A Guide to the Solidilication 01 Steels
Jernkontoret,
Stockholm 1977.
Jern kontoret Box 1721 S-111 87 Stockholm Lju...
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A Guide to the Solidilication 01 Steels
Jernkontoret,
Stockholm 1977.
Jern kontoret Box 1721 S-111 87 Stockholm Ljungberg
Tryckeri AB, S6dertalje ISBN 91-7260-156-6
1977
FOREWORD An investigation
into the solidification
terest was started by Jernkontoret work was the responsibility
structures
in steels of commercial
in 1974. The planning
of a Research Committee,
reference of 408/74. Membership
in-
and supervision
of
having the Jernkontoret
of this Committee comprised:
G. Grunbaum, (Sandvik AB), Chairman, B. Call mer, (Swedish Institute for Metals Research),
Secretary,
b.
Hammar,
(Sandvik
Hellner, (AB Bofors), S. Maim, (Uddeholms AB) and
A.
Nilsson, (Stora Kopparberg
The experimental
programme
Metals Research, Stockholm, Callmer, were responsible
AB), P. Havola, (Ovako Oy), L.
AB), L. Morsing, (Avesta Jernverks
AB).
was carried
out at the Swedish
where initially
for the work, including
lography and photomicrography
were performed
represented
supplied
contributions
on the Committee to the experimental
Institute
for
B. Carlsson and, from 1975, B. evaluation
of results. Metal-
by H. Modin. The companies
samples of steels and made other
programme.
D. Dulieu (BSC, Sheffield
Lab-
oratories, England), assisted with the preparation of the English text. The project was partly financed by the Swedish Board for Technical Development.
CONTENTS Foreword
5
Introduction
9
1. Experimental Techniques
11
2. Carbon and Low Alloy Steels
17
3. Chromium Steels
55
4. Stainless and Heat Resistant Steels
81
5. High Speed Steels
133
6. Conclusions and Comments
142
7. References
151
8. Alloy Index
154
INTRODUCTION The purpose of the present work is to provide a systematic compilation of solidification data, describing the formation of the as-cast microstructures in steels of technical importance. The compositions have been chosen to cover a large part of the spectrum of steels in current production. Where a specific steel is not included, it should be possible to gain an outline of its solidification characteristics from related compositions present. The book is not intended to provide a theoretical treatment of solidification processes in steels. It is hoped rather that the descriptions of the microstructures formed on solidification will assist in solving, or avoiding, some of the problems arising in casting, hot working and welding. However, specific production and materials problems have not been described. A knowledge of solidification processes is also relevant to problems of quality in the final product; for example, in understanding the effects of segregation arising during solidification on the microstructure of wrought material. The work should find use also in metallurgical education as a source of basic information. In the planning stage, the Project Committee hoped to collect data from both the technical literature and unpublished laboratory reports. However, a study of these sources soon showed that most investigations were unique in both their experimental techniques and presentation of results. In addition, thermal analysis at varying cooling rates had been identified in this project as a powerful technique for investigation of solidification. Little systematic experimental work employing this method was found in the literature. It was decided, therefore, to generate the data needed within the study and to use the same reproducible methods for all the steel compositions studied. The Committee gave considerable attention to the problem of relating structures obtained in small, laboratory ingots to those found in large ingots under production conditions. This aspect is discussed in chapter 1, where the experimental techniques are described and the format adopted for diagrams and tables is explained. Chapters 2-5 comprise the main body of the book, with results for each individual steel described. These sections are printed in a standardized form for ease of quick reference. The large number of steels has made it necessary to limit the amount of information given. Wherever possible in these chapters, descriptive passages have been avoided in favour of figures, diagrams and micrographs. The alloys have been brought together into four broad classes: Carbon and Low Alloy Steels (Ch. Chromium Steels (Ch. Stainless and Heat Resistant Steels (Ch. High Speed Steels (Ch.
2) 3) 4) 5)
Although the intention was to arrange the steels in a logical way, this was not always possible. In most cases, however, a steel type will be classified easily within the four groups. Each of chapters 2 to 5 is introduced by a paragraph describing those specific steels which have been studied. The reader can quickly ascertain whether a steel composition is included or not, by examining either the tables accompanying each chapter, or the index tables given in chapter 8. Chapter 6 contains some general conclusions regarding solidification phenomena which are common for the groups of steels. References to the relevant literature have been made throughout and are listed in full in chapter 7. Chapter 8 comprises master tables of chemical compositions and thermal analysis data for all the steels included in the study. In addition, this chapter includes tables of dendrite arm spacings and microsegregation.
11
1. Experimental Techniques The object of the laboratory experiments was to produce microstructures identical to those obtained under production solidification conditions. A suitable experimental technique would allow the following: •
Determination of pertinent temperatures, such as those of the liquid us, solidus and high temperature reactions, together with the relative amounts of the phases formed.
•
The ability to freeze instantaneously reaction by rapid quenching.
the solidification
•
A controlled wide limits.
•
A reproducible relationship between the structures obtained in laboratory samples and those found in full-size ingots.
cooling rate which could be varied within
To fulfill these requirements, the experiments were carried out on small ingots (35 g) solidified in a ceramic crucible at a preset, controlled cooling rate. The development of the solidification microstructure is governed mainly by alloy composition and the rate of heat removal. By using samples of commercial alloys and letting them cool at a rate similar to that found in full scale ingots, good reproduction of microstructural features was obtained. A range of cooling rates in steel ingots, evaluated from published cooling curves, is shown in figure 1.1, [1-4,23, 26, 93, 96] * .The results refer to different ingot sizes; which means that values on the abscissa are only indicative of position within an ingot. The figure shows that the range of cooling rates of practical interest lies between 0,05 and 3°C/s. Accordingly, the specimens in this study were cooled at 0,1, 0,5 and 2°C/s.
According to reported data (for cooling rates [20], solidification rates [4, 21] and local solidification times [22]), ingots produced by the electroslag remelting or vacuum arc remelting processes follow, in general, the pattern shown in figure 1.1. No experimental values of cooling rates in continuous casting were found in the literature. Calculations based on mathematical models of heat transfer show these cooling rates to be slightly higher than for ingots up to 20-30 mm under the surface, as shown in figure 1.1 [5,6]. At larger depths no great difference exists, as cooling rate is governed by heat conduction in the solidified shell. This has been established by comparisons between measured solidification speeds in ingots and continuously cast material, [4, 7, 8]. Solidification of weld metal takes place at high cooling rates. Depending on process parameters, such as the size of the weld pool, rates have been reported to vary between 20 and 200°C/s, [10, 11]. In powder metallurgy very high cooling rates are encountered, Calculations lead to an estimate of 103-104 °C/s for the solidification of argon atomized steel particles [9]. Welding and powder metallurgy are thus not directly covered by the experiments reported in the present work.
('C/s)
\000 E
.3-500
~
~300
u
;t200 l1'I
Cooling rate °C/minoC/s 600 10
300
:::li ~ 100
100
x
1 tonne
0
2,5- 9 tonnes
5 x
200
Ingot weight < 1 tonne
I:!.
