SU927412A1 - Method of applying coating on ingot mould working surface - Google Patents

Description

(5) METHOD OF APPLYING COATING ON THE WORKING SURFACE

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The invention relates to metallurgy, in particular to methods of coating the surface of molds.

There is a known method of coating the inner surface of the layer (which consists in the fact that a variable air pressure is applied in the dispenser and that the side air jet 11 is directed at the sprayed torch.

The disadvantage of the invention is that when it is used, the front end of the mold is not painted and the coating does not evenly lie along the length of the cylindrical part. Obtaining a thin layer of the coating at certain places of the inner cylindrical part of the mold and on its end walls leads to the appearance of external chill and structurally free cementite along the cross section of the walls of the castings of the sleeves of tractor and automobile engines. The presence of cementite leads to scuffing and engine failure.

The purpose of the invention is to develop a method for coating a working surface of a mold, which ensures uniform coating of the cylindrical and end parts of the mold and accelerates the drying of the coating.

The goal is achieved by the fact that in the method of coating on the working surface of the mold, including spraying the coating under

10 by compressed air from the sprayer, an air flow in the form of a cone, with a base equal to the diameter of the opposite end of the mold, is directed towards the flow of the coating,

IS, at the time of the return stroke of the sprayer, the pressure and air flow are uniformly increased until the sprayer leaves the mold, reaching a pressure equal to

20 air pressure in the sprayer and flow rate 1.5-2.0 times the air flow rate in the sprayer and the flow rate until the sprayer leaves the setting 3, so that the pressure reaches the air pressure at the exit of the sprayer, and the air flow exceeds the flow rate air flow in the sprayer 1,352, 0 times. The direction of the air jet to the flow of the sprayed paint contributes to an increase in the dispersibility of the paint and allows a uniform layer of coating on the inner surface of the mold. Orientation of oncoming air flow along a guide close to a cone forming With a base corresponding to the opposite end of the mold, ensures that the coating penetrates the inner surface of the front cover, which is practically impossible when using other methods. Supply of oncoming air flow into the mold will ensure uniform application coating on the back end of the mold during the forward stroke of the sprayer and significantly improves the application of the coating on the inside of the front cover. Controlling the pressure and flow rate of air on the organization of a counter flow during the reverse movement of the sprayer allows for a more uniform coating of the cylindrical part of the mold and ensures that the layer has an optimal thickness on the front cover. A gradual increase in pressure during the return stroke of the sprayer improves the uniformity of the coating thickness over the entire inner surface of the mold and the front ring. In addition, increasing the pressure of the oncoming air accelerates the removal of vapors from the mold and increases the drying speed of the coating layer on the inner surface of the mold. FIG. 1 and 2 are diagrams illustrating the operation of the method. As can be seen from FIG. 1 (ae) with ave. In the course of the mold, a sprayer comes in, there is no counter-flow of air, and the sprayer provides coating on most of the cylindrical part of the mold and on its back end wall. FIG. 1 (ae) shows the spray cones of a coating when used in an air diffuser with a pressure of 6 atm. When the spray gun reaches the limit position (Fig. 1e), it 4 stops and begins to move in the opposite direction of Fig. 2g) and at this moment air begins to be supplied to the nozzle located in the end part of the mold on the same axis as the sprayer. An increase in pressure and an increase in air flow in this nozzle occurs linearly and at the time the sprayer leaves the mold reaches the air pressure in the coating sprayer (atm), and the air flow rate exceeds the air consumption in the sprayer 1.35-2.0 times. FIG. Figure 2 (F) shows the change in the direction of flow of the coating from the sprayer under the action of a counter-flow of air from the end nozzle. From the presented data, it can be seen that the greater the pressure and air flow in the nozzle, the more the main flow of the sprayed coating deviates (shown by the shaded area). At the moment the sprayer leaves the mold, when the air pressure in the nozzle reaches the air pressure in the sprayer and the air flow reaches 1.5-2.0 times the air flow in the sprayer 1.35-2.0 times, the main flow of the sprayed coating becomes such that coatings on the inner face of the front ring. Studies show that if, at the moment the spray gun comes out of the mold, the pressure of the air supplied to the nozzle is less than the air pressure in the spray gun and the air flow through the nozzle is greater than the air flow through the spray gun less than 1.35 times, then part of the front ring is covered with a coating not completely and in a thin layer. At the same time, if the considered flow rate is more than 2.0 times the air flow rate in the sprayer, then the coating begins to be intensively carried out into the front ring opening and this leads to an increase in coating consumption and poor sanitary and hygienic conditions in the workshop. Example. The proposed method of coating is used for casting SMD-1 sleeves on a single-station installation in the foundry of the Kiev plant. Lepse. A cast iron mold is used as the mold. The coating composition is as follows.

