Cutter insert gum modification method and apparatus

Abstract

A method and apparatus for treating a cutter ring adapted to be used in tunnel boring operations. An initial cutter member blank is formed and heat treats the cutter ring prior to a cladding process. An alloy is applied to the surface of the cutter blank adjacent to the cutting elements by the cladding process whereby the cutting elements have insufficient heat transfer from the cladding process to reduce their hardness properties, and in one form a fabric material defines the region for the exterior hard surface.

1 . A method of producing a cutter ring, the method comprising:
 a. applying a pliable pre-hardened material to an outer surface of cutter blank, where the pliable pre-hardened material is comprised of a hard facing alloy and has surfaces defining openings therein,   b. applying sufficient heat positioning the cutter blank with the pliable pre-hardened material so as to melt the hard facing alloy of the pliable pre-hardened material to bind to the outer surface of the cutter blank to form a hardened surface,   c. identifying the regions of the cutter blank of the services defining openings of the pliable pre-hardened material and excavating material from the cutter blank to form a cavity adjacent to the outer surface of the hardened surface,   d. inserting cutting elements into the cavities and fixedly manning the cutting elements therein,   e. whereas the cutting elements have a hardness higher than that of the surrounding gum region beneath hardened surface.   
     
     
         2 . The method as recited in  claim 1  where the cutter blank is placed in a furnace and heated above the melting point of the hard-facing alloy and where the molten alloy wicks down into the layer of tungsten carbide particles, metallurgically bonding the hard particles to the cutter blank. 
     
     
         3 . The method as recited in  claim 1  whereby the method deposit's material is greater than 0.030 of an inch. 
     
     
         4 . The method as recited in  claim 1  whereby the cutting elements are comprised of a tungsten carbide material. 
     
     
         5 . The method as recited in  claim 1  where the Rockwell hardness of the cutter ring is between 32 and 44 when forming the plurality of cavities in the cutter blank. 
     
     
         6 . The method as recited in  claim 5  whereby the cutting elements are press fit into the cavity regions. 
     
     
         7 . A cutter head for a tunnel boring machine comprising:
 a. a perimeter portion with a plurality of cavities with cutting elements fixedly positioned in said cavities,   b. the ring having a gum region engaging said cutting elements, the gum region comprising:
 i. a surface region, 
 ii a hardened layer cladded to the surface region where the hardened layer is cladded to the surface region when the cutter ring is preheated above 350° F. and heat is applied to an alloy material to form the hardened layer whereby the cutting elements are not effected by the heat is applied to an alloy powder and the metallurgical hardness properties of the cutting elements is preserved whereby hardened elements of the hardened layer and the cutting elements have a Rockwell hardness at least 20 units greater than the gum region. 
   
     
     
         8 . The cutter head as recited in  claim 7  where the temperature of the cutting elements during the heat transfer to the alloy powder does not increase above 900° F. 
     
     
         9 . The cutter head as recited in  claim 7  where the Rockwell hardness of the cutting elements in the hardened layer is at least 30 units greater than the gum region. 
     
     
         10 . The cutter head as recited in  claim 9  where the surface region is comprised of a nickel matrix composition mixed with a tungsten carbide material. 
     
     
         11 . The cutter head as recited in  claim 7  where the hardened layer is not more than ⅛ of an inch in thickness. 
     
     
         12 . The cutter head as recited in  claim 10  where the Rockwell hardness of the cutter ring is not more than 44 when forming the plurality of radially extending cavities in the perimeter region. 
     
     
         13 . The cutter head as recited in  claim 10  where the Rockwell hardness of the cutter ring is less than 36. 
     
     
         14 . The cutter head as recited in  claim 10  where the cutting elements are placed in the radially extending cavities after the hardened layer is formed. 
     
     
         15 . The cutter head as recited in  claim 10  where the cutting elements are placed in the radially extending cavities prior to the application of alloy powder to form the hardened layer. 
     
     
         16 . The cutter head as recited in  claim 7  where the cutting elements are scraper elements. 
     
     
         17 . A method for forming a cutting tool for a tunnel boring machine comprising the steps of:
 a. retrieving a cutter blank comprised of a base material with an outer surface and having a first hardness value,   b. providing openings within the cutter blanks   c. positioning a substrate material on the cutter blank where the substrate material has a surface defining openings thereupon, positioning the substrate material in a manner so as to have the openings substantially correlate in position with the openings of the cutter blank,   d. providing heat to the substrate material so as to create a hard-facing alloy positioned on the outer surface of the cutter blank,   e. press fitting cutter bits into the openings of the cutter blank such that the cutter bits are rigidly mounted therein.   
     
     
         18 . The method as recited in  claim 17  where the hard facing alloy wicks into the cutter blank, providing tungsten carbide particles to metallurgically bond thereto. 
     
     
         19 . The method as recited in  claim 18  where the hard-facing alloy is heeded by way of a laser cladding process. 
     
     
         20 . The method as recited in  claim 19  where the cutter bits are inserted into the cutter blank prior to the laser cladding being applied to the substrate material. 
     
     
         21 . The method as recited in  claim 17  where heat is applied to the substrate material to metallurgically bond the substrate material to the cutter blank. 
     
     
         22 . The method as recited in  claim 21  where after the substrate material is bonded to the cutter blank, a cutter insert is fitted to the openings defined in the cutter blank and having the substrate material positioned around the cutter bits. 
     
     
         23 . The method as recited in  claim 17  where the cutter bit is a scraper blade. 
     
     
         24 . The method as recited in  claim 23  where the combination of the cutter blank, the cutter bits and the hardened substrate material forms a cutter head which is bidirectional.