Continuous cast, calcul. •
3
>a::
~ z o
u W l1'I
50 30 20 1
2
3
5
10 20 30 50 100 200 AVERAGE COOLING RATE (·C/minl
500 1000
2 Figure 1.2 Dendrite arm spacings in commercial 0,14-0,88% C-steel ingots (After Suzuki A. et ai, J. Japan Inst, of Metals, (1968) 1301 -1305.) [28]
30
0,5
20
0,3 0,2
10 6
0,1
3
0,05
3
5
10
20
30
50
100 200 300 500 Distance from surface. mm
• References appear in chapter 7
Figure 1.1 billets
Cooling
rates in steel ingots and continuously
cast
The cooling rate may be related to the microstructure through its effect on the secondary dendrite arm spacing. This decreases with increasing cooling rate in the manner shown in figure 1.2, [28]. Many diagrams of this type are available in the literature. When extrapolated to cooling rates prevailing in welding and powder solidification, the relationship predicts fairly well the secondary dendrite arm spacings in weld metal and steel powder, [14, 9, 96]. As shown in later sections, the arm spacings found in the small samples are of the same order of magnitude as those reported for ingots of the same composition. Figure 1.3 shows examples of secondary dendrite arm spacing measurements in the columnar zones of ingots of low alloy steel ranging in weight from 1 to 9 tonnes, together with results from a 1,7 tonne stainless ingot, [12, 13,26].
12
Secondary dendrite arm spacing, j.Jm
ARGON INLET •.....---WINDOW
400
--
r
300
TEFLON PLUG
FURNACE THERMOCOUPLE FOR POWER REGULATION THERMOCOUPLE ANALYSIS
FOR
I
CRUCIBLE AND LID
SOOmm
200
WITH SAMPLE
AI 0) FIBRE 2 BRASS
TUBES
REFLECTING
WALL
MOLYBDENUM SUPPORT
100
AI 0) 2
WIRE
ROD
TUBE
ARGON INLET
o
o
Figure 1.3
Thermal
20
40
60
80 100 120 Distance from surface, mm
Dendrite arm spacings in production
scale ingots
Experimental
furnace
analysis
The steel samples of 35 ± 1 g were melted in alumina crucibles in an atmosphere of argon (02 < 5 ppm), Samples inserted in the hot furnace, shown in figure 1.4, melted in five minutes. A tube of alumina was resistance heated by a molybdenum wire element. Argon was flushed through the tube from the top at a rate of approximately 0,1 lis. The outside of the tube with the molybdenum wire was subjected to a non-flowing argon atmosphere. The tubular furnace shell was double-walled and water cooled, with the inside chromium plated to give good heat reflection. No insulation was used so that the furnace had a low thermal inertia, enabling cooling rates of up to 2,0°C/s to be achieved down to 1000°C. The samples were quenched in brine within about three seconds from removal at the bottom of the furnace.
FURNACE
Figure 1.5
Figure 1.4
Control systems
The temperature and cooling rate of the furnace was controlled by the power input. The desired furnace cooling rate was achieved by presetting a programmable temperature-time regulator (Data Trak). An artificial thermoelectric voltage-time function was generated and compared with the actual output of the furnace thermocouple. The system minimized any difference by adjusting the furnace power input. Theaccuracy in cooling rate which was obtained was better than ten percent. Figure 1.5 shows schematically the regulating and measuring system of the furnace. The temperature of the steel sample was measured at its centre by means of a thermocouple (PtlPt-10% Rh). The thermocouple output was registered by a digital microvolt meter. The cold junction was maintained at O°C.One registration of specimen temperature per degree fall in furna-
13
ce temperature was used for all the cooling rates. The result was punched on a paper tape and evaluated in a minicomputer. The thermocouples and the other components used were checked by determining the liquidus temperature of a pure nickel melt. The precision of the temperature measurements was found to be ± 2°C.
a minimum, see figure 1.6. After this point the cooling rate of the sample started to approach the cooling rate of the furnace, since no more latent heat was evolved. The derivative is more useful for evaluation of the cooling curve, showing changes more clearly than the temperature-time curve itself.
Thermal analysis, as used here, is based on an analysis of the temperature versus time curve of a solidifying sample. The furnace and the molten sample are subject to a constant cooling rate, but when the sample starts to solidify the latent heat evolved decreases the cooling rate of the sample. In fact, all reactions or transformations evolving latent heat decrease the cooling rate of the sample. The growth of the solid phase starts at the walls of the crucible and proceeds to the centre. The dendrites grow at an almost constant temperature, shown by the plateau of the temperature-time curve in figure 1.6. When the tips of the dendrites reach the thermocouple the heat transfer from the thermocouple becomes markedly more rapid and the amount of latent heat sensed by the thermocouple is diminished. As a consequence the registered temperature starts to decrease.
The end of solidification, as defined here, is denoted the solidus temperature and is strongly dependent on the cooling rate. It was particularly difficult to determine the solidus temperature by thermal analysis in steels with a high carbon content. This is a result of their wide solidification ranges and very low growth rates near the end of solidification. Furthermore, eutectic reactions occurred at the end of solidification over a large temperatu re range which led to poorly defined minima in the derivative.
TEMPERATURE
T (·C)
COOLING RATE
dT d't"
T
(·C/s)
+
The solidus temperature was also determined as the start of melting in heating tests. The samples cooled at a,1 and a,5°C/s were reheated at a,5°C/s. The start of melting and the end of solidification in cooling trials generally differed only by a few degrees. The lowest of these temperatures was chosen as the solidus temperature and rounded off to within five degrees. Quenching experiments confirmed that this method for determining the solidus temperature was acceptable. In a few cases a small amount of the melt could solidify below the reported solidus temperature, but for practical purposes the reported solidus temperatures are relevant. All temperatures given in the tables are mean values of two to five measurements and thus are not necessarily those which can be evaluated from the cooling curves shown.
o R
t furnace _."
"-..,.
TIME, T (s) Figure 1.6
T
Thermal analysis, temperatures
CD
Start of growth of primary phase
®
Growth temperature rature
®
Dendrite tips reach thermocouple
of dendrites,
~ ...........
used as liquidus tempein centre of sample
Start of secondary phase precipitation Maximum reaction rate for secondary phase precipitation, maximum temperature, used as temperature of formation of the secondary phase
w
End of solidification,
~ w
-R
Preset cooling
rate of furnace
'
,
~ ~T
1 I
I -
0
-1I
-
reached
-
1
='4
1
~ w
I I I
b
Tfurnace : Tsample I I
0
-R
t?
z :i
0 0
u
c
o
'[,
TIME
Figure 1.7
a-c.
_
I I
d't
1450
0
1400
dT dt
1350
-1,5 R = 0,5°C/s
1300
0
Average 2,0
Liquidus temperature, Temperature
ferritic primary phase, °C
of austenite formation,
Solidus temperature,
°C
Solidification
range, °C
Solidification
time, s
CD
°C
CD
CD
Microsegregation Element
Cr
Ni
Mo
1,3
1,4
2,5
R = 0,5°C/s Tq = 1400°C
Cooling Rate,R, eC/s)
0,5
0,1
1501
1501
1502
1485
1485
1487
1450
1450
1465
50 85
Precipitates
lIs)
200
100
50
40
210
640
Steel 208 • 35
Partly solidified
Figure 1 R Tq
d
= O,5°C/s = 1495°C = 70 J.Lm
o-dendrites
and quenched liquid (L). x 25
400J.Lm
Completely solidified
Figure 2 R = 2,O°C/s Tq = 1400°C d = 75 J.Lm Figures 2-4: Former o-dendrites, transformed to y by the peritectic reaction. x 25
400 J.Lm
x 25
400 J.Lm
Figure 3 R Tq d
=
0,5°C/s
= 1400°C = 110J.Lm
,·.l #
,f
•
,. .•.. ~
'"
-.
..
.. .,
,,.,'
j1r
,
If
Figure 4 R Tq d
..
