Maraging steel golf club head

Abstract

The invention concerns a golf club head whereof the strike surface zone at least is made of maraging steel essentially consisting of 6.0 to 9.0 wt. % of nickel, 11.0 to 15.0 wt. % of chromium, 0.1 to 0.3 wt. % of titanium, 0.2 to 0.3 wt. % of beryllium, the rest being iron and impurities resulting from production, the temperature of the martensitic phase being M s ≧130 ° C. and the ferrite content being adjusted at C Ferrit<3%. Said maraging steel typically exhibits tensile strength R m of about 2800 MPa, yield strength R p0.2 of about 2600 MPa, Vickers hardness>800 and alternating flexure strength o′ bw of about 1550 MPa.

1 . Golf club head that is at least partly made of a corrosion-free, precipitation-hardened, maraging steel with a martensite temperature M s ≧130° C., a ferrite content  C Ferrite<3%, wherein the maraging steel essentially consists of 6.0 to 9.0 wt. % nickel, 11.0 to 15.0 wt. % chromium, 0.1 to 0.3 wt. % titanium, 0.2 to 0.3 wt. % beryllium, the rest being iron together with unavoidable impurities, and wherein maraging steel in accordance with the invention exhibits a tensile strength R m >2000 MPa and a yield strength R p0.2 >1900 MPa.  
   
   
       2 . Golf club head in accordance with  claim 1  wherein up to 35% of the chromium content can be replaced by molybdenum and/or tungsten.  
   
   
       3 . Golf club head in accordance with  claim 2  wherein the maraging steel essentially consists of 8.0 wt. % nickel, 13.0 wt. % chromium, 0.2 wt. % titanium, 0.25 wt. % beryllium, 1.0 wt. % molybdenum, the rest being iron together with unavoidable impurities.  
   
   
       4 . Golf club head in accordance with  claim 1  wherein the maraging steel comprises up to 0.1 wt. % cerium or cerium misch metal as a deoxidizing agent.  
   
   
       5 . Golf club head in accordance with  claim 1  wherein the maraging steel can comprise at least one of the elements manganese, niobium or silicon in individual proportions of less than 0.5 wt. %.  
   
   
       6 . Golf club head in accordance with  claim 1  wherein the maraging steel comprises at least one of the elements C, N, S, P, B, H, or O in individual proportions of less than 0.1 wt. %.  
   
   
       7 . Golf club head in accordance with  claim 5  wherein the maraging steel exhibits a martensite temperature M s =[629.45−6.8(Cr+1.2 Mo+0.6 W)−24.5(Ni+0.15 Co)−13.2 Mn−11.2 Si−670(C+N)] ° C.  
   
   
       8 . Golf club head in accordance with  claim 5  wherein the spring steel exhibits a ferrite content  C Ferrite=[11.8 Si+7.92(Cr+Mo+0.5 W)+15.84 Ti−2.91 Mn−5.83(Ni+0.3 Co)−174.9(C+N)−77.08] wt. %.  
   
   
       9 . Golf club head in accordance with  claim 1  wherein the maraging steel exhibits a tensile strength R m >2400 MPa.  
   
   
       10 . Golf club head in accordance with  claim 9  wherein the maraging steel exhibits a tensile strength R m  of approximately 2800 MPa.  
   
   
       11 . Golf club head in accordance with  claim 1  wherein the maraging steel exhibits a yield strength R p0.2 >2100 MPa.  
   
   
       12 . Golf club head in accordance with  claim 11  wherein the maraging steel exhibits a yield strength R p0.2  of approximately 2500 MPa.  
   
   
       13 . Golf club head in accordance with  claim 1  wherein the maraging steel exhibits an alternating flexure strength  o′ bw of approximately 1350 MPa.  
   
   
       14 . Golf club head in accordance with  claim 13  wherein the maraging steel exhibits an alternating flexure strength  o′ bw of approximately 1550 MPa.  
   
   
       15 . Golf club head in accordance with  claim 1  wherein the maraging steel exhibits a Vickers hardness HV>700.  
   
   
       16 . Golf club head in accordance with  claim 15  wherein the maraging steel exhibits a Vickers hardness HV>800.  
   
   
       17 . Golf club head in accordance with  claim 1  wherein the maraging steel exhibits a maximal storable energy of more then 30 MPa.  
   
   
       18 . Golf club head in accordance with  claim 17  wherein the maraging steel exhibits a maximal storable energy of approximately 40 MPa.  
   
   
       19 . Process for the manufacturing of maraging steel for a golf club head in accordance with  claim 1  comprising the following process steps: 
 a) Melting the alloy under vacuum or protective gas followed by casting into an ingot;    b) Hot forming the ingot into a strip at 900° C.≦T 1 ≦1150° C.;    c) Carrying out a solution annealing of the strip at 850° C.≦T 2 ≦1100° C.;    d) Cooling the strip to a temperature T 3 ≦300° C.;    e) Grinding the strip to remove the beryllium-depleted edge zone;    f) Cold forming the strip with a cold forming degree that is greater than or equal to 60%;    g) First heat treatment of the strip at 400° C.≦T 4 ≦550° C. for a duration of 1 hour to 10 hours.    
   
   
       20 . Process in accordance with  claim 17  comprising the following additional process step: 
 h) Second heat treatment of the strip at 300° C.≦T 5 ≦470° C. for a duration of ten to 100 hours.