Application and effect of the hottest CBN tool gri

2022-08-18
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The application and effect of CBN tools (grinders) in machining

in the past five years, the sales situation of the German tool industry, in addition to normal fluctuations, the general trend has continued to rise, but the supply period of products has been extended. With the further improvement of the economic situation, we must speed up the development of new products and pay attention to the research and development work related to the future of the tool manufacturing industry. So that the manufacturing industry can apply more efficient cutting tools after 2000

so, what are the most important topics for the tool industry at present? The following ten aspects can be listed:

(1) how to process new workpiece materials

(2) about hard dry high speed machining

(3) cemented carbide with electrophoretic deposition process and gradient structure

(4) about multilayer coating and nano coating

(5) about lubricating coating and micro lubrication technology

(6) disposable tools

(7) intelligent tool

(8) provide cutting technology with management function

(9) the impact of interconnection on the tool industry

(10) the relationship between patented technology and popularization

what kind of workpiece materials should the new tool process

in the next decade, what kind of workpiece materials should the newly developed tool process? We can get a clear answer from the two industrial sectors that are most closely related to the tool industry -- the automotive industry and the aviation industry

in the automotive industry, aluminum alloy plays a leading role. Figure 1 shows the change trend of workpiece material composition of Volvo automobile factory in Sweden. Aluminum alloy is also the main material for manufacturing aircraft fuselage. In the aircraft engine manufacturing industry, in addition to aluminum alloy, the main materials are nickel based alloy and titanium based alloy. Figure 2 shows the change trend of workpiece material composition of Volvo aircraft engine factory in Sweden. In addition, the composition pattern of the above materials is also changing, and it is expected that vermicular graphite cast iron (GGV) and magnesium alloy will play an important role in the future

Table 1 shows the comparison of the properties of these two materials with ordinary gray cast iron (GG) and aluminum alloy, which will affect the efficiency of cutting and the service life of cutting tools

a gray cast iron B nodular cast iron C forged steel D aluminum alloy e other a steel B aluminum alloy C cobalt base alloy D nickel base alloy e titanium alloy f synthetic materials Figure 1 development trend of workpiece materials in car industry figure 2 development trend of workpiece materials in aircraft engine industry

Table 1 Comparison of material properties workpiece materials gray cast iron gg25 GGV cast iron (70% pearlite) GGV cast iron (95% pearlite) Aluminum alloy alsi9cu3 magnesium alloy AZ91HP strength MPa 230 440 480 255 225 modulus of elasticity GPA 130 145 145 74 45 hardness HB 190 200 250 10072 gross weight of cylinder head kg 40.4 303027.5 21.5 net weight of cylinder head kg 35.2 24.5 24.5 2217

hard dry high speed cutting: Ten related technologies of dry cutting

hard processing, mainly refers to the processing of carburized quenched steel. See Table 2 for the technical level that can be achieved at present. The most important trend in current manufacturing technology is definitely dry cutting. The following is a list of the ten most important related technologies for the economic application of this technology:

(1) only the universal dry or quasi dry cutting process is valuable. Because there is a high cutting temperature in the cutting area of hole machining (drilling, tapping, reaming), hole machining is the key to the universality of dry cutting. Flange ball valve

(2) a new special tool geometric angle must be used to reduce the friction between the tool and the workpiece, which is conducive to the flow of chips

(3) the tool material should be suitable for grinding a sharp edge to reduce the cutting temperature

(4) adopt multi-layer coating containing TiAlN to prevent heat from entering the tool

(5) reduce the friction of chip flow with antifriction coating

(6) the external micro lubrication method is simple and effective only for the processing of infrequent tool replacement

(7) for machining center machine tools that frequently change tools, it is necessary to adopt the internal micro lubrication supply mode of spindle tool

(8) there should be a device to suck chips and oil mist

(9) machine tools suitable for dry cutting should be conducive to the falling of chips and can quickly remove chips from the processing area. The movement of the workbench has a high acceleration (deceleration) speed to provide the best feed speed

(10) a high cutting speed must be adopted so that the heat can be taken away by the chips

Table 2 technical status of hard cutting (provided by Hannover University of Technology) ceramic, ultra-fine particle cemented carbide for CBN hard turning +tin coated ultra-fine particle cemented carbide for hard milling +tialn coated hard milling cutting speed VC (m/min) 120 ~ 250 200 ~ 350 40 ~ 60 feed rate f mm the bid price is nearly 1.5 ~ 0.15 0.1 ~ 0.2 0.02 ~ 0.1 roughness Ra μ M 1 ~ 42 ~ 52 ~ 4 Precision it5 ~ 7 it7 ~ 10

Figure 3 development prospect of dry cutting in German machinery manufacturing industry

several of the above ten articles need to be further explained, the most important of which is Article 10, because its advantages are of practical significance and widely used only when dry cutting does not reduce productivity. Practice has proved that dry cutting must improve the cutting speed so that the heat can be taken away by the chips. The actual situation was better than expected, and the productivity not only did not decrease, but even increased. Experts have different opinions on how fast this technology will be promoted. Figure 3 shows the proportion of dry cutting in German machinery manufacturing industry: currently 6%, by 2003, the best estimate is 40%, while the realistic estimate is 20%

in order to speed up the promotion of dry cutting, the practice of Germany's second largest automobile manufacturer can be used for reference. The principle of its project implementation arrangement is:

where the energy consumption of 100 million tons of standard coal can be reduced, the process of dry cutting can be adopted, and the machine tool suitable for dry cutting must be input, otherwise the processing can be carried out according to the following principles:

