JFE TECHNICAL REPORT

No. 2 (Mar. 2004)

Steel Products for Shipbuilding

SUZUKI Shinichi*1MURAOKA Ryuji*2OBINATA Tadashi*3ENDO Shigeru*4HORITA Tomoo*5OMATA Kazuo*6

Abstract: control process) steel plates for high heat input welding
Product designs and properties of 6 steel products for container ships, which contribute to improved pro-
for shipbuilding are described. They are new TMCP ductivity by greatly reducing welding working time, and
(thermo-mechanical control process) steel plates, weld- LP steel plates (longitudinally profiled plates, also called
able with high heat input, for container ships and LP taper plates), new anti-corrosion steel plates for crude
(longitudinal profile) plates, both contribute to the oil tankers, NAC5, which contribute to higher perfor-
increase in productivity at shipyards through the large mance in ships through improved corrosion resistance,
reduction of welding time, anti-corrosion steel plates for and clad steel plates for chemical tankers. Tubular prod-
crude oil tankers NAC5 which contribute to high perfor- ucts include JFE-MARINE-COP for crude oil tankers,
mance of ships from the viewpoint of corrosion, cladded which improves corrosion wear performance in onboard
steel plates for chemical tankers, anti-corrosion pipes, oil receiving pipes used in loading and unloading crude
JFE-MARINE-COP, used in crude oil tankers for load- oil. Among shape steels, JFE Steel has developed TMCP
ing and unloading crude oil, and shapes for shipbuild- technologies for shapes for shipbuilding which provide
ing which are produced using TMCP to realize weldabil- weldability equal to that of plates.
ity as good as steel plates.
2. Steel Plates
1. Introduction
2.1 Steel Plate for High Heat Input Welding
In recent years, the shipbuilding industry has energet-
EWEL
ically promoted high performance of ships and improved
productivity in construction in response to vessel diver- With the increase in long distance freight transpor-
sification (trend toward exclusive-use ships). In the pro- tation in recent year, the size of container ship has been
cess, the industry has also pointed out a variety of devel- enlarged rapidly, and even 8 000 TEU (TEU: twenty-
opmental needs related to steel products, resulting in the feet equivalent unit) class container ships are being con-
creation of new technologies and new products. structed recently. To construct such large-scale con-
This report describes the product design concepts and tainer ships, high strength and thick steel plates are used,
properties of the following 6 products which were devel- such as 390 N/mm2 class yield strength and maximum
oped by JFE Steel in response to these needs. In the field thichness of 65 mm or more. For welding of these thick
of plate, they include new TMCP (thermo-mechanical plates, 1-pass vertical electro gas arc welding (EGW),

Originally published in JFE GIHO No. 2 (Nov. 2003), p. 3744

*1 *4
Senior Researcher Manager, Senior Researcher Manager,
Plates & Shapes Res. Dept., Plates & Shapes Res. Dept.,
Steel Res. Lab., Steel Res. Lab.,
JFE Steel JFE Steel

*2 *5
Senior Researcher Deputy Manager, Staff Manager,
Plates & Shapes Res. Dept., Products Design & Quality for Steel Products Dept.,
Steel Res. Lab., West Japan Works,
JFE Steel JFE Steel

*3 *6
Staff Deputy General Manager, General Manager,
Products Design & Quality for Steel Products Dept., Plate Business Planning Dept.,
West Japan Works, JFE Steel
JFE Steel

41
 Steel Products for Shipbuilding

Thickness : 80 mm, Heat input : 640 kJ/cm

High cooling rate
(1) Low Cep alloy design by super-OLAC
Ave.
300
Each

Absorbed energy at 40C (J)

(2) Control of grain size Pinning by
in HAZ optimum sized TiN

200
(3) Control of microstructure ACR control
in HAZ grain Microallying techonology

