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Influence of the nitrided layer thickness of dies made of two types of tool steel used in hot extrusion of valve forgings made of nickel–chromium steel on the durability of these tools

Hawryluk Marek, Lachowicz Marzena, Janik Marta, Ziemba Jacek, Gronostajski Zbigniew

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 4

277--293

EN

The study constitutes an analysis of the durability of dies used in the first operation of producing valve forgings from chromium–nickel steel (NCF 3015) for motor trucks. The average durability of the dies (subjected to standard thermal treatment and nitriding) in this operation equals about 800 forgings. To perform an in-depth analysis of the effect of the nitrided layer thickness (0.1 mm and 0.2 mm) and the tool material (W360 and QRO90) on the possibilities of increasing the die durability, complex studies were carried out, which included: a macroscopic analysis combined with 3D scanning, microstructural examinations using a scanning microscope and a metallographic microscope, as well as hardness measurements. A minimum of three tools were tested for different variants, and for each of them, one representative die was selected for detailed examinations. The research showed the presence of abrasive wear, thermo-mechanical fatigue and traces of adhesive wear as well as plastic deformation on the surface of the working impressions. Also observed was the effect of the extruded material sticking to the tools (high friction and the presence of intermetallic phases in the extruded material) and the forging being blocked in the smallest section of the die, which is a critical factor causing a production shutdown and the necessity of tool replacement. The highest mean durability equalling 2600 forgings was obtained for the dies with a lower carbon content and a higher content of vanadium and the nitrided layer thickness at the level of 0.2 mm. The lowest mean durability (after one forging item) was recorded for the dies made of steel with a higher carbon content and a higher chromium content, forming less stable compound carbides and the thickness layer at the level of 0.1 mm.

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Wear Mechanisms Analysis of Dies Used in the Process of Hot Forging a Valve Made of High Nickel Steel

Hawryluk M., Gronostajski Z., Kaszuba M., Krawczyk J., Widomski P., Ziemba J., Zwierzchowski M., Janik M.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 4

1963--1974

EN

The study presents a durability analysis of dies used in the first operation of producing a valve-type forging from high nickel steel assigned to be applied in motor truck engines. The analyzed process of producing exhaust valves is realized in the forward extrusion technology and next through forging in closed dies. It is difficult to master, mainly due to the increased adhesion of the charge material (high nickel steel) to the tool’s substrate. The mean durability of tools made of tool steel W360, subjected to thermal treatment and nitriding, equals about 1000 forgings. In order to perform a thorough analysis, complex investigations were carried out, which included: a macroscopic analysis combined with laser scanning, numerical modelling by FEM, microstructural tests on a scanning electron microscopy and light microscopy (metallographic), as well as hardness tests. The preliminary results showed the presence of traces of abrasive wear, fatigue cracks as well as traces of adhesive wear and plastic deformation on the surface of the dies. Also, the effect of the forging material being stuck to the tool surface was observed, caused by the excessive friction in the forging’s contact with the tool and the presence of intermetallic phases in the nickel-chromium steel. The obtained results demonstrated numerous tool cracks, excessive friction, especially in the area of sectional reduction, as well as sticking of the forging material, which, with insufficient control of the tribological conditions, may be the cause of premature wear of the dies.

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Durability analysis of forging tools after different variants of surface treatment using a decision-support system based on artificial neural networks

Mrzygłód B., Hawryluk M., Gronostajski Z., Opaliński A., Kaszuba M., Polak S., Widomski P., Ziemba J., Zwierzchowski M.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 4

1079--1091

EN

This article concerns a decision-support system based on artificial neural networks (ANN) enabling analysis and forecasting of the durability of forging tools used in the hot forging process of a cover forging – a sealing element of the driveshaft in road freight vehicles. The process of knowledge acquisition, adopted neural network architecture and parameters of the developed network are presented. In addition, 3 variants of a hybrid layer (gas nitrided layer GN + PVD coating) were applied to the selected tools (punches applied in the 2nd top forging operation): GN/AlCrTiN, GN/AlCrTiSiN, and GN/CrN, in order to improve durability, and the resultant tools were also compared to standard tools (with only gas nitriding) and regenerated tools (after repair welding regeneration). The indispensable knowledge about the durability of selected forging tools (after various surface engineering variants), required for the process of learning, testing and validation for various neural network architectures was obtained from comprehensive, multi-year studies. These studies covered, among other things: operational observation of the forging process, macroscopic analysis combined with scanning of tools’ working surfaces, microhardness measurements, microstructural analysis and numerical modeling of the forging process. The developed machine-learning dataset was a collection of approx. 900 knowledge records. The input (independent) variables were: number of forgings manufactures, pressing forces, temperature on selected tool surfaces, friction path and type of protective layer applied to tool. Meanwhile, output (dependent) variables were: geometrical loss of tool material and percentage share of the four main destructive mechanisms. Obtained results indicate the validity of employing ANN-based IT tools to build decision-support systems for the purpose of analyzing and forecasting the durability of forging tools.

