CBN is a very hard tool material, most suitable for machining materials with hardness higher than HRC48. It has excellent high temperature hardness - up to 2000℃, and it also has higher impact strength and crushing resistance than ceramic knives.
CBN has low thermal conductivity and high compressive strength, withstanding the cutting heat generated by high cutting speed and negative rake Angle. The higher temperature in the cutting zone softens the workpiece material and contributes to chip formation.
What materials can CBN tool generally suitable for processing ?
1. High hardness cast iron
Such as high chromium cast iron, alloy cast iron, nickel hard cast iron, white cast iron all belong to high hardness cast iron, typical parts have rolls, industrial pumps and so on. For high hardness cast iron commonly used BN-K1 and BN-K10 material, the advantage is significant.
2. High hardness steel parts (hardness HRC45 and above)
Such as high manganese steel, high speed steel, hardened steel, etc., typical parts include mortar wall, high speed steel roller, hardened gear/gear shaft, bearing, ball screw, mold, etc. For high hardness steel parts commonly used CBN material for BN-S10, BN-S20, BN-S200, BN-H10, BN-H21 material.
3. Ordinary gray cast iron (HT150/200/250/300, etc.)
Such as engine cylinder block/cylinder head, brake disc, brake drum, pulley, clutch disc and so on are all gray cast iron parts. Commonly used CBN materials are BN-S300 and BNK30.
4. Other difficult-to-process materials
Such as powder metallurgy, high temperature alloy materials, and nickel base, iron base, cobalt base and other high hardness surfacing/spray welding/laser cladding/thermal spraying material workpiece. Common CBN materials are BN-S300, BN-S200, BDN80 and so on.
High quality cubic boron nitride (CBN) knife has two characteristics:
(1) Good impact resistance, especially in the field of rough machining, when used, the blade is not broken, not broken, which is the most basic guarantee of the safety of cubic boron nitride (CBN) tool.
CBN tool performance advantages ：
(1) With high hardness and wear resistance CBN single crystal microhardness of HV8000~9000, is currently known as the second highest hardness of material,CBN composite hardness is generally HV3000~5000.
(2) With high thermal stability and high temperature hardness CBN heat resistance up to 1400~1500, at 800 hardness Al2O3/TiC ceramics at room temperature hardness
(3) High chemical stability
(4) CBN has high oxidation resistance, at 1000 does not produce oxidation phenomenon, and iron materials in 1200~1300.
(5) Rough machining, should try to ensure a higher metal cutting rate and the necessary tool durability, so the general preference as much as possible to choose the cutting depth AP, followed by a larger feed f, and finally according to the tool durability requirements, determine the appropriate cutting speed Finishing, first of all should ensure the workpiece processing accuracy and surface quality requirements, so the general selection of smaller feed f and cutting depth AP, and as far as possible to choose higher cutting speed Vc.
CBN tool wear form
(1) continuous cutting wear form.
After the blade wear: the most common forms of wear and tear, is the tool and workpiece material of hard particles, due to friction wear will cause surface roughness and the dimensional accuracy of the workpiece processed super bad, need to replace new CBN inserts crater wear: surface occurred before the blade of the knife, is made between the cutting tool and workpiece material caused by chemical reaction Crescent depression wear will lead to chip treatment deterioration, affecting the quality of the machined surface, and too large crescent depression wear will weaken the cutting edge and may lead to fracture pressure surface wear: the main reason is because the cutting speed is too fast, the feed is too large, the tool Angle is too small and caused by pressure surface wear Boundary wear: the main reason is that the main deflection Angle is too large, the feed is too large, the cutting speed is too low to cause boundary wear (2)Broken cutting in the form of breakage edge: this is the CBN tool discontinuous processing of steel and cast iron, a common form of breakage it is produced on the cutting edge of a small gap, a few small gap on the blade or be broken off a small piece Such as micro collapse edge of the tool in the allowed wear limit can continue to cut, the need to replace the fragmentation :CBN tool continuous cutting high hardness materials or discontinuous cutting workpiece often occur in the form of damage, this is due to discontinuous cutting high hardness workpiece impact load is too large Cutting short time after the occurrence of early damage, although the cutting condition, the appropriate cutting after a long time, but no tool change in time, because of the cutting tool material fatigue occurs large flake fracture: milling of steel and cast iron face, often appear on the surface of the knife before the shells of spalling Appear this kind of situation, can reduce feed by raising the cutting speed, use a negative chamfer A blade with a passivated edge.
---EDITOR: Doris Hu
---POST: Doris Hu