Influence of Weld Bead
Area on Weld Metal
Mechanical Properties
BY B. L. SHULTZ A N D C. E. J A C K S O N
The yield strength of weld metals in multipass
welds
varies inversely with the cross-sectional area of each
weld bead
ABSTRACT. Variations in w e l d i n g
conditions have been k n o w n to influence the properties of w e l d deposits
by their effect o n the transformation
and solidification processes for w e l d
metal. These changes occur during
the cooling portion of the w e l d thermal cycle; thus, it is important to
know the cooling rates of w e l d metal
in order to adequately describe its response to the welding process.
In the past, the heat source for calculating w e l d metal cooling rates has
been measured by the parameters of
the welding arc; this heat input has
been calculated in units of joules or
watt-seconds per unit length of weld.
Since various cooling rates can be obtained for a given welding energy i n put, the energy input concept cannot
adequately predict mechanical properties.
Recently it has been proposed that
the calorific heat content of the weld
metal is a more appropriate source
for determining weld metal cooling
rates. The calorific heat content is dependent upon the volume of molten
B. L. SHULTZ is Welding Engineer, General American Transportation Corporation, Sharon, Pa., and C. E. JACKSON is
Professor, Department of Welding Engineering, The Ohio State University,
Columbus, Ohio. Based on paper presented at the A WS National Fall Meeting
held in Baltimore, Md., during October 69, 1969.
26-s I J A N U A R Y
1 973
Metric C onversion
1
1
1
1
1
1
1
in.
ipm
lb/in. 2
ksi
ft-lb
kJ/in.
in. 2
25.4 mm
0.423 mm/sec
6894.76 N/m 2
6.895 MN/m 2
1.35582 joules
0.03937 kJ/mm
645.16 mm 2
1
1
1
1
1
1
mm
mm/sec
MN/m2
joule
kj/mm
mm 2
0.03937 in.
2.362 ipm
0.145 ksi
0.737561 ft-lb
25.4 kJ/in.
0.00155 in. 2
w e l d metal and is proportional to the
w e l d metal area. In this investigation
the calorific heat content of a unit volume of a single weld bead was the
basis for measurement. For convenience, such unit volume has been
termed " n u g g e t " volume, and its
cross-sectional area " w e l d nugget
area." These terms should not be confused w i t h the A W S definitions for
nugget and nugget size w h i c h refer
specifically to resistance welding.
This paper attempts to present a
working relationship between multipass shielded metal-arc w e l d metal
mechanical properties and the w e l d
nugget areas for high strength steel.
The effect of w e l d nugget area on
weld metal cooling rates and the effects of variations in welding technique on resultant w e l d nugget areas
are also presented. A unique cooling
rate has been obtained for each combination of preheat and weld nugget
area. Weld metal cooling rates and
welding energy inputs are also investigated for possible relationships
to mechanical properties.
Introduction
The properties of many w e l d deposits have been k n o w n to be significantly influenced by the arc welding
technique used during the deposition
of the weld metal. Variations in w e l d ing technique affect the dilution,
solidification
and
transformation
processes for w e l d metal. These
processes are quite complex and are
influenced by the rapid thermal
changes associated w i t h welding.
The area in the vicinity of a welding
arc is subjected to a complex thermal
cycle in w h i c h temperatures from the
initial plate temperature to above the
melting point of the alloy are involved. After the weld metal has been
melted, not only does the rate of heat
transfer to the surroundings determine the rate of solidification, but
also the nature and pattern of heat
flow during solidification have major
effects in the microstructure and
properties of the w e l d . The thermal
cycle of the w e l d heat-affected zone
is determined by the heating and cooling rates of the w e l d metal. The effects of these rapid thermal cycles on
the structure and subsequent mechanical properties are of primary
concern in welding.
The conduction of heat through the
plate and the resulting w e l d m e n t
properties are determined by the response of the metal to the heat introduced during welding. Thus, it is i m portant to know the effective t h e r m a l
cycle produced by the welding technique, in order to adequately relate
the response to the welding process.
For years, investigators have studied the rapid thermal cycles associated w i t h welding, both mathematically and empirically. 1 - 6 The
basic relationship w h i c h has been derived for the cooling portion of the
thermal cycle in the vicinity of the
w e l d has the following general form.
The cooling rate in an arc w e l d on a
very thick plate is given by:
dT_
(T - T0 )2
(D
2TTK
d0
ZH
dT
where — = cooling rate on the centerline of the w e l d ; K = thermal conductivity of the metal; T = temperature at
w h i c h the cooling rate is to be determined; T0 = initial uniform temperature of the plate; H = arc energy input;
Z = efficiency factor for heat transfer
to the base metal.
The heat source for calculating
weld metal cooling rates has typically
been considered to be the welding
arc, and its energy, H, is usually calculated in energy units per linear inch
of w e l d , as follows:
Item
C
012
4.91
0.56
0.48
0.32
0.84
0.070
Ni
Cr
Mo
Si
Mn
V
Ti
P
S
Al
Cu
—
0.003
0.005
0.021
—
Y.S., 0.2% offset:
ksi
MN/m2
T.S., ksi
MN/m2
Elongation
,%
Base
Metal
Melted
I
H (joules per inch) =
V (voltage) * A (current) * 60
S (travel, i n . / m i n )
Heat
Affected Zone
I /
Fig. 1 — The cross-sectional
area of a
bead weld (shaded area) is the weld nugget area
or:
H (joules per millimeter)
V (voltage) * A (current)
S (travel, m m / s )
(2)
Not all of the energy generated by
the welding arc enters the base plate,
thus the efficiency factor, i.e., Z in eq
(1), is used to account for the various
heat losses. The value for the efficiency factor is typically assumed to
remain constant for various welding
techniques. Thus, it has been assumed that w e l d metal cooling rates
(and subsequent mechanical properties) would be proportional to w e l d ing energy input, as follows:
dT
S (travel
dO
V (voltage) * A (current)
(3)
In this expression the cooling rate is
directly related to travel speed and
inversely related to current and arc
Table 1—Typical 5 N i - C r - M o - V Plate and W e l d Deposit Chemical
Compositions, % and Mechanical Properties
Plate
5Ni-Cr-Mo-V
Deposited Weld Metal
W e l d deposit.