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Wear analysis of die inserts in the hot forging process of a forked type forging using reverse scanning techniques

Dworzak Ł., Hawryluk M., Ziemba J.

Advances in Science and Technology. Research Journal

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2017

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Vol. 11, no 4

225--238

EN

This article presents a wear analysis of die inserts used in the hot forging process of a forked forging (yoke), an element applied in steering systems of passenger vehicles. Studies involved the application of an original reverse scanning method intended for rapid and reliable wear analysis of forging tools (with complicated shape) affording easy assessment without the need to dismount tools from the forging unit. The developed method involves analysis of progressive wear of forging tools based on measurements (scanning) of forgings periodically collected from the process and constitutes a useful tool for measurement and testing. As the authors’ earlier works have demonstrated, the proposed new approach to analysis of tool wear with the application of reverse 3D scanning has proven successful in multiple instances in the case of axially symmetrical objects. The presented results of studies indicate that it is possible to utilize the expanded method to analyze the lifetime of forging tools, including tools with complex geometry. Application of the reverse scanning method allows for continuous and practical monitoring of the condition of forging tools over the course of the forging process and should have a positive impact on improving production output and reducing production costs.

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Analiza mechanizmów niszczących stemple stosowane w przemysłowym procesie kucia precyzyjnego na gorąco

Gronostajski Z., Hawryluk M., Kaszuba M., Marciniak M., Będza T., Zakrzewski T., Rogaliński G.

Prace Naukowe Politechniki Warszawskiej. Mechanika

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2013

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z. 253

107--112

PL

Praca dotyczy analizy trwałości stempla stosowanego w przemysłowym wielooperacyjnym procesie kucia obudowy przegubu. Szczegółowej analizie poddano jeden ze stempli używanych w czwartej operacji kucia, ze względu na najniższą średnią trwałość wynoszącą zaledwie 4000 odkuwek. Na skutek pracy narzędzia w ekstremalnych warunkach (wysokie cykliczne obciążenia mechaniczne oraz termiczne) najbardziej intensywne zniszczenia zachodzą w miejscu najdłuższego kontaktu (na promieniach zaokrągleń części roboczej stempla) z odkształconym materiałem. Na podstawie przeprowadzonych badań wykazano, że najbardziej niebezpiecznym zjawiskiem jest pękanie mechaniczne oraz zmęczenie cieplno-mechaniczne, które powoduje powstanie małych pęknięć, co w efekcie szybko prowadzi do powstania siatki pęknięć na całej powierzchni kontaktu narzędzia z kutym materiałem. Istotną rolę w niszczeniu narzędzi odgrywa także odkształcenie plastyczne oraz zużycie ścierne powstałe na wskutek wysokich temperatur na powierzchni kontaktu oraz intensywnego płynięcia materiału w obecności cząstek ściernych.

EN

The work concerns the analysis of the punch tool life used in the industrial multioperation forging process of CVJB housing. Authors performed detailed analyses of punch in the fourth forging operation regarding to its low life of less than 4000 forgings. As a result of tool extreme conditions (hight cyclic mechanical and thermal), the most intense damage occurs at the area of longest contact (the radii of rounding of the working the punch) with the deformed material. Extensive research (scanning surface, microhardness measurements, microscopic examinations, etc.) has shown that the most dangerous factor in the analyzed process is the mechanical cracking and the thermo-mechanical fatigue, which results in creation of the small cracks. They are changed into the grit on the entire surface of contacts between the tool and forged material. An important role of the tools destruction plays the plastic deformation and wear caused by hight temperatures and intense contact surface of the material flow in the precence of abrasive particles.