Question

For a steel alloy, it has been determined that a carburizing heat treatment of 10-h duration will raise the carbon concentration to 0.45 wt at a point 2.5 mm from the surface. What is the carbon concentration at the surface?

1) 0.45 wt
2) Cannot be determined
3) 0.45 wt or higher
4) 0.45 wt or lower

Answer 1

After carburizing, the carbon concentration at a steel alloy surface will be 0.45 wt% or higher, with the highest concentration at the surface, decreasing with depth.

Step-by-step explanation:

The question is about the carbon concentration on the surface of a steel alloy after carburizing, a process that increases the surface carbon content of steel to improve its properties. After a 10-hour treatment, the carbon concentration is 0.45 wt% at a point 2.5 mm from the surface. Understanding that carburizing creates a gradient where the surface will have the highest carbon concentration, we can infer that the carbon concentration at the surface will be 0.45 wt% or higher. The process enriches the surface first, then the carbon diffuses inward, meaning the exterior will always have a higher or equal concentration to a point beneath it after the process is complete. Therefore, the correct answer is option 3) 0.45 wt% or higher.