Honing surface quality of the hottest engineering

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Honing surface quality of engineering ceramics

engineering ceramic materials have broad application prospects in engineering because of their excellent mechanical properties. Hole type ceramic parts are being used in many industrial fields. Ceramic engine without cooling system adopts ceramic cylinder block, which can improve fuel utilization and driving efficiency by adding 22.35.1 (1) in January last year, and reduce fuel consumption. In oil drilling equipment, the service life of the mud pump cylinder liner made of ZTM (zirconia toughened mullite) ceramic material is more than three times that of the cemented carbide cylinder liner, which greatly improves the working life and reliability of the mud pump. In addition, ceramic bearing sleeve and ceramic plunger sleeve for textile are all used in industry

honing is often used for finishing the inner hole surface. At the same time, it is an efficient machining method, which can remove large allowance and is suitable for machining precision coupling parts with high relative motion accuracy. With the application of diamond and other superhard abrasives, honing of high-performance ceramic materials will occupy a large proportion in the future. Honing is the best choice for machining hole parts such as ceramic engine cylinder (mg PSZ, TZP), ceramic sediment pump cylinder (ZTM, Al2O3) and ceramic bearing sleeve (hpsn, RBSN). One of the main research topics of honing engineering ceramics is how to improve the processing quality and give full play to the excellent properties of materials. In this paper, the honing surface quality of engineering ceramic materials is studied from two aspects of ceramic materials and honing tools, and the honing surface roughness and surface wear resistance are analyzed, And the addition amount is moderate. The main experimental conditions are as follows:

machine tool: m4215 vertical honing machine

specimen diameter: 65 mm

honing speed: 12.44 m/min

oilstone reciprocating speed: 4.8 m/min

oilstone working pressure: 0.24 MPa

oilstone overtravel: 20 mm

honing time: 3 min

cooling conditions: Kerosene + oil

grinder: mg1432a high.Precision universal cylindrical grinder

workpiece spindle speed: 140 r/min

wheel spindle speed: 10000 r/min

wheel model: 1a1/t2 30 × ten × ten × 3rvd 140/170 B 100

testing instrument: taylor-hobson-6 surface roughness instrument, UBM micro focal length surface roughness instrument

1 Analysis of honing surface quality of different ceramic materials

ceramics can provide doctors with telemetry load data. There are different types of materials, and their grinding surface roughness values are different. The surface roughness values of ceramic materials after machining reflect the grinding machinability of materials to a certain extent. Honing of ceramic materials has the same rule. Under the same experimental conditions, honing four kinds of ceramic materials: 95al2o3, ZTM, ztm/sicp and hpsn. Among them, the model of oilstone is SFH 72 × six × six × 2 RVD 230/270 B 75。 The experimental results are shown in Figure 1

Figure 1 Ra value of ceramic material surface

among the above materials, 95al2o3 material has the lowest strength and the greatest brittleness, which is easy to process. The material is removed in a brittle manner, and there are pits left by brittle collapse on the processing surface. In addition, the porosity of the material itself is high, so the surface roughness value after processing is the largest. The Ra value of 95al2o3 is 0.85 μ m. It is much higher than other ceramic materials. The strength and toughness of ZTM ceramic materials are improved by adding zirconia particles into Mullite Matrix, which is affected by the stress-induced phase transformation toughening mechanism and microcrack toughening mechanism, and the surface roughness value smaller than that of 95al2o3 can be obtained. Ztm/sicp ceramic materials, based on ZTM, add SiC particle dispersion phase, which has a strengthening and toughening mechanism dominated by crack deflection, so that the strength and toughness of ztm/sicp ceramic materials reinforced by particles are further improved. Under the same processing conditions, the probability of brittle fracture removal of materials is reduced, and the density of hot pressed sintered ceramic products is high. Therefore, the honing surface roughness value of ztm/sicp ceramic materials is low, It is basically close to hpsn ceramic material in value. It can be seen that when selecting honing process parameters of engineering ceramic materials, the influence of material factors of machined parts should also be considered

2 the influence of honing tools on the surface roughness of ceramic honing

the influencing factors of honing surface quality of engineering ceramic materials can be divided into two categories: honing process parameters and honing tool parameters. Among them, the influence of tool parameters is the most significant. Taking ZTM ceramic material as an example, this paper mainly investigates the influence of diamond particle size, concentration and binder on the surface roughness of honing engineering ceramics

2.1 diamond petrolatum particle size

diamond petrolatum particle size has an important influence on the surface roughness of ceramic materials after honing. Three kinds of oilstone abrasives are selected to hone ZTM ceramic materials. Among them, the concentration of resin bonded oilstone is 50%. The results are shown in the particle size comparison section in Figure 2. With the reduction of diamond oilstone abrasive particle size, the machining surface quality of ceramic materials has been significantly improved. The particle size of oilstone abrasive is fine, the interaction area between abrasive particles and ceramic materials is small, the cutting ability of abrasive particles is weak, the amount of material removal is small, and the grinding trace on the surface of ceramic materials is shallow. Therefore, the roughness parameter Ra value is low. When finishing engineering ceramic materials, fine-grained diamond oilstone tools should be selected to avoid scratches, so as to obtain qualified surface quality