5 / 3 2 in. diam
E-14018
0.09
2.74
0.59
0.44
0.47
1.77
0.020
0.031
0.006
0.010
0.01
0.02
141
972
144
992
151
1041
152
1048
20.0
15.8
Reduction of area, %
58.4
58.0
Charpy V-notch at
0 F(-17.8C):
ft-lb
joules
97
132
46
62
voltage. Various degrees of success
have been reported by investigators
using this equation for predicting
cooling rates and subsequent mechanical properties in welding.
One extensive investigation of cooling rates in weld metal recently published by Dorshu 3 showed that w e l d
metal cooling rate is approximately
linearly related to travel speed,
inversely related to welding current,
but practically unaffected by changes
in the arc plasma length (arc voltage).
Myers 4 reports that the overall results
of using equations, such as eq (1), for
predicting cooling rates in welding is
that they are inadequate for fast
travel speeds and only reasonably
successful at moderate travel speeds.
In reviewing the basic assumptions
necessary for the derivation of cooling rate expressions, one of the major
factors for error is precisely indicating the effective energy of the heat
source. The energy of the heat source
is typically considered to be the w e l d ing energy input modified by a constant efficiency factor. The exact
relationship between welding technique and efficiency of energy utilization has not been determined. However, it has been pointed out that
efficiency depends upon the specific
welding technique used for depositing weld metal. This view has been
established by a qualitative study bv
Jackson et al.7 for the suomerged arc
and shielded
metal-arc
welding
process. The energy
utilized
in
forming the weld metal was s h o w n to
range from 2 0 to over 5 0 % of the total
energy of the arc source. Thus, it w a s
found that the total energy generated
by the welding arc, modified by a constant efficiency factor, is not necessarily an accurate measure of the
heat source for calculating cooling
rates. This is because the efficiency
of energy utilization is not constant
over a wide range of welding conditions.
One measure of the effective heat
source for weld metal cooling rates,
w h i c h has been proposed by Jackson, 8 is the calorific heat content of
the molten w e l d metal. The heat con-
WELDING RESEARCH SUPPLEMENT!
27-s
Nugget Area ( m m 2 )
900
50
100
1
1
150
250
300
350
Input-Kilojoule Per Linear Millimeter
1
2
3
4
5
1,000
67
1
<EY:
KEY:
•
800 —
200
A C 0 2 Solid Wire
A
V
•
•
900
V Submerged Arc
o
D Stick Electrode
700
• Tig
SL A
O C 0 2 C o r e d Wire
A E l e c t r o n - Beam
\
600
*
• Mig
->,
V
5 500
X
E
— 50
Mo
X
D
1
1
C 0 2 Solid Wire
Submerged Arc
Stick Electrode
Tig
•y7
•
O C0 2 Cored Wire
• Electron-Beam
•
o
-
• Mig
A
60
55 cj
•
V
-
ty
«
40
E 500
V
_
700
o
•
-£+* •
*
•
600 —
-
Z5
.1 400
800
60
-
1
•
o
o
-
30
<
< 300 —
A
300
20
200 —
200
3^i> A
30
V
c
-
20
o
IOC
1
03
0.2
1
1
04
0.5
Nugget Area (in 2 )
tent is proportional to the w e l d bead
cross-sectional area (weld nugget
area) per unit length. The w e l d nugget area represents the amount of
metal (Fig. 1) w h i c h has been heated
to the molten state; the thermal efficiency is inherent in the measurement. The w e l d nugget area increases
w i t h welding current and decreases
w i t h increasing travel speed. The area
seems to be relatively unaffected by
normal changes in arc voltage. A n
empirical equation for the data
(which are available) is as follows:
na (in. 2 ) = 11 22 x IO" 7 A ' 5S_
o 0.903
(4)
where: na (in. 2 ) = nugget area in
square inches, A = welding current, in
amperes, and Sipm = speed of travel
in inches per minute;
or, in metric units:
na(mm 2 ) = 3 3 , 3 1 2 x 1 0 - 6
A1
0903
where na(mm 2 ) = nuggetarea, in square
millimeters; A = welding current in
amperes and S mm/s = speed of travel in millimeters per second.
This relationship has been s h o w n
to be valid for the shielded metal-arc,
gas metal-arc, and submerged arc
welding processes.
The cooling rate in the vicinity of
the weiding arc has been s h o w n to be
1 973
1
20
06
Fig. 2 — The relation of nugget area to maximum hardness
in the heat-affected zone for an AISI 1045 carbon steel9
28-s I J A N U A R Y
-
X
O
100
•
-
^ <5
N
AV
CC
V
4 0 rr
VJ
o
E
S 400
1
40
1
60
1
80
1
100
1
120
140
I nput -Kilojoule Per Linear Inch
Fig. 3 — The relation of energy input to maximum hardness in
the heat-affected zone for an AISI 1045 carbon steel9
determined by the area of molten
metal in the weld bead. A recent
investigation 9 surveyed the effect of
cooling rates in welding on a sample
of AISI 1 045 steel. A variety of w e l d ing processes were used to produce
surface beads on the steel. W e l d nugget areas were measured from photographs taken of polished and etched
cross-sections of the weld deposits;
they were then plotted against the
maximum heat-affected zone hardness. The relationship of maximum
hardness and weld nugget area is
similar to the end quench hardenability plot for this steel and is s h o w n
in Fig. 2. These data were also studied
to determine the relation of the maximum hardness to the welding energy
input as s h o w n in Fig. 3.
