Note: Descriptions are shown in the official language in which they were submitted.
1148747
Description
FILLED TUBULAR ARTICLE AND METHOD
FOR CASTING BORON TREATED STEEL
Technical Field
This invention relates generally to casting
of boron treated steel, and more specifically to an
improved filled tubular article and method of controlled
insertion of preselected materials within the filled
tubular article into the molten metal as it is being
cast.
Background Art
_ _ .
Up to the present time a number of difficul-
ties have been experienced with the continuous casting
of boron treated steels because of the need to add
boron, alloying elements, deoxidants and denitriders to
the molten metal near the time of pouring. For example,
such steels have been typically produced by adding
aluminum to the molten metal immediately prior to the
introduction thereof into the mold. However, the
aluminum in these aluminum killed steels forms oxides
and a reaction with the silicates in the melt to plug
the nozzles that meter the molten metal to the tundish
and to the mold. Titanium also forms oxides and tends
to plug the nozzles in much the same way. Such slag
formation at the nozzles not only detrimentally affects
the controlled flow rate of molten metal into the mold,
but detrimentally affects the ratio of external surface
area of the poured stream to the total stream cross
section so that there is undesirably an increased
oxidation and nitriding tendency. The formation of
slag also detracts from the amount of residual aluminum
available for obtaining the desired grain refinement.
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The material additions such as titanium,
zirconium and boron, in singular or combined form,
which have been made to the tundish or ladle to improve
the response of the material to heat treatment have
heretofore been relatively ineffective because there
has been a reaction with the atmosphere and a fading
phenomena as a result of prolonged exposure of the
additional materials to the atmosphere at the elevated
temperature. In other words, the article or billet
that is formed has a less homogeneous and coarser
structure than it should have for the expense of the
material additions and a lower hardenability than is
desired. Typically, several feet of the continuously
cast billets are not usable because of imperfections,
and so such sections are cut off resulting in a waste
of time and material.
Another approach to minimizing the exposure
of the highly reactive additive materials to the atmo-
sphere is to shroud the outlet stream and/or to use an
inert gas such as argon to isolate the stream as it is
being poured into the mold. Obviously, this adds a
considerable cost to the process.
Less prevalent in the continuous casting of
boron treated steels is the introduction of an aluminum
alloy rod near the entry to the mold as is recommended
by Kawecki Berylco Industries, Inc. of Reading, Pennsyl-
vania. This late addition of aluminum, as well as
preselected amounts of titanium and boron integrally
formed with the aluminum, has been only partially
satisfactory. This is in part due to the aluminum alloy
rod melting prematurely so that there is an undesirable
reaction with the atmosphere that decreases the effec-
tiveness of the material additions, and in part due to
a less than satisfactory selection of the basic elements
and their proportions.
8747
Even though the advantageous teachings of
U. S. Patent No. 3,991,808 issued to J. R. Nieman,
et al on November 16, 1976 have been widely recognized,
such teachings have not resulted in the formation of a
single additive rod capable of effectively making boron
treated steel and while taking into account the diverse
chemical reactions that occur. Not only do the reaction
capabilities of the materials of the rod itself have to
be taken into proper account, but also one must consider
the reaction thereof to the composition of the molten
metal and to the gases in the atmosphere. Furthermore,
the flexibility of the rod must be maintained to permit
coiling thereof on a containment reel. Hence, the
additive rod cannot be too stiff or brittle, and if
lS particulate material is contained within the rod it
should be capable of being drawn for improved densifi-
cation thereof.
Thus, what is desired is a single rod, capable
of being easily handled and fed into molten steel, and
containing such hardenability intensifiers and additives
as are precisely tailored for the production of fine
grain, boron treated steels in an effective and economi-
cal manner. As one would suspect, the full boron effect
is likely to be obtained only with a rod having a
preselected construction and material composition. In
this regard, it should be recognized that a substantial
number of inoculating rods are known to the industry
which are constructed specifically for completely
different casting purposes. For example, the following
U. S. patents disclose inoculating rod constructions
which are representative of the general state of the
art:
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~1~87~7
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3,056,190 to D. S. Chisholm, et al on October
2, 1962;
3,367,395 to S. I. Karsey on February 6, 1968;
3,921,700 to J. G. Frantzreb, Sr. on November
25, 1975;
3,911,993 to M. L. Caudill, et al on October
14, 1975; and
4,174,962 to J. G. Frantzreb, Sr. et al on
November 20, 1979.