4f
••
= 0,1°C/s
;.. t
= 1400°C
= 250J.Lm x 25
400 J.Lm
,
,
\
.
e'
36 • Steel 209
STEEL 209.
0,2 % C Cr Ni
lOW AllOY
STEEL
Designations SIS
AISI
Werkstoff
Nr
2512
Composition (wt-%) C
Si
Mn
p
S
Cr
Ni
Mo
Cu
v
0,20
0,25
0,90
0,014
0,039
0,81
1,05
0,06
0,07
0,02
fs
Thermal Analysis
0,0
T
0)
0,6
0,"
0,8
N
0,036
0,009
1,0
dT dt
CD
(QC)
(QC/s)
~ T
1500
.1,5 .1,0
1450 .0,5 0
1400
-0,5 1350
R
-1,0 -1,5
1300
= 0,5 C/s Q
0
100
200
Average
Liquidus
temperature,
ferritic
Temperature
of austenite
Temperature
of MnS-formation,
Solidus
temperature,
Solidification
QC
primary
formation,
CD
phase, QC QC
QC
CD
CD
CD
Solidification
Precipitates
MnS. The steel was resulphurized
(see figures
5-7).
Microsegregation Element
Cr
Ni
1,5
1,4
R = 0,5 QC/s Tq = 1370 QC
Cooling Rate,R, (OC/s) 0,5
0,1
1502
1502
1503
1474
1465
1474
time, s
1'(5)
2,0
1460-1420
range, QC
300
1460-1425
1420
1425
85 95
230
80
-1445 1445
60 750
Steel 209 • 37
Partly solidified
Figure 1 R Tq
d
= O,5°C/s = 1495°C = 60 fLm
o-dendrites
and quenched
liquid (L). x 25
400 fLm
Completely solidified
Figure 2 R = 2,O°C/s Tq = 1370°C d = 85 fLm Figures 2-4: Former o-dendrites, transformed to"y by the peritectic reaction.
)• -'
•
.r .•..
",,'
..•••.
--.~
- ..
..
. .. ..
"-
--' .. -
..
"
y
.
-'"
.-
..-
"-
R Tq d
= 0,5°C/s = 1340°C
= 100J1.m
,-
I
.••..
...
Figure 3
,
-" .-
x 25
••
•-.
I ,
••
..
"'.
I
" t 1JIl
I
••
..
•
• • •
I "
Figure 4 R Tq d
= 0,1°C/s
= 1340°C = 190J1.m x 25
Steel 214 • 47
STEEL 214.
0,5% C Cr
LOW ALLOY STEEL
Designations SIS
2230
AISI
Werkstoff
6150
1.8159
Nr
Composition (wt-%) C
Si
Mn
p
S
Cr
Ni
Mo
Cu
0,52
0,22
0,85
0,010
0,006
1,07
0,07
0,07
0,04
fs
Thermal Analysis
0,0
0,2
0,4
0,6
N
0,14
0,008
~0,004
1,0
0,8
dT d"t
T (OC)
(OC/s)
CD t
1500
+1,5
T
+1,0
1450 +0,5 0
1400
dT dt
-0,5
1350 -1,0 -1,5
R = O,soC/s
1300 0
200
100
300
't (5)
Average Cooling Rate,R, eC/s)
2,0 Liquidus Solidus
temperature, temperature,
austenitic °C
Solidification
range, °C
Solidification
time, s
CD
primary
phase, °C
CD
Small amount
carbides.
Microsegregation Element
1482
1482
1483
1385
1400
85
of interdendritic
Cr
V
2,1
1,9
R = 0,5°C/s Tq = 1310 °C
0,1
1380 100
Precipitates
0,5
95 250
80 740
48 • Steel 214 "'," .I
..-,
,
.:. L',:"~"'>
.' ; ,..-..
. '
"
. ~/
.'
",
( •
.
j
.I
,
.
/;
"
f
,f
'.
!A
f -
.!/
f
•..I ~ '.
.,•• ../
"
'.'
R Tq
y-dendrites
-.
;'..~:,~
.
Figure 1
\
.!r
f'
Partly solidified
0,5°C/s 1310°C 90 fLm
...J
,
J f
-
x 25
••
Figure 4 R Tq d
=
400
fLm
0,1°C/s 1310°C = 140 fLm x 25
Steel 215 • 49
STEEL 215.
0,55 % C Cr Ni Mo
LOW ALLOY STEEL
Designations SIS
Werkstoff
AISI
2550
Nr
1.2721
Composition (wt-%) C
Si
Mn
p
S
Cr
Ni
Mo
Cu
v
0,55
0,27
0,50
0,019
0,012
0,99
3,0
0,31
0,06
0,08
fs
Thermal Analysis
0,0
0,2
0,4
0,6
N
0,8
0,011
0,008
1,0
dT de
T (OCl
(OC/s)
1500 +',5
T 1450
0
1400
dT d't' 1350
-1,5
R
= O,5°C/s
1300
100
0
200
Average
Liquidus
temperature,
Temperature Solidus
austenitic
of formation
temperature,
°C
primary
of eutectic,
CD
phase, °C
CD
°C
300
T(s)
Cooling Rate,R, (OC/s)
2,0
0,5
0,1
1471
1471
1472
1365-1335 1335
-1370 1370
-1375 1375
Solidification
range, °C
140
100
75
Solidification
time, s
100
260
720
Precipitates
Interdendritic
carbide-austenite
eutectic,
Fe3P and MnS, (see figure 5).
Microsegregation Element
Cr
Ni
Mo
v
2,1
1,2
2,5
2,0
R
=
0,5°C/s
Tq = 1290 °C
Partly solidified
Figure 1 R
Tq d
= 0,5°C/s = 1465°C = 65 fLm
y-dendrites
400 fLm
and quenched
x 25
Completely solidified
""
.....•
,
"
l
,,J
Figure 2 R
= 2,0°C/s
Tq
=
1290°C d = 70 fLm Figures 2-4: y-dendrites,
400 fLm
J .../
...., t . 1
x 25
" ...j) :( -\ r
iT- .
f' ('.
·'A.-
\"
'",
"
"\.,.
"
,t.......,
Figure 3
"
".
R
= 0,5°C/s
Tq
= 1290°C = 90 fLm
d
400 fLm 1
x 25
\.
Figure 4 R
Tq '
•
. ;/J ..
liquid (L),
I
.
d
= 0,1°C/s 1290°C
= 130
fLm
x 25
Steel 215 • 51
Figure 5 R
Tq
= O,5°C/s = 1290°C
Interdendritic area with carbide-austenite eutectic (El, Fe3P and MnS. x 1000
52 • Steel 216
STEEL 216.
1,0 % C Cr
LOW ALLOY STEEL
Designations SIS
AISI
Werkstoff
2258
52100
1.3505
Nr
Composition (wt-%) C
Si
Mn
p
S
Cr
Ni
Mo
Cu
v
1,01
0,23
0,33
0,021
0,026
1,55
0,02
0,01
0,04
0,04
Thermal Analysis
Is 0,0
0,2
0,4
0,6
N
0,011
1,0
0,9
0,8
0,003
dT d't
T
CD t
(OC)
145O
(OC/s)
+',5
T
+',0 1400 .0,5
°
1350
-0,5 1300
-1,0 - 1,5
R = 0,5 C/s
125O
Average 2,0
Liquidus temperature, Temperature
Solidus temperature, Solidification Solification
austenitic
of formation C
primary phase, DC
of eutectic, QC
CD
CD
300
200
100
° CD
1450 1320-1270
range, C time, s
L(S)
Cooling Rate,R, ("C/s) 0,5
0,1
1450
1451
1340 -1300
-1300 ~1300
1270
1300
180
150
150
170
330
1400
Precipitates
1. Interdendritic Fe3P-carbide-austenite eutectic (14% Cr, 5% P). The eutectic figures 5 and 6), but was dissolved after homogenizing for 4 h at 1200 cC. 2. Interdendritic
MnS.
