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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.

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Structures for Heat Treatment Assembled from Cast Elements

Piekarski Bogdan, Drotlew Andrzej

Journal of Casting & Materials Engineering

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2020

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Vol. 4, no. 4

53--57

EN

Various types of technological equipment individually designed for operation in pit and elevator heat treatment furnaces are described in this article. A common characteristic of these structures is that they are composed of several or several dozen thin-walled elements of various shapes and sizes, gravity cast in sand moulds from creep-resistant alloys (austenitic Cr-Ni/Ni-Cr cast steel and cast nickel alloys). The design of the castings requires the development of a manufacturing technology that can effectively use the principle of the simultaneous solidification of all components. Properly designed equipment should have minimum weight, maximum strength, and maximum loading capacity combined with adequate durability and reliability. Two designs of the equipment for the heat treatment of steel parts were presented. Both designs, as well as their individual components, were described in detail and illustrated. The main task of the equipment is to form the charge in the furnace and transport this charge both inside and outside the furnace. The first design is the design of an equipment for the heat treatment of large ring-shaped parts. The second design is the design of an equipment, whose structure can be modified using various repeatable components. As a result of these modifications, different variants of the equipment are obtained, allowing for the heat treatment of five different types of the shafts characterized by different shapes and sizes. The study is of an application nature. It is addressed to engineering and technical staff dealing with both the design and operation of heat treatment furnaces.

3

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.

4

Cast functional accessories for heat treatment furnaces

Piekarski B., Drotlew A.

Archives of Foundry Engineering

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2010

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Vol. 10, iss. 4

183--190

EN

The study gives examples of the cast functional accessories operating in furnaces for the heat treatment of metals and alloys. The described design solutions of castings and their respective assemblies are used for charge preparation and handling. They were put in systematic order depending on furnace design and the technological purpose of heat treatment. Basic grades of austenitic cast steel, used for castings of this type, were enumerated, and examples of general guidelines formulated for their use were stated. The functional accessories described in this study were designed and made by the Foundry Research Laboratory of West Pomeranian University of Technology.