A relationship between w e l d nugget area and maximum hardness in
the heat-affected zone has been
established. Therefore, since maximum hardness is a function of cooling rate, it should be possible to establish a meaningful relationship between weld nugget area and w e l d
metal cooling rates.
Objective
As a result of the concepts w h i c h
have been presented, it is expected
that weld nugget area may influence
weld metal mechanical properties. In
order to determine whether definite
trends can be detected, controlled lab-
oratory tests must be carried out; the
objectives of the program that follows
were:
1. To determine the relationship
between weld nugget areas for multiple pass weldments and resultant
weld metal mechanical properties.
2. To determine the effect of w e l d
nugget areas on weld metal cooling
rates.
3. To relate the effects of variations in welding technique to resultant weld nugget areas for the
shielded metal-arc process.
Experimental Work
Plan of Investigation
Test specimens w e r e prepared
under controlled conditions
with
mechanized welding units and preselected welding procedures; the first
series of specimens consisted of weld
beads deposited on the surface of the
plate followed by w e l d metal specimens prepared using multipass techniques.
It is expected that, w i t h the results
of these tests, it will be possible to
establish relationships w h i c h w i l l aid
in control of the process. Welding
parameter limits also may be established. These w i l l provide manufacturing techniques for the production of
desired mechanical properties and,
thus, provide a basic quality-control
method for the shielded metal-arc
process.
Materials and Equipment
A high strength, quenched and t e m pered steel w a s selected for this i n vestigation. It w a s chosen because
minor variations in w e l d i n g techniques w e r e k n o w n to produce signif-
icant variations in mechanical properties of w e l d metal.
This base metal used for experimental welds consisted of 1 and 2 i n .
(25.4 and 50.8 mm) thick plates of
5Ni-Cr-Mo-V steel. The plates had
been water quenched from 1 5 0 0 F
(814 C), and tempered at 1 1 8 0 F (638
C) to hardness values of 3 4 to 35 Rc.
Shielded metal-arc w e l d
deposits
were made w i t h electrodes of the
iron-powder (E-14018) low-hydrogen
Table 2 - - S u m m a r y of Data Obta ned from Bead-on-Plate Welds
15
15
4
4
7.75
7.75
15
15
4
4
0.051
0.019
0.052
0.020
0.133
0.043
0.138
0.044
0.047
0.046
0.081
0.024
0.103
0.032
0.194
0.052
0.266
0.058
0.073
0.069
34.6
9.24
44.6
11.9
69.3
18.5
89.1
23.8
29.0
29.0
24
24
24
27
24
24
27
24
24
24
7.75
7.75
7.75
4
7.75
15
15
7.75
7.75
7.75
0.050
0.051
0.053
0.096
0.057
0.026
0.031
0.053
0.081
0.058
0.075
0.072
0.079
0.170
0.110
0.033
0.043
0.140
0.111
0.078
29.0
29.0
29.0
63.2
29.0
16.6
16.9
29.0
40.8
29.0
110
156
156
110
110
220
110
156
156
220
27
21
24
24
21
21
24
24
21
27
7.75
4
4
7.75
7.75
7.75
7.75
7.75
15
7.75
0.034
0.074
0.086
0.028
0.027
0.080
0.034
0.049
0.025
0.087
0.052
0.127
0.131
0.074
0.040
0.099
0.046
0.071
0.035
0.134
23.0
49.2
56.2
20.4
17.9
35.8
20.4
29.0
13.1
46.0
ND
ND
ND
ND
ND
ND
ND
48.8
150.7
41.9
200
500
80
500
200
200
80
500
200
200
220
156
156
156
156
110
156
110
156
156
24
24
24
24
24
24
21
24
24
27
7.75
4
7.75
15
7.75
4
7.75
7.75
4
7.75
0.080
0.102
0.052
0.032
0.053
0.054
0.042
0.035
0.093
0.056
0.136
0,258
0.071
0.043
0.078
0.084
0.053
0.077
0.226
0.097
40.8
56.2
29.0
16.6
29.0
39.6
25.4
20.4
56.2
32.2
15.2
10.7
732
50.7
61.5
54.9
97.7
131.8
12.9
38.8
1
2
1/2
1
1
1
1
2
1
1
80
200
200
200
200
200
500
200
500
80
220
156
156
156
220
220
156
156
156
110
24
27
24
24
24
24
27
24
21
24
7.75
7.75
15
7.75
15
4
7.75
15
7.75
7.75
0.075
0.053
0.029
0.052
0.046
0.126
0.063
0.029
0.050
0.028
0.086
0.077
0.040
0.076
0.049
0.202
0.136
0.036
0.104
0.075
40.8
32.6
16.6
29.0
20.1
79.3
32.6
16.6
25.4
20.4
40.8
57.3
109.9
59.9
101.4
23.5
27.5
115.7
38.2
119.9
1/2
1
1
2
2
1
1
1
200
80
500
200
200
200
200
200
156
156
220
156
156
110
156
156
21
27
24
21
24
24
24
24
7.75
7.75
775
7.75
4
15
7.75
7.75
0.049
0.056
0.087
0.046
0.079
0.016
0.051
0.043
0.074
0.161
0.059
0.059
0.119
0.026
0.074
0.065
25.4
32.6
40.8
25.4
56.2
10.6
29.0
29.0
45.8
75.3
23.1
65.9
31.4
193.4
73.2
62.8
Welding
current,
amp (a)
Arc
voltage,
2
3
4
5
6
7
3
9
10
2
2
2
2
2
2
2
2
2
2
225
225
225
225
225
225
225
225
225
225
110
220
220
110
156
156
220
110
110
220
27
21
27
21
24
24
27
21
27
21
11
12
13
14
15
16
17
18
19
20
2
2
1
1
1/2
1
1
2
2
1
225
225
200
200
500
80
200
500
200
200
156
156
156
156
156
156
156
156
220
156
21
22
23
24
25
26
27
28
29
30
1
1
1
1/2
1
1
2
1/2
1
1
200
200
80
200
200
200
200
80
200
200
31
32
33
34
35
36
37
38
39
40
1/2
1
2
1
1
1
1
1
1/2
1/2
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
1
Cooling
rate at
1000 F,
F/sec
Heataffected
zone,
in. 2
Preheat
temperature,
F
Weld
no.
