Subsequent Grinding Research Articles

Influence of the aging process on the dealloying activity of an induction salt bath

1. The process of dealloying of the surface of high-alloy steels in heating in induction salt baths with a graphite crucible is neutralized by the process of carburizing and electrochemical interaction in a high-frequency electromagnetic field. 2. The low dealloying activity of induction salt baths makes it possible to provide high tool quality with a partially ground profile or without subsequent grinding.

Improved method for the preparation of TiN-coated WC-Co-based samples for cross-sectional AEM investigation.

An improved method for the preparation of cross-sectional thin foils of coated WC-Co samples for studies by analytical electron microscopy is described. A braze alloy is used to join the sections of the sample together and the resulting sample is stable during subsequent grinding, dimpling, and milling operations. Cross-sectional micrographs provide examples of the efficacy of this method. No microstructural alteration associated with the brazing operation was observed.

A technique for separation of wheat germ by impacting and subsequent grinding

A technique was developed for the separation of the embryo and scutellum, which make up the wheat kernel germ, with improved yield and purity. The wheat embryo was separated prior to grinding by using the impact action of a horizontal scourer. Factors influencing embryo separation and the optimum working parameters of equipment for processing four classes of wheats were studied. A wheat moisture content of 13-5 % (w/w) and a working volume of 5-95 7[ ma/kg for the impacting scourer were the parameters that gave optimal embryo extraction and minimized kernel breakage. The yield of pure and intact wheat embryo ranged from 0-74 to 120 % on a wheat weight basis, which represented 53-6 to 91-6 % of wheat embryos present in samples dissected by hand. Subsequently, in the milling process the scutellum was separated by proper sieve selection of the 2 BK and 3 BKf and a grinding gap of 0279 mm for 3 BKf roll. The scutellum was purified using a gravity table, with a yield ranging from 0-75 to 1-75 % on a wheat weight basis. The embryo and scutellum products had high protein and crude fat contents. Removal of the embryonic axis, scutellum, and some additional flaked embryo during the process did not affect wheat milling quality. The flour's chemical composition was also unaffected, but the protein and fat contents of the mill feed were reduced. The germ products resulting from the new technique retain both morphological integrity and chemical composition.

遊星ミルによる珪砂の水中粉砕における粉砕平衡粒度

The limit of in-water grinding of silica sand by a planetary ball mill, which gives a much higher grinding rate than tumbling ball mills, was investigated from the viewpoint of mechanical grinding conditions. The grinding limit and subsequent negative grinding were confirmed in the in-water grinding. To do this, the product fineness was evaluated on the basis of size analysis by the laser scattering-diffraction method. As a result of a series of experiments, it was found that the grinding equilibrium size, defined as the minimum particle size determined by the size analysis, decreased as the ball size, ball density or mill's rotation was reduced. The grinding equilibrium size was well correlated with the maximum force exerting on a single ball in the mill pot within the experimental range.

Optical glass fabrication technology 2: Relationship between surface roughness and subsurface damage

For glass grinding conditions where fracture is the principal mechanism, a constancy is found between the depths of surface roughness and subsurface damage. For a range of experimental conditions we find the ratio of subsurface damage to surface roughness to be 6.2-6.4 for bound diamond abrasive grinding. This is larger than the value reported for loose abrasive grinding (3.7-4.0). The constancy of this value has great practical importance. From a measurement of the surface roughness one can obtain an accurate estimate of the damage layer thickness that must be eliminated by polishing or subsequent grinding operations.

Ductility of TiN-coated high speed steel

The ductility of high speed steel (HSS) coated with a thin layer of titanium nitride (TiN) was studied. The testing method was based on using a conventional Charpy impact testing hammer. The impact energy required to break the TiN-coated steel square rods used as test pieces was recorded. Uncoated HSS rods were used as a reference. The effects of the sputter cleaning atmosphere and the removal of the coating by masking or subsequent grinding of the test pieces were studied. TiN-coated samples obtained from different manufacturers were also compared. It was found that the TiN coating decreased the ductility to some extent in all the cases studied.

