Patent Application
20080009368
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:
A metal alloy applied to manufacture a golf club head member in accordance with a preferred embodiment of the present invention is constructed from a stainless steel containing a predetermined amount of tungsten (W). In the preferred embodiment, other components are carbon (C), silicon (Si), manganese (Mn), nickel (Ni), chromium (Cr), tungsten (W) and iron (Fe) which are in the predetermined ratio of the following alloy components. Preferably, the alloy components of the metal alloy in accordance with the present invention satisfy the following conditions: carbon less than 0.08% by weight, silicon of about 0.5% to about 2.0% by weight, manganese of about 0.5% to about 2.0% by weight, nickel of about 5.0% to about 15.0% by weight, chromium of about 15.0% to about 30.0% by weight, tungsten of about 5.0% to about 15.0% by weight and the balance is essentially iron, as is given in Table 1. The density of the metal alloy of this preferred embodiment may vary in a range of 8 to 8.5.
Table 1 shows the alloy components of ASTM 304 and the metal alloy of a preferred embodiment of the present invention in percent by weight. As obtained from Table 1, contents of carbon (C), silicon (Si), manganese (Mn), phosphorous (P), sulfur (S), nickel (Ni), chromium (Cr), tungsten (W) and iron (Fe) are listed. In this embodiment, phosphorous and sulfur are added without departing from the scope and spirit of the present invention. In comparison with the present invention, ASTM 304 is absent tungsten that functions as a weighting material for the golf club head.
A manufacturing method for the metal alloy in practicing the present invention is similar to that described in U.S. Pat. No. 6,776,728, entitled “Weight Member for a Golf Club Head,” U.S. Pat. No. 6,758,764, entitled “Weight Member for a Golf Club Head,” and Taiwanese Patent Publication No. 589,215, entitled “Forging Composition and a Method thereof for Manufacturing a Golf Club Head” which are owned by the present assignee and hereby incorporated by reference in its entirety.
The manufacturing method for the metal alloy in accordance with the preferred embodiment of the present invention comprises the steps of: melting raw materials of pure iron, ferrosilicon, ferromanganese, ferrochromium nickel and tungsten in a high-temperature furnace (e.g. microwave furnace, not shown). The above raw materials may vary weigh percent of the contents of carbon, silicon, manganese, nickel, chromium and tungsten without departing from scope and spirit of the present invention. In a preferred embodiment, the metal alloy has carbon less than 0.08% by weight, silicon of about 0.5% to about 2.0% by weight, manganese of about 0.5% to about 2.0% by weight, nickel of about 5.0% to about 15.0% by weight, chromium of about 15.0% to about 30.0% by weight, tungsten of about 5.0% to about 15.0% by weight and the balance being essentially iron. The melting alloy is preferably poured into a molding apparatus (not shown) to form a casting selecting from configurations of a golf club head, a striking plate, a weighting member or other club head members. In another preferred embodiment, the metal alloy in accordance with the present invention may be in an alloy bar form for a following forging procedure.
Referring now to
In the preferred embodiment, the raw materials may be selected from pure iron, other elements (i.e. carbon, silicon, manganese, chromium, nickel and tungsten) of pure metals (containing normal small amount of impurities) and ferroalloys thereof. The amount of alloy components applied in the present invention may be varied according to elements contained in the raw materials of pure iron, pure metals or ferroalloys in manufacturing the golf club head members. In addition, the stainless steel alloy of the present invention, due to the differences of raw materials, may further include incidental impurities, molybdenum (Mo), copper (Cu), phosphorous (P) and sulfur (S) for example.
As shown in Table 2, tensile strength is a maximum of stress that the metal alloy can normally withstand; yielding strength is a threshold limit value of stress that can shift the structure of metal alloy from elastic deformation to permanent deformation.
Table 2 shows the mechanical characteristics of ASTM 304 and the metal alloy of the present invention including tensile strength, yielding strength and elongation. As shown in Table 2, the tensile strength, yielding strength and hardness of the metal alloy of the present invention are greater than those of ASTM 304 due to the different amount of elements. Further, the metal alloy of the present invention has a greater density that is suitable for functioning as a weighting material of the golf club head. Finally, the metal alloy of the present invention has an excellent property of corrosion resistance same with that of ASTM 304.
Table 3 shows the application properties of ASTM 304 and the metal alloy of the present invention for the golf club head including hardness, embeddness, heterogeneous metal weldability, corrosion resistance, surface, hosel angle adjustability and thermal cracking sensibility. As shown in Table 3, the hardness, heterogeneous metal weldability and thermal cracking sensibility of the metal alloy of the present invention are greater than those of ASTM 304 due to the different amount of elements.
Referring back to Table 1, in comparison with ASTM 304, the metal alloy in accordance with the present invention further includes tungsten of about 5.0% to about 15.0% by weight and incidental impurities (e.g. molybdenum less than 1.0% by weight and less than 1.0%). As has been apparent from Table 1 through 3 and
(1) Carbon is less than 0.08% by weight, preferably less than 0.07% by weight, 0.06% by weight, 0.05% by weight or 0.04% by weight, so as to increase hardness and tensile of the carbon-contained metal alloy.
