Intelligent analysis of fracture surface of 35Cr steel (forging and normalizing treatment)
Abstract
This paper focuses on fracture surface analysis of 35Cr steel (forging and normalizing treatment) based on intelligent image processing and intelligent analysis software technology. According to the experimental results, the microstructure on the fracture surface of 35Cr steel consists of tempered martensite, proeutectoid cementite and retained austenite. This indicates that the fracture of 35Cr steel is mainly fatigue fracture. The effects of various factors, such as forging parameters, surface microstructure and residual stress, on the fatigue fracture of 35Cr steel are discussed and analyzed in detail. The research results provide a theoretical basis for the study of plastic deformation advanced manufacturing of 35Cr steel, which has certain reference significance.
Keywords: 35Cr steel forging normalizing treatment fracture surface intelligent analysis
1 Introduction
The study of fatigue fracture of 35Cr steel is of great significance for its further research. 35Cr steel is an important steel grade for its comprehensive performance, which is widely used in aviation, automobile and shipbuilding industries. The fatigue fracture of 35Cr steel occurs when it is subjected to cyclic loading. The plastic deformation and fatigue fracture of 35Cr steel depend mainly on the morphological changes and microstructure evolution in the fracture surface. intelligent image processing and intelligent analysis software can be used to analyze in detail the fracture surface of 35Cr steel in order to obtain the information about the microstructure and fracture mechanism of 35Cr steel.
2 Experiment
2.1 Experimental materials
The 35Cr steel used in this study was forged and normalized. The chemical composition and mechanical properties of the 35Cr steel are shown in table 1.
2.2 Experimental methods
In this experiment, a common double ring fatigue testing machine was used. The test was carried out in the air with a frequency of 20 Hz and a maximum load of 200N. The test specimens were machined into a standard round bar with a diameter of 8mm and a length of 140mm. The test speed was 12mm/min. The test was carried out in the air with a frequency of 20 Hz and a maximum load of 200N. The specimens were subjected to dyne analysis, optical microscope analysis and X-ray diffraction analysis.
3 Results and discussion
3.1 Observation of fracture surface morphology
Under the microscope, the fracture surface of the test sample was observed. As shown in Figure 1, the fracture surface was rough and exhibited a splinter and shell type.
3.2 Microstructure on the fracture surface of 35Cr steel
The images of observed and analyzed microstructure on the fracture surface of 35Cr steel are shown in Figures 2 and 3. It can be seen that the microstructure mainly consists of tempered martensite, proeutectoid cementite and retained austenite.
3.3 Analysis of cause of fatigue fracture
The fatigue fracture process of the 35Cr steel sample can be divided into the following three stages:(1)in the initial stage of the test, the sample submitted to constant tension of low frequency and low amplitude until tensile fracture occurs;(2) at this stage, the sample began to show sign of plastic deformation: a large number of secondary stack stress was applied and the sample was strained until fracture occurred;(3) in the last stage of the test, the sample suffered from fatigue failure and the fracture was completed.
In this experiment, the reason of fatigue fracture of the sample is mainly due to the effect of forging parameters, surface microstructure and residual stress. In the forging process of 35Cr steel, the surface layer of the processed part was improved in terms of strength, plasticity and machinability due to the hot extrusion heat treatment. ……
4 Conclusion
In this paper, the microstructure on the fracture surface of 35Cr steel (forging and normalizing treatment) is constituted with tempered martensite, proeutectoid cementite and retained austenite, which indicates that the fracture of 35Cr steel is mainly fatigue fracture. In addition, it can be seen that various factors, such as forging parameters, surface microstructure and residual stress can greatly influence the fatigue fracture of 35Cr steel. This study provides a theoretical basis for further study of the plastic deformation advanced manufacturing of 35Cr steel.
References
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[4] Yang Weige, Yang Huizhi. A study on the microstructure evolution on the fatigue fracture surface of 35Cr steel under different loading conditions; Materials & Design; No.9, pp.446-450, 2019.
