Carbide precipitation occurs in some stainless steels when they are kept at a temperature between ____ degrees Fahrenheit for a long period of time.

• A. 800 and 1500
• B. 1700 and 2100
• C. 1500 and 2100
• D. 1000 and 2100

Answer: (A)

Carbide precipitation occurs in stainless steels when they are held at an intermediate temperature for a long period, a phenomenon known as sensitization. At these temperatures, carbon can diffuse to grain boundaries and form chromium carbides, which deplete chromium in the surrounding areas. That chromium depletion at the grain boundaries weakens the steel’s resistance to intergranular corrosion when exposed to corrosive environments.

The most active window for this diffusion-driven precipitation is about 800 to 1500 °F. Below this range, diffusion is too slow for significant carbide formation; above it, the carbides tend to dissolve or other transformations occur, so the same sustained precipitation doesn’t happen. So, the correct range is 800 to 1500 °F.