円筒プランジ研削における振動抑制の一方法

For the purpose of obtaining practical guidelines for controlling the vibration that produces on the plunge-cut ground surface the local variations of the light reflectivity, the mechanism by which the dynamic unbalance of the rotating grinding wheel generates the dynamic variation of the instantaneous stock removal and hence the onset of the grinding vibration has been studied by theoretical analysis as well as grinding experiments. Experiments have also been carried out to optimize the method of varying the rotational speed of the wheel, of which effect was demonstrated by a former study. By monitoring the oscillation of the machine body at the frequency of the wheel rotation, it is first recommended to adjust the wheel balance to minimize the monitored oscillation prior to the dressing operation. The subsequent grinding operation has to be carried out without introducing any balance adjustment and wheel speed variation after the dressing. Effect of the balance adjust procedure in suppressing the grinding vibration is further enhanced by introducing the wheel speed variation. According to grinding test results comparing the rectangular and triangular patterns of the wheel speed variation, the former has been found more effective, which at a ±10% range variation for 4 minutes period seems to result in an optimum effect for practice.

Kinetic study of the dehydration of sulfaguanidine under isothermal conditions.

Intact and ground crystals of Sulfaguanidine (monohydrate) were prepared by recrystallization from aqueous solution with or without subsequent grinding. The hydrate was also prepared by sorbing H2O vapor on the particles of anhydrous sulfaguanidine. By using these as sample materials, the dehydration curves at various temperatures were determined under dry conditions at 1 atm and in vacuo, as well as under various conditions of humidity. The applicability of various kinetic equations for solid state decomposition was investigated. It was found that chemically the same hydrate was dehydrated through different mechanisms depending on the crystal properties of the samples and the environmental conditions. In addition, changes in surface appearance of the intact and the ground crystals were observed during heating at constant temperatures. It is suggested that the differences in the dehydration mechanisms may be attributable to different modes of nuclei growth.

Microporous carbon adsorbent systems Communication 3. Experimental estimation of micropore system parameters

1. A method has been developed for the experimental determination of the characteristic dimensions of the mesopore and micropore zones of active carbons based on precipitation of carbon within the adsorbent granules and subsequent grinding and measurement of its adsorption properties and the external surface after grinding. 2. In the AC-30 active carbon studied, the size of the unit micropore zones was 220 nm and that of the unit mesopore zones was 540 nm.

Hot Impact Densification: A New Method for Producing High Density Ceramic Pellets with Close Shape Tolerances

Density and correct diameter of nuclear fuel pellets are usually achieved by sintering and subsequent circular grinding. Hot impact densification (HID) thermally squatted ceramic bodies can be directly high speed precision-molded in a cold die. For thermoshock-sensitive materials, a controlled cooling down procedure of some minutes is added. The feasibility of HID has been demonstrated on the laboratory scale on UO/sub 2/, UC, and some more materials at temperatures between 1700 and 2300/sup 0/C, pressures up to 800 N/mm/sup 2/. Shape tolerances are close, density can be exactly reproduced within a wide range. Tool wear seems to be no problem. Currently, a prototype facility for continuous performance is being developed.

Gelation and Fusion Characteristics of PVC Resins in Plastisols by Determination of Their Viscoelasticity

Abstract A poly(vinyl chloride) (PVC) plastisol is a suspension of fine particles of PVC dispersion resin in a plasticizer. The particle size ranges typically from about 15 to 0.2 µm and smaller. The PVC particles in the plastisol consist of the primary particles, which are products of polymerization, and of the agglomerates of the primary particles, which result from the spray drying and subsequent grinding. The commercial applications of plastisols are coatings, films, sheets, foams and rotational castings, where the plastisol is first spread on substrates, and then heated to gel and fuse. PVC dispersion resins are used to produce a variety of formulations, including those for automotive applications, coated fabrics and resilient flooring. Requirements for the plastisols are many; for example, good air release, viscosity stability, fine particle size, foamability and good heat stability. In general, the processability requirements emphasize the rheological behavior at room temperature and the gelation-fusion behavior, the latter being the subject of this paper. When a PVC plastisol is heated, the resin particles are penetrated by the plasticizer and become swollen. Consequently, the system becomes a dry, coherent mass; at this point the material has not attained its ultimate strength. This stage is called gelation. Upon continued heating to a higher temperature (e.g., 195°C) the microcrystallites of PVC melt and the polymer molecules fuse together more uniformly. Upon cooling, the material exhibits the intrinsic strength of a plasticized PVC. The rates of gelation and fusion are important and are often critical aspects of the processing of the plastisol. For example, the rate of gelation controls the residence time needed to build the wall thickness desired in slush molded boots or hot dip molded pieces. Gel rate also affects the uniformity of rotocast parts and the penetration of plastisol into fabric in cast coating operations. Fusion rate and the rate of decrease in melt viscosity after fusion affect uniformity of cells in chemically blown foams. Therefore, many commercial grades of PVC dispersion resins are offered, each having a different rate of gelation, fusion and ultimate properties.

