Based on the above experimental results, in order to verify the effect of molybdenum on the tensile strength of gray cast iron, two groups of samples with molybdenum content of 0.024% and 0.8% were melted by vacuum induction melting according to the test requirements of gray cast iron (GB / t9439-2010), and the tensile strength of gray cast iron was tested. The final chemical composition and tensile strength of room temperature grey cast iron of the sample are shown in Table 2. The tensile strength of room temperature grey cast iron of the sample increases from 254 MPa of reference sample Z1 (0.024% Mo) to 368 MPa of sample Z2 (0.8% Mo). Therefore, adding molybdenum to gray cast iron can effectively improve the tensile strength of gray cast iron.
(1) With the increase of molybdenum content in gray cast iron, the length and quantity of graphite become shorter, the area fraction of graphite decreases slightly, and the graphite tends to coarsen;
(2) The pearlite content decreases with the increase of molybdenum content, but molybdenum has a strong ability to reduce the pearlite lamellar spacing and refine the pearlite structure. When the addition of molybdenum increased from 0.034% to 0.77%, the average lamellar spacing of pearlite decreased from 395 nm to 229 nm;
(3) Molybdenum carbide precipitates in austenite or grain boundary in strip or rod shape. When pearlite transformation occurs in grain, molybdenum carbide in grain can induce pearlite to precipitate from austenite and form pearlite structure with different orientation, which plays the role of refining pearlite grain;
(4) The experimental results show that when the molybdenum content increases from 0.024% to 0.8%, the tensile strength of gray cast iron increases from 254 MPa to 368 MPa. Therefore, adding an appropriate amount of molybdenum to the gray cast iron hub is an effective way to improve its tensile strength.