However, such inoculating rods are totally
unsatisfactory for making boron treated steels.
The present invention is directed to overcoming
one or more of the problems as set forth above.
Disclosure of the Invention
In accordance with one aspect of the present
invention a filled tubular article is provided for
controlled dissolution in a molten metal for making
boron treated steel, the filled tubular article having
an elongate conduit of ferrous material, an elongate,
non-particulate member of primarily aluminum material
in the conduit, and a master composition including
ferroboron particulate material, ferrotitanium
particulate material, and ferrovanadium particulate
material in the conduit.
In a further aspect of the invention a method
of casting a boron treated steel article by introducing
molten steel into a mold includes introducing a filled
tubular article into the molten steel having an
elongate conduit of ferrous material, an elongate
non-particulate member of primarily aluminum material
in the conduit, and a particulate master composition
including ferroboron material, ferrotitanium material
and ferrovanadium material contained in the conduit.
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747
Advantageously, the instant invention has
successfully made boron treated steel in a continuous
as-cast round bar manufacturing facility by introducing
preselected amounts of ferroboron, ferrotitanium, and
ferrovanadium particulate materials and an aluminum rod
in a protective conduit and effecting melting thereof
at a preselected depth below the level of the molten
steel in the mold. Its success has been determined by
a study of boron factors, performance criteria, and
chemical analyses of the elements of a plurality of
heat-treated parts including experimental tests and
comparison base tests.
Brief Description of Drawinqs
Fig. 1 is a diagrammatic, elevational view of
a continuous casting facility including an apparatus
for progressively feeding a filled tubular article
constructed in accordance with the present invention
into the molten metal in the mold.
Fig. 2 is an enlarged, fragmentary and
diagrammatic elevational view of the upper portion of
the casting facility of Fig. 1 with a portion
illustrated in section to better show details of the
present invention.
Fig. 3 is an enlarged, diagrammatic, cross
sectional view of the filled tubular article
illustrated in Figs. 1 and 2.
Fig. 4 is a graph showing the relationship
between actual boron factor and carbon content.
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Fig. 5 is a tabular listing of seven experi-
mental rod members and the additive material ratio
additions in each.
Best Mode for Carrying Out the Invention
Referring to Figs. 1 and 2 a rotary continuous
casting facility 10 is illustrated of the type utilized
by the MacSteel Division of Quanex Corporation and
located in Jackson, Michigan. Such facility produces
continuous as-cast round bars by utilizing a large
bottom pour ladle 12 to pour argon-gas-stirred molten
steel 13 into a tundish 14. Liquid steel is teemed
from the tundish via a bent nozzle 16 having a relatively
small outlet opening at 18, for example about 16 mm
(5~8") dia., and into a water cooled mold 20 at a
precise angle with respect to a central vertical axis
22. The generally cylindrical mold 20 is of copper and
has a precisely contoured or tapered internal bore 24
to allow for solidification shrinkage and to maintain
mold contact with the solidifying hot bar for optimum
cooling.
As is diagrammatically indicated in Fig. 2,
the copper mold 20 has an enlarged annular head portion
or top end 26 and a lower cylindrical body portion or
bottom end 28, and vertically spaced apart seal means
30 are provided between the mold and a suitable support
member 32 to define a chamber 34 through which liquid
coolant such as water is circulated. Through a mechanism,
not shown, the mold 20 is oscillated at a rate of about
60 cycles per minute through a range of about 16 mm
(0.625") in the direction of the vertical axis 22 on
which it is centered, while at the same time it is
rotated at a speed of about 60 revolutions per minute
as is schematically shown in Fig. 1 by the movement
indicating arrows "A" and "B" respectively. The emerging
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bar or strand depends from the mold and passes through
a water spray system 35. Thereafter the bar is cut to
length by a carriage mounted saw, not shown, that
clamps to the bar and travels with it during the cut.