Welding
energy
input,
kJ/in.
Weld
nugget
area.
in. 2
Plate
thickness,
in.
(a) Electrode positive
V
Travel
speed
ipm
54.4
169.4
45.1
154.6
26.6
92.7
21.0
86.9
70.8
64.0
64.6
68.3
ND(b|
ND
ND
ND
ND
ND
ND
ND
not determined
WELDING
RESEARCH
SUPPLEMENT!
29-s
B
Fig. 4 — Location of mechanical
property
test specimens in weldments: A,
tensile
specimens; B, Charpy V-notch; C, macrosection
type. Typical chemical composition
and mechanical properties are indicated in Table 1 for plate and w e l d
metal.
Mechanized
shielded
metal-arc
welds were made using an arc-welding system consisting of a control
motor-generator set, a control panel,
an operator's panel, and a welding
head equipped w i t h a covered-electrode feed attachment. The control
motor-generator set is used to supply
power to operate the control panel
and the motor in the welding head.
The head is used to feed the welding
electrode and to maintain a constant
arc voltage. The feed attachment is
designed to feed straight lengths of
covered electrode of the type ordinarily used for manual shielded metalarc welding. The welding head w a s
mounted on a machine carriage, w i t h
an electronic governor.
Welding
power was supplied by a 3 0 0 amp
static d-c power supply.
Welding current and voltage w e r e
continuously recorded on 50 mv and
130v Esterline-Angus recorders. A n
electric clock, w h i c h was interlocked
to the welding current by an internal
relay in the welding system, w a s
used to measure arc time.
Weld metal temperatures and cool30-s I J A N U A R Y
1 973
cross-section facing the w e l d start
was polished and etched for metallographic examination. W e l d nugget
areas and heat-affected zone areas
were measured from the macrophotographs by a compensating polar planimeter. The welding energy input w a s
calculated for each of the weld beads
by equation (2).
The levels of the three variables in
this series of tests w e r e picked by setting the m i n i m u m and maximum level
for each variable and then calculating
the center point on a logarithmic
scale (base*). Such a calculation w a s
necessary in order for the data obtained herein to be used in a computerized program. The series of beadon-plate w e l d s w e r e used to obtain i n formation on the effects of welding
current, arc voltage, and travel speed
on w e l d nugget areas and cooling
rates. The welding conditions and the
results obtained for these welds are
shown in Table 2.
ing rates were determined from cooling curves for each of the bead-onplate welds. Cooling curves w e r e obtained by plunging a high temperature Pt-Rh 18 thermocouple in the
molten w e l d metal. The thermocouple millivoltage was fed into an X-Y
recorder w i t h a time base. The thermocouple consisted of a 2 4 in. (610
mm) long pair of 0.020 in. (0.05 mm)
diam w i r e s of Pt-6%Rh vs. Pt-30%Rh
calibrated by comparison w i t h a National Bureau of Standards platinumplatinum 10% rhodium thermocouple.
The base metal was preheated by a
3 0 0 0 w a t t strip heater. The electrodes were conditioned in an electric
furnace and stored in a stabilizing
oven. Electrodes w e r e conditioned
immediately after removal from the
hermetically sealed shipping containers for one hour at 775 ± 25 F (413 +
14 C) and immediately transferred to
the stabilizing oven at 2 5 0 F (121 C).
Bead-On-Plate Tests
The bead welds for testing during
this part of the program consisted of
bead-on-plate tests to obtain information on the effects of weld current,
arc voltage, and travel speed on the
weld nugget area and cooling rate for
the shielded metal-arc process. Plate
sizes of 1/2 in. (12.7 mm), 1 in. (25.4
mm) and 2 in. (50.8 mm) thick by 8 in.
(203 mm) w i d e by 12 in. (305 mm)
long w i t h a preheat temperature of
225 F (107 C) were used. The plates
were ground to bright metal to remove all mill scale before depositing
the bead welds on each side. The PtRh18 thermocouple was manually i m mersed in the molten w e l d metal at
the plate centerline slightly behind
the arc column.
Weld metal cooling rates at 1000 F
(538 C) w e r e graphically determined.
Weld nugget areas w e r e measured
from macrophotographs of the bead
weld cross-sections cut from the center of each w e l d bead. The side of the
Mechanical Property Weldments
For mechanical property measurements 10 weldments were prepared
w i t h the automatic welding equipment. A l l 10 weldments w e r e f a b r i cated w i t h a double-vee groove joint
in 2 in. (50.8 mm) thick plate as
shown in Fig. 4. A constant preheat
and interpass temperature between
2 2 5 - 2 5 0 F ( 1 0 7 - 1 2 1 C ) w a s used during welding. Table 3 shows a summary of the welding conditions for
the 10 weldments. The root beads of
the first 4 weldments were deposited
automatically; however, good penetration w a s not obtained and very
deep arc gouging of the second side
was required to get to sound w e l d
metal. The root beads for the last 6
weldments were deposited manually;
the remaining beads for these w e l d ments were deposited automatically.
