How to Make p Wps Din
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MK0400035
APPROVAL TECHNOLOGY FOR ARC WELDING OF St S2-3N STEEL PLATES WIT H...
WELDING PROCEDURE SPECIFICATION FOR ARC W ELDING
OF St 52-3N STEEL PLA TES W ITH COVERED ELECTRODES
S.Cvetkovski, Faculty of Technology and m etallurgy - Skopje
D.
Slavkov, Faculty of Technology and metallurgy - Skopje
J. Magdeski, Faculty of Technology and m etallurgy - Skopje
A bs tra ct : In this paper the results of approval welding technology for arc welding of plates made of St 52-3N steel
are presented. Metal arc welding with covered electrode is used welding process. Test specimens are butt welded in
different welding positions P
A
,PF,Pcand P
D
. Before start welding preliminary welding proced ure was prepared . A fter
welding of test specimens non destructive and destructive testing was performed. Obtained results were compared
with standard DIN 17100 which concerns to chemical composition and mechanical properties of base material. It
was confirmed that in all cases mechanical properties of welded joint are higher than those of base material, so
preliminary welding procedure (pWPS) can be accepted as welding procedure specification WPS for metal arc
welding of St52-3N steel.
INTRODUCTION
Welding is a special process which requires the coordination of welding operation in order to establish
confidence in welding fabrication and reliable performance in service. The tasks and responsibilities of
personnel involved in welding related activities, e.g. planning, executing, supervising and inspection,
should be clearly defined. Welding is considered a special process in the terminology of standards for
quality systems. Standards for quality systems usually require that special processes be carried out in
accordance with written procedure specifications. So welding procedure specifications are needed in order
to provide a well-defined basis for planning of the welding operations and for quality control during
welding. It can be said that Welding procedure (WP) is a specified course of action to be followed in
making a weld, inducing reference to materials, preparation, preheating (if necessary), method and control
of welding and post-weld heat treatment (if relevant), and necessary equipment to be used. But as first
Preliminary welding procedure specification (pWPS) has to be prepared. Preliminary w elding procedure
specification is a tentative welding procedure specification, which is assumed to be adequate by the
manufacturer, but which has not been approved. Welding of test pieces is needed for approval of a
welding procedure specification and has to be carried ou t on the basis of a preliminary w elding p rocedure
specification. If standard requirements are fulfilled, welding procedure specification (WPS) become a
document providing in detail the required variables for a specific application to assure repeatability.
PRELIMINARY WELDING PROCEDURE (pWPS)
The preliminary welding procedure specification was prepared in accordance w ith EN 288-2. It specu
v
tolerance range for all the relevant parameters.
The base material are plates with thickness 30 mm , made of St 52-3N steel. This steel belongs to fir&t
group of steels, according to EN 28 8 as can be seen below:
Steels with a minimum yield strength Re
h
< 360 N/mm
2
and with analysis not exceeding, in %:
c
=
Si =
Mn =
Mo =
C —
p =
Any other single element =
All elements total =
0,24 (0,25 for castings)
0,60
1,70
0,70
0,045
0,045
0,3 (0,4 for castings)
0,8 (1,0 for castings)
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As a welding process metal arc welding process with covered electrode is choosen (111 EN 24063).
Covered electrode EVB 50 intended for welding of carbon and low alloyed steels with yield strength till
610 N/mm
2
is recommended to be used a filler material for welding. Before start with w elding, drying of
electrodes at temperature of 300 °C/2h is recommended.
Welding has to be done in 4 different positions according EN 288 which designation is shown at figure 1.
P
A
flat P
F
vertical upwards P
c
horizontal-vertical P
E
overhead
Figure 1. Welding positions for different specimens (Butt welds)
For those welding positions and thickness of base material, groove preparations like on the figure 2 are
given.
1
n
i
a b
Figure 2 Groove preparation for specimens P
A
,P F and P
G
(a) and P
c
(b)
Recommended preheating temperature is 100 °C (determined by m ethod of Seferian). The edges of
welding plates are grinded before start of welding.
