U.S. patent application number 11/092978 was filed with the patent office on 2005-10-06 for al-si based alloy and alloy member made therefrom.
Invention is credited to Fukuchi, Fumiaki, Yahaba, Takanori.
Application Number | 20050220660 11/092978 |
Document ID | / |
Family ID | 35054488 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050220660 |
Kind Code |
A1 |
Fukuchi, Fumiaki ; et
al. |
October 6, 2005 |
Al-Si based alloy and alloy member made therefrom
Abstract
An Al--Si based alloy and an alloy member made of the alloy, in
which when alloys produced by diecasting under high vacuum
conditions are welded, weldability can be improved without
increasing plate thickness of welded portions and reducing gas
content in diecasting.
Inventors: |
Fukuchi, Fumiaki; (Wako-shi,
JP) ; Yahaba, Takanori; (Wako-shi, JP) |
Correspondence
Address: |
ARENT FOX PLLC
1050 CONNECTICUT AVENUE, N.W.
SUITE 400
WASHINGTON
DC
20036
US
|
Family ID: |
35054488 |
Appl. No.: |
11/092978 |
Filed: |
March 30, 2005 |
Current U.S.
Class: |
420/534 |
Current CPC
Class: |
B22D 17/14 20130101;
C22C 21/02 20130101; B22D 17/00 20130101 |
Class at
Publication: |
420/534 |
International
Class: |
C22C 021/04 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2004 |
JP |
2004--101044 |
Claims
What is claimed is:
1. An Al--Si based alloy including Si at 7.5 to 9.0 mass %, Mg at
0.2 to 0.4 mass %, Mn at 0.3 to 0.5 mass %, Cu at 0.03 to 0.2 mass
%, Fe at 0.1 to 0.25 mass %, Sr at 0.005 to 0.02 mass %, and the
balance consisting of Al and inevitable impurities.
2. The Al--Si based alloy according to claim 1, wherein Si is 7.5
to 8.5 mass %, Mg is 0.2 to 0.3 mass %, and Mn is 0.3 to 0.4 mass
%.
3. An alloy member subject made of the Al--Si based alloy according
to claim 1 or 2.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an Al--Si based alloy and
to an alloy member made of the Al--Si based alloy, and in
particular, relates to a technique for producing an Al--Si based
alloy which is produced by diecasting under a high vacuum and has
good weldability.
[0003] 2. Related Art
[0004] Until now, various techniques have been disclosed as
production methods for casting by diecasting of aluminum. For
example, in order to improve mechanical properties, in particular,
elongation by aging only, without solution heat treatment, Japanese
Unexamined Patent Application Publication No. 7-91624 discloses a
production method of aluminum alloy casting including a step for
forming a casting by diecasting aluminum alloy, a step for coating
on the casting, and a step for heating which bakes the coating on
the coated casting and aging the casting at the same time, wherein
the aluminum alloy includes, by weight, Si at 7.5 to 9.5%, Cu at
0.1 to 0.3%, Mg at 0.1 to 0.32%, Fe at 0.5 to 0.9%, Mn at 0.2 to
0.6%, and Sr at 0.03 to 0.05%, and the balance consisting of Al. In
addition, in order to improve dimensional accuracy and toughness of
the diecasting products, Japanese Unexamined Patent Application
Publication No. 9-3610 discloses a production technique of aluminum
diecasting products including a step for diecasting aluminum molten
metal including Si at 5 to 13%, Mg at 0.5% or less, Mn at 0.1 to
1.0%, and Fe at 0.1 to 2.0%, a step of heating the diecasting
product to 400 to 500.degree. C., and a step for cooling to room
temperature at a cooling rate of 10.degree. C./sec or less, so that
average particle size of the diecasting product is 20 .mu.m or
less.
[0005] Of diecasting products produced by these disclosed
techniques, diecasting products using for example, 365 alloy
according to the AA standard, etc., has superior toughness, and
moreover, fluidity is superior because the products have uniform
alloy which exists in a region from the Al--Si hypo eutectic region
to the eutectic region. However, the products made of these alloys
do not exhibit superior weldability.
