U.S. patent application number 12/458514 was filed with the patent office on 2010-01-07 for low-density high-toughness alloy and the fabrication method thereof.
Invention is credited to Jian-Wei Lee, Tzeng-Feng Liu.
Application Number | 20100003159 12/458514 |
Document ID | / |
Family ID | 41464537 |
Filed Date | 2010-01-07 |
United States Patent
Application |
20100003159 |
Kind Code |
A1 |
Liu; Tzeng-Feng ; et
al. |
January 7, 2010 |
Low-density high-toughness alloy and the fabrication method
thereof
Abstract
The present invention discloses a low-density high-toughness
alloy and the fabrication method thereof. The alloy of the present
invention consists essentially of: by weight percent, equal to or
greater than 23% but lower than or equal to 33% manganese, equal to
or greater than 8.1% but lower than or equal to 9.8% aluminum,
equal to or greater than 3% but lower than or equal to 5.0%
chromium, equal to or greater than 0.6% but lower than or equal to
1.2% carbon, equal to or greater than 0.1% but lower than or equal
to 0.24% silicon and the balance of iron. The golf-club head made
from the abovementioned alloy can obtain superior elongation,
strength, damping capacity, and corrosion resistance even without
any heat treatment, or any hot/cold working, such as forging and
rolling; therefore, the fabrication cost thereof can be obviously
reduced.
Inventors: |
Liu; Tzeng-Feng; (Hsinchu,
TW) ; Lee; Jian-Wei; (Hsinchu City, TW) |
Correspondence
Address: |
ROSENBERG, KLEIN & LEE
3458 ELLICOTT CENTER DRIVE-SUITE 101
ELLICOTT CITY
MD
21043
US
|
Family ID: |
41464537 |
Appl. No.: |
12/458514 |
Filed: |
July 15, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11509771 |
Aug 25, 2006 |
|
|
|
12458514 |
|
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|
Current U.S.
Class: |
420/74 ; 148/540;
164/113; 164/61; 164/68.1; 420/583 |
Current CPC
Class: |
C21D 6/002 20130101;
C22C 38/06 20130101; C21D 8/02 20130101; C22C 38/02 20130101; C21D
6/005 20130101; C21D 2211/004 20130101; C22C 38/38 20130101; C21D
6/02 20130101 |
Class at
Publication: |
420/74 ; 420/583;
164/113; 148/540; 164/61; 164/68.1 |
International
Class: |
C22C 38/38 20060101
C22C038/38; C22C 30/00 20060101 C22C030/00; B22D 17/02 20060101
B22D017/02; C21D 1/00 20060101 C21D001/00; B22D 23/00 20060101
B22D023/00; B22D 27/00 20060101 B22D027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 14, 2005 |
TW |
94135943 |
Claims
1. A low-density high-toughness alloy, comprising: equal to or
greater than 23 wt. % but lower than or equal to 33 wt. %
manganese, equal to or greater than 8.1 wt. % but lower than or
equal to 9.8 wt. % aluminum, equal to or greater than 3 wt. % but
lower than or equal to 5.0 wt. % chromium, equal to or greater than
0.6 wt. % but lower than or equal to 1.2 wt. % carbon, equal to or
greater than 0.1 wt. % but lower than or equal to 0.24 wt. %
silicon, and the balance of iron.
2. The low-density high-toughness alloy according to claim 1,
further comprising up to 1.5 wt. % molybdenum.
3. The low-density high-toughness alloy according to claim 1,
having a density ranging from 6.6 to 6.9 g/cm.sup.3, an elongation
ranging from 30 to 60%, and a tensile strength ranging from 100 to
135 ksi.
4. A fabrication method of a low-density high-toughness alloy,
comprising melting a raw material, which comprises: equal to or
greater than 23 wt. % but lower than or equal to 33 wt. %
manganese, equal to or greater than 8.1 wt. % but lower than or
equal to 9.8 wt. % aluminum, equal to or greater than 3 wt. % but
lower than or equal to 5.0 wt. % chromium, equal to or greater than
0.6 wt. % but lower than or equal to 1.2 wt. % carbon, equal to or
greater than 0.1 wt. % but lower than or equal to 0.24 wt. %
silicon, and the balance of iron; pouring said raw material into
shell molds having spiral runner and pre-heated; and de-casting
said raw material from said shell molds.
5. The fabrication method of a low-density high-toughness alloy
according to claim 4, wherein said raw material further comprises
up to 1.5 wt. % molybdenum.
6. The fabrication method of a low-density high-toughness alloy
according to claim 4, further comprising a step of heat-treating
said alloy at the temperature ranging from 950 to 1200.degree. C.
for the duration ranging from 1 to 3 hours.
7. The fabrication method of a low-density high-toughness alloy
according to claim 4, wherein said raw material is melted at the
atmosphere, at vacuum, or at a reducing atmosphere.
8. The fabrication method of a low-density high-toughness alloy
according to claim 4, wherein said alloy has a density ranging from
6.6 to 6.9 g/cm.sup.3, an elongation ranging from 30 to 60%, and a
tensile strength ranging from 100 to 135 ksi.
Description
[0001] The present application is a continuation in part of U.S.
application Ser. No. 11/509,771 titled "LOW-DENSITY HIGH-TOUGHNESS
ALLOY AND THE FABRICATION METHOD THEREOF," filed Aug. 25, 2006 and
presently pending.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a low-density alloy,
particularly to a low-density alloy for use of making golf-club
heads with superior elongation, strength, damping capacity, and
corrosion resistance generated without any heat treatment and
plastic deformation process, including hot working, and cold
working.
[0004] 2. Description of the Related Art
[0005] To provide a better ball-hitting feeling for the golfers,
and to enable the golfer to hit the ball farther and more stably
(i.e. longer ball-contacting time, higher ball-controlling ability,
and lower vibration), many commercial materials have been applied
to golf-club heads, such as 8620 soft iron, 304 austenitic
stainless steel, 17-4PH precipitation-hardening stainless steel,
AISI431/AISI455 high-strength martensitic stainless steel,
18Ni(200) maraging steel, Ti-6Al-4V alloy, and SP-700 titanium
alloy. Among those materials, some have superior ductility, but the
strength thereof is pretty insufficient; for example, 8620 soft
iron and 304 austenitic stainless steel have an elongation as high
as about 50% but have a tensile strength of only about 80 ksi. Some
have very high strength, but the ductility thereof is pretty low;
for example, AISI431/AISI455 high-strength martensitic stainless
steel and 18Ni(200) maraging steel have a tensile strength as high
as 150.about.200 ksi but have an elongation of only 10% or below.
According to the current design principles of golf-club heads, the
ideal material for the golf-club head should have the following
characteristics: (1) low density: under the requirement that the
golf-club heads of a specified number should be equal to a
specified weight, the golf-club head using a low-density material
can have a larger volume; therefore, the ball-striking sweet zone
can be enlarged, and the probability of utilizing the correct
region to hit the ball increases; further, the low density
golf-club head material can also increase the design flexibility of
the balance weight, lower the gravitational center of the golf-club
head, and then increase the stability and the swing force of the
ball-striking actions, so that balls can be hit farther and more
accurately; (2) appropriate combination of ductility and strength:
the loft angle between the shaft and the striking face may be
adjusted according to the height of the golfer; the higher the
ductility of the golf-club head material, the larger the allowable
range of adjusting the loft angle; further, the higher the
ductility, the longer the time that the golf ball contacts the
striking face, and thus, the flying trajectory of the golf ball can
be more easily controlled, and the ball-controlling ability is
promoted; (3) high damping ratio: the material of high damping
capacity can absorb the vibration created by hitting a ball, so
that the vibration is less likely to numb the hands of the golfer,
and the golfer can have a better ball-hitting feeling and can
control the golf ball more steadily; (4) high elastic modulus
(Young's modulus): the higher the elastic modulus, the longer the
flight distance of the golf ball; (5) high corrosion resistance:
high corrosion resistance makes the golf-club head less likely to
rust when it is used in humidified and herbicide-containing lawn;
thus, the function and appearance of the golf-club head can be
maintained, and the design flexibility of golf-club heads can also
be promoted.
