Analyze CBN inserts cracking phenomenon

Summary

CBN Cutting tools abnormal cracking is what customers most boring,which will increase Processing cost,work piece scrap or reworking,lower the processing efficiency and other problems.Especially CBN insert with high price,cracking phenomenon will cause lots of waste,so it is so important to choose the most suitable CBN inserts.

Halnn superhard material summarized some chipping reasons as following:

1.CBN inserts itself performance

The overall sintering between main CBN granule and suited binder will exit a high tensile strength,which is the advantages of common CBN inserts when rough machining work piece.Except the high purity require when producing CBN inserts,the CBN(cubic boron nitride) micro powder also need deoxidized and other many process,and test its bulk density,this is just the most important reason for different  quality CBN inserts in the market.In addition,the synthesis process directly decide the dimension and size of the poly-crystalline grain when processing CBN inserts.

2.The selection of CBN inserts

The cutting depth of soldering CBN inserts should be controlled within 0.3mm or even less to ensure using safety, any manufacturers compound CBN inserts can not make sure there is no chipping when facing interrupted turning condition,this condition must choose Solid CBN inserts.

3.The selection of the CBN inserts type

The impact resistances comparison with the same grade CBN inserts:round insert,commonly 25°,45°,75°,83°,90°(the inserts angle after install ),and the width and angle of CBN inserts itself negative chamfer also affect the CBN cutting tools strength.

4.Cutting parameter influence

Reduce the feed rate is the most reliable method from the cutting force;we need turn down the revolving speed when interrupted turning or machining both long and thin shaft.

5.CNC lathe reason

The machinery overall system rigidity must be high,In order to avoid shaking during machining;we also need avoid the jammed when rough machining.

6.The extend length of the inserts arbor

If the inserts arbor extend long length,it will have the  risks on shaking and chipping,the extend length need within the arbor size.

7.The inserts arbors quality reason

Good quality inserts arbor has a excellent heat-conducting property, high machine rigidity, seismic performance;although the price is a little higher,but the total processing cost will not have a big change,and it will reduce the inserts unnecessary waste.

8.The cutting fluid

Cooling liquid can be used when rough machining gray cast iron or other materials,but the thermal stress will cause CBN inserts cracking risk.

In some conditions,CBN inserts own impact resistance and heat-conducting property are not contradictory.For example,YG series cutting tools have a good impact resistance,but there are a strong cutting resistance will also make the inserts cracked,this condition will mislead the researchers and customer thinking that the inserts doesn't have a good impact resistance,but the actually reason is the cutting tools was not good wear resistant.

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

Halnn release Hard turning bearing rings CBN inserts BN-S20

Hard turning bearing ring technology:

Step 1:Finish turning the base level end, the base level end will be less than 0.005 mm after finish turning ,then turning the outer diameter of the shaft washer;

Step 2:Turn to another face for turning

Step 3:Turning the upper end surface (inside the channel); convert  the workpiece platen, then turning the upper end surface.（outside the channel）

Step 4:Hard turning the spherical channel (Halnn superhard CBN spherical inserts ), the channel bottom range will less than 0.005mm after hard turning ,the channel surface roughness will be Ra0.3μm

Step 5:Finish turning inner diameter of the shaft washer.

With above technology ,the wall thickness difference of the push ball bearing ring will less than 0.01mm,which is more than the precision value of P5 grade bearing .

Application Case 1：Hard turning wind power bearing ring.

Machining Targets: variable pitch bearing ring used for 1.5MW wind power machine sets.

Machine:CNC Vertical Lathe

Cutting Inserts Grade:Halnn superhard BN-S20 CBN inserts

Workpiece Dimension: Outer diameter φ1900mm，Thickness 130mm，

Roughness after finish turning：The channel bottom range of double peach channel after finish turning all less than 0.005mm ,and the channel surface roughness will reach Ra0.3μm.

Application Case 2: Turning the bevel of the Precision angular contact bearing ring 

Machining Targets : Precision angular contact bearing

Cutting Inserts Grade:Halnn superhard BN-H20

Inserts Lifetime:Machining about 1000 sets /cutting edge; smooth finish≤Ra0.4

Advantages of hard turning the bearing ring

 1.High working efficiency

For example, like variable pitch bearing ring which is used for machining wind power 1.5 MW machining sets in bearing industry.If grinding machining all the allowance after queching ,the grinding time is above 18 h, but use the turning instead of grinding process,just need 4.5h .At the same machining precision,the turning machining efficiency is 4 times than grinding machining .

