Table 1 summarizes the 12 pours. After each pour, the casting was al- lowed to cool and broken out. Te tubes were cut from the feeder and inspected. Each tube was visually inspected followed by X-ray and liquid penetrant inspection. Figure 4 shows all 12 sets of
tubes. Each smaller picture con- tains two sets of tubes, all with the same inner diameter, and two tubes of each of the six lengths of core.
Looking for Defects The tubes were first evaluated
Fig. 4. A total of 72 castings were created, two for each of the test conditions.
for defects during pouring. Fig- ure 5 shows an end view of one of each diameter of tubes. There is an obvious eccentricity of the core in the 0.25-in. tube, but the others appeared concentric. The lack of deformation in the larger diameter tubes was confirmed by X-ray inspection. The deforma- tion of the small tube was great enough that, in longer lengths, part of the tube did not fill, as shown in Figure 6. Non-fill due to core deformation is clearly visible in the 8-, 10- and 12-in. tubes. Non-fill conditions were not found in any larger diameter tubes.
Liquid penetrant inspection
revealed a number of gas defects, such as those shown in Figure 7. In some cases, a pit is obvious in the cases of larger defects. Te presence of the gas defects raised two ques- tions: What was the source of the gas? Why didn’t the core venting allow the gas to escape? If the source of the gas was the binder in the core, such de- fects may be difficult to avoid in any casting. The other gas defects in the cast tubes showed two definite trends: • Defects increased with in- creased pouring height.
• Smaller diameter tubes had fewer defects.
If the binder was the source of the gas, similar defect levels should be found in all castings. However, defects were more
30 | METAL CASTING DESIGN & PURCHASING | Nov/Dec 2015
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