[0006] Therefore, a Fe--Mn--Al--C-based low-density high-toughness
alloy has come to the attention of the golf world. The development
history of the Fe--Mn--Al--Cr--C alloy and its applications to
golf-club heads will be described below.
[0007] In the Age of Cold War, nickel and chromium are resources of
high strategic and economical value; however, the conventional
Ni--Cr-based stainless steel comprises high proportion of Ni and
Cr; furthermore, the chromium and nickel mines are not common in
the Western World but rich in the Republic of Zimbabwe and the
Republic of South Africa. Owing to strategic and economical
considerations, researchers began to develop Ni/Cr-free stainless
steel and tried to replace Cr and Ni with Mn and Al; therefore, the
Fe--Mn--Al alloy was developed then. It is found: since the
Fe--Mn--Al alloy has a protective high-temperature-durable
aluminum-oxide layer formed on the surface, the Fe--Mn--Al alloy
has better oxidation resistance at high temperature than the
traditional stainless steel, and the weight gain of the Fe--Mn--Al
alloy is also much less than that of the conventional stainless
steel; however, in the environment of sea water or corrosive
liquid, the corrosion-resistance of the Fe--Mn--Al alloy is
inferior to that of the conventional stainless steel.
[0008] Excluding the case that the Fe--Mn--Al alloy is used as a
substitute for stainless steel, a series of Fe--Mn--Al--C-based
high-strength and high-ductility alloys has been developed by many
specialists and scholars for the last two decades.
[0009] From surveying the abovementioned papers, it is found: after
the processes of a plastic working (such as forging and rolling), a
solid-solution heat treatment at the temperature of
950.about.1200.degree. C., a fast quenching, and then an aging heat
treatment at the temperature of 450.about.75.degree. C., the
Fe-(28.about.35) wt. % Mn-(4.9.about.11) wt. % Al-(0.5.about.2.0)
wt. % C-based alloy becomes a high-strength and high-ductility
alloy having an austenitic-matrix structure, a density of
6.6.about.6.8 g/cm.sup.3, a tensile strength of 100.about.180 ksi,
a yield strength of 90.about.160 ksi, and an elongation of
25.about.65%.
[0010] In order to improve the corrosion resistance, 2.98.about.6
wt. % of Cr and 0.9.about.1.03 wt. % of Mo may be further added
into the above-mentioned Fe--Mn--Al--C-based alloy; the corrosion
resistance thereof has been discussed in detailed in the following
papers. [0011] 1. Jeng-Gong Duh, et al., "Diffusion-Related
Kinetics in the Oxidation-Induced Phase Transformation of
Fe-9Al-3Cr-31Mn Alloys", J. Electronchem. Soc., Vol. 136, No. 3,
March 1989 [0012] 2. Jeng-Gong Duh, et al., "Microstructural
development in the oxidation-induced phase transformation of
Fe--Al--Cr--Mn--C alloys", JOURNAL OF MATERIALS SCIENCE, Vol. 23,
1988 [0013] 3. J. G. Duh, et al., "Nitriding behavior in
Fe--Al--Mn--Cr--C alloys at 1000-1100.degree. C.", JOURNAL OF
MATERIALS SCIENCE, Vol. 28, 1993 [0014] 4. S. C. Chang, et al.,
"Environment-Assisted Cracking of Fe-32% Mn-9% Al Alloys in 3.5%
Sodium Chloride Solution", J. CORROSION, Vol. 51, 1995 [0015] 5. J.
G. Duh, et al., "Nitriding Kinetics of Fe--Al--Mn--Cr--C alloys at
1000.degree. C.", JOURNAL OF MATERIALS SCIENCE, Vol. 25, 1990
[0016] 6. J. G. Duh, et al., "High temperature oxidation of
Fe-31Mn-9Al-xCr-0.87C alloys (x=0, 3 and 6)", JOURNAL OF MATERIALS
SCIENCE, Vol. 25, 1990 [0017] 7. M. S. thesis "Phase
Transformations in an Fe-8.8Al-30.0Mn-6.0Cr-1.0C Alloy", National
Chiao Tung University, 1990, supervised by Prof. Liu Tzeng-Feng
(one of the inventors of the present invention)
[0018] From those discussed above, it is known: via appropriate
composition design, the Fe--Mn--Al--C alloy, which has low density,
high strength, and high toughness, is a material pretty fitting for
golf-club heads; therefore, the patent Fe--Mn--Al--C alloys of
different compositions have been tried to apply to golf-club heads.
In order to demonstrate the difference among them, the published US
and Taiwan patents relating to the applications of the
Fe--Mn--Al--C alloys to golf-club heads are to be described
below.
[0019] According to the Taiwan patent of Publication No. 178648
"Fabrication Method of the Precision Castings of a Fe--Mn--Al
Alloy", the claim 1 thereof claims a Fe--Mn--Al alloy consisting of
22.about.36 wt. % Mn, 6.about.8 wt. % Al, 1.5.about.2.0 wt. % C,
1.0.about.1.5 wt. % Mo, and the balance of Fe, which has to use a
solid-solution heat treatment at 1030.about.1050.degree. C. for
1.about.2 hours and an aging heat treatment at
450.about.550.degree. C. for 1.about.2 hours to obtain required
toughness and strength.
[0020] According to the Taiwan patent of Publication No. 185568
"Fabrication Method of the Precision Castings of a
Corrosion-Resistant Alloy", the claim 1 thereof claims a
fabrication method of the precision castings of a
corrosion-resistant alloy, wherein the casting of an alloy, which
consists of 26.about.28 wt. % Mn, 6.5.about.8 wt. % Al,
5.0.about.6.0 wt. % Cr, 0.9.about.1.1 wt. % C, 0.2.about.1.5 wt. %
Si, 1.0.about.1.2 wt. % Mo, 0.9.about.1.1 wt. % Cu, 0.02.about.0.04
wt. % Nb and the balance of Fe, requires a homogenization heat
treatment at an atmosphere furnace, an atmosphere-controlled
furnace, or a vacuum furnace.
[0021] According to the US patent of Publication No. 20030077479
"Low Density and High Ductility Alloy Steel for a Golf Club Head"
(equivalent to the Taiwan patent of Publication No. 460591), the
claim 1 thereof claims a low-density high-ductility iron-based
alloy for golf-club iron heads consisting of 25.about.31 wt. % Mn,
6.3.about.7.8 wt. % Al, 5.5.about.9.0 wt. % Cr, 0.65.about.0.85 wt.
% C, and the balance of Fe, which is hot forged at the temperature
of 800.about.1050.degree. C. The claim 2 thereof claims the alloy
according to claim 1 but further comprising: 0.8.about.1.5 wt. % Si
and 2.0.about.5 wt. % Ti. The claim 3 thereof claims the alloy
according to claim 1 but further comprise: 0.5.about.1 wt. % Mo.
