A company will use a belt conveyor oven from Grieve, Round Lake, Ill., to heat treat coiled spring steel.
 
The oven has workspace dimensions measuring 18” wide by 20’ deep by 15” high. The oven travel comprises a 1.5’ long open belt loading zone, 20’ long insulated heat zone with recirculated airflow, 1’ long open zone, 12’ long cooling zone and 1.5’ long open unloading zone. Controls include a 10” diameter circular chart recording temperature controller and a manual reset excess temperature controller.
 
(Source: http://www.process-heating.com/articles/91767-oven-can-heat-treat-coiled-spring-steel)