SU876790A1 - Method of cleaning ingots from ceramics - Google Patents

Description

t

The invention relates to the thermochemical cleaning of castings in alkali melts and can be used. in particular, for the removal of ceramic ceramics from complex aluminum casting.

A known method of chemical cleaning cast from ceramics by processing it in an alkali melt 1 ..

The disadvantage of this method is, with a significant specific consumption of alkali. In addition, when cleaning the aluminum casting, corrosion of the casting surface is observed; quality cleaning is possible only until 6-8 wt.% of ceramics are dissolved in the melt.

The closest to the proposed technical essence is the method of cleaning castings from ceramics by treating them in an alkali melt at 500-560s with periodic introduction into the melt of 1-2 wt.% Barium chloride 23 ...

The disadvantage of this method is that the cleaning of the casting is associated with the consumption of barium chloride and occurs at 500-560 ° C, which, for example, for aluminum casting is unacceptable due to its low corrosion resistance in alkali melts at elevated temperatures and etching

surface. The addition of barium chloride to the melt makes it possible to increase the operability of the melt; however, it also contributes to corrosion of aluminum casting during the cleaning process.

The purpose of the invention is to reduce the corrosion of castings in the process of cleaning them, reducing the consumption of materials and energy costs.

This goal is achieved by the fact that in the process of cleaning castings from ceramics, which include processing in an alkaline melt, during the processing of castings in the melt at 400–450 0 (as each 6–8 wt.% Of ceramics is added to the melt, the melt temperature is raised to 550-600 C for 5-20 minutes, followed by cooling the melt to the operating temperature.

Claims (2)

At the same time, cleaning in the range of temperatures 400-450 SG is not associated with significant corrosion of the casting surface. The specific operating temperature of the melt is chosen depending on the corrosion resistance of the 30-poured to be cleaned. For example, cleaning aluminum casting is recommended to be carried out at steel-nosing at 450s. At the operating temperature, it is advisable to dissolve no more than b% of ceramics in the melt, and at a temperature not more than 8% of the melt's weight, which is explained by a sharp decrease in the rate of interaction of ceramics with the melt during crushing above the specified limits. The latter leads to a prolongation of the cleaning time and an increase in the etching of the casting surface. Overheating of the melt to and above leads to the formation of sodium orthosilicate by the reaction of Na, 5iOj + lNaOH - Na4Si04 + H, () which after cooling the melt to the working temperature falls to the bottom of the bath as a compact precipitate, which reduces the melt viscosity and allows to continue cleaning in the same raz the melt of alkali. Overheating of the melt above is impractical due to its increased evaporation. The specific heating temperature is set depending on the saturation of the melt with silica: at 6 wt.% Ceramics in the melt, the superheat temperature is not lower than 550 ° C, at 8 wt.% Ceramics-BOO ° C . The exposure time, which ensures the completion of the reaction (.1), with an overheating temperature of 550 s is 20 min, at a temperature of 600 ° C - 5 m. Overheating of the melt, moreover, reduces the amount of water in the melt (more intense to complete). evaporation, which reduces, respectively, and the corrosion of purified casting. The method is carried out as follows: The casting to be cleaned is loaded into a caustic soda melt at a temperature of 4 00-4 50 ° C. In this case, the weight of one charge is chosen in such a way that simultaneously bring my melt with castings does not exceed 1-2% of the weight of the melt. Otherwise, due to the rapid chemical reaction accompanied by gas evolution, melt can be released from the crucibles. After holding the castings in the melt g for 20 min, they are removed from BHHily and sent for further technological operations (cooling, washing, etc.). Then in the melt process another charge is cast, and so on until the melt is saturated with ceramics in the amount of 6-8 wt.% Of the weight of the melt. After that, the melt overheated 550-600 ° C, incubated for 5-20 minutes and cooled to a working temperature of 400-450 ° C. Example 1. Aluminum casting from an alloy of AL9 is treated in a melt of caustic soda for 20 minutes. The amount of silica introduced into the melt with each batch of the castings to be cleaned is determined by calculation using the formula I., 00% where h is the amount of the ceramics introduced into the melt, wt%; K - the average amount of ceramics on the 1st kg pour, kg; P - the weight of the purified cast, kg; P2 - weight of the melt, kg. After the melt is saturated with 6 wt.% Ceramics, the cleaned castings are removed from the melt, the latter is heated to 550 ° C, held for 20 minutes and cooled to a working temperature of 400 ° C, after which the next batch is cast, etc. to dissolve in the melt about 24% by weight of ceramics. Next, the melt is purified from the precipitate, fresh alkali is added to the initial level and the purification is continued. Aluminum casting, cleaned by the proposed method, has a high-quality surface without traces of etching. Example 2. Steel casting from steel 45l with the remnants of the ceramic mold is treated in the molten caustic soda at 450 ° C for 20 minutes. The amount of silica introduced into the melt by each casting batch is determined analogously to example 1. After dissolving 8 wt.% Of ceramics in the melt, it is superheated to 600 ° C, kept for 5 minutes and cooled to a working temperature of 450 ° C, after which the next cleaning is carried out batch pouring, etc. Melt cleaning and refining of fresh alkali were performed as in Example 1 ,. after we melt approximately 24% by weight of ceramics. The consumption of caustic alkali during cleaning casting by the proposed method is reduced by 2-3 times without the use of any special additives. The implementation of the proposed method allows to obtain an annual economic effect in the amount of 100 thousand rubles. Claim method for cleaning castings from ceramics, including processing in an alkaline melt, characterized in that, in order to reduce corrosion of castings, material consumption and energy costs, in the process of processing castings in the melt at 400,450 ° C as it is introduced into the melt 5 8767906 every 6-8 wt.% ceramics period-Sources of information, the cast is extracted and temperature taken into account during the examination ru melt increase to BSE-BOO C1. USSR author's certificate within 5-20 minutes followed by OH-No. 358433, cl. C 23 Q 1/28, 1970, by waiting for the melt to the working temperature. 2. USSR Author's Certificate - literature., No. 663758, cl. C 23 G 1/28, 1977.