Abstract: A novel rapid temperature adjusting method is proposed and experimentally validated to find a solution to the issues of low temperature dropping efficiency and uneven temperature distribution in traditional roller hearth open-flame heat-treatment furnace. Traditional methods rely on natural cooling or simple forced air cooling systems, resulting in slow cooling rates (66 h to cool from 600 ℃ to 200 ℃) and uneven temperature distribution. This leads to significant variations in the mechanical properties of the steel plates, impacting product quality and production efficiency. The novel cooling method integrates five measures: ① alternating pulse cooling of the burners to improve both cooling rate and temperature uniformity; ② increasing furnace negative pressure while raising the furnace door to enhance cold air intake; ③ increasing the exhaust fan frequency to control furnace pressure; ④ auxiliary cooling by steel plate, large-specification steel plates to absorb heat; and ⑤ accelerating hot gas turbulence by increasing the frequency of the top circulating fan to promote better heat mixing within the furnace. Comparative tests on a roller hearth annealing furnace demonstrate that the novel method reduces the cooling time from 600 ℃ to 200 ℃ to 26.9 h, representing at least a two-fold increase in cooling rate. Mechanical property tests show that the steel plates treated with the novel method exhibit significantly lower transverse variations in tensile strength and yield strength (less than 0.40% and 0.41%, respectively) compared to the traditional method. This novel method significantly improves the production efficiency, enhances product quality, and offers substantial economic and environmental benefits.

Key words: green manufacturing, heat treatment furnace, temperature dropping method, production efficiency, temperature uniformity