Posted by
**lisa** on
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An undesirable consequence of welding steel by acetylene torch is the rise in hydrogen concentration in the metal. That hydrogen contamination embrittles the steel. The metal is typically subjected to a vacuum heat treatment to restore ductility. A steel part is placed in a vacuum furnace at 600∘C for one hour. The H concentration (initially uniform in the weld) falls to 1/2 its initial value at a depth of 500μm from the surface: It is known that the diffusivity of H in the steel at 600∘ C is 3.091×10−4 cm2/sec. An identical part is heat treated at 700∘ C. Under these conditions the H concentration falls to 1/2 its initial value at a depth of 500μm in 50 minutes. What is the diffusivity of H in steel at 700∘ C?

Give your answer in units of cm2/s, in scientific notation up to two decimal places