Fig. 1 Concept of developing high strength steel plates, 100

Spec.
EWEL, for high heat input welding
(41 J)

which has high welding efficiency, has been applied, and 0

FL HAZlmm HAZ3mm HAZ5mm
the heat inputs in these welding reach ultra-high level
exceeding 400 kJ/cm. This high heat inputs cause the Notch position
remarkable coarsening of microstructure in heat affected Fig. 2 Charpy impact energy of welded joint of EH40
zone (HAZ), and greatly decrease the toughness of plate
welded joint. Furthermore, in order to meet the require-
ments of higher strength and increased thickness, it is Figure 2 shows joint toughness in the case of 1-pass
necessary to increase the carbon equivalent (Ceq) and/or EGW of YP390 N/mm2 class steel plates with a thick-
to add alloying elements, but this causes deterioration in ness of 80 mm. High heat input welding steel EWEL has
weldability and the toughness of welded joint. excellent joint toughness even at 40C.
To resolve these problems, JFE Steel developed a F class high strength steel and low temperature ser-
high heat input welding technology based on the techni- vice steel for hull structure, in which excellent low tem-
cal concept shown in Fig. 1, resulting in steel plates for perature toughness is required, were also developed and
high heat input welding, EWEL, which is used in large- commercialized based on the same concept. In the weld-
scale container ships and other applications.1) In EWEL, ing of these steels, the heat input is not always high, but
excellent base metal properties and welded joint proper- in the case of one side one pass FAB (flux asbestos back-
ties are realized by the combination of three concepts: ing) welding and FCB (flux cupper backing) welding,
(1) Low Carbon Equivalent Alloy Design of the Base the equivalent heat input relative to the plate thickness
Metal is high, and excellent low temperature toughness is also
By applying the high cooling rate attained by JFE required. Table 1 shows an example of the welded joint
Steels Super-OLAC (on-line accelerated cool- toughness of a steel plate for low temperature service.
ing) technology, the optimum composition design Joints welded by FAB process (heat input: 88 kJ/cm)
is prepared considering the strengths of both base show superior impact toughness.
metal and welded joint, and yield strength of the As is mentioned above, outstanding properties have
390 N/mm2 class is achieved at the same Ceq level been realized in the steel for high heat input weld-
as in YS355 N/mm2 class steel, and also, the upper ing EWEL by using the Super-OLAC and JFE
bainite, which is detrimental to the toughness of Steels advanced microalloying composition design to
welded joint, is suppressed. control the microstructure of the base material and HAZ.
(2) Control of Grain Size in HAZ These developed steels have received an excellent evalu-
By using optimum TiN, refinement of the grain size ation from customers and have been adopted in numer-
in the HAZ is achieved. ous large-scale container ships, LPG ships, and others,
(3) Control of Microstructure in HAZ Grain and increasing demand is expected. It should be noted
Nucleation of intra-granular ferrite is accelerated that JFE Steel has also applied the development concept
by applying ACR (atomic concentration ratio) con- of high heat input welding technology EWEL to the
trol, which is JFE Steels original technology, and steels for bulding structure, and YS325440 N/mm2
other microalloying technologies. class steels were developed and commercialized. 2)

Table 1 Charpy impact energy of KL37 plate

Charpy impact energy at 55C (J)

Thickness Welding Heat input
Grade Fusion line HAZ l mm HAZ 3 mm
(mm) method (kJ/cm)
Min. Ave. Min. Ave. Min. Ave.
KL37 17 FAB 88 70 128 74 116 264 289

42 JFE TECHNICAL REPORT No. 2 (Mar. 2004)

 Steel Products for Shipbuilding

2.2 New Anti-Corrosion Steel for Crude Oil Conventional

Tankers NAC5 steel

As illustrated in Fig. 3, the area under the upper deck

NAC5
in crude oil tankers is exposed to mixed atmosphere of Base metal
exhaust gas and H2S volatilized from the crude oil. As
this area is also subject to cyclic condensation and evap-
NAC5
oration of sulfur during day and night, a type of corro- Weld metal
sion peculiar to the under deck area, called vapor space
0.7 0.8 0.9 1
corrosion, occurs. The average corrosion rate in vapor
space is about 0.1 mm/y. However, considering the life Ratio of corrosion rate

