1 Fig. 1. Shown is the workpiece for machinability testing of cast iron used in this study.
Background Metal makers have used a
variety of machining proce- dures and measuring methods to quantify the machinability
of their products. T ey usually simu- late their major customers’ machining procedure such as turning, milling, and drilling. During the machining procedure they measure response at- tributes such as surface roughness, chip form, part tolerance, cutting forces and cutting tool wear and/or failure. Finn chose to measure cutting tool wear as the response attribute while face tun- ing cast iron discs. Face turning cast iron discs simulates the surface milling procedure used most often in making parts from cast iron. T e procedure in the ASTM E618-81 specifi cation is the only standard machinability testing methodology for metal alloys, namely for cold rolled bars. It is not applicable to disc workpieces and the shapes and sizes of cast iron products. Many metal makers use a modifi cation of the ISO 3685-1977(E) cutting tool life test in turning of wrought and cast bars. A modifi ed cutting tool life test is being used by members of the Bar Machinability Subcommittee of the Steel Market Development Institute (a business unit of the American Iron and Steel Institute). T e steel makers have developed a database of machinability values for automotive bar steel for 36 carbon, alloy, resulfurized and microal- loyed steel grades. Finn’s research took a similar approach. Face turning cast discs, however, required factorial de- signed tests to determine the optimum cutting tool type and geometry that wore the cutting tool uniformly without catastrophic failure. Additional studies were required to optimize the depth of cut (DOC). A compromise DOC was selected that would not rotate the disc in the chuck and wear the cutting tool edge enough to measure under a microscope. Cutting fl uid type and ma- chining parameters were also optimized to eff ectively and economically measure the machinability values. Finn and his group determined the machinability values for fi ve grades of gray and ductile cast iron, while AFS compiled values for other grades from metalcasters using the new testing procedure.
34 | METAL CASTING DESIGN & PURCHASING | Mar/Apr 2013
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