Used welding parameters are given in tables 1-4, and figures 3.
lable
Run
1
2
3
4
5
6
7
1 Number of runs and order of fil ling out the groove for PA welding position
Process
Traveling
Traveling
Traveling
Traveling
Traveling
Traveling
Traveling
Electrode
diameter
EVB50 (t>3.2
EVB50
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APPROVAL TECHNOLOGY
FOR ARC
WELDING
OF St
52-3N STEEL PLATES W ITH...
Table
2
Number
of
runs
and
order
of
filling
out the
groove
for P
F
welding p osition
Run
1
2
3
4
5
6
7
Process
Traveling
Traveling
Traveling
Traveling
Traveling
Traveling
Traveling
Electrode
diameter
EVB50
03.2
EVB50
4
E V B 5 0
(])4
E V B 5 0 4
EVB50 04
EVB50
04
EVB50
04
Current
[A]
110-120
150 -160
150 -160
140 -150
140 -150
140 -150
130 -140
Voltage
[V]
19-20
20-21
20-21
20-21
19-20
19-20
19-20
Type of current / polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
Travel
speed
[mm/min]
55-60
70-75
70-75
80-85
75-80
75-80
70-75
Table
3
Number
of
runs
and
order
of
filling
out the
groove
for P
c
welding position
Run
1
2
3 .
4
5
6
7
8
Process
• Traveling
-
Traveling
Traveling
Traveling
Traveling
Traveling
Traveling
Traveling
Electrode
diameter
EVB50
03.2
EVB50 04
EVB50 05
EVB50
04
EVB50 04
EVB50 04
EVB50 04
EVB50 04
Current
[A]
110-120
150 - 170
200-210
200
- 210
160
-170
160
-170
170-180
160
-170
Voltage
[V]
19-20
20-21
22-23
22-23
20-21
20-21
20-21
20-21
Type of current / polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
Travel
speed
[mm/min]
75-80
120 -125
175
180
165
170
220
225
125
126
125 -130
125-130
Table
4
Number
of
runs
and
order
of
filing
out the
groove
for P
E
welding position
Run
1
2
3
4
5
6
7
Process
Traveling
Traveling
Traveling
Traveling
Traveling
Traveling
Traveling
Electrode
diameter
EVB50 03.2
EVB50, 04
EVB50 05
EVB50
04
EVB50 04
EVB50 04
EVB50 04
Current
[A]
110-120
140
- 150
200
- 210
130
- 140
130
-140
130
-140
120
- 130
Voltage
[V]
18-19
20-21
22-23
19-20
19-20
19-20
19-20
Type of current / polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
DC/inverted polarity
Travel
speed
[mm/min]
70-75
90-95
85-90
70-75
85-90
90-95
6 5 - 7 0
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APPROVAL TECHNOLOGY FOR ARC WELDING OF St 52-3N STEEL PLATES WITH...
P F
L
• 41-- -
\
J
m
Pc PE
Figure 3 Num ber of runs and order of filing out the groove for different welding position
WELDING PROCEDURE TEST
Making and testing of test pieces representing the type of welding used in production are in accordance
with EN
288-3.
The welder who undertakes the welding procedure test satisfactorily in accordance with
EN 288-3 is approved for the appropriate range of approval given in the relevant part of E N 287.
Test piece
The welder assembly to which the welding procedure will relate in production shall be represented by
making a standardized test piece or pieces. The test piece for butt welding of steel plates, like in our case,
is in accordance with figure 4. The length of the test piece shall be such as to provide for the appropriate
test specimens as given in Table 1.
Welding of test piece
Preparation and welding of test pieces were carried out in accordance with the pWPS, and under the
general conditions of welding in the production which they shall represent. Standard EN 288-2 defines a
format for the welding procedure specifications for arc welding of metallic materials, which is considered
to fulfill the requirements in current standards for quality systems as regards procedure specifications.
