Effects of grain size on the sheared surface in micropiercing of austenitic stainless steel SUS304

Abstract

Over the last decade, development of fine-grained materials and investigation into the effect of different grain sizes on metal forming at the micro-scale have been seen worldwide. There were several technical reports and scientific papers dealing with the quality improvements with use of the ultra-fine grained steel due to the different grain deformations. However, there were few studies concerning effect of the grain size on the sheared surface in micropiercing. In this study, we investigated stability of the sheared surface length of the cross section in micropierced holes. The inner diameter of the holes and maximum piercing forces were measured in order to evaluate the effect of the grain size in the micropiercing process. As reducing the material grain size, ratio of the fractured surface and maximum piercing force increased with tendency to tensile strength. However, the ratio of the burnished surface to the fractured surface as well as inner diameter of the pierced holes varied, depending on the grain size of the material. As a result, a suitable grain size should be considered for a micropiercing process.

Micro Forming and its Applications: An Overview

“…In this technique, the workpiece and explosive charge (in the form of a cartridge) are associated with each other while detonation is started at very high pressure around 30,000MPa over the workpiece surface as shown in Fig. 6 [80]. As a result of that deformation in a material is taking place and fracture possibly.…”

“…Explosive forming is commonly used for the manufacturing of parts in the aerospace industry and can be used in the production of automotive-related components [81]. The contact technique involves cladding, extruding and compaction of powder as well as helps in controlling the surface hardening of Hadfield steels [80]. The advantage of the contact technique involves forming complex shapes with higher accuracy over no machining or low machining is required with having no tool and presses cost is required [81].…”

“…The heat-assisted micro forming subjected to heating resistance provides high parts accuracy via heating to the workpiece and involves low energy consumption with a limited heat transfer rate over the tool [80]. This method is appropriately used for the utilization of energy to a low level; provides accuracy to the formed part which is associated with the heating of the workpiece that provides minimal heat to the apparatus.…”

“…The experimental setup involves mainly two probes which are inculcated into the die to retain the workpiece in association with the probe and required heating is being delivered [81]. Since, in Micro forming, the size of the specimen is small, there occurs an issue in dealing with a temperature that is under what range of temperature is supplied to the workpiece to accommodate high energy [80]. The temperature variation depends upon the shape of the workpiece and electrode position.…”

An integrated precise engineering for micro forming

“…For manufacturing micro metallic devices, the authors integrated the precise engineering technologies including the material development and the die fabrication. A micro pump was developed by using precise piercing and diffusion bonding processes with ultra-fine grain stainless steel foil (SUS304) [22]. Fig.…”