Every weld bead in each w e l d m e n t
was run at the same welding current,
arc voltage, and travel speed w i t h the
Table 3 — S u m m a r y of Welding Conditions Used to Fabricate Mechanical Property
Weldments'in 2 in. ( 5 0 . 8 m m ) Thick H Y - 8 0 w i t h 2 2 5 F ( 1 0 7 C) Preheat
V
Travel
speed,
ipm
Nugget
area
in. 2
24
24
24
21
23
4.7
6.6
8.6
9.4
4.9
0.045
0.050
0.059
0.085
0.068
27
30
22
27
27
4.0
8.1
5.0
16.0
3.0
0.048
0.086
0.098
0.034
0.061
Weld
ment
no.
Welding
Current
dcrp, amp
Arc
voltage,
1
2
3
4
5
115
160
210
260
160
6
7
8
9
10
111
270
230
180
110
Fig. 5 — Weld nugget area
shown outlined on etched
macrosection of a weld
•• ' x.i.y'%.
exception of 4 root beads w h i c h were
run at 1 1 0 amp., 2 4 v, and 6 ipm
(2.54 m m / s ) .
The 10 weldments w e r e radiographed at least 2 days after fabrication. From each of the 10 w e l d m e n t s ,
t w o 0.357 in. (9.068 mm) diam all
w e l d metal tension and eight Charpy
V-notch test specimens w e r e machined as s h o w n in Fig. 4. The nugget
area was determined from the last
pass on etched macrosection of the
w e l d as s h o w n in Fig. 5.
A l l tensile specimens w e r e mechanically tested by an independent
testing laboratory. Room temperature
tensile strength, yield strength (0.2%
offset), elongation and reduction of
area values w e r e obtained for each
test bar.
Charpy V-notch test specimens
were tested at 30, 0, -30 and -60 F
( - 1 , -18, - 3 4 and -51 C). Specimens
were stabilized at test temperature in
an acetone and dry ice bath for at
least 2 0 min, and tested w i t h i n 3 sec
after removal from the bath. The bath
temperature w a s measured w i t h a
+60 to - 1 0 0 F (16 to - 7 3 C) t h e r m o m eter, w h i l e specimen temperature
was measured w i t h a copper constantan thermocouple inserted in a spe-
cial aluminum " d u m m y " specimen
w h i c h had been drilled to locate the
thermocouple at the specimen center. Energy absorption values in ft-lb
were obtained for each test specimen.
Results
Bead-On-Plate Test
Metallographic examination of the
bead-on-plate weld cross-sections included measurements of the w e l d
nugget area and the heat-affectedzone area. Table 3 includes the data
obtained for the nugget area measurements.
2800
WELDING CONDITIONS
2400
I in plate
Nugget area
2 0 0 F preheat HAZ
I 10 amp
Cooling rate
2 4 volts
Dilution
I 5.0 ipm
1400
2
0 0l6in
0 0 2 6 in 2
193 F/s
47 %
200
1000I 600
8 0 0 a>
CL
E
I-
E
1200
800
Fig. 6 — Cooling portion of weld
thermal cycle—
weld 56, Table 2
400
J
6
L
8
10
12
14
16
16
Time (sec)
WELDING RESEARCH SUPPLEMENT!
31-s
2800
WELDING
2400
T
CONDITIONS
2 in plate
Nugget area
2 2 5 F preheat HAZ
1 1 0 amp
Cooling rate
2 1 volts
Dilution
1 5 0 ipm
2000
400
0 0 1 9 in 2
0.0 29 in 2
1 6 9 F/s
53 %
1200
O
1000 —
B
1600
8 0 0 cu
E
I- 1200
600
800
Fig.
7 — Cooling
thermal
cycle
portion
— weld
of
2, Table
weld
2
400
8
Time
10
12
(sec)
2800
WELDING
r-
2 in plate
2 0 0 F preheat
156 amp
2 4 volts
I50ipm
2000
CONDITIONS
Nugget area
HAZ
Cooling rate
Dilution
0029m2
0 0 3 6 in 2
1 16 F/s
57 %
1200
800 $
CL
E
800
Fig. 8 — Cooling
thermal
cycle—
8
Time
portion
of
weld
weld 48, Table 2
10
(sec)
2800
WELDING
2400
I in plate
2 0 0 F preheat
2 2 0 amp
2 4 volts
1.50 ipm
r- 2000
CONDITIONS
Nugget area
HAZ
Cooling rate
Dilution
1400
2
0 0 4 6 in
0 0 4 9 in 2
I 01 F/s
62 %
1200
1600
8 0 0 n>
Q.
Q.
E
E
<u
I - 1200
600
800
400
Fig. 9 — Cooling
portion
of
weld
thermal
cycle — weld 45, Table 2
8
Time
32-s
j J A N U A R Y
1 9 7 3
10
(sec)
2800
WELDING
CONDITIONS
2400
I in plate
2 0 0 F preheat
56 amp
—
2 4 volts
7 7 5 ipm
2000
B
Nugget area
HAZ
Cooling rote
Dilution
0 0 5 3 in
0 0 7 8 in 2
6 I
F/s
50 %
200
o
1000 —
1600
8 0 0 cu
Q-
E
1200
600
800
Fig.
