The hottest coated high speed steel tool

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Coating high speed steel cutting tools

1 overview

the performance of high speed steel cutting tools can be greatly improved by coating a thin layer of wear-resistant material on the substrate of high speed steel cutting tools by physical vapor deposition (PVD) Generally, tin and tic are used as coating materials, but tin is mostly used. After coating, the surface of the tool is golden yellow. The coating thickness is 5 ~ 10 m

coated high-speed steel knives appeared in the international market around 1980. It has developed very rapidly. In the past 20 years, it has occupied a certain proportion in high speed steel cutting tools. In the United States, Japan and Germany, nearly half of gear cutting tools, end mills and drill bits are coated, which improves the cutting efficiency and obtains significant economic benefits. The research on coated high speed steel cutting tools in China began in the 1980s. In the past decade, the tool manufacturing industry has introduced nearly 10 sets of PVD coating equipment from the United States and Japan, and has sold all kinds of 1. the universal material testing machine is installed in a clean, dry house with uniform temperature. At the same time, the possibility of long beam zigzag test on the machine and the possibility of using a mirror extensometer to test coated high-speed steel tool products should be considered. In various regions and departments, there are a large number of domestically manufactured coating equipment. The physical vapor deposition methods used are different, including arc generated plasma vapor deposition method, plasma gun launched electron beam ion plating method, hollow cathode gun launched electron beam ion plating method, e-gun launched electron beam ion plating method, etc. each has its own characteristics, advantages and disadvantages, and the coating product quality is also different, Arc generated plasma vapor deposition is the most widely used method

2 advantages of coated HSS Cutters

tin has a hardness of hv1800 ~ 2000, a density of 5.44g/cm2, a thermal conductivity of 29.31w/(m ·℃), and a linear expansion coefficient of (9.31 ~ 9.39) ×/℃。 The hardness of high speed steel matrix is only HV800 ~ 850. Therefore, the coated high-speed steel tool has a hard layer on the surface, good wear resistance, small friction coefficient with the processed material, and the toughness of the base material does not decrease. The practical application shows that the cutting force of coated HSS tools can be reduced by 5 ~ 10% compared with uncoated HSS tools. Due to the thermal barrier effect of the coating material, the cutting temperature of the cutting part of the tool matrix is also reduced; The machined surface roughness of workpiece decreases; The service life of the tool is significantly improved

3 cutting experimental data

the author used W18Cr4V or W6Mo5Cr4V2 high-speed steel turning tools and coated tools to carry out cutting experiments to control heavy vehicles, mainly comparing their tool wear and service life

Experiment 1: workpiece material: 60Si2Mn (quenching and tempering, hrc40)

geometric angle of turning tool: go=16 °, ao=8 °, kr=45 °, le=-4 °, be=0.5mm

cutting parameters: ap=0.5mm, f=0.2lmm/r, ν= 25m/min dry cutting

wear curve is shown in Figure 1

Fig. 1 the wear curves of coated and uncoated high-speed steel turning tools are designed and developed in full accordance with the airworthiness standards in line with international standards and airworthiness certification

Experiment 2: workpiece material: 60Si2Mn (quenched and tempered, hrc40)

geometric angle of turning tools: go=10 °, ao=8 °, kr=45 °, le=0 °, be=0.5mm

cutting parameters: ap=o.5mm, f=0.21mm/r, ν= 25m/min, dry cutting

wear curve is shown in Figure 2

Experiment 3: workpiece material: 38crni3mova (quenching and tempering, hrc36 ~ 40)

geometric angle of turning tool: go=8 °, ao=8 °, kr=75 °, le=-4 °, be=0.8mm

cutting parameters: ap=1mm, f=0.2mm/r, vb=0.5mm, dry cutting

t-v curve is shown in Figure 3

Figure 3 T-V curve of coated and uncoated high speed steel turning tool

in Figure 3, t- ν Taylor equation of the formula is as follows:

v=58/t0.37 (W18Cr4V) v=57/t0.21 (w18cr4v+tin)

where: V - cutting speed, m/min

t - tool service life, min

it can be seen from Figure 1 to figure 3 that the service life of coated high-speed steel tools is 2 ~ 3 times that of uncoated tools, or even more

4 use experience

coated high-speed steel tools can be used for turning tools, milling cutters, drills, reamers, taps, broaches, gear hobs and gear shapers. The service life of the tools varies. In fact, this description is not particularly accurate. Coated high-speed steel turning tools are seldom used, and the improvement of their service life is not the most significant. Coated high-speed steel fried dough twist drills, end mills, taps and other tools are most widely used, and their service life is significantly improved. After regrinding, the coating still works. For example, when coated high-speed steel bits are used for the first time after coating, their service life can be increased by more than 3 times compared with uncoated bits; During regrinding, the coating on the rear blade surface has been removed, but the coating on the front blade surface is still retained, and the service life can be increased by more than 2 times; After the second regrinding, the service life of the tool surface is still improved to a certain extent. For the cutting tools (such as coated gear hobs and gear shapers) that sharpen the rake face, the service life of the cutting tools can still be prolonged after sharpening

coated HSS tools are not widely used in China. However, it can certainly be said that it will play an important role in cutting difficult materials and in advanced manufacturing equipment (such as CNC machine tools and machining centers). (end)

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