Quantitative Examination of the Inclusion and the Rotated Bending Fatigue Behavior of SAE52100

This study investigated the effect of maximum inclusion on the life of SAE52100 bearing steel processed by two different melting routes, vacuum induction melting plus electroslag remelting (VIM + ESR), and basic oxygen furnace plus ladle furnace plus vacuum degassing process (BOF + LF + RH) by the metallographic method, Aspex explorer, and rotated bending fatigue test. The rotated bending method was applied to examine the maximum inclusion size in a satisfactory manner, whereas both the metallographic method and Aspex explorer underestimated the result. Regardless of the characterization methods, the results show that the total number of inclusions in VIM + ESR melted steel is significantly higher than that in BOF + LF + RH processed steel, but the maximum inclusion size of VIM + ESR melted steel is significantly smaller than that of the BOF + LF + RH degassed steel. The distribution of the maximum inclusion size could be well fitted by the inverse Weibull distribution and could be well applied to reveal the different inclusion size distribution based on the data examined by the rotated bending fatigue method. Finally, a new equation was proposed to establish the relationship among the loading stress amplitude, rotated bending fatigue number, and the maximum inclusion size.

A METHOD FOR ASSESSING THE OPERATIONAL RELIABILITY OF WELDED CONNECTIONS FROM 09G2S STEEL WORKING IN ENVIRONMENTS CAUSING CORROSIVE CRACKING

Based on the study of the structure and mechanical properties of the metal of welded joints of 09Г2С steel, a metallographic method has been proposed, which makes it possible to establish the fact of post-weld heat treatment when determining the causes of corrosion cracking in aggressive environments of petrochemical and oil refineries, as well as supervising welding operations.

CHIP FORMATION DURING THERMAL FRICTION TURN-MILLING

This paper presents the results of chip formation studies in the processing of 30KhGSA steel by thermofriction turn-milling. When studying the process in this work there are presented the results of studying chip formation when the processing of chip formation there is used the metallographic method. Chip root area investigated. The dependence of the chip shrinkage coefficient on the cutting speed and feed was also investigated. It is established that with increasing supply S the value of the chip shrinkage coefficient K decreases. The higher the chip shrinkage factor, the more work will be required to cut the chips and the more complex the processing process.

Examining of Solid and Liquid Industrial Copper Blanks with Purpose for Quality Control in Respect of Defects of Technological Origin

Microstructure of ingot and industrial blanks made of copper M2 was examined for quality control. Microstructure was examined by means of traditional metallographic analysis methods. Exogenous nonmetal inclusions and pores in microstructure were found. The transition from exogenous inclusions and pores, which were not removed in initial processing stage, to the crack, which leads to billet destruction on one of last processing stages, is shown. Without quality control of copper blanks by a metallographic method, it is impossible to provide guarantee of reliable operation of machines and responsible purpose constructions. A comparative study of the temperature dependences of the viscosity of the melts of charge materials and finished ingots for copper M2 was carried out. The study of the viscosity of copper melts M2 was carried out with the aim of quality control in the chain of "charge-melt-ingot" at the foundry stage.

Metallographic Determination of Strain Distribution in Cold Extruded Aluminum Gear-Like Element

In this study, an experimental, metallographic method for determining strain distribution in a cold extruded aluminum gear-like element, based on the dependence of recrystallized grain size on prior deformation, was devised in order to overcome design problems in manufacturing of complex parts where critical values of strain and stress could cause a fracture. The method was applied on a 99.5% aluminum bar subjected to cold, radial extrusion, in order to produce complex gear-like element. To reveal the strain and stress distribution in specimens, the calibration and flow curves were first obtained by uniaxial compression (Rastegaev test). Afterwards, the grain size in different parts of the gear section was examined, the strain and stress distributions were calculated, and the results were confirmed by microhardness measurements. It was found that grain size, strain, stress, and microhardness considerably differed throughout the cross-section of the gear. The coarsest grain, and thus the lowest strain zone, was obtained in the central part of the tooth and in the zone between teeth. Conversely, the finest grains appeared in the highest strain zone at the specimen surface, particularly in the root of the teeth. Furthermore, results were supported by microhardness measurements, i.e., microhardness corresponded to grain size and strain hardening. Finally, the real view of material flow in the complex extruded part was successfully obtained by the metallographic method.

Analysis of Primary Short Circuited Melted Mark Evidence Identification in Electrical Fire Case

Regardless of fire heat or short circuit high temperature melting, the residual traces which represent the environmental characteristics can be found in copper and aluminum wires. The primary short circuited melted mark identification must be scientific and objective for physical evidence of the electricity fire during detecting, and the conclusions are related to the fire survey process. Currently, identification method of electricity fire, including macroscopic method and metallographic method, is very general and lacking of standard reference map and detailed description. According to the macro and micro characteristics and formation mechanism of various fire wire melted marks and the characteristics of metallographic organization of primary short circuited melted mark, two actual cases were analyzed in detail so as to distinguish the relationship between the melting reason and fire cause and to confirm that these two fires are caused by primary short circuit.

Experimental Research of Rotational-and-Frictional Boring of Big Holes in Large Parts

When producing large-dimensional parts of heavy machines, the largest specific weight in the general labour input is made by the operations, connected with machining the main holes, i. e. holes of large diameter. To the holes of large diameter of large-dimensional parts, there are specified high requirements in the aspect of accuracy of the size, shape and arrangement. Machining of holes still remains one of the topical problems of present day mechanical engineering, in particular machine-building enterprises of the Republic of Kazakhstan. Solving the problem of ensuring accuracy and quality of machining large holes of large-dimensional parts requires the development of new resource-saving technologies of machining. In this work there are presented the results of studying a resource-saving method of rotation-friction boring of large diameter holes. There has been achieved good results in providing the quality indicators, when machining by the proposed method of rotation-friction boring with the use of the tool (a disk cutter) made of steel 90CrSi5 in comparison with well-known boring of holes. The diagram of chip formation of cutting and the results of studying the zone of chip formation by the metallographic method is also presented.