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Monotonic Mechanical Properties


Table 3 shows the monotonic mechanical properties that were obtained for the selected grades. Figure 18 shows a plot of yield strength versus elongation for all eight selected conditions. Selected mechanical properties are also plotted versus ferrite content in Figures 19 and 20 for the three as- cast conditions.


The monotonic mechanical properties in the as-cast condi- tion obeyed expectations as follows:


1. Figure 18 shows that the yield strengths of the fer- ritic, ferritic-pearlitic, and pearlitic irons decreased with increasing elongation.


2. Figure 19 shows that the hardness, yield strength and tensile strength increased with decreasing ferrite content in the as-cast conditions.


3. Figure 19 shows that the ductility, as measured by both elongation and reduction in area, increased with increasing ferrite content in the as- cast conditions.


The monotonic mechanical properties were altered with heat treatment for the two grades that were evaluated, but less predict- ably. The following heat treatment trends were observed:


1. Table 3 shows that the tensile strength of as-cast grade 60-40-18 decreased slightly with subcritical annealing and decreased signifi- cantly with full annealing.


2. Table 3 shows that the yield strength of as-cast grade 60-40-18 decreased slightly with subcritical annealing and decreased signifi- cantly with full annealing.


3. Table 3 shows that the ductility of as-cast grade 60-40-18 hardly changed with subcritical anneal- ing; however, significant increas- es in ductility were obtained with full annealing.


4. Table 3 shows that the yield and tensile strengths of the normal- ized 100-70-03 grade increased significantly with respect to the as-cast 100-70-03 grade in both the 25 mm and 76 mm section sizes. (In fact, the 100-70-03 properties are not generally ob- tainable in a heavy section size without normalizing.)


18


5. Table 3 shows that ductility of the 25 mm as-cast samples of the 100-70-03 grade did not change when they were normalized.


6. Table 3 shows that the ductility of the normalized 76 mm samples was significantly lower than the 25 mm samples of the 100-70-03.


7. Figure 18 shows that quenched and tempered (Q&T) grade 120-90-02 had a significantly higher yield strength at the same ductility of the pearlitic 100-70-03 grade.


No significant change in the elastic properties (modu- lus and Poisson’s ratio) were observed for any of the conditions.


Figure 19. The hardness and strength decreased with increasing ferrite content for the as-cast conditions.


Figure 20. The ductility increased with increasing ferrite content for the as-cast conditions.


International Journal of Metalcasting/Spring 2012


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