无心磨床试磨中的问题与解决方法

简要介绍了无心磨床磨削的工作原理和磨削方法,对试磨前的整备及注意事项、试磨时的调整方法、试磨时工件的不良现象及其解决方法进行了分析探讨,以供无心磨床试磨操作者和初学者参考。

热磨试间火灾爆炸风险分析

采用层次分析法对热磨试间火灾爆炸风险进行分析,以某企业热磨试间内热磨合作业过程为例建立了评价模型。为提高层次分析法的准确性和有效性,在层次分析法之前,引入事故树,通过事故树确定各级指标,在层次分析法之后,通过与模糊数学相结合,对模型进行模糊评价,得出模型所处等级D=0.7087,即该企业热磨试间火灾爆炸风险为"危险性较大"等级。研究表明,"事故树-模糊层次分析法"应用于热磨试间火灾爆炸风险分析是可行的,有助于企业有针对性地制定安全措施,预防热磨试间火灾爆炸事故的发生。

MPS35.5型模型磨煤机试磨方法和制备褐煤性能的试验研究

本文主要介绍 MPS35.5型磨煤机的试磨方法和制备褐煤特性。

S型风扇磨煤机的选型与应用

众所周知，影响风扇磨煤机的性能参数主要有：煤质特性、风扇磨的结构特性和运行特性。传统的风扇磨的选型往往是根据煤的可磨度、煤粉细度和原煤水份等修正系数来确定风扇磨的性能参数。实践证阻，该选型方法是不完善的，其通用性较差。采用煤种的试磨方法是风扇磨选型和制粉系统设计较为可靠的方法。本文介绍了根据流动和几何相似原理建立起的Ｓｏ２．３００型风扇磨试验系统，通过对扎赉诺尔和霍林河褐煤的试验验证，把试磨的有关参数移植到大型风扇磨的选型设计中去。为设计院根据煤种合理选择风扇磨及其制粉系统设计提供依据。

活塞环使用的初期磨合

本文从理论与实践方面阐述了活塞环使用中产生磨损的机理，指出了其初期磨合的重要性，并从多年的生产实践中总结出了一套冷磨热试的工艺参数与规范，对活塞环的正确使用及延长寿命有一定参考价值。

660MW机组半焦煤粉锅炉制粉系统选型

半焦作为一种新型的锅炉燃料,其研磨和磨损特性与常规煤种存在较大不同,仅靠理论计算无法满足半焦磨煤机合理选型的要求。本文利用小型半工业性钢球磨煤机试验台,对半焦在钢球磨煤机上的研磨出力、煤粉细度、制粉电耗进行了试验研究,并根据试验结果对纯燃用半焦的超超临界660 MW机组锅炉制粉系统设备进行选型。结果表明:半焦具有热值高、挥发分低、难磨、磨损性强等特点,磨煤机应选择双进双出钢球磨煤机,选取耐磨能力较强钢球及磨煤机衬板;半焦在钢球磨煤机上的实际研磨出力低于理论计算值,建议选用稍大型号磨煤机。

Dry sliding friction and wear behaviors of Mg_2B_2O_5 whisker reinforced 6061Al matrix composites

The friction and wear properties of Mg2B2O5 whisker reinforced 6061Al matrix composite fabricated via power ultrasonic-stir casting process were investigated using a ball-on-disk wear-testing machine against a GCr45 steel counterface under dry sliding conditions. The reinforcements include as-received Mg2B2O5 whiskers and Mg2B2O5 whiskers coated with CuO and ZnO. The volume fraction of the composites is 2%. The relationship between the wear rate and the coefficient of friction was discussed. The results indicate that the wear rate of the Mg2B2O5 whiskers coated with ZnO reinforced aluminum matrix composites is the lowest among the materials. As the applied load and sliding speed steadily increase the coefficients of friction and wear rates of the as-received matrix alloy and the fabricated composites decrease. As the applied load and sliding speed increase, the wear mechanisms of the composites shift from a mild to a severe regime.

