ULTRA-HIGH STRENGTH STAINLESS ALLOY STRIP, A METHOD OF MAKING SAME, AND A METHOD OF USING SAME FOR MAKING A GOLF CLUB HEAD

Description

BACKGROUND OF THE INVENTION:

FIELD OF THE INVENTION:

[0001] This invention relates to stainless steel strip material and in particular to a stainless steel strip article having very high tensile strength, a method of making same, and a method of using the strip material for making a golf club head.

DESCRIPTION OF THE RELATED ART:

[0002] Golf club manufacturers are constantly looking for a high strength faceplate material. Very high strength allows the faceplate section to be made thinner, and therefore lighter, which provides designers more leeway in club head design. In addition, corrosion-resistant materials are preferable to non-stainless materials because surface coatings or plating, which could be removed during use, are not required.

[0003] Current solutions to this problem include the use of standard PH stainless steel alloys such as the CUSTOM 455 alloy and newly designed stainless alloys such as the CUSTOM 465 and CUSTOM 475 alloys. However, the CUSTOM 455 and CUSTOM 465 alloys do not provide the strength levels desired in new club designs. The CUSTOM 475 alloy provides very high strength, but it is also highly alloyed, making it both expensive for the club manufacturer as well as less forgiving in the golf club manufacturing process.

[0004] In addition, many club heads are typically manufactured using a cast body with a faceplate. The cast body material is typically formed of a precipitation hardenable stainless steel such as 17-4 PH or 15-5 PH stainless steel. Golf clubs are typically manufactured by welding the faceplate to the cast body and then heat treating the entire assembly to develop final properties. The alloys typically used for the cast body of the club have solution temperatures of about 1900°F (1038°C), whereas the known faceplate materials have solution temperatures ranging from 1550°F to 1800°F (843°C to 982°C). This mismatch in heat treating temperatures results in either the club body, or the faceplate material, or possibly both, providing less than optimum properties in the as-heat treated condition after assembly of the club head. In addition, the CUSTOM 475 alloy often requires a different manufacturing process altogether, because the alloy cannot be re-solutioned after club head assembly.

BRIEF SUMMARY OF THE INVENTION:

[0005] The disadvantages of the known materials are overcome to a large degree by a stainless steel strip article according to this invention. In accordance with the one aspect of the present invention, there is provided a stainless steel strip article that is formed from a corrosion resistant alloy comprising, in weight percent, about:

C	0.03 max.
Mn	1.0 max.
Si	0.75 max.
P	0.040 max.
S	0.020 max.
Cr	10.9-11.1
Ni	10.9-11.1
Mo	0.9-1.1
Ti	1.5-1.6
Al	0.25 max.
Nb	0.7-0.8
Cu	1 max.
B	0.010 max.
N	0.030 max.

and the balance is iron and usual impurities. The elongated thin strip article provides a room temperature tensile strength of at least 280 ksi (1930.5 MPa) in the solution treated and age hardened condition.

[0006] In accordance with another aspect of this invention there is provided a method of making a thin strip article. The method comprises the steps of casting a corrosion resistant alloy having the weight percent composition set forth above to form an ingot. The ingot is hot worked to form an elongated strip material. The strip material is then heat treated under conditions of time and temperature to provide an ultimate tensile strength of at least about 280 ksi (1930.5 MPa) at room temperature. The heat treating step comprises the steps of: heating the elongated strip article at a temperature of 1038-1093°C; and then heating the elongated strip article at a temperature of 482°C to 510°C.

[0007] In accordance with a further aspect of this invention there is provided a method of making a golf club head. The method includes the step of casting a corrosion resistant alloy having the weight percent composition set forth above to form an ingot. The ingot is hot worked to form an elongated strip article which is then heat treated under conditions of time and temperature to benefit the machinability and processability of the strip material. The strip material is then machined to form a faceplate for a golf club head. The method includes the further step of forming a golf club head body from a corrosion resistant precipitation hardenable steel alloy. The faceplate is bonded to golf club head body. The assembly is then heat treated under conditions of time and temperature sufficient to provide a desired level of hardness and strength in the golf club head body and an ultimate tensile strength of at least about 280 ksi (1930.5 MPa) at room temperature in the faceplate. The heat treating step comprises the steps of: heating the elongated strip article at a temperature of 1038-1093°C; and then heating the elongated strip article at a temperature of 482°C to 510°C.