10 —
weld thermal
Table 2
Cooling
cycle
portion
— weld
400
of
35,
400
8
10
Time
(sec)
2800
WELDING
2400
I in plate
2 0 0 F preheat
1 10 amp
2 4 volts
4 0 ipm
2000
B
CONDITIONS
400
Nugget area 0.054 i n 2
HAZ
0 0 8 4 in 2
Cooling rate
55
F/s
Dilution
4 I %
O
IOOO —
1600
800 cu
Q.
CL
E
E
I 200
600
Fig.
11 —
weld thermal
Table 2
Cooling
cycle
portion
— weld
of
36,
8
IO
Time
(sec)
Time
(sec)
IO
iwA
'
'
12
i
/
l
l
l
WELDING
l
Nugget area
200 F preheat HAZ
I 56 amp
Cooling rate
24 /olts
Dilution
4 0 pm
i m plate
.
^ v ^ ^
-5
o
—
CONDITIONS
0 0 9 3 in 2
0 2 2 6 in 2
3 F/s
_
39%
I600
8 0 0 co
a
CO
a.
E
*-
E
CD
1200
"—I
•
-
I-
600
Fig. 12 — Cooling portion
of weld
thermal
cycle — weld 39, Table 2
i
\
I
26
I
28
30
Time
W E L D I N G
32
34
36
38
40
(sec)
R E S E A R C H
S U P P L E M E N T !
33-s
W e l d metal cooling curves w e r e obtained for the bead-on-plate tests to
determine the effects of weld nugget
areas on w e l d metal cooling rates.
Cooling curves for some of the beadon-plate welds are s h o w n in Figs. 6
to 12. Cooling rates were graphically
determined at 1000 F (538 C) from
the temperature vs. time plots. The
cooling rates w e r e determined at
1000 F (538 C); this temperature is
above the transformation range for
this weld metal composition, thus
eliminating any sudden changes in
slope introduced by transformations
on cooling. Subsequent examination
of the cooling curves revealed that
there w e r e no abrupt changes in
slope. Hence, the weld metal was
set of 4 mechanical property w e l d ments (1 to 4) was made at a welding
energy input of 35.2 kilojoules per linear inch (1385 j / m m ) , but w i t h various welding currents and travel
speeds. W e l d metal yield strength
ranged from 1 53.0 to 135.5 ksi (1056
to 934 M N / m 2 ) at the same level of
welding energy input.
A second set of 3 mechanical property weldments (7, 8, and 10) w a s
made at a welding energy input of
60.0 kilojoules per linear inch (2362
j / m m ) , but w i t h various welding currents and travel speeds. W e l d metal
yield strength ranged from 148.8 to
131.8 ksi (1026 to 1009 M N / m 2 ) at
this level of welding energy input.
Three other mechanical
property
Mechanical Property Weldments
The first four weldments radiographed exhibited areas of porosity
w h i c h were correlated to w e l d starts.
Since a backwash starting technique
w a s not feasible w i t h the automatic
equipment, all additional w e l d starts
were ground before depositing subsequent weld beads. After this technique was adopted, no porosity was
visible on subsequent radiographs.
No transverse delayed weld metal
cracks w e r e observed in any of the 10
weldments: however, 4 of the 8 t e n sile specimens from the first 4 w e l d ments exhibited poor tensile ductility
and two exhibited fish-eyes on the
fracture surfaces. Fish-eyes on the
tensile specimen fracture surfaces
Table 4 -- A l l Weld Metal Tension and Charpy V-Notch Impact Test Results
no.
Beads
Layers
Weld
energy
input,
kJ/in.
1
58
18
35.2
Weldment
Weld
cooling
rate,
F/sec
77.0
Nugget
area
in2
0.045
2
49
19
35 2
62.0
0.050
3
43
19
35.2
45.5
0.059
4
35
16
352
32.0
0.085
5
38
16
45.1
41.0
0.068
6
47
18
45.0
66.0
0.048
7
34
18
60.0
31.5
0.086
8
28
15
60.8
27.2
0.098
9
96
29
18.2
108.0
0.034
10
37
17
59.4
47.0
0.061
Yield
strength Tensile
Elon(0.2%) strength, gation,
ksi
ksi
%
151.6
153.0
150.4
150.1
144.1
142.1
140.3
135.6
139.4
144.1
148.3
149.3
138.8
140.3
131.8
135.2
152.5
153.0
148.8
148.0
153.3
158.4
154.8
153.5
148.6
146.7
144.8
145.7
153.1
152 7
154.4
156.0
146.9
148.0
145.0
148.4
152.8
145.4
151.2
154.8
Reduction in
area, %
15.7
20.0
12.9
49.0
39.0
64.0
36.0
28.0
64.0
65.0
59.4
62.4
9.3
260
17.9
20.0
20.0
20.7
20.0
13.6
12.9
60.0
61.0
60.0
33.0
61.0
40.0
28.0
25.0
4.3
16.4
14.3
20.0
86
12.1
18.6
207
9.3
93
250
Charpy V-notch energy
absorpti on; 'tt-lb
+30 F
OF
-30 F
-60 F
35.0
39.0
41.0
42.0
36.0
42.0
33.0
48.5
44.5
49.5
30.0
38.5
29.0
40.0
45.0
48.5
32.0
44.0
34.0
36.5
32.5
37.5
33.0
43.5
32.5
43.5
35.0
42.0
40.0
45.0
33.0
43.0
32.0
41.5
41.5
43.0
33.5
35.0
29.0
42.0
24.0
32.5
23.0
20.0
37.0
34.5
29.5
40.0
42.0
34.5
27.5
31.5
25.0
30.5
33.0
36.0
24.0
34.5
31.0
36.5
16.0
22.0
23.0
29.0
19.0
25.0
25.0
29.0
27.0
34.5
25.0
23.0
23.0
32.5
29.0
33.0
21.0
28.0
21.5
33.5
(a) Surface specimens reported first; center specimens are reported second.
probably transforming to martensite
at a lower temperature. The M s temperature of this weld metal is probably in the range 7 0 0 - 8 0 0 F ( 3 7 1 427 C) based on the M s temperature
of the base plate. Slopes of the cooling curves were not taken at the
lower temperature range. This was
not done because the millivoltage response of the thermocouple per degree in temperature is much smaller
in the temperature range 7 0 0 - 8 0 0 F
( 3 7 1 - 4 2 7 C ) t h a n at 1000 F (538 C)
and would result in decreased accuracy for the measurement of weld
metal cooling rates. Welding conditions for the graphical determination
of weld metal cooling rates are also
given in Table 3.
