Brick – one of the most common materials traditionally used in the construction of buildings and structures. Technology brickwork gives architects and designers unlimited possibilities for the realization of creative ideas. Providing protection from external factors, having a high fire resistance and relatively low thermal conductivity, brick determines the high level of safety and comfort as residential and industrial buildings. By appointment brick construction and is divided into front (facing, front). Building bricks used for the internal rows of masonry for external or series, but with subsequent plaster. Facing bricks – a uniform color, has two smooth, flat surface of the face (so-called 'poke' and 'stretcher'). It is used for interior decoration is known that the brick is 'red' and 'white' – they differ composition. Red brick is mostly made of clay and is called 'ceramic' white – sand and lime.

A mixture of the latter was called 'silicate' and, hence, calcium silicate bricks. Silicate brick in shape, size and main purpose is no different from clay bricks. sand-lime brick of high quality must meet the following specifications: First, take into account the compressive strength. For sand-lime brick he is 15 – 20 MPa. In characterizing the strength of bricks marked with the letter 'M' indicating the degree of safety (M100, M125, M150, etc.).

When construction is necessary to consider this option, ie, for the construction of 2 – 3 storey cottage is suitable brick and M100 grade, but in the construction of bearing walls high-rise buildings make better use of the brand and M150 above. Second, the average density of the brick must be 1300 kg / cu.m. Third, the frost of silica brick is 15 and higher cycles to central Russia is best to choose a brick with a frost 35 – 50 cycles. Fourth, the maximum temperature of application should not exceed 550 C. Prices for sand-lime brick depend primarily on its technical characteristics, and hence on the quality. Therefore, buying a brick, always ask the seller license, because the brick quality will not only provide a good appearance of the building a few years, but its safety, strength. silicate brick masonry with good use of load-bearing walls and partitions of different, but strictly forbidden to use it in laying the foundations put stoves, fireplaces, pipes, sockets, etc. A definite plus silica brick in front of the ceramic is its high sound insulation performance that is important in the construction or interior walls mezhkvartirnyh. Techno-economic indicators sand-lime brick clay brick superior. Required to produce it in 2 times less fuel is 3 times less energy is 2.5 times less labor intensity of production, ultimately the cost of sand-lime brick is 25-35% less than clay. Silicate brick can be solid and hollow. Hollow brick and lighter due to this reduced pressure on the foundation. In addition, it has a lower thermal conductivity, so walls of a brick can be made thinner without compromising the thermal insulating characteristics. The use of brick with holes makes it possible to build in the usual way, with improved thermal properties, reduce labor costs, reduce the number of species of silica brick is very broad. If the mixture in the manufacture of silica bricks are added weatherproof, alkali-resistant pigments, then we color sand-lime brick. This is a silicate brick sandstone stained (range of colors can even include yellow, green and blue), a brick is usually used as a facing. Produced as a porous silicate brick and sandstone hollow, hollow brick / sandstone with a texture and so cleaved

For manual arc welding electrodes with a thick layer covering the chemical reactions between metal arc gases and slag flow at 2100-2300 C in a time of transition drops of molten metal through the electrode and cover arc gap. Further physical and chemical processes occur in the weld pool. The main chemical reaction during welding under flux occur only under a layer of molten flux in the welding bath. Consider key reaction in the weld zone of steel, as the most popular metal that is to be welded. Oxidation. In the area of welding, oxygen is the most harmful impurity, so as to oxidize the elements that are part of the metal seam, and degrades its quality, forming chemical compounds – oxides. Oxidation of the elements, usually occurs due to oxygen contained in the slag and gas welding zone.

Oxidation to a lesser extent may be due to oxygen surface base metal oxides (rust, scale). If you accidentally drop increasing the arc length of the electrode metal can be oxidized by oxygen in ambient air. The oxidation of initially formed ferrous oxide, which in the future under certain conditions (the ratio of oxygen and iron in the weld pool, temperature) can move into mixed oxide and iron oxide. During the welding process in the oxidation of iron main importance of iron oxide, as soon as it is able to dissolve in the liquid metal. When the oxygen content in the steel reaches 0,035%, from the solution begins to stand out excess oxygen to form iron oxide and located between the grains of the metal. Chemical reactions in the welding area are not up to the end and to a certain equilibrium between the reaction products and starting materials. The equilibrium state is characterized by simultaneous presence in the reaction zone as a free metal and its oxide at the designated ratios. The equilibrium state depends primarily on the concentration of the reactants in the reaction zone pressure and temperature.

The equilibrium state is determined by the equilibrium constant. Concentrations of the reactants determine only the direction of the reaction. The possibility of this reaction is due to chemical affinity of participating agents, in this case, the affinity for oxygen. In the presence of a base metal multiple items, they begin to oxidize all the time, but those elements whose affinity for oxygen at a given temperature greater than would be oxidized intensively and thoroughly. In the first place when welding steel oxidized iron, which is the main component. Other components are oxidized more rapidly than larger chemical affinity this component with oxygen. By reducing the degree of chemical affinity with oxygen, the components can be placed in the following order: aluminum, titanium, silicon, manganese, chromium, molybdenum, iron, nickel, copper. Carbon in increasing the temperature enhances the activity of oxygen and at 1700 C exceeds its activity titanium, and at 2100 C, aluminum. With decreasing in the reaction zone, the concentration of the components that have high affinity for oxygen, the rate of oxidation decreases. Appropriately increasing the rate of oxidation of other elements with lower affinity to oxygen, which begin to burn more intensely as long as their concentration is not drops to an equilibrium and will not end the oxidation. This process of successive increases the rate of oxidation of individual elements extending to as long as the concentration of all elements will not match equilibrium, after which the oxidation of the metal in the weld pool to an end.