Powder metallurgical processing of high-manganese steels into parts

Abstract

Although high-manganese steels may have desirable mechanical strength and corrosion resistance, machining and casting can be difficult. Alternatively, high-manganese steel parts may be fabricated to near-net shape parts using powder metallurgical processing, such as hot pressing and powder injection molding, thereby significantly minimizing or eliminating the need for further machining of fabricated parts. Hot pressing processes may comprise: loading a container with a plurality of particulates comprising a high-manganese steel; establishing a reduced pressure state in the container after loading the container with the plurality of particulates, and sealing the container to maintain the reduced pressure state therein and to afford a sealed container; placing the sealed container in a pressure vessel; heating the pressure vessel at a predetermined temperature while applying a predetermined pressure isostatically to an exterior surface of the sealed container with a pressurizing gas to consolidate the plurality of particulates into a densified part having a near-net shape; and removing the sealed container to expose a surface of the densified part.

What is claimed is: 
     
         1 . A process comprising:
 providing a plurality of particulates comprising a high-manganese steel;   loading a container with the plurality of particulates, the container having an internal surface formed in a near-net shape of a part;   establishing a reduced pressure state in the container after loading the container with the plurality of particulates, and sealing the container to maintain the reduced pressure state therein, thereby affording a sealed container;   placing the sealed container in a pressure vessel;   heating the pressure vessel at a predetermined temperature while applying a predetermined pressure isostatically to an exterior surface of the sealed container with a pressurizing gas;
 wherein the predetermined temperature and the predetermined pressure in combination are sufficient to consolidate the plurality of particulates to form a densified part having the near-net shape; and 
   removing the sealed container to expose a surface of the densified part.   
     
     
         2 . The process of  claim 1 , wherein removing the sealed container comprises a pickling treatment that dissolves the container. 
     
     
         3 . The process of  claim 1 , wherein removing the sealed container comprises a machining operation that disassembles the container. 
     
     
         4 . The process of  claim 1 , wherein sealing the container comprises a seal welding operation. 
     
     
         5 . The process of  claim 1 , wherein the densified part is a pipeline connector. 
     
     
         6 . The process of  claim 5 , wherein the densified part is a weld neck pipe flange. 
     
     
         7 . The process of  claim 5 , wherein the densified part is a flanged pipe elbow or a flanged pipe T. 
     
     
         8 . The process of  claim 1 , wherein the predetermined temperature does not lead to formation of a liquid phase in the container. 
     
     
         9 . The process of  claim 1 , further comprising:
 providing a second plurality of particulates comprising a second high-manganese steel with a different composition from the high-manganese steel or a steel composition that is not a high-manganese steel;
 wherein the loading the container with the plurality of particulates comprises disposing the plurality of particulates of the high-manganese steel in a first location of the container and disposing plurality of particulates of the second high-manganese steel or the steel composition that is not a high-manganese steel in a second location of the container. 
   
     
     
         10 . The process of  claim 9 , wherein the second location of the container is in a location of the container that forms the internal surface of the near-net shape part. 
     
     
         11 . A process comprising:
 providing a plurality of particulates comprising a high-manganese steel;   introducing the plurality of particulates and a binder material into a mold having an internal surface formed in a near-net shape of a part;   setting the binder material to form a first intermediate part in which the plurality of particulates remain in a substantially unconsolidated state;   removing the first intermediate part from the mold;   heating the first intermediate part at a first temperature sufficient to remove the binder material while leaving the plurality of particulates in the substantially unconsolidated state, thereby forming a second intermediate part; and   heating the second intermediate part at a second temperature sufficient to consolidate the plurality of particulates together to form a densified part.   
     
     
         12 . The process of  claim 11 , wherein the binder material comprises a polymer or a wax. 
     
     
         13 . The process of  claim 11 , wherein introducing the plurality of particulates and the binder material into the mold takes place by injection molding. 
     
     
         14 . The process of  claim 11 , wherein the plurality of particulates and the binder material are premixed before being introduced to the mold. 
     
     
         15 . The process of  claim 11 , wherein the plurality of particulates and the binder material are separately introduced into the mold. 
     
     
         16 . The process of  claim 15 , wherein the plurality of particulates and the binder material are disposed heterogeneously in the first intermediate part. 
     
     
         17 . The process of  claim 11 , wherein the densified part is a pipeline connector. 
     
     
         18 . The process of  claim 17 , wherein the densified part is a weld neck pipe flange. 
     
     
         19 . The process of  claim 17 , wherein the densified part is a flanged pipe elbow or a flanged pipe T. 
     
     
         20 . The process of  claim 11 , wherein the second temperature does not lead to formation of a liquid phase in the container.