Microsegregation Element
Cr
2,6
R = 0,5 cCls Tq = 1250 cC
remained
after cooling
to 850 DC (see
Partly solidified
Figure 1 R Tq
= 1440°C
= 0,5°C/s
d
= 60
y-dendrites
JLm
and quenched
liquid (L). x 25
400
JLm
x 25
400
JLm
Completely solidified
Figure 2 R = 2,0°C/s Tq = 1250°C d = 75 JLm Figures 2-4: y-dendrites.
Figure 3
R Tq d
= = =
0,5°C/s 1250°C 90 JLm
'-.:a;
.---x 25
400
..• JLm
R..' ,,:' • 1'...,...
"...,.
.'
.
••
•
p
~
• ~.
..•..
,
;'
'
I
~:~
J
y
,0"
".
..•
•
~
,f
1
Figure 4
R Tq d
= = =
'
.•.. ••
x 25
400
JLm
I
•
.•
.-1 .. ,
V ..
~
f . ~~
#': . .)..~
,
IJ
~
0,1°C/s 1250°C 140 JLm
'-
'.1J
-'
4
.}
, .-
?
J.•..
•• :
.!:.'"
Figure 5 R = 2,0°C/s Tq = 1250°C Interdendritic Fe3P-carbide-austenite eutectic (E) (approximately 0,1 vol-%). The eutectic contains 14% Cr and 5% P.
'-E
x 1000 • t
•
Figure 6 R = 2,0°C/s Tq = 850°C After cooling to 850°C, small amounts of the eutectic shown in figure 5 remained. (Annealing for 4 h at 1200°C completely eliminated the eutectic.) x 1000
55
3. Chromium Steels Steels with chromium as the only, or the dominant alloying element are normally called chromium steels. The two common groups included here are steels with 5 and 13% chromium. In the first family the alloying addition is used to increase hardenability and to give the final product a favourable combination of strength and toughness. In the 13% Cr-steels, chromium imparts both corrosion resistance and strength. With reference to the structure of the steel products, the group comprises ferritic stainless (C < 0,08%), hardenable martensitic stainless (C ~ 0,09%), and low carbon hardenable martensitic stainless steels with 4-6% nickel. Because of their constitutional similarity at high temperatures, the 5 and 13% chromium steels are kept together in this work, rather than grouping the 13% Cr- steels with the Cr-Ni stainless materials.
Temperature
1600 I
1400
1300 1200 l+y+Kc
900
Si
301 302 303 304
0,13 0,35 0,50 0,96
0,4 1,0 1,0 0,3
Mn
Cr
0,4 0,5 0,5 0,7
5,0 5,2 5,1 5,2
Ni 0,2 0,2 0,1
Mo 0,6 1,3 1,4 1,2
V
l
a
Chromium steels are produced as castings and ingots of moderate size, continuous casting is unusual.
C
I
1500
1000
No.
5% Cr
I
l+a
Steels containing 17-25% chromium have not been examined. They are similar to the 13 % Cr-group in regard to solidification and structure at high temperatures.
Both the groups of steels investigated are made with a wide range of carbon contents. For a given chromium level the solidification mode is strongly dependent on carbon; this can be seen in the pseudobinary phase diagrams, figures 3.1 and 3.2. Account was taken of this effect of carbon when chosing the production steels for examination; these are given in tables 3.1 and 3.2:
;C
o
1
Weight Figure
3.1
Fe-5Cr-C
5% chromium
-4 -%carbon
system
Temperature~C %
1600 13 % Cr
1,0 1,2 0,2
1500 L
a Table 3.1
3
2
steels
1400 1300
No.
C
Si
Mn
Cr
Ni
305 306 307 308 309
0,04 0,07 0,14 0,32 0,69
0,5 0,5 0,2 0,2 0,4
0,6 0,5 0,7 0,3 0,6
13,4 12,9 12,0 13,9 13,1
5,5 0,2 1,2 0,2 0,2
%
1200
Table 3.2
13% chromium
1100 y+K2
1000
steels (see also table 4.1)
a 900 As indicated in figures 3.1 and 3.2 these grades cover the following solidification processes: •
primary ferrite formation
•
primary ferrite formation tion
•
by a peritectic
reac-
2
1
3 Weight - % carbon
Figure
followed
0 O'+y+K
3.2
Fe-13Cr-C
system
(Figures 3.1 and 3.2 after Bungardt (1958) 3, 193-203, Kc = Fe3 C, K,
=
et al. Arch. EisenhOttenw. M23C6, K2 = M7C3)
29
primary austenite formation
It should be noted that the pseudobinary phase diagrams are strictly valid for ternary Fe-Cr-C-alloys only. The superimposed lines for the commercial steel grades are therefore only indicative.
References The solidification of chromium steels has not been widely studied. General aspects of the process have been reported, [55-59]. Research work on microsegregation is described in references [60-64].
56 • Steel 301
STEEL 301.
0,1 % C
5 % CHROMIUM STEEL
Designations SIS
AISI
Werkstoff
501
1.7362
Nr
Composition (wt-%) C
Si
Mn
p
S
Cr
Ni
Mo
Cu
0,13
0,36
0,37
0,003
0,007
5,0
0,01
0,58
0,02
Thermal Analysis
fs
0)
T
0,4
0,6
0,8 0,9
v
W 0,01
N
0,01
0,009
0,006
1,0
dT d't
CD
(OC)
(OC/s)
~
1500
+1,5 +1,0
1450 +0,5 0
1400
-0,5
dT dt
1350
-1,0 -1,5
R
= 0,5 C/s
1300
Q
'[(5)
200
100
0
Average Cooling Rate,R, eC/s)
2,0 Liquidus
temperature,
Temperature Solidus
ferritic
of austenite
temperature,
QC
Solidification
range, QC
Solidification
time, s
primary
formation,
CD
phase, QC QC
CD
CD
Precipitates
Microsegregation Element
Cr
Mo
1,1
1,4
R = 0,5 QC/s Tq = 1375 QC
0,5
0,1
1508
1501
1506
1443
1426
1444
1405
1415
1440
105
85
65
85
190
790
Partly solidified
Figure 1 R = 0,5°C/s Tq = 1495°C d = 65 j.Lm o-dendrites and quenched liquid (L). x 25
400 j.Lm
Completely solidified
Figure 2 R = 2,0°C/s Tq = 1375°C d = 85 j.Lm Figures 2 - 4: Former o-dendrites, transformed to y by the peritectic reaction. x 25
400 j.Lm
x 25
400j.Lm
Figure 3 R Tq d
= O,5°C/s
= 1375°C = 160j.Lm
;. I 't .••••
".
Figure 4 R Tq d
= O,1°C/s = 1375°C = 275 j.Lm
",... ff
". J
x 25
400j.Lm
58 • Steel 302
STEEL 302.