BRIEF DESCRIPTION OF THE DRAWING:

[0008] The drawing is a graph of tensile strength as a function of aging temperature.

DETAILED DESCRIPTION:

[0009] A preferred embodiment of the invention includes an elongated strip article having the following composition in weight percent:

C	0.03 max.
Mn	1.0 max.
Si	0.75 max.
P	0.040 max.
S	0.020 max.
Cr	10.9-11.1
Ni	10.9-11.1
Mo	0.9-1.1
Ti	1.5-1.6
Al	0.25 max.
Nb	0.7-0.8
Cu	1 max.
B	0.010 max.
N	0.030 max.

The balance is iron and the usual impurities.

[0010] The alloy composition is preferably melted using vacuum induction melting (VIM). The steel is cast into one or more ingot molds. For additional cleanness, the alloy is vacuum arc remelted (VAR) after the VIM step. After solidification, the alloy is formed into strip by intermediate pressing of the ingot to form a billet and then hot rolling the billet to form elongated strip. Alternatively, the strip material can be formed by hot rolling the ingot from a starting temperature of 1900°F to 2250°F (1038°C to 1232°C). The strip can be provided in the overaged condition by heating at 1100OF to 1350°F (593°C to 732°C) for about 2 to 8 hours and then cooling in air. Alternatively, and for better machinability and processability, the strip material is heated at 1900°F to 1950°F (1038°C to 1065°C) for 1 hour, cooled in air, refrigerated at -100°F (-73.3°C) for 8 hours, and then warmed in air to room temperature. Preferably, the strip material is cold rolled to final or near final thickness prior to being heat treated. The strip material according to this invention can be solution treated in a continuous furnace with times and temperatures adjusted accordingly. For the golf club application, the strip material is processed to a thickness of 0.02-0.16 inches (0.5-4 mm), preferably 0.10-0.12 inches (2.5-3.0 mm).

[0011] Unlike the known high strength stainless steel alloys such as the CUSTOM 475 stainless alloy, the alloy strip according to this invention can be double solution treated with no significant loss in properties, particularly no loss of strength. In other words, the stainless steel strip material of this invention can be provided in the solution treated plus refrigerated condition, processed into components, and then re-solutioned, re-refrigerated, and age hardened after being assembled into a golf club head to provide the desired high strength and hardness.

[0012] As an example of the elongated strip article according to the present invention, a small heat was melted and processed. The 400 lb (181.4 kg) heat was melted by VIM + VAR and cast as an 8-inch (20.3 cm) diameter ingot. The weight percent composition of the VAR ingot is given below in Table I. The balance of the alloy was iron and usual impurities.

Table I

C	Mn	Si	P	S	Cr	Ni	Mo	Ti	Cb	B	N	Ce
0.005	0.05	0.04	<0.005	<0.0005	11.05	11.02	1.01	1.56	0.79	0.0019	0.0016	0.001

[0013] The ingot was homogenized at about 2300°F (1260°C) for 16 hours, and then pressed to a 4-in x 8-in (10 cm x 20.3 cm) billet from a starting temperature of about 2000°F (1093°C). The billet was hot rolled to 7.5 in. wide x 0.15 in. thick (19 cm wide x 3.8 mm thick) strip from a starting temperature of about 2250°F (1232°C). The strip was then ground to 0.135 in. (3.4 mm) thick and then cold rolled to 0.1103 in. (2.8 mm) thick. The strip was given an overaging treatment by heating at about 1146°F (619°C) for 5.5 hours. After cooling to room temperature, the strip material was ground to a final thickness of 0.1083 in (2.75 mm).

[0014] Standard strip tensile blanks were rough cut in the longitudinal and transverse orientations from the overaged strip. Groups of the blanks were solution treated at 1850°F (1010°C), 1900°F (1038°C), 1950°F (1065°C), and 2000°F (1093°C), respectively, for 1 hour and air cooled. The solution treated blanks were deep chilled at -100°F (-73.3°C) for 8 hours and then warmed in air to room temperature. The blanks were then rough machined to provide a gage section about ½ inch wide x 2 inches long (1.27 cm wide x 5.08 cm long). Groups of the rough machined blanks from each solution treatment were aged at temperatures ranging from about 900°F (482°C) to about 975°F (524°C) for 4 hours and then air cooled. The test specimens were finish machined after aging and tested at room temperature.

