MACHINABILITY CAST IRON
The effect of aging on material properties determines the optimal machining time.
T
SIMON N. LEKAKH AND VON L. RICHARDS, MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY, ROLLA, MISSOURI
here are various ways to improve casting machinability. Natural aging’s eff ect on cast iron machinability dif- fers based on its alloying elements, which are nitride- forming (titanium), carbide-forming (chromium) and nitrogen mobility modifi ers (manganese). Relationships between cast iron aging and casting machinability have been verifi ed in multiple laboratory and industrial tests, with respect to parameters such as cutting force, tool wear, surface quality and dimensional accuracy. A recent confi rmation test verifi ed the optimal aging time for a
specifi c composition to improve gray iron machinability.
Cast Iron Natural Aging Understanding how age strengthening aff ects machinability enables manufac-
turers to schedule the optimal window for machining. Room-temperature aging phenomena has been documented for diff erent types of ferrous alloys, including cast irons and steels. In gray cast iron, tensile strength increased by 5%-15% after 5-30 days of room-temperature aging. Aging studies in quenched iron-based alloys indicated a three-stage precipita-
tion process. In some cases, a dip in strength is observed during the start of the aging process. Elevated temperature aging kinetics in the cast iron revealed typical
Aging sometimes improves iron casting machinability, depending on its mate- rial properties.
Fig. 1. These graphs show strengthening of cast iron during aging (a) at room temperature, (b) at 360F (182C) and (c) at 545F (285C). Sept/Oct 2013 | METAL CASTING DESIGN & PURCHASING | 25
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