[0006] That is, in the case in which conventional Al--Si based
alloys obtained by diecasting are welded, welded metal flows out,
and sufficient weld bead dimensions such as throat thickness and
leg length are not obtained. Here, the above throat thickness and
leg length will be explained. FIG. 1 is a side view showing a
welding state of alloy members consisting of Al--Si based alloy. As
shown in the figure, the throat thickness is the largest height 2
in the protruding portion of weld metal 1 (shaded portion) which
exists in a welded portion, and the leg length is lengths 3 and 4
in each direction of the contact portion between the base metal
(each Al--Si based alloy) and weld metal 1. When the throat
thickness 2 is not ensured sufficiently, volume of the weld metal 1
is small, and when the leg lengths 3 and 4 are not ensured
sufficiently, contact area between the weld metal 1 and the base
metal is small. Therefore, in either case, strength of the welded
portion after welding is not sufficiently obtained.
[0007] In addition, in producing the conventional Al--Si based
alloys, superior quality and strength of the weld bead are not
obtained when Si content in the alloys is large, even if diecasting
is carried out under a vacuum so as to decrease gas content. The
reason for this is that hydrogen gas contained in diecasting
members bubble out and then a blowhole is formed in the weld bead
by generated and accumulated hydrogen gas bubble. For example, when
the Si content in the alloy is large, even if diecasting is carried
out under a vacuum so as to decrease the hydrogen content to 5.0
cc/100 g, crystallization of solid phase in welded portions is
delayed and bubbling of microbubbles of gas is thereby caused due
to dissolving, generating and accumulating of hydrogen gas. As a
result, a blowhole is formed in the weld bead and therefore,
superior strength and quality of the alloy, etc., are not obtained.
In view of such circumstances, in order to obtain sufficient
strength until now in the welded portion, it was necessary that
plate thickness of the welded portion zone be increased or that gas
content in diecasting be reduced.
DISCLOSURE OF INVENTION
[0008] The present invention was completed in view of the above
circumstances, and objects of the present invention are therefore
to provide an Al--Si based alloy and an alloy member made of the
alloy, in which when alloys produced by diecasting under high
vacuum conditions are welded, weldability can be improved without
increasing plate thickness of welded portions and gas content is
reduced in diecasting.
[0009] The present inventors researched Al--Si based alloys and
alloy members made of the alloy, which is produced by diecasting
under high vacuum conditions and exhibits superior weldability, as
described above. As a result, it was concluded that according to
the Al--Si based alloy, superior weld beads can be formed and
preferable weld strength, that is, sufficient weldability, can be
thereby obtained, by the following known facts shown in 1) to
4).
[0010] 1) FIG. 2 is a graph showing the relationship between the
liquid phase rate and temperature in welding in connection with
each Si content in an Al--Si based alloy. As shown in the figure,
in welded metal immediately after welding, the lower the Si
content, the higher the starting temperature of crystallization of
the solid phase, and the viscosity of the welded metal after
welding is increased with increasing of solid phase. Therefore, for
example, when the Si content in the Al--Si based alloy is
controlled to within 7.5 to 9.0 mass %, viscosity in melting can be
sufficiently ensured, and solidifying time of the weld bead can be
shortened by increasing the liquid temperature and the solid
temperature. As a result, throat thickness and leg length can be
sufficiently ensured by preventing flowing out of weld metal, and
bubbling of microbubbles of gas due to dissolving, generating and
accumulating of hydrogen gas is prevented by crystallization of
solid phase and blowhole in the weld bead can also thereby be
prevented from forming. Therefore, weldability can be improved.
[0011] 2) When Mu, Cr, Ti, and Sr are contained in a small amount
as a improvement processing agent, the alpha phase of aluminum in
solidifying the weld bead is made finer, the beta phase of Si is
fine-spheroidized, and therefore, strength of the welded portion
can be improved.
[0012] 3) When Mn, Cr, and Fe are contained in the Al--Si based
alloy, the alloy can be prevented from adhering to and burning in
the metal mold, even if molten metal temperature, casting speed,
and casting pressure are increased in order to compensate for
fluidity in diecasting.
[0013] 4) It is preferable that Ti not be contained as a
constituent element of the alloy in order to attempt to improve
toughness.
[0014] The present invention was completed in view of the above
knowledge.