[0015] The results of room temperature tensile and hardness testing are presented in Tables 2 - 4 below including the solution treatment temperature (Solution Temp.) and the aging temperature (Age Temp.) in °F (°C), the 0.2% offset yield strength (Y.S.) and ultimate tensile strength (U.T.S.) in ksi (MPa), and the Rockwell C-scale hardness (Hardness) as HRC.

Table 2

Solution Temp.	Age Temp.	Orient.	Y.S.	U.T.S.	% El.	Hardness (HRC)
1850°F (1010°C)	950°F (510°C)	L	258	266	-	52.0
			(1779)	(1834)
			258	267	-
			(1779)	(1841)
			258	268	-
			(1779)	(1848)
		T	260	272	-
			(1792)	(1875)
			260	273	-
			(1792)	(1882)
			245	272	-
			(1689)	(1875)
	975°F (524°C)	L	244	252	-	50.5
			(1682)	(1737)
			244	253	-
			(1682)	(1744)
			245	253	-
			(1689)	(1744)
		T	248	258	-
			(1710)	(1779)
			246	256	-
			(1696)	(1765)
			245	255	-
			(1689)	(1758)

Table 3

Solution Temp.	Age Temp.	Orient.	Y.S.	U.T.S.	% El.	Hardness (HRC)
1900°F	900°F	L	260	284	4.8	53.5
(1038°C)	(482°C)		(1792)	(1958)
			261	286	4.3
			(1799)	(1972)
			259	284	4.8
			(1785)	(19058)
		T	264	287	4.3
			(1820)	(1979)
			257	282	2.8
			(1772)	(1944)
			258	285	4.2
			(1779)	(1965)
	925°F (496°C)	L	259	282	4.0	53.5
			(1785)	(1944)
			257	281	4.2
			(1772)	(1937)
			256	281	4.1
			(1765)	(1937)
		T	247	285	3.9
			(1703)	(1965)
			260	285	4.1
			(1792)	(1965)
			257	285	4.2
			(1772)	(1965)
	950°F (510°C)	L	250	274	6.2	52.0
			(1723)	(1889)
			252	273	6.7
			(1737)	(1882)
			249	273	6.4
			(1716)	(1882)
		T	251	277	6.5
			(1730)	(1910)
			250	277	6.0
			(1723)	(1910)
			251	276	6.7
			(1730)	(1903)
	975°F (524°C)	L	234	258	7.3	50.5
			(1613)	(1779)
			235	256	7.1
			(1620)	(1765)
			235	259	6.9
			(1620)	(1785)
		T	243	264	6.8
			(1675)	(1820)
			240	261	6.6
			(1654)	(1799)
			242	263	6.6
			(1668)	(1813)

Table 4

Solution Temp.	Age Temp.	Orient.	Y.S.	U.T.S.	% El.	Hardness (HRC)
1950°F (1065°C)	900°F (482°C)	L	*	*	4.6	53.5
			*	*	4.1
			*	*	4.7
		T	*	*	5.4
			*	*	4.2
			*	*	4.8
	950°F (510°C)	L	*	*	5.3	52.5
			*	*	5.2
			*	*	4.3
		T	264	275	5.3
			(1820)	(1896)
			267	279	4.9
			(1841)	(1923)
			260	276	5.3
			(1792)	(1903)
2000°F (1093°C)	900°F (482°C)	L	248	282	5.9	53.5
			(1710)	(1944)
			253	283	5.0
			(1744)	(1951)
			255	282	5.5
			(1758)	(1944)
		T	261	286	4.6
			(1799)	(1972)
			258	291	5.1
			(1779)	(2006)
			260	287	4.7
			(1792)	(1979)
	950°F (510°C)	L	253	276	5.7	53.0
			(1744)	(1903)
			254	277	5.2
			(1751)	(1910)
			255	276	5.2
			(1758)	(1903)
		T	260	281	4.7
			(1792)	(1937)
			261	282	4.6
			(1799)	(1944)
			263	282	5.0
			(1813)	(1944)

* Strength data was lost for these samples. However, the test operator recalls that the U.T.S. for the H900 samples was above 280 ksi (1930.5 MPa) and that the U.T.S. for the H950 samples was slightly under 280 ksi (1930.5 MPa).

[0016] Metallographic analysis of the test specimens showed that the material solution treated at 1850°F (1038°C) and 1900°F (1038°C) had a grain size of about ASTM 8. The material solution treated at 1950°F (1065°) had a grain size of about ASTM 7-8. The material solution treated at 2000°F (1093°C) had a grain size of about ASTM 2-3. Here and throughout this application, the ASTM grain size means average grain size as determined in accordance with ASTM Standard Test Procedure E-112.

