Hot forging process desing and sensitivity analysis for long, thin and tubular coponents

Abstract

n closed die hot forging, high forging loads lead to wide part tolerances and make forging dies very susceptible to fatigue and wear failures. In particular, hot forging of 304L stainless steel is difficult compared to carbon and micro-alloyed steels in terms of forging load. Therefore, it is essential to investigate complicated design and process parameters in order to obtain an appropriate parameter combination that minimizes forging load without causing any under-filling or folding defects. Computer experiments using the finite element method under a full factorial design is very effective to demonstrate the main and interaction effects of the process factors on the forging load. The thesis mainly has two successive objectives. The first goal of the thesis is to develop a closed die hot forging manufacturing system for long, thin and tubular rail body component which is used in Gasoline Direct Injection system. The second goal of this research is to investigate the effects of the forging parameters including billet temperature, cross section diameter and flash land thickness on the forging load by using a full factorial array of 3 factors with 3 levels. It was concluded that increasing billet temperature and flash land thickness have decreasing effect on maximum force (load), while increasing billet cross section diameter has an increasing effect. By means of ANOVA, it was shown that all of the input factors have significant effects on the forging load.