Furthermore, in the patent specification thereof, the abstract, the
summary of the invention, and the Remarks in FIG. 8 also mention
that the alloy of this patent has to utilize a hot forging at the
temperature of 800.about.1050.degree. C. and a heat treatment at
the temperature of 980.about.1080.degree. C. for 1.about.24 hours
to obtain a superior combination of ductility and tensile
strength.
[0022] According to the US patent of Publication No. 20030082067
"Low-Density Iron Based Alloy for a Golf Club Head" (equivalent to
the Taiwan patent of Publication No. 506845), the claim 1 thereof
claims a low-density iron-based material for golf-club heads
consisting of 28.0.about.31.5 wt. % Mn, 7.8.about.10.0 wt. % Al,
0.9.about.1.10 wt. % C, 0.35.about.2.5 wt. % Ti, and the balance of
Fe, which is hot forged at the temperature of
900.about.1100.degree. C. The claim 2 thereof claims the alloy
according to claim 1 but further includes: 5.0.about.7.0 wt. % Cr.
The claim 3 thereof claims the alloy according to claim 1 but
further includes: 0.8.about.1.5 wt. % Si. Furthermore, in the
patent specification thereof, the abstract, the summary of the
invention, and the Remarks in FIG. 6 also mention: after the alloy
of this patent is heat-treated at the temperature of
950.about.1270.degree. C. for 1.about.24 hours, it can obtain a
microstructure which consists of an austenitic matrix and varying
ratios of precipitated phase (Ti, Fe)C.sub.x, and a density lower
than 6.6 g/cm.sup.3.
[0023] According to the US patent of Publication No. 20050006007
"Low Density Iron Based Alloy for a Golf Club Head" (equivalent to
the Taiwan patent of Publication No. 584568, the claim 1 thereof
claims a low-density iron-based alloy for golf-club heads
consisting of 25.about.31 wt. % Mn, 71.about.10 wt. % Al, 5.about.7
wt. % Cr, 0.9.about.1.1 wt. % C, and the balance of Fe. The claim 2
thereof claims the alloy according to claim 1 but further includes:
0.8.about.1.5 wt. % Si. The claim 3 thereof claims the alloy
according to claim 1 but further includes: 2.about.5 wt. % Cr. The
claim 4 thereof claims the alloy according to claim 1 but further
includes: 0.5.about.1.0 wt. % Mo. The claim 5 thereof claims the
low density iron based alloy as claimed in claim 1 is hot forged at
800 to 1050.degree. C. and has a surface roughness of 2.4 to 3
.mu.m. Furthermore, in the patent specification thereof, the
Chinese abstract, the summary of the invention, and the Notes of
FIG. 6 in Detailed description of the invention also mention: the
casting or the alloy having been plastically worked (hot worked or
cold worked) are heat-treated at the temperature of
950.about.1270.degree. C. for 1.about.24 hours to obtain a density
lower than 6.6 g/cm.sup.3 and a microstructure with different
ratios of precipitated phase; the alloy may also be hot forged at
the temperature of 800.about.1050.degree. C. to obtain a superior
surface property; the alloy may also be heat-treated at the
temperature of 980.about.1080.degree. C. for 14 hours and then
heat-treated at the temperature of 500.about.650.degree. C. for
4.about.8 hours, and the heat-treated alloy is cold rolled to
modify the structure of the crystalline grains and then
aging-treated to obtain a superior combination of tensile strength
and ductility to meet the requirement of the golf-club head--low
density, high strength and high corrosion resistance.
[0024] According to the Taiwan patent of Publication No. 1235677
"Low Density and High Ductility Iron Based Alloy for a Golf-Club
Head", the claim 1 thereof claims a low-density high-ductility
iron-based alloy for golf-club heads consisting of 23.0.about.30.0
wt. % Mn, 6.3.about.10.0 wt. % Al, 5.0.about.9.0 wt. % Cr,
0.8.about.1.05 wt. % C, 0.2.about.10.0 wt. % Co and the balance of
Fe, and the alloy is hot forged at the temperature of
1000.about.1050.degree. C. to promote surface property so that the
surface roughness will be below 3 .mu.m. The claim 2 thereof claims
the alloy according to claim 1 but further includes: 0.6.about.1.0
wt. % Si and 0.2.about.0.4 wt. % N. Furthermore, in the patent
specification thereof, the Chinese abstract, the summary of the
invention, the detailed description of the invention also mention:
the casting of the Co-containing alloy of the invention is hot
forged at the temperature of 1000.about.1050.degree. C. and then
heat-treated at the temperature of 1030.about.1080.degree. C. for
15.about.60 minutes and then heat-treated at the temperature of
450.about.850.degree. C. for 4.about.24 hours to obtain low
density, high strength, high ductility, high corrosion resistance,
and superior surface property and meet the requirement of the
golf-club head.
[0025] Refer to Table to survey the abovementioned US and Taiwan
patents regarding the application of the Fe--Mn--Al--C alloys to
golf-club heads, it is found: the published patents of the
Fe--Mn--Al--C alloys have to utilize a high-temperature long-time
solution heat treatment and an aging heat treatment, or a
hot-forging/rolling for grain-refining plus a long-time solution
heat treatment and an aging heat treatment to obtain the strength
and ductility required by golf-club heads. Further, as all the
conventional Fe--Mn--Al--C alloys have high carbon contents, the
golf-club heads made from those Fe--Mn--Al--C alloys must be
heat-treated in a vacuum furnace to prevent serious
decarburization; the forging molds, This leads to a great increase
in the fabrication cost of golf-club head.
[0026] Table shows the comparison of the disclosed Fe--Mn--Al-based
alloys in the prior arts, with respect to the compositions and the
heat treatment/forging conditions thereof as following:
TABLE-US-00001 Application Composition Forging and Heat-treatment
Pub. No. Fe Mn Al Cr C Si Mo others Conditions TW 178648 Bal. 22~36
6~8 1.5~2.0 1.0~1.5 solid solution at 1030~1050.degree. C. for 1~2
hrs and aging at 400~550.degree. C. for 1~2 hrs TW 185568 Bal.
26~28 6.5~8 5~6 0.9~1.1 0.2~1.5 1.0~1.2 0.9~1.1 Cu homogenization
heat treatment 0.02~0.04 Nb US 20030077479 Bal. 25~31 6.3~7.8 5.5~9
0.65~0.85 *0.8~1.5 *2~5 Ti hot forging at 850~1050.degree. C. and
heat treatment at 980~1080.degree. C. for 1~24 hrs US 20030082067
Bal. 28~31.5 7.8~10 *5~7 0.9~1.1 *0.8~1.5 0.35~2.5 Ti hot forging
at 900~1100.degree. C. and heat treatment at 950~1270.degree. C.
for 1~24 hrs US 20050006007 Bal. 25~31 7~10 5~7 0.9~1.1 *0.8~1.5
*0.5~1.0 hot forging at 850~1050.degree. C. and then solid solution
at 980~1080.degree. C. for 1~4 hrs and aging at 500~650.degree. C.
for 4~8 hrs TW 1235677 Bal. 23~30 6.3~10 5~9 0.8~1.05 *0.6~1.0
0.2~10 Co solid solution at 1030~1080.degree. C. for *0.2~0.4 N
15~60 mins and aging at 450~850.degree. C. for 4~24 hrs *means
content of element optionally added in this alloy
[0027] In the phase diagram of the Fe--Mn--Al--C alloy, there is a
wide temperature range in the solid-liquid mixing region, i.e. a
mush zone, wherein liquid-state metal and solid-state metal
coexists. As the coexisting liquid-state metal and solid-state
metal are very glutinous, the fluidity of the liquid alloy is poor,
and the tiny letters of the logo, the minute U/V-section trenches
of the striking face, and the thin-thickness region of the
golf-club head are hard to form in the casting process but are
mechanically carved otherwise; therefore, the fabrication time and
cost of the golf-club head increases greatly, and the appearance
design thereof is also limited by the poor castability in the
thin-thickness region. Further, owing to the poor fluidity of the
liquid alloy, the interdendrite porosity caused by the physical
shrinkage during solidification cannot be fed, which results in the
internal shrinkage porosity of the golf-club head and then the
deformation or fracture of the striking face may be occurred when
the golfer is hitting golf balls. Furthermore, the shrinkage
porosity will be originators of fractures when the golf-club head
is bent to adjust the loft angle between the head and the shaft or
when the casting is forged.
