except.
(3) Pouring temperature The pores between sand grains are increased by sintering or melting under the heat of metal, thereby increasing the penetration depth of molten metal. When the pouring temperature is low, because the sand is not easy to sinter or melt, fine sand molding is used, and the penetration depth of the metal liquid is small, so that it is not easy to stick sand. When the pouring temperature is relatively small, the fine sand is easily sintered or melted, and the pores between the sand particles increase in size and the penetration depth of the molten metal increases, and the sticky sand is easily generated. When the pouring temperature is too high, the coarse sand can also be sintered, and the penetration depth of the molten metal is more necessary than the post-sintering amount and the control of the pouring temperature.
4 The mineral composition and chemical composition of the sand sand directly affect the refractoriness and chemical stability of the sand, thereby affecting the degree of stickiness and surface roughness of the casting. The impurities in the sand are mainly alkaline oxide sulphides and iron oxides. Alkaline oxides can form susceptibility materials with the main components of quartz sand. This kind of material will melt and stick to other sand grains to form sintered and lead to viscous sand. Sulfide is more harmful. Sulfide will precipitate sulfur gas at high temperature. If gas comes into contact with molten steel, it will produce low melting point 3,3 and strong bonding strength, so it is easy to form severe sticky sand; iron oxides will reduce the refractoriness of sand and make sand easy to sinter. Inspection, the mineral composition of the original sand, requires special equipment and complex techniques, the site is difficult to do, but the oxide of iron is easily judged, when the content is high, the sand is yellow or reddish, this kind of sand is easy to form sintering and Sticky sand.
5 Water glass Water glass is used as molding material mainly as binder for molding sand. The main components of casting water glass are sodium silicate and water. Sodium silicate is a mixture of SiO2 and Na20 in different proportions and the ratio of 0 to 0 is called the modulus of the module is the main parameters of water glass, and the other main parameter is the specific gravity. Due to the lower production cost of low-modulus water glass, the general modulus of water glass in actual production is large, and the large modulus results in fast hardening of the sand, and the strength after hardening is reduced, resulting in that the cavity surface sand easily fall off, forming voids, making metal Infiltration of liquid into the formation of sticky sand, while the modulus is large, the sand easily sticks to the top of the model, affecting the surface finish of the cavity after the mold. When the curing speed is high, the formed gel skeleton is destroyed in the modeling, so it will also affect the strength of the sand, and ultimately affect the casting surface quality, resulting in flash burr. The effect of the large modulus of the water glass is more prominent in the summer, sometimes reaching a difficult or impossible shape. In the winter, this phenomenon has been greatly improved. Therefore, the summer water glass glass modulus control captures the main contradiction, water glass sand is easy to stick to the model can be used in the sand to add heavy oil or spray kerosene on the model and other methods solve.
Although these factors work together, improving or resolving each of them can help to improve the quality of the casting surface. Of course, the overall improvement will be even better. , Pingdingshan, Henan Province, 5 engineer, graduated from the Zhengzhou Institute of Technology in 1983, the Provincial Foundry Association haircut papers multiple, incumbent Pingdingshan coal mine machinery factory deputy chief, division. 03754978758.
Analysis of the factors affecting the surface quality of steel castings Liu Jianfu's new type of flameproof high voltage vacuum power distribution device Yanzhou Mining Group Nantun Coal Mine Dongfang Electromechanical Co., Ltd. adopts the design recommended by the former Ministry of Coal Industry and draws on Japanese manufacturing technology to produce Type 8019160 Flameproof high voltage vacuum power distribution device for mining.
Its main features are as follows: Due to adopting the structure of the live bolt bolt-on type door opening structure, it overcomes the instability of the explosion-proof parameters of the quick-opening door products in the past and achieves double break point isolation, providing a safety guarantee for the overhaul of the outfeed line. When the movement emerges, the trolley is pulled out of the box, which can facilitate maintenance or replace the spare movement, saving the time of inspection and repair. This device also has a reliable safety interlock, and the door can be opened only after the isolation pin is opened in place; after the door is opened, the isolation pin cannot be closed; after the isolation pin is closed in place, the vacuum circuit breaker can be closed; the isolation pin cannot be With load switching. Li Jianfeng feeds
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