压缩机主轴变形分析

通过对压缩机Cr17N i2主轴的热处理、试磨以及残余应力测定等试验,找出了主轴变形的主要影响因素。合理的热处理能够使主轴的残余应力值减至合格,而不适当的磨削也可使轴内产生应力。

IMPACT-SLIDING WEAR OF MATERIALS

A simple impact-sliding wear test rig is designed for studying the wear behavior between solid materials on a repetitive normal impact accompanied with the tangential sliding. The test rig consists of a cantilever beam forced by the dynamoelectric vibration exciter and a rotational shaft driven by a spindle. It has a widely adjustable range of testing parameters, including the impact frequency, the impact load and the sliding velocity. The avail- able maximum impact frequency, impact load and sliding velocity are 100 Hz, 200 N and 4.52 m/s, respectively. To evaluate the capability of the test rig, tests are carried out and the impact load is measured. Results show that the test rig has the good repeatability under the same test conditions and the repeatable error is less than 7%. Furthermore, non-destructive examination results by the mass loss method, two-dimensional profilometry and the scanning electron microscopy （SEM） show that the test rig can meet the demands for the impact-sliding wear.

Influence of niobium and molybdenum addition on microstructure and wear behavior of laser-borided layers produced on Nimonic 80A-alloy

Laser alloying was used for production of thick layers on surface of Nimonic 80A-alloy.For laser surface modification,three types of pre-coated pastes were applied:with amorphous boron,with amorphous boron and molybdenum as well as with amorphous boron and niobium.The microstructure,hardness and wear resistance of produced layers were studied in details.The presence of different types of borides in re-melted zone depended on the paste composition and caused an increase in hardness up to about HV 1000.The wear resistance was evaluated by calculation of mass wear intensity factor Imw and relative mass loss of specimen and counter-specimen.The wear behavior of the tested frictional pairs was determined by 3D interference microscopy,scanning electron microscopy equipped with EDS microanalyzer.The significant increase in abrasive wear resistance was observed in comparison to untreated Nimonic 80A-alloy.The lowest mass loss intensity factor was characteristic of laser-alloyed Nimonic 80A-alloy with boron and niobium(Imw=1.234 mg/(cm2?h)).Laser alloyed-layers indicated abrasive wear mechanism with clearly visible grooves.Laser alloying with boron and niobium resulted in the additional oxidative wear mechanism.In this case,EDS patterns revealed presence of oxygen on the worn surface of specimen.

Effects of additives on corrosion and wear resistance of micro-arc oxidation coatings on TiAl alloy

Ceramic coating was deposited on TiAl alloy substrate by micro-arc oxidation(MAO)in a silicate-aluminate electrolyte solution with additives including sodium citrate,graphite and sodium tungstate.The microstructures and compositions were analyzed by SEM,EDX and XRD.The corrosion and wear properties of the coatings were investigated by potentiodynamic polarization and ball-on-disc wear test,respectively.The results show that the MAO coatings consist of WO3,Ti2O3,graphite and Al2O3 besides Al2TiO5 and Al2SiO5.With additives in the electrolyte,the working voltage at the micro-arc discharge stage decreases,and the ceramic coating gets smoother and more compact.The corrosion current density of MAO coating is much lower than that of TiAl substrate.It can be reduced from 9.81×10-8A/cm 2to 3.02×10-10A/cm 2 .The MAO coatings composed of hard Al2O3,WO3 and Ti2O3 obviously improve the wear resistance of TiAl alloy.The wear rate is-3.27×10-7g/(N·m).

Friction properties of groove texture on Cr12MoV surface

To analyze the influence of surface texture on friction properties of Crl2MoV＇, ordinary grinder and spinning technology were adopted to obtain the grooved surface morphology of samples, and then the impact of spindle speed and feed in z-direction on surface morphology in the process of spinning was studied. In addition, the corresponding friction coefficient of sample was obtained through friction and wear tests. The results show that the peak clipping and the valley filling were conducted on the grinding surface, which could improve the surface roughness effectively and make the grinding trench-type wear scar more uniform. Both the area ratio of groove and groove spacing increased initially and then decreased with the increase of the spindle speed or the feed in z-direction. As a kind of micro-process, the groove could influence the friction coefficient of sample surface, whose distribution was beneficial to the reduction of friction coefficient. Compared with the surface obtained through ordinary grinding, grooved surface morphology through spinning technology was more conductive to reduce the friction coefficient, which could be reduced by 25%. When the friction coefficient of sample was reduced to the minimum, the texture of groove corresponded had an optimal area ratio and an optimal groove spacing, 37.5% and 27.5 μm, respectively.