In actuality, the continuous casting facility
10 so far described and used during the development of
the present invention, is a twin strand unit having
side-by-side molds 20 and associated nozzles 16 to
allow simultaneous manufacture of a pair of bars.
Since the construction and operation of each strand is
the same, a description of one can suffice for the
other and only one unit need be illustrated in the
drawings. The straight bar length or overall height
"OH" is about 10 m (33'), and the bar diameter "D" can
be varied from, for example, about 100 to 180 mm (4 to
7").
An apparatus for introducing additives into
the casting mold 20 is generally indicated by the
reference numeral 36. The additives utilized in the
present invention are in the form of a relatively
ductile filled tubular article or treating rod 38
having a lower or distal end 40. The filled tubular
article is progressively urged downwardly when viewing
the drawings by a wire feed mechanism 42 which unreels
the article from a rotatable reel 44. A feed rate of
about 64 mm/sec. (2 12"/sec.) was found to be satisfac-
tory in one instance. A hollow tubular guide member 46
is located below the feed mechanism, and is generally
aligned with a plane through the central axis 22;
however, the guide member has a preselected angle of
inclination with respect to the axis so that the distal
end 40 of the filled tubular article is below a surface
48 of the molten steel 13 in the mold 20 by a preselected
distance "L" as indicated in Fig. 2 and so that the
distal end is adjacent the central axis thereat. For
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~48747
further details of the apparatus 36 reference is made
to U. S. Patent No. 3,991,808 issued November 16, 1967
to J. R. Nieman, et al.
Thus, it can be appreciated that as the
molten steel 13 is added to the mold 20 the filled
tubular article 38 melts at its distal end 40 to add
preselected materials below the surface 48 simultaneously
with reciprocation and rotation of the mold. Moreover,
heat is removed from the copper mold by the water in
the chamber 34, and progressive solidification occurs
at the periphery of the tapered bore 24 so that a
cylindrical bar 50 is continuously formed along the
axis 22. In the instant example the retraction rate or
formation rate of the bar is about 2m/min. (79"/min.).
It is to be understood that the central part of the bar
does not immediately solidify, but rather the solidifi-
cation progresses radially inwardly with time and with
the downward movement of the bar. This phenomena is
graphically or schematically portrayed in Fig. 2 by the
tapered phantom solidification demarcation lines desig-
nated by the reference numeral 52. At a distal end 54
of the downwardly converging lines 52 the liquid center
of the treated molten metal has solidified. For example,
the distal end 54 is typically reached at a distance
"H" of about 5.5m (18') from the top of the mold for a
bar diameter of about 140mm (5.5").
With reference now to the cross sectional
view of Fig. 3, the filled tubular article 38 can be
seen to include an elongate metal conduit 56, an elongate,
non-particulate member 58 located within the conduit,
and a preselected particulate master composition 60
compactly contained within the conduit. Specifically,
the master composition 60 includes ferroboron, the non-
particulate member 58 is primarily of aluminum material,
and the conduit 56 is of preferably a ferrous material
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~87~7
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for formability. For example, the conduit 56 can have
the following composition in percentage by weight:
C About 0.10%
Mn 0.25 - 0.50%
S About 0.05%
P About 0.01%
Fe Balance
I have determined that the master composition
60 should preferably include preselected weight percent-
ages ~f ferrotitanium and ferrovanadium particulate
materials intermixed with a preselected weight percent-
age of ferroboron particulate material. I have found
it desirable to compact the master composition 60
within the conduit 56 to a relatively dense state in
order to assure rapid internal dissolution of the
conduit. For example, the preferred density of the
core is equivalent to a degree of compaction in excess
of 10% above the tapped density thereof. The term
"tapped density" as used herein, refers to the known
procedure described in "HANDBOOK OF METAL POWDERS" -
Poster, Reinhold Publishing Co., New York, New York,
1966, page 57.
