Simulation-Assisted Production of Stainless Steel Fasteners Using Pre-Deformed Raw Material by Cold Forging Method

Abstract

The initial properties of the raw material used while producing by cold forging change the mechanical properties of the final product resulting from deformation. Depending on the amount and speed of deformation, there is an increase in strength and a decrease in formability after cold forging on the basis of the true stress - strain curve of the material. In this study, pre-deformation of 304Cu (1.4567) quality raw material used to produce fasteners in A2-70 class by wire drawing before forging and the change of the mechanical properties of the raw material, on the basis of this change, the simulation supported design of the fastener mold and process was carried out. Simufact.forming software was used in cold forging simulation studies. According to the simulation data, the yield strength value increased from 215 MPa to 620 MPa as a result of thinning the raw material from Ø7.80 mm to Ø6.95 mm with wire drawing operation. In this case, the properties of the raw materials entering the cold forging have changed according to the deformation percentage amount, and the material properties and mold design used in the finite element simulation supported production were made according to this data. As a result of the use of this raw material in the cold forging simulation, the HV10 hardness value in the fastener head region, where deformation is intense on the basis of the die geometry, has reached the levels of 320 to 340 HV. Material flow lines, product dimensional tolerances, rolling and thread cutting processes during deformation were verified in the computer environment and physical product production was made. Hardness, strength and structural checks were performed and compared with numerical model values. Especially, the changing material properties as a result of the wire drawing process applied to the starting raw material and its effect on cold forging were investigated mechanically and metallographically.