Analysis of multistage deep drawing with ironing was made while manufacturing of cups from 12 mm thick, 60 mm diameter circular blanks of Al-killed AISI 1040 graded medium carbon steel. Quality requirements of the steel in heat treated condition were examined in terms of tensile properties, formability characteristics, and formability limit diagram. Drawability and ironability parameters in multistage cup drawing processes were evaluated in terms of draw ratio; draw reduction; ironing ratio; ironing reduction and thus its press formability in an actual state of practice was shown. Further, were analysed the influences of process parameters such as: semi die angle; interfacial friction coefficient; die-punch clearance on draw and ironing punch forces in each draw stage. The spring back tendency of cups in terms of their trends and degrees with respect to cup heights and draw stages were experimentally determined by conducting split ring test. Thus, a data bank was created as potential references for process engineers to improve the manufacturing process and draw tools as well, particularly for the selected steel.
In this paper a new modified processing route has been proposed for producing long cylindrical cups from 12 mm thick circular blanks of AISI 1020 steel (Aluminium (Al) -killed). In this route, flat blanks were made to preformed shape by stamping operation, followed by multistage deep drawing processes(without blank-holder and with inter-stage stress relief annealing) to increase cup depth. Wall ironing was also purposefully included in each draw step to reduce wall thickness and earing tendency on cup edges. Thus, evolution of wall thickness distribution, Drawability and Ironability, punch force history, and strain distribution profiles on outer cup surfaces were obtained as the effects of interaction between processes, tools and material. The overall draw stages showed: LDR 2.06; overall draw reduction >50% with a drawing efficiency ~72%; LIR 3.55; overall ironing reduction >70% with an ironing efficiency ~68%, which were achieved in the experimental works.
The basic formability of Aluminum-killed AISI 1040 graded medium carbon steel (cold rolled followed by hardening and spheroidization tempering) has been characterized by uniaxial tension, compression, bending, and Erichsen cup tests.The results shows a good strength (~634 MPa) -ductility combination, high strain hardening exponent, normal plastic anisotropy value > 1 and a considerably low planar anisotropy. The compressibility, bendability and biaxial strechability characteristics of the steel also signify its formability behavior in different loading states. The strain analysis on tensile and Erichsen cup specimens has provided deeper information on its strain dispersibility as well as necking tendency in both uniaxial and biaxial states.The actual press formability also has been investigated by applying a process consisting of multistage deep drawing accompanied with wall ironing, without using blank holder and with intermediate stress relieving treatment. Thus ~56 mm long cylindrical cups, ~36.85 mm diameter and ~3.8 mm wall thickness, have been manufactured from 12 mm thick and 60 mm diameter circular blanks in a preformed shape. This experiment has yielded significant values of few press formability parameters in terms of draw ratio, draw reduction, ironing ratio, ironing reduction and etc. Further, by drawing comparisons with few sheet metals, the competitiveness of the steel has been shown with an objective to enlighten on its line of applications as per customer demands. KEY WORDS: Aluminum-killed AISI 1040 graded medium carbon steel; formability; multistage deep drawing; wall ironing; cylindrical cup.
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