[0017] The results presented in Tables 2, 3, and 4 show that the preferred solution temperature is about 1900°F (1038°C) to about 1950°F (1065°C). Likewise, the preferred aging temperature is about 900°F to 925°F (482°C to 496°C) in order for the material to provide the desired 280 ksi (1930.5 MPa) U.T.S. A graph of U.T.S. versus solution and aging temperature combinations is shown in the drawing.

[0018] The data presented in the tables show that a strip article made from the alloy composition described in this application is capable of attaining an U.T.S. 280 ksi (1930.5 MPa) or higher. The strip material is much less heavily alloyed than other stainless compositions capable of that strength level, resulting in a lower alloy cost. In addition, the strip material is capable of being solution heat treated more than once without sacrificing strength or toughness properties. The strip material of this invention is preferably solution heat treated at a temperature in range of 1900-1950°F (1038-1065°C), making golf club faceplates of this composition fully compatible with the solution treating temperature for the precipitation hardenable stainless casting alloys most often used for the body of golf club head. Therefore, the faceplate and the club head body can be solution treated and age hardened in the assembled configuration to develop maximum hardness and strength, not only in the body of the club head, but also in the faceplate which makes contact with a golf ball.

Claims

1. An elongated, thin strip article that is formed from corrosion resistant alloy comprising, in weight percent:

C	0.03 max.
Mn	1.0 max.
Si	0.75 max.
P	0.040 max.
S	0.020 max.
Cr	10.9-11.1
Ni	10.9-11.1
Mo	0.9-1.1
Ti	1.5-1.6
Al	0.25 max.
Nb	0.7-0.8
Cu	1 max.
B	0.010 max.
N	0.030 max.

and the balance is iron and usual impurities, said elongated thin strip article having a room temperature tensile strength of at least 1930.5 MPa in the solution treated and age hardened condition.

2. An elongated strip article as claimed in Claim 1 wherein the strip has a thickness of 0.5 to 4 mm.

3. An elongated strip article as claimed in Claim 1 or Claim 2 wherein the alloy has an average grain size not greater than ASTM 7-8.

4. An elongated strip article as claimed in any of Claims 1-3 which has a hardness of 53-54 HRC.

5. A method of making the elongated thin strip article claimed in Claim 1 comprising the steps of
casting the corrosion resistant alloy to form an ingot;
mechanically working said ingot to form an elongated strip article; and then
heat treating said elongated strip article under conditions of time and temperature to provide an ultimate tensile strength of at least 1930.5 MPa at room temperature, said heat treating step comprising the steps of:

heating the elongated strip article at a temperature of 1038-1093°C; and then

heating the elongated strip article at a temperature of 482°C to 510°C.

6. A method as claimed in Claim 5 wherein the first heating step comprises heating the alloy at a temperature of 1038-1065°C.

7. A method as claimed in any of Claim 5 or 6 wherein the step of mechanically working the ingot comprises the steps of:

pressing the ingot to form a billet; and then

hot rolling the billet to form the elongated strip article.

8. A method as claimed in any of Claim 5 or 6 wherein the step of mechanically working the ingot comprises hot rolling the ingot to form the elongated strip article.

9. A method as claimed in Claim 7 or 8 wherein the step of mechanically working the ingot comprises cold rolling the elongated thin strip article to reduce its thickness to final or near final dimension.

10. A method as claimed in Claim 8 or 9 wherein the hot rolling step comprises heating the billet to 1038-1232°C.

11. A method of making a golf club head comprising the steps of
preparing an elongated thin strip article in accordance with the method of any of Claims 5-10;
cutting said elongated strip material to form a faceplate for a golf club head;
forming a golf club head body from a corrosion resistant precipitation hardenable steel alloy;
bonding said faceplate to said golf club head body to form a golf club head assembly; and then
heat treating said golf club head assembly under conditions of time and temperature to provide hardness and strength in the golf club head assembly and an ultimate tensile strength of at least 1930.5 MPa at room temperature in said faceplate, said heat treating step comprising the steps of:
heating the elongated strip article at a temperature of 1038-1093°C; and then
heating the elongated strip article at a temperature of 482°C to 510°C.

12. A method as claimed in Claim 11 wherein the step of heat treating the elongated thin strip article comprises the step of overaging the elongated thin strip article at 593-732°C.