of a crude oil tanker to be approximately 20 years, the Fig. 4 Corrosion test results of NAC5 and conventional
possibility of deck plate replacement increases. Without steel (Gas : CO2-SO2-H2S-O2-N2, 720 h)
replacement of deck plate which cost is very expensive,
the resulting ship reliability may be lower.
JFE Steel developed a new anti-corrosion steel for
crude oil tankers, NAC5 (New Anti-Corrosion No.5)
that can extend the service life of deck plates by approx-
Conventional
imately 5 years, with the use of ship primer. NAC5 also steel
has excellnt weldability, which is an essential property
in shipbuilding materials. JFE Steel produces YS235
355 N/mm2 class NAC5 plates and shapes in A and D
grade.
NAC5
Figure 4 shows a cyclic corrosion test results simu-
lating the corrosion environment under the upper deck
plate with NAC5 and conventional steel without shop 0.2 0.4 0.6 0.8 1
primer. As for NAC5 without shop primer, the corrosion
Ratio of exfoliation rate
rates of both base metal and weld metal were approxi-
Fig. 5 Corrosion test results of cross cut specimens
mately 10% lower than those of the conventional steel, coated by shop primer
which demonstrates the improved corrosion resistance. A
cyclic corrosion test was also performed with cross-cut
7
type specimens to investigate the life of the shop primer,
6 Plate thickness : 20 mm
with the results as shown in Fig. 5. Since the exfoliation Conventional
rate of NAC5 was reduced approximately 40% in com- 5 steel
Probability (%)

parison to the conventional steel, shop primer remain- 4 5y

ing life can be extended by about two times with NAC5.
3
Moreover, because the Ceq of NAC5 is reduced to the
2
same level as that of the conventional steel by applying
NAC5
TMCP technology, conventional welding consumables 1
Shop primer
can be used, and the NAC5 has weldability equivalent to 0
0 5 10 15 20 25 30 35
the conventional steel.
Ship age (y)
Fig. 6 Estimation of life of deck plate

Vapor space Inert gas

Figure 6 shows an estimation of the service life of

deck plates using NAC5 in comparison with the conven-

Ex.8%O2
14%CO2
tional steel based on an investigation of corrosion dam-
H2S
0.03%SOx Crude oil
age in the under surface of upper deck plate by Yama-
Bal.N2 moto.3) In the evaluation of 1% probability of deck plate
replacement, the life of NAC5 deck plate with shop
primer was estimated to be approximately 5 years longer
than that of the conventional steel.
Fig. 3 Illustration of corrosion under upper deck plate in It is also considered possible to reduce maintenance
crude oil tanker costs and enhance ship reliability by using NAC5.

JFE TECHNICAL REPORT No. 2 (Mar. 2004) 43

 Steel Products for Shipbuilding

Weld Weld
seam
2.3 LP Steel Plates for Shipbuilding4-6) seam

LP steel plates are plates in which the thickness is

changed continuously in the longitudinal direction, and
are high performance plates which make it possible to
reduce the number of welds and steel weight in struc-
tures.
Figure 7 shows typical profiles of LP plates used (a) Normal (b) Lengthwise differential (c) LP plate
plate thickness plate
in shipbuilding. LP1 is an LP plate in which the thick-
ness is changed longitudinally in one direction, while Fig. 8 Example of an omission of weld seams and reduc-
tion of weight by using LP plate
LP2 has isometric parts at the head and tail ends. A uni-
form plate thickness for welded joints can be obtained
Upper deck Trans-bulk head
by specifying these isometric parts. In LP7 and LP8, the
Cargo hold
plate thickness is changed longitudinally in two steps
in the same direction. These thickness differences are
imparted in the LP plate manufacturing process by con-
tinuously changing the roll gap during rolling.
The effect of applying LP plates in shipbuilding is
illustrated in Fig. 8, which shows the trans-bulkheads
of a bulk carrier as an example. In trans-bulkheads, it
is necessary to reduce the plate thickness from the ship Bottom plate

bottom to the top. Conventionally, a large number of Fig. 9 Examples of typical application of LP plate for
plates of varying thicknesses were joined by welding, shipbuilding
as shown in Fig. 8 (a), to reduce the plate thickness as
Sep. 1993 Sep. 1996 May 2000 Jan. 2001
stress decreases with the aim of reducing weight. The
Taper ratio
number of welds can be reduced by applying differen- 4/1000 8/1000
Taper ratio : Thickness reduction per 1000 mm length
tial thickness plates in these parts, as shown in Fig. 8 (b). 25 000
Differential thickness plates are plates having two dif-
20 000
ferent thickness in the longitudinal direction. In con-
Plate delivered (t)

trast, LP plates are tapered in the longitudinal direction. 15 000

Use of LP plates, as shown in Fig. 8 (c), enables further
10 000
reductions in steel weight and in the number of joints.
Figure 9 shows an example of typical locations 5 000