r~qOre particularly, I have found that boron
treated steel can be made best by progressively inserting
a filled tubular article 38 consisting essentially of
the following elements in the proportions indicated
into and below the surface of molten metal in the mold:
BroadPreferred Most
Range Range Desirable
(Wt.%)* (Wt.%)* (Wt.%)*
1) aluminum 0.015 - 0.070 0.015 - 0.030 0.016
portion of
member 58
2) boron 0.0008 - 0.00462 0.0011 - 0.00308 0.0018
portion of
ferroboron
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3) titanium 0.038 - 0.150 0.038 - 0.088 0.050
portion of
ferrotitanium
4) vanadium 0.022 - 0.147 0.044 - 0.103 0.044
portion of
ferrovanadium
*Note: Reflected as a percentage of the molten metal
addition to the mold.
I make note that the ferrous metal portions
of the protecting conduit 56 and the selected three
particulate materials designated immediately above is
not significant since such ferrous portions have a
negligible diluent influence on the molten metal.
Rather this compatibility factor can be utilized with
advantage because ferroalloys of boron, titanium and
vanadium are available in the marketplace at economical
prices and because the reaction thereof is more tame
than the reaction of the purer basic element forms.
Another way to state the preferred material
relationship is to designate the ratio of the four ele-
ments as about 9:1:28:24 which reflects the weight
analysis ratio of aluminum, boron, titanium and vanadium
in the filled tubular article 38.
In the aforementioned preferred composition
of the novel filled tubular article 38, low cost aluminum
serves as an effective deoxidizer and denitrider and
imparts the desired degree of grain refinement in the
cast article by removing dissolved gases from the melt.
Above a level of about 0.070 Wt.% the ductility of the
cast article can be expected to be adversely affected
and an undesired amount of inclusions noted therein.
Below a level of about 0.015 Wt.~ the amount would be
ineffective as a grain refiner. It must be present in
a non-particulate or non-powder form for the reason
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~487~7
11
that if aluminum ~ere present in the form of xelatively
small particles an excessive amount of external surface
area would be provided; such larger surface area would
at least partly oxidize even within the confines of the
conduit 56, for example, and result in a marked decrease
in effectiveness of the aluminum additive. While I
prefer that the aluminum member 58 be present as a
cylindrical rod centrally located within the conduit
56, I also contemplate that it could be formed as a
coating on the inside surface of the conduit. However,
if the conduit itself were made of aluminum such
construction would be unsatisfactory because the larger
surface area thereof would be exposed to the atmosphere
and it would melt too fast so that the aluminum and
master composition 60 would be prematurely exposed to
atmospheric contamination. The aluminum that I used
was over 99~ pure since it is commercially available in
that form.
Ferroboron particulate material provides the
desired degree of hardenability to the steel article
while replacing an appreciable percentage of more
expensive alloying ingredients. Above a boron level of
about 0.00462 Wt.% an undesirable secondary reaction
occurs involving the precipitation of iron borides that
tend to embrittle the article. Below a level of about
0.0008 Wt.% there is insufficient boron available to
provide the hardenability effect on the heat treat of
the article. The ferroboron particulate material that
I used had 17 1/2 Wt.% boron.
The preferred addition of ferrotitanium
serves as a powerful deoxidizer and denitrider. Above a
titanium level of about 0.150 Wt.~ there is so much
titanium that some would be available to link up with
the carbon and detrimentally affect the heat treatment
capability of the cast article and its hardenability.
This is so because titanium is an exceptionally strong
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~48747
carbide former. Furthermore, the formation of stable
inclusions can occur that would adversely affect machin-
ability. Below a titanium level of about 0.038 Wt.%
the effectiveness of the boron addition would be
minimized since the boron would tend to link with the
available oxygen and nitrogen in place of titanium.
