Effect of Niobium Additions on

1
Effect of Niobium Additions on Heat Affected Zone
Toughness of 0.2 Wt C Ferrite-Pearlite Steels
Dr.Robert Foley 312-567-3052 foley_at_iit.edu
Chirag Shah 312-567-5814 shahchi4_at_iit.edu
2
Objectives

• Investigate the relationship between niobium
  content up to 0.05 wt Nb with heat affected
  zone (HAZ) microstructure and toughness for
• 0.2 wt C ferrite-pearlite plate steels
• Establish relationship between results obtained
  from Gleeble simulations of HAZ with commercially
  produced SAW steel plates

3
Strategy

• Conduct a literature survey in order to
  identify and analyze
• various effects of Nb on the welding HAZ
  toughness
• Obtain commercial plate materials comprising TC
  128
• with Nb,TC 128 without Nb and ASTM A 945
  steels
• Obtain lab heats with similar base chemistry as
  TC 128
• and with varying Nb levels
• (1) lt 0.005, (2) 0.015, (3) 0.030, (4) 0.054
  wt Nb
• Using the Uwer and Degenkolbes formula develop
  a
• representative thermal cycle for simulating
  the welding HAZ

4
Strategy

• Get familiarized with Gleeble 3500 and the
  welding
• simulation techniques
• Machine Charpy specimens for welding simulation
• Perform Gleeble simulation testing and stress
  relieving
• Notch the simulated samples conduct the
  Charpy testing
• Characterize as-received materials and conduct
  austenite
• grain measurement study
• Compare the simulated results with real weldment
  tests
• Analyze the results and draw relationships

5
Experimentation 1/14
Schematic Project Planning
6
 
Experimentation 2/14
Lab Heats Chemical Composition
7
 
Experimentation 3/14
Mill Heats Chemical Composition
Heat 811S02660
TC 128 Steel
C
C
Mn
Mn
P
P
S
S
Si
Si
Cu
Cu
Ni
Ni
Cr
Cr
Mo
Mo
V
V
Nb
Nb
Al
Al
N
N
Ti
Ti
Fe
Fe
0.24
0.24
1.25
1.25
0.014
0.014
0.07
0.07
0.399
0.399
0.01
0.01
0.01
0.01
0.17
0.17
0.056
0.056
0.06
0.06
0.02
0.02
0.048
0.048
0.000
0.000
0.000
0.000
Bal
Bal
Heat 1N 11580
ASTM A945 Steel
ASTM A945 Steel
C
C
Mn
Mn
P
P
S
S
Si
Si
Cu
Cu
Ni
Ni
Cr
Cr
Mo
Mo
V
V
Ti
Ti
Al
Al
B
B
Co
Co
N
N
0.09
0.09
1.49
1.49
0.017
0.017
0.004
0.004
0.281
0.281
0.018
0.018
0.01
0.01
0.03
0.03
0.006
0.006
0.069
0.069
0.014
0.014
0.035
0.035
0.0002
0.0002
0.030
0.030
 
8
Experimentation 4/14
Gleeble Testing

• Fundamental investigation for studying Nb
  effects on
• HAZ toughness in specific microstructure
  generated
• by thermal cycle
• Simple,powerful and rapid test method
• CVN impact testing is a valid identification of
  impact
• toughness in simulated specimens due to larger
  
• homogeneous HAZ microstructure obtained
• Give reproducible results with high accuracy
• Programmed thermal cycle is used as input
• Real time monitoring and data analysis

9
Experimentation 5/14
Machining of Charpy Bar
Charpy Bar 10mm X 10mm X 55 mm
10
Experimentation 6/14
Test matrix and Nomenclature
11
Experimentation 7/14
Thermal Cycle Calculation for Gleeble Simulations
(1)
The Uwer-Degenkolbe Formula for calculating the t
8/5 (cooling time between 800 C and 500C) is
given by t 8/5 (0.043 (4.3 10-5 T0 )) (
N2 E2 / D2) (1 / (500 To )2 ) - ( 1/( 800
To)2 ) F2 ...(1) Where,
t Time (seconds) To Preheat Temp (25C) N
Efficiency of the SMA welding (1) E Heat Input
(3 KJ/mm and 5 KJ/mm) F2 Constant for SMA
welding (0.9) D Plate Thickness (1.5875 cm)
12
Experimentation 8/14
Thermal Cycle Calculation for Gleeble Simulations
(2)
Generalizing the above formula for obtaining the
whole cooling curve and developing GSL
program t (0.043 ( 4.3 10-5 T0 )) ( N2 E2
/ D2) 1/ (T- To)2 F2 (2) T To
(0.043 (4.3 10-5 T0))1/2 (N E / D) F21/2
1/t1/2 (3) where, T Peak Temperature
( 850C to 1350C with 50C interval) E Heat
Input (3 and 5 KJ/mm) Ramp Rate 0.5 C/msec Ht
Hold Time (500 msec) DT 20 Program Step
5C To room temperature(25 C) Tf final
temperature(200C) d Plate thickness(1.5875cm) F
Constant for SMA welding(0.9) N Efficiency
of the SMA welding (1)
13
Experimentation 9/14
Specimen Chamber
14
Experimentation 10/14
Programmed and Experimental Thermal Profiles 3
kJ/mm
Programmed
Experimental
15
Experimentation 11/14
Programmed and Experimental Thermal Profiles 5
kJ/mm
Programmed
Experimental
16
Experimentation 12/14
Comparison of Programmed and Experimental Thermal
Cycles
3 kJ/mm
5 kJ/mm
17
Experimentation 13/14
Simulated Region of the Charpy Bar
18
Experimentation 14/14
Experimental Setup for CVN Testing
19
RESULTS Lab Heats 1/11
76.2 kJ/In
0.005 Nb
0.015 Nb
0.032 Nb
0.051 Nb
20
RESULTS Lab Heats 2/11
127 kJ/In
0.015 Nb
0.005 Nb
0.032 Nb
0.051 Nb
21
RESULTS Lab Heats 3/11
76.2 kJ/In
127 kJ/mm
0.005 Nb
0.015 Nb
0.032 Nb
0.051 Nb
22
RESULTS Lab Heats 4/11
76.2 kJ/In
127 kJ/In
0.005 Nb
0.015 Nb
0.032 Nb
0.051 Nb
23
RESULTS Lab Heats 5/11
Charpy Test Temperature 32F
76.2 kJ/In
127 kJ/In
24
RESULTS Lab Heats 6/11
Charpy Test Temperature 0F
76.2 kJ/In
127 kJ/In
25
RESULTS Lab Heats 7/11
Charpy Test Temperature -30F
127 kJ/In
76.2 kJ/In
26
RESULTS Lab Heats 8/11
76.2 kJ/In
127 kJ/In
32 F
0 F
-30 F
27
RESULTS Mill Heats 9/11
76.2 kJ/In
127 kJ/In
TC 128 w/o Nb
ASTM A 945
TC 128 with Nb
28
RESULTS Mill Heats 10/11
76.2 kJ/In
127 kJ/In
TC 128 w/o Nb
ASTM A 945
TC 128 with Nb
29
RESULTS Mill Heats 11/11
76.2 kJ/In
127 kJ/In
32 F
0 F
-30 F
30
Work Plan Next Period

• Continue literature survey and review more
  aspects
• of effects of Nb on welding HAZ toughness
• Optical and electrical Metallographic
  examination
• Conduct Austenite grain measurement study
• As welded simulations and Charpy testing
• Perform real weldment tests and compare them
  with
• the simulated results
• Analyze the results and make a report