As we all know, the general failure form of the blade during processing is normal wear, so the life of the blade is closely related to wear resistance. After demonstration, the life of the cubic boron nitride blade is generally several to dozens of times that of the carbide blade and the ceramic blade. In addition to its own performance and quality, the life of the cubic boron nitride blade is also closely related to the material of the workpiece, the amount of machining, the machining speed, etc. Therefore, it is necessary to understand the relationship between the life and performance of the cubic boron nitride blade, correctly apply the cubic boron nitride blade, improve the machining efficiency, and reduce unnecessary machining waste.
Comparison of the Life of Cubic Boron Nitride Insert and Other Materials
When using superhard cubic boron nitride circular blades to process HRC55 chilled cast iron at a cutting amount of Vc=40 m/min and f=0.16 mm/r, the tool life is 500 min, while when using ceramic blades, the blade life is only 5 min. The durability of cubic boron nitride blades is 100 times that of ceramic blades. The cubic boron nitride integral polycrystalline blades developed by Henan Institute of Superhard Materials have begun to be used in heavy-load roughing.
Cubic boron nitride blades have begun to be used in roughing with large feed and large depth, and the removal rate is higher than that of cemented carbide blades. For example, using cubic boron nitride blades to cut chilled cast iron rolls can achieve extremely high metal removal rates. For example, when Vc=61 m/min, αp =/mm, and f=0.94 mm/r, the metal removal rate reaches 400 cm3/min, and the blade is almost not worn.
Superhard cubic boron nitride blades are used to process gray iron brake discs. Cutting parameters: linear speed 600M/min. The blades are 2 times more efficient than carbide blades, and their lifespan is 6-12 times longer in roughing. Their lifespan is 15-20 times that of carbide blades in finishing.
Relationship Between CBN Insert Grade and Performance
The performance of cubic boron nitride blades is closely related to the grade of cubic boron nitride blades. The particle size, content and type of binder of CBN directly determine the performance of cubic boron nitride blades. Each manufacturer has also woven its own cubic boron nitride blade brand based on performance and composition. Although each has its own comparison, it is generally not universal.
Cubic boron nitride blades can be roughly divided into two categories according to their organization. One type is directly sintered from CBN grains without adding a binder. It has a high CBN content (more than 70%) and high hardness. It is suitable for cutting of heat-resistant alloys, cast iron and iron-based sintered metals. The other type is made of CBN grains as the main body and sintered by ceramic binders (mainly TiN, TiC, TiCN, AlN, Al2O3, etc.). This type of cubic boron nitride blade contains little CBN (less than 70%). Low hardness, suitable for cutting hardened steel.
Subdivision of cubic boron nitride blade grades: Superhard CBN is divided into finishing and roughing according to the specific CBN particle size. The decisive factor for subdivision is the CBN grains in the cubic boron nitride blade.
CBN Grain Division of CBN Inserts
The grain size of CBN can be roughly divided into three categories: coarse grains (the average grain size is 20~50μm), medium grains (10~20μm) and fine grains (2~10μm). The larger the grain size, the better the wear resistance and the longer the blade life, but the edge quality is poor and it is difficult to make high-precision blades. On the contrary, fine-grained cubic boron nitride blades have good cutting edge quality and good processing surface quality. Therefore, the grains of polycrystalline are constantly refined, and there are already fine grains of 1μm and even below 0.5μm. Different sizes of grains need to be selected according to different process requirements such as roughing and finishing.
CBN Insert Grades Corresponding to the Workpiece Range
At present, cubic boron nitride blades do not have a unified classification internationally like cemented carbide. Each manufacturer has its own varieties and brands, and you must refer to the manufacturer’s product samples when using them. According to the material, it is subdivided into: high chromium cast iron, white cast iron, austempered ductile iron, high temperature alloy, powder metallurgy, gray cast iron, hardened steel processing, etc. Combined with the CBN grain size required for the processing conditions (roughing, semi-finishing, finishing), it is refined into a series of cubic boron nitride blade brands.
Different cubic boron nitride blade brands have very different cutting performances due to their different components, so you must pay attention when selecting them.
Judgment of the Quality of CBN Inserts
Judging from the use perspective, good quality cubic boron nitride blades have two major characteristics:
- Good impact resistance, especially in the field of rough processing, no chipping or breaking during use. This is the most basic guarantee for the safety of cubic boron nitride blades.
- Good wear resistance, efficient processing, and can replace carbide blades and ceramic blades at a low cost. This is the guarantee of the economical use of cubic boron nitride blades.
Dialectics of Insert Wear Resistance and Toughness
It is not difficult to simply improve the hardness and wear resistance of cutting tools. However, as the hardness of the tool material increases, the toughness will decrease. Therefore, during use, it is necessary to comprehensively consider the workpiece material, machine tool system, and processing conditions to avoid the contradiction between the two to the greatest extent and make comprehensive considerations in selection. In view of the characteristics of cubic boron nitride blades, we have launched a brand of cubic boron nitride blades suitable for low-speed cutting and heavy-load rough machining. The impact resistance of the blade is far ahead of the entire superhard tool industry. It enjoys a high reputation in the tool academic community at home and abroad.
Efficient Machining does Not Mean High-speed Machining
Indeed, when processing ferrous metals, cubic boron nitride is undoubtedly the hardest blade material. So when it comes to cubic boron nitride tools, everyone will fall into a misunderstanding: “High hardness, poor toughness, only suitable for high-speed cutting or high-precision machine tools”, but this is not the case. “High-efficiency processing does not mean high-speed processing”, no matter how high the hardness of the cubic boron nitride blade is, the tool life will decrease within a certain range as the line speed increases, and the life will decrease.
By increasing the depth of cutting and the amount of cutting, the work efficiency can be improved, which is more suitable for the processing of some difficult-to-process materials. Facts have proved that this concept does solve the actual processing problems of users. The CBN series of cubic boron nitride blades do not break the blade while processing efficiently, especially in the field of intermittent cutting of difficult-to-process materials. This is the greatest success in the superhard tool industry.
