Cutting tool insert

Abstract

The present invention relates to a cutting tool insert for side and face milling of rolled low alloyed steel at low and at moderate cutting speeds comprising a cemented carbide body and a coating and a method for making same. The cemented carbide body comprises WC, from about 7.3 to about 7.9 wt-% Co and from about 1.0 to about 1.8 wt-% cubic carbides of Ta and Nb and a highly W-alloyed binder phase with a CW-ratio of from about 0.86 to about 0.94. The coating comprises: a first (innermost) layer of TiC x N y O z with a thickness of from about 0.1 to about 2 μm, and with equiaxed grains with size less than about 0.5 μm a layer of TiC x N y O z with a thickness of from about 2 to about 10 μm with columnar grains with a diameter of about less than about 5 μm a layer of TiC x N y O z with a thickness of 0.1-2 μm and with equiaxed or needlelike grains with size less than about 0.5 μm an outer layer of a smooth, textured, finegrained α-Al 2 O 3 layer with a thickness of from about 2 to about 10 μm. The invention also relates to the use of such a cutting tool insert for side and face milling of rolled low alloyed steel at low and moderate cutting speeds.

1 - 8 . (canceled)  
   
   
       9 . A method of manufacturing a metal workpiece with a cutting tool insert including a cemented carbide body and a coating, 
 said cemented carbide body comprising WC, from about 7.3 to about 7.9 wt-% Co and from about 1.0 to about 1.8 wt-% cubic carbides of Ta and Nb, a highly W-alloyed binder phase with a CW-ratio of from about 0.86 to about 0.94, and an edge radius of from about 20 to about 45 μm,    said coating comprising 
 a first (innermost) layer of TiC x N y O z  with a thickness of from about 0.1 to about 2 μm, and with equiaxed grains with size less than about 0.5 μm,  
 a layer of TiC x N y O z  with a thickness of from about 2 to about 10 μm with columnar grains with a diameter of less than about 5 μm,  
 a layer of TiC x N y O z  with a thickness of from about 0.1 to about 2 μm and with equiaxed or needlelike grains with size less than about 0.5 μm, and  
 an outer layer of a smooth, textured, finegrained α-Al 2 O 3  layer with a thickness of from about 2 to about 10 μm,  
   the method comprising: 
 side and face milling the metal workpiece at low or moderate cutting speeds.  
   
   
   
       10 . The method of  claim 9 , wherein the metal workpiece is formed of rolled low alloyed steel.  
   
   
       11 . The method of  claim 9 , wherein the metal workpiece is a plate.  
   
   
       12 . The method of  claim 11 , comprising manufacturing a tube from the milled plate.  
   
   
       13 . The method of claim  1 , wherein the α-Al 2 O 3  layer has a texture in the (104)-direction with a texture coefficient TC(104) larger than 1.3.  
   
   
       14 . The method of claim  1 , wherein the α-Al 2 O 3  layer has a texture in the (110)-direction with a texture coefficient TC(110) larger than 1.3.  
   
   
       15 . The method of claim  1 , wherein the cutting tool insert includes from about 0.5 to about 1.0 μm thick layer of TiN having a surface roughness R max <0.4 μm over a length of 10 μm and reduced in thickness over the edge line to from about 50 to about 90% of the thickness on the rake face.  
   
   
       16 . The method of claim  1 , wherein the cemented carbide includes from about 1.4 to about 1.7 wt-% carbides of Ta and Nb.  
   
   
       17 . A method of manufacturing a metal workpiece with a cutting tool insert, the cutting tool insert including a cemented carbide body and a coating, 
 wherein said cemented carbide body includes WC, from about 7.3 to about 7.9 wt-% Co and from about 1.0 to about 1.8 wt-% cubic carbides of Ta and Nb, a highly W-alloyed binder phase with a CW-ratio of from about 0.86 to about 0.94, and    wherein said coating includes 
 a first (innermost) layer of TiC x N y O z  with a thickness of from about 0.1 to about 2 μm, and with equiaxed grains with size less than about 0.5 μm,  
 a second layer of TiC x N y O z  with a thickness of from about 2 to about 10 μm with columnar grains with a diameter of less than about 5 μm,  
 a third layer of TiC x N y O z  with a thickness of from about 0.1 to about 2 μm and with equiaxed or needlelike grains with size less than about 0.5 μm,  
 an outer layer of a smooth, textured, finegrained α-Al 2 O 3  layer with a thickness of from about 2 to about 10 μm, and  
 a further layer of TiN having a surface roughness R max <0.4 μm over a length of 10 μm, having a thickness on a rake face of from about 0.5 to about 1.0 μm and having a reduced thickness over an edge line of from about 50 to about 90% of the thickness on the rake face,  
   the method comprising: 
 side and face milling the metal workpiece with the cutting tool insert.  
   
   
   
       18 . The method of  claim 17 , wherein side and face milling is at a cutting speed of less than about 500 m/min.  
   
   
       19 . The method of  claim 17 , wherein side and face milling is at a cutting speed of 1 about 300 m/min to about 500 m/min.  
   
   
       20 . The method of  claim 17 , wherein the cutting tool insert is a chamfering cutting tool insert.  
   
   
       21 . The method of  claim 17 , wherein the metal workpiece is formed of rolled low alloyed steel.  
   
   
       22 . The method of  claim 17 , wherein the metal workpiece is a plate and the method comprises manufacturing a tube from the milled plate.  
   
   
       23 . The method of  claim 17 , wherein the α-Al 2 O 3  layer has a texture in the (012)-direction with a texture coefficient TC(012) larger than 1.3.  
   
   
       24 . The method of  claim 17 , wherein the α-Al 2 O 3  layer has a texture in the (104)-direction with a texture coefficient TC(104) larger than 1.3.  
   
   
       25 . The method of  claim 17 , wherein the α-Al 2 O 3  layer has a texture in the (110)-direction with a texture coefficient TC(110) larger than 1.3.  
   
   
       26 . The method of  claim 17 , wherein the cemented carbide contains from about 1.4 to about 1.7 wt-% carbides of Ta and Nb.  
   
   
       27 . The method of  claim 17 , wherein the insert has an edge radius of from about 20 to about 45 μm before coating.  
   
   
       28 . The method of  claim 17 , wherein said edge radius is about 35 μm.  
   
   
       29 . The method of  claim 17 , wherein said cemented carbide body comprises about 7.6 wt-% Co.  
   
   
       30 . The method of  claim 17 , wherein an average grain size of the WC is in a range of from about 1.5 to 2.5 μm.  
   
   
       31 . The method of  claim 17 , wherein said CW-ratio is from about 0.86 to about 0.91.  
   
   
       32 . The method of  claim 17 , wherein the thickness of the second layer of TiC x N y O z  is from about 4 to about 7 μm.  
   
   
       33 . The method of  claim 17 , wherein the thickness of the outer layer of α-Al 2 O 3  is from about 3 to about 6 μm.  
   
   
       34 . The method of  claim 17 , wherein a texture coefficient of the α-Al 2 O 3  layer for the set of (012), (104) or (110) crystal planes is larger than 1.5.