The study is concerned with the development and analysis of warm press forming of invar shadow masks of the color cathode ray tube. In order to have an improved and more precise screen image, aluminum-killed decarbonized steel widely used for manufacturing shadow masks of cathode ray tubes has been replaced by invar sheet due to low thermal coefficient of heat expansion. However, invar sheet has high yield point and high springback property and is not amenable to press forming at the room temperature. Thus, invar sheet are subjected to warm press forming in order to obtain distortion-free shadow masks of high precision.
For analysis of the warm press forming of invar shdow masks, the temperature level and distribution are important for the control of the process. The rigid-viscoplastic finite element method is employed in order to analyze the heat transfer and temperature distribution of die. Bishop's step-wise decoupled method is employed in the frame work of the finite element analysis for thermomechanical interaction between deformation and heat transfer.
As an important process for shadow mask forming, the stretching phase has been analyzed by approximately the sectionwise plane strain condition and the effects of temperature in the punch and the die and punch speed, etc have been discussed.