[0028] Accordingly, the present invention proposes a low-density
high-toughness alloy and the fabrication method thereof, which is
adaptable to be a golf-club head material and can save the time and
cost of fabricating the Fe--Mn--Al--C golf-club heads, to overcome
the abovementioned problems.
SUMMARY OF THE INVENTION
[0029] The present invention is to provide a low-density
high-toughness alloy and the fabrication method thereof by de-waxed
casting process, wherein the alloy of the present invention can
obtain superior elongation, strength, damping capacity, and
corrosion resistance without any heat treatment, hot working, or
plastic cold working.
[0030] Another one of objectives of the present invention is to
provide a low-density high-toughness alloy and the fabrication
method thereof, wherein the fluidity of the liquid alloy is
improved, and the castability and the plastic workability of the
alloy, such as forgeability and ductility, are also promoted.
[0031] Yet another one of objectives of the present invention is to
provide a low-density high-toughness alloy and the fabrication
method thereof, wherein the fluidity of liquid alloy is improved,
and the tiny letters, the trenches on the striking face, and
thin-thickness regions of the golf-club head can be formed merely
by only casting and without extra mechanical carving, and thereby,
the fabrication cost and time thereof can be greatly saved.
[0032] Still another one of objectives of the present invention is
to provide a low-density high-toughness alloy and the fabrication
method thereof, wherein the fluidity of the liquid alloy is
increased, and the interdendrite shrinkage porosity formed during
the solidification process can be easily fed by the liquid alloy,
which can solve the problem that the strength and ductility of the
golf-club head is drastically lowered owing to the internal
shrinkage porosity, and the problem that cracks are induced by the
shrinkage porosity during the forging process or the rolling
process; thereby, the yield thereof is greatly promoted.
[0033] Further another one of objectives of the present invention
is to provide a low-density high-toughness alloy and the
fabrication method thereof, wherein the alloy of the present
invention not only has a density as low as 6.6.about.6.9
g/cm.sup.3, but also can even obtain a superior elongation as high
as 30.about.60%, a superior tensile strength as high as
100.about.135 ksi, superior damping capacity, and superior
corrosion resistance without any heat treatment, hot working, or
plastic cold working in comparison with the conventional
Fe--Mn--Al--C alloys.
[0034] The present invention proposes a low-density high-toughness
alloy, comprising: equal to or greater than 23 wt. % but lower than
or equal to 33 wt. % manganese, equal to or greater than 8.1 wt. %
but lower than or equal to 9.8 wt. % aluminum, equal to or greater
than 3 wt. % but lower than or equal to 7.8 wt. % chromium, equal
to or greater than 0.6 wt. % but lower than or equal to 1.2 wt. %
carbon, equal to or greater than 0.1 wt. % but lower than or equal
to 0.5 wt. % silicon, and the balance of iron.
[0035] The present invention also proposes a fabrication method of
a low-density high-toughness alloy, wherein a raw material, which
comprises: equal to or greater than 23 wt. % but lower than or
equal to 33 wt. % manganese, equal to or greater than 8.1 wt. % but
lower than or equal to 9.8 wt. % aluminum, equal to or greater than
3 wt. % but lower than or equal to 5.0 wt. % chromium, equal to or
greater than 0.6 wt. % but lower than or equal to 1.2 wt. % carbon,
equal to or greater than 0.1 wt. % but lower than or equal to 0.24
wt. % silicon, and the balance of iron, is melted to form an
alloy.
[0036] To enable the objectives, technical contents,
characteristics and accomplishments of the present invention to be
more easily understood, the theoretical basis of the alloy design
and the embodiments of the present invention are to be described
below in detail in cooperation with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The patent or application file contains at least one
drawing(s) executed in color. Copies of this patent or patent
application publication with color drawing(s) will be provided by
the office upon request and payment of the necessary fee.
[0038] FIG. 1 is a diagram showing the relationship between the
silicon content and the fluidity of the alloy consisting of 30.4
wt. % Mn, 8.8 wt. % Al, 5.1 wt. % Cr, 1.03 wt. % C, Xwt. % Si, and
the balance of Fe.
[0039] FIG. 2 is a diagram showing the relationship between the
aluminum content and the fluidity of the alloy, consisting of 30.4
wt. % Mn, Xwt. % Al, 5.1 wt. % Cr, 1.03 wt. % C, 0.18 wt. % Si, and
the balance of Fe.
[0040] FIG. 3 is a diagram showing the depth profile of the
alloying elements on the surface layer of the alloy containing:
30.4 wt. % Mn, 7.2 wt. % Al, 5.1 wt. % Cr, 1.03 wt. % C, 0.18 wt. %
Si, and the balance of Fe.
[0041] FIG. 4 is a diagram showing the depth profile of the
alloying elements on the surface layer of the alloy containing:
30.4 wt. % Mn, 8.1 wt. % Al, 5.1 wt. % Cr, 1.03 wt. % C, 0.18 wt. %
Si, and the balance of Fe.
[0042] FIG. 5 is a diagram showing the potentiodynamic polarization
curves performed in 5% NaCl solution for both the alloys containing
different aluminum contents respectively consisting of 30.4 wt. %
Mn, 7.2 wt. % Al, 5.1 wt. % Cr, 1.03 wt. % C, 0.18 wt. % Si and the
balance of Fe, and 30.4 wt. % Mn, 8.1 wt. % Al, 5.1 wt. % Cr, 1.03
wt. % C, 0.18 wt. % Si and the balance of Fe.
[0043] FIG. 6(a) and FIG. 6(b) are color diagrams illustrating the
alloy of Fe-30.4% Mn-8.8% Al-5.1% Cr-1.03% C-0% Si formed with wood
head.
[0044] FIG. 6(c) and FIG. 6.(d) are color diagrams illustrating the
alloy of Fe-30.4% Mn-8.8% Al-5.1% Cr-1.03% C-0% Si formed with iron
head.
[0045] FIG. 7(a) and FIG. 7(b) are color diagrams illustrating the
alloy of Fe-30.4% Mn-8.8% Al-5.1% Cr-1.03% C-0.05% Si formed with
wood head.
[0046] FIG. 7(c) and FIG. 7(d) are color diagrams illustrating the
alloy of Fe-30.4% Mn-8.8% Al-5.1% Cr-1.03% C-0.05% Si formed with
iron head.
[0047] FIG. 8(a), FIG. 8(b), FIG. 8(c), and FIG. 8(d) are color
diagrams illustrating the alloy of Fe-30.4% Mn-8.8% Al-5.1%
Cr-1.03% C-0.11% Si formed with wood head.
