Hard turning slewing bearing instead of grinding CBN inserts from Halnn Superhard Materials
The hardness of Slewing bearing after quenching can arrive HRC55~62,The hardened layer usually is 3~5mm,Slewing bearing and wind power wheel bearing ring which materials are 50Mn or 42CrMo,and turning instead of grinding process usually use dry cutting with vertical lathe.
Hard turning slewing bearing process raised large challenge on the toughness and wear-resistance of hard cutting tools because of the large machining allowance and strictly requirements on machining accuracy when hard turning rolls path and bearing surface .
Cubic boron nitride (CBN) is the most hard cutting tools materials in current ferrous metal which used for machining cutting tools.CBN is already well known as hard cutting inserts after heat-treatment,and it usually only use on turning small allowance instead of grinding after quenching because of brittleness limit.
CBN inserts performance requirement for hard turning slewing bearings
The machining allowance of hard turning slewing bearings will be reserved depending on previous heat-treatment process and quenching deformation. Usually the allowance is 2~6mm when hard turning slewing bearings after quenching; hard cutting inserts need excellent impact toughness.
Thus it can be seen that the difficult point on hard cutting slewing inner and outer bearings is CBN inserts need high toughness and excellent wear-resistance and stability because finish turning slewing ring roller path after quenching require good smooth finish and dimension stability.So people who is in slewing wheel bearings industry will complain that CBN inserts has poor smooth finish because of low CBN inserts hardness, and CBN inserts is too Brittle to chipping ,especially for discontinuous surface cutting part.
Specific to hard turning large allowance in the slewing bearings,Halnn research new grade cbn inserts which can be used for turning instead of grinding.
Halnn superhard material developed non-metal adhesive BN-S20 grade CBN inserts, which specific to the high performance requirement for CBN inserts on hard turning slewing bearing.
As the only non-metal adhesive CBN inserts,BN-S20 grade inserts not only ensure CBN inserts toughness ,but also avoid the lifetime reduction which caused by metal adhesive premature softening after CBN inserts was heating .BN-S20 grade cutting inserts suit high speed finishing and tough turning high hardness large-scale workpiece after quenching, which hardness is HRC98.5;and the Machinable Hardness range after heat treatment :HRC45-HRC79.
Halnn BN-S20 grade CBN inserts also suit for hard turning with long time and large allowance or turning instead of grinding process.
Application case as follows:
Hard Turning bearings rings with BN-S20 grade CBN inserts,
Working allowance after quenching:5mm,
Linear speed:90-150m/min
The roughness and the channel surface roughness of finish turning that work piece after quenching can arrive Ra0.3μm.
All can satisfy turning instead of grinding process requirement.
More information details ,http://www.halnntools.com/ ,Or contact with us halnntools@gmail.com,skype:cbn_inserts_angels