Test pieces for all welding position were prepared. Dimensions of test pieces are like on the picture 4.
a = 3t; minimum value 150 mm b = 6t; minimum value 350 mm
Fig ure 4 - T est piece for a butt weld of plates
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EXAMINATION AND TESTING
The testing includes both nondestructive exam ination (N DE) and d estructive testing which shall be in
accordance with the requirements of Table 5.
Table 5 Exam ination and testing of the test pieces
Test piece
Butt-weld
Type of test
Visual
Radiographic or ultrasonic
Surface crack detection
Transverse tensile test
Transverse bend test
Impact test
Hardness test
Macro-examination
Extent of testing
100%
100%
100%
2 specimens
2 root and 2 face
specimens
2 sets
required
1 specimen
Footnote
—
d
a
-
b
f
c
-
Penetrant testing or m agnetic particle testing. For non-magnetic materials, penetrant testing.
2 root and 2 face bend test specimens may preferably be substituted by 4 side bend test specimens for / > 12 mm.
c
Not required for parent metals:
- ferrtic steels with R
m
430 N/mm
(R* 275 N/mm
2
);
- group 9 steels.
R« is defined in the relevant product standard.
Ultrasonic testing is only applicab le for ferritic steels and. for t > 8 mm.
Testing as detailed does not p rovide information on the mechanical properties of the joint. Where these properties are relevant to the
application an additional approval shall also be held e.g. a butt weld approval.
One set in the weld metal and one set in the HAZ . Required only for t > 12 mm and only for parent metals having specified impact
properties or when required by the application standard. If a testing temperature has not been specified, testing shall be performed at
room temperature.
NON DESTRUCTIVE TESTS
Visual control and radiographic testing were carried out to all test specimens. Unalowed defects were no
detected. The root and the face of welded joints are w ith regular shape.
DESTRUCTIVE TESTS
Machining probes for destructive testing from test specimens is given in figure 5.
Specimens and testing for transverse tensile testing for butt joint are in accordance with ISO 4136. One
probe for each specimen (welding position is used). Comparing obtained results (Table 6), and the values
for mechanical properties according to DIN 17100 standard (R^ = 345; R
m
= 490-r630; A
5
(%) = 22t, 201),
it can be seen that obtained results are in all cases higher than the values for base material.
1
I
~- Gitcans 2s -va
i
E
A-M 2
tr
- - HMK t*C tHSif«ar l
Figure 5 Machining probes of test specimens for a butt weld in plate
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APPROVAL T E C H N O L O G Y F O R ARC W E LD I N G O F St 52 3 N S T E E L P L AT E S W I T H . ..
Table 6 Results of transverse tensile testing of test specimen s for different welding positions
Specimen
PΑ
P F
P c
P E
R eh
[ N / r a m
2
]
366
365
364
369
Rm
[ N / m m
2
]
515
520
519
523
A
s
[ ]
26.1
25.2
26.0
25.8
Specimens and testing for bend testing for butt joints shall be in accordance with EN 910. The bending
angle should be minimum of 120°, and in our tests angle of 180° were obtained. Two probes were
prepared from each test specimen. As can be seen from Table 7 all results are allowed.
Table
7
Result
of
bending test
Specimen
PΑ
P F
P c
P E
Bending 18 °
allowed
allowed
allowed
allowed
Test specimens and testing for impact tests for butt joints are in accordance with EN 2883 for position of
specimens and temperature of testing, and with EN 875 for dimensions and testing. Testing of base metal,
welds and HAZ was performed. Machining probes for impact testing is shown in figure 6. Test
temperature was 20 °C. Minimum value for impact energy, according Din 17100 is 27 J. It can be seen
from Table 8, that all results are much higher than this value. Significant differences between obtained
results can be explained by heterogeneity of microstructure, because welding was performed with many
runs .
I N o t c h
o l c i
F i g u r e 6 M achining probes for impac t testing of welded joints
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APPROVAL TECHNOLOGY FOR ARC WELDING OF St 52 3N STEEL PLATES WITH.
