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Halnn CBN inserts machine forged steel cold roll

Forged steel cold roll, as one important tool for cold-rolled plate and Non-ferrous metal, has high hardness, strength, good ductility and impact toughness. So it has a big difficult problem on turning forged steel cold roll. Halnn researched BN-S20 solid CBN inserts which can machine forged steel cold roll.

Part 1 The reasons of forged steel cold roll difficult to machine
With the fast development of automobile, petrochemical, construction, railway and other industries, the demand for cold-rolled sheet always are rising, and because forged steel cold roll belongs to consumables, so we usually use 9Cr2Mo,86CrMoV7,Cr3,Cr5 and Cr8 as main cold roll materials. And chilled rolls need hear-treatment, roughing which will be machining easily because of low hardness, but if semi-finishing and finishing after modulated are usually difficult to cut, and modulated part can easily deform and hardness is higher. So it will have problems of non-wear-resistance.

Part 2 The problems and solutions when machining forged steel cold roll
In the process of machining forged steel cold roll, it exist 2 big problems:
1.cutting tools wear;
2.Cutters Crack

The following we will offer solutions about above problems.
1. The tool wear fast reasons and solutions
(1) The tool wear fast main reasons:
The selection of the cutting tools materials and the choice of the cutting parameters

We will introduce the selection of the cutting materials first
In current times, there are carbide tools, ceramic cutters and CBN inserts for machining forged steel cold roll. The hardness of carbide tools itself is between HRC71 and HRC76, so it will burn inserts easily causing wear block and lower processing efficiency. This is the reason what many machine manufacturers said; Ceramic cutters have big brittleness, which is the reason of easily crack in the process, so ceramic tools only suit for small allowance finishing and small cutting depth. However the average hardness of CBN inserts is above HRC98.5, it is the most wear-resistant materials for machining ferrous metals, and suit for machining high hardness (above HRC45) forged steel cold roll. After a demonstration, the lifetime of CBN Inserts usually is several times of carbide tools and ceramic cutting tools.

For example, Halnn BN-S20 solid CBN inserts, which not only interrupt cutting hardened steel, but also can large allowance cut the workpiece quenched layer, and achieve the perfect balance of wear resistance and impact resistance.

The tool wear fast second reason—the selection of the cutting parameters:
(1) Cutting Speed Vc related most with cutting tools durability, and related with interrupted turning and Machine rigidity and kept the machine stable. And the linear speed should not be high, we usually use the method of observing the cutting color and cutting edge temperature, if cutting edge appear red color, and chips appear Fuchsia, that means the linear is a little high.
(2) Cutting Depth ap related to workpiece allowance.
(3) Feeding Rate suit for Cutting Speed. When machining forged steel cold roll, only we use well all the machine itself condition, and improve CBN inserts, cutting edge conditions, and improve the cutting parameters, which can be machining stability to machining forged steel and chilled rolls.

The reasons of causing cutters crack and solutions
The reasons of causing cutters crack:
(1) Improper operation
(2) Rolls neck brake cutter
(3) Not timely change tool.
And the improper operation include united passes: the handle did not hang the right place or  didn’t observe the trial cut situation ,causing united passes ,then brake the cutters; And the low hardness materials ,and cutting parameters will be high ,and if choose 90 degree inserts ,any accident will cause cutters crack because of high metal removal rate
Cutters Crack is the most common and main default for machining forged steel cold roll, the suitable cutting parameters is one of the important factors to make sure the product quality. For example, when machining forged steel cold roll, the cutting depth need be high, feed rate need small, if the inserts thickness is high, cutting depth and feed rate can be high.such as BN-S20 SNMN120712 cutting depth 7.5mm; BN-S20 CNMN120408 Cutting Depth 1.5mm;BN-S20 RNMN120400 Cutting Depth 2.5mm.

Part 3 The inserts grade and machining effect of Halnn superhard machining forged steel cold roll
(1) For example: machining Sweden forged steel cold roll (HRC67):BN-S20 grade CNC inserts cutting depth 4-7mm,linear speed 90m/min, the lifetime is 2.5 times of some foreign brand CBN inserts.
(2) When turning restored 9Cr2Mo cold work roll, we use BN-S20,also can get good effect, lifetime is more than 4 times than domestic CBN inserts ,and Chapped parts will not chapping, make sure the use safety and economy.
(1) Use Halnn BN-S20 grade CBN inserts, choose reasonable inserts angle can shorten the processing time and improve the work efficiency.BN-20 grade CBN inserts, compared with other Halnn CBN inserts grade, has the best toughness, can cut at a brisk 0.2 * 20 degree chamfer, and can restore irregular surfaces of forged steel cold roll.
(2) Choose reasonable tools angle and cutting parameters (turning instead of grinding or roughing quenched steel cold roll), Correct operations can solve the cutters crack problem of forged steel cold rolls.

Part 4 Conclusion
As the Rolling steel manufacturer production rising, and strict requirement on the rolls performance, causing problems for machinery manufacturers ,and workpiece difficult to machine ,they can’t find suitable cutting tools materials ,affected the development, which is a challenge and opportunity for cutting tools industry .only researched high hardness ,high quality and high efficiency cutting tools or cutting tools materials , can get a place in tool industry and promote the development of machines.

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