Browsing by Subject "quench"

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Access status: Open Access ,
Development of strength and electrical properties of Al-Si-Mg casting aluminum alloys with an Mg content of 1 wt%
(2016) Knych, Tadeusz Antoni; Wiecheć, Justyna; Uliasz, Piotr
Silumins (i.e., alloys where the main alloy additive is silicon) are the largest casting aluminum alloy group. Materials of this kind are characterized by high strength properties, high corrosion resistance, and low density, which make it possible to use them for construction purposes. A new group of developed properties typical for casting silumins are electrical and thermal conductivity. Thermal and electrical conductivity can be optimized by the suitable selection of chemical composition of the alloy, in the process of precipitation hardening, or by means of a combination of both. The present paper includes test results of the strength and electrical properties of AlSiMg casting aluminum alloys. The alloys that were subject to testing were AlSi5Mg1, AlSi7Mg1, and AlSi11Mg1. Heat treatment included homogenization at a temperature of 535°C over a time period of 8 h, quenched, and artificial aging. The strength tests involved a Brinell hardness measurement as well as an electrical properties test involving electrical conductivity measurement tests.
Access status: Open Access ,
Theoretical Possibilities of Controlling the Cooling Rate in the Heat Treatment of Cast Iron with Water Mist
(AGH University Press, 2024) Stręk, Piotr
The goal of the cooling procedure after austenitizing in the austempering heat treatment process applied to ausferritic ductile iron (ADI) castings is to rapidly reduce the temperature throughout the casting volume to the temperature range of the process window in which the proper metal matrix structure is formed. The lower limit of this range must be higher than the temperature at which the martensitic transformation starts. The upper limit is selected to eliminate the possibility of diffusion decomposition of austenite while holding castings at austempering temperature. Most often in heat treatment practice, salt baths are used for this purpose. Such a solution makes it possible to realize in one device both the procedure of cooling down to a given temperature and the procedure of isothermal heat treatment at this temperature. Unfortunately, the presence of molten salt in the process equipment has a very unfavorable impact on working conditions and ecology. The purpose of this research is to analyze the possibility of replacing the salt bath cooling procedure in the manufacturing process of ADI castings with a water mist spray cooling procedure on the surfaces of the heat-treated casting. If such cooling is effective, subsequent procedures of heat treatment operations can be carried out with traditional furnace equipment without the use of molten salt, which will clearly improve the environmental performance of the enterprise. The article, using analytical and numerical methods, analyzes the possibility of cooling objects made of cast iron with the help of a high-efficiency heat receiver such as water mist spraying. The limiting conditions for carrying out the process for the assumed cooling curve were considered. It was proposed to use a PID controller realizing the function of controlling the intensity of water mist spray, which corresponds to the intensity of the heat flux received from the heat-treated casting. The theoretical analysis carried out allows us to conclude that water mist cooling according to the assumed cooling curve is practically feasible.