[0048] FIG. 8(e) and FIG. 8(f) are color diagrams illustrating the
alloy of Fe-30.4% Mn-8.8% Al-5.1% Cr-1.03% C-0.11% Si formed with
iron head.
[0049] FIG. 9(a), FIG. 9(b), FIG. 9(c), and FIG. 9(d) are color
diagrams illustrating the alloy of Fe-30.4% Mn-8.8% Al-5.1%
Cr-1.03% C-0.17% Si formed with wood head.
[0050] FIG. 9(e) and FIG. 9(f) are color diagrams illustrating the
alloy of Fe-30.4% Mn-8.8% Al-5.1% Cr-1.03% C-0.17% Si formed with
iron head.
[0051] FIG. 10(a), FIG. 10(b), FIG. 10(c), FIG. 10(d), FIG. 10(e),
and FIG. 10(f) are color diagrams illustrating the alloy of
Fe-30.4% Mn-x % Al-5.1% Cr-1.03% C-0.18% Si alloy (a) and (b) x=6,
(c) and (d) x=7.4, (e) and (f) x=8.1.
DETAILED DESCRIPTION OF THE INVENTION
[0052] The alloy of the present invention is based on iron,
manganese, aluminum, chromium, carbon, and silicon elements.
According to the research of the inventors, when the
Fe--Mn--Al--Cr--C alloy contains equal to or greater than 0.1 wt. %
but lower than or equal to 0.24 wt. % silicon and equal to or
greater than 8.1 wt. % but lower than or equal to 9.8 wt. %
aluminum, a fine carbide (Fe, Mn).sub.3AlC.sub.x (referred to as
.kappa.'-carbide hereinafter) having a L'1.sub.2 ordered phase will
homogeneously and coherently precipitate within austenite matrix
with FCC crystalline structure, and the casting thereof can obtain
superior strength without any heat treatment. The atomic
arrangement of the L'1.sub.2 ordered structure of the
.kappa.'-carbide is similar to that of the FCC structure of the
austenite phase except that the types of atoms therein are not
completely identical. The lattice constant of the .kappa.'-carbide
(a.sub..kappa.=0.376 nm) is very close to that of the austenitic
matrix (a.sub..UPSILON.=0.371 nm), and there is only 1.3 wt. %
difference between them. Therefore, a coherent interface can exist
between the .kappa.'-carbide and the austenitic matrix, and the
atoms at both sides of the interface can be completely bonded
together one by one separately just as the atoms inside their own
phases; therefore, there is no edge dislocation to form on the
interface because edge dislocations are to modify the huge stress
field induced by different structures or different lattice
constants. As the atoms at both sides of the interface can be
completely bonded together one by one separately, the atoms on the
interface between those two phases are hard to move or diffuse.
Therefore, when there is a coherent interface between the
.kappa.'-carbide and the austenite matrix, the fine
.kappa.'-carbides will not grow too rapidly inside the austenite
matrix during cooling of the casting from pouring temperature, so
that the casting will not change drastically from a ductile one to
a brittle one. By comparison, the aforementioned patents have to
use a high-temperature vacuum solid solution heat treatment and an
aging heat treatment to obtain the microstructures of different
ratios of precipitated phases before those alloys are used as the
material of the golf-club heads. In contrast to those disclosed
Fe--Mn--Al--C alloys, the alloy of the present invention may have
fine .kappa.'-carbides uniformly distributed in the austenite
matrix and may also obtain a superior combination of elongation
(30.about.60%) and tensile strength (100.about.135 ksi) even
without any heat treatment. It is also noted that the alloy
provided herein is used under as-cast condition, which is met
requirement different from those used in hot-forged, hot-rolled, or
cold-rolled condition and heat-treatment after process.
[0053] Besides, in the present invention, equal to or greater than
0.1 wt. % or lower than or equal to 0.24 wt. % silicon is added
into the Fe--Mn--Al--C alloy to improve its castability and promote
its liquid-state fluidity. Therefore, the tiny logo letters of the
casting, the minute U/V-section trenches on the striking face, and
the thin-thickness regions of the golf-club head may be easily
formed in the casting process without extra mechanical carving, and
the fabrication cost thereof may also be saved. Owing to the
promoted liquid-state fluidity, the molten alloy can effectively
feed the interdendrite porosity caused by the physical shrinkage
during the solidification process. Thus, the problems of cracks,
which are induced by the internal shrinkage cavities during a
plastic working process, such as a forging process and a rolling
process, may be overcome. The inventors had undertaken a research
to study the influence of the different silicon amount on the
fluidity of the alloy comprising by weight percent: Fe-30.4%
Mn-8.8% Al-5.1% Cr-1.03% C-X % Si; the 1550.degree. C. molten
silicon-free alloy and the 1550.degree. C. molten alloys containing
different ratios of silicon are poured into shell molds having
spiral runner and pre-heated at 1000.degree. C., and the lengths of
the solidified alloys are compared with the length of the
solidified silicon-free alloy, wherein X=0, 0.11, 0.17, 0.24, 0.30,
0.42, 0.60, 0.73, 0.85, and 1.17, and the length of the solidified
silicon-free alloy is set to be 1. The test result is shown in FIG.
1. From FIG. 1, it can be seen that the silicon-free alloy has the
shortest length and the relative lowest fluidity. When a slight
amount of silicon as low as only 0.11 wt. % is added to the alloy,
the length of the solidified alloy increases obviously. With the
increase of silicon content, the length of the solidified alloy
also increases proportionally until the silicon content reaches
0.42 wt. %; when the silicon content is above 0.42 wt. %,
increasing the silicon ratio can no more increase the fluidity
obviously.
[0054] When only the fluidity is considered, at least 0.42 wt. %
silicon should be added into the alloy of Fe-30.4% Mn-8.8% Al-5.1%
Cr-1.03% C. However, from the research performed by the inventors
and implemented with SEM (scanning electronic microscope), EDS
(energy dispersive spectrometer), TEM (transmission electronic
microscope), and a tensile test, it can be seen: the as-cast
structure of the alloy of Fe-30.4 wt. % Mn-8.8 wt. % Al-5.1 wt. %
Cr-1.03 wt. % C with the addition of silicon of 0.3 wt. % or above
contains dendrites and interdendrites interweaved among the
dendrite structures. It is noted that during solidification
process, the austenite dendrites solidify firstly, and meanwhile,
the aluminum atoms and the silicon atoms are expelled into the
unsolidified interdendrite liquid phases; and with the decrease of
temperature, the Al-rich and Si-rich liquid phases also solidify
gradually. Although the Al and Si contents of the alloy of Fe-30.4
wt. % Mn-8.8 wt. % Al-5.1 wt. % Cr-1.03 wt. % C-0.3 wt. % Si are
respectively only 8.8 wt. % and 0.3 wt. % on average, the Al and Si
contents of the lastly solidified interdendrite regions are as high
as 10.2 wt. % and 0.68 wt. % respectively, examined by SEM and EDX.
From the TEM analysis and the phase identification, it is known: in
the interdendrite regions, aluminum and silicon are the
ferrite-forming elements, and in the Al-rich ferrite phase,
increasing the silicon content will transform the disordered
ferrite phase into a very brittle D0.sub.3 ordered phase, which
reduces the toughness of the alloy. It is also confirmed by the
tensile test: when the silicon content in the alloy of Fe-30.4 wt.
