PURPOSE: To equalize mechanical properties of products and to improve the production efficiency by inserting the low temp. zone part, containing a mandrel, of the rolling tail end side of a pipe stock into the high temp. heating zone of a reheating furnace, reheating the part, and reducing by which the part contracts or rolling by which the part has a constant diameter.
CONSTITUTION: A sensor 7 measures a temp. distribution of a shell 9 carried onto an inlet conveyer 6 of a reheating furnace 1 and the low temp. part length LZ and the total length LMM of the shell 9 necessary to control a charging position are detected. The above signals are inputted to a control part which controls a charging position so that the boundary part A between the low temp. part 11 and high temp. part 12 of the shell 9 coincides with the boundary B between the high temp. zone 5 and standard zone 4 of the furnace 1. The shell 9 is heated, extracted, and drawn to have a contracted shape or rolled to have a constant diameter. In that method, high quality products are obtained and the production efficiency is improved.
UTAKOJI MASARU
YOSHIOKA KOJI