Ansprüche

1. Länglicher, dünner Bandgegenstand, der aus korrosionsbeständiger Legierung gebildet ist, die Folgendes umfasst (in Gewichtsprozent):

C	max. 0,03
Mn	max. 1,0
Si	max. 0,75
P	max. 0,040
S	max. 0,020
Cr	10,9-11,1
Ni	10,9-11,1
Mo	0,9-1,1
Ti	1,5-1,6
Al	max. 0,25
Nb	0,7-0,8
Cu	max. 1
B	max. 0,010
N	max. 0,030

und Eisen und übliche Beimengungen machen den Rest aus, wobei der längliche, dünne Bandgegenstand im lösungsgeglühten und ausgehärteten Zustand bei Raumtemperatur eine Zugfestigkeit von mindestens 1930,5 MPa aufweist.

2. Länglicher Bandgegenstand nach Anspruch 1, wobei das Band eine Dicke von 0,5 bis 4 mm aufweist.

3. Länglicher Bandgegenstand nach Anspruch 1 oder 2, bei dem die Legierung eine durchschnittliche Korngröße von maximal 7 bis 8 nach ASTM aufweist.

4. Länglicher Bandgegenstand nach einem der Ansprüche 1 bis 3, der eine Härte von 53 bis 54 HRC aufweist.

5. Verfahren zum Herstellen des länglichen Bandgegenstands nach Anspruch 1, das folgende Schritte umfasst:

Gießen der korrosionsbeständigen Legierung zum Bilden eines Rohblocks,

mechanisches Bearbeiten des Rohblocks zum Bilden eines länglichen Bandgegenstands und danach

Wärmebehandeln des länglichen Bandgegenstands unter Zeit- und Temperaturbedingungen, die für eine letzendliche Zugfestigkeit von mindestens 1930,5 MPa bei Raumtemperatur sorgen, wobei die Wärmebehandlung folgende Schritte umfasst:

Erwärmen des länglichen Bandgegenstands bei einer Temperatur von 1038 bis 1093°C und danach

Erwärmen des länglichen Bandgegenstands bei einer Temperatur von 482 bis 510°C.

6. Verfahren nach Anspruch 5, bei dem der erste Erwärmungsschritt das Erwärmen der Legierung auf eine Temperatur von 1038 bis 1065°C umfasst.

7. Verfahren nach Anspruch 5 oder 6, bei dem das mechanische Bearbeiten des Rohblocks folgende Schritte umfasst:

Pressen des Rohblocks zum Bilden eines Knüppels und danach

Warmwalzen des Knüppels zum Bilden des länglichen Bandgegenstands.

8. Verfahren nach Anspruch 5 oder 6, bei dem das mechanische Bearbeiten des Rohblocks das Warmwalzen des Knüppels zum Bilden des länglichen Bandgegenstands umfasst.

9. Verfahren nach Anspruch 7 oder 8, bei dem das mechanische Bearbeiten des Rohblocks das Kaltwalzen des länglichen, dünnen Bandgegenstands zum Verringern seiner Dicke auf das Endmaß oder fast auf das Endmaß umfasst.

10. Verfahren nach Anspruch 8 oder 9, bei dem das Warmwalzen das Erwärmen des Knüppels auf 1038 bis 1232°C umfasst.

11. Verfahren zum Herstellen eines Golfschlägerkopfes, das folgende Schritte umfasst:

Fertigen eines länglichen, dünnen Bandgegenstands gemäß dem Verfahren nach einem der Ansprüche 5 bis 10,

Zuschneiden des länglichen Bandmaterials zum Bilden eines Schlägerblatts für einen Golfschlägerkopf,

Bilden des Körpers eines Golfschlägerkopfes aus einer korrosionsbeständigen, ausscheidungshärtbaren Stahllegierung,

Verbinden des Schlägerblatts mit dem Körper des Golfschlägerkopfes zum Bilden einer Golfschlägerkopf-Baugruppe und danach

Wärmebehandeln der Golfschlägerkopf-Baugruppe unter Zeit- und Temperaturbedingungen, die für Härte und Festigkeit der Golfschlägerkopf-Baugruppe und eine letzendliche Zugfestigkeit im Schlägerblatt von mindestens 1930,5 MPa bei Raumtemperatur sorgen, wobei die Wärmebehandlung folgende Schritte umfasst:

Erwärmen des länglichen Bandgegenstands bei einer Temperatur von 1038 bis 1093°C und danach

Erwärmen des länglichen Bandgegenstands bei einer Temperatur von 482 bis 510°C.

