CBMM ASIA - SEAISIseaisi.org/seaisi2017/file/file/presentation-file/Session 10B Paper2.pdf · • Internal slab quality centerline alloy segregation/core unsoundness rating of Mannesmann

CBMM ASIA

OPTIMIZATION AND STABILITY OF PRODUCTION OF

HEAVY GAUGE EH47 SHIP PLATE

DOUGLAS STALHEIMPRESIDENT - DGS METALLURGICAL SOLUTIONS, INC.

CONSULTANT – CBMM TECHNOLOGY SUISSE SA,

GENEVA, SWITZERLAND

SEAISI 2017 CONFERENCE & EXHIBITIONRESORTS WORLD SENTOSA, SINGAPORE

MAY 22-25, 2017

Optimization and Stability of Production of Heavy Gauge

EH47 Ship Plate

1. Introduction

2. Requirements

3. Metallurgical Strategy for Optimization

4. Results

5. Conclusions

Content


EH47 Ship Plate

• Economy, environment and energy are driving forces in container ship design

• Container ship size is increasing as measured by TEU (Twenty-foot (6.1 m) equivalent

unit).

• One TEU – 20 foot x 8 foot x 8 foot cargo container

Introduction

1-TEU cargo container (20’x8’x8’)

6-TEU – 2 – 40 foot containers (white) –

4 total TEU, and 2 – 20 foot containers

(red) – 2 total for a combined 6-TEU.


EH47 Ship Plate

Introduction

Ultra Large

Container

Vessel

(ULCV)


EH47 Ship Plate

Introduction


EH47 Ship Plate

Introduction

Requirement AttributeGrade/Thickness Change to Ensure Hull

Integrity/Safety

Large Size/Hatch

Opening, Complex

Loading,

Longitudinal/

Buckling/Torsional

Strength

Ensure

Hull

Integrity

Grade: EH36/EH40 to EH40/EH47

Thickness: EH40/68 mm to EH47/85 mm

Yield Strength

Increased to EH47,

Potential Weld

Joint Flaws, Plain

Strain State

Ensure

Hull

Safety

Impact Toughness: Energy ≥ 64J @ -40 °C,

center thickness location

Fracture Toughness: CTOD ≥ 0.40 mm @ -

10 °C

Crack Arrest Toughness: Kca ≥ 6000N/mm3/2

(ESSO Test)


EH47 Ship Plate

• Higher strength, improved low temperature cross sectional

toughness in plate thickness from 50-100 mm

Requirements

C Mn P S Si Cu Ni Cr Mo V Nb Ti Als N2 B

≤0.10 ≤2.00 ≤0.030 ≤0.030 ≤0.55 ≤0.35 ≤1.50 ≤0.25 ≤0.08 ≤0.10 ≤0.05 ≤0.02 ≥0.015 NR ≤0.002

ABS EH47 Specification Chemistry Requirements

Typical Specification Mechanical Property Requirements for EH47 or Equivalent

Yield (Mpa)

Tensile (Mpa)

Elongation %

Average Longitudinal/Transverse

Charpy Energy J @ -

40 °C

Weld Tensile

Strength (Mpa)

HAZ Average Charpy J @ -40 °C

CTOD @ -10 °C (mm)

ESSO Toughness, Kca @ - 10

°C (N/mm3/2)

≥ 460 570-720 ≥ 17 ≥ 64/43 ≥ 570 ≥ 64 ≥ 0.38 ≥ 6000

Slab to Plate

Metallurgical

Reduction Ratios

between 3:1 and 5:1


EH47 Ship Plate

• The ESSO Test is a temperature gradient full thickness wide

plate test designed to assess a structural steel fracture

toughness characteristics (brittle crack arrest toughness)

intended for ship hull structure applications.

• Intended for plate thicknesses > 50 mm

• Test the base plate EH47 along with simulation of high

heat input welding of the base plate EH47 to deck plate

EH40 (duplex ESSO test).

• Requirement that must be meet to be qualified for the

construction of ULCV container ships per the societal

ship codes such as Japan’s Nippon Kaiji Kyokai or

commonly known as “Class NK”

Requirements


EH47 Ship Plate

Requirements – ESSO Test Example


EH47 Ship Plate


Shape and size of test specimen

Necessary conditions of

arrest crack position


EH47 Ship Plate


Example of ultra-large

width duplex ESSO test

for welding

Example brittle crack is 207 mm long

Example brittle crack is 270 mm long


EH47 Ship Plate


Equation for Kca calculation

Example of crack length vs.

arrested temperature and Kca


EH47 Ship Plate

• Key Points:

• Create as fine and homogenous as possible cross sectional

grain size/microstructure.

• Creating as high of a volume fraction of high angle (>15°)

grain boundaries will further enhance toughness.

• Desired microstructure for this grade is ferrite/acicular ferrite

(low carbon bainite).

• Low Sulfur/Ca treated clean steel – minimum inclusion levels

• S ≤ 0.003%

• Total O2 < 30 ppm, preferably <20 ppm

• H2 control - < 1 ppm in final as-rolled plate

• Minimum as-cast alloy centerline segregation/microstructural

banding

• Mannesmann Scale rating of 2 or less

Metallurgical Strategy for Optimization


EH47 Ship Plate

• Key Points:

• Slab Dimension - Metallurgical reduction as

large as possible, absolute minimum of 3:1.

• Proper generation of recrystallization

behaviors in roughing and finishing

• Optimization of Nb metallurgy

• Per pass reduction strategy -

CRITICAL

• Critical path in the metallurgical strategy is

to achieve >200 J @ -40 °C average

charpy energy at the center thickness to

have any chance of passing the ESSO or

CTOD testing.