[0015] That is, an Al--Si based alloy according to the present
invention includes Si at 7.5 to 9.0 mass %, Mg at 0.2 to 0.4 mass
%, Mn at 0.3 to 0.5 mass %, Cu at 0.03 to 0.2 mass %, Fe at 0.1 to
0.25 mass %, Sr at 0.005 to 0.02 mass %, and the balance consisting
of Al and inevitable impurities.
[0016] It is preferable that the Al--Si based alloy include Si at
7.5 to 8.5 mass %, Mg at 0.2 to 0.3 mass %, and Mn at 0.3 to 0.4
mass %.
[0017] As shown in the above, according to the present invention,
an Al--Si based alloy which exhibits superior weldability in
diecasting under high vacuum conditions can be obtained by
optimizing of contents of Si, Mg, Mn, Cu, Fe, and Sr which are
constituent elements in the alloy. In welding of alloy members
produced by using the alloy of the present invention, by improving
the weldability, plate thickness of welded portion in the alloy
members is decreased and length of weld bead is shortened, and the
alloy members obtained by diecasting can be thereby made lighter.
In addition, the alloy members of the present invention are
preferably employed as members for various processing since
toughness is high as that of conventional alloy members and
weldability is also high. Furthermore, welding processes can be
rationalized in welding of the alloy members of the present
invention, since plate thickness can be decreased as described
above, etc. Additionally, diecasting process can also be
rationalized since the contained gas amount in diecasting is
increased.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 is a side view showing a welding state of alloy
members consisting of an Al--Si based alloy.
[0019] FIG. 2 is a graph showing the relationship between the
liquid phase rate and temperature in welding in connection with
each Si content in the Al--Si based alloy.
[0020] FIGS. 3A to 3C are graphs showing mechanical properties in
the case in which molten metal of each Al--Si--Mg alloy in which Mg
content was set to a desired value and Si content was changed was
cast in a metal mold for an ASTM test piece by a 200-ton diecasting
machine, respectively, and then a test piece for tension test was
processed, and subsequently, a tension test was carried out without
heating. FIG. 3A shows tensile strength, FIG. 3B shows proof
stress, and FIG. 3C shows elongation.
[0021] FIGS. 4A to 4C are graphs showing mechanical properties in
the case in which molten metal of each Al--Si--Mg alloy in which Si
content was set to a desired value and Mg content was changed was
cast in a metal mold for an ASTM test piece by a 200-ton diecasting
machine, respectively, and then a test piece for tension test was
processed, and subsequently, a tension test was carried out without
heating. FIG. 4A shows tensile strength, FIG. 4B shows proof
stress, and FIG. 4C shows elongation.
[0022] FIG. 5 is a plane view showing a test piece for tension test
cut down from each plate-shaped diecasting product (Examples 1 to 5
and Comparative Examples 6 to 12 of the present invention).
[0023] FIG. 6 is a side view showing a point of welding and a point
of measurement of throat thickness and blowhole in the
Examples.
BEST MODE FOR CARRYING OUT THE INVENTION
[0024] In the following, reasons for the limitation of the contents
of each constituent element in the Al--Si based alloy according to
the present invention will be explained.
[0025] FIGS. 3A to 3C are graphs showing the relationships of
tensile strength, proof stress and elongation in the case in which
molten metal of each Al--Si--Mg alloy in which Mg content was set
to a desired value and Si content was changed was cast in a metal
mold for an ASTM test piece by a 200-ton diecasting machine,
respectively, then a test piece for tension test was processed, and
subsequently, a tension test was carried out without heating. As is
apparent from the results of FIG. 2 and FIGS. 3A and 3B, when the
Si content is 7.5 mass % or more, fluidity of molten metal in
diecasting is superior and mechanical properties such as tensile
strength, proof stress, etc., are thereby superior. In the
meantime, the following conclusions were obtained from the results
of FIG. 2 and FIG. 3C. That is, when the Si content is 9.0 mass %
or less, the solid phase in the welded portion after welding is
crystallized at a high temperature range and viscosity of the
welded portion after welding is increased with increase of the
solid phase, and the weld metal is prevented from flowing out. As a
result, throat thickness and leg length are sufficiently ensured,
bubbling of microbubbles of gas is prevented by the crystallization
of the solid phase, and formation of blowhole in weld bead is
prevented also. Therefore, toughness such as elongation can be
sufficiently ensured. As described above, the Si content is set to
be 7.5 to 9.0 mass %. Here, it is preferable that Si content be 8.5
mass % or less, since elongation can be ensured at a higher
level.