where LP plates are applied in vessels. In addition the 0

trans-bulkhead, LP plates can be used in a number of 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

other parts, such as the upper deck, bottom plates, etc. Year

Under rules for classification of ships, it is possible to Fig. 10 Supply record of LP steel plates for shipbuilding
manufacture LP plates of 40 k (A, B, D grade) and 50 k
(A, D, E grade) class steel for shipbuilding.
Figure 10 shows JFE Steels LP plate supply record more recently, bi-directional LP plates (1996), 8/1000
since 1993 and improvements in the LP plate profile. Ini- taper ratio LP plates (maximum taper ratio:8 mm/m;
tially, only uni-directional LP plates were available, but 2000), and 2-step LP plates (2001) have been developed.
Between 1993 and 2002, JFE Steel shipped more than
58 000 t of LP plates, and has steadily increased its sup-
t1 t2 t1 t2 ply record since these plates were first used in shipbuild-
L1 L1 L2 L3 ing in 1993. In particular, use of LP plates has increased
dramatically since 1999, showing that these plates are
(a) LP1 (b) LP2
now widely recognized as materials which reduce the
number of welds and steel weight when applied in ship-
t1 t3 t1 t2 t3
t2 building, contributing to reduced construction costs. In
L1 L2 L3 L1 L2 L3 L4 L5 one actual example, approximately 2 500 t of LP plates
were used in a 170 000 t class bulk carrier, achieving a
(c) LP7 (d) LP8
700 m reduction in the length of welds and 218 t reduc-
Fig. 7 Various thickness profiles of LP plates tion in the weight of steel consumed.

44 JFE TECHNICAL REPORT No. 2 (Mar. 2004)

 Steel Products for Shipbuilding

Table 2 Corrosion resistance of stainless clad steel

2.4 Clad Steel for Chemical Tankers
Pitting
Clad steel is a type of composite steel plate in which Intergranular SCC (U-bend)
corrosion
stainless steel plates or other material (called cladding or corrosion Boiling
JIS G0578
clad material) is bonded to one or both sides of a carbon JIS G0575 20%NaCl
50C, 24 h
16 h, 1t-bend 500 h, 8t-bend
steel or low alloy steel plate (base material). Accord- (g/m2h)
ingly, while clad plates possess the strength required 27.1
in structural members (function of base material), they KA316L 24.1 No crack No crack
simultaneously have corrosion resistance or other func- Ave. 25.6
tions (function of cladding), and are therefore a high (KA : Mild steel for shipbuilding)
performance material with properties which would be
difficult to realize in a single material.
Table 3 Corrosion rate in phosphoric and sulfuric acids
Recent years have seen an increasing number of cases
in which stainless clad plates were used as hull mate-
rial for chemical tankers (Fig. 11). The cladding (stain- Phosphoric acid 98%sulfuric acid
less steel) of stainless clad plates for chemical tankers is 75C 50C
(mm/y) (mm/y)
required to provide corrosion resistance against numer-
ous kinds of chemical cargos, while the base material 0.160 0.25
KA316L
(carbon steel) must have excellent mechanical properties 0.158 0.25
capable of withstanding high specific gravity and severe Phosphoric acid : 44%P2O58.3%SO421.6%Fe3
loading conditions. Furthermore, because stainless steel 0.8%Al31.3%F0.2%Cl
for bulkhead use is frequently welded during construc-
tion without removing the cladding, bonding strength
Table 4 Tensile test and V-notch Charpy impact test
between the base material and cladding is also required. results
Thus, among the applications of clad plates, chemical
tankers have extremely high performance requirements. Tensile test* Impact test**

Although various manufacturing processes can be KA316L YS TS El vE20C

used to produce clad plates, JFE Steel uses the rolling t(93)mm (MPa) (MPa) (%) (J)
cladding process. The following describes some of the Direction : T
276 473 34 82
outstanding properties of rolled clad plates.
* Full thickness, W25 mm, Gauge length200 mm
The results of an accelerated corrosion test of the ** 3/4 size V-notch Charpy impact test of base metal
cladding of clad steel plates are shown in Table 2. Pit-
ting corrosion resistance, intergranular corrosion resis-
tance, and SCC resistance all display the same level of
Table 5 Bend test results
performance as solid stainless steel materials. Table 3
shows the results of an evaluation of corrosion resis- Bend test*
tance against crude phosphoric acid and sulfuric acid, KA316L Face bend Root bend Side bend
r1.5 t r2.0 t r2.0 t
which are representative examples of particularly strong t(93)mm
chemicals among actual cargos. Although the test tem- Direction : T Good Good Good
*JIS G 0601