0,35 % C Mo V
5 % CHROMIUM
STEEL
Designations SIS
AISI
Werkstoff
2242
H 13
1.2344
Nr
Composition (wt-%) C
Si
Mn
p
S
Cr
Ni
Mo
Cu
0,35
1,03
0,46
0,020
0,007
5,2
0,23
1,34
0,11
Thermal Analysis
Is
D)
0,0
T
0,4
0,6
W
v
N
0,091,00,013
0,026
1,0
0,8
dT dt
CD
(OC)
f
(OC/s)
1450
+1,5 +1,0
1400 +0,5 0
1350
-0,5 1300
-1,0 -1,5
R
1250
= 0,5 C/s Q
0
100
Average
Liquidus Solidus
0,1
1471
1464
1470
1370
1387
1412
1335
1360
1380
range, QC
135
105
90
time, s
100
250
990
ferritic
of austenite
Solidification
QC
primary
formation,
0)
phase, QC QC
CD
CD
Precipitates
Small amount
of eutectic
carbide.
Microsegregation Element
Cooling Rate,R, rC/s) 0,5
temperature,
Solidification
't (5)
2,0
temperature,
Temperature
300
200
Cr
Ni
Mo
v
1,2
1,0
1,5
1,7
R = 0,5 QCIs Tq = 1300 QC
Steel 302 • 59
Partly solidified
Figure 1 R = 0.5°C/s Tq = 1450°C d = 55fLm o-dendrites and quenched liquid (L). x 25
400 fLm
Completely solidified
Figure 2 R = 2.0°C/s Tq = 1300°C d = 70 fLm Figures 2-4: Former o-dendrites, transformed to y by the peritectic reaction. x 25
400 fLm
x 25
400 fLm
Figure 3 R Tq d
= 0.5°C/s = 1300°C = BOfLm
• ••~
.J '" .r
,)
Figure 4 R Tq d
=
=
OYC/s 1200°C 110j.Lm
400 j.Lm
x 25
and
interdendritic
Steel
304 • 65
.•...,. "
Figure 5 R = 2,0°C/s Tq = 1200°C Quenched liquid. x 1000
Figure 6 R = 2,0°C/s Tq = 1000°C Morphology of M7C3. x 1000
Figure 7 R = 2,0°C/s Tq = 1000°C Interdendritic distribution
of M 7 C3. x 150
I
,.
66 • Steel 305
STEEL 305.
0,04 % C
5 % Ni
13 % CHROMIUM
Werkstoff
Nr
STEEL
Designations SIS
AISI
Composition (wt-%) C
Si
Mn
p
S
Cr
Ni
Mo
Cu
W
0,04
0,54
0,61
0,010
0,009
13,4
5,5
0,07
0,07
0,01
fs
Thermal Analysis
0,0
T
0,2
0,6
0,4
0,01
N
0,019
0,032
1,0
0,8 0.9
dT dt (oC/s)
Q)
+CD
(OC)
v
+
T
1450
+1,5 +1,0
1400 +0,5 1350
0
---
dT dt
-0,5
1300
-1,0 -1,5
R
= 0,5°C/s
1250
Average
2,0 Liquidus temperature, Temperature
ferritic primary phase, °C
of austenite formation, °C
Solidus temperature, °C Solidification Solidification
CD
CD
CD
range, °C
Precipitates
Microsegregation Element
Cr
Ni
1,1
1,2
R =
O,5°C/s
Tq = 1350 °C
Cooling Rate,R, (OC/s) 0,5
0,1
1470
1476
1476
1410
1419
1425
1355
1395
1420
115
80
60
230
670
100
time, s
t(s)
300
200
100
0
Steel
Partly solidified
Figure 1 R = O,5°C/s Tq = 1473°C d = 75ILm I)-dendrites and quenched liquid (L). x 25
Completely solidified
Figure 2 R = 2,O°C/s Tq = 1350°C d = 140 ILm Figures 2-4: Formerl)-dendrites (D). White interdendritic areas (ID). Most of the I) transformed to y by the peritectic reaction. x 25
400 ILm
x 25
400 ILm
x 25
400 ILm
Figure 3 R Tq d
= 0,5°C/s = 1350°C = 240 ILm
Figure 4 R Tq d
= 0,1°C/s = 1350°C = 520 ILm
305 • 67
68 • Steel 305
Figure 5 R = 0,5°C/s Tq = 1200°C (d12oo = 260 Mm) Former 8-dendrites (D). White interdendritic areas (ID). Most of the 8 transformed to y by th9 peritectic reaction. 400 Mm
·1
\\
,
'. _."
.\
x 25
•
.
Figure 6
\.
R = 2,0°C/s Tq = 1350°C Residual dendritic in the y-matrix.
.'
ferrite (il)
x 600
~~
.
\ \.
;,\
\ '\
I
.
'~~
/ Figure 7
)
R =0,1°C/s Tq = 1350°C Residual dendritic in the y-matrix. x 600
ferrite (r';)
Steel
STEEL 306.
0,07 % C
306 • 69
13 % CHROMIUM STEEL
Designations SIS
AISI
Werkstoff
2301
410 S
1.4000
Nr
Composition (wt-%) C
Si
Mn
p
5
Cr
Ni
Mo
Cu
W
0,07
0,54
0,48
0,020
0,006
12,9
0,17
0,02
0,10
0,01
Average
Liquidus temperature, Solidus temperature,
ferritic primary phase, QC QC
CD
Temperature
of solid phase transformation
Solidification
range, QC
Solidification
time, s
CD CD
Precipitates
Microsegregation Element
Cr
Ni
1,0
1,0
R = 0,5 QC/s Tq = 1400 QC
::; 0,01
Cooling
N
0,026
0,039
Rate,R, (OC/s)
2,0
0,5
0,1
1497
1500
1500
1440
1455
1435 of ferrite to austenite, QC
v
1325-1270
1330-1290
65
60
45
80
210
610
Partly solidified
Figure 1 R Tq
d
= 0,5°C/s
= 1498°C = 90 Mm
o-dendrites and quenched liquid (L). 400 Mm
x 25
Completely solidified
Figure 2 R = 2,0°C/s Tq = 1400°C d = 205 Mm Figures 2-3: o-dendrites. Light interdendritic areas. (Interference contrast.)
400 Mm
x 25
Figure 3 R Tq d
= 0,5°C/s = 1400°C = 260 Mm
400 Mm
x 25
Figure 4 R = 0,1°C/s Tq = 1400°C d No dendrites visible due to absence of segregation. Austenite (dark) precipitated during quenching. 400 Mm
x 25
Figure 5 R = 0,5°C/s Tq = 1400°C Austenite from 1400 (dark C . ) precipitated
during
quenching .
0
x 25
400
JLm
Figure 6 R = 0,5°C/s Tq = 1200°C Austenite ( ) 12000C (SOli~ st~~:ciPitated during (d12oo= 270 JLm) transformation).
x 25
cooling
400
to
JLm
72 • Steel 307
STEEL 307.