Influence of pH values on electroless Ni-P-SiC plating on AZ91D magnesium alloy

A novel Ni-P-SiC composite coating was prepared by electroless plating in order to improve the corrosion capacity and wear resistance of AZ91D magnesium alloy.The influence of pH values on deposition rates and properties of the coatings was studied.The microstructure and phase structure of the Ni-P-SiC coatings were analyzed by scanning electron microscopy(SEM)and X-ray diffractometry(XRD).The corrosion and wear resistance performances of the coatings were also investigated through electrochemical technique and pin-on-disk tribometer,respectively.The results indicate that the composite coating is composed of Ni, P and SiC.It exhibits an amorphous structure and good adhesion to the substrate.The coatings have higher open circuit potential than that of the substrate.The composite coating obtained at pH value of 5.2 possesses optimal integrated properties,which shows similar corrosion resistance and ascendant wear resistance properties to the substrate.

Comparison of wear behaviour of LM13 Al−Si alloy based composites reinforced with synthetic(B_(4)C)and natural(ilmenite)ceramic particles

Dry sliding wear behaviour of stir-cast aluminium matrix composites(AMCs)containing LM13 alloy as matrix and ceramic particles as reinforcement was investigated.Two different ceramic particle reinforcements were used separately:synthetic ceramic particles(B_(4)C),and natural ceramic particles(ilmenite).Optical micrographs showed uniform dispersion of reinforced particles in the matrix material.Reinforced particles refined the grain size of eutectic silicon and changed its morphology to globular type.B_(4)C reinforced composites(BRCs)showed maximum improvement in hardness of AMCs.Ilmenite reinforced composites(IRCs)showed maximum reduction in coefficient of friction values due to strong matrix−reinforcement interfacial bonding caused by the formation of interfacial compounds.Dry sliding wear behaviour of composites was significantly improved as compared to base alloy.The low density and high hardness of B_(4)C particles resulted in high dislocation density around filler particles in BRCs.On the other hand,the low thermal conductivity of ilmenite particles resulted in early oxidation and formation of a tribo-layer on surface of IRCs.So,both types of reinforcements led to the improvement in wear properties of AMCs,though the mechanisms involved were very different.Thus,the low-cost ilmenite particles can be used as alternative fillers to the high-cost B_(4)C particles for processing of wear resistant composites.

Wear mechanism for spray deposited Al-Si/SiC_p composites under dry sliding condition

Al-Si/15%SiCp(volume fraction) composites with different silicon contents were fabricated by spray deposition technique, and typical microstructures of these composites were studied by optical microscopy(OM). Dry sliding wear tests were carried out using a block-on-ring wear machine to investigate the effect of applied load range of 10-220 N on the wear and friction behavior of these composites sliding against SAE 52100 grade bearing steel. Scanning electron microscopy(SEM) and energy-dispersive X-ray microanalysis(EDAX) were utilized to examine the morphologies of the worn surfaces in order to observe the wear characteristics and investigate the wear mechanism. The results show that the wear behavior of these composites is dependent on the silicon content in the matrix alloy and the applied load. Al-Si/15%SiCp composites with higher silicon content exhibit better wear resistance in the applied load range. Under lower loads, the major wear mechanisms are oxidation wear and abrasive wear for all tested composites. Under higher loads, severe adhesive wear becomes the main wear mechanisms for Al-7Si/15%SiCp and Al-13Si/15%SiCp composites, while Al-20Si/15%SiCp presents a compound wear mechanism, consisting of oxidation, abrasive wear and adhesion wear.