① first, micro lubrication should be used to see whether the processing is feasible

② if cooling must be used, emulsion should be given priority

③ use oil cooling only when forced

with regard to the development of dry cutting machine tools, at least 12 machine tool plants have been able to provide newly developed machining centers suitable for dry cutting or will launch prototypes in the near future

cemented carbide that can replace high-speed steel and welded PCD

at present, the dominant cutting tool materials in the market are still in the traditional pattern: class P is used for processing steel, and class k is used for processing cast iron and aluminum alloy. Such a pattern is going out of date. The advantage of p-type cemented carbide is that it can not be recoated after regrinding when processing steel. In fact, this advantage has become irrelevant. If coated ultra-fine particle cemented carbides are used, compared with p-type cemented carbides, the increase in life before regrinding far exceeds the loss of life after regrinding, so the total life is greatly improved, as shown in Figure 4

in order to improve the toughness of cemented carbide, the content of cobalt is usually increased, and the resulting reduction in hardness can now be compensated by refining the particle size (see Figure 5), so that ultra-fine cemented carbide is favored. Especially in the case of poor rigidity of machine tools or unstable processing conditions, if ordinary cemented carbide tools are used, sooner or later they will cut. Figure 6 shows the crankshaft oil hole drill made of ultra-fine cemented carbide, with a hole depth of 25d, representing the current highest level of such tools

a tin coating B after regrinding Figure 5 hardness and strength of class k cemented carbide Figure 4 Comparison of tool durability between k40uf and P40

Figure 6 crankshaft oil made of ultra-fine particle cemented carbide is respectively installed on the upper and lower collets of the experimental machine to drill holes Figure 7 gradient cemented carbide k40uf metallographic structure

another advantage of fine particle cemented carbide is that the cutting edge of the tool is sharp, which is suitable for processing those very sticky workpiece materials. High strength and sharp edge experiments show that the cutting edge can replace high-speed steel tools even in the case of poor processing conditions, so that the application range of cemented carbide tools is more extensive

although the hardness and strength of hard gold made of Nano fine particles have reached the highest value, the price is too expensive. Therefore, a gradient performance cemented carbide material with tough core and hard surface was developed (Fig. 7). At present, this material can only be made of coarse grained cemented carbide. Such continuous (stepless) gradient structural materials are very suitable for manufacturing cutting tools with constant cutting edge arc (such as end mills and reamers)

for tools with end edges, such as drill bits and taper milling cutters, their transverse edges wear quickly. For this, electric pulse deposition can bring a breakthrough. This technology can change the ratio of toughness and hardness of the coating at a very small rate of change. It can deposit particles with gradient properties on the surface of any shape of the tool. When dense diamond coatings can be deposited, welded diamond tools will be eliminated because of their high price, adverse environmental protection, and unstable welding quality in complex shapes

can multilayer coatings and nano coatings replace tin

in all kinds of coatings, tin coating is dominant, and the latest coating research exploration combines the three most important advantages of tool coating

the multi-layer coating with tin as the bottom layer can ensure the best performance of the coating. The production efficiency of this coating is also not low, because the etching and coating processes can be partially carried out at the same time. TiAlN and tin multilayer structures deposited on tin substrate have the best effect on crack absorption. In multi-layer structure, the greater the change between layers, the better the effect of changing the direction of cracks, thus increasing the path of crack propagation to the matrix

at present, the surface layer of multi coating is generally TiAlN, because TiAlN has the lowest thermal conductivity. In addition, because the oxide formed on the surface of TiAlN is corundum, it has higher strength than the oxide formed on the surface of tin

the multi-layer coating must adopt the once denied multi arc process. The productivity of the multi arc process is not a problem. The problem is the large particles in the coating, which will hinder the flow of chips, so it is not suitable for coating deep hole machining tools

in order to quantitatively evaluate the influence of such particles, the concept of coating slip coefficient is introduced to reflect the influence degree of particles in the coating. The method is to analyze the feed force measured during drilling and express it with the corresponding drilling depth. By improving the etching process and using the multilayer structure of small particles, the sliding performance of multi arc coating can be greatly improved. At the same time, the sliding performance of the coating can be improved by self polishing effect. After solving the particle problem of multi arc coating, multi-layer coating can greatly improve the processing efficiency compared with the usual tin coating

nano coating further improves the hardness and wear resistance of tools, so it is possible to abandon the use of welded CBN and PCD tools in the future. The technology of nano coating has been mastered, that is, to control the discharge time and the rotation speed of the coated tool, so that the two can be accurately synchronized. However, the practicality of nano coating is also limited to the batch coating of tools with the same geometry

those coating companies that operate independently usually deal with different workpieces at the same time, so they cannot paint nano scale. For these companies, the most important thing is to develop practical recoating technology. At present, many coating companies do not master the technology of de coating and particle refinement. Therefore, its main business will be simple repainting for a long time in the future

a more promising coating process is ion implantation (PII). Its principle is to strengthen the lattice through the bombardment of metal ions, so as to improve the hardness without changing the size of the tool, which is very beneficial to the finishing tool. Combining the existing process with ion implantation can produce a new coating, that is, first of all, ion implantation is used to generate a coating on the substrate as a later common coating

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