Table 8 Results of impact testing of test specimens
S p e c i m e n
P Α
P F
Pc
P D
B a s e m e t a l
1 4
85
96
89
7
7
1 1
1
2
86
8
63
Z
97
97
71
46
52
158
147
15
53
154
25
137
el
6
174
56
5
12
2
32
147
53
141
137
63
T h e
method of hardness testing shall be in accordance with EN 1043. The
Vickers
method HV10 was
used. The indentation was made in the weld, the HAZs and the base metal. Maximum hardness values
allowed with standard for this group of steel is 380 HV10 (without heat treatment).
Measured hardness values on test specimens are following:
Weld:
159 179 HV10
H A Z : 159 183HV10
Base metal 136 140 HV10
Those values are much lower from the values
given
in standard, and confirmed good welding parameters.
Metallographic testing
T h e test specimen for macro examination was prepared and etched on one side in accordance with
E N
1321, to clearly reveal the fusion line, the HAZ and the build up of the runs. Unallowed defect were
n o detected. Detailed microstructural examination was carried out to detect characteristic
microconstituents in welded joints, figure 7 a e ) . Microstructure of weld metal (fig 7a) consists of
proeutectoide ferrite which forms at higher transformation temperatures, at the boundaries of primary
austenite grains. Inside the grains, acicular ferrite is formed. This microconstituent enables high tensile
properties and
very
good impact toughness. Microstructure of coarse grained HAZ consists of ferrite and
bainite and generally has worsened properties, especially impact toughness (7b). The best mechanical
properties has fine grained HAZ which consists of equiaxed bainiticferrite grains, figure 7c. Intercritically
H A Z formed as results of non complete y/ a transformation is shown at figure 7d. It could have worsened
properties as a result of martensite forming during subsequent cooling. Striped ferritepearlite
microstructure is presented at figure 7e.
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APPROVAL TECHNOLOGY FOR ARC WELDING OF St 52-3N STEEL PLATES WITH...
a
*V
^
1
5 ? ^ ^ .
1
- «
• e
Figure 7(a-e) Microstructure of test specimen PA, x500 a. weld metal b. coarse grained HAZ c. fine grained HAZ d.
Intercritically HAZ e. base metal
CONCLUSIONS
Basic idea of this paper was preparing of welding technology for steel plates made of St 52-3N in
accordance with EN 288 standard.
Concerning that, preliminary welding specification was written following standard requirements.
Test specimens for butt welds in positions P
A
, P
F>
P
c
and P
D
were prepared and welded according
preliminary welding procedure specification.
Non destructive and destructive tests were carried out to test specimens. Radiographic and visual
inspection didn't reveal presence of any significant imperfections. Results of mechanical properties of
welded joint were compared with requirements of DIN 17100 standard, for base material.. It was
confirmed that test results are higher than standard's requirements.
So, preliminary welding specification, become approved welding procedure for metal arc welding of steel
plates,
made of St 52-3N plates.
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Literature:
1.
EN 287-1 Approval testing of welders - Fusion welding - Part 1 - Steels;
2.
EN 288-1 Specifications and approval of welding procedure for metallic m aterials - Part 1 - General
rules for fusion welding;
3. EN 288-2 Specification and approval of welding procedure for metallic material - part 2 Welding
procedure specification for arc welding;
4.
EN 288-3 Specification and approval of welding procedure for metallic material - part 3 Welding
procedure tests for the arc welding of steels;
5. EN 1043 Welded joints in metallic materials - Hardness testing;
6. EN 910 Welded butt joints in metallic materials - Bend tests;
7.
EN 895 Welded butt joints in m etallic materials - Transverse tensile tests;
8. EN 875 Welded butt joints in metallic materials - Specimen, location and notch orientation for impact
test;
9. EN 26620 Classification of imperfections in metallic fusion welds, with explanations;
10. ISO 1106-1 Recommended practice for radiographic examination of fusion welded joints -Part 1
Fusion welded butt joints in steel up to 50 mm thick;
11.
ISO 4063 W elding brazing and soldering processes and braze welding of metals - Nom enclature of
processes and reference n umbers for symbolic presentation on drawings;
12.
ISO 6947 Welds - Working positions - Definitions of angles slope and rotations.
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