Figure 2 Ra value on the surface of ZTM ceramic material

2.2 diamond oilstone concentration

three concentrations of diamond oilstone abrasives are selected to hone ZTM ceramic material. Among them, the particle size of resin bonded oilstone is 230/270. The results are shown in the concentration comparison part in Figure 2. The concentration of diamond oilstone is low, and the number of abrasive particles per unit area on the surface of oilstone is reduced, resulting in the non-uniformity of honing surface processing of ceramic materials. Moreover, the force on a single abrasive particle is large, and the ceramic material is easier to be removed in the form of brittle failure, leaving deep scratches on the machined surface. Therefore, the RA of low concentration oilstone honing ceramic material surface is higher. It can be seen from Figure 2 that the influence of diamond oilstone concentration on the honing surface roughness of ceramic materials is not as significant as that of oilstone particle size. In order to obtain better honing surface quality of engineering ceramics, the concentration of diamond oilstone should not be too low

2.3 diamond petrolatum bond

in the actual processing of engineering ceramic parts, resin bonded diamond tool products are generally used as cutting tools. In order to obtain high grinding ratio and processing efficiency, metal bonded diamond tools are usually used. The abrasive particle size of oilstone is 230/270 and the concentration is 75%. It can be seen from the comparison of binders in Figure 2 that there is little difference in the surface roughness values of ceramics processed with resin, bronze and cast iron bonded diamond oilstone. However, the surface roughness of ceramic materials after honing with electroplated diamond petroleum stone increases rapidly, which has the greatest impact on the surface quality of ceramic materials. The abrasive particles on the surface of electroplated oilstone are fully exposed, and deep scratches are machined on the surface of ceramic materials

3 analysis of surface quality of ceramic flat top honing

for precision coupling parts with matching accuracy requirements, the final machined surface quality is more important in use. Taking the application of ceramic materials in automobile and motorcycle engine blocks as an example, if the surface quality of materials is poor, surface wear will occur (see Figure 3): sharp peaks on the surface of ceramic materials, or sharp peaks on the surface contour between metal parts or ceramic materials that are matched by cutting, will collide with each other, resulting in the fitting size of parts exceeding the tolerance range, and the fitting accuracy will decline, thereby increasing fuel consumption

Figure 3 wear of mating surface

ceramic flat top honing goes through two processes: rough honing and fine honing, that is, rough honing with resin bonded diamond oilstone with particle size of 140/170 to form wrinkles; Then the particle size is 27. Later, when he became more and more familiar with this kind of material, the 0/325 SiC oilstone was finely honed to remove the sharp part of the rough machined surface ridges. The flat top honing method can not only remove the sharp convex edges in the surface contour of engineering ceramic materials and avoid the wear phenomenon in Figure 3, but also increase the bearing area of the machined hole surface, shorten the "running in" period of the hole surface, extend the "stable" wear period, and further increase the wear resistance of the machined surface of parts

the surface profile of Mg PSZ ceramic material after grinding and flat top honing (see Figure 4). Comparing the material surface profile of the two machining methods, it is obvious that the peaks and valleys of the surface profile of ceramic materials after grinding are randomly distributed, and there are many convex peaks on the surface, which is not suitable for precision mating surface. SiC oilstone in flat top honing has little cutting effect on ceramic materials, and can only remove the peak part of the surface profile of ceramic materials to obtain a flat surface profile

Figure 4 mg PSZ material surface profile

(a) grinding surface (b) flat top honing surface

the abrasive wear resistance of the material surface is closely related to the contour support length ratio curve (TP curve) and amplitude distribution curve related to the shape characteristics of the micro roughness of the material surface profile. The two curves visually illustrate the wear resistance of the material surface [3, 4]. If the surface profile of the material is very flat, the TP curve shape is flat, and the distribution range of the height amplitude of the surface profile is narrow, which indicates that the wear resistance of the material surface is good. On the contrary, if there are many convex peaks on the material surface, the shape of TP curve is steep, the distribution range of surface contour height is wide, and the wear resistance of the material surface is not good

the research shows that the TP curve shape of the ground surface is relatively steep, and the distribution range of the height amplitude curve of the surface profile is relatively wide. The wear resistance of the material surface is poor. However, for the material surface processed by flat top honing, the shape of TP curve is relatively flat, the distribution range of surface contour height amplitude curve is narrow, and the material surface has good wear resistance

the above research results prove the existence of the flat top characteristics of the machined surface of engineering ceramic materials. In production, we can choose a reasonable machining process to improve the mechanical properties of ceramic materials from the perspective of machining

4 conclusion

(1) there are certain differences in the honing surface roughness values of different ceramic materials. The lower the strength and the higher the brittleness of ceramic materials, the greater the machined surface roughness value. The honing of ceramic materials should also consider the influence factors of materials

(2) among the three honing tool parameters of diamond petrolatum particle size, concentration and binder, the influence of oilstone particle size and oilstone binder on the honing surface roughness of ceramic materials is more significant

(3) engineering ceramic materials adopt the flat top honing method, which can remove sharp peaks in the surface contour of the material and form a ceramic material surface with flat top characteristics, so as to avoid the wear of mating surface materials in practical application

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