2.Low cost

For example , like turning the 1900 variable pitch bearing ring ，use Halnn superhard BN-S20 grade solid CBN inserts can finish turning more than 30 piece bearing ring.

3.Reduce pollution

Compared with the grinding iron grain with the turning iron scraps, it will be more convenient to deal with the iron scraps ,and the irons scraps cost lower as resource ,also reduce the pollution .

Conclusion

When turning the large-scare and high-precision bearings,using hard turning technology (used turning instead of grinding process) has become a trender in bearing industry .This technology has high machining effiency ,low cost ,traditional technology can not contend with it .As BN-S20. BN-H20 grade superhard inserts enter into the market , the smooth finish and reliability which use turning instead of grinding process become better ,and the inserts cost become lower .

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

The lifetime and wear resistance of CBN inserts

Part 1 Summary

The common failure mode of cutting tools is wear,the inserts lifetime has a lot to do with the wear resistance,after testing,the CBN(Cubic Boron Nitride) inserts lifetime is usually several longer times or even more than carbide inserts and ceramic inserts.CBN inserts lifetime is not only relate the tools quality,but also related to the workpieces materials, machining speed etc.So it is necessary to know more about the relationship between CBN inserts lifetime and performance,use the suitable CBN inserts,increase machining efficiency,reduce the the unnecessary machining waste.

1.The comparison between CBN inserts lifetime and other materials inserts

(1)The round CBN inserts from Halnn super hard,with cutting parameters Vc=40m/min,f=0.16mm/r to machining chilled cast iron with HRC55.CBN inserts durability is 500 min ,but the ceramic inserts is just 5 min.CBN inserts durability is 100 times longer than ceramic inserts.The solid Polycrystalline Cubic Boron Nitride(PCBN) inserts developed by Halnn superhard was widely used in roughing application,CBN inserts begin used in roughing process with big feed rate and cutting depth.It has a higher cutting efficiency than carbide inserts.For example,CBN inserts turning chilled cast iron roll,getting a high cutting efficiency.The cutting parameters:Vc=61m/min,ap=/mm,f=0.94mm/r,the metal cutting efficiency can reach 400cm3/min,the inserts almost has no wear.

(2) Halnn superhard CBN inserts machining the gray iron,cutting parameter:linear speed 600m/min,was 2 higher times efficiency than carbide inserts,the lifetime can be improved about 6-12 times longer when roughing,has 15-20 times longer lifetime than carbide inserts when finishing.

Part 2 The relation between CBN inserts grade and its performance

The CBN inserts performance is closely to the CBN inserts grade.The CBN granularity, contect, and the different kind of binder directly decide CBN inserts performance,each manufacturer define them own grade according to the performance and element,the grade cant used universally although they are similar.

CBN inserts can be divided into two categories according to its organization:one is made by CBN grain sintered directly without binder,has a high CBN content(more than 70%),has a high hardness,used for turning machining the heat-resisting alloy,cast iron and iron series sintered metal;another category is base the CBN grain as the main body,according to the ceramic binder(main contain TiN,TiC,TiCN,AIN,Al2O3,etc)sintered,this kind CBN inserts has a low content CBN(less than 70%),has a lower hardness,just suir for machining the hardened steel.

The classification of CBN inserts grade:Halnn superhard CBN inserts can be divide into rough machining and finish turning according to CBN inserts granularity size;The detail classification is based on the CBN grain crystal.

1.The CBN grain crystal classification of CBN inserts

The size of CBN grain crystal can be divide into three categories: coarse grain (the average size is 20-50μm),medium size grain crystal(10-20μm), fine grain(2-10μm).the larger size of the grain,the better wear resistant and longer lifetime the CBN inserts will have.but the blade of the inserts will be worse,its hard to make a high precision inserts. On the contrary,the the fine grain CBN inserts has a good quality blade,the work piece will have a good surface after machining.There are 1μm,less than 0.5μm grain now,we can choose the different size grain according to the different machining process require of roughing and finishing.

