Mechanical and Thermal Influences on Microstructural and Mechanical Properties during Process-Integrated Thermomechanically Controlled Forging of Tempering Steel AISI 4140

Abstract

Thermomechanical treatment (TMT) describes the effect of thermal and mechanical conditions on the microstructure of materials during processing and offers possible integration in the forging process. TMT materials exhibit a fine-grained microstructure, leading to excellent mechanical properties. In this study, a two-step TMT upsetting process with intermediate cooling is used to demonstrate possibilities for a process-integrated treatment and corresponding properties. A water–air-based cooling system was designed to adjust different phase configurations by varying the target temperature and cooling rate. Four different thermal processing routes and four combinations of applied plastic strains are investigated in standardized mechanical tests and metallographic analyses. The applied TMT results in a finely structured bainitic microstructure of the investigated tempering steel AISI 4140 (42CrMo4) with different characteristics depending on the forming conditions. It can be shown that the demands of the standard (DIN EN ISO 683) in a quenched and tempered state can be fulfilled by means of appropriate forming conditions. The yield strength can be enhanced up to 1174 MPa while elongation at break is about 12.6% and absorbed impact energy reaches 58.5 J without additional heat treatment when the material is formed after rapid cooling.

On the Tribological and Oxidation Study of Xanthophylls as Natural Additives in Castor Oil for Green Lubrication

“…These experiments were accomplished using a tribometer from CSM Instruments, Needham (MA), USA with a ball-on-disk configuration, based on the ASTM G-99 standard. For this evaluation, disks of AISI 4140 steel were used because this material is one of the most employed steel in the industry due to its notable mechanical properties [ 21 ]. Whereas commercial balls of tungsten carbide (WC) were employed as counterparts.…”

Thermo-mechanical forging of 708M40 steel ring samples: experiments and modelling

“…Bernd et al [4] performed a two-stage forging process on AISI 4140 to deliver excellent mechanical properties. The first forging stage was conducted at 1200°C to generate the bulk deformation and a secondary thermo-mechanical forming operation at 800°C which resulted in reduced formability and increased required forming forces, but this was necessary to prevent grain growth and promote fine grain areas which deliver enhanced mechanical properties.…”