The ferrotitanium particulate material that I used had
70 Wt.% titanium.
Lastly, the preferred ferrovanadium addition
serves as a somewhat weaker deoxidizer, a stabilizer, a
hardenability agent, a grain refiner and a means of
increasing the strength of the boron steel article.
Above a level of about 0.147 Wt.% vanadium there would
be massive carbide precipitation that would result in a
loss of hardenability. Below a level of about 0.022
Wt.% there would not be the degree of system stability
desired; in other words, there would be an excessively
large variation in the microstructure and hardenability
of the final product article. Moreover, there would be
an undesirable loss in strength if the level is below
that recommended. The ferrovanadium particulate
material that I used had 54 Wt.% vanadium.
With the aforementioned proportions, about
50% of the total weight of the master composition 60 is
ferrovanadium, about 43 1/2% is ferrotitanium, and
about 6 1/2~ is ferroboron.
Industrial Applicability
Initially, expeximental tests were conducted
on casting boron steel by introducing a filled tubular
article including a metallic sheath containing pre-
selected additives into the molten metal flowing into a
casting mold substantially as set forth in U. S. Patent
No. 3,991,808 mentioned previously. One of the objects
of the testing was to try to obtain a satisfactory
boron factor at a reasonable cost, and without adding
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1148747
undesirable amounts of the additives to the chemical
analysis of the final castings.
In connection with the so-called boron factor,
reference is made to the pioneering work of Marcus A.
Grossman, such as his AIME Paper of February, 1942 on
Hardenability Calculations from Chemical Compositions,
and to ASTM Specification A255 relating to a standard
method of End-Quench Test for hardenability of steel.
The actual boron factor is generally defined as the
actual D.I. in inches calculated from Jominy divided by
D. I. in inches calculated from the chemistry (without
boron). When steel is properly made, the boron factor,
or its contribution to increased hardenability, is an
inverse function of the carbon content. The higher the
amount of carbon, the lower the boron factor and the
less the contribution to increasing hardenability.
This is observable by reference to the chart identified
as Fig. 4, wherein the actual boron factor is plotted
in the vertical direction of the ordinate and the
20 carbon content of the steel is plotted in the horizontal -
direction of the abscissa. A target value or normal
expectancy value is represented in Fig. 4 by the substan-
tially straight shaded band or region identified by the
reference letter A. The further that the actual boron
factor is below the target value in the band when
viewing the chart, the more undesirable it is.
Initially, steels having a chemistry similar
to lOB30 Mod., 41B30, and lOB30 Mod. with high silicon
(0.5 - 0.65 Wt.~ were experimentally poured. It was
found that there was no apparent correlation between
the boron factor and the micro-alloying content, since
the 0.25-0.40 Wt.% Cr and 0.08-0.15 Wt.~ Mo in the
41B30 alloy steel didn't influence the boron factor.
Furnace or ladle additions of aluminum, with and without
additions of ferrotitanium and silicon zirconium, were
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made to the melt before pouring and various filled
tubular articles or rods were inserted into the casting
cavity at the time of pouring. For example, some rods
contained particulate ferrotitanium and/or silicon
zirconium along with particulate ferroboron. The
actual boron factors obtained varied from less than 1.0
to 2.07 and fluctuated too widely as may be noted by
reference to the zone designated by the reference
letter "B" in Fig. 4. From this and the chemical
analyses of the various heats the conclusions were
reached that furnace and ladle additions were erratic
and wasteful, and that ferrotitanium additions within
the rod were highly desirable. Furthermore, while
zirconium additions within the sheath exhibited some
degree of success on hardenability, the cost thereof
was excessive for the effectiveness obtained. It was
also learned that boron factors did not appear to
relate to boron content.
~ith this background, further experimental
tests were conducted using four different filled tubular
articles or rods for comparison purposes. These rods
were designated as Nos. 1-4 in the chart identified as
Fig. 5, and different quantities thereof were melted by
the following lOB38 carbon steel composition in percent-
age by weight as it was poured at a preselected pour
temperature into the casting cavity at an average pour
rate of about 11.3 Kg/sec (25 lbs/sec.):
C 0.35 - 0.43%
Mn About 1.13
S 0.050% Max.
