Design of a flanged ring produced by hot forming using FE analysis

This paper describes the investigation for a ring rolling company aimed at designing, by means of FE analysis, the manufacturing steps involved in the production of a flanged ring, made of 42CrMo4 steel, used for power generation plants. Company engineers proposed the following hot forming cycle consisting in (i) upsetting, (ii) indenting, (iii) piercing and, (iv) ring rolling. The FE analysis conducted adopting the proposed design evidenced different problems (confirmed by a pre-production test operated at the company job shop) both in the forming of the initial ring and in the ring rolling process. The hot forming of the pierced perform exceeds the capacity of the presses available at the job shop. Therefore this part of the forming cycle was redesigned modifying the tooling, reducing the press stroke and adding a new upsetting stage with a flat die at the end of the hot piercing. Moreover the lack of material in the flanged part of the final ring and the excessive axial expansion of the ring suggested to reduce the height of the preform and to increase the diameter of the flanged zone. The new configuration of the perform sequence and main roller shape were successful in correcting both the axial expansion and the filling of the flanged zone, also keeping the required forming forces below the industrial limits.