0,1 % C
Ni
12 % CHROMIUM
STEEL
Designations SIS
AISI
Werkstoff
2302
(414)
1.4008
Nr
Composition (wt-%) C
Si
Mn
p
S
Cr
Ni
Mo
Cu
W
V
0,14
0,19
0,68
0,009
0,014
12,0
1,20
0,01
0,03
0,01
0,02
fs 0,0
Thermal Analysis
T
0,2
0,4
0,6
0,8
Altot
N
0,001
0,040
1,0
dT dt
.CD
(OC)
(OC/s)
T 1450
+1,5 +1,0
1400
+0,5 1350
-
0
Ql dt
-0,5
1300 -1, 0 1250
R = O,SQC/s
-1,5 0
100
200
Average
Liquidus
temperature,
Temperature Solidus
ferritic
of austenite
temperature,
C
Solidification
range, QC
Solidification
time, s
primary
formation,
CD
phase, QC QC
CD
CD
Precipitates
Microsegregation Element
Cr
Ni
1,1
1,3
R = 0,5 QCls Tq = 1360 QC
300
'[(5)
Cooling Rate,R, ( C/s)
2,0
0,5
0,1
1490
1495
1494
1416
1425
1401
1390
1400
1400
100
95
95
95
255
1070
Steel 307 • 73
Partly solidified
Figure 1 R = O,5°C/s Tq = 1493°C d = 75/-Lm o-dendrites and quenched liquid (L). x 25
400/-Lm
Completely solidified
Figure 2 R = 2,0°C/s Tq = 1360°C d = 150 /-Lm Figures 2 - 4: Former o-dendrites (D). White interdendritic areas (ID). (Most of the 0 transformed to y by the peritectic reaction.)
x 25
400/-Lm
x 25
400/-Lm
x 25
400/-Lm
Figure 3 R Tq d
= 0,5°C/s = 1360°C
= 180
/-Lm
Figure 4 R Tq d
= 0,1°C/s = 1360°C = 470/-Lm
74 • Steel 307
Figure 5 R = 0,5°C/s Tq = 1200°C (d12oo= 250 fLm) Former o-dendrites (D). White interdendritic areas (ID). (Most of the 0 transformed to y by the peritectic reaction.) 400 fLm
x 25
Figure 6 R = 2,0°C/s Tq = 1360°C Residual dendritic
,1
I
ferrite (0) in the y-matrix.
,
x 600 /
Figure 7 /
\'
'j
I
J
--~
R = 0,1°C/s Tq = 1360°C Residual dendritic ferrite (0) in the y-matrix. Figures 6-7: Note the influence of cooling on ferrite coarseness.
I x 600
rate
Steel 308 • 75
STEEL 308.
0,3 % C
14 % CHROMIUM STEEL
Designations SIS
AISI
Werkstoff
2304
(420)
1.4028
Nr
Composition (wt-%) C
Si
0,32
0,15
p
Mn
0,30
S 0,008
0,009
fs
Thermal Analysis
Cr
Ni
Mo
13,9
0,16
0,01
0,0
O,L.
v
Cu
W
0,01
0,22
0,03
0,8
0,6
N
0,003
0,013
1.0 dT dT
T (OC)
(OC/s)
1L.50
+1.5 +1.0
1L.00
+0,5 0 -0,5 1300
-1,0 -1.5
1250
R = 0,5°C/s
0
100
300
200
L
(5)
Average Cooling Rate,R, (OC/s)
2,0 Liquidus temperature, Temperature
ferritic primary phase, °C
of austenite formation,
Solidus temperature,
°C
CD
°C
CD
CD
0,5
0,1
1480
1483
1482
1400
1407
1401
1370
1375
1390
Solidification
range, °C
110
105
90
Solidification
time, s
100
290
1100
Precipitates
Interdendritic
ferrite, (see figures 7 - 8).
Microsegregation Element
Cr
Ni
1,2
1,0
R = 0,5 °C/s Tq = 1345 °C
76 • Steel 308
Partly solidified
Figure 1 R = 0,5°C/s Tq = 1410°C d = 75 fLm 8-dendrites (almost completely transformed to y) and quenched liquid (L), (compare figure 6). x 25
400 fLm
Completely solidified
Figure 2 R = 2,0°C/s Tq = 1345°C d = 75 fLm Figures 2-4: Former 8-dendrites, (transformed to y by the peritectic reaction), and interdendritic ferrite (8).
400 fLm
x 25
Figure 3 R Tq d
= 0,5°C/s = 1345°C = 100 fLm
x 25
Figure 4 R Tq d
= 0,1°C/s = 1345°C =210fLm
400 fLm
x 25
Steel 308 • 77
Figure 5 R Tq
= 0,5°C/s = 1200°C
(d12oo = 110 j.Lm)
Former o-dendrites, (transformed to y by the peritectic reaction), and interdendritic ferrite (0).
x 25
400 j.Lm
Figure 6 R = 0,5°C/s Tq = 1410°C Former o-dendrite, almost completely transformed to y by the peritectic reaction, with residual o in the centre. L = quenched liquid. x 150
Figure 7 R = 2,0°C/s Tq = 1345°C Interdendritic ferrite (0). x 150
Figure 8 R = O,5°C/s Tq = 1200°C Interdendritic ferrite (0). x 150
78 • Steel 309
STEEL 309.
0,7 % C
13 % CHROMIUM STEEL
Designations SIS
AISI
Werkstoff
Nr
Composition (wt-%) C
Si
Mn
P
S
Cr
Ni
Mo
Cu
W
V
Altot
0,69
0,43
0,64
0,014
0,005
13,1
0,20
0,07
0,02
0,22
0,03
0,002
Thermal Analysis
fs
0,0
0,2
0.4
0.6
0,025
0.95 1,0
0,9
0,8
N
dT dt (OC/s)
T (OC)
Q)
1450
~
+3.0 +2.5
1400
+2,0 1350
+1,5 +1,0
1300
1250
-t-- --
-dT dT
1200
-0,5 -1,0
1150
100
0
ferritic
Temperature
of austenite
Temperature
of formation
Solidus
Solidification
formation,
phase, QC QC
of eutectic,
CD
CD CD
CD
Cooling
0,5
0,1
1442
1448
1444
1422
1414 1240-1195
QC
Rate,R, (OC/s)
2,0
1250-1240
1415 1260-1245 1245
1195
1240
range, QC
245
210
200
time, s
160
405
2140
temperature,
Solidification
primary
t(s)
400
300
200
Average
temperature,
QC
Precipitates
Interdendritic M7C3-austenite (see figures 5-8).
eutectic.
The amount
of carbide
eutectic
increased
Microsegregation Element
0
-1,5
R = O,SQC/s
Liquidus
+0,5
G)© t 4
Cr
Ni
1,2
1,0
R = 0,5 QC/s Tq = 1240 C Q
with increasing
cooling
rate,
Steel 309 • 79
Partly solidified Figure 1 R = O,5°C/s Tq = 141BoC d = 50 fLm Former 8-dendrites, (completely transformed to y by the peritectic reaction), and quenched liquid (L). x 25
400 fLm
Completely solidified Figure 2 R = 2,O°C/s Tq = 1195°C d = 65 fLm Figures 2-4: Former 8-dendrites, (transformed to y by the peritectic reaction). Interdendritic carbide eutectic (compare figures 5-B). x 25
400 fLm
x 25
400 fLm
x 25
400 fLm
Figure 3 R Tq d
= 0,5°C/s = 1240°C = BOfLm
Figure 4 R Tq d
= O,1°C/s = 1240°C
=
130fLm
80 • Steel 309
, .J--'
"
f
, ..
~" /
.t
\..
">
""'\-;
.".
4
J
•... ~
l~~\
.,
'y "A..
.cv
'"
f
Figure 5 t
-\.
\
•
R = 0,5°C/s Tq = 1240°C Interdendritic M7C3-Y eutectic. 3,5 vol-% carbide . 100 Mm
x 150
il..
