Halnn CBN Cutting tools processing hardened steel well

 As the Hardened steel has a good performance, it  used in various mechanical industries widely.We all know hardened steel was a steel workpiece which been heat treated,the hardness was usually HRC45 or higher ,and its difficult to process, especially
in roughing , interrupted cutting or when the grooving, with a large margin.So we need choose a tools which  with a higher intens-ity and better impact resistance.

This article mainly introduce the performance characteristics of the harden steel and how to choose the right materi-als of the cutting tool to cut hardened steel.

Part 1 The performance characteristics of cutting hardened steel and the simple processing of cutting hardened steel

1.    the features when cutting hardened steel when

(1)The harden steel has a higher hardness and strength after heat treatment,
almost no plastic; 

(2) hardened steel has a huge cutting power and high temperature when cutting , this easily lead to edge chip-ping or severe abrasion; (3) not easy to BUE; (4) lower thermal conductivity.

2. the process of cutting hardened steel: cutting - casting (or forged) - normalizing (or annealing) - roughing - Heat treatment - Grinding. These are the beginning of the process,the workpiece is difficult to machine due to the  higher hardness after heat tre-atment , grinding can only be the final step of cutting hardened steel, but the grinding efficiency is very low, with production gra-dually hardened steel, grinding affect the overall processing efficiency. Therefore, with the continuous research of tool industry practice, ultimately has developed a hardened steel cutting tools,lathe instead of grinding , they are :carbide cutting tools, coa-ted carbide tools, ceramic cutting tools and cubic boron nitride(CBN) tool. Divided by the hardness: Carbide Tool <Coated Carbide Tool <ceramic tool <cubic boron nitride(CBN) cutting tool; toughness: Ceramic Tool <Carbide Tool <Coated Carbide
Tool <cubic nitride boron tool, You can get this Specific analysis as follows:

Part 2 The tools for cutting hardened steel

Carbide Tool: Carbide Tool is the latest developed one more than other three tools, and is still mainstream products in the tool industry, but not for cutting hardened steel because of the hardness of the carbide cutting tools body is between HRC71 to 76, and the hardness of hardened steel after heat treatment was general about HRC45 or more, the tool does not wear well in the process, if you didn’t usually cut hardened steel with it, without considering the overall processing efficiency and tool costs in the case, you can select the appropriate carbide cutting tools.
Coated carbide tools: coat a layer of wear-resistant material about 2 ~ 18μm on the carbidecutting tools which has a good toughness,It has a better strength, hardness and wear resistance than uncoated carbide tools . But there are not enough good, mainly due tothe wear layer of surface coating is too thin, after the wear layer was run out, its performancewas just like the carbide cutting tools without wear coat. But still can turning the workpiece which hardness is less than HRC45 workpiece at low speed.

Ceramic tool: we all know the ceramic tools had a better hardness, strength, wear resistance than the carbide tools and coated carbide tools, but the only biggest disadvantage was its bad brittleness, ceramic tool using normal , lathe speed was 2 to 5 times than carbide tools, especially suitable for using high hardness materials processing, finishing and high-speed machining. Can machine the hardened steel workpiece which hardness was betweenHRC45 to 55, but we don’t suggest you choose the ceramic tools when intermittent cutting or margin excessive, ceramic knives met this casewill chip intermittently, and it only can turning hardened steel with a small feed cutting or knife depth.

Cubic boron nitride(CBN) tools: The resistance and hardness of CBN tools is just next to the diamonds, has a excellent high-temperature hardness.CBN tools has a  better impact  strength and resistance crushing performance compared with ceramic tools.It is widely used for cutting hardened steel which has a hardness more than HRC45, it has a new better cutting speed compared with carbide cutting tools.Especially the non metallic adhesiveIn cubic boronnitride cutting tools researched by Halnn superhard tools company, Solved the problem which traditional cubic boron nitride cutting tools just can finishing machine the hardened steel .

Since Halnn superhard company founded, keep researching ,offering high-quality, high-performance tool products. With long-term trying,cutting-edge technology and  development  capabilities, Being the first one who raise "CBN overall polycrystalline Blade"concept. And Halnn Superhard tools got a high reputation in the industry.

