0.0305 wt% for nitrogen of 130 ppm. An improvement to the consideration of feeding modulus is to use the simu- lated cooling curves to calculate the AlN embrittlement in the geometry.
The AlN embrittlement indicator is constructed using the simulated cooling curve at each point in the casting. The value of the indicator is the time spent inside the AlN phase precipitation curve. This calculation does not depend on as- suming a constant cooling rate or other assumption about the temperature field. Therefore the influence of the rigging is completely considered and may not even scale with the feeding modulus shown in earlier figures. Figure 7 shows the resulting AlN embrittlement indicator for a composition of aluminum 0.035 wt% and nitrogen 0.013 wt%.
Figure 8 shows the AlN embrittlement indicator for levels of aluminum on the casting with rigging included. Lowering the aluminum content from 0.035 to 0.03 wt% reduces the embrittled volume. According to the feeding modulus value alone, the lower aluminum level should be free of predicted AlN embrittlement. However, based on the actual cooling curves this volume is still predicting some embrittlement. At the highest nitrogen and aluminum level, the whole end of the casting is at risk of AlN embrittlement. At an aluminum
Figure 7. The color contour plot of time during embrittlement is shown. This is calculated for aluminum 0.035wt% and nitrogen 0.013wt%.
Figure 6. Comparison of feeding modulus on the geometry without and with rigging using the same scale from previous figure. Maximum feeding modulus location has changed.
International Journal of Metalcasting/Summer 10
Figure 8. The color contour plot of time during embrittlement is shown for two compositions of aluminum.
31
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81