Discussion on Common Problems as Staying with Push-type Tube Hot-expanding Process with Local Medium-frequency Induction Heating

Discussed here in the essay are the problems as commonly encountered with the push-type tube hot-expanding process with local mid-frequency induction heating,and also mentioned are common defects of the hot-expanded tube,and relevant improvement measures. It is concluded that speaking of the mother tube as subjected to the hot-expanding process,the steel chemical composition should be properly controlled with consideration of relevant factors that possibly reduce the after-expanding mechanical properties of the material,and the chemical elements like C and Mn,etc. that may influence the steel strength should be controlled as far as possible within the upper limit ranges;and the hot-rolled mother tube must be subjected to online quench-temper treatment or offline normalization treatment to further refine the grain. It is also suggested to attach importance to inner surface graphite lubrication of the mother tube,and the preparation of the tube expanding core mould,and to conduct careful check of the mother tube quality via various measures,including NDT.