Halnn superhard company developed the different grades tools according to the different hardened steel.The Halnns tools not only has a high effectiveness but also with a low cost. We suggest the followed parameters and the corresponding cutting
grade tool as the table:

What we can get from the above table: The BN-S20 grade tools researched by Halnn superhard company can machine both rough and finishing, as the BN-S20 brands belong to non-metallic adhesive overall PCBN cutting tool (as Picture 1 ), it has a higher hardness, better wear resistance and impact resistance, also can be interrupted cuts and a large margin of cutting hardened steel. there are a lot of brands for the finishing process , they mainly were the welding cubic boron nitride(CBN) cutting tool (as Picture 2), the depth of
cut is better controlled in less than 0.5mm, the BN-S200 grades belong to the monolithicCBN tools , but mainly for the finishing process.
Here's a brief introduction to the actual cases about cutting parameters of Halnn superhard cubic boron nitride cutting tool
for cutting hardened steel.

Part 3 The case
1.Halnn superhard cubic boron nitride cutting tools BN-H10 grade for hardened steel gear  cutting parameters:ap=0.2mm,Fr=0.1mm/r,Vc=180m/ min.

2.Halnn superhard cubic boron nitride cutting tools BN-H20 grade hardened steel synchronizer  cutting parameters:ap=0.15mm,Fr= 0.1mm / r,Vc=170m/min.

3.Halnn superhard cubic boron nitride cutting tools BN-S20 grade hardened  steel gear (strong interrupted cutting) cutting parameters: ap = 2.5mm, Fr = 0.12mm / r, Vc = 90m / min.

4.Cutting parameter of Halnn superhard cubic boron nitride cutting tools BN-S200 grade  hardened steel slewing ring bearings: ap = 0.5mm, Fr = 0.45mm / r, Vc = 110m /min.

Part 4 Summary

Recently, with the development of modern technology, more and more hardened steel difficult to machine appear on the processing site, machinery manufacturers has been looking for efficient cutting tools material for hardened steel in order to get a good piece size and hardness of the workpiece.which for the tool industry, as long as the constant times, developed
a high hardness, high-quality, high-efficiency tools material, will be able to obtain benefits for the company,at the same time also can promote state's development of machinery manufacturing industry.

More information ,please check our web:http://www.halnntools.com/news/case/127.html ,feel free to contact with us halnntools@gmail.com ,Or skype:cbn_inserts_angels

The project of Halnn CBN inserts finish turning hardened steel

1.Turning characteristics and finishing technology of hardened steel

A.Turning characteristics of hardened steel.

Hardened steel means the steel after quenched,the organization is marten site,one kind steel with above HRC50. There are some characteristics when turning hardened steel: 

(1) High hardness, high strength,almost no plastic;

(2) Big cutting force,high cutting temperature ;

(3) Not easy to built-up edge

(4) The cutting edge is easy to chipping,wear and tear;

(5) Low thermal conductivity

B.Technological changes when finishing machine hardened steel

The hardened steel has a high hardness as it after quenched, Grinding is the traditional method to meet the required size precision and finish, but the grinding efficiency is too low. As the increasingly widely used of carbide coated cutting tools,diamond inserts,ceramic inserts and Cubic Boron Nitride(CBN) inserts, diamond, hardened,a new technology appeared,turning the hardened steel,it also called turning instead of grinding.

Advantages of turning instead of grinding :

(1) More efficient , time can be saved more than tenths in some cases

(2) Work piece has a better geometry shape than grinding,

(3) CNC lathe is much easier to maintain .

Following are the case of process the hardened steel by turning replace grinding,briefly introduce the choice of cutting tools materials when finishing hardened steel and the application case of Halnn CBN cutting tools finish turning hardened steel

2. The choice of cutting tools materials during finishing hardened steel

It is a important requirement to choose inserts materials reasonable when finish machining hardened steel .Inserts materials must have characteristic of high hardness ,better wear resistance,heat resistance,and have a certain strength, thermal conductivity according to the hardened steels cutting characteristic.

(1) Carbide alloy inserts: The carbide inserts hardness is about HRA89-89,equal to 71-76 HRC,it is easy happen burning the inserts so that wear quickly and having a low machining efficiency when machining the hardened steel with hardness above HRC40,so carbide inserts is suitable to finish machining the work piece with hardness less than HRC45,and with low turning speed.

(2)Ceramic inserts:As ceramic inserts has a big brittleness,chipping is easy happened, suit for machining the work piece with hardness between HRC40 to HRC55,but its better to avoid the interrupted turning.