% Mn-8.8 wt. % Al-5.1 wt. % Cr-1.03 wt. % C-Xwt. % Si is equal to
or greater than 0.3 wt. %, the ductility of the as-cast alloy is
reduced to 15% or below; such an alloy cannot be applied to the
golf-club head unless it has been heat treated. When the silicon
content of the alloy is equal to or greater than 0.3 wt. %, the
ductility of the as-cast alloy without a heat treatment decreases
obviously; however, as only 0.24 wt. % silicon is added to the
alloy, the fluidity of the molten alloy could be significantly
improved. Therefore, under the considerations of both ductility and
fluidity, the silicon content of the alloy should be controlled to
be equal to or greater than 0.1 wt. % but lower than or equal to
0.24 wt. %. In this case, the molten alloy can have a suitable
fluidity, and the as-cast alloy without any heat treatment can also
have a superior combination of toughness and strength. However, in
the present invention, when the silicon content of the alloy is
greater than 0.24 wt. % but lower than or equal to 0.5 wt. %, the
alloy of the present invention can still possess fine elongation
and strength via being heat treated for 1.about.3 hours at the
temperature of 950.about.1200.degree. C. The structures of present
invention is distinct from those disclosed in Taiwan patent of
Publication Numbers 178648, and US patents of Publication Numbers
of 20030077479, 20030082067, and 20050006007, which have none
silicon or have too great a silicon content as high as
0.8.about.1.5 wt. %.
[0055] The inventors had also undertaken a research to study the
influence of the aluminum content on the fluidity of the alloy of
Fe-30.4 wt. % Mn-Xwt. % Al-5.1 wt. % Cr-1.03 wt. % C-0.18 wt. % Si;
the 1550.degree. C. molten alloys containing different ratios of
aluminum are poured into shell molds having spiral runner and
pre-heated at 1000.degree. C., and the lengths of the solidified
alloys are compared with the length of the solidified alloy
containing 6.0 wt. % aluminum, wherein X=6.0, 7.4, 8.1, 9.1, 9.8,
10.6, and 11.8, and the length of the solidified alloy containing
6.0 wt. % aluminum is set to be 1. The test result is shown in FIG.
2. From FIG. 2, it can be seen: the alloy containing 6.0 wt. %
aluminum has the shortest length and the lowest fluidity; with the
increase of aluminum--a low-melting-point element, the fluidity of
the alloy also increases.
[0056] As discussed above, the aluminum atoms will be segregated
into the interdendrite regions during the solidification process,
and the local aluminum content is much greater than the average
aluminum content, which causes the reduction of toughness. From the
observation performed by the inventors with TEM, aluminum is one of
constituent elements of the carbide (Fe,Mn).sub.3AlC.sub.x
(.kappa.'-carbide); therefore, decreasing aluminum content will
inhibit the .kappa.'-carbide's precipitation on the austenite
matrix and decrease the amount of .kappa.'-carbide, which causes
the reduction of strength. The inventors also utilized XPS/ESCA
(X-Ray Photoelectron Spectroscopy/Electron Spectroscopy for
Chemical Analysis) to analyze the oxides of the protective
passivation layer on the surface of the alloy. From the analysis
result, it is found that the passivation layer consists primarily
of protective anti-corrosion Cr.sub.2O.sub.3 and Al.sub.2O.sub.3,
and minor proportion of protective anti-oxidation SiO.sub.2, and
small proportion of non-corrosion-resistant oxides, such as
FeO(Fe.sub.3O.sub.4), Fe.sub.2O.sub.3, MnO(Mn.sub.3O.sub.4), and
Mn.sub.2O.sub.3. FIG. 3 and FIG. 4 are diagrams respectively
showing the depth profiles of the surface oxides of the alloy of
Fe-30.4 wt. % Mn-7.2 wt. % Al-5.1 wt. % Cr-1.03 wt. % C-0.18 wt. %
Si and the alloy of Fe-30.4 wt. % Mn-8.1 wt. % Al-5.1 wt. % Cr-1.03
wt. % C-0.18 wt. % Si. From FIG. 3 and FIG. 4, the inventors make
an important discovery: the content of Al.sub.2O.sub.3, which can
protect the metallic substrate, increases greatly when the aluminum
content changes from 7.2 wt. % to 8.1 wt. % according to the atomic
ratios of aluminum in FIG. 3 and FIG. 4 (The aluminum atoms in the
surface layer exist in the form of Al.sub.2O.sub.3). FIG. 5 shows
the potentiodynamic polarization curves performed in 5% NaCl
solution for the alloy of Fe-30.4 wt. % Mn-7.2 wt. % Al-5.1 wt. %
Cr-1.03 wt. % C-0.18 wt. % Si and the alloy of Fe-30.4 wt. % Mn-8.1
wt. % Al-5.1 wt. % Cr-1.03 wt. % C-0.18 wt. % Si. From FIG. 5, it
is found that since the amount of the protective Al.sub.2O.sub.3 on
the surface of the alloy with higher aluminum content of 8.1 wt. %
increases greatly, the passivation current density (I.sub.p)
decreases obviously, and the passivation potential (.DELTA.E) and
the pitting-corrosion potential (E.sub.pp) increase obviously;
therefore, the corrosion resistance of the alloy of Fe-30.4 wt. %
Mn-8.1 wt. % Al-5.1 wt. % Cr-1.03 wt. % C-0.18 wt. % Si containing
8.1 wt. % Al is much better than that of the alloy of Fe-30.4 wt. %
Mn-7.2 wt. % Al-5.1 wt. % Cr-1.03 wt. % C-0.18 wt. % Si containing
only 7.2 wt. % Al. Taking all the factors of the fluidity,
elongation, strength, and corrosion resistance of the alloy into
consideration and making a compromise between them, the aluminum
content should be controlled to be equal to or greater than 8.1 wt.
% but lower than or equal to 9.8 wt. %; in this case, the molten
alloy of the present invention has superior fluidity, and the
as-cast alloy of the present invention can also possess a superior
combination of toughness and strength even without any heat
treatment. The alloy of the present invention is distinct from
those Taiwan patents of Publication Numbers 178648 and 185568, and
US patent of Publication Number 20030077479, whose aluminum
contents are lower than 8.0 wt. %.
[0057] Based on the abovementioned alloy design, which limits the
silicon content to be equal to or greater than 0.1 wt. % but lower
than or equal to 0.24 wt. %, and limits the aluminum content to be
equal to or greater than 8.1 wt. % but lower than or equal to 9.8
wt. %, and to achieve the objective that the as-cast alloy can
possess a superior combination of toughness and strength even
without any heat treatment, the contents of the other alloying
elements, such as Mn, Cr, C, are to be appropriately modified or
limited as below.
[0058] Manganese is an austenite-stabilized element and austenite
former, which can increase the proportion of austenite and promote
the elongation of the alloy. To enable the as-cast alloy to have a
superior ductility, the manganese content has to be equal to or
greater than 23 wt. % because the single austenite structure would
not be formed under the condition of manganese lower than 15 wt. %.
However, when the manganese content is over 33 wt. %, the
precipitation of .beta.-Mn phase will deteriorate the ductility of
the alloy. Therefore, the manganese content should be controlled to
be equal to or greater than 23 wt. % but lower than or equal to 33
wt. %. Carbon is not only an austenite-stablizer but also a main
constituent element of the carbide (Fe,Mn).sub.3AlC.sub.x
(.kappa.'-carbide). Insufficient carbon content, such as lower than
0.5 wt. %, will form a two-phase structure of austenite and
ferrite, decrease the proportion of austenite and inhibit the
precipitation of .kappa.'-carbide, which lead to the decrease of
both ductility and strength of the alloy. Increasing the carbon
content can increase the proportion of austenite and the amount of
the .kappa.'-carbide precipitated within the austenite matrix.
