20th International Forgemasters Meeting - IFM 2017

Main structural frames of Danieli Breda forging presses are made by welded parts. The design of their fatigue life is based upon an expected service loadtable, and on recognized international standards that provide database for evaluation of fatigue performances of each type of welded joint. All the available recognised standards are based on experimental tests from civil structures, or from oil-and-gas\naval engineering, thus covering joints whose tickness is very small compared with the ones existing in a frame of a large forging press. Additional corrections coefficients are provided for accounting of higher thickness joints. From experiences derived by many forging plants delivered in the years by Danieli Breda, it appears that such correction for high thickness plates are quite conservative. A numerical investigation on this point has been developed, followed by experimental activities on typical joints executed according to Danieli procedures, to find out the actual fatigue performances of large weldings. Even a limited upgrade, in the resulting S-N curves for this kind of weldings, has an appreciable impact on the design and economical approach of both the construction and operative service of a forging press. In the design step, once given a loadtable, it is possible to reduce the weight and the dimensions of the structural frames of the press, so reducing its dimensions (mainly its heigth), thus weight and costs. For presses already in service, it is possible to extend their expected service life and rescheduling the stops of the plant for periodical NDT ispections