2.The corresponding work piece of the different CBN inserts grade

Currently CBN inserts don't have a uniform classification just like carbide inserts,each manufacturer has themselves type and grade,we need choose base on them catalogue during using.The famous CBN inserts grade was BK-K1 and BN-H1 which were developed by Halnn super hard material company,those two grade inserts was used for machining cast iron and hardened steel separately.Later,BN-S20 and BN-S30 grade inserts were the solid PCBN inserts,can machining:High-chromium cast iron,white cast iron, austempered ductile iron,high-temperature alloy, powder metallurgy,gray cast iron,hardened steel and so on,connect the machining condition(roughing , semi-finishing,finishing)require to the CBN grain size to form the CBN inserts grade.

The different CBN inserts grade has a different cutting performance as the different composition,so we need pay more attention when choose the CBN inserts.

Part 3 How to judge the CBN inserts quality

Judge the CBN inserts from the using point of view,the good quality CBN inserts has two characteristic:

1.Has a good impact resistance,especially in the roughing field,the inserts will not crack,this is most basic guarantee use security of CBN inserts.

2.Has a good wear resistance,in the same time for ensure the efficient machining also can reduce the cost and can instead of carbide inserts and ceramic inserts,this is the economical guarantee of CBN inserts.

Part 4 Discriminate the inserts wear resistance and toughness

It is not difficult to improve the cutting tools hardness and toughness,but with increase of the cutting tools materials hardness,the toughness will reduced,so we need consider the work piece material,the CNC lathe,machining condition comprehensive in use,avoid the contradiction between the hardness and toughness.Aim at the CBN inserts character,Halnn seperhard company research one grade CBN inserts which suit for cutting with low speed and roughing,it has a excellent impact resistance,Halnn superhard material company enjoy a high reputation in cutting tools industry.

Part 5 High efficiency machining is not mean machining with high speed

Cubic boron nitirde is the highest hardness cutting tools material for machining the ferrous metals,so most people thought ‘high hardness,low toughness,just suit for high speed cutting or high precision machine tool’ by mistake,but its not.High efficient machining is not mean high-speed machining,the cutting tools lifetime also will reduce with the increased linear speed even the CBN inserts has a very high hardness.

It is more suitable to machining the difficult processing materials with increasing the cut depth and feed rate for improving the machining efficiency.This is the Halnn superhard company purpose to the reason why research the cubic boron nitride inserts,and facts proved that this case solved the customers practical machining problem,The CBN inserts from Halnn superhard company will not crack when machining with high efficient,expeciall in the industry which interrupted cutting the difficult cut material,this is also the biggest success in the hard cutting tools field.

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

How to choose CBN inserts machining high hardness materials and the cutting parameters 

The machine range of Halnn superhard CBN inserts:

1. High hardness cast iron/cast iron machining,such as:rough machining and finish turning high chromium cast iron,white cast iron,Ni-hard cast iron, wear-resistant heat-resistant steel.

2. Machine high hardness after heat-treatment,such as:hard turning hardened bearing steel, Carburizing steel, tool steel and die steel after heat-treatment.

3. Other materials difficult to machining: superalloy,powder metallurgy,etc.

4. Ordinary gray cast iron, high grade of nodular cast iron.

Halnn superhard CBN inserts machine high hardness steel parts

When turning high hardness alloy steel,the workpiece has a high hardness,produce a large turning quantity heat,has alarge cutting force;causing the hard turning tools rapid wear,or the insert tip appear chipping.Halnn superhard suggest the cutting parameters with the experience of turning high hardness alloy steel.

The insert material and characteristic of Halnn superhard CBN inserts turning high hardness alloy steel

BN-S20 CBN inserts:rough machining and finish turning high hardness alloy steel with HRC45—HRC79.Such as:High hardness W18Cr4V, high-speed steel after heat treatment,Cr12MoV  tool steel,GCr15 ball bearing steel,9SiCr tool steel,20Cr,15CrMo,65Mn alloy steel material.It also can rough machining cast wear-resistance alloy ZGMn13,can restore high hardness alloy steel with big allowance rough machining,it also can stand strong interrupted cutting.It is one of the most popular superhard inserts.Following is the case of the BN-S20 CBN insert:

BN-H20 CBN inserts:It suit for finish turning high hardness alloy steel with HRC45-HRC68 with high-speed,such as:hard turning the 40CrMo,20CrMnTi gear after heat-treatment;BN-H20 use the Ceramic bond,has a higher thermal conductivity.It suit for high hardness alloy steel workpiece after heat-treatment,such as:high-speed finish turning hardened steel, nitride  steel, carburizing steel ,etc. 

