of ASTM A710, Grade A
steel, is a ferritic steel. The microstructure of the quenched and aged
HSLA-80 plate product is generally an acicular ferrite. Ferritic steels are
widely used in civil construction because of their excellent weldability.
In 1981, the Navy HSLA Steels Exploratory Development Program
was initiated at David Taylor Research Center (DTRC), with ASTM A710, Grade A
selected as the primary candidate. Because of the positive results emanating
from the project, ASTM A710, Grade A, Class 3 steel was authorized as
substitute for HY-80 steel on a production trial basis in CVN 71 in selected
noncritical, nonwetted areas in 1983. Upon completion of the evaluation of
ASTM A710 for Navy requirements, the modifications to ASTM A710 were
incorporated in MIL-S-24645(SH), 4 September 1984, for HSLA-80 steel plate,
sheet, and coil. The Naval Sea Systems Command (NAVSEA) certified HSLA-80 for
surface ship construction and repair in thickness up to 1-1/4 inch, 16
February 1984. The evaluation of HSLA-80 properties, welding, and structural
performance demonstrated that the very-lowcarbon, copper
precipitation-strengthened steel met the requirements of HY-80 steel and was
readily weldable with no preheat (32°F minimum) using the same welding
consumables and processes as those used for HY-80 steel fabrication. Since
1985, HSLA-80 steel has been used in CG 47 Class construction in increasing
tonnage, in CVN 72 and follow-on ships, and in DDG 51 Class, LHD 1 Class, LSD
41 Class, and FFG 7 Class modifications.
Following the HSLA-80 program, a research and development
(R&D) project commenced in 1985 to establish the feasibility of HSLA-100
steel as a replacement for HY-100 to reduce fabrication costs. A contract to
AMAX Materials Research Center in 1985 initiated the laboratory alloy
development for HSLA-100 steel. The objective for HSLA-100 was to meet the
strength and toughness of HY-100 steel but to be weldable without the preheat
requirements of HY-100, using the same welding consumables and processes as
those used in welding HY-100. The project for the development of HSLA-100
steel in the laboratory alloy design phase used the principles of very low
carbon, copper-precipitation strengthened steel successful for HSLA-80.
Fracture-process research on HSLA-80 steel indicated that a
uniformly small grain size and wider distribution of small carbides would
reduce the fracture transition temperature. In fact, HSLA-80 plates of 1-inch
gage and less were typically a fine-grained, acicular ferrite microstructure
with widely dispersed fine carbides and showed excellent low-temperature
toughness. The aim of HSLA-100 alloy design was to produce a homogeneous,
fine-grained, low-carbon martensite microstructure that dispersed the
secondary transformation products. The alloy development effort to modify
HSLA-80 steel microstructurally used laboratory-scale heats (50 to 100 lb) to
study the effects of Mn, Ni, Mo, Cu, Cr, Cb, and C in hot rolled, quenched,
and aged HSLA-100 plate. Laboratory plates in thicknesses of 1/4, 3/4, 1-1/4,
and 2 inches of HSLA-100 exceeded the minimum strength and impact toughness
Microstructural analysis was conducted to develop composition
ranges for heavy gage plate, meeting the strength and toughness requirements,
where polygonal (“blocky”) ferrite microstructures were not present. A
regression analysis was conducted on the results for plates from 45
experimental melts to develop composition ranges for an Interim Specification
for HSLA-100 Steel Plate. The Interim Specification was then used as the basis
for a trial commercial production of HSLA-100 steel by domestic steel plate
The copper content of HSLA-100 steel is higher than that in
HSLA-80 [for additional precipitation strengthening (maximum solubility of
copper in iron is near 2 percent)], and increased hardenability was achieved
by increases in manganese, nickel, and molybdenum. Nickel, the greatest
increase over that in HSLA-80, lowers upper shelf impact toughness but also
lowers (improves) the impact toughness transition temperature. The
microstructure of HSLA-100 steel was identified by optical and scanning
electron microscopy as low-carbon martensite or a granular, low-carbon
bainite, depending on plate gage—a significantly different metallurgy and
microstructure than the ferritic HSLA-80 steel microstructures.
Certification of HSLA-80 Steel, NAVSEA ltr 05MB/BPS,
Ser 5, dated 16 February 1984.
Coldren, A.P. and T.B. Cox, Development of 100 Ksi Yield
Strength HSLA Steel, DTNSRDC-CR-07-86, July 1986.
Coldren, A.P., T.B. Cox, E.G. Hamburg, C.R. Roper, and A.D.
Wilson, Modification of HSLA-80 Steel to Improve Toughness in Heavy
Sections, DTRC Report SME-CR-04-91, February 1991.
Jesseman, R.J. and G.C. Schmid, “Submerged Arc Welding a
Low-Carbon, Copper Strengthened Alloy Steel,” Welding Journal Research
Supplement, Vol. 62, No. 11, November 1983, pp. 321s–330s.
Jesseman, R.J. and G.J. Murphy, “Mechanical Properties and
Precipitation Hardening Response in ASTM A710 Grade A and A736 Alloy Steel
Plates,” Journal of Heat Treating, Vol. 3, No. 3, June 1984, pp.
Kvidahl, L.G., “An Improved High Yield Strength Steel for
Shipbuilding,” Welding Journal, Vol. 64, No. 7, July 1985, pp.
McCaw, R.L. and R.J. Wong, Welding of HSLA-80 Steel,
DTNSRDC/SME-85/32, June 1985.
Money, K.L., C.H. Shelton, and P.P. Hydrean, “High Strength, Age
Hardening Low-Alloy Steel Plate for Offshore Platforms and Hull Plate,”
1974 Offshore Technology Conference, Paper OTC 1952, 1974.
Montemarano, T.W., R.T. Brenna, T.E. Caton, D.A. Davis, R.L.
McCaw, L.J. Roberson, T.M. Scoonover, and R.J. Wong, Results of the
Evaluation of ASTM A710, Grade A Steel Under the “Certification of HSLA Steels
for Surface Ship Construction Program,” DTNSRDC TM-28-84-17, January
Natishan, M.E., Micromechanisms of Strength and Toughness in
a Microalloyed, Precipitation Hardened Steel, DTRC/SME-89/04, May
Wilson, A.D., “High Strength, Weldable Precipitation Aged
Steels,” Journal of Metals, March 1987, pp. 36–38.