Highly alloyed stainless steel forgings made without solution anneal

Abstract

The post-forging solution anneal step normally carried out on hot forgings made from highly alloyed metals can be eliminated while still avoiding the formation of deleterious intermetallic phases by adopting a number separate features in connection with the way the forging is made.

1 . In a continuous, automatic process for making multiple hot forgings in series from multiple billets made from a highly-alloyed metal, the improvement wherein the hot forgings are made without subjecting these hot forgings to post-forging solution anneal. 
     
     
         2 . The process of  claim 1 , wherein only those billets which are essentially free of deleterious intermetallic phases are selected as the billets to be forged. 
     
     
         3 . The process of  claim 1 , wherein the hot forgings are made by a forging process including a heating step in which the billets are heated by means of resistance or induction heating from below the critical temperature range of the highly-alloyed metal to a forging temperature above this critical temperature range. 
     
     
         4 . The process of  claim 3 , wherein the heating step is carried out by (a) automatically discharging to waste any billet whose heating rate fails to achieve a predetermined minimum. 
     
     
         5 . The process of  claim 4 , wherein the heating step is further carried out by (b) automatically discharging to waste any billet whose temperature at the end of this step is below a predetermined minimum or above a predetermined maximum. 
     
     
         6 . The process of  claim 4 , wherein the heating step is further carried out by (c) automatically discharging to waste any billet in which the difference between the measured temperature of the side wall of the billet at the end of this step and the measured temperature of the front or rear face of the billet at the end of this step exceeds a predetermined maximum. 
     
     
         7 . The process of  claim 4 , wherein the heating step is further carried out by (d) heating the billet above its critical temperature range long enough to redissolve any intermetallic phases that may be present. 
     
     
         8 . The process of  claim 4 , wherein the heating step is further carried out by discharging to waste all billets whose actual temperature at the end of the heating step exceeds a predetermined maximum, or by discharging to waste all billets which are heated in the heating step for a holding time which exceeds a predetermined maximum. 
     
     
         9 . The process of  claim 1 , wherein the hot forgings are made by a forging process which includes (1) a heating step in which the billets are heated from below the critical temperature range of the highly-alloyed metal to a forging temperature above this critical temperature range rapidly enough so that the heated billets obtained are essentially free of deleterious intermetallic phases, (2) a forging step in which the billets are forged into forgings, and (3) a cooling step in which the forgings so made are cooled from above their critical temperature range to below their critical temperature range. 
     
     
         10 . The process of  claim 9 , wherein step (1) is carried out in a heater, wherein step (3) is carried out by contact of the forging so made with water or other cooling liquid, and further wherein step (2) is carried out by automatically discharging to waste any forging whose forging step is carried out for a period of time which is longer than a predetermined maximum, this period of time beginning when the billet is removed from its heater in step (1) and ending when the forging so made is contacted with water or other cooling liquid in step (3). 
     
     
         11 . The process of  claim 9 , wherein step (2) is carried out rapidly enough so that the forgings obtained are essentially free of deleterious intermetallic phases, and further wherein step (3) is carried out rapidly enough so that the cooled forgings obtained are essentially free of deleterious intermetallic phases. 
     
     
         12 . The process of  claim 11 , wherein step (1) is carried out in a heater, wherein step (3) is carried out by contact of the forging so made with water or other cooling liquid, and further wherein step (2) is carried out by automatically discharging to waste any forging whose forging step is carried out for a period of time which is longer than a predetermined maximum, this period of time beginning when the billet is removed from its heater in step (1) and ending when the forging so made is contacted with water or other cooling liquid in step (3). 
     
     
         13 . The process of  claim 9 , wherein cooling is carried out by immersing the forging so made in water or other cooling liquid, said process further comprising automatically discharging to waste any forging which is immersed in water or other cooling liquid having a temperature exceeding a predetermined maximum. 
     
     
         14 . The process of  claim 1 , wherein the highly-alloyed metal has a CP value of at least 500, wherein the CP value of the alloy is given by the following formula:
   CP=20×% Cr+0.3×% Ni+30×% Si+40×% Mo+5×% W+10×% Mn+50×% C−200×% N.
   
     
     
         15 . The process of  claim 14 , wherein the highly-alloyed metal is a superstainless steel containing about 19 to 26 wt. % Cr and 3 to 8 wt. % Mo. 
     
     
         16 . The process of  claim 14 , wherein the highly-alloyed metal is a nickel based alloy containing at least about 4 wt. % Mo. 
     
     
         17 . In a process for shaping a hot forging which is made from a highly-alloyed metal into a metal part which is useful in one or more applications including chemical processing, scrubbers, pulp mills, bleach washers, food processing and oil field piping, the improvement comprising shaping the hot forging into the metal part without subjecting this hot forging to post-forging solution anneal. 
     
     
         18 . The process of  claim 17 , wherein shaping is accomplished by machining the hot forging. 
     
     
         19 . The process of  claim 17 , wherein the highly-alloyed metal has a CP value of at least 500, wherein the CP value of the alloy is given by the following formula:
   CP=20×% Cr+0.3×% Ni+30×% Si+40×% Mo+5×% W+10×% Mn+50×% C−200×% N.
   
     
     
         20 . A process for making a metal part from a hot forging of a highly-alloyed metal, the process comprising
 (a) heating a billet of a highly-alloyed metal up to its forging temperature in a manner so that the heated billet is essentially free of intermetallic phases,   (b) forging the billet in a manner so that the forging obtained is essentially free of intermetallic phases,   (c) cooling the forging so obtained to below its critical temperature range CTR rapidly enough so that the forging obtained is essentially free of intermetallic phases, and   (d) forming the metal part by machining the hot forging of step (c) without subjecting this hot forging to post-forging solution anneal.   
     
     
         21 . The process of  claim 20 , wherein the highly-alloyed metal has a CP value of at least 500, wherein the CP value of the alloy is given by the following formula:
   CP=20×% Cr+0.3×% Ni+30×% Si+40×% Mo+5×% W+10×% Mn+50×% C−200×% N.
   
     
     
         22 . The product of the process of  claim 21 . 
     
     
         23 . In a metal part which is (a) made by shaping a hot forging of a highly-alloyed metal and (b) useful in one or more applications including chemical processing, scrubbers, pulp mills, bleach washers, food processing and oil field piping, the improvement wherein the metal part is made without subjecting the hot forging to post-forging solution anneal. 
     
     
         24 . The metal part of  claim 23 , wherein the metal part is made by machining the hot forging. 
     
     
         25 . The metal part of  claim 24 , wherein the highly-alloyed metal has a CP value of at least 500, wherein the CP value of the alloy is given by the following formula:
   CP=20×% Cr+0.3×% Ni+30×% Si+40×% Mo+5×% W+10×% Mn+50×% C−200×% N.
   
     
     
         26 . A metal part made by machining a hot forging made by the process of  claim 1 .