However, excessive carbon content causes coarse carbides to
precipitate on the grain boundary, which results in the decrease in
the ductility of the alloy. Chromium is not only a ferrite-former
element but also a carbide-forming element. Further, chromium can
form a protective Cr.sub.2O.sub.3 oxide layer on the surface of the
alloy and benefit the corrosion resistance of the alloy. Too low a
chromium content will not provide enough protection from corrosion.
Too high a chromium content, such as higher than 6.5 wt. %, with a
high carbon content will cause the formation of Cr.sub.7C.sub.3
carbide with the HCP (hexagonal close packing) crystalline
structure, which not only reduces the ductility of the alloy but
also results in the chromium-depletion regions that will to be the
attacked sites of pitting corrosion or intergranular corrosion.
Therefore, to achieve the objective that the as-cast alloy can have
a superior combination of toughness and strength even without any
heat treatment, the chromium content should be limited to be equal
to or greater than 3.0 wt. % but lower than or equal to 5.0 wt. %,
and the carbon content should be restricted to be equal to or
greater than 0.6 wt. % but lower than or equal to 1.2 wt. %.
[0059] From the inventors' research, it is also found that adding
molybdenum into the alloy can raise the pitting-corrosion potential
(E.sub.pp) of the potentiodynamic polarization curve performed in
5% NaCl solution and improve the pitting-corrosion resistance.
Notwithstanding that there is a slight reduction in the ductility
of the alloy, the strength of the alloy can be further raised when
the addition amount of molybdenum does not exceed 1.5 wt. %. For
the latest years, molybdenum has become very expensive; therefore,
molybdenum will be selectively added into the alloy, and with
surveying all the properties, whether molybdenum is added into the
alloy depends on whether the Mo-free alloy can meet the
requirement. Anyway, molybdenum may be flexibly added into the
alloy within the range of at most 1.5 wt. % in order to get an
optimal compromise between product quality and price
competence.
[0060] In summary, the alloy of the present invention consists
essentially of: 23.about.33 wt. % Mn, 8.1.about.9.8 wt. % Al,
3.about.5.0 wt. % Cr, 0.6.about.1.2 wt. % C, 0.1.about.0.24 wt. %
Si and the balance of Fe, in which up to 1.5 wt. % Mo may also be
added into the alloy of the present invention. The alloy of the
present invention has superior fluidity in liquid state; even in
non-heat-treated as-cast condition, the alloy of the present
invention has a density as low as 6.6.about.6.9 g/cm.sup.3, a
superior elongation as high as 30.about.60%, a superior tensile
strength as high as 100.about.135 ksi, high damping capacity, and
high corrosion resistance. When the Fe--Mn--Al golf-club heads are
made from the alloy of the present invention, the fabrication cost
can be reduced obviously.
[0061] The alloy of the present invention, which consists
essentially of: 23.about.33 wt. % Mn, 8.1.about.9.8 wt. % Al,
3.about.5.0 wt. % Cr, 0.6.about.1.2 wt. % C, 0.1.about.0.24 wt. %
Si, and the balance of Fe with up to 1.5 wt. % Mo being optionally
added to the alloy, can be melted in the atmosphere, in vacuum, or
in a reducing atmosphere, and then cast into molds. Without any
heat treatment, the casting can be directly sandblasted, ground,
welded, drilled, surface-treated, and art-worked to form an as-cast
type golf-club head. As the alloy of the present invention has
superior ductility even in the as-cast state, the as-cast castings
thereof are adaptable to the succeeding hot working or cold working
and can be fabricated into forging type golf-club heads or complex
type (casting plus forging) golf-club heads.
[0062] In order to prove the availability of the present invention,
and to enable the persons skilled in the art to understand, make,
and use the present invention, the embodiments of the present
invention are to be described below; however, those embodiments are
not intended to limit the scope of the present invention.
Embodiment 1
[0063] An alloy according to the present invention consists
essentially of: 26 wt. % Mn, 8.3 wt. % Al, 6.0 wt. % Cr, 0.68 wt. %
C, 0.18 wt. % Si, and the balance of Fe. The alloy may be melted
with a high-frequency induction furnace, and then, the molten alloy
is poured into pre-heated lost-waxed shell molds of golf-club
heads. As the molten alloy has superior fluidity, it can easily
fill into all the mold cavities and thin-thickness regions. After
the castings together with the shell molds are cooled to room
temperature, they are processed with the following steps of
shell-mold shaking-out, cutting gates and runners, sandblasting,
grinding, welding, drilling, surface-treatment, and art-working.
Even without any heat treatment, the as-cast golf-club head can
still possess superior properties and has a density as low as 6.74
g/cm.sup.3, an elongation as high as 59.1%, a tensile strength as
great as 108.2 ksi, and superior corrosion resistance. Thus, the
fabrication cost of golf-club heads can be greatly reduced.
Embodiment 2
[0064] An alloy according to the present invention consists
essentially of: 30.4 wt. % Mn, 8.8 wt. % Al, 5.1 wt. % Cr, 1.03 wt.
% C, 0.24 wt. % Si, and the balance of Fe. The alloy may be melted
with a high-frequency induction furnace, and then, the molten alloy
is poured into pre-heated lost-waxed shell molds of golf-club
heads. As the molten alloy has superior fluidity, it can easily
fill all the mold cavities and thin-thickness regions. After the
castings together with the shell molds are cooled to room
temperature, they are processed with the following steps of
shell-mold shaking-out, cutting gates and runners, sandblasting,
grinding, welding, drilling, surface-treatment, and art-working.
Even without any heat treatment, the as-cast golf-club head can
still have superior properties and has a density as low as
6.62/cm.sup.3, an elongation as high as 43.3%, a tensile strength
as great as 124.5 ksi, and superior corrosion resistance. Thus, the
fabrication cost of golf-club heads can be greatly reduced.
Embodiment 3
[0065] An alloy according to the present invention consists
essentially of: 28 wt. % Mn, 8.8 wt. % Al, 5.1 wt. % Cr, 1.02 wt. %
C, 0.21 wt. % Si, 1.0 wt. % Mo and the balance of Fe. The alloy may
be melted with a high-frequency induction furnace, and then, the
molten alloy is poured into pre-heated lost-waxed shell molds for
golf-club heads. As the molten alloy has superior fluidity, it can
easily fill all the mold cavities and thin-thickness regions. After
the castings together with the shell molds are cooled to room
temperature, they are processed with the following steps of
shell-mold shaking-out, cutting gates and runners, sandblasting,
grinding, welding, drilling, surface-treatment, and art-working.
Even without any heat treatment, the as-cast golf-club head can
still possess superior properties and has a density as low as 6.83
g/cm.sup.3, an elongation as high as 35.2%, a tensile strength as
great as 133.1 ksi, and superior corrosion resistance. Thus, the
fabrication cost of the golf-club head can be greatly reduced.
[0066] In the present invention, the principles of alloy design and
the knowledge of the microstructures in materials are applied to
invent an alloy for golf-club heads, which has a density as low as
6.6.about.6.9 g/cm.sup.3 and a superior damping capacity, and can
still have a superior elongation as high as 30.about.60%, a
superior tensile strength as great as 100.about.135 ksi and a
superior corrosion resistance even without any heat treatment, hot
working, or plastic cold working. Via appropriate alloy design, the
alloy of the present invention has improved fluidity and
castability in liquid state, and has a superior plastic
workability. Therefore, the present invention can greatly reduce
the cost and save the time of the fabrication of the Fe--Mn--Al--C
golf-club heads.
