Halnn publish new type CBN inserts which can Hard Turning slewing ring bearings instead of grinding

Bearing Steel is one of the most demanding steels,it need high requirement on the materials:high hardness ,wear-resistance,contact fatigue strength,elastic limit,good impact toughness,fracture toughness, dimensional stability, rust resistance,hot and cold processing property,ect.So bearing steel must strictly require the uniformity of the chemical composition and carbide distribution.

Bearing Steel can be found almost everywhere,widely used in transportation ,wind power,Metallurgy and Petro-Chemical Machinery industry,such as slewing ring bearings ,Metallurgy bearings (called GCr15 bearings),ect.This article mainly introduce machining slewing ring bearings technology and inserts selection.

Part 1 Slewing ring bearings materials selection

(1)Slewing bearings definition:It is a kind large-scale bearings which can bear combined loads,large axial, radial load and overturning moment at the same time.It is called “Machine joints”.

(2)Slewing bearings materials selection:Slewing ring rolling elements usually use solid hardened carbon chromium bearing steel which is made of GCr15 or GCr15SiMn steel;Slewing bearings ring use surface hardened steel,we usually use 50Mn steel materials when users don’t have special requirement ,but sometimes we will choose other grade surface hardened steel like 42CrMo,5CrMnMo depending on user’s usage condition details.

Part 2 Process optimization of slewing ring bearings

For large-scale slewing ring bearings ,we need compile a reasonable machining technology before going into the workshop,it need get drawings measurement and precision and meanwhile can not affect the working efficiency .Following will introduce slewing ring bearings process routine:

Slewing ring bearing technology machining process :

Baiting---Forging---Annealing---Turning---Heat-treatment---Grinding---inspecting---Antirusting---Putting into warehouse.

The hardness of large-scale slewing ring bearings after heat-treatment  is above HRC45,and usually use grinding machining slewing ring bearings ,even though it can get high work piece precision ,but grinding efficiency is very low,which will affect working efficiency.

As the development of cutting technology ,casting cutting tools industry developed new cutting tools materials which can use turning instead of grinding ,turning instead of grinding process can not only improve work efficiency,but also satisfy drawing requirement.Currently Machinery factory usually use simple machining process:Rough machining---heat-treatment---finish turning and use turning instead of grinding.

In current times,there are 3 kinds cutting tools using turning slewing ring bearings instead of grinding:carbide tools, ceramic cutting tools, cubic boron nitride cutting tools. The followings will analyze three kinds of cutting tools advantages and whether suit for machining slewing ring bearings or not .

Part 3 Cutting tools materials used for machining slewing ring bearings  

The hardness of the slewing ring bearings after heat-treatment usually is above HRC45,channel part hardness usually is HRC55-62,so it will be difficult machining.We don’t advise use carbide and ceramic cutting tools ,but many factory use them to machining slewing ring bearings ,it will be found that the cutters has poor wear-resistance and often chipping ,the processing result can be unsatisfactory. Compared CBN inserts with Carbide and ceramic cutting tools ,CBN inserts not only has high hardness,but also has good wear-resistance and wear-heat,but large brittleness is undeniable, especially for machining discontinuous surface,CBN inserts still are unsatisfactory,also have same problems:poor wear-resistance and often chipping.China Halnn superhard materials research BN-S200 grade and BN-S20 grade CBN inserts through cutting tools industry’s continuous research and practice.The above materials both use non-metal (ceramic) as adhesive,which make sure high hardness ,wear heat-resistance and improved impact toughness ,BN-S200 used for finish turning  and BN-S20 used for both rough and finish turning .

Halnn superhard is the first one proposing concept on rough turning “Solid polycrystalline Cubic boron nitride cutting tools ”,  and accurately grasp the pulse of the times and research “high speed,finish machining”turning inserts ,milling cutters, CNC blade relying on long-term accumulation of technical strength and top technology development capability. Halnn Superhard materials has high reputation in Superhard tools academia .

The following will introduce the case of turning slewing ring bearings with Halnn CBN inserts  

Part 4 Halnn Superhard turning slewing ring bearings application Case

The work piece after heat-treatment will be deform,so we need choose different allowance depending on different work piece . The following we will choose cutting inserts grade and cutting parameters depending on the machining allowance.

(1)Finish turning slewing ring bearings allowance is less than 2mm: 

Choose Halnn Superhard BN-S200 CBN inserts (following figure),cutting depth will be less than 0.5mm. turning parameters:ap≤1mm，Fr=0.05-0.35mm/r,Vc=60-250m/min and the cutting parameters can range depending on machine rigidity.

Application Case 1:

Materials:42CrMo slewing ring bearings ;

Hardness : HRC47-55

Process:finish turning channel rolls,end surface

Cutting parameters:ap=0.5mm，Fr=0.45mm/r,Vc=110m/min

Efficiency:Compared to ceramic inserts(following figure):

On the basis of CBN inserts cutting speed is 22% higher than ceramic tool, the tool lifetime is 7 times than ceramic inserts, and roughness ensure less than Ra1.0.

Cutting Tools Materials	Cutting Speed	Cutting Tools lifetime	Roughness
Halnn BN-S200	110m/min	8pcs/cutter edge	Ra0.6-1.0
Some European brand ceramic inserts	90m/min	1pcs/cutter edge	Ra0.8-1.6

(2)Finish turning slewing ring bearings allowance is more than 2mm:

Choose Halnn superhard BN-S20 grade CBN inserts (following figure),machining circumcircle and groove parts of slewing ring bearings ,cutting depth can cut entire depth of the blade,cutting parameters:ap=1-10mm，Fr=0.15-0.7mm/r,Vc=50-150m/min and can range depending on machine rigidity.Efficiency: cutters has long lifetime ,and the roughness can arrive Ra0.4.

More information,http://www.halnntools.com/ ,Or contact with us halnntools@gmail.com,whatsapp:+8615036165377,skype:cbn_inserts_angels