Stock material or miscellaneous articles – All metal or with adjacent metals – Surface feature
Reexamination Certificate
2001-10-19
2003-09-09
Zimmerman, John J. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Surface feature
C420S074000, C148S337000, C148S619000, C473S349000
Reexamination Certificate
active
06617050
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an alloy for use in making of golf clubs, particularly to an alloy with low density, high ductility and high resistance to corrosion.
2. Description of Related Art
An alloy is a mixture of metals, such as a metal mixed with additions of metals or sub-metals for various special purposes. When a metal is mixed with other metals or sub-metals, its mechanical properties, such as the melting temperature, strength, ductility, electrical resistance, thermal conductance, heat treatment properties, resistance to corrosion and magnetic properties are all promoted.
A set of golf clubs generally comprises woods, irons, pitching wedges, sand wedges, putters, etc. The iron club has a shorter striking distance but gives better good controllability and a higher striking height than the wood club has. In recent years, the iron club has been designed to have a hollow club head in order that the iron club may possess the advantages of the wood club.
With reference to the table in
FIG. 1
, two manufacturing methods of the head of the golf club are listed; one of them is precision lost-wax casting and the other one is forging. Besides the methods listed in the table of
FIG. 1
, some iron club heads are finished by surface plating, such as nickel-plating, cobalt-plating, etc. and paneling. Among these methods, the method of the precision lost-wax casting has the lowest manufacturing cost, however the method of the forging has more advantages than the method of precision casting, which can be seen from the comparison in the table of FIG.
1
. The mechanical properties of the precision lost-wax casting and the forging are listed in the table of FIG.
2
.
The major object of the designing of the golf club is to improve the controllability and stability of striking via good striking points, and the designing has following tendencies:
1. the heads of the clubs are enlarged in order to increase sweet spots and the probability of successful striking; the volume of the woods can be from 280 cc to 310 cc, and even to 350 cc, and the irons also have some oversized features.
2. the center of gravity of the club head is lowered in order to obtain a very stable striking of the ball, good striking points and long striking distance.
3. the shape of the club head is designed to have a strengthened club face with low air drag.
Since the club heads have a variety shapes, an alloy metal is a popular material for manufacture thereof, particularly an alloy which combines high strength with high ductility and resistance to corrosion. However, the alloys which are used to make club head at present do not satisfy all the requirements of the club head. For example, titanium alloyed with stainless steel has good resistance to corrosion from a damp or salty atmosphere, however its ductility and impact value are not good enough; the 304 stainless steel has an elongation of 40%~60%, however its strength is not enough. The S25C with a tensile strength of 75 ksi~85 ksi and an elongation of 30%~35% is the best material for use in forging of a club head, however, its resistance to corrosion is a little insufficient.
The research of the golf materials shows that if an alloy for heads of golf clubs has low density, high ductility and toughness, then the head of the club may be designed with a larger volume, and also the controllability and striking stability of the club will be increased. Presently, manufacturers of golf clubs have a common opinion that the best alloy for the golf club irons should have a tensile strength about 80 ksi to 120 ksi, which is 1.0 to 1.5 times of the tensile strength of the soft iron used for forging, an elongation over 40% and the higher the better, a density below 7.9 g/cm
3
, and a good resistance to the corrosion.
It has been found that mechanical properties can be promoted by controlling the contents and by performing heat treatment to obtain high strength and toughness, good resistance of low or high temperature, and resistance to the corrosion. The following papers have described these characteristics in detail.