6 000
peratures were set high, at 75C and 50C, respectively,
5 000 for the accelerated corrosion test, satisfactory corrosion
Quantity of order (t)

4 000
resistance was observed.
As an evaluation of mechanical properties, Table 4
3 000 shows the results of a full thickness tensile test of the
2 000
clad steel and Charpy impact test of the carbon steel
base metal, and Table 5 shows the results of various
1 000 bending tests. Sufficient properties for use as material
0 for hull construction were observed in all the test results.
1990 1992 1994 1996 1998 2000 2002 Rolled clad steels are considered capable of meeting
Year the requirements of high performance materials, as out-
Fig. 11 Change in quantity of order of clad steel plates lined above, including those of further growth in demand
for chemical tankers in the future.

JFE TECHNICAL REPORT No. 2 (Mar. 2004) 45

 Steel Products for Shipbuilding

1.6
3. Steel Pipes JFE-MARINE-COP
1.0 Cr (High C)

Corrosion rate (mm/y)

1.2 STPY 400
3.1 Cargo Oil Pipe for Crude Oil Tankers
JFE-MARINE-COP 0.8

Because the onboard piping of oil tankers which is 50C 300 h

used to load and unload crude oil and seawater, called 0.4 Synthetic sea water
cargo oil pipes, is exposed to a seawater environment
containing crude oil on both the outer and inner sur- 0
faces, painted 400 MPa class steel pipes (STPY 400) or Base metal Seam welded joint

Cr-added cast iron pipes are normally used. Moreover, Fig. 12 Corrosion rate of JFE-MARINE-COP in synthetic
in addition of resistance to seawater corrosion, cargo oil sea water in comparison with those of 1% Cr,
high C steel and STPY 400
pipes must also have corrosion wear resistance. For this
application, the company developed and brings to mar-
ket a seawater-resistant pipe, JFE-MARINE-COP, which
has both the equivallent weldability of 400 MPa steel
pipe and the corrosion resistance and corrosion wear
resistance of cast iron. The following describes the fea-
tures and service performance of JFE-MARINE-COP.

3.2 Features of JFE-MARINE-COP

Table 6 shows the chemical composition and manu-
facturing process of JFE-MARINE-COP. Cu, Ni, and Cr
are added to improve seawater corrosion resistance, and
Ca is added to prevent preferential corrosion of welds.
In the manufacturing process, controlled rolling and JFE Fig. 13 Cross sections of the MARINE-COP after 3 years
Steels on-line accelerated cooling device, Super-OLAC, of service as a cargo oil tank in the BENETIA
are applied to secure a homogeneous bainite structure.
The corrosion rate in artificial seawater at 50C tends
35
to decrease as Cr addition is increased. As shown in
30 JFE-MARINE-COP
Fig. 12, JFE-MARINE-COP with 1% Cr addition shows
1.0 Cr (High C)
a corrosion rate of around 50% that of 400 MPa class
Cracking area ratio (%)

25

steel without Cr addition. 20

Figure 13 shows the appearance of cross-sections of
15
a JFE-MARINE-COP pipe used for 3 years as a cargo
10
oil pipe in an actual vessel (named the Benetia). Virtu-
ally no thickness reduction attributable to general corro- 5
sion or local corrosion can be observed in either the pipe 0
base metal or weld metal. This is a result of suppression 20 0 20 40 60 80 100
of preferential corrosion of the HAZ by the homoge- Testing temperature (C)
neous microstructure of the base metal/HAZ and addi- Fig. 14 Results of weld cold cracking evaluation test or
tion of Cu, Ni, and Ca. Tekken test of JFE-MARINE-COP in comparison
Further, no weld cold cracking was observed in low with 1% Cr, high C steel
carbon JFE-MARINE-COP in a y-groove weld crack-
ing test (Tekken test), even without preheating (Fig. 14). Various welding consumables have been developed
through joint research with Kobe Steel, Ltd. as consum-
ables for circumferential welding of JFE-MARINE-COP,
Table 6 Chemical composition and manufacturing pro- including manual welding (SMAW) with the brands
cess of JFE-MARINE-COP
mentioned below. Satisfactory corrosion resistance and
Chemical composition corrosion wear resistance have been confirmed in welds
C Si Mn Process using these consumables.
Others
(mass%) (mass%) (mass%)
(1) LBK-52 for SMAW use
0.06 0.25 1.0 Cu, Ni, Cr Super-OLAC (2) MGK-52 for GMAW use
(3) TGSK-52 for TIG use

