API 571 Certification (Corrosion & Materials) Practice Test

Which steel grades are commonly used and included in spheroidization susceptibility?

1. C-0.5Mo and 1Cr

2. 410 Stainless Steel

3. Alloy 600

4. Cast Iron

The correct answer is: C-0.5Mo and 1Cr

Spheroidization susceptibility relates to the ability of a steel to undergo a microstructural change where the cementite phase (Fe3C) forms spheroidal particles within a ferritic matrix. This is particularly significant for steels that contain alloying elements, such as molybdenum and chromium, which influence the stability and transformation of the microstructure during heat treatment processes. The steels that are commonly associated with spheroidization susceptibility typically include those that have carbon content and specific alloying elements. In this case, the correct choice refers to steel grades C-0.5Mo and 1Cr. Both these compositions feature the right combination of carbon and molybdenum or chromium that can facilitate the spheroidization process. Lower carbon steels with specific alloy content undergo spheroidization at elevated temperatures, making them more susceptible. In contrast, the other options do not primarily emphasize the spheroidization process. For instance, 410 Stainless Steel is primarily known for its hardness and corrosion resistance but does not undergo spheroidization in a meaningful way. Alloy 600, on the other hand, is known for its strong resistance to oxidation and corrosion at high temperatures, not for spheroidization susceptibility. Lastly, cast iron does not fall under this