[0026] FIGS. 4A to 4C are graphs showing the relationships of
tensile strength, proof stress and elongation in the case in which
molten metal of each Al--Si--Mg alloy in which Si content was set
to a desired value and Mg content was changed was cast in a metal
mold for an ASTM test piece by a 200-ton diecasting machine,
respectively, then a test piece for tension test was processed, and
subsequently, tension test was carried out without heating. Mg is
contained in order to improve mechanical properties such as tensile
strength and proof stress, as well as Si. As is apparent from FIGS.
4A to 4C, when Mg content is less than 0.2 mass %, the improving
effect of the above mechanical properties is low. In contrast, when
the content exceeds 0.4 mass %, toughness such as elongation is
decreased. Therefore, the Mg content is set to be 0.2 to 0.4 mass
%. Here, it is preferable that Mg content be 0.3 mass % or less,
since elongation can be ensured at a higher level.
[0027] In the following, tensile strength, proof stress and
elongation in tensile test in the case of the above Si content and
Mg content will be explained in detail. That is, as is apparent
from FIG. 3A and FIG. 4A, the tensile strength is easily affected
by the Mg content more than the Si content. When the Si content is
9.0 mass % or 10.0 mass %, the tensile strength increases in
proportion to Mg content; however, when the Si content is less than
7.5 mass %, the tensile strength is rapidly lowered. In order to
maintain the tensile strength, it is preferable that the Si content
be 7.5 mass % or more and the Mg content be 0.2 mass % or more. In
addition, as is apparent from FIG. 3B and FIG. 4B, the proof stress
is also easily affected by the Mg content more than of the Si
content. When the Si content is 9.0 mass % or 10.0 mass %, superior
proof stress is exhibited; however, there is less difference of
tensile strength than that of proof stress between these contents
and there is less difference when the Si content is 7.5 mass % or
more. Furthermore, as is apparent from FIG. 3C and FIG. 4C, the
elongation is easily affected by not only the Mg content but also
the Si content. That is, the elongation tends to be in inverse
proportion to the Si content, and the less the Si content, the
larger the elongation. In addition, for elongation it is preferable
that the Mg content be within 0.2 to 0.4 mass %.
[0028] Next, Mn is contained in order to suppress that toughness
such as elongation is decreased by Fe compound which is a needle
coarse crystal deposited in diecasting. When the Mn content is less
than 0.3 mass %, the above effect in which decreasing of the
toughness is suppressed is poor. In contrast, when the content
exceeds 0.5 mass %, the above suppressing effect is saturated and
it is difficult to obtain further effect. Therefore, the Mn content
is set to be 0.3 to 0.5 mass %. Here, it is preferable that the Mn
content be 0.4 mass % or less, since intermetallic compound is
prevented from being produced and the elongation can be
sufficiently ensured.
[0029] In addition, Cu is contained in order to improve tensile
strength and proof stress. When Cu content is less than 0.03 mass
%, high purity Al mother alloy must be used in diecasting, and in
addition, the cleanliness of the fusion furnace and the holding
furnace must be more precisely controlled than those of
conventional methods, and producing cost is increased. In contrast,
when the content exceeds 0.2 mass %, by affecting the Si content,
toughness such as the elongation lowering and moreover, corrosion
resistance are deteriorated. Therefore, the Cu content is set to be
0.03 to 0.2 mass %.
[0030] Furthermore, Fe content is less than 0.1 mass %, high purity
Al mother alloy must be used in diecasting, and in addition, the
cleanliness of fusion furnace and holding furnace must be more
precisely controlled than those of conventional methods, and
producing cost is increased. In contrast, when the Fe content
exceeds 0.25 mass %, Fe compound is deposited as a needle coarse
crystal in diecasting, and toughness such as elongation is
decreased. Therefore, the Fe content is set to be 0.1 to 0.25 mass
%.
