Wear Analysis of Forging Tools Used in an Industrial Production Process—Hot Forging in Closed Dies of the “Head-Disk” of an Engine Valve Forging

Abstract

The article performs an analysis of the durability of punches applied in the process of producing a valve forging from chromium-nickel steel. A forging of this type is made in two operations: coextrusion of a long shank, followed by finishing forging in closed dies of the valve head. The product obtained in this way (after other additional finishing procedures) constitutes the key element of the combustion engine (resistant to high pressures and temperatures) in motor trucks. Unfortunately, a significant problem in this production process is a relatively low durability of the forging tools, especially the punch used in the second forging operation. The key element at this stage, deciding about the punch’s further operation, is the area of the so-called “calotte”. The short-term life of the tools results from very hard performance conditions present during the forging process (periodical high mechanical and thermal loads, long path of friction). The latter cause intensive abrasive wear as well as high adhesion of the forging material to the tool surface. Based on the performed studies, including the following: technology analysis, numerical modelling, macro analyses combined with 3D scanning of tool sections as well as microstructural tests and hardness measurements, it was established that it is crucial to properly select the process parameters (charge and tool temperature, tribological conditions), as even slight changes introduced into them significantly affect the operation time of the forging tools. Mastering and proper implementation of the analyzed forging technology requires numerous further studies and tests, which will enable its perfection and thus increase the durability of the tools as well as the quality of the produced items.

Possibilities of Increasing the Durability of Punches Used in the Forging Process in Closed Dies of Valve Forgings by Using Alternative Materials from Tool Steels and Sintered Carbides

“…This article presents results regarding the possibility of increasing the durability of tools by using one of the easiest to evaluate methods, the obtained results of which are also easy to interpret, i.e., the method of increasing the durability of forging punches, which involves the use of an alternative tool material. This approach has been confirmed in many works [51][52][53], as it is one of the cheapest and relatively easy-to-analyze methods of increasing the durability of forging tools.…”

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

“…So, in order to properly choose the tool material, we need to largely depend on the experience of the tool steel producers as well as the users of the tools, i.e., die forges [37,38]. At the same time, we should emphasize that, among the whole spectrum of available steels, there is none that would fulfill the expectations of the production in a complex way; so, while choosing the tool material [39], we can mostly base our decisions on the experience of the steel producers as well as the people directly connected with the production process [40]. The most common forging tool material used in forging processes are warm and hot operation tool steels, that is, 1.2343, 1.2344, 1.2367, 1.2999, etc., which are characterized by very good mechanical properties (high tensile strength and hardness, high abrasion resistance, high yield point of 2200 MPa).…”

Surface Inspection and Description in Metrology and Tribology—Vol.1

“…This was reported by many scientists for cutting tools [39], or working pairs [40], including numerical and qualitative characterization [41]. In this book, Hawryluk et al [42] presented an analysis of the durability of punches applied when manufacturing chromiumnickel steel valves for combustion engines by forging in two operations-coextrusion of a long shank, and forging valve head in closed dies. Due to intensive abrasive wear, as well as high adhesion of the forging material to the tool surface durability of the forging tools is rather low.…”