Processes at the inetrface molten metal-sand mold

The processes that take place at the liquid metal-sand mold interface during the casting and crystallization of metal were studied in this paper. The mold was made using the CO2 – method, with the addition of active components, such as: MgO, TiO2, AlK(SO4)2 and Na2SO4. At the liquid steel pouring temperature, these active components undergo decomposition in the mold, caused by heat release during pouring, crystallization and cooling of castings. Silicates, which have an important influence on casting surface quality, are formed as a result of the interaction between the mould material and liquid steel

Tempering/ageing in region 50 – 600 °C of quenched and cold deformed 585 GOLD alloy for jewelry production

Numerous gold alloys posses the ability for thermal hardening, and this property is attractive for improving jewels strength, because the most noble alloys are weak. The thermal treating below the recrystallization temperature, is kind of tempering but also age-hardening. In this paper is made an attempt for studying the possibility for thermal hardening of 585 golden alloy. The goal is to increase the mechanical properties. Those demands could be reached by metallurgical controlling of phase transformations аnd proper thermal treating. Here is studied behavior of quenched and cold deformed gold alloy 585 after tempering/ageing in temperature region 50 - 600 °C, in intervals of 50 °C. The highest hardness values are obtained at temperatures about 200 °C for both initial states

Sustainable management of drinking water production plant pollutants

During the last two centuries, the origin of pollution substances that are jeopardizing environmental sustainability by devastating its structural elements, are a consequence of rapid techno-economic development. It is the unconditional accountability of the human population to recover the biosphere, through remediation and diminution of the existing, as well as prevention of future extermination of natural resources. One of the ultimate prerequisites for survival of all living beings is water. Anthropogenicly, it means it means providing enough drinking water in the same quantities for us, as well as for the future generations, applicable for all other natural resources. This essay puts the accent on the crucial aspect of water sustainability: sludge managing, from the water production plant, specifically drinking water, from the aspect of influence on structure, quantity, optional recycling and the most efficient disposal

Contribution to study of processes on the steel cast-sand mould contact surface during casting

The testings involved in this paper were part of a comprehensive research project conducted to find out what complex processes were taking place at metal-mould contact surface. These investigations are of particular importance for metal casting from relatively high melting temperature, such as that of steel (approximately 1600 °C). Steel castings, in regard to their high manufactured temperature and other specifications in pouring, need a mould mixture of such good quality. The mould mixture, used for casting steel class DIN G-X 120 Mn 12, was based on the silica sand, and with water-glass as a binder and AlK(SO4)2 as an active component. This active component is, at pouring temperature of liquid steel, decomposed in the mould by thermal influence during pouring, crystallization and cooling the casting. In decomposition process of the active component, the gaseous products appear and the water-stream is generated from chemically bonded water. These processes are influencing the molten metal oxidation. The penetrated molten metal into the mould surface is oxidized, too. At the high melting temperature and in the presence of gaseous products, the silicates were formed in the contact zone between metal and sand mould mixture. The objective of these tests was to find out to what extent the composition of the mould mixture affects the formation process, shape, type and composition of the silicates

The investigation of applicability of the Hollomon-Jaffe equation on tempering the HSLA steel

High strength low-alloyed (HSLA) Cr-Mn-Si steels belong to a group of steels that can reach their full mechanical properties after quenching and tempering. Those properties depend both on the temperature and time of tempering. Knowing the tempering parameters, it is possible to reach the desired properties of the treated steel. Some results on investigating the Hollomon-Jaffe equation (in parametric form) application for tempering of HSLA steel, are shown in this paper. The experiments were performed in real production conditions, using a standard material. The quenching was performed at 870 C, the heating period was always 30 min, with subsequent cooling into the oil bath. The tempering was carried out in temperature range from 480 to 680 C, while tempering time varied from 15 min to 24 h. The degree of tempering is referred through the hardness values changing. The experimental results have shown a pretty well agreement to tempering parameters, included in Hollomon- -Jaffe equation, for this kind of HSLA steel

JIT maintenance improves the productivity and energy efficiency of the system

Maintenance planning in order to ensure the smooth functioning of the system, optimal interaction of system with the environment, and timely responses to the set requirements is one of the most important internal resources of the organization. Just-In-Time Maintenance enables rarely downtime and lower maintenance costs throughout the life cycle of the system, and dramatically increases the productivity and energy efficiency of the entire system. By adopting of the Just-In-Time Maintenance philosophy, minimum of objective function of energy or production system, as well as of production of services system, is achieved

Quenched zones and material structures at gears teeth

Gears are used in most types of machinery, including the automotive industry as a wide known application. Different types of gears are specified through many (inter)national standards, mainly their geometry, design specifications or requirements while the (micro) structures of gear's teeth are less known. In diagnostics of damage or rupture, when it is happened, the microstructure undergoes to investigation but this is usually too late. From that reason the (micro)structure and hardness of gear tooth should be known in advance and here is defined. In manufacturing of a gear many methods are available rather by cutting (milling, hobbing, shaving or grinding) than forging. Those cutting methods have no great influence on the structure. If the grinding was not performed correctly than the hardened surface may be softened, even with cracks. The main influences on the structure to be obtained lie in a kind of production techniques such as: casting, forging, rolling and finely by a kind of chemical heat-treating of gear teeth surface. Here are presented typical zones and microstructures realized through the chemical heat-treating of teeth, and those should be known, especially for providing an incoming control of a gear in industrial conditions. Those data are of a crucial importance for a gear life