Methods for processing metal alloys

A method of processing a superaustenitic stainless steel alloy, the method comprising:

• heating a superaustenitic stainless steel alloy to an intermetallic phase precipitate dissolution temperature in an intermetallic phase precipitate dissolution temperature range, wherein the intermetallic phase precipitate dissolution temperature range is from a solvus temperature of an intermetallic phase precipitate of the superaustenitic stainless steel alloy to a temperature just below an incipient melting temperature of the superaustenitic stainless steel alloy;
• maintaining the superaustenitic stainless steel alloy in the intermetallic phase precipitate dissolution temperature range for a time sufficient to dissolve the intermetallic phase precipitate and to minimize grain growth in the superaustenitic stainless steel alloy;
• working the superaustenitic stainless steel alloy at a working temperature in a working temperature range from just above an apex temperature of a time-temperature-transformation curve for the intermetallic phase precipitate of the superaustenitic stainless steel alloy to just below the incipient melting temperature of the superaustenitic stainless steel alloy to provide a superaustenitic stainless steel article comprising a surface region and a central region, wherein the surface region comprises a mixture of recrystallized grains and unrecrystallized grains, and wherein the central region is fully recrystallized;
• transferring the superaustenitic stainless steel alloy article to a heating apparatus without letting the superaustenitic stainless steel article cool to the apex temperature of the time-temperature-transformation curve;
• heating the surface region of the superaustenitic stainless steel alloy article to a temperature in a temperature range of greater than 1900° F. to 2000° F.;
• maintaining the surface region of the superaustenitic stainless steel alloy article in the temperature range of greater than 1900° F. to 2000° F. for 1 minute to 30 minutes to recrystallize only grains in the surface region and provide a fully recrystallized surface region;
• and
• cooling the superaustenitic stainless steel alloy article to a cooling temperature at a cooling rate and to a temperature that inhibits formation of the intermetallic phase precipitate and minimizes grain growth;
• wherein after the cooling the superaustenitic stainless steel alloy article, an average grain size of the superaustenitic stainless steel alloy article is in an ASTM grain size number range of 00 to less than 3 wherein the cooling rate comprises a range from 0.3 Fahrenheit degrees per minute to 10 Fahrenheit degrees per minute.

A method of processing a superaustenitic stainless steel alloy, the method comprising:

• heating a superaustenitic stainless steel alloy to a temperature in a working temperature range, wherein the working temperature range is from a recrystallization temperature of the superaustenitic stainless steel alloy to a temperature below an incipient melting temperature of the superaustenitic stainless steel alloy;
• working the superaustenitic stainless steel alloy in the working temperature range to provide a superaustenitic stainless steel article comprising a surface region and a central region, wherein the surface region comprises a mixture of recrystallized grains and unrecrystallized grains, and wherein the central region is fully recrystallized;
• transferring the superaustenitic stainless steel alloy article to a heating apparatus within a time that does not exceed the time to an apex of a time-temperature-transformation curve for dissolution of an intermetallic sigma-phase precipitate of the superaustenitic stainless steel alloy;
• heating the surface region of the superaustenitic stainless steel alloy article to a temperature in a temperature range of greater than 2000° F. to 2150° F.;
• maintaining the surface region of the superaustenitic stainless steel alloy article in the temperature range of greater than 2000° F. to 2150° F. for 1 minute to 30 minutes to recrystallize only grains in the surface region and provide a fully recrystallized surface region;
• and
• cooling the superaustenitic stainless steel alloy article from the temperature range of greater than 2000° F. to 2150° F. at a cooling rate and to a temperature that minimizes grain growth in the superaustenitic stainless steel alloy article;
• wherein after the cooling the superaustenitic stainless steel alloy article, an average grain size of the superaustenitic stainless steel alloy article is in an ASTM grain size number range of 00 to less than 3 wherein the cooling rate comprises a range from 0.3 Fahrenheit degrees per minute to 10 Fahrenheit degrees per minute.

A method of processing a superaustenitic stainless steel alloy, the method comprising:

• heating a superaustenitic stainless steel alloy to an intermetallic phase precipitate dissolution temperature in an intermetallic phase precipitate dissolution temperature range, wherein the intermetallic phase precipitate dissolution temperature range is from a solvus temperature of an intermetallic phase precipitate of the superaustenitic stainless steel alloy to a temperature just below an incipient melting temperature of the superaustenitic stainless steel alloy;
• maintaining the superaustenitic stainless steel alloy in the intermetallic phase precipitate dissolution temperature range for a time sufficient to dissolve the intermetallic phase precipitate and to minimize grain growth in the superaustenitic stainless steel alloy;
• working the superaustenitic stainless steel alloy at a working temperature in a working temperature range from just above an apex temperature of a time-temperature-transformation curve for the intermetallic phase precipitate of the superaustenitic stainless steel alloy to just below the incipient melting temperature of the superaustenitic stainless steel alloy to provide a superaustenitic stainless steel article comprising a surface region and a central region, wherein the surface region comprises a mixture of recrystallized grains and unrecrystallized grains, and wherein the central region is fully recrystallized;
• transferring the superaustenitic stainless steel alloy article to a heating apparatus without letting the superaustenitic stainless steel article cool to the apex temperature of the time-temperature-transformation curve;
• heating the surface region of the superaustenitic stainless steel alloy article to a temperature in a temperature range of greater than 2000° F. to 2150° F.;
• maintaining the surface region of the superaustenitic stainless steel alloy article in the temperature range of greater than 2000° F. to 2150° F. for 1 minute to 30 minutes to recrystallize only grains in the surface region and provide a fully recrystallized surface region;
• and
• cooling the superaustenitic stainless steel alloy article to a cooling temperature at a cooling rate and to a temperature that inhibits formation of the intermetallic phase precipitate and minimizes grain growth;
• wherein after the cooling the superaustenitic stainless steel alloy article, an average grain size of the superaustenitic stainless steel alloy article is in an ASTM grain size number range of 00 to less than 3 wherein the cooling rate comprises a range from 0.3 Fahrenheit degrees per minute to 10 Fahrenheit degrees per minute.