Beta-Type Titanium Alloy

Abstract

Disclosed is a β-titanium alloy consisting of, in weight percent, 5-15% of V, 0.5-2.5% of Fe, 0.5-6% of Mo, 0.5-5% of Cr, 1.5-5% of Al, and the balance of Ti and impurities. When the weight % of V content is expressed as X V , the weight % of Fe content is expressed as X Fe , the weight % of Mo content is expressed as X Mo , and the weight % of Cr content is expressed as X Cr ; the value of X V +2.95X Fe +1.5X Mo +1.65 X Cr is 15-23%. Such a β-titanium alloy has excellent cold workability, while having higher strength than Ti-20V-4Al-1Sn β-titanium alloy.

1 . A β-type titanium alloy comprising, by mass %, V: 5 to 15%, Fe: 0.5 to 2.5%, Mo: 0.5 to 6% and Cr: 0.5 to 5%, wherein the value of X V +2.95X Fe +1.5X Mo +1.65X Cr  is from 15 to 23%, wherein X V  represents the mass % of the V, X Fe  represents the mass % of the Fe, X Mo  represents the mass % of the Mo and X Cr  represents the mass % of the Cr, and further comprising, by mass %, Al: 1.5 to 5%, wherein Ti and impurities constitute the residue.  
     
     
         2 . A β-type titanium alloy comprising, by mass %, V: 5 to 15%, Fe: 0.5 to 2.5%, Mo: 0.5 to 6% and Cr: 0.5 to 5%, wherein the value of X V +2.95X Fe +1.5X Mo +1.65X Cr  is from 15 to 23%, wherein X V  represents the mass % of the V, X Fe  represents the mass % of the Fe, X Mo  represents the mass % of the Mo and X Cr  represents the mass % of the Cr, and 
 further comprising, by mass %, Al: 1.5% to less than 5% and at least one of the group consisting of Sn: not more than 5% and Zr: not more than 5%, wherein the value of X Al +(X Sn /3)+(X Zr /6) is from 1.5 to 5, wherein X Al  represents the mass % of the Al, X Sn  represents the mass % of the Sn and X Zr  represents the mass % of the Zr, wherein Ti and impurities constitute the residue.    
     
     
         3 . A β-type titanium alloy comprising, by mass %, V: 5 to 15%, Fe: 0.5 to 2.5%, Mo: 0.5 to 6%, Cr: 0.5 to 5% and at least one selected from the group consisting of Nb: 0.5 to 2%, Ta: 0.5 to 2%, Ni: 0.25 to 1%, Mn: 0.25 to 1% and Co: 0.25 to 1%, wherein the value of X V +2.95X Fe +1.5X Mo +1.65X Cr +0.4X Nb +0.3X Ta +1.6X Ni +2.3X Mn +2.1X Co  is from 15 to 23%, wherein X V  represents the mass % of the V, X Fe  represents the mass % of the Fe, X Mo  represents the mass % of the Mo, X Cr  represents the mass % of the Cr, X Nb  represents the mass % of the Nb, X Ta  represents the mass % of the Ta, X Ni  represents the mass % of the Ni, X Mn  represents the mass % of the Mn and X Co  represents the mass % of the Co, and further comprising, by mass %, Al: 1.5 to 5%, wherein Ti and impurities constitute the residue.  
     
     
         4 . A β-type titanium alloy comprising, by mass %, V: 5 to 15%, Fe: 0.5 to 2.5%, Mo: 0.5 to 6%, Cr: 0.5 to 5% and at least one selected from the group consisting of Nb: 0.5 to 2%, Ta: 0.5 to 2%, Ni: 0.25 to 1%, Mn: 0.25 to 1% and Co: 0.25 to 1%, wherein the value of X V +2.95X Fe +1.5X Mo +1.65X Cr +0.4X Nb +0.3X Ta +1.6X Ni +2.3X Mn +2.1X Co  is from 15 to 23%, wherein X V  represents the mass % of the V, X Fe  represents the mass % of the Fe, X Mo  represents the mass % of the Mo, X Cr  represents the mass % of the Cr, X Nb  represents the mass % of the Nb, X Ta  represents the mass % of the Ta, X Ni  represents the mass % of the Ni, X Mn  represents the mass % of the Mn and X Co  represents the mass % of the Co, and 
 further comprising, by mass %, Al: 1.5% to less than 5% and at least one selected from the group consisting of Sn: not more than 5% and Zr: not more than 5%, wherein the value of X Al +(X Sn /3)+(X Zr /6) is from 1.5 to 5, wherein X Al  represents the mass % of the Al, X Sn  represents the mass % of the Sn and X Zr  represents the mass % of the Zr, and wherein Ti and impurities constitute the residue.    
     
     
         5 . A method for heat treatment of the β-type titanium alloy of  claim 1 , comprising heating a β-type titanium alloy to a temperature equal to or above the β transformation temperature, and then cooling the same at an average cooling rate of 1 to 100° C./sec to at least 500° C. or below.  
     
     
         6 . A method for heat treatment of the β-type titanium alloy of  claim 2 , comprising heating a β-type titanium alloy to a temperature equal to or above the β transformation temperature, and then cooling the same at an average cooling rate of 1 to 100° C./sec to at least 500° C. or below.  
     
     
         9 . A method for heat treatment of the β-type titanium alloy of  claim 3 , comprising heating a β-type titanium alloy to a temperature equal to or above the β transformation temperature, and then cooling the same at an average cooling rate of 1 to 100° C./sec to at least 500° C. or below.  
     
     
         10 . A method for heat treatment of the β-type titanium alloy of  claim 4 , comprising heating a β-type titanium alloy to a temperature equal to or above the β transformation temperature, and then cooling the same at an average cooling rate of 1 to 100° C./sec to at least 500° C. or below.