“the Structure and Properties of Austenitic Alloys Containing Aluminum and Silicon” by D. J. Schmatz, Trans. ASM., vol. 52, p. 898, 1960; “Phase Transformation Kinetics in Steel 9G28Yu9MVB” by G. B. Krivonogov et al., Phys. Met. & Metallog, vol. 4, p. 86, 1975; “An Austenitic Stainless Steel Without Nickel or Chromium” by S. K. Banerji, Met. Prog, p. 59, 1978; “Phase Decomposition of Rapidly Solidified Fe—Mn—Al—C Austenitic Alloys” by J. Charles et al., Met. Prog., p. 71, 1981; “Development of Oxidation Resistant Fe—Mn—Al Alloys” by J. Garcia, et al., Met. Prog., p. 47, 1982; “New Stainless Steel Without Nickel or Chromium for Alloys Applications” by R. Wang, Met. Prog, p. 72, 1983; “An Assessment of Fe—Mn—al Alloys as Substitutes for Stainless Steel” by J. C. Benz et al., Journal of Metals, p. 36, 1985; “New Cryogenic Materials” by J. Charles et al., Met. Prog, p. 71, 1981; “TEM Evidence of Modulated Structure in Fe—Mn—al—C Alloys” by K. H. Ham, Scripta Metall, vol. 20, p 33, 1986; Electron Microscope Observation of Phase Decompositions in an Austentic Fe-8.7 Al-29.7 M-1.04 C Alloy” by S. C. Tjong, Mater. Char, vol. 24, p. 275, 1990; “Grain Boundary Precipitation in an Fe-7.8 Al-1.7 Mn-0.8 Si-1.0 C Alloy” by C. N. Hwang et al., Scripta Metall, vol. 28, p109, 1993; “Hot-Rolled Alloy Steel Plate” by T. F. Liu U.S. Pat. No. 4,968,357, 1990.
Reviewing the above noted references, it can be found that in the Fe—Al—Mn—C based alloys, manganese content is added to stabilize the austenite structure and retain an FCC structure under a room or lower than room temperature, which is beneficial to enhance the workability and ductility of the alloy. An aluminum content has a strong effect on oxidation resistance. A carbon content mainly helps precipitation of strengthening elements when the alloy is quenched rapidly after a solution heat treatment at a temperature from 1050° C. to 1200° C., and then aged at a temperature from 450° C., to 750° C. The alloy has a mono austenite structure during the quenching, and the fine (Fe, Mn)
3
AlC
x
&kgr; carbides are precipitated coherently within the austenite matrix during the aging. Additionally, after a lengthy aging, phase decomposition like &ggr;→&agr;+&bgr;-Mn or &ggr;→&agr;+&bgr;-Mn+&kgr; is produced on the grain boundary of the alloy dependent on its chemical composition. The coarse precipitates of &bgr;-Mn will deteriorate the ductility of the alloy. Consequently, to obtain carbides precipitated coherently within the austenite matrix and without the coarse &bgr;-Mn being precipitated therein is an important method for the alloy to possess a satisfactory strength and ductility.
It is found that the Fe—Al—Mn based alloys mainly consisting of iron, 5 to 12 wt % aluminum, 20 to 35 wt % manganese, and 0.3 to 1.3 wt % carbon, and after being solution heat treated, quenched and aged, will have different mechanical properties dependent on their chemical compositions, the tensile strength has a range of 80 ksi to 200 ksi, the yield strength has a range from 60 ksi to 180 ksi and the elongation has a range from 62% to 25%. As shown in the tables of FIG.
3
and
FIG. 4
, the chemical compositions and mechanical properties of the typical Fe—Al—Mn alloys, which have been studied by experts in this field, are listed for comparison.
The inventor has worked on the analysis and study of the Fe-10 wt %, Al-30 wt %, Mn-1 wt %, C alloy and the Fe-8 wt %, Al-30 wt %, Mn-0.8 wt %, C alloy. The study proves that after being heat treated at a temperature of 1100° C. for 0.5 to 2 hours, the Fe-10 wt %, Al-30 wt %, Mn-1 wt %, C alloy has its hardness value from Hr
b
82.7 to 88.9, tensile strength from 111 ksi to 124 ksi, yield strength from 79.7 ksi to 97 ksi, elongation from 58.9% to 63.3%, the Hall-Petch relationship between the tensile strength (&sgr;) and the grain size (d): &sgr;=68.72+21.2×d
−0.46
, a metallograph as shown in
FIG. 5
,
O-Ta Precision Casting Co., Ltd.
Rosenberg , Klein & Lee
Zimmerman John J.
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