Bi-metallic metal injection molded hand tool and manufacturing method

Abstract

An injection molded metallic hand tool having a body portion made of a first metal and an active surface portion made of higher hardness metal more capable of operating on the work subject. For example, in a pair of pliers, the serrated jaws have gripping teeth active surface portion is made from a durable, high strength metal such as tool steel alloy and the remainder or body portion is made from stainless steel alloy. The tool is made through a metal injection molding process wherein an amount of high hardness metal particles is first placed or injected into the corresponding tip portion of the mold, then higher strength metal particles are injected to fill the remainder of the mold. In this way, complex bi-metallic parts may be inexpensively injection molded. This also creates an alloy matrix bond between the two different metal portions.

What is claimed is:  
     
         1 . A process for forming a metal injection molded part which comprises: 
 selecting a first flowable amount of first metal particles in suspension, and a second flowable amount of second metal particles in suspension;    placing said first amount into a region of a mold;    injecting said second amount into said mold after said placing to form a compact; and    sintering said compact to form said part.    
     
     
         2 . The process of  claim 1 , wherein said first metal has a hardness greater than said second metal.  
     
     
         3 . The process of  claim 1 , wherein said process further comprises pressing to form said compact.  
     
     
         4 . The process of  claim 1 , wherein said injecting is performed at a pressure sufficient to form said compact.  
     
     
         5 . The process of  claim 1 , wherein said first metal comprises tool steel selected from the group consisting of: A, d, t, and m type tool steels and alloys thereof.  
     
     
         6 . The process of  claim 1 , wherein said first metal comprises a metal carbide.  
     
     
         7 . The process of  claim 1 , wherein said second metal comprises stainless steel and alloys thereof.  
     
     
         8 . The process of  claim 1 , wherein said sintering occurs at a temperature and for a time such that not all of said particles become fully molten.  
     
     
         9 . The process of  claim 1 , wherein said sintering comprises heating said compact through a heat profile; and terminally quenching said compact to adjust the hardness of the part.  
     
     
         10 . The process of  claim 1 , wherein said placing comprises coating a portion of said mold with said amount.  
     
     
         11 . The process of  claim 1 , wherein said placing comprises forming said first amount into a preformed coupon; and inserting said coupon into said mold.  
     
     
         12 . The process of  claim 1 , wherein said sintering results in said part having a density of between about 98% and 100% theoretical density.  
     
     
         13 . The process of  claim 1 , wherein said first and second metals are capable of forming a common alloy.  
     
     
         14 . A hand tool made from the process of  claim 1 .  
     
     
         15 . A method for forming an enhanced bond between two metallic structures comprises: 
 selecting an amount of first metal particles to form a first of said structures;    selecting an amount of second metal particles to form a second of said structures;    placing said first amount into a region of a mold;    placing said second amount into said mold in contact with said first amount along an interface;    heating said first and second amounts to a temperature sufficient to partially melt particles of both first and second metals and allow liquidus intermingling of said first and second metals along said interface to form a common alloy matrix thereby bonding said particles.    
     
     
         16 . A hand tool comprises: 
 a tip portion comprising particles of a first metal;    said tip portion being bonded at an interface zone to a body portion comprising particles of a second metal;    wherein said first and second particles are agglutinated by a metal matrix extending across said interface.    
     
     
         17 . The tool of  claim 16 , wherein said metal matrix comprises an alloy of said first and second metals.  
     
     
         18 . The tool of  claim 16 , wherein said first metal is harder than said second metal.  
     
     
         19 . The tool of  claim 16 , wherein said tool has a density of between about 98% and 100% theoretical density.  
     
     
         20 . The tool of  claim 16 , wherein said first metal comprises a tool steel selected from the group consisting of A, D, M, and T type tool steels and alloys thereof.  
     
     
         21 . The tool of  claim 16 , wherein said first metal comprises a refractory metal carbide.  
     
     
         22 . The tool of  claim 16 , wherein said second metal comprises stainless steel and alloys thereof.  
     
     
         23 . The tool of  claim 16 , wherein said first and second particles have substantially dissimilar crytaline orientations.  
     
     
         24 . A tool comprises: 
 a first portion made from sintered particles of a first metal;    a second portion made from sintered particles of a second metal different from said first metal;    wherein said first portion is bonded to said second portion by a metal matrix alloy formed by said first and second metals.    
     
     
         25 . The tool of  claim 24 , wherein each of said sintered particles maintains a unique crystalline structure relative to any adjacent particles.