12. Verfahren nach Anspruch 11, bei dem das Wärmebehandeln des länglichen, dünnen Bandgegenstandes das Übervergüten des länglichen, dünnen Bandgegenstands bei 593 bis 732°C umfasst.

Revendications

1. Feuillard fin et allongé, formé d'un alliage résistant à la corrosion, comprenant en pourcentage pondéral :

C	0,03 max.
Mn	1,0 max.
Si	0,75 max.
P	0,040 max.
S	0,020 max.
Cr	10,9-11,1
Ni	10,9-11,1
Mo	0,9-1,1
Ti	1,5-1,6
Al	0,25 max.
Nb	0,7-0,8
Cu	1 max.
B	0,010 max.
N	0,030 max.

le reste étant du fer et des impuretés habituelles, ledit feuillard fin et allongé présentant une résistance à la traction à température ambiante d'au moins 1930,5 MPa dans un état mis en solution et durci par vieillissement.

2. Feuillard allongé selon la revendication 1, dans lequel le feuillard a une épaisseur comprise entre 0,5 et 4 mm.

3. Feuillard allongé selon la revendication 1 ou 2, dans lequel l'alliage a une granulométrie moyenne inférieure à 7-8 ASTM.

4. Feuillard allongé selon l'une quelconque des revendications 1 à 3, ayant une dureté de 53-54 HRC.

5. Procédé de fabrication du feuillard fin et allongé selon la revendication 1, comprenant les étapes suivantes :

moulage de l'alliage résistant à la corrosion afin de former un lingot ;

usinage mécanique dudit lingot afin de former un feuillard allongé ; puis traitement thermique dudit feuillard allongé dans des conditions temporelles et thermiques permettant de fournir une résistance à la traction finale d'au moins 1930,5 MPa à température ambiante, ladite étape de traitement thermique comprenant les étapes suivantes :

chauffage du feuillard allongé à une température comprise entre 1038 et 1093°C ; puis

chauffage du feuillard allongé à une température comprise entre 482°C et 510°C.

6. Procédé selon la revendication 5, dans lequel la première étape de chauffage comprend le chauffage de l'alliage à une température comprise entre 1038 et 1065°C.

7. Procédé selon l'une quelconque des revendications 5 ou 6, dans lequel l'étape d'usinage mécanique du lingot comprend les étapes suivantes :

compression du lingot pour former une billette ; puis

laminage à chaud de la billette pour former le feuillard allongé.

8. Procédé selon l'une quelconque des revendications 5 ou 6, dans lequel l'étape d'usinage mécanique du lingot comprend le laminage à chaud du lingot pour former le feuillard allongé.

9. Procédé selon la revendication 7 ou 8, dans lequel l'étape d'usinage mécanique du lingot comprend le laminage à froid du feuillard fin et allongé afin de réduire son épaisseur à une dimension finale ou quasi-finale.

10. Procédé selon la revendication 8 ou 9, dans lequel l'étape de laminage à chaud comprend le chauffage de la billette à 1038-1232°C.

11. Procédé de fabrication d'une tête de club de golf, comprenant les étapes suivantes :

préparation d'un feuillard fin et allongé conformément au procédé de l'une quelconque des revendications 5 à 10 ;

découpe dudit feuillard allongé afin de former une face pour une tête de club de golf ;

formage du corps de tête de club de golf à partir d'un alliage d'acier durcissable par précipitation et résistant à la corrosion ;

collage de ladite face audit corps de tête de club de golf afin de former un ensemble de tête de club de golf ; puis

traitement thermique dudit ensemble de tête de club de golf dans des conditions temporelles et thermiques permettant de fournir une dureté et une solidité à l'ensemble de tête de club de golf , ainsi qu'une résistance à la traction finale d'au moins 1930,5 MPa à température ambiante dans ladite face, ladite étape de traitement thermique comprenant les étapes suivantes :

chauffage du feuillard allongé à une température comprise entre 1038 et 1093°C ; puis

chauffage du feuillard allongé à une température comprise entre 482°C et 510°C.

12. Procédé selon la revendication 11, dans laquelle l'étape de traitement thermique du feuillard fin et allongé comprend l'étape de survieillissement du feuillard fin et allongé à 593-732°C.

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