Turning inserts for hard turning hardened steel

Part 1 Coated carbide material inserts

Coated carbide inserts is coating on good toughness carbide cutting tools by the thickness of 2-18µm.It lowers the heat conduction efficiency after coating and abate the hot action of cutting tool substrate, Coating can effectively improve the cutting process of friction and adhesion effect, reducing the heat caused during cutting. Coated carbide cutting tools has a better strength, hardness and wear resistance than the carbide cutting tools. Low-cost coated carbide inserts can realize low speed when turning the work piece which hardness was under HRC45.

Part 2 Ceramic material inserts

The turning speed of ceramic inserts is 3-5 times faster than carbide inserts with normal machining. Ceramic inserts is especially suit for processing hardness materials with high speed, finishing process and high speed process. We can choose ceramic inserts to finish turning hardened steel with hardness HRC45~HRC55,and had better avoid interrupted turning.

Part 3 CBN(Cubic Boron Nitride) material inserts

The CBN hardness and wear resistance are second only to diamond, has a wonderful hot hardness, and also has a better impact strength and breakage resistance compared with ceramic inserts. It is widely used for turning the Hardened steel (more than 50 HRC), pearlite gray cast iron and chilled cast iron and high temperature alloy. CBN inserts has a much higher cutting speed than carbide inserts.

PCBN inserts with high content CBN is harder, better wear resistance, better compressive impact and toughness ,but its defect is low thermo stability and chemical inertness, which is suitable for machining heat resistant alloy, cast iron and iron series sintered metal. CBN particle content in the composite PCBN cutting tools is low, using the ceramic as binder, which hardness is low, but make up for the before one materials defect which low thermal stability, chemical inertness, PCBN used for machining hardened steel.

Part 4 Summarize

We can choose both ceramic and CBN inserts when machining hardened steel, you can analyze the producing cost and machining quality so that which one is more economical. PCBN material cutting tools has a better performance than Al2O3 ceramic inserts, and the latter has a better thermal chemical stability. But PCBN inserts has a better toughness. Generally, ceramic inserts will be better choice when machining the hardened steel work piece with hardness less than HRC50 with thin cutting depth and small feed rate. while PCBN tool is suitable for machining the work piece with hardness above 50 HRC, especially for automation and high precision machining .In addition , with the same blade wear, PCBN cutting tools has a better stable residual stress than ceramic inserts after they stand the same wear of the cutting tools flank cutting surface. In addition, ceramic inserts should avoid using for roughing and semi-finishing, Halnn company developed integral CBN inserts can be suitable for interrupted turning , hard roughing the hardened steel overloading.

Interrupted turning hardened steel cutting tools--- BN-H21 grade CBN inserts

As we all know, the hardness of hardened steel work piece is high, and difficult to machine, especially for interrupted turning condition, so the requirements on the cutting tools materials improve gradually.

In current times, the materials of machining hardened steel include carbide alloy, ceramic and CBN cutting tools, but because of high hardness of hardened steel, it only suit for CBN inserts .

Hardened steel work piece usually belongs to finish turning after heat-treatment,has small working allowance,and it will be more economical with soldering CBN inserts.But some hardened steel exist interrupted turning condition,such as turning key seating or oil bore on the surface of the work piece.In the process,CBN inserts are easily chipping,so many manufacturers are difficult to guarantee the precision and durability for interrupted turning hardened steel.

But as the manufacturing required product quality increase gradually,it not only require the work piece high precision,but also require product quality improved.Hardened steel,as one of the most common parts in manufacturing is the most important factor which cutting tools enterprise need value.

As a professional CBN inserts manufacturer, Halnn has good development in the following areas: high hardness cast iron/steel, high hardness steel after heat-treatment, cast iron, ect.

Now,as the increase of hardened steel interrupted cutting condition work piece, we researched BN-H21 grade CBN insert which can interrupt turning hardened steel work piece ,and already has good development in gear industry.

Application case as follows: 

1.Workpiece information:

Name: Gear

Hardness:HRC53~61

Other information:φ97.02 ,Depth30mm

Process: finish turning inner bore

Machining condition: semi-interrupted turning

Precision requirement:Ra1.6

Tolerance: +0.02

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2.The cutting parameters of BN-H21 CBN insert interrupt turning gear inner bore

Inserts model:BN-H21 CCGW09T304-2S

Cutting Parameters:

N=500r/min;ap=0.08~0.12mm;Fr=0.08mm/r

Cutting Type:Dry Cutting

Working Efficiency:one cutting edge can machine 180~200piece work piece, and continue working about 3 hours. And guarantee the tolerance and precision requirement, and approval by customers .

More information:http://www.halnntools.com/pro/PCBN_inserts/DNMG.html