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Reasonable application of thermal analysis instrument


Yuan Ju permit precision thermocouple deep end is generally away from the computer capacity, so the computer is not the ambient temperature is the ambient temperature test glass, the computer is in the general long-term work status, it will slowly increase the ambient temperature,[link widoczny dla zalogowanych], with air-conditioning to ensure a constant ambient temperature will increase the computer temperature accuracy. Measurement system in the above case,[link widoczny dla zalogowanych], the general shape of the measured cooling curve of molten iron and the actual theory of the cooling curve are similar, but the measured downward or upward curve can then iron-carbon eutectic temperature phase diagram of the principle of not people to determine the carbon equivalent. For example,[link widoczny dla zalogowanych], Figure 6 shows the error curve (dashed line), the computer to determine: TLzI170 ℃. Ts = 1135 ℃ △ T = 35 ℃ e pterygium were disheartened by a La Wai film is error on the curve of Fig. 6Influen4: eoftemperaturechecking411 ~ lroroncoolingG ~ urvo assuming the actual cooling curve of molten iron as shown in solid line, then △ ABc = △ abc, little change under the eutectic line of principle,[link widoczny dla zalogowanych], you can leave 『『 Jue 0 Introduction diesel engine crankshaft is one of the main parts . Many domestic and foreign diesel engine crankshaft using ductile iron,[link widoczny dla zalogowanych], in the course of the Central Standing Committee issued first prepared forms of failure. In analyzing the reasons for this type of crankshaft failure, we found that the fracture of such crankshaft manufacturing process not only generated in the driving surface and also trap on the course of their use is closely related to wear and tear '. Ductile iron crankshaft fracture is due to shrinkage in the casting process, slag and processing defects caused by rough, etc., have been discussed in the data; and the friction and wear due to the crankshaft and organizational changes in surface morphology caused by failure also not been reported in detail. This article by ball milling 8G diesel engine crankshaft is down, the process due to wear on the use of surface morphologies of the journal changes caused by the crankshaft fracture analysis. A physical and chemical analysis of macro and fracture location 11 ductile iron crankshaft crankshaft running IOOOO many hours after the dismantling, it was found in the fourth cylinder connecting rod journal has a long crack, the broken off, the fracture surface with the axis was 45. Direction, shown in Figure 1. The location of the cracks can be seen from the production of it between the shaft and the bearing friction and wear are very closely linked. 1.2 off-axis off-axis surface morphology typical surface morphology of the friction and wear. It has two characteristics, first, the surface becomes very rough, and both sides of the hole appeared on the surface of the groove is characterized by the phenomenon of strain shown in Figure 1; around a new wing of the crankshaft phenomenon of Fig-strain , ScrJtchofbrokencr ● - k ● h. tI followed by the existence of surface cracks as shown in Figure 2, reticulate, their distribution is roughly perpendicular to the grooves milled clearly seen that the general is very similar to grinding cracks. 13 physical and chemical detection l_3.1 chemical in the body is a sampling of off-axis, and its components) as: 2.02Si, 0.3Mn. 0.039P, <0.01S, 0.41Cu, 0.30Mo, 0. Ol7RE, 0.06ZMg. Meet the technical conditions of ductile iron crankshaft 1.3.2 microstructure of samples were detected in the tissues of patients with off-axis, the result is the ball of four, a small amount of graphite size 4 5, pearlite is greater than 95%, P eutectic 1.0%, 1.0% carbon. It can be seen, the crankshaft matrix meet the technical requirements, but in observing the surface microstructure of the journal, found a layer of significant uncertainty Ts = 1120 ℃, dashed down the pan as long as 15 ℃, too: TL ---- l170-15 = 1155 (℃) Ts = 1135 a l5 = 1120 (℃) and then were by the formula (2) a (4) calculated: CE = 4.15% C - 3.71% Si = l_37% actual E , just look at △ T (n-Ts) in size, we can determine the carbon equivalent iron disclosure is appropriate. Because the Ministry of △ T and the carbon equivalent to reflect the composition of molten iron extent of deviation from the eutectic point, if the target material to allow the change in composition in the range 3.95% ~ 4.25% cE, 1.35 ~ l_55% si, then the corresponding △ T should range from 50 ℃ to 22L04 Conclusion existing thermal analysis does not have the intelligence, the early crystallization platform for the cooling curve is not obvious, the computer can not give results, or even miscarriage of justice. Engineering and technical personnel must be able to accurately identify a variety of unusual curves, in order to ensure a reliable thermal analysis computer applications. References 1 medium-sized Itsuo. Introduction to Computer Solidification Analysis Hu Yunxiang translation.) Machinery Industry Press, 19882 Lu Wenhua Building, the melting of cast iron. Machinery Industry Press. 1981f999 closed on April 20 glass Huang Binnan. j; /

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