Analysis of the Microstructure and Non-Metallic Inclusions of 34CrNi3Mo Steel
Abstract
The microstructure and non-metallic inclusions of 34CrNi3Mo steel were studied by metallographic microscope, SEM and EDX. The results showed that 34CrNi3Mo steel had lath martensite and a few laths of ferrite. The grain sizes of the matrix structure and lamellar structure were microstructure and non-metallic inclusions. The shape of non-metallic inclusions .were ferritic, oxides and sulfides. The size of the non-metallic inclusions was very small in microstructures. Thus, this had a complicated effect on the 34CrNi3Mo Steel.
1 Introduction
The 34CrNi3Mo steel is a kind of high-strength special steel with core strength of 1100 and a yield strength of 950 MPa, which can be used for manufacturing important parts and tools in aviation, ships, vehicles and household appliances industries. Therefore, the study of its microstructure and non-metallic inclusion is of great significance in the practical application of this steel.
2 Materials and Methods
The 34CrNi3Mo steel was taken from a large bar of the same material with a diameter of 73 mm. The sample had been quenched to form a martensitic microstructure. The microstructure and non-metallic inclusions were studied by metallographic microscope, SEM and EDX analysis.
3 Results and Discussion
3.1 Results
The low magnification micrograph of 34CrNi3Mo steel is shown in Figure. 1, which shows that martensite and a few laths of ferrite are present in this steel. The microstructures are composed of lath martensite, ferrite, and a small number of non-metallic inclusions. The grain sizes of the matrix structure and lamellar structure were relatively uniform, and they were mainly in the range of 0.2-1.2 mm.
The SEM micrograph in Figure.2 shows that non-metallic inclusions in 34CrNi3Mo steel were small, and the shape of non-metallic inclusions was irregular, including ferrites, oxides and sulphides. The size of these non-metallic inclusions was generally 0.1 to 5 μm.
Figure. 3 shows the EDX analysis of the non-metallic inclusions. The elemental analysis of the non-metallic inclusions showed that the major element was C, Si, O, S, Fe and some trace elements such as Mn and P.
4 Conclusion
In summary, the results show that 34CrNi3Mo Steel has a lath martensite structure and a few laths of ferrite. The grain size of the microstructure is relatively uniform. The shape of non-metallic inclusions is ferritic, oxides and sulphides, and the size of non-metallic inclusions is very small. This study provides basic information for further improving the performance of this steel.
Acknowledgments
This study was supported by the National Natural Science Foundation of China (No. 51575095). The authors would like to thank Professor Q. Yang at Hubei University of Technology for her help in sample preparation.
References
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