Preparation And Investigation On Microstructure And Properties Of Minor Diameter Cast Iron Section Bars

With the extension of the horizontal continuous casting technology, cast iron section bars are wider and wider applied to each domain of industry. Through optimizing the relevant continuous iron-casting technological parameters, and making minor diameter cast iron section bars with several different cross-section areas, and from the characteristics of solidification and forming of the cast-iron section bars, the paper analyzes and researches on the corresponding relationship between its structure and property and draws the following conclusion:1. The metallographic structure characteristics of minor diameter cast iron section bars is that there are developed primary austenite dendrite crystal and fine D-type graphite distributed among dendrite crystals.2. The hardness test result of the minor diameter cast iron section bars show that the cast iron section bars are of more even hardness, the hardness is between HB190～220, the hardness difference is only HB±15.3. The tested tensile strength of the minor diameter cast iron section bars are all over 320MPa, their mechanical property is good.4. It is got from the stretching fracture that the main function of the austenite dendrite crystal during the course of fracture is to stop the spread of the crack, increase the energy needed for fracture, and improve the cast-iron bars' strength.5. The analysis of the structure and break of the minor diameter cast iron bars shows that developed primary austenite dendrites distribute in framework; With the high-power electron microscope to observe the D-type graphite between dendrites, the graphite is approximately worm-shaped or coral-shaped. That is the basic reason why the minor diameter cast iron section bars are of high strength.