(3) Halnn Cubic Boron Nitride(CBN) inserts BN-H20 and BN-S20 grade:suit for machining the steel work piece with hardness above HRC55.You can choose BN-H10 and BN-H20 grade CBN inserts if the cutting depth within 0.3 mm when finish turning,the two grade CBN inserts are both belong to brazed cubic boron nitride(CBN) cutting tools,the difference between the two grades CBN inserts is: BN-H10 grade is only suitable for continuous turning,while BN-H20 can stand medium interrupted turning work piece.

You can choose BN-S20 grade CBN inserts when rough machining the cutting depth reach above 0.5mm or interrupted finish turning hardened steel, this grade CBN inserts belong to non-metallic adhesive,it can not only interrupted turning hardened steel,but also can cut off the hardening layer with big allowance without wear the cutting tools,this is the biggest difference compare with the market common CBN inserts.As this three grade CBN inserts hardness reach about HV8000-HV9000, refractoriness reach 1400℃-1500℃,them cutting speed is few times faster than carbide inserts,CBN inserts lifetime is few dozens longer than carbide insert.Following are the three grade CBN inserts advantage and what material can machining with them.

BN-H10 grade CBN inserts performance advantages and processing material

Cutting tools  grade	Suitable for processing material	Performance advantages	Typical application industry
BN-H10 CBN inserts	Hardened steel  and high strength cast iron	Suitable for high speed finish machining, has a good balance between abrasion resistance and fracture damage resistance.	Baring, gear, gear shaft, constant speed coupling; Pearlitic nodular cast iron, etc.

BN-H20 grade CBN inserts performance advantages and processing material

Cutting tools  grade	Suitable for processing material	Performance advantages	Typical application industry
BN-H20	Hardened steel,materials difficult to turning	More flexible cutting tools, more cutting edges. Have good abrasion resistance and fracture damage resistance when machining the difficult cutting material such as hardened steel	The brake disc, brake drum, cast iron parts, hardened steel gear, etc

BN-S20 grade CBN inserts performance advantages and processing material

Cutting tools  grade	Suitable for processing material	Performance advantages	Typical application industry
BN-S20	Hardened steel, high strength steel, rolling hard steel, heat resistant steel, nickel base alloy and its surface hardening materials	Have excellent heat resistance and wear resistance when machining hardened steel and High strength steel	Hardened steel roller, screw, wind power bearing, high speed steel roll, the wear-resisting layer of oil drill pipe, etc

3. In which condition is more effective when turning instead of grinding with using the above three grade CBN inserts turning hardened steel

(1)It not only can reduce the amount of labor to 1/3～2/3 when cutting several complex surfaces in the CNC lathe,but also can  ensure a very high location accuracy by turning instead of grinding.

(2) when grinding the complex shape inner bore or small bore,the requirement of the grinding wheel is much strict,and cant grinding well sometimes, , then turning is the best way to machining the bore.

(3) If one part has few surfaces (outer circle, inner hole, face, stage, groove) are all required to grinding, just one process can be completed if use turning, you can save the grinding work procedures.

(4) Parts after quenched is easy to deformation and waste when leave a little allowance.You can leave a big allowance first,and then quenching, finally cut off the spare allowance and turning so that reduce the parts waste.

(5)Use CBN inserts machining high frequency parts which used under amount of load change and differ 

4. The case of Cubic boron nitride(CBN) cutting tools BN-H10 grade, BN-H20 Grade and grade BN-S20 machining hardened steel:

(1)BN-H10 grade PCBN inserts finishturning gears steel (after quenching hardness 58HRC-63HRC) :cutting parameters:ap=0.2mm,Fr =0.1mm / r, Vc = 180m/ min.Cutting state: continuous cutting, dry cutting.  

Halnn BN-H10 grade CBN inserts compare to ceramic tool (see below)：The cutting speed of Halnn BN-H10 grade CBN inserts is 1.4 times faster than ceramic inserts ,and the life is 5 times longer . Efficiency has been great improved and the machining time is saved.