• If the cross sectional grain size cannot be

properly optimized to meet the toughness

requirements, the only option is to add

costly additions of Ni in the 0.50-1.0% to

assist in the low temperature toughness

performance.



EH47 Ship Plate


C Mn1 P S Si Cu1 Ni2 Cr1 Mo1 V Nb3 Ti4 Als N2 B

.05-.07

1.35-1.70

≤0.015 ≤0.003.10-.20

≤0.35.40-1.00

≤0.25 ≤0.08 NIA.030-.060

.010-.020

≤.030≤60 ppm

NIA

Example of a typical EH47 heavy gauge alloy design

1 – Depends on mill capabilities

2 – Ni is used to promote good low temperature fracture toughness performance. How much Ni

is required depends on effectiveness of implementation of Nb metallurgical rolling strategy. Ni

can be reduced as optimized Nb metallurgical strategy is implemented.

3 – Nb needs to be optimized for a given mill’s capability to create the proper recrystallization

behaviors during rolling. Proper Nb optimization for cross sectional grain size/distribution the

less Ni is required.

4 – Ti should be sub-stoichiometric to N2 in the 2.8-3.3 Ti:N range.


EH47 Ship Plate

• Key Metallurgical/Processing Strategies• Steelmaking/Casting:

• Vacuum degassing for hydrogen removal to the 1.5-4 ppm range.

• Internal slab quality centerline alloy segregation/core unsoundness rating of

Mannesmann scale 2.0 or lower or equivalent.

• Casting machine mechanical condition

• Superheat 10-25 °C

• Proper mold/spray chamber water cooling temperature/strategy

• Proper casting speed

• Calcium treated with proper inclusion/steel cleanliness controls.

• Sulfur ≤0.003%

• Total O2 <30 ppm, preferably <20 ppm.

• Total LMF time average of 45 minutes

• Low flow argon rinse 3-5 minutes prior at the end of the LMF cycle. A two-

step low flow argon rinse with the first rinse of 5-8 minutes prior to calcium

treatment followed by the final 3-5 minute rinse after calcium treatment is

optimum for total O2 control and cleanliness.



EH47 Ship Plate

• Key Metallurgical/Processing Strategies

• Rolling:

• Slab reheat temperature for metallurgy/rolling, typically 1150-1180 °C for this

application.

• Type I Static Recrystallization behavior > 50% total deformation

• Type II No-recrystallization behavior (pancaking) > 30%.

• Slab thickness/width design - assure that the metallurgical reduction ratio is >3:1.

• Preferably >5:1.

• Proper roughing/finishing transfer thickness and per pass reduction strategy



EH47 Ship Plate


• Rolling:

• Valid equations for determining key metallurgical temperatures/processing

parameters such as Nb solubility, RST (Recrystallization Stop Temperature), Ar3

(austenite to ferrite start temperature) and Bs (bainite start temperature).

• Implementation of mean flow stress analysis of actual per pass rolling mill data

to evaluate if the proper Nb metallurgy/recrystallization behaviors are occurring.



EH47 Ship Plate


• Post Rolling Water Cooling:

• Proper microstructure of polygonal ferrite/acicular ferrite.

• High volume fraction of high angle grain boundaries (HAGB >°15),

• Fine/homogenous cross sectional gain size.

• These three points come from proper control of the cooling rate and final

cooling temperature. A relatively high cooling rate and lower cooling stop

temperature are needed to create the balance of microstructure, HAGB and

cross sectional grain size.



EH47 Ship Plate



EH47 Ship Plate

Results – 50-100 mm EH47

Spec. 570-720

Mpa

Yield strength vs. ¼ and center

thickness vs. Nb content.

Tensile strength vs. ¼ and center

thickness vs. Nb content. Note

that at 0.040% Nb, the center

thickness and ¼ thickness

strength are similar suggesting

good homogenization of cross

sectional grain size.


EH47 Ship Plate

Results – 50-100 mm EH47Example of various Nb

and Ni levels vs. center

thickness TCVN. A

minimum average of 200 J

@ - 40 °C (red and black

lines) is required to pass

the ESSO testing.


EH47 Ship Plate


Strength vs. Nb/CE Elongation vs. Nb/CE, note the

improvement in elongation with the

higher Nb content.


EH47 Ship Plate


Average TCVN charpy

performance vs. Nb/CE

Kca fracture toughness for

0.045% Nb and 0.25% Ni alloy

design vs. plate thickness


EH47 Ship Plate


Example of the

importance of optimizing

the rolling schedule to

improve cross sectional

toughness performance.

Corresponding ESSO

test results for

optimized rolling

schedule 1


EH47 Ship Plate


Example of Nb vs. cross

sectional charpy

performance during

production process

deviations.


EH47 Ship Plate

• With the proper understanding and implementation of the

alloy/process/metallurgical design discussed, optimum

cross sectional toughness can be achieved in heavy gauge

EH47 plate up to 100 mm.

• Implementation of proper Nb metallurgy (0.040-0.050%),

costly alloy additions of nickel can be minimized from

0.90% to 0.25%.

• Examples have been given of various alloy, processing and

plate thickness and successful production of cost effective

stable/optimized mechanical property performance of

EH47 heavy gauge plate intended for ULCV applications.

Conclusions


EH47 Ship Plate

Thank You For Your Kind Attention

Douglas Stalheim – President

DGS Metallurgical Solutions, Inc.

Consultant – CBMM Technology Suisse SA, Geneva, Switzerland

Vancouver, WA USA

Phone: +1 (360) 723-2407

[email protected]

mailto:[email protected]

Documents

CBMM ASIA - SEAISIseaisi.org/seaisi2017/file/file/presentation-file/Session 10B Paper2.pdf · • Internal slab quality centerline alloy segregation/core unsoundness rating of Mannesmann