The New Technology of Die Forging of Automotive Connecting Rods from EN AB-71100 Aluminium Alloy Cast Preforms

Possibilities of Increasing the Durability of Dies Used in the Extrusion Process of Valve Forgings from Chrome-Nickel Steel by Using Alternative Materials from Hot-Work Tool Steels

This study refers to an analysis of the dies used in the first operation of producing a valve forging from chromium-nickel steel NC3015. The analyzed process of manufacturing forgings of exhaust valves is realized in the co-extrusion technology, followed by forging in closed dies. This type of technology is difficult to master, mainly due to the increased adhesion of the charge material to the tool substrate as well as the complex conditions of the tools' operations, which are caused by the cyclic thermo-mechanical loads and also the hard tribological conditions. The average durability of tools made from tool steel WLV (1.2365), subjected to thermal treatment and nitriding, equals about 1000 forgings. In order to perform an in-depth analysis, a complex analysis of the presently realized technology was conducted in combination with multi-variant numerical simulations. The obtained results showed numerous cracks on the tools, especially in the cross-section reduction area, as well as sticking of the forging material, which, with insufficient control of the tribological conditions, can cause premature wear of the dies. In order to increase the durability of forging dies, alternative materials made of hot work tool steels were used: QRO90 Supreme, W360, and Unimax. The preliminary tests showed that the best results were obtained for QRO90, as the average durability for the tools made of this steel equaled about 1200 forgings (with an increase in both the minimal and maximal values), with reference to the 1000 forgings for the material applied so far.

Investigation of a New Screw Press Forming Process for Manufacturing Connectors from ZK60 Magnesium Alloy Preforms

This article discusses a new technology of forming connector forgings from ZK60 magnesium alloy preforms by die forging on a screw press. The purpose of the study was to evaluate the feasibility of using preforms cast from the ZK60 magnesium alloy to forge a connector forging with improved mechanical properties compared to those obtained by casting. It also aimed to establish whether this new forging method has the potential for replacing the multi-stage forging process conducted on hydraulic presses used for high-strength Mg alloys. A numerical analysis of the proposed approach was performed by the finite element method, applying the popular DEFORM computer software for simulating forming processes. The numerical results confirmed that the developed method produces parts with the desired shape. The numerical results also provided information regarding the behavior of the workpiece's material and the screw press forging process, including the distributions of strains and temperatures, the Cockcroft-Latham damage criterion, and energy required to form connector forgings. The proposed screw press forging process for producing ZK60 alloy connectors from cast preforms was verified by experimental tests. The connector forgings produced from the ZK60 magnesium alloy were then subjected to qualitative tests.