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The influence of hardening medium in the vacuum carburizing process on the distortion of machine elements used in the automotive industry

Pawęta S., Pietrasik R.

Journal of Achievements in Materials and Manufacturing Engineering

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2019

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Vol. 94, nr 1-2

32--40

EN

Purpose: As part of this study, the influence of the hardening medium on distortions of FineCarb® carburized rollers used in the automotive industry as elements of fuel pumps has been examined. The analysis was carried out for the process of quenching in gas at different pressure of cooling gas and quenching in oil at variable delay time of oil mixers. Design/methodology/approach: The research was carried out on real elements used in the automotive industry as elements of fuel pumps. FineCarb® vacuum carburizing technology was used in order to obtain optimal parameters of the surface layers. During quenching a variable related to the parameters of the quenching medium was introduced. For quenching in gas it was the pressure at which nitrogen was introduced into the cooling chamber, while for quenching in oil it was the time of mixers delay. The sample batch was laid out in accordance with the PPAP (Production Part Approval Process) requirements for the automotive industry. Microhardness and radial runout measurements were carried out on the samples and subjected to statistical analysis. Findings: The analysis of each hardening processes has showed that depending on the cooling medium used, different distortion values are obtained. The distortion value is significantly influenced by the parameters of the hardening process - gas pressure/oil mixers delay. With the proposed quenching parameters, there is no relationship between the location of the sample in the furnace chamber and the distortion value. The smallest hardening distortions were obtained as a result of the hardening process in gas at a gas pressure of 3 bar. Hardening in gas was characterized by the smallest scatter values of obtained results of radial runout. Research limitations/implications: Basing on the studies and analyses carried out in this work, it can be concluded that the introduction of gas quenching technology instead of oil quenching technology is justified qualitatively and economically alike. Hardening in gas was also characterized by the smallest scatter values of obtained results of radial runout. This is an extremely important technological and economic aspect, due to the cost of grinding processing. Practical implications: The automotive and aviation industries are putting ever greater demands on the quality of manufactured components while reducing costs. It requires optimization of technological processes from co-operators. In the case of hardening plants, the most important aspect is obtaining repeatable, precisely planned parameters of the carburized layer, as well as minimizing the negative phenomena that cause dimensional changes after hardening of elements. The tests allowed to determine the most effective hardening conditions in terms of obtained distortions and costs of eliminating distortions. However, the selection of the optimal parameters depends on whether the core hardness requirements are also determined. Originality/value: The conducted tests allowed to determine the most effective hardening conditions in terms of obtained distortions, costs of levelling distortions and a complete technological process for the automotive industry.

2

Stachurski W., Zgórniak P., Sawicki J., Przybysz M.

Advances in Science and Technology. Research Journal

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2017

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Vol. 11, no 1

237--245

EN

The purpose of modern surface hardening technology is obtaining reproducible, precisely planned parameters of the carburized layer, minimizing the negative phenomena that result in dimensional changes after hardening and making it possible to determine the nature and magnitude of these changes. This concerns mainly the concept of single-piece flow in heat treatment applied for the purposes of mass production, employing a special autonomous 4D Quenching chamber for high pressure gas quenching (HPGQ). The main components of the 4D Quenching chamber include a system of cooling nozzles surrounding the processed item and providing a uniform inflow of cooling gas from all directions (3D) and a table rotating together with the item processed, contributing to uniform cooling (4D). Within the framework of this paper there was studied the impact of gear wheel quenching in a 4D Quenching chamber using nitrogen at pressure of 6 and 10 bar on changes in geometry. Geometric measurements of facewidth of gear, hole diameter and outside diameter were performed before and after carburization and quenching. The results obtained allowed us to determine the impact of quenching pressure inside a 4D Quenching chamber on dimensional changes in gear wheels analyzed. The thermo-chemical treatment resulted in a decrease in outside diameters and hole diameters measured and an increase in facewidth of gears.

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Distortion of 16MnCr5 steel parts during low-pressure carburizing

Dybowski K., Niewiedzielski R.

Advances in Science and Technology. Research Journal

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2017

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Vol. 11, no 1

201--207

EN

One of the many advantages of low pressure carburizing (LPC) is that it can be combined with high-pressure gas quenching. This makes it possible to achieve workpieces with pure metallic surfaces, less distortion hardening, and, above all, it allows a more reliable and repeatable treatment than conventional oil quenching. This article presents a study of the distortion rate of workpieces carburized at low pressure then quenched in nitrogen at 1.4 MPa. By comparing the distortion which takes place during the carburizing stage only and the carburizing combined with post-carburizing heat treatment it will be possible to assess the distortion rate and its causes at the different stages of the heat treatment process.

4

Single-chamber HPGQ vacuum furnace with quenching efficiency comparable to oil

Korecki M., Olejnik J., Szczerba Z., Bazel M.

Inżynieria Materiałowa

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2010

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Vol. 31, nr 4

1038-1041

EN

This article discusses the new generation, single-chamber vacuum furnace with a high-pressure gas-quenching system (HPGQ) able to quench with an efficiency better than that achieved in furnaces with a separate gas-quenching chamber (cold chamber) and comparable to the efficiency of oil systems. The performance of the furnace cooling system as it relates to the thermophysical properties of quenching gas at ambient and process temperatures is presented and discussed. Finally, the efficiency and technological effect of quenching in gas is compared with results obtained in typical oil-quench systems.