Comparison of the fatigue limit of heat-resistant nickel alloys in bending and tension-compression

Specimens of heat-resistant nickel alloys were fatigue .tested in pure bending with rotation on machine type NUM. The frequency of the variable load was 50 Hz; the test base was 20-200 million cycles ( ~1001000 19. The tension-compress ion tests were carried out on MIR-ST machines with a frequency of the variable load of 35 Hz [6, 7]. The test base was taken equal to 10-50 million cycles (80-400 h). The specimens were heated to the test temperature in electric furnaces with omega-shaped heating elements. The fatigue tests of the heat-resistant nickel alloys at high temperatures were carried out by standard methods. The blanks for the fatigue-test specimens of formed alloy EI867 were cut out of rods; the specimens of cast alloys VZhL12U and ZhS6K were made by precision casting in vacuum. The blanks thus obtained were heat treated under standard conditions. The specimens were made by turning with subsequent grinding and polishing of the working part to V 9-10. The chemical composition and mechanical properties of the material of the specimens conformed to the standard. The fatigue tests in bending with rotation of the alloys EI867 and ZhS6K were made with specimens with a toroidal working part of 7.0 mm diameter and ofthe alloy VZhL12U, withcylindrical working part of 7.5 mm diameter and length [p = 5d. Fatigue tests with tension-compress ion were carried out with specimens with a cylindrical working part of 7.5 mm diameter and length lp = 5d. Before the tests, the specimens were subjected to visual and instrumental inspection, and the diameters of their working part and heads were measured. For the purpose of verifying the homogeneity of the material, selective hardness measurements of the specimens were carried out. The results of the fatigue tests were processed by linear regression analysis on a BF.SM-4 computer. The obtained data were approximated in coordinates log ~a log Np by straight lines (in case of a break by two straight lines).

The effects of induced prenatal hypothyroidism on lamb mandibular third primary molars

Intrauterine thyroidectomies were performed on nine lambs on or about the ninety-sixth postconception day. Seven other control and shamoperated lambs, and the cretin lambs were sacrificed immediately after birth. The mandibles were removed and sectioned at the midline. The right side molars were removed by dissection and caliper measured. The distal cusps of the third primary molars were sectioned, dehydrated, and embedded in Bioplastic. A slow speed diamond saw was used to section the plastic blocks and the embedded teeth. Subsequent grinding and polishing produced high quality 75 micrometer sections of the lamb molar cusps. No significant differences in tooth size or enamel thickness existed. Microscopic examinations show that parts of the cretin enamel were poorly calcified, an observation that was correlated to the intrauterine thyroidectomies. The data suggest that hypothyroidism alters ameloblastic activity during the secretory phase of enamel formation.

Transformation of Alkoxy-Derived PbO by Heating and Grinding

The present study was performed in order to study the phase transformation of alkoxy-derived PbO, two polymorphic modifications of litharge (tetragonal) and massicot (orthorhombic), caused by heating and grinding. Techniques employed are DTA, X-ray analysis and electron microscopy.Transformation isotherms of litharge (A) having a tetragonal plate-like form were characterized by sigmoidal shape, and kinetics were best described by the Avrami equation, ln(1-α)=-ktn(n=2), where a, t, k, and n are the fraction of transformation, time, rate constant and proportionality constant, respectively. In the case of litharge (B) obtained by grinding, n in the Avrami equation was 3. The above results are explained by the difference on particle forms. The values of the activation energies calculated from the Arrhenius plots are about 50 kcal/mol and 35kcal/mol, respectively. These activation energies represent those of the nucleation growth of massicot.The transformation from massicot to litharge was completed by grinding for 10min in vacuum, and the ground product was only litharge through long times. The line profiles of the X-ray powder diffraction patterns of the ground litharge showed the decrease of height and the broadening of breadth with increasing time. The size of crystallites became rapidly small by grinding for 20 h, and it was hardly influenced by the subsequent grinding. On the other hand, the lattice distortion increased gradually with increasing time. When litharge ground for long times was heated in air, PbCO3·PbO and 4PbCO3·3PbO were formed by the reaction with CO2 in the heating process. This results show that PbO has a tendency to absorb CO2.

