8.53. Heat treating is often used to carbonize metal parts, such as gears. The thickness of the carbonized layer is a critical output variable from this process, and it is usually measured by performing a carbon analysis on the gear pitch (the top of the gear tooth). Six factors were studied in a design: A $ furnace temperature, B $ cycle time, C

$ carbon concentration, D $ duration of the carbonizing cycle, E $ carbon concentration of the diffuse cycle, and F $ duration of the diffuse cycle. The experiment is shown in Table P8.16.

(a) Estimate the factor effects and plot them on a normal probability plot. Select a tentative model.

(b) Perform appropriate statistical tests on the model.

(c) Analyze the residuals and comment on model adequacy.

(d) Interpret the results of this experiment. Assume that a layer thickness of between 140 and 160 is desirable.

Transcribed Image Text:

The Heat Treating Experiment Standard Run Order Order A B C D E F Pitch -2345678901 11 5782026 10 12 16 1 6 9 14 13 11 3 + 1 + 1 1 + 1 + 1 + 1 1 + - + 12 13 14 15 15 - 16 4 + + 1 ++ 1 1 - | ++ - ++ +1 1 + 1 T 1 1 + + + + + + + + +++ + 1 1 1 1 ++++ - 74 190 + 133 + 127 + 115 + 101 - 54 ++- + T + - 144 +121 +188 135 170 - 126 - 175 + 126 + 193