P 0.040% Max.
Si 0.15 - 0.30%
Fe Balance
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Identical generally cylindrical ingots were produced and
tested for chemistry, oxygen and nitrogen levels,
hardenability and microstructure. From these data the
actual boron factors were obtained for each ingot heat.
The steel heats associated with rod Nos. 1
and 3 were prepared by ladle additions of a preselected
quantity of aluminum pellets generally in accordance
with conventional practices, while there was no aluminum
addition to the ladle during the pouring of the heats
of rod Nos. 2 and 4. Rather, in accordance with one
aspect of my invention, the aluminum wire 58 was incor-
porated within the ferrous metal conduit 56 of rod Nos.
2 and 4 and surrounded by the particulate master composi-
tion 60 including preselected proportions of ferroti-
tanium and ferroboron as indicated by Fig. 5. The totalweight percentage of the aluminum addition in each of
the various heats associated with rod Nos. 1 and 2 was
maintained the same, as was the aluminum addition in
the heats of rod Nos. 3 and 4. For continuity the
total weight percentage of the boron addition was kept
constant throughout this stage of the experimental
tests.
The results of the tests of rod Nos. 1 - 4
were enlightening. Particularly, it was noted that the
amount of aluminum present in the ingots associated
with rod Nos. 2 and 4 generally doubled in comparison
with the ingots associated with rod Nos. 1 and 3,
indicating that an unexpectedly high recovery rate was
exhibited. Since the average boron factor dropped from
30 about 1.8 to about 1.60 in comparable heats of rod Nos.
1 and 2, and the average boron factor dropped from
about 1.93 to about 1.61 in comparable heats of rod
Nos. 3 and 4, there was cause to believe that this was
due at least in part to the presence of excessive
amounts of aluminum and that the amount of aluminum and
1~L487~7
titanium needed within the rod could be reduced substan-
tially and still retain the desired level of harden-
ability. The extra titanium in the heats of rod No. 3
when compared with the heats of No. 1 caused a higher
boron factor, but not enough greater to justify the
added expense. Moreover, the amount of retained titanium
in some of the ingots was noted to be higher than
desired, for example above about 0.10 Wt.%.
Several heats using rod No. 5 were thereafter
run to take into account the above mentioned factors.
Rod No. 5 differed from the first four rods by containing
a preselected quantity of ferrovanadium. Boron factors
in the neighborhood of 1.90 were noted indicating a
definite success with that rod as a result of the
vanadium influence. However, the chemical analyses of
the ingots indicated that a relatively high residual
proportion of the additive elements was retained and
that the ratio of the elements within the rod was
therefor too rich.
Rod No. 6 was provided to reduce the amount
of aluminum and titanium substantially, while keeping
the amount of boron constant. Upon examining the
ingots thus produced it was found that the same high
boron factors of about 1.90 were observed. Thus,
unexpectedly good results were obtained with less
additive material, and this time the chemical analysis
of the ingots indicated only minimal amounts of the
additives present. This was the best rod of the seven
listed in Fig. 5.
Another rod, rod No. 7 was evaluated, and is
reported here to show that while columbium or niobium
is in the same general family as vanadium, the direct
substitution thereof for vanadium is not productive
insofar as hardenability is concerned. Specifically,
the boron factor dropped so much that such substitution
was indicated to be entirely unsatisfactory.
~148747
_ 17 _
The experience gained by analyzing the ingot
castings made by using rod Nos. 1-7 as discussed imme-
diately above permitted more extensive testing to be
conducted with a reasonable promise of success. Accord-
ingly, even though boron treated steel utilizing aminimum of additive material and having a reasonably
high boron factor had never been advanced to the desired
level in a continuous casting facility, three more
experimental tests were conducted using plain or low
carbon steel, medium carbon steel and medium carbon
alloy steel having some chromium and molybdenum therein
in the continuous casting facility described with
reference to Figs. 1 and 2.
