Experimental study on the effect of molybdenum on the properties of gray cast iron

HT250 finished brake hub produced by ZHY casting is melted in cy-sp35-vim temperature controlled high frequency induction furnace, argon is used as protective atmosphere, the heating rate is 50 ℃ / min, ferromolybdenum femo60 (particle size is 1 ~ 5 mm) is added after the temperature reaches 1600 ℃, and 0.5 wt% 75sife inoculant is added after holding for 15 min. In order to ensure the inoculation effect, stir with quartz rod for 10 s and cool to room temperature with the furnace.

The contents of S and C are determined by cs996 infrared carbon sulfur analyzer, and the contents of Si, Mn, Mo, P and other elements are measured by iris advantage Er / s inductively coupled plasma emission spectrometer. The composition of the sample is shown in Table 1.

Sample S1 in Table 1 is the reference sample, in which 0.034% Mo comes from the finished wheel hub itself. Samples S2 ~ S4 are alloyed with ferromolybdenum to increase the molybdenum content to 0.26% ~ 0.77%. After polishing, the sample was corroded with 4% Vol. nitric acid alcohol solution. The pearlite content was counted with Olympus dsx1000 three-dimensional digital microscope. The microstructure of the sample was observed with Evo ma10 scanning electron microscope and analyzed by energy spectrum. Classification and length analysis of graphite according to EN ISO 945-1 2017.

The sample melted in the above high-frequency induction furnace is only 0.5kg, which can not meet the size requirements of tensile sample. Therefore, based on the above experimental results, in order to verify the effect of molybdenum on the tensile strength of gray cast iron, the optimal amount of molybdenum is selected, melted and cast in a 25kg vacuum induction furnace Φ 30 mm Single cast test bar. The normal temperature tensile specimen is machined according to the dimensional requirements in Figure 1, and tested on dwd-200 universal tensile testing machine to determine its tensile strength.