34-s I J A N U A R Y
1973
were attributed to the presence of excessive hydrogen in the w e l d metal.
All electrodes w e r e removed from the
holding oven and reconditioned at
775 ± 2 5 F (413 + 14 C). None of the
remaining six weldments exhibited
fish-eyes on the fracture surfaces,
and all but t w o specimens exhibited
cup and cone fractures.
Results of the all-weld-metal t e n sion and impact tests are given in
Table4.
Discussion
Effect of Welding Energy Input
The effect of welding energy input
on E-14018 weld deposit
yield
strength is s h o w n in Fig. 13. The first
weldments were made, one at 18.2
kilojoules per linear inch (716 j / m m )
and t w o at 4 5 . 0 kilojoules per linear
inch (1771 j / m m ) . In general, yield
strength decreased w i t h increasing
welding energy input.
The effect of cooling rate on Charpy
V-notch energy absorption at - 6 0 F
(-51 C) is s h o w n in Fig. 14. Energy absorption tended to increase slightly
w i t h increasing w e l d nugget area and
lower cooling rate.
The relationships between welding
energy input and w e l d metal properties show that a calculation of the arc
energy is not a positive means of controlling w e l d deposit
mechanical
properties. The scatter in the results
suggests that calculated welding e n -
Welding
Energy
Input
160
Cooling Rate ( C / s )
(j/mm)
1000
2000
L
50
10
50
I
M—
o
S: 40
a.
L,
I
-
- 6 0 °F Test Temperature
—
o
50 "3
O
CO
<
I
I
••
•
30
••
•
>,
CJl
•
CD
•
l5 20
-
•
•
-
JZ
—
o
o
Z
10
>
>,
0
15
30
Welding
Fig. 13 — Relation
input
45
Energy
between
Input
—
20
(kj/in)
yield strength
energy
Nugget A r e a (mm 2 )
I60
IO
20
I
1
30
1
t
150
40
V
1
•
130
rates
and
I 100
100
— 1000 «
•
•
•
-
,
cooling
50
1 -
•
-a
0 02
I20
Area ( m m 2 \
60
•
I40
0
IOO
t
•
•
n
I
80
W e l d nugget area has been s h o w n
to be more directly related to w e l d
metal mechanical properties than
welding energy input. Nonetheless,
there still remains the problem of controlling w e l d nugget areas under production conditions. Once a usable
range of yield strengths is determined and related to w e l d nugget
areas, the chart s h o w n in Fig. 17 can
be used to help personnel maintain
the range of nugget areas desired. It
is to be remembered that voltage is a
minor factor and is not used in this
calculation.
Since measurement and control of
travel speed for the manual process is
quite difficult, an additional solution
to the problem would be to specify the
minimum number of passes to be
deposited for a given joint as a means
Nugget
50
1
I
60
Fig. 14 — Relationship
between measured
Charpy V-notch energy absorption at -60 F
Practical Application of the
Nugget Area Concept
The data presented in the preceding sections were confined to
automatic shielded metal-arc welds.
Automatic equipment w a s used to e n sure uniformity and reproducibility of
the basic relationships derived from
the data. The w e l d nugget area concept was also used to analyze data
from manual 5Ni-Cr-Mo-V steel w e l d ments. W e l d i n g energy input for each
weldment
was
calculated
from
equation (2). W e l d nugget areas w e r e
calculated from
the
nomograph
shown in Fig. 17, w h i c h gives the
solution to equation (4). Analysis of
the data indicated that even calculated w e l d nugget area appears to be
directly related to w e l d metal deposit
yield strength — Fig. 16.
Effect of Weld Nugget Area
A review of the data for Fig. 13
showed that, for a given welding e n ergy input, the w e l d m e n t w i t h the
most passes always had the highest
yield strength and the w e l d m e n t w i t h
the least passes always had the lowest yield strength. This suggested
that the area of the weld bead may be
a contributing factor in controlling
yield strength.
The relationship between w e l d nugget area and E-14018 w e l d deposit
yield strength is s h o w n in Fig. 15.
W e l d deposit yield strength is inversely related to weld nugget area.
40
Cooling Rate ( F / s )
and welding
ergy input may not be the best indicator of weld metal mechanical properties.
3s
~ 10
9- r.
60
<
900
,
0.04
Nugget
006
008
A r e a (in 2 )
0 1
Fig. 15 — Relationship between measured weld nugget area and
yield strength for E14018 high strength multipass weld metal
0.04
0.06
Weld
0.08
Nugget
Fig. 16 — Effect of calculated
for E14018 weld deposits
0.I0
Area ( i n . 2 )
weld nugget area on yield
WELDING RESEARCH SUPPLEMENT!
strength
35-s
Chart for Determining
Nugget Area for a given Welding Technique
TRAVEL (S)
too
.200
CURRENT (A)
100-
50^-
NUGGET AREA
(no)
-100
90
5 -
ZOO
80
—- O.Ol
•
IO
60
0.02
300
=—
6
E
400
0.04
m
£
A
e
0.03
CM
cu
cu
70
0 05 «vh
.C;
5
500
% °-
-—O.IO
100 - CD
0.20
CJ
800
|
"CJ
o
o
30
cu
W
Is
k,
cj
Q_
Crto
v.
