Asked by Odesa

You wish to increase the carbon content of a slab of steel by exposing it to a carburizing atmosphere at elevated temperature. The carbon concentration in the steel before carburization is 193.5 ppm and is initially uniform through the thickness of the steel. The atmosphere of the carburizing furnace maintains a carbon concentration of 7865.0 ppm at the surface of the steel. Calculate the time required to carburize steel so that the concentration of carbon at a depth of 59.0 x 10-2 cm is one half the value of the carbon concentration at the surface. The diffusion coefficient of carbon in steel is 3.091 x 10-7 cm2/s at the carburizing temperature. Express your answer in hours.

DATA: Error Function Values
erf(ξ < 0.6), use the approximation erf ξ = ξ
erf(1.0) = 0.84
erf(2.0) = 0.998
Answered by BRA
777.78
Answered by Paul
No right!
Answered by Yamy
Don't think its a correct answer!
Answered by BRA
Corect Answer,
Use:

concentration of carbon at a depth
___________________________________

4*(3.091*10^-7)*0,26277
Answered by BRA
Corect Answer,
Use:
concentration of carbon at a depth//[
4*(3.091*10^-7)*0,26277]
Answered by Ling
Had 3.24888828e-07 but place 777.78 and had wrong answer. What when wrong?
Answered by MIT
DO NOT ANSWER THIS QUESTION, IT IS A MIDTERM QUESTION FOR AN ONLINE CLASS
Answered by Anon
What is 4
Answered by Anonymous
What is this formula and why the comma between 0.26277
Answered by qwerty
What is the formula?
Answered by qwerty
T(sec)= d^2 / 4*D*error^2
Answered by alq
Finally, what's the correct answer?
Answered by Yamy
Could someone fill the data above into the formula, so we can get an idea how to search the answer? Thank you
Answered by Ankur
Agree to Yamy
Answered by qwerty
Step 1:

(0.5*7865 - 7865)/ (193.5 - 7865)= erf(ξ)

Step 2:
erf(ξ < 0.6), use the approximation erf ξ = ξ

Step 3:

t= d^2/4*D*ξ^2

d=59.0 x 10-2 cm
D=3.091 x 10-7 cm2/s

Step 4:
t in sec -> hours
Answered by Yamy
Step 1:

(0.5*7865 - 7865)/ (193.5 - 7865)= 0.512611614417(erf(ξ))

Step 2:
erf(ξ < 0.6), use the approximation erf ξ = ξ

Step 3:

t= d^2/4*D*ξ^2
t=(59.0x10^-2)^2/4(3.091 x 10^-7)(0.512611614417)^2
t=0.3481/3.2488965297e-07
t=1071440.70862
d=59.0 x 10-2 cm
D=3.091 x 10-7 cm2/s

Step 4:
t in sec -> hours
1071440.70862/60x60
297.622419061 hours




0.78850182838 hours and had it wrong.

Answered by Odesa
Got the answer 297.622419061 hours.Thank you all for the advise, check through, and help, great way to make sure all of us don't use up our submissions. Again thank you bra, qwerty and yamy.
Answered by Antonio
This is a question from the second midterm of 3.091x by edx. Stop cheating, it's silly and pointless.
Answered by qpt
Thank you for the info, great help
Answered by ninja
But what is ξ??
Answered by ninja
how to find erf? error function ξ? and what is use of erf(1) and erf(2)??
Answered by qwerty
ξ= (0.5 * carbon concentration at the surface of the steel - carbon concentration at the surface of the steel)/ (carbon concentration in the steel before carburization - carbon concentration at the surface of the steel)
Answered by hk
You wish to increase the carbon content of a slab of steel by exposing it to a carburizing atmosphere at elevated temperature. The carbon concentration in the steel before carburization is 223.0 ppm and is initially uniform through the thickness of the steel. The atmosphere of the carburizing furnace maintains a carbon concentration of 6125.0 ppm at the surface of the steel. Calculate the time required to carburize steel so that the concentration of carbon at a depth of 84.5 x 10-2 cm is one half the value of the carbon concentration at the surface. The diffusion coefficient of carbon in steel is 3.091 x 10-7 cm2/s at the carburizing temperature. Express your answer in hours.

DATA: Error Function Values
erf(ξ 0.6), use the approximation erf ξ = ξ
erf(1.0) = 0.84
erf(2.0) = 0.998
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