The relationship between length increment and holding time of high nickelat different operating temperatures is shown in the figure.It can be seen from the diagram that the length of high nickel ductile iron increases firstly and then tends to stabilize with the change of working time under 950 (?) C. The larger the working temperature is, the larger the stable size corresponds to. The stable growth is 0.028% at 850 (?) C, 0.038% at 900 (?) C and 0.042% at 950 (?).
Compared with high silicon-molybdenum ductile iron, the stable length growth of high nickel ductile iron at 850 C is only 45% of that of high silicon-molybdenum ductile iron, which is significantly lower than that of high silicon-molybdenum ductile iron.According to literature reports, the main reason is that the carbon equivalent of high nickel ductile iron (3.93) is lower than that of high silicon molybdenum ductile iron (4.67). On the other hand, high silicon molybdenum ductile iron is ferrite matrix and ferrite to austenite transformation occurs at high temperature; while high nickel ductile iron is austenitic matrix and does not occur phase transformation; at the same time, silicon can cause expansion coefficient to increase, so itsIn addition, the oxidation resistance of high nickel ductile iron is higher than that of high silicon molybdenum ductile iron.