PL

Artykuł przedstawia nowej generacji, jednokomorowy piec próżniowy wyposażony w gazowy system chłodzenia pod wysokim ciśnieniem (HPGQ), umożliwiający hartowanie stali ze skutecznością większą niż w piecach z wydzieloną komorą chłodzenia gazowego (zimną komorą), a porównywalną do systemów olejowych. Przedstawiony i omówiony jest wpływ cieplno- fizycznych własności gazu na efektywność systemu chłodzenia. Ostatecznie porównano skuteczność i wynik technologiczny hartowania otrzymany w gazie i w typowych systemach chłodzenia w oleju.

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Odkształcenia kół zębatych w procesie nawęglania niskociśnieniowego z hartowaniem w gazie pod wysokim ciśnieniem

Dybowski K., Kula P., Sawicki J., Pietrasik R.

Inżynieria Materiałowa

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2010

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Vol. 31, nr 4

942-945

PL

Nawęglanie próżniowe oprócz wielu zalet daje również możliwość połączenia tej obróbki z hartowaniem w gazie pod wysokim ciśnieniem. W efekcie uzyskuje się detale o czystej metalicznej powierzchni, mniejszych, a przede wszystkim bardziej powtarzalnych odkształceniach hartowniczych w porównaniu z nawęglaniem konwencjonalnym z hartowaniem w oleju. W artykule przedstawiono badania wielkości odkształceń kół zębatych nawęglanych próżniowo i hartowanych w azocie pod ciśnieniem 1,2 MPa w zależności od ich rozmieszczenia w komorze obróbczej jednokomorowego pieca próżniowego do nawęglania. Zmierzono bicie promieniowe uzębienia i średnicy osadczej kół przed i po obróbce.

EN

Vacuum carburizing offers numerous advantages and also allows combining this treatment with quenching in a gas under high pressure. As the results details with the pure metallic surfaces, the smaller and, above all, more repeatable distortion hardening as compared to the conventional carburizing quenching in oil are obtained. The article presents the studies about the volume distortion of vacuum carburizing and quenched in nitrogen at a pressure of 1.2 MPa gears, depending on their placement in the one - chamber vacuum furnace for carburizing during the process.

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Symulacja komputerowa wyznaczania profilu twardości w warstwie wierzchniej po nawęgleniu próżniowym i chłodzeniu w gazach

Atraszkiewicz R., Kula P., Górecki M.

Inżynieria Materiałowa

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2006

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Vol. 27, nr 5

858-861

PL

W pracy przedstawiono wyniki badań grubości warstw nawęglonych po hartowaniu gazowym oparte na rzeczywistych procesach przeprowadzonych na stanowisku do obróbek cieplno-chemicznych oraz symulacji wyznaczającej profile twardości warstw po hartowaniu gazowym. Aplikacja komputerowa wyposażona została w opcję definicji komory roboczej urządzenia realizującego obróbkę cieplno-chemiczną i obrabiany wsad, co w dużym stopniu przyczyniło się do zmniejszenia czasu optymalizacji parametrów całego procesu. Ponadto prezentowana aplikacja stanowić będzie integralną część opracowanego systemu eksperckiego SimVaC™ przeznaczonego do doboru prawidłowej, dla założonych warunków eksploatacyjnych, budowy warstwy wierzchniej oraz optymalnego przebiegu procesu technologicznego.

EN

The results of investigation of carburized layers depth after gas quenching, based on real processes made at heat-treatment device and determining the hardness profile of hardened layers model simulation, are presented in the paper. Computer simulation has been equipped with furnace chamber definition option and charge pieces definition procedure leading to decrease of calculation and optimizing time. Moreover, the application is the essential part of expert system SimVaC™ for optimal process course selection.

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Analiza twardości granicznej warstw nawęglanych hartowanych w gazach pod wysokim cisnieniem

Kula P., Atraszkiewicz R.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Mechanika

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2005

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Z. 82

161-168

PL

W artykule przedstawiono omówienie metody określania twardości granicznej warstw nawęglonych po hartowaniu w gazach pod wysokim ciśnieniem, będącej integralną częścią opracowanego w Instytucie Inżynierii Materiałowej Politechniki Łódzkiej systemu FineCarb. Istotą problemu było opisanie modelu matematycznego zmian temperatury w badanym detalu, stworzenie baz materiałowych dla wytypowanych gatunków stali zawierających informacje odnośnie struktury i właściwości, wyznaczenie zależności wielkości wsadu, wielkości komory chłodzenia i ciśnienia gazu od szybkości chłodzenia. Te zależności w połączeniu z wymaganiami odnośnie właściwości warstwy wierzchniej są danymi wejściowymi do symulacji procesu nawęglania próżniowego spełniającego wymagania postawione przez użytkownika systemu.

EN

The method of limiting hardness of carburized and quenched layers analysis has been investigated in the paper. This method is integral part of FineCarb system created at Material Science Institute at Technical University of Lodz. The main goal of investigations and researches was to define a mathematical model of temperature distribution and cooling rate in heat-treated part, create materials database and dependence between charge size, cooling ability of quenching chamber and properties of quenching gases. This assumption leads to perform conditions about surface layer required by users.