(2) Silicon is in a range of about 0.5% by weight to about 2.0% weight, preferably selecting from 0.7%, 0.9%, 1.1%, 1.4% or 1.7% by weight, so as to enhance fluidness of the molten metal alloy in a casting procedure. It would be advantageous that this alloy component can aid precipitation of carbide in ferrite such that tensile strength of the metal alloy can be increased and is in the range of 90 ksi to 110 ksi (see Table 2). In this manner, the metal alloy is suitable for manufacturing the striking plate which can withstand a higher stress in striking a golf ball. Also, the structure of the striking plate can be designed to have a relatively thinner thickness due to the fact that the striking plate can provide a higher tensile strength (i.e. impact resistance). Consequently, the striking plate can be designed to have a relatively lower weight by reducing its thickness such that the total weight of the golf club head can be redesigned. Accordingly, it would be advantageous to lower a center of gravity of the golf club head. By way of example, the golf club head body can be made from a heavy material having a relatively high density so as to increase moment of inertia if the striking plate is designed to have such a relatively lower (lighter) weight. Accordingly, the silicon-contained metal alloy can enhance the golf club head to have a greater striking ability.
(3) Manganese is in a range of about 0.5% by weight to about 2.0% weight, preferably selecting from 0.7%, 0.9%, 1.1%, 1.4% or 1.7% by weight, so as to enhance the structure of austenite of the metal alloy that can provide better corrosion resistance. Also, such a manganese-contained metal alloy can provide better extensibility in aiding hosel angle adjusting operation of the golf club head. Accordingly, the manganese-contained metal alloy can enhance the golf club head to have a greater toughness.
(4) Nickel is in a range of about 5.0% by weight to about 15.0% weight, preferably selecting from 7.0%, 9.0%, 11.0% or 13.0% by weight, while chromium is in a range of about 15.0% by weight to about 30.0% weight, preferably selecting from 17.0%, 19.0%, 21.0%, 24.0% or 27.0% by weight. Such a nickel-contained metal alloy can suppress formation of a pearlite structure that can improve corrosion resistance (i.e. resistance to pitting cavitations or uniform corrosion) of the metal alloy.
(5) Chromium is in a range of about 15.0% by weight to about 30.0% weight, preferably selecting from 17.0%, 19.0%, 21.0%, 24.0% or 27.0% by weight which can suppress formation of a pearlite structure. Meanwhile, chromium is a stabilized element formed in a ferrite phase that can aid in producing a complex structure of austenite and ferrite when the molten metal alloy is solidified. Such a chromium-contained structure of the ferrite phase exists a grain boundary limiting stress corrosion crack (SCC), thereby causing a pinning effect upon the diffusion of SCC. Consequently, the amount of chromium can affect the growth of SCC. In addition, there exists a change of a solidified columnar grain orientation in austenite phase to form ferrite phase by shifting a linear grain orientation to a cross grain orientation. In this way, the metal alloy can possess a higher degree of mechanical strength and a heterogeneous metal compatibility for the dilute ratio of high-strength steel (i.e. a matrix of martensite). Accordingly, the chromium-contained metal alloy is suitable for filler-free welding.
(6) Tungsten is in a range of about 5.0% by weight to about 15.0% weight, preferably selecting from 7.0%, 9.0%, 11.0% or 13.0% by weight. When the metal alloy is solidified, the ferrite phase may be precipitated in advance so that a coefficient of thermal expansion may be lower in high temperature. In this way, thermal stresses in the solidified metal alloy can therefore be avoided. In addition, the ferrite phase may melt a greater amount of solids of incidental impurities such that deficiencies of the gain boundary may be minimized. Also, the grain boundary of the tungsten-contained metal alloy may cause a pinning effect upon the diffusion of SCC, thereby stopping or overwhelming the growth of SCC. In addition, there also exists a change of a solidified columnar grain orientation in austenite phase to form ferrite phase by shifting a linear grain orientation to a cross grain orientation. In this way, the metal alloy can possess a higher degree of mechanical strength and a heterogeneous metal compatibility for the dilute ratio of high-strength steel (i.e. a matrix of martensite). Accordingly, the tungsten-contained metal alloy is also suitable for filler-free welding. Yet further, tungsten may increase a density of the metal alloy such that the tungsten-contained metal alloy can function as a weight material of the golf club head.
(7) Molybdenum is less than 1.0% by weight, preferably selecting from 0.9%, 0.8%, 0.7%, 0.6%, 0.5% or 0.4% by weight, so as to intensify and stabilize the structure of ferrite phase such that the molybdenum-contained metal alloy can reduce a possibility of thermal cracking in welding operation. Accordingly, the striking plate made from such a molybdenum-contained metal alloy can perform a greater heterogeneous metal weldability in a welding procedure.
(8) A small amount of impurities may be contained according to changes in processes, raw materials or both. In a preferred embodiment, copper is less than 1.0% by weight, preferably selecting from 0.9%, 0.8%, 0.7%, 0.6%, 0.5% or 0.4% by weight, so as to maintain the mechanical characteristics of the metal alloy of the present invention. Also, the copper-contained metal alloy can avoid the occurrence of embrittlement. In another preferred embodiment, sulfur is less than 0.04% by weight, preferably selecting from 0.03%, 0.02% or 0.01% by weight; and phosphorous is less than 0.04% by weight, preferably selecting from 0.03%, 0.02% or 0.01% by weight. The amount of sulfur and phosphorous must be lower than a predetermined value so as to avoid deficiencies of hot cracking in welding. Accordingly, the metal alloy can ensure the quality of welding. It will be apparent from the aforementioned discussions that ASTM 304 has a relatively low degree of tensile strength, wielding strength and hardness that may reduce mechanical strength and wear resistibility. Conversely, the metal alloy of the present invention contains a predetermined amount of tungsten and a small amount of incidental impurities (i.e. molybdenum, copper, phosphorous and sulfur) such that a ferrite structure is formed in the matrix of austenite phase. Advantageously, such a structure of the metal alloy possesses a high degree of mechanical characteristic and functions as a weighting material for the golf club head. Although the invention has been described in detail with reference to its presently preferred embodiment, it will be understood by one of ordinary skill in the art that various modifications can be made without departing from the spirit and the scope of the invention, as set forth in the appended claims.