Figure 6 R Tq
= 2,0°C/s
= 1195°C M7C3-Y eutectic. 4,5 vol-% carbide. 25 Mm
x 600
.0
Figure 7
R
= 0,5°Cts
= 1245°C M7C3-Y eutectic (E) and small amounts of
Tq
liquid (L).
f .I
I,
25 Mm
x 600
Figure 8 R Tq
= 0,1°C/s =
1240°C
M7C3-Y eutectic. 2,4 vol-% carbide. 25 Mm
x 600
81
4. Stainless and Heat Resistant Steels The main alloying element is chromium in amounts between 12 and 30%. Most common stainless steels also contain considerable quantities of other alloying elements of which molybdenum and nickel are the most important. The main object of these additions is to increase the corrosion resistance of the steel and to control the phase composition of the microstructure in the final product. Most commercial stainless and heat resistant steels are found in the following range of standardized compositions, table 4.1: Structure
of the steel product
Ferritic
Martensitic
Ferritic-austen
itic
Austenitic Table 4.1
Classification
Cr
C
Ni%
-0,08 -0,10 -0,25 -0,08 0,090,15-
12-14 16-19 24-28 12-14 12-14 16-18
1,3-2,5
-0,10
18-30
4,5-14
-0,50
16-26
7-35
3-6
Other common alloying elements are molybdenum up to 5% and copper up to 3%. Nitrogen, which is usually present at residual levels of about 0,03-0,06%, can also be used as an alloying addition of up to 0,2%. Austenitic steels are produced as castings, ingots of all sizes and as continuously cast billets and slabs. The other types of stainless and heat resistant materials mentioned in table 4.1 are cast predominantly as ingots of a moderate size, although martensitic and ferritic-austenitic steels are also commonly used as castings. The solidification behaviour is governed by the proportions of austenite- and ferrite-forming elements present. The first group comprises carbon, nitrogen, nickel, manganese, copper and cobalt. (At high concentrations manganese has been reported to be a ferrite former, [66].) The most important ferrite formers are chromium, silicon, molybdenum, niobium, titanium and aluminium. The ferritic and martensitic grades have already been described in chapter 3. The alloys of the present section, belonging to the ferritic-austenitic and the austenitic groups were chosen to give examples of the different solidification paths. The alloys are listed in table 4.2 in order of increasing tendency to solidify as austenite: No.
C
Si
Mn
Cr
Ni
Mo
401 402 403 404 405 406 407 408 409
0,04 0,01 0,02 0,04 0,07 0,05 0,02 0,05 0,02 0,01 0,06 0,13 0,01 0,41 0,07
0,9 0,3 0,3 0,4 0,6 0,4 0,5 0,6 0,6 0,2 1,2 0,5 0,5 1,0 0,6
0,8 1,8 0,9 1,2 1,4 1,7 1,6 1,7 1,8
25,1 19,8 19,5 18,4 17,2 17,2 17,2 17,7 17,4
4,7 9,9 10,3 9,1 10,3 12,6 13,5 13,4 12,8
1,2
1,8 1,8 1,7 1,7 1,3 0,6
25,1 24,2 24,3 19,2 25,2 21,1
22,2 20,4 20,5 25,1 20,6 31,0
Table 4.2
The types of solidification
are:
•
primary ferrite formation
•
primary ferrite formation followed reaction between liquid, 0 and y.
•
primary ferrite and austenite formation
•
primary austenite formation
by a three-phase
In this work the transition 0 + liquid ~ y is called peritectic reaction as long as the 0- phase is in direct contact with the liquid. When 0 is completely surrounded by y -phase and the reaction rate is governed by solid state diffusion of the alloying elements through y, the process is denoted peritectic transformation. The relative amount of austenite usually increases below the solidus temperature, i.e. the remaining o-ferrite content is dependent on temperature. In alloys with a high carbon content carbides precipitate during solidification.
of stainless and heat resistant steels
The structure of the filial product should not be confused with the structures present during and immediately after solidification. Many austenitic steels for instance contain considerable quantities of ferrite in their solidification structure.
410 411 412 413 414 415
The choice of these alloys was based on the solidification modes indicated by the pseudobinary phase diagrams, such as that shown in figure 4.1.
0,4 0,5 2,8 2,6 2,7 2,8
Others%
0,5 Ti 0,5 Nb
0,19 N
2,3
4,4
Stainless and heat resistant steels
1,5 Cu
Temperature,OC 1500
L+
1400
Y
y
1300
1200
1100
o
5
10
15
20
I
I
I
I
I
30
25
20
15
10
Figure 4.1 Phase diagram Fe-Cr-Ni Handbook, Vol 8, 1973,424-425)
25 30 Weight-% Ni I
I
5 0 Weight-% Cr
at 70% Fe. (After
Metals
References The solidification of stainless and heat resistant alloys has been the subject of many research reports. Papers on general aspects of solidification and phase equilibria include references [65-77]. Quantitative discussions of microsegregation have been presented, [68, 69, 71, 73, 77-82]. Finally, solidification under welding conditions received attention, [72, 79, 83-86].
has also
82 • Steel 401
STEEL 401.
0,04 % C 25 % Cr 5 % Ni Mo
STAINLESS STEEL
Designations SIS
AISI
Werkstoff
2324
(329)
(1.4460)
Nr
Composition (wt-%) Si
Mn
0,86
0,76
C
0,042 Creq Nieq
_ -
S
P
0,031
0,010
Cr
Ni
Mo
Cu
25,1
4,7
1,22
0,08
Altot
Co
0,08
N
,:::;0,002
0,077
4,01
fs Thermal Analysis
0.0
T
0.2
0,4
0,6
0.8
1,0
dT dt
.CD
(OCl
(OCls)
T
1450
+1,5 +1.0
1400
+0.5 1350
--
0
dT dt
-0.5
1300
-1.0 -1.5
R
1250
= 0,5°C/s
0
100
200
Average
2,0 Liquidus temperature, Solidus temperature, Solidification
ferritic primary phase, °C °C
CD
CD
range, °C
Solidification
time, s
Fraction solidified
as ferrite, %
300
Cooling Rate,R, (OC/s)
0,5
1465
1471
1469
1410
1420
75 80
60
50
205
770
100
100
100
M23C6particles and austenite in grain boundaries and M23C6particles in the matrix, (see figures 5-8). The carbide and austenite were precipitated during quenching from 1360°C.
Element
Mn
Cr
Ni
Mo
1,3
1,0
1,2
1,3
R = 0,5 °C/s Tq = 1360 °C
0,1
1390
Precipitates
Microsegregation
t (s)
Steel 401 • 83
Partly solidified
Figure 1 R = 0,5°C/s Tq = 1468°C d = 70 JLm a-dendrites and quenched
liquid (L).
x 25
400 JLm
Completely solidified
Figure 2 R 2,0°C/s Tq 1360°C d 115 JLm Figures 2-4: a-dendrites. White interdendritic areas (ID). Grain boundaries (G) also visible.
x 25
Figure 3 R Tq d
0,5°C/s 1360°C 280 JLm x 25
Figure 4 R Tq d
= 0,1°C/s = 1360°C = 550JLm
x 25
84 • Steel 401
Figure 5 R Tq A B C
= O,5°C/s = 1360°C
grain boundary with austenite. grain boundary with carbide particles. ferritic matrix with carbide and austenite precipitates.
100 f-Lm
,
, "
.
x 150
/' \J
' , \1"
Figure 6 R = 0,5°C/s Tq = 1360°C Austenite, formed during boundary as in fig 5 at A.
quenching,
in grain
x 1000
Figure 7 R = 0,5°C/s Tq = 1360°C Carbide particles (M23C6), formed during quenching, in a grain boundary as in fig 5 at B. Electron micrograph of thin foil (TEM).
x 30000
Figure 8 R = 0,5°C/s Tq = 1360°C Carbide particles (M23C6), formed during quenching, in the ferritic matrix as in fig 5 at C. Electron micrograph of thin foil (TEM). x 15000
Steel 402 • 85
STEEL 402.