46 JFE TECHNICAL REPORT No. 2 (Mar. 2004)

 Steel Products for Shipbuilding

3.3 Manufacturing Results 4.2.2 Available standards

JFE-MARINE-COP can be manufactured in outer NKBS has received manufacturing certifica-
diameters from 76.3 mm to 1 016 mm at JIS (Japanese tion from major ship class societies for products up to
Industral Standards) STPY 400 and STPY 500 equiva- DH36, and JFE Steel is certified for mild steel and high
lent strength levels. JFE Steel currently produces around tensile steel up to EH40 applying TMCP technology,
5 000 t/y for customers inside and outside of Japan. as introduced in the following section. JFE Steel has
also received certification to manufacture low tempera-
ture service steels with guaranteed impact properties at
4. Steel Shapes
60C for use in liquefied gas carriers and similar
applications.
4.1 Shapes for Shipbuilding
JFE Steel and its group company, NKK BARS & 4.3 Manufacturing Processes for Steel Shapes
SHAPES (NKBS) have developed products and pro- for Shipbuilding
cesses for shapes for use in ship hulls since entering the
4.3.1 Rolling process for steel shapes for ship-
shape steel business and were the first in Japan to man-
building
ufacture representative shapes for shipbuilding such as
unequal leg and unequal thickness angles (NAB) and Because shapes for shipbuilding, as represented
bulb plates (BP). JFE Steel has established its leadership by NAB, have an asymmetrical cross-section in the lat-
in shapes for shipbuilding by introducing equipment eral and vertical directions, both the material prop-
such as an exclusive-use shot blasting device for shapes erty design, as mentioned above, and the manufactur-
and developing the first water cooling type TMCP tech- ing design in the hot rolling process are important. JFE
nology for shapes. The following introduces JFE Steels Steel has realized high accuracy caliber rolling with 2-hi
products and manufacturing technologies for shapes for rolls by applying FEM analysis in addition to the caliber
shipbuilding. design technology which the company has accumulated
over many years. The forming process in caliber rolling
4.2 Classification of Steel Shapes for is shown in Fig. 15 for NAB as a representative product.
Shipbuilding
4.3.2 TMCP for steel shapes for shipbuilding
4.2.1 Cross-sectional classification of steel
JFE Steel has developed and applied non-water
shapes
cooling and water cooling type TMCP technologies
The main shapes for shipbuilding produced by JFE which meet the requirements of low Ceq high toughness,
Steel and NKBS are shown in Table 7. The JFE Steel high strength steels with excellent weldability. TMCP
Group has an extensive line of shape products for ship- technology was first developed as a plate manufacturing
building, including NAB, BP, unequal leg angles (ABS), process. However, when applied to shape production, the
flat bars (FB), and equal leg angles (AB). As available
sizes, the JFE Steel Group also produces shapes with Bloom BD mill R1 mill
intermediate thicknesses outside JIS section dimensions,
contributing to greater freedom in ship hull design and
optimum design. R2 mill F mill

Fig. 15 Kaliber rolling process of NAB

Table 7 Dimensions of shapes for shipbuilding

No. Section dimensions Unit weight, Moment of

Shape of (mm) W inertia, IX Brand
size AB t1 t2 (kg/m) (cm4)
NAB 28 200 90 450125 8 12.5 1418 21.8 60.8 1 120 16 600 JFE
BP 4 180 250 9.5 12 16.5 29.9 671 2 360 JFE
ABS 6 100 75 150 90 7 12 9.3 21.5 118 619 NKBS
30 20 20 150150 3 14 0.9 41.9 0.4 1 090 NKBS
AB
7 175175 250250 12 35 31.8 128.0 1 170 9 110 JFE
FB 108 25 150 4.5 25 0.9 29.4 NKBS