[0031] Additionally, Sr is contained in order to fine Si particles
deposited in diecasting. Since the Si content is 9.0 mass % or
less, when the Sr content is less than 0.005 mass %, the above
fining effect is not obtained. In contrast, when the Sr content
exceeds 0.02 mass %, the above fining effect is saturated and it is
difficult to obtain further effects, and consequently, yield is
deteriorated. Therefore, the Sr content is set to be 0.005 to 0.02
mass %.
EXAMPLES
[0032] In the following, the present invention will be explained in
more detail by Examples.
[0033] Alloys having the compositions shown in Table 1 were
dissolved at 720.degree. C., respectively and then were deoxidized
and degassed by molten metal treatment using Ar gas and flux. Next,
under a vacuum condition at an internal pressure of a metal mold of
5 kPa and at molten metal temperature 700.degree. C., the alloys
were cast using a metal mold for plate-shaped diecasting having
width of 100 mm, depth of 300 mm, and height of 5 mm, and
plate-shaped diecasting products having each composition shown in
Table 1 (Examples 1 to 5 and Comparative Examples 6 to 12 of the
present invention) were thereby obtained. Here, temperature of the
metal mold was 150.degree. C. Subsequently, the above diecasting
products were subjected to each heat treatment which was
respectively suitable under the condition described in Table 1.
1TABLE 1 units: mass % Heating Condition Si Fe Cu Mn Mg Zn Ti Sr
(only Aging) Example 1 7.5 0.13 0.14 0.46 0.25 0.016 200.degree.
C., 2 hours Example 2 8 0.19 0.14 0.36 0.23 0.017 200.degree. C., 2
hours Example 3 8.2 0.19 0.14 0.36 0.23 0.017 200.degree. C., 2
hours Example 4 8.6 0.17 0.13 0.49 0.23 0.015 200.degree. C., 2
hours Example 5 9 0.14 0.15 0.35 0.24 0.015 200.degree. C., 2 hours
Comparative 7 0.14 0.15 0.41 0.24 0.012 200.degree. C., 2 hours
Example 6 Comparative 8.5 0.33 0.22 0.3 0.4 0.011 200.degree. C., 2
hours Example 7 Comparative 9.5 0.16 0.16 0.5 0.3 0.013 180.degree.
C., 3 hours Example 8 Comparative 10 0.14 0.13 0.46 0.21 0.014
180.degree. C., 3 hours Example 9 Comparative 10.5 0.07 0.01 0.62
0.26 0.07 0.06 0.018 180.degree. C., 3 hours Example 10 Comparative
10.3 0.08 0.01 0.65 0.35 0.06 0.02 180.degree. C., 3 hours Example
11 Comparative 10.1 0.07 0.01 0.62 0.2 0.06 0.18 180.degree. C., 3
hours Example 12
[0034] Next, in connection with the plate-shaped diecasting
products (Examples 1 to 5 and Comparative Examples 6 to 12 of the
present invention), test pieces for a tensile test having sizes
shown in FIG. 5 were cut out from the center of the product, and
test pieces (plate thickness of 2.5 mm with U-shaped notch) for a
Charpy impact test shown in JIS Z2242 were cut out. The test pieces
were subjected to normal temperature tensile test using a 5-ton
tensile testing machine and a Charpy impact test using a 5-kg-m
Charpy impact testing machine. These results are shown in Table
2.
2 TABLE 2 Tensile Charpy Strength Proof Stress Value MPa MPa
Elongation % J/cm.sup.2 Example 1 278 188 11.4 10.7 Example 2 284
190 10.3 9.3 Example 3 286 191 10.3 9.5 Example 4 289 192 10.3 8.9
Example 5 293 193 10 8.1 Comparative 236 164 10.9 9.3 Example 6
Comparative 297 210 4.9 1.9 Example 7 Comparative 301 197 8.5 7.1
Example 8 Comparative 283 196 7.6 5.9 Example 9 Comparative 292 189
7.7 5.6 Example 10 Comparative 310 201 5.8 3.4 Example 11
Comparative 235 165 9.2 8.2 Example 12
[0035] As is apparent from Table 2, each diecasting product of
Examples 1 to 5 exhibited superior results about not only tensile
strength, proof stress and elongation but also impact value to
those of each diecasting product of Comparative Examples 6 to
12.