Application case as following:

Cutting parameters of Halnn superhard tools machine high hardness alloy steel

Processing material	Cutting parameters and CBN inserts grade
	Linear speed Vc(m/min)	Cutting depth ap(mm)	Feed rate(mm/r)	CBN inserts grade
High hardness steels(hardness≥HRC45)	35-90(rough)	1-10	0.15-0.7	BN-S20
	60-120(finish)	≤1	0.05-0.35	BN-S20 or BN-H20
Superalloy (hardness≥HRC35)	200-500(rough)	1-10	0.2-1	BN-S20
	500-1500(finish)	≤1	0.05-0.3	BN-S20 or BN-H20

High hardness alloy steel include hardened steel,heat-resistant alloy,such as:alloy steel 3Cr2Mo,4Cr5mOv1Si which widely used for mold material,the hardness usually was between HRC45 to HRC68,some Nitride steel was above HRC65.

  

When machining high hardness alloy steel,we usually use BN-H20 CBN inserts when machining allowance was more than 0.5mm,if need one tool for rough machining and finish turning with big allowance,choose BN-S20 is better.

CBN inserts grade and instruction of Halnn superhard CBN inserts machine high hardness cast iron material

The hard point,pore,surface chill layer and sand in the cast iron workpiece did take some trouble during machining,quickening the inserts wear and damaged,especially machine cast iron mass in a assembly line,reduce the production efficiency;change the insert during finish machining big casting surface will affect the quality.As the application amount of the casting was large,reducing the machine cost or improving the efficiency will take us a objective economic benefits.So people request better insert for turning cast iron parts.Such as:mineral,building and metallurgy machinery parts made of white cast iron,high-chromium cast iron.Halnn superhard material company post BN-K1 and BN-S20 CBN inserts which can rough  machining high hardness cast iron in 2007. BN-S10,BN-S20,BN-K10,BN-K20 CBN inserts from Halnn superhard company achieve good result when machining high-chromium white cast iron and chilled cast iron;while the development of BN-S30 CBN inserts make a good result aiming at machining the wear resistant cast iron,this insert has a better wear resistance and higher hardness,suit for semi-finish and finish turning cast iron material workpiece.

Halnn superhard CBN inserts grade and cutting parameter:

Processing material	Cutting parameter and CBN insert grade
	Cutting linear speed Vc(m/min)	Cut depth ap(mm)	Feed rate(mm/r)	CBN insert grade
Hard cast iron (hardness:HRC35-68)	35-90(rough)	1-10	0.15-0.7	BN-K1
	60-120(finish)	≤1	0.05-0.35	BN-K1 or BN-K10
Grey cast iron/nodular cast iron	200-500(rough)	1-10	0.2-1	BN-S30
	500-1500(finish)	≤1	0.05-0.3	BN-K20 or BN-S30

The kind of Halnn superhard tools grade:

Grade	Classes	Application range
BN-K10	Soldering CBN insert	Suit for continuous finish turning gray cast iron and wear-resistant alloy cast iron materials, such as finish turning the brake drums, brake discs, flywheels, cylinder and other parts and high hardness cast iron materials.
BN-K20		High-speed finish turning gray cast iron, nodular cast iron, powder metallurgy finishing materials, and suitable for high speed precision boring.
BN-H10		Mild intermittent continuous or finish turning hard steel, such as the "turning instead of grinding" gears, bearings, etc.
BN-H20		Strong/semi-interrupted finish turning and high-speed finish turning, such as a variety of high-precision profiling shafts and gears, bearings, turning and small bore machining.
BN-K1	Solid CBN insert	Good impact resistance ,Rough machining high hardness cast iron in big margin such as:high-chromium alloy cast iron, high nickel chromium alloy, chilled cast iron, white cast iron; widely used in mining,metallurgical machinery,cement,electrical equipment wear spare parts.
BN-S20		Perfect balance between Impact resistance and abrasion resistance,can roughing,semi-finish turning and finish machining,suit for kinds of high hardness material,such as: High temperature alloys,heat-resistant steel, high hardness cast iron / steel, hardened steel, nitrided steel, carburizing steel.
BN-S30		High wear resistance and appropriate impact resistance,suit for high-speed finish turning gray cast iron,ductile iron, alloy cast iron and powder metallurgy, and suit for high-speed and efficiency boring, milling,

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