=>
/O-
CU
CX
20 t$
.C;
C3-
900
40
<=
0.08 -g
600
700
50
0.30
CO
£
0.40
/OOO
0.50
0.60
500 —
080
• 1.00
10
9
2000
8
7
6
5
Fig. 17 — Nomograph for determining nugget area for a given welding technique. Welding voltage is not a controlling factor. A
straight line drawn to connect the current (A) and travel (S) intersects the nugget area (na) at the calculated value
36-s ! J A N U A R Y
1973
of maintaining production quality.
The recognition of the influence of
nugget area and its accompanying
cooling rate on the mechanical properties of weld metal is significant.
This approach w i l l provide a guide for
establishing
welding
techniques
w h i c h result in more uniform mechanical properties.
Conclusions
The experimental tests and equipment used in this program were d i rected toward obtaining a working relationship between multipass w e l d
metal mechanical properties and
weld nugget areas for a high strength
steel. W e l d metal cooling rates and
welding energy inputs w e r e also investigated for possible relationships
to mechanical properties. W e l d nugget areas (the cross-sectional area of
a single w e l d bead) were measured
from the last pass of the multiple pass
weldments. Welding energy inputs
were calculated in units of joules per
unit length of w e l d . Weld metal cooling rates w e r e measured at 1000 F
(538 C) from cooling curves obtained
w i t h a high temperature Pt-Rh 18
thermocouple. Each of the factors selected for investigation were related
to w e l d metal mechanical properties;
however, some were more significant
than others.
Based on the results the following
conclusions have been d r a w n :
1. The result of these tests is a good
indication of a clear relationship bet w e e n w e l d nugget area and w e l d
metal cooling rates. The w e l d nugget
area becomes a useful indicator of
weld metal mechanical properties
w h i c h are influenced by cooling rate.
A n inverse relationship
between
weld nugget area and yield strength
in multipass w e l d metal of high yield
strength is indicated.
2. The w e l d metal cooling rate associated w i t h a given nugget area was a
good indicator of the mechanical
properties and a linear relationship
existed in these tests between yield
strength and the inverse of the cooling rate.
3. W e l d nugget areas and cooling
rates appear to be determined by
welding current and travel speed. The
results of bead-on-plate tests suggest
that arc voltage has no significant
effect on w e l d nugget area or w e l d
metal cooling rate.
References
1. Rosenthal, D., " M a t h e m a t i c a l Theory
of Heat Distribution During Cutting and
Welding,"
Welding
Journal,
2 0 (5),
Research Suppl., 2 2 0 - s to 2 3 4 - s (1941).
2. Rykalin, N. N., "Effectiveness of T h e
Metal-Fusion Process During Arc W e l d i n g , " Doklady Akademii
Nauk SSR, 63
(11), 131 to 1 3 4 ( 1 9 4 8 ) .
3. Dorschu, K. E., " C o n t r o l of Cooling
Rates in Steel Weld M e t a l , " Welding Journal, 4 7 (2), Research Suppl., 49-s to 6 2 - s
(1968).
4. Myers, P. S., "Fundamentals of Heat
Flow in W e l d i n g , " Welding Research
Council Bulletin 123, July 1967.
5. Christenson, N., "Distribution
of
Temperatures in Arc W e l d i n g ,
British
Welding Journal, 12 (2), 5 4 - 7 5 (1965).
6. Barry, J . M., " H e a t Conduction f r o m
Moving Arcs in W e l d i n g , " Welding Journal, 4 2 (3), Research Suppl., 97-s to 104-s
(1963).
7. Jackson, C. E., and Shrubsall, A. E.,
"Energy Distribution in Electric W e l d i n g , "
Welding Journal, 29 (5), Research Suppl.,
231-s to 241-s (1950).
8. Jackson, C. E., "The Science of A r c
W e l d i n g , " Part I, Welding Journal, 39 (4),
(5), (6), 1 29-s to 140-s; Part II, 39 (5), 1 77-s
to 190-s; and Part III, 3 9 (6), 2 2 5 - s to
230-s (1960)
9. Jackson, C. E., " W e l d i n g Engineeri n g , " Welding Journal, 4 7 (1 1), 8 8 4 to 855
(1968).
( 1 ) S e n s i t i v i t y of t h e D e l t a T e s t t o S t e e l
Compositions and Variables
by L. J .
WRC
Bulletin
No. 172
May 1972
McGeady
The introduction and use of higher strength heat-treated steels have demonstrated the need for awareness of weldability and fracture problems in the total
composite of weld metal, heat-affected zone and plate material. Hence there has
developed need for an appropriate test specimen and procedure applicable to the
total composite weldment providing the opportunity for failure in any area. This
report describes a specimen applicable to this need and to present data to determine whether the proposed specimen, the Delta, allows failures to follow leastresistant paths because of specimen geometry and loading system. It is not the
purpose to recommend materials, welding procedures or processes, though it has
been necessary to study many of these in a wide variety of combinations to determine their influences on behavior of the specimen. The work reported in this
paper was sponsored by the Pressure Vessel Research Committee of the Welding
Research Council.
(2) E x p e r i m e n t a l S t r e s s A n a l y s i s a n d F r a c t u r e
B e h a v i o r of D e l t a S p e c i m e n s
by J . M.
Barsom
This investigation was undertaken to analyze the stress distribution in the
Delta specimen and to investigate the possible effect of the stress distribution on
the flow and fracture behavior of the Delta specimen.
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