[0036] Furthermore, each diecasting product was subjected to an
evaluation about weldability. The welding was carried out according
to the model figure shown in FIG. 6. In FIG. 6, numeral reference B
showed total throat thickness (minimum thickness in building up
portion by overlaying), and numeral reference Bb showed blowhole
thickness. In addition, as described in the same figure, each
diecasting product of Examples 1 to 5 and Comparative Examples 6 to
12 was used for a top plate, and T1 thickness of the plate was 4
mm. On the other hand, A5052P-O product was used for a bottom
plate, and T2 thickness of the plate was 3 mm. Under such
conditions, overlapping plates were assembled by fillet welding,
MIG welding was carried out at a contact pressure of 3 tons,
current of 230 A and voltage of 23 V, using filler metal A5356, and
strip-shaped test pieces having width of 25 mm were cut out from
the center of weld bead. The test pieces were subjected to normal
temperature tensile test using a 5-ton tensile testing machine, and
weld strength in the time was measured. The results are shown in
Table 3. Here, alloys of Comparative Examples 10 to 12 were
equivalent to 365 alloy of the AA standard. In the following, the
results of each diecasting product are shown in the both cases in
which diecasting contained gas amount was 2 cc/100 g and in which
the gas amount was 8 cc/100 g.
3 TABLE 3 Throat Thickness mm Welding Strength N Contained Gas
Contained Gas Amount Contained Contained Amount 2 cc/100 g 8 cc/100
g Gas Gas Total Blowhole Total Blowhole Amount Amount Throat
Thickness Throat Thickness 2 cc/100 g 8 cc/100 g Thickness B Bb
Thickness B Bb Example 1 8779 8631 3.9 0 4.0 0.8 Example 2 9075
8898 4.2 0 4.2 0.9 Example 3 9114 8967 4.3 0 4.4 0.9 Example 4 9227
9103 4.4 0 4.5 0.9 Example 5 9364 9182 4.4 0 4.4 1.0 Comparative
7529 7442 3.9 0 3.9 0.9 Example 6 Comparative 9472 9315 4.3 0 4.3
1.2 Example 7 Comparative 8134 7646 3.7 0.1 3.9 1.7 Example 8
Comparative 7193 6759 3.2 0.3 3.7 1.7 Example 9 Comparative 7340
6826 3.3 0.2 3.8 1.9 Example 10 Comparative 7396 7026 3.3 0.2 3.7
1.8 Example 11 Comparative 6125 5728 3.2 0.3 3.9 1.9 Example 12
[0037] According to in Table 3, the results in the case in which
diecasting products of Examples 1 to 5 were used, were generally
superior to those in the case in which diecasting products of
Comparative Examples 6 to 12 were used. This applied to not only
when diecasting contained gas amount was 2 cc/100 g but also when
it was 8 cc/100 g. Here, the results in the case in which
diecasting contained gas amount was 2 cc/100 g, were generally
superior to those in the case in which diecasting contained gas
amount was 8 cc/100 g.
[0038] In addition, cross section of the bead portion of welding
remaining material which adjoined the overlapped fillet welding
test piece was water-polished by abrasive paper and was
diamond-polished, and subsequently, the cross section of weld bead
was observed. Specifically, throat thickness B (mm) and blowhole
thickness Bb (mm) in the case in which the contained gas amount
were different (2 cc/100 g and 8 cc/100 g) were measured at
positions shown in FIG. 6. The results are shown in Table 3.
[0039] As is apparent from Table 3, in the weld bead using the
diecasting products of Examples 1 to 5, superior weldability was
exhibited because throat thickness was larger and blowhole
thickness was smaller than those in the case in the weld bead using
the diecasting products of Comparative Examples 6 to 12.
Additionally, in the case in which the contained gas amount was 2
cc/100 g, if the diecasting products of Examples 1 to 5 were used,
blowholes did not form and stabilized weldability was obtained.
[0040] In Si--Al based alloy of the present invention, in the case
in which diecasting is carried out under high vacuum condition,
weldability can be improved without increasing plate thickness of
welding portion or reducing contained gas amount in diecasting.
Therefore, the present invention is preferable to use as a various
member in which more superior weldability will be required in the
future.
* * * * *