Effect Of Modification On Microstructure And Properties Of Permanent-mould High Chromium Cast Iron

From the view of to improve the toughness of the material, reduce the production cost and improve its service life, on the basis of not reducing the properties of high chromium cast iron, to join the other trace elements in high chromium cast iron, by refining the organization, improving the carbide morphology and distribution, so that the performance and service life to improve at the same time. Modification is an important means to improve casting performance, which is simple and low cost.In this experiment, to study the influences of the different metamorphic agent on the microstructure and properties of high chromium cast iron by permanent-mould casting under laboratory conditions with the centrifugal casting of Shandong province Zibo Jintai roll Co. Ltd for high chromium cast iron as raw material. In this paper, examines the influences law of different content of boron, rare earth magnesium and molybdenum of high chromium cast iron, phase, hardness, impact toughness tensile strength, and corrosion resistance performance by means of optical microscope, scanning electron microscope, X-ray diffraction, rockwell hardness tester, universal testing machine and other analysis method, through contrast experiment method. Experimental results are shown as follows:(1) Boron replace part of carbon and chromium forming boride(Fe,Cr)7(C,B)3 and Fe23(C,B)6 type carbide in high chromium cast iron after adding boron metamorphism.The morphology and distribution of carbide has the obvious change, carbide becomesisolated lumps vermicular and spheroidal distribution from the sharp edges of the strip shape and good continuity of reticular, structure refinement, and isolation degree obviously. Tensile strength, the impact toughness, hardness, corrosion resistance of high chromium cast iron has improved with increase of boron content.(2) To add rare earth magnesium in high chromium cast iron, the organization do not appear in the new phase, but the carbide with coarse, a flake or long strip, sharp form into clumps and fine fishbone, separate effect on the matrix decrease obviously.It is of great advantage to improve the toughness of high chromiumcast iron.The mechanical properties of high chromium cast iron has overall ascensionwith addition of rare earth magnesium, while the content of rare earth magnesium added is 0.6wt%, the mechanical properties have reached the maximum and corrosion resistanceis exhibits desirable.(3) Adding proper amount of Mo can significantly improve the hardenability of high chromium cast iron, but also create new material Mo2 Cto make high chromium cast iron hardness values reaches 62 HRC.At this point the carbide morphology and distribution also have varying degrees of change, carbide change by the long strip into the strip of isolated sphericaland the increase in the number and organization obviously refined.When the addition of molybdenum is 0.6wt%, the comprehensive mechanical properties of high chromium cast iron exhibits desirable.