Rock drill bit for percussive drilling and a rock drill bit button

Abstract

A button and a rock drill bit for percussive drilling including a bit head attached at an end of a drill element of a drilling assembly. The bit head has at a front end, as seen in the intended drilling direction, a plurality of buttons distributed over the bit head to engage material to be crushed. At least one of the buttons has a shank portion made of a substrate material of particles of a first material embedded in a binder phase. The first material is harder than the binder phase. The shank portion at least partially forms a bearing portion, the material of which is harder than the binder phase. At least one of the buttons is allowed to rotate about its own respective symmetry axis.

1 . A rock drill bit for percussive drilling comprising a bit head attached at an end of a drill element of a drilling assembly, said bit head having at a front end and as seen in an intended drilling direction a plurality of buttons distributed over said bit head to engage material to be crushed, at least one of said plurality of buttons having a shank portion of a substrate material including particles of a first material embedded in a binder phase, said first material being harder than the binder phase, wherein the shank portion at least partially forms a bearing portion, the bearing portion being made of a material that is harder than the binder phase, and wherein at least one of said plurality of buttons is allowed to rotate about its respective symmetry axis. 
     
     
         2 . A rock drill bit according to  claim 1 , wherein the material of the bearing portion is substantially homogenous. 
     
     
         3 . A rock drill bit according to  claim 1 , wherein the bearing portion comprises a material generally free from particles that are harder than the surrounding material. 
     
     
         4 . A rock drill bit according to  claim 1 , wherein the bearing portion at is at least partially coated with a barrier coating. 
     
     
         5 . A rock drill bit according to  claim 1 , wherein the bearing portion has a friction coefficient against steel which is less than 0.5, preferably in the range of 0.1-0.49, and/or most preferably in the range of 0.2-0.4. 
     
     
         6 . A rock drill bit according to  claim 1 , wherein the bearing portion has a microhardness (HV 0.05) of at least 3000, preferably in the range of 3000-3500, and/or most preferably in the range of 3100-3400. 
     
     
         7 . A rock drill bit according to anyone of  claims 1  to  6 ,  claim 1 , wherein the material of the bearing portion is selected from the group of titanium-aluminium nitride (TiAlN), aluminum-chromium nitride (AlCrN), titanium carbide (TiC), titanium nitride (TiN), chromium nitride (CrN), zirconium nitride (ZrN) and/or diamond coatings, or mixtures of such. 
     
     
         8 . A rock drill bit according to  claim 1 , wherein each of the plurality of buttons includes a button retaining means. 
     
     
         9 . A rock drill bit according to  claim 1 , wherein a base portion ( 44 ,  55 ) of at least one of the plurality of buttons rests against or contacts a bottom of a button hole to transfer impact forces to the button while allowing the base portion to move thereon when rotating. 
     
     
         10 . A rotatable rock drill bit button, comprising:
 a shank portion of a substrate material;   particles of a first material embedded in a binder phase, said first material being harder than the binder phase, wherein the shank portion at least partially forms a bearing portion, the bearing portion being made of a material that is harder than the binder phase.   
     
     
         11 . A rock drill bit button according to  claim 10 , wherein the material of the bearing portion is substantially homogenous. 
     
     
         12 . A rock drill bit button according to  claim 10 , wherein the bearing portion comprises a material generally free from particles that are harder than the surrounding material. 
     
     
         13 . A rock drill bit button according to  claim 10 , wherein the bearing portion has a friction coefficient against steel which is less than 0.5, preferably in the range of 0.1-0.5, and/or most preferably in the range of 0.2-0.4. 
     
     
         14 . A rock drill bit button according to  claim 10 , wherein the bearing portion has a microhardness (HV 0.05) of at least 3000, preferably in the range of 3000-3500, and/or most preferably in the range of 3100-3400. 
     
     
         15 . A rock drill bit button according to  claim 10 , wherein the bearing portion is selected from the group of titanium-aluminium nitride (TiAlN), aluminum-chromium nitride (AlCrN), titanium carbide (TiC), titanium nitride (TiN), chromium nitride (CrN), zirconium nitride (ZrN) and/or diamond coatings, or mixtures of such. 
     
     
         16 . A rock drill bit button according to  claim 10 , wherein each of the plurality of buttons includes a button retaining means. 
     
     
         17 . (canceled)