[0067] In the disclosure of U.S. Pat. No. 4,975,335 which claims
articles and parts made of an alloy consist essentially of by
weight 10% to 45% manganese, 4% to 15% aluminum, 0.01% to 1.4%
carbon, up to 2.5% silicon, about 3% to 12% chromium, and the
balance essentially iron. There is an extremely broader range of
silicon content as claimed above. For iron based alloys, it is
known to a person having ordinary skill in the art that alloys with
0 to 2.5% silicon contents must have entirely different
characteristics of strength, elongation, fluidity, castability,
machinability, corrosion resistance, wear resistance, impact
resistance and so on. Similarly, this phenomenon is also occurred
in the Fe--Mn--Al--C based alloy. But, no demonstration about the
effect of various silicon contents within the extremely broader
range of 0 to 2.5 wt. % on the Fe--Mn--Al--C based alloy could be
found in the U.S. Pat. No. 4,975,335. Also, silicon is absent in
all alloys from examples 1 to 10 disclosed in the U.S. Pat. No.
4,975,335 so that the examples can not embody the influence of
various silicon contents on the Fe--Mn--Al--C based alloys.
[0068] In contrast to claims 2.about.4, 6, 8.about.13 in U.S. Pat.
No. 4,975,335 in which the claimed alloys comprise no silicon, they
are different from those with maximally 2.5 wt. % Si in claims 1
and 7. Based on the sections of DETAIL OF INVENTION, EXAMPLE and
CLAIM in the specification of U.S. Pat. No. 4,975,335, their
claimed alloys with maximally 2.5 wt. % Si and without Si have no
distinction in characteristics from each other. Thus, according to
the disclosure of U.S. Pat. No. 4,975,335, whether the
Fe--Mn--Al--C based alloys include Si with maximally 2.5% or no Si
is not critical. Furthermore, as demonstrated in the last paragraph
in the abstract and all examples in the specification of U.S. Pat.
No. 4,975,335, for enhancing the mechanical properties, serial
fabrication processes of hot working, cold working and then heat
treatment are performed to obtain a tensile strength of
112.about.146 ksi and an elongation of 58.about.67%. The ranges of
the tensile strength and elongation are acquired from the summary
of the examples in the specification of U.S. Pat. No.
4,975,335.
[0069] However, in the section of detailed description of the
present invention, the effects of silicon alloying element and its
content on the mechanical properties and castability of the
Fe--Mn--Al--Cr--C based alloys are explicitly revealed. Based on
our investigation on the effect of silicon on the Fe--Mn--Al--Cr--C
alloys, the present inventors demonstrate that the more narrow
range of silicon content with limited ranges of other alloying
elements Mn, Al, Cr, C are significantly critical and productive of
new and unexpected results. The addition of a limited range of
silicon content is able to enhance the formation of
.kappa.'-carbide during the period of cooling after casting. Then
the alloy in the as-cast condition can possess a tensile strength
of 100.about.135 ksi and an elongation of 30.about.60%, even
without any heat treatment, hot working, or cold working.
Therefore, the regular fabrication processes of expensive hot die
forging (swage) and vacuum heat treatment for making the golf-club
heads of Fe--Mn--Al--C based alloys are no longer required, so that
the fabrication cost of the golf-club heads made of the
Fe--Mn--Al--Cr--C based alloy disclosed in the present invention
can be greatly reduced. Moreover, the present inventors also reveal
that once the addition of the Si content exceeds the maximum
limitation disclosed in the present invention, the elongation of
the as-cast alloy will be drastically deteriorated due to the
precipitation of the brittle ordered D0.sub.3 phase in
interdedrites in typical casting structure.
[0070] In conclusion, the composition of the alloy of the present
invention is distinct from the compositions of the
golf-club-head-related Fe--Mn--Al--C alloys disclosed in the US
patents of Publication Numbers of 20030077479, 20030082067 and
20050006007, and the Taiwan Patents of Publication Numbers 178648,
185568 and 1235677. The alloy of the present invention has a low
density; further, even though none of heat treatment, cold working,
and hot working (such as forging and rolling) is used, the as-cast
alloy of the present invention can still have high toughness, high
strength, high damping capacity, and high corrosion resistance.
Furthermore, as the alloy of the present invention also has an
improved fluidity in liquid state, the tiny letters, the trenches
on the striking face, and the thin-thickness regions of the
golf-club head can be formed completely in the casting process, and
the mechanical carving is no more needed. The interdendrite can be
easily fed by the molten alloy; thereby, the problem of internal
shrinkage porosity is overcome, and the defective fraction and the
fabrication cost of the Fe--Mn--Al--C golf-club heads are greatly
reduced.
[0071] FIG. 6(a) and FIG. 6(b) are color diagrams illustrating the
alloy of Fe-30.4% Mn-8.8% Al-5.1% Cr-1.03% C-0% Si formed with wood
head. FIG. 6(c) and FIG. 6.(d) are color diagrams illustrating the
alloy of Fe-30.4% Mn-8.8% Al-5.1% Cr-1.03% C-0% Si formed with iron
head. Without the addition of silicon, the fluidity of alloy is not
enough to form product during de-waxed casting process.
[0072] FIG. 7(a) and FIG. 7(b) are color diagrams illustrating the
alloy of Fe-30.4% Mn-8.8% Al-5.1% Cr-1.03% C-0.05% Si formed with
wood head. FIG. 7(c) and FIG. 7(d) are color diagrams illustrating
the alloy of Fe-30.4% Mn-8.8% Al-5.1% Cr-1.03% C-0.05% Si formed
with iron head. With addition of 0.05 silicon, the fluidity of
alloy is improved but not enough to form the product in good
quality.
[0073] FIG. 8(a), FIG. 8(b), FIG. 8(c), and FIG. 8(d) are color
diagrams illustrating the alloy of Fe-30.4% Mn-8.8% Al-5.1%
Cr-1.03% C-0.11% Si formed with wood head. FIG. 8(e) and FIG. 8(f)
are color diagrams illustrating the alloy of Fe-30.4% Mn-8.8%
Al-5.1% Cr-1.03% C-0.11% Si formed with iron head. The fluidity of
alloy is better than ones in FIG. 7(a), 7(b), 7(c) and 7(d). FIG.
9(a), FIG. 9(b), FIG. 9(c), and FIG. 9(d) are color diagrams
illustrating the alloy of Fe-30.4% Mn-8.8% Al-5.1% Cr-1.03% C-0.17%
Si formed with wood head. FIG. 9(e) and FIG. 9(f) are color
diagrams illustrating the alloy of Fe-30.4% Mn-8.8% Al-5.1%
Cr-1.03% C-0.17% Si formed with iron head.
[0074] FIG. 10(a), FIG. 10(b), FIG. 10(c), FIG. 10(d), FIG. 10(e),
and FIG. 10(f) are color diagrams illustrating the alloy of
Fe-30.4% Mn-x % Al-5.1% Cr-1.03% C-0.18% Si alloy (a) and (b) x=6,
(c) and (d) x=7.4, (e) and (f) x=8.1.
[0075] Those embodiments described above are to clarify the present
invention to enable the persons skilled in the art to understand
and use the present invention; however, the embodiments are not
intended to limit the scope of the present invention; therefore,
any equivalent modification and variation according to the spirit
of the present invention is still to be included within the scope
of the claims of the present invention stated below.
* * * * *