Speeding up the milling op refeactory materials

It is possible to intensify the grinding of refractory materials by introducing closed cycle schemes. An increase in the output of tube mills during combined grinding with a simultaneous increase in the fineness of the harder components of the mixture is achieved by pregrinding the hard component in a separate grinding unit to a prescribed size with subsequent combined grinding of both components in a tube mill.

Effect of impurity additions on the remanence and coercivity of reduced hematite ores

AbstractSynthetic ores of pure ferric oxide, and ferric oxide with additions of CaO, SiO2, MnO2 and TiO2 were made up by sintering the mixtures at 1100°C. Subsequent crushing, grinding and screening yielded ores with particle between 149 and 208 microns. The ores were reduced to mainetite between 500°C and 1000°C in a CO-CO2 atmosphere.The coercive force and remanence of the reduced ores were determined using a 60 cps hysteresis loop tracer. The addition of CaO decreased the coercive force and remanence of the reduced ore as compared to pure magnetite, whereas the effects of the other additions were not significant. Explanations for the findings are offered. Resume Des minerais synthetiques d'oxide ferrique pur et d'oxyde ferrique additionne de CaO, SiO2, MnO2 et TiO2 ont ete elabore par frittage a 1100°C. Apres broyage et tamisage, la tail1e des particules de minerai s' echelonnait de 149 a 208 microns. Ces minerais etaient ensuit reduits en magnetite a des temperatures variant de 500 a 1000°C en atmosph...

Nitriding gears without subsequent grinding

Nitriding gears without subsequent grinding

Improved Spectrochemical Analysis of Alumina by Mineralized Calcination

Alumina-types present striking differences in physical properties, which have detrimental effects on accuracy of spectrochemical analysis. Calcination with a small amount of aluminium fluoride eliminates many of these differences The “mineralized calcination step” converts all samples to essentially alpha alumina of very similar monocrystal size, and subsequent grinding while mixing with graphite introduces still more uniformity This treatment is simple and can be carried out on a number of samples at the same time It provides significant improvement in both accuracy and precision. Details of the pre-treatment are presented along with analytical data to show the improvement.

Automatic control of dimensional accuracy in internal grinding

With the above method of measuring under optimum conditions, it is almost possible to completely eliminate the effect of allowance variations on the accuracy of the ground ring diameters. 2. On grinding machine 02S33, and similar machines, it is possible to grind details without subsequent precision grinding, thus raising the productivity of the grinding process.

Sectioning and fault analysis of junction transistors

Special techniques have recently been developed by the authors to enable microsections to be readily made on high-frequency p-n-p and p-n-i-p junction transistors. It is impossible to use standard metallographic techniques when sectioning these devices, owing to the extreme fragility of the very thin germanium wafers used in their fabrication. Wafers as thin as 0.001 in may be encountered, and it has been found necessary to encapsulate the specimens in two stages, using different resins, to ensure adequate support of the wafer edges and so avoid chipping of the wafers during the subsequent grinding and polishing operations. A detailed grinding and polishing procedure has been developed to give optimum surface finish. The junction structure can finally be shown up by preferential etching.After preparation, the specimens can be microscopically examined, photographed and much valuable information extracted concerning the wetting, alloy penetration, recrystallization, crystal orientation and junction geometry. It is possible to examine the effect of the final clean-up etch used during manufacture, and in some cases to explain soft reverse-junction characteristics.The paper describes the preparation of large numbers of sections on a routine basis, using these techniques, and a number of examples are shown and typical faults discussed. The information obtained from these samples has proved of considerable value, particularly during the early stages of any new development.