Factors affecting scaling of furnace stock The rate at which oxide scale forms on heated stock is governed by which combination of variables?

Introduction / Context:
Scaling is oxidation of metal surfaces at elevated temperatures. In reheating and heat treatment, minimizing scale is essential to preserve surface quality and reduce material losses.

Given Data / Assumptions:

• Oxidizing environments promote scale formation.
• Kinetics are temperature and time dependent.

Concept / Approach:
Oxidation rates typically increase strongly with temperature (Arrhenius-type behavior). Longer exposure time increases total scale thickness. The furnace atmosphere (oxidizing vs reducing, moisture content, CO2/CO ratio) also changes the oxidation rate and type of scale formed. Thus, temperature, time, and atmosphere all matter.

Step-by-Step Solution:

Verification / Alternative check:
Practical data show reduced scaling with shorter cycles and controlled (less oxidizing) atmospheres at a given temperature.

Why Other Options Are Wrong:

Common Pitfalls:
Overheating periods “just to be safe,” which disproportionately increases scale due to strong temperature sensitivity.

Final Answer:
all (a), (b) and (c)