JFE TECHNICAL REPORT No. 2 (Mar. 2004) 47

 Steel Products for Shipbuilding

Table 8 Available TMCP shapes approved by certifying organization

Standard Classification of ships Chemical composition

YP
(kgf/mm2) Grade NK AB LR NV BV KR CR Steel Ceq (LR)

A, D Si-Mn
32, 36
E Si-Mn
0.36
A, D Nb
40
E Nb
: JFE has the general approval

devices are designed to enable temperature control

OLAC Flange cooling
considering the temperature characteristics of each
Furnace
BD mill part of the rolled material.
(3) Available Standards for TMCP
F mill R2 mill R1 mill JFE Steel has received certification to manufacture
low Ceq high strength steels by TMCP from leading
Fig. 16 Location of water cooling equipment certifying organizations, as shown in Table 8.
5. Conclusions
rolling conditions are subject to more difficult restric-
tions than with plates due to the complexity of the cross- In response to the requirements of the shipbuilding
sectional profile of shape steel and features peculiar to industry, JFE Steel has developed and commercialized
rolling with caliber rolls. Examples of these problems advanced products such as water cooled TMCP steels
include the difficulty of securing homogeneous proper- which have now become world-standard products. In the
ties and dimensional shape accuracy in cross-sections future, JFE Steel Group will continue to develop Only
containing differing thicknesses and the load capacity 1 and No. 1 products which meet the needs of the ship-
limitations of caliber rolls. Accordingly, JFE Steel suc- building industry, for example, by contributing to higher
cessively developed and applied a proprietary non-water productivity and higher performance, including ship col-
cooling type TMCP technology for steel shapes, fol- lision safety, corrosion resistance, and fatigue resistance.
lowed by the first water cooling type TMCP technology Through the products mentioned above, JFE Steel will
for shapes. contribute to the development of society and protection
(1) Water Cooling Type TMCP for Steel Shapes of the global environment.
In rolling asymmetrical NAB, the temperature of the
flange is higher than that of the web during rolling References
and in finishing due to the cross-sectional profile (the 1) Omata, Kazuo.; Yoshimura, Hiroshi.; Yamamoto, Sadahiro.
flange is thick, whereas the web is thin). Accordingly, The leading high performance steel plates with advanced
in the TMCP process for NAB, uniform strength manufacturing technologies. NKK Technical Report. no.179,
2003, p.5762.
properties are obtained through the entire cross- 2) Kimura, Tatsumi; Hisada, Mitsuo; Fujisawa, Seiji; Yokoyama,
section by securing sufficiently rollimg reducing in Yukio; Katori, Shuji. Steel plates for architectural construc-
the low temperature region of Austenite and/or in tion with excellent toughness in large heat input welded joints.
Kawasaki Steel Giho. vol.34, no.4, 2002, p.158163.
subcritical regin for the web and applying accelerated 3) Yamamoto, Norio. Recent research results of corrosion dim-
cooling after rolling. inution and its effect on struvture strength. Structure symp.
(2) Cooling Equipment for Shape Steel TMCP 2001-12-14, p.315.
4) Yuge, Yoshinori; Hori, Toshifumi; Nishida, Shun-ichi. Devel-
The arrangement of the cooling equipment for opment of manufacturing technologies of longitudinally pro-
TMCP for shipbuilding steel shapes is shown in filed steel plates for ships and bridges. Kawasaki Steel Giho.
Fig. 16. For accelerated cooling after rolling, an vol.30, no.3, 1998, p.137141.
5) Tanigawa, Osamu; Kohriyama, Takeshi; Amano, Keniti;.
OLAC device is installed after the finishing roll- Development of high performance steel plates in terms of reli-
ing mill, while flange cooling devices are installed in ability and economy of steel structures. Kawasaki Steel Giho.
the guides at the intermediate and finishing mills to vol.32, no.3, 2000, p.198204.
6) Kusuhara, Yuuji. Recent progress in plate rolling technol-
improve homogeneity in all parts of the product and ogy. no.159 & 160 Nishiyama Kinen Gijutsu Kouza. 1996,
enhance TMCP efficiency. The respective cooling p.118.

48