Green cutting affects the development direction of tool technology

It is clear that changes in cooling methods are also changing the tool to adapt to the new cutting environment. What changes need to be made to tools that adapt to green cutting technology? Wu Jiang, technical director of Iskar Tool International Trading (Shanghai) Co., Ltd., said in an interview: “Green cutting technology is affecting the development direction of tool technology. In order to meet the demand of green processing, tool companies need to develop new tool materials and pay attention to tools. Reasonable matching of materials and workpiece materials and prevention of diffusion and bonding of tool materials and workpiece materials during cutting."

Reporter: Compared with traditional tools, green cutting tools, especially dry cutting tools, will have more new technical requirements. What are the technical requirements of these tools?

Wu Jiang: Green cutting tools not only involve tool materials, tool coatings, but also tool geometry, tool holder structure, machine tools, cutting amount, machining methods, etc., and need to consider tool materials, coating materials, and geometric shapes. And the mutual consideration and optimization between the three. ”

In terms of tool geometry, the tool design should follow the "low cutting temperature" design principle. The tool structure design must consider the heat generated during the machining process as little as possible, that is, the tool structure stress should be low cutting force and low friction. . For example, the chip flute contour design of the tool should ensure the flow of low friction chips to reduce the friction between the cutter and the chip during processing, which makes the chip removal convenient and quick, and reduces heat accumulation.

In addition to studying the hardness, toughness and thermal stability of tool materials, it is also necessary to consider the adaptability of different tool materials in cutting, the role, characteristics and performance of different materials in cutting. Tool geometry parameter design, blade shape and geometric parameters are reasonably determined, which is very important to give full play to the cutting performance of the tool. Therefore, we are constantly developing a blade shape with higher strength and a more secure blade clamping method, considering the adjustment of the mass distribution of the tool body. Reasonable, so that the knife body expands evenly and so on.

For geometric parameters, we emphasize the principle of low cutting force and low cutting temperature. It is worth pointing out that the design of the tool structure and tool geometry is related to the tool material, the material of the workpiece to be processed, the cutting process parameters, the machine tool conditions, the cooling method, etc., and it is necessary to go through certain process tests before it can be used for production. Optimized value.

In dry cutting, the softening theory of the metal cutting layer is an important aspect. A sharply rising cutting temperature during the cutting process causes a decrease in tool life, but at the same time, the high temperature causes the shear strength and tensile strength of the material to be processed to decrease, the cutting force is lowered, and the tool life is increased. To benefit from these two aspects, it involves the working conditions of various factors such as working materials, tool materials, and cutting elements. This is our concern and research.

Reporter: Dry cutting is a green cutting technology that is currently used more and more mature. To achieve dry cutting, what technical requirements do the tools need to meet? What efforts has Isa made in this regard?

Wu Jiang: Dry cutting is a revolution in traditional production methods. This advanced manufacturing technology has become the main direction of metal cutting. To achieve dry cutting, the tool material must have excellent thermosetting and wear resistance, which can effectively withstand the high temperature of the cutting process; a lower friction coefficient can reduce the friction suppression between the tool and the chip and the workpiece surface. The rise in temperature; higher strength and impact resistance, can withstand greater cutting forces and worse cutting conditions. At present, tool materials such as cubic boron nitride, polycrystalline cubic boron nitride, diamond, polycrystalline diamond, ceramic, cermet, ultra-fine grained carbide and hard alloy coating have been widely used in dry cutting.

Conventional tools are not suitable for dry cutting. For this reason, dry cutting should optimize tool geometry, which requires the tool to have a large rake angle and fit the appropriate cutting edge shape. Such as ISCAR's various milling inserts -PDR and -PDR HM groove type, the use of zero-degree small diamond blade and double positive rake angle design, which reduces the cutting force and strengthens the strength and heat capacity of the cutting edge. In order to reduce the heat of cutting, ISCAR provides reinforcing ribs on the rake face of the car blade, groove blade and milling insert, which can form a scaly cutting surface in the contact area. The contact area between the tool and the chip is greatly reduced, and most of the heat is chipped. Take away, the cutting temperature is greatly reduced compared with the ordinary blade, and the shear angle is also increased, so that the tool life is significantly improved.

In the past two years, ISCAR has developed a number of tool materials for dry cutting: IB90 and IB85 with high wear resistance and toughness, and CBN content of 85% and 90%, which can cope with the vibration caused by interrupted cutting. Correspondingly, grades IB55 and IB50 with low CBN content are more suitable for semi-finishing and finishing. ISCAR's IS6 is the new Sailong SiAlON ceramic, which complements the existing ceramic grades IS8 and IS80. The Sailong SiAlON ceramic grade has high hardness, anti-crushing, excellent heat resistance and can achieve ratio SiN-based ceramics have higher cutting speeds for high-speed roughing of cast iron.

Reporter: Coating tools that are being widely used have many advantages in cutting processing. What changes have been made to the coating technology for green cutting?

Wu Jiang: Coating tools combine high hardness and wear resistance, high heat resistance, high toughness, high anti-blocking performance, high chemical stability and low coefficient of friction. Generally, coatings are divided into coatings. Hard coatings and "soft" coatings come in two broad categories. The “soft” coating refers to the anti-friction coating such as chalcogenide M0S2 or WS2 or TaS2, which can significantly reduce the friction coefficient. Such coating tools are also called “self-lubricating tools”, and such coating tools are to some extent It compensates for the lubrication of the non-cutting fluid and resists the rise of the cutting temperature, making it suitable for green cutting.

ISCAR places special emphasis on the development of coated tools. ISCAR's IC908, IC907, and IC903 use ultra-fine grained carbide with good mechanical shock and thermal shock resistance as the matrix. The high temperature resistant material TiAlN is coated by a PVD coating process with a lower coefficient of friction. The friction between the workpiece and the chip reduces the heat generation. In addition, the TiAlN coating also acts as a heat insulator, allowing the tool to withstand higher temperatures during dry cutting. With the increase of A1 content, PVD-TiAlN coating has higher hardness, higher resistance to high temperature fracture, high hardness and wear resistance, and the oxidation temperature is unchanged, so ISCAR has developed a higher Al ratio. The PVD-AlTiN coating Al-TEC IC908, Al-TEC IC900, Al-TEC IC903, Al-TEC IC910 is particularly suitable for green cutting.

In the past two years, ISCAR has applied ultra-thin TiN and TiAlN to alternately coat the tools. The coated tools have strong adhesion, high heat resistance and good wear resistance, and they are concentrated in TiN, TiAlN and TiNC. The advantages of the coating, and then the post-treatment technology SUMO-TEC, further improve the toughness and wear resistance, reduce the surface friction coefficient, make the cutting area lower temperature, anti-cracking and anti-chip-forming properties, This results in a more reliable and long-lasting tool life when machining most of the material being processed, and blade durability is increased by 20% to 280%. This is the new material grades IC808, IC807, IC830, IC380, IC5005, IC5010 and IC8080, etc., which provide more and better tool materials for green cutting.