Inserts material	Cutting speed	Inserts life	Produce tact
Halnn BN-H10 CBN inserts	180m/min	800pieces/per cutting edge	6 seconds
Other brand ceramic inserts	130m/min	150pieces/per cutting edge	8.5 seconds

(3) BN - S20 grade CBN inserts finishing the ball screw, processing materials: Chinese brand 40CrMo or Gcr15, HRC60-62 hardness, cutting parameter: ap = 4.5 mm, Fr = 0.10 mm/r, Vc = 90 m/min, cutting way: dry cutting.(2)BN-H20 grade CBN inserts finishing synchronizer (after quenching hardness 58HRC-63HRC) case: cutting parameters: ap = 0.15mm, Fr = 0.1mm / r, Vc = 170m / min. Processing Step: finishing groove, continuous cutting, Cutting state: Dry Cutting.                   

Inserts materail	Cutting speed	Cutting depth	The final failure forms
Halnn BN-S20 CBN inserts	90m/min	4.5mm	Normal wear
Other brand ceramic inserts	65m/min	0.5mm	Chipping

BN-S20 brand CBN inserts compare to ceramic blade : The cut depth of Halnn S20 grade CBN inserts is 9 times deep than ceramic inserts under the 1.3 times faster than ceramic inserts cutting speed, the BN-S20 grade CBN inserts case subvert the knowledge which people always thought that Cubic Boron Nitride(CBN) inserts just can finish machining,as the non-metallic adhesive BN - S20 grade inserts impact resistance was improved ,BN-S20 CBN inserts can stand the 7.5mm cut depth,saved the machining time by reducing the feed times,and also reduce the machining cost , realize people rough machining the quenched steel and heavy turning the big size hard work piece. 

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

The reasonable parameters of CBN inserts Hard turning bearing steel after quenching

1.The hardness standard conversion of the bearing steel after quenching

The hardness of bearing steel after quenching usually is above HRC45,some even more than HRC60,the conversion between Rockwell hardness and Vickers hardness,we can get a very accurate result with additional formula HRC=100-37353/(HV+200),this formula is so convenient in the practical application.Common hardness comparison table which people usually used is not suit for quenched steel.

2.When need CBN inserts hard turning bearing steel after quenching

Firstly,choosing the appropriate insert material,if the hardness of the bearing steel after quenching is above HRC55,choose CBN insert is the best choice,if the hardness is below HRC45 and finishing process,you can choose one better after comparing the economy between CBN insert and ceramic insert aim at this case.If just hard turning quenched steel infrequent,you can think about YT726 or others carbide turning tools.

Notice: PCBN inserts(Halnn company BN-H10,BN-H20 grade)cutting depth usually is within 0.3mm,and need try to avoid interrupted turning,can get a good surface roughness when finish turning bearing steel,realize turning instead of grinding.If the cutting depth is above 0.3mm or interrupted turning quenched steel,BN-S20 grade from Halnn superhard material company can meet this requirement completely.(BN-S20 grade CBN inserts cutting depth can reach above 7mm when hard turning quenched steel) 

3.The cutting parameter of CBN inserts hard turning bearing steel after quenching 

CBN inserts hard turning quenched bearing steel: cutting speed usually is 80-120m/min,if the work piece has a much higher hardness,its better choose a lower cutting speed,for example,its better to turning the work piece with 70HRC hardness by 60-80m/min cutting speed,if the lathe machine has a high rigidity, Halnn BN-S20 grade CBN insert almost can finish the most allowance just with one feed,just leave about 0.3 as the finishing allowance,the feed rate was choose according to the roughness require,suit about 0.1mm/r.

4.CBN inserts parameter Selection 

CBN inserts parameters:usually chose 0.2*20 degree chamfer when roughing or interrupted machining,choose 0.1mm width chamfer when finishing,the tools nose radius of circular arc according to the detail condition.

5.Notes when using CBN insert machining quenched bearing steel

(1)dry cutting,if there are some reason so that need add water,you can use Halnn company BN-H10 grade CBN inserts,this grade insert has a good lifetime under wet cutting.

(2)Choose the CBN inserts grade:Need chose BN-H20 when turning the bearing steel instead of grinding,try to shorten the extended length of holder for decrease the vibration and get a better surface roughness.If the machining allowance of the quenched bearing steel is a little big,we recommend BN-S20 grade CBN insert.(This two grade CBN insert are both researched by Halnn superhard material Co.,Ltd.,win national key technology of production, study and research project results,has the best toughness and lifetime in the superhard cutting tools industry)

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