Microstructure,mechanical and wear properties of aluminum borate whisker reinforced aluminum matrix composites

The microstructural features and the consequent mechanical properties were characterized in aluminium borate whisker(ABOw)(5, 10 and 15 wt.%) reinforced commercially-pure aluminium composites fabricated by conventional powder metallurgy technique. The aluminium powder and the whisker were effectively blended by a semi-powder metallurgy method. The blended powder mixtures were cold compacted and sintered at 600 ℃. The sintered composites were characterized for microstructural features by optical microscopy(OM), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), transmission electron microscopy(TEM) and X-ray diffraction(XRD) analysis. Porosity in the composites with variation in ABOw contents was determined. The effect of variation in content of ABOw on mechanical properties, viz. hardness, bending strength and compressive strength of the composites was evaluated. The dry sliding wear behaviour was evaluated at varying sliding distance at constant loads. Maximum flexural strength of 172 MPa and compressive strength of 324 MPa with improved hardness around HV 40.2 are obtained in composite with 10 wt.% ABOw. Further increase in ABOw content deteriorates the properties. A substantial increase in wear resistance is also observed with 10 wt.% ABOw. The excellent combination of mechanical properties of Al-10 wt.%ABOw composites is attributed to good interfacial bonds, less porosity and uniformity in the microstructure.

Effect of applied load on transition behavior of wear mechanism in Cu-15Ni-8Sn alloy under oil lubrication

Tribological behavior of Cu-15Ni-8Sn(mass fraction, %) alloy against GCr15 ring under various loads was investigated on a ring-on-block tester in oil lubrication. The results showed that the wear rate increased slowly from 1.7×10^(-7) to 9.8× 10^(-7) mm^3/mm under the load lower than 300 N, and then increased dramatically to the climax of 216×10^(-7) mm^3/mm under the load over 300 N, which indicated the transition of wear mechanism with the increase of applied load. The wear mechanism mainly was plastic deformation and abrasive wear under the load less than 300 N. As the applied load was more than 300 N, the wear mechanism of Cu-15Ni-8Sn alloy primarily was delamination wear. Besides, the transition can also be confirmed from the different morphologies of worn surface, subsurface and wear debris. It is distinctly indicated that the appearance of flaky debris at the applied load over 300 N may be a critical point for the change of wear mechanism.

Study on Lubrication Properties of Modified Nano ZnO in Base Oil

ZnO nanoparticles with an average size of 125 nm were prepared via homogeneous precipitation method and were characterized by SEM.The products were surface-modified by the surfactant SDS.Surface-modified nano particles were added at a mass ratio of 1.0%,2.0%,3.0%,and 4.0%,respectively,in base oil and their friction and wear behaviors were evaluated on a MRS-10D type four-ball wear tester.After four-ball wear tests,the morphology of the rubbing surfaces was evaluated with metallographic microscope.It was revealed that the modified nano ZnO had excellent behavior for improving anti-wear property and friction coefficient,which could greatly reduce the friction of machine parts.

The Effect of Counter-face Roughness on the Tribological Behavior of Filled and Unfilled PTFE

Since the wear problems play a crucial role in the relatively moving systems, in this paper, the effect of counter-face roughness on the wear of extruded PTFE （polytetrafluoroethylene） which is a very common material for sliding bearing applications has been investigated to contribute related literature. PTFE is well-known for its exceptional tribological properties, and good toughness, and high thermal stability. It can also be used in dry sliding applications. PTFE is commonly used to reduce friction between relatively moving surfaces, lts wear rate can be reduced by adding micro or nano-sized fillers such as Al2O3, TiO2, SiO2, MoS2, Al, Pb, ZnO, Cu, ZrO2, Ni, CNF （carbon nano fiber）, carbon fiber, glass fiber, bronze, and graphite powder into the PTFE. In this study, an experimental research was carried out for filled and unfilled PTFE to compare their behaviors under different speeds and loads. Test materials were unfilled PTFE, PTFE ＋ wt. 5% Al2O3, PTFE ＋ wt. 15% Al2O3. Formation of transfer film was examined in dry sliding condition against stainless steel counter faces. All tribological tests were carried out in a commercially available tribo-tester sliding against AISI-416 C stainless steel. As a result of a series of systematic experiments, remarkable results have been obtained to make a distinctive comparison between unfilled and filled PTFE. The variation of friction coefficient with sliding distance during the tests has also been recorded. At the end of the tests, wear rate of related PTFE specimen was calculated based on measured data. Wear rate is found very high for unfilled PTFE, however, the lowest wear rate is recorded for PTFE ＋ wt. 15% Al2O3 as expected. The coefficient of friction remained approximately stable during the wear tests. Transfer films were inspected by observing the discs＇ surface with optical microscope.