An iron-carbon alloy initially containing 0.258 wt% C is exposed to an oxygen-rich and virtually carbon-free atmosphere at 1120°C. Under these circumstances the carbon diffuses from the alloy and reacts at the surface with the oxygen in the atmosphere; that is, the carbon concentration at the surface position is maintained essentially at 0.0 wt% C. At what position will the carbon concentration be 0.194 wt% after a 6 h treatment? The value of D at 1120°C is 6.9 × 10-11 m2/s.

1.95 mm

Explanation:

Let's calculate the carbon conc. 0.194 wt% after a 6 h treatment using the expression:

From the erf z table, at erf(z) = 0.752

z = 0.80

Thus,

Where d =

Time, t = 6 hrs = (6 * 60mins * 60secs)

Substituting values:

Solve for x:

x = 1.95 mm

The position will the carbon concentration be 0.194 wt% after a 6 h treatment is at 1.95 mm

the equation above shows how temperature f, measured in degrees fahrenheit, relates to a temperature c, measured in degrees celsius. based on the equation, which of the following must be true?

a temperature increase of 1 degree fahrenheit is equivalent to a temperature increase of

5

9

degree celsius.

a temperature increase of 1 degree celsius is equivalent to a temperature increase of 1.8 degrees fahrenheit.

a temperature increase of

5

9

degree fahrenheit is equivalent to a temperature increase of 1 degree celsius.

a) i only

b) ii only

c) iii only

d) i and ii only