0,01 % C 20 % Cr 10 % Ni
STAINLESS STEEL
Designations SIS
AISI
Werkstoff
30BL
1.4316
Nr
Composition (wt-%) C
Si
Mn
P
S
Cr
Ni
Mo
Cu
Co
Altot
N
0,012
0,31
1,76
O,OOB
O,OOB
19,B
9,9
0,10
0,04
0,02
0,004
0,031
Creq Nieq
= 1,B2 fs
Thermal Analysis
0,2
0,0
T
0,6
0,4
1,0
0,8
dT dt
CD
(OC)
t 1450
(OC/s)
T
+1,5 +1,0
1400
+0,5 1350
--
0
dT dt
-0,5
1300
-1,0 -1,5
1250
R = 0,5°C/s
0
Average
Liquidus temperature, ferritic primary phase, °C Temperature of austenite formation, °C Solidus temperature, °C Solidification
range, °C
Solidification
time, s
CD
CD
(3)
Fraction solidified as ferrite, %
Precipitates
Microsegregation Element
Si
Mn
Cr
Ni c _ n ~ 0f'./c
300
200
100
Cooling
'('(5)
Rate,R, (OC/s)
2,0
0,5
0,1
1447 1366 1325 120 105 92
1454 1391 1360 95 255 91
1449 1405 1390 60 690 97
86 • Steel 402
Partly solidified
Figure 1 R 0.5°C/s Tq 1450°C d 60 [Lm o-dendrites and quenched liquid (L).
400
[Lm
x 25
Completely solidified
Figure 2 R 2.0°C/s Tq 1325°C d 150[Lm Figures 2-4: Former o-dendrites (D). White interdendritic areas (ID). (Most of the ,) transformed to y by the peritectic reaction and transformation.) x 25
Figure 3 R Tq d 400
0.5°C/s 1325°C 270 [Lm x 25
[Lm
Figure 4 R Tq
O.1°C/s 1325°C
Steel
Figure 5 R Tq
= 0,5°C/s = 1200°C
= 300 JLm) Former o-dendrites (D). White interdendritic areas (ID). (Most of the 0 transformed to 'Y by the peritectic reaction and transformation.) (d1200
x 25
400 JLm
Figure 6 R = 2,0°C/s Tq = 1325°C 13 vol-% dendritic ferrite. Figures 6-9: Note that the residual ferrite only appears in the former o-dendrites.
x 150
Figure 7
Figure 8
R = 0,5°C/s Tq = 1325°C 19 vol-% dendritic ferrite (0).
R = 0,5°C/s Tq = 1200°C 9 vol-% dendritic ferrite (0). x 150
Figure 9 R = 0,1°C/s Tq = 1325°C 20 vol-% dendritic ferrite. x 150
402 • 87
88 • Steel 403
STEEL 403.
0,02 % C 19 % Cr 10 % Ni
STAINLESS STEEL
Designations SIS
AISI
Werkstoff
(2352)
304L
1.4316
Nr
Composition (wt-%) C
Si
Mn
P
S
Cr
Ni
Mo
Cu
Co
Altot
N
0,019
0,31
0,94
0,009
0,010
19,5
10,2
0,11
0,03
0,05
0,002
0,044
Creq Nieq
= 1,74
fs
Thermal Analysis
0,0
T (OCl
0,2
0,4
0,6
0,80,9
1.0 dT dT (OC/s)
CD + T
+1,5 +1,0
1400
+0,5 1350
-
0 dT dT
-0,5
1300
-1.0 -1,5
R = O,soC/s
1250 0
100
200
Average
2,0 Liquidus
temperature,
Temperature Solidus
ferritic
of austenite
cC
temperature,
primary
formation,
CD
phase, °C °C
CD
CD
300
'[(5)
Cooling Rate,R, (CC/s)
0,5
0,1
1447
1455
1453
1404
1415
1418 1405
1365
1390
Solidification
range, °C
80
65
50
Solidification
time, s
90
220
610
91
92
98
Fraction
solidified
as ferrite,
%
Precipitates
Microsegregation Element
Si
Mn
Cr
Ni
I
1,6
1,5
1,1 1,2
1,5 0,7
PD
R = 0,5 °C/s Tq = 1340 °C
Partly solidified
Figure 1 R = 0,5°Cts Tq = 1450°C d = 65 jLm Ti(C,N) + y)
10 fLm
x 1000
Ti(C,N).
Figure 9 R = 2,O°C/s Tq = 1320°C 6 vol-% dendritic ferrite. . Figures 9 -12: Note that the r~sidual fernte only appears in the former 8-dendntes (D).
x 150
100
JLm
x 150
100
JLm
x 150
100
JLm
Figure 10 R = O,5°C/s Tq = 1320°C . 8 vol-% dendritic fernte.
Figure 11 R = O,5°C/s Tq = 1200°C 4,1 vol-% dendritic ferrite
~ {/- .'
-. ".'
\
l
"
'\)
.
"
~
.
•. J
,/
,
,
\
b
\ \. ".",
Figure 12 R = O,1°C/s Tq = 1320°C 4,8 vol-% dendritic ferrite
..
t
x 150
100
JLm
-
'--: ..
.
?
" 1 l
(/ 'j
, /~
.. ).
//
1 '\
'"
.
98 • Steel 406
STEEL 406.
0,05 % C 17 % Cr 12 % Ni 2,8 %Mo Nb
STAINLESS STEEL
Designations SIS
AISI
Werkstoff
316 Cb
1.4583
Nr
Average
2,0 Liquidus
temperature,
ferritic
and austenitic
Temperature
of maximum
Temperature
of carbide formation,
Solidus
temperature,
Solidification
°C
rate of formation
CD
QC
CD
primary
phases, QC
of austenite,
QC
CD
CD
Solidification time, s Fraction solidified as ferrite,
%
Precipitates
1. Interdendritic ferrite, (see figures 4, 6 -11). 2. Eutectic NbC, (see figures 6,7,9-11).
Microsegregation Element
Si
Mn
Cr
Ni
I Po PlO
1,7
1,5
1,1 1,3 1,1
1,4 0,6 0,8
R = 0,5 QC/s Tq = 1285 QC
0.,5
0,1
1420
1423
1424
1410
1418
1417
1330-1275
range, °C
Cooling Rate,R, (OC/s)
1330-1290
1330-1305 1305
1275
1290
145
130
120
130
300
1240
" .... ~
1 ..•.
Figure 9 J
R = 2,0°C/s Tq = 1320°C 5,5 vol-% ferrite, dendritic tic (100).
(i,
. --.
,...,
f.~. ~; .
I
--
"''.
(Do) and interdendriV
;/
x 150
\
100 fLm '"". of"
• I
(
J.
r-"
/'-:
,
'(
" '.J,"4"j. 1'1'
••.
{,
"
Figure 10 R = 0,5°C/s Tq = 1320°C 5,6 vol-% ferrite, mainly interdendritic
• (100). ,~,
x 150
/
I1
j)
~ Figure 11 R = 0,5°C/s Tq = 1200°C 3,5 vol-% ferrite, mainly interdendritic
108-
e,/. 15
(100).
)7 ~ {I
x 150
~
/
•
\ L
{ ()
( 7 Figure 12 R = 0,1°C/s Tq = 1320°C 4,4 vol-% ferrite, mainly interdendritic
(100).
•
o
,
~
-
•