Action Planning for Improvement of Design and Operating Parameters of Ball-Bearing Steel Tube Annealing

Abstract

Annealing process was reviewed for hot rolled 100Cr6 steel tubes in a chamber furnace with subhearth burners. Based on the obtained results of thermotechnical testing at the chamber furnace it was detected that the current annealing curve conceptually do not allow production of satisfactory quality tube in the course of annealing. As a result an adjusted curve corresponding to the annealing requirements for 100Cr6 steel and chamber furnace capabilities was proposed. Causes were determined for poor quality tube annealing and detailed review was carried out for chamber furnace capabilities in terms of required heat treatment duration ensuring sufficiently high quality of annealed tubes. List of actions allowing significant improvement of chamber furnace performance and annealed tube quality was considered. Chamber furnace renovation option was proposed where the total heat treatment time of tubes may be reduced significantly through heat transfer process intensification in the furnace working space, uniformity of tube heating in the batch, annealing quality and therefore furnace performance may be improved.