Investigation of Metal Air-Cooling Process as An Element of Thermal Processing

<p>Background: Nowadays on metal tempering and annealing its air cooling (AC) is realized inside furnace with forced coolant delivery. Scientific tools lack for metal AC study and design is substantiated. The aim of this work is to investigate technological and design furnace parameters influence on metal AC duration, as well as disclosure of metal AC heat engineering regularities. Materials and method: For study mathematical model of metal AC is used. It bases on solving the differential non-stationary heat conductivity equation in one-dimensional form for cylindrical ingots and lining. Results: For three lining design types and different technological parameters operation acceleration possibility due to lining design change was studied. It is found that with ceramic fibers on walls and roof acceleration is 31-45% and with all lining made of ceramic fiber it is 44-52% as compared with fireclay brick lining. For a furnace with hearth of fireclay bricks and ceramic fiber on the walls and roof, convective component varies from 10 to 30%; for lining completely consisting of ceramic fibers it is 10 - 25%. When using fireclay brick lining parts their inner temperature is higher than for ceramic fiber up to 50 °C. Conclusions: Significant furnace lining materials type influence on metal AC intensity is proved. Heat removal mechanism on metal AC in furnace is disclosed, by establishing heat proportion directly removed from metal by convection. It is found that radiant heat transfer between metal and fireclay brick part of lining goes less intensively than with ceramic fiber part. </p>

Study on Thermal Operation and Design of Ring Furnace of the Pipe Rolling Plant

High productivity of rolling and pipe rolling mills, good quality of finished metal products is possible to provide in the presence of powerful heating furnaces, well heating the metal with minimal oxidation and decarburization. Such conditions are provided by ring furnaces which are widely used for heating the preparations at rolling of pipes, wheels and bands of the railway rolling stock. The purpose of the heat – receiving structure of the metal, providing a set of physical and working properties, or impart to these materials the ductility required for subsequent machining. The article deals with the design and thermal performance of the ring furnace operating at ChelPipe’s Pipe Rolling Plant No.2. The problems arising during the operation of the thermal unit are analyzed. The paper describes the calculation of heating of metal and heat balance of the ring furnace. In the course of the analysis of the results of design studies, the shortcomings of the existing heat recovery system are revealed and measures for the reconstruction of the furnace to reduce fuel consumption and increase productivity (replacement of the existing brick lining with fibrous, the use of regenerative burners, the use of non-water-cooled partitions, etc.) are proposed. The paper analyzes the design and thermal performance of the ring furnace for heating of pipe billets before rolling. It shows a heat balance of the ring heating furnace and provides measures for furnace reconstruction aimed at reduction in fuel consumption and increase in efficiency: replacement of the existing lining with fiber lining, use of regenerative burners, application of non-water cooled walls.

Evaluation of Chemical and Physico-Mechanical Properties of some Nigeria Natural Clays Samples for Foundry Applications

Studies have shown that Nigerian clays have not been fully utilized for foundry applications, either as refractories or even bonding clays, and are still being imported into the country. There is need to effectively exploit and adequately utilize the available natural resources to improve Nigeria economic activities, most especially during the present economic recession. Samples of clays were obtained from Auchi, Dada-Okelele (Ilorin), Kaba, Maraba-Rido, Mokwa and New-Bussa in Nigeria. The samples’ physico-mechanical properties were examined for its suitability for foundry/refractory applications. The results of the chemical analysis revealed that the samples belong to Alumino-Silicate refractories. The samples exhibited 35.3-96.2%, 17.1-28.7%, 1.72-2.34 g/cm3, 2.2-10.1%, 73-86 and >1300oC as values for percentage clay contents, apparent porosity, bulk density, permeability, linear shrinkage and refractoriness respectively. These values were within the standard range values of >35%, 22-30%, 17-2.4%, 2.0-10.1% and 25-90 required as percentage clay contents, apparent porosity, bulk density, permeability and linear shrinkage values respectively, for refractory clays/brick lining or alumina-silicates, kaolin and fireclays. Hence, the clays could suitably replace imported clays / ceramics in refractory applications, such as in production of earthen wares, chalk; as insulating refractories for casting and melting of low and medium temperature iron and steel. Appropriate utilization of these clays for local foundry applications will assist in addressing the problem of inadequate job, and over dependence on foreign goods.Keywords— Alumino-Silicate, Clay, Foundry, Moisture and Refractoriness