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Mac.S ;: filter powder 10-12; refractory clay 8.5-10.5; Dextrin 2-3 cryptocrystalline graphite 1-1.5 and water the rest. The speed of rotation of the mold is 1 BWr / min. The flow rate of the liquid coating is. 0.8-0.52 l, which provides the thickness of the dry coating on the surface of the mold 0.45-0.6 MM. The temperature of the mold during coating is 550-580 K.

For casting, cast iron of the following chemical composition is used, mas: carbon 3,2; silicon 1.86; manganese 0.83; chromium 0.28; nickel phosphorus 0.11; antimony 0.18; sulfur 0.04 and iron else. Cast iron is melted in a MGP-102 induction furnace. The cast iron temperature during casting is in the range of 1670-1705 K.

The studies performed show that when coating is applied, using only one sprayer, retracting into the mold, the thickness of the coating on the cylindrical part of the mold at its back end is 0.65-0.8 mm, on the back end wall and the front part of the mold 0 , 4-0,5 mm, and on the inside of the front ring 0.1-0.2 mm. The study of the microstructure of the molded sleeves shows that if a part of the liner adjacent to the front ring is found to have structurally free cementite, then in the cylindrical part of the casting adjacent to the back end of the mold, ferrite is observed.

Using the proposed method of coating, a uniform layer of coating 0, 55 mm thick was obtained on the entire surface of the mold and fine perlite was obtained in the casting microstructure in all parts of the casting.

If in the first case, the hardness of cast iron at various places of the liner is within 2170-3400 mPa HB), then in the second case it is within 2400-2470 mPa.

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Studies show that the proposed method allows to reduce the time of application and drying of the coating. This makes it possible to increase the productivity in casting the liner by 3%, 0%. Improving the microstructure of the cast iron of the liner reduces the scrap by 10-15. and improve machining productivity. by 7-12%.

A preliminary calculation of the expected economic efficiency from the implementation of the proposed method shows that by increasing the productivity in casting liners by 7.0, reducing the scrap by 10-15 and increasing the productivity in machining castings, the savings will be 26.3-27.1 rubles. on 1 ton of cartridges

Claims (2)

1. The method of coating the working surface of the mold, including spraying the coating under the pressure of compressed air from the sprayer, different jeM that, in order to ensure uniform coating on the cylindrical and end parts of the mold and accelerating the drying of the coating, directing the air stream in the form of a cone with a base equal to the diameter of the opposite end of the mold towards the sprayed coating. 2. Method pop-1, which is also distinguished by the fact that a counter-air flow is fed into the mold during the return stroke of the sprayer, and at the time of the return stroke of the sprayer, pressure and air flow are uniformly increased until the sprayer leaves the mold, reaching a pressure equal to air pressure in the sprayer, and a flow rate of 1.52, 0 times the flow rate of air in the sprayer. Sources of information taken into account in the examination 1. USSR author's certificate ff 428785, cl. B 22 D 13/10, 1968. PI-3-bati } -foru LR