Specifically, the filled tubular article 38
having the preferred No. 6 rod construction (28 parts
titanium; 1 part boron; 9 parts aluminum; and 24 parts
vanadium) was inserted into a plain carbon steel having
the following element analysis of primary interest in
pexcentage by weight:
C 0.17%
Mn 0.85%
Si 0.25%
S 0.022%
Al 0.008%
P 0.005~
The filled tubular article 38 was inserted into the
mold 20 as indicated in Fig. 2 at the rate of about 64
mm/sec. (212"/sec.), while the steel at about 1530C
(2790F) was poured into the mold at a rate of about
4.60 Kg/sec. (10.11 lbs./sec.). The filled tubular
article at almost 8 mm dia. (5/16" dia.) exhibited a
- dissolution depth "L" of about 400 mm (16"). This
corresponded to a rate of material addition of about
0.020 Wt.~ Al, 0.0023 Wt.% ~,0.063 Wt.% Ti and 0.055
Wt.~ V, reflected as a percentage of the molten metal
addition to the mold. This enabled withdrawal of the
1~879~7
cylindrical bar 50 at a diameter of about 150 mm (5.875")
at a rate of about 2m/min. (79"/min.~. The result was
the formation of an article having a highly desirable
actual boron factor of2.43, as indicated by the letter
"C" on the graph of Fig. 4. This was achieved with
reasonable levels of the additive ingredients remaining
in the article. For example, 0.027 Wt.% Al, 0.0011
Wt.% B, 0.04 Wt.% Ti, and 0.040 Wt.% V were noted in
the bar.
Secondly, the same filled tubular article 38
was inserted at approximately the same rate into a
medium carbon steel having the following element analysis
of primary interest in percentage by weight:
C 0.35%
Mn 0.82%
Si 0.29%
Cr 0.06%
S 0.023%
Al 0.008% (Est.)
P 0.008%
In this second instance the corresponding rate of material
addition was also about 0.020 Wt.% Al, 0.0023 Wt.% B, 0.063
Wt.% Ti, and 0.055 Wt.% V, and provided an article having a
boron factor of 2.03 as indicated by the letter "D" on the
graph of Fig. 4. This was achieved at a final chemistry
retention level of about 0.03 Wt.% Al, .0020 Wt.% B, 0.07
Wt.% Ti and 0.06 Wt.% V.
In the third instance, the same filled tubular
article 38 was inserted into a medium carbon alloy
steel having the following element analysis of primary
interest in percentage by weight:
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C 0.34%
~n 1.06%
Cr 0.30%
Si 0.25%
Mo 0.10%
S 0.020%
P 0.012%
Al 0.008% (Est.)
In the third case the corresponding rate of material
addition was reduced to about 0.015 Wt.% Al, 0.0016
Wt.% B, 0.045 Wt.% Ti, and 0.040 Wt.% V as reflected as
a portion of the molten metal addition to the mold.
The leaner mixture provided an excellent actual boron
factor of 2.16 as indicated by the Letter "E" on the
graph of Fig. 4 at a final chemistry retention level of
about 0.02 Wt.% Al, 0.0012 Wt.% B, 0.03 Wt.% Ti, and
0.035 Wt.% V.
Hence, it can be appreciated that the filled
tubular article and method for casting boron treated
steel in accordance with the present invention is
extremely successful by providing high boron factors,
by providing substantially the lowest practical levels
of material additions at a late stage to reduce fade
and contamination of the melt, and by providing a
manufactured article with relatively low chemistry
weight percentage levels of the additive elements. The
articles thus produced have exhibited an extremely
desirable clean microstructure morphology and/or a
minimum of nonmetallic inclusions that are often charac-
terized as "dirt". This is indicative that the recoveryrate is high, and the process economically efficient.
Other aspects, objects and advantages of this
invention can be obtained from a study of the drawings,
the disclosure and the appended claims.
."'.,
,:
