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1
Content available Effect of Thermal Nodes Reduction in Wall Connections of the Charge-Handling Furnace Grates on Thermal Stresses
Bajwoluk Artur, Gutowski P.
Archives of Foundry Engineering
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2021
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Vol. 21, iss. 3
53--58
EN
The paper presents FEM approach for comparative analyses of wall connections applied in cast grates used for charge transport in furnaces for heat and thermal-chemical treatment. Nine variants of wall connection were compared in term of temperature differences arising during cooling process and stresses caused by the differences. The presented comparative methodology consists of two steps. In first, the calculations of heat flow during cooling in oil for analysed constructions were carried out. As a result the temperature distributions vs cooling time in cross-sections of analysed wall connections were determined. In the second step, based on heat flow analyses, calculations of stresses caused by the temperature gradient in the wall connections were performed. The conducted calculations were used to evaluate an impact of thermal nodes reduction on maximum temperature differences and to quantitative comparison of various base design of the cast grate wall connection in term of level of thermal stresses and their distribution during cooling process. The obtained results clearly show which solution of wall connection should be applied in cast grate used for charge transport in real constructions and which of them should be avoided because the risk of high thermal stresses forming during cooling process.
2
Content available Thermal Stresses in the Accessories of Heat Treatment Furnaces vs Cooling Kinetics
Bajwoluk A., Gutowski P.
Archives of Foundry Engineering
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2019
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iss. 3
88--93
EN
Depending on the course of the processes of heat treatment and thermo-chemical treatment, the technological equipment of heat treatment furnaces is exposed to different operating conditions, as the said processes differ among themselves in the temperature of annealing and atmosphere prevailing in the furnace chamber, in the duration of a single work cycle and in the type and temperature of the coolant. These differences affect the magnitude of stresses occurring in each cycle of the operation of furnace accessories, and thus play an important role in fatigue processes leading to the destruction of these accessories. The kinetics of temperature changes during each cooling process plays an important role in the formation of thermal stresses on the cross-section of the cooled parts. It depends on many factors, including the initial cooling temperature, the type and temperature of the cooling medium, or the dimensions and shape of the object. This article presents a numerical analysis of the effect of the initial temperature on the distribution of stresses on the cross-section of the grate ribs, generated in the first few seconds of the cooling process carried out in two cooling media, i.e. hardening oil and water. The analysis was carried out by the finite element method, based on the results of experimental testes of temperature changes in the rib during its cooling.
3
Content available Design Options to Decrease the Thermal Stresses in Cast Accessories for Heat and Chemical Treatment Furnaces
Bajwoluk A., Gutowski P.
Archives of Foundry Engineering
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2018
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Vol. 18, iss. 4
125--130
EN
By the very nature of their work, castings used in furnaces for heat treatment and thermo-chemical treatment are exposed to the effect of many unfavorable factors causing their deformation and cracking, significantly shortening the lifetime. The main source of damage are the micro-and macro-thermal stresses appearing in each cycle. As the cost of furnace instrumentation forms a significant part of the total furnace cost, in designing this type of tooling it is important to develop solutions that delay the damage formation process and thus extend the casting operation time. In this article, two structural modifications introduced to pallets castings to reduce thermal stresses arising at various stages of the cooling process are proposed. The essence of the first modification consists in making technological recesses in the wall connections, while the aim of the second one is to reduce the stiffness of the pallet by placing expanders in the external walls. Using the results of simulation analyses carried out by the finite element method, the impact of both proposed solutions on the level of thermal stresses was evaluated.
4
Content available The Effect of Cooling Agent on Stress and Deformation of Charge-loaded Cast Pallets
Bajwoluk A., Gutowski P.
Archives of Foundry Engineering
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2017
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Vol. 17, iss. 4
13--18
EN
The results of research on the effect of the type of cooling agent used during heat treatment and thermal-chemical treatment on the formation of temperature gradient and stress-deformation distribution in cast pallets, which are part of furnace accessories used in this treatment, are disclosed. During operation, pallets are exposed to the effect of the same conditions as the charge they are carrying. Cyclic thermal loads are the main cause of excessive deformations or cracks, which after some time of the cast pallet operation result in its withdrawal due to damage. One of the major causes of this damage are stresses formed under the effect of temperature gradient in the unevenly cooled pallet construction. Studies focused on the analysis of heat flow in a charge-loaded pallet, cooled by various cooling agents characterized by different heat transfer coefficients and temperature. Based on the obtained temperature distribution, the stress distribution and the resulting deformation were examined. The results enabled drawing relevant conclusions about the effect of cooling conditions on stresses formed in the direction of the largest temperature gradient.
5
Powłoki natryskiwane plazmowo na elementach urządzeń do fluidalnej obróbki cieplnej
Morel S., Jasiński J., Jasiński J., Jeziorski L.
Inżynieria Materiałowa
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2012
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Vol. 33, nr 5
456--459
PL
W pracy przedstawiono zastosowanie powłok wytwarzanych plazmowo na elementach urządzeń do fluidalnej obróbki cieplnej. Powłoki te można podzielić na trzy grupy w zależności od funkcji jakie mogą spełniać. Do pierwszej grupy należą powłoki pozwalające na modyfikację właściwości eksploatacyjnych, zwiększające m.in. trwałość mechaniczną elementów. Drugą grupę tworzą powłoki wpływające na właściwości cieplne i energetyczne, tj. zwiększenie wymiany ciepła i ograniczające straty energii. Trzecią grupę stanowią powłoki katalityczne stosowane w celu unieszkodliwienia niebezpiecznych składników zawartych w atmosferach roboczych stosowanych w urządzeniach cieplnych w procesach m.in. nawęglania i azotowania.
EN
Application of plasma sprayed coatings on fluidized bed heat treatment equipment elements is presented in this paper. Coatings can be divided into three groups according to their function. First group are the coatings which modify exploitation properties, second which influence on thermal and energy properties as heat transfer and energy losses elimination. Third group are the catalytic coatings used for limitation of harmful working atmosphere gases used in fluidized bed chemical-heat treatment as carburizing, nitrocarburizing.
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