SU604624A1 - Method of making castings in porous moulds - Google Patents

Description

The invention relates to the field of foundry, in particular, to a method for producing castings from ferrous and non-ferrous metals. A known method of making castings in metal (painted or lined) forms. By this method, the mold is used many times, and the possibility is achieved in increasing the crystallization rate of castings by using water-cooled chill molds. As a result, the fine-grained structure of the castings is obtained (the strength of the cast iron depends on the grain size: the finer the grain, the stronger the cast iron), and the surface of the castings has a lower roughness than those produced in sand forms 1J. The disadvantages of this method are gas-tightness, warping, high thermal conductivity and high proportion of metal molds, their limited use, especially for producing steel castings, imperfect supply of molds to the pouring site. The closest in technical essence is a method for producing castings on automatic lines, including assembling lined metal molds, transporting molds to the pouring site and pouring them in a fixed position, subsequent cooling of castings 2. High cost, bulkiness and difficulty in servicing such lines (machines ), various technological difficulties: the possibility of metal melt contact with hydraulic system oil, violation of the thermal conditions of the molds, and so on, as well as imperfection in the cool Chills and difficulties in managing the crystallization process of the melt are significant drawbacks of the method for producing castings in i-permanent metal forms and impede its development. In addition, when the chill molds are cooled with running water and thus, when the rate of crystallization of the metal poured into the mold is intensified, scum (welded salt layer), especially in thin sections, forms on the back walls of the chill mold; 150-200 C). Quite frequent violations in the complex system of water supply for cooling the molds and in the loss of tightness of the chill molds lead to the rejection of castings. The aim of the invention is to simplify the process of manufacturing castings by simplifying transportation and increasing the cooling intensity of casting molds with castings. The goal is achieved by transporting, pouring and cooling porous molds when placed in a flow of coolant, and the cooling rate of porous molds is 50-325 ° C / min with their porosity equal to 20-80 %

FIG. 1 shows a device for carrying out the proposed method, the position before pouring; in fig. 2 - the process of pouring metal molds; in fig. 3 - the process of cooling the mold with the casting (in this case the mold and the casting are immersed in the cooling liquid before the brewing cup).

The device contains a chute 1 with coolant 2, in which the mold 3 is placed. Half-permanent molds for producing castings are made of a lightweight (with a specific weight less than one) porous material having high heat resistance, for example, porous silicon carbide, whose strength is not lower than 60 kg / cm, gas permeability is not lower than 400 units, zero gas efficiency, heat resistance is not lower than 2000 ° C.

The material from which the mold is made is practically not wetted by water (for example, for molds made of porous silicon carbide, the wetting angle is 168-172 °). The speed of movement of the molds due to the flow of water to the pouring position may be 0.05-5.0 m / min.

Liquid at the movement of forms practically does not come into holes of forms. In this state (afloat), the molds approach the casting position and are poured with metal. Mold depth

As the working cavity of the mold is filled with metal, the cooling fluid (water) enters the pores of the mold to a height equal to the height of the submerged part of the mold in water. As

immersing the form in a liquid the heat removal rate increases. When the form is completely filled with metal, it is immersed in water to its full height (up to the pot). At the same time, the cooling rate of castings with

the materiality of the mold material increases from 20 to 80% from 50 to 325 ° C / min.

The method is carried out as follows. Forms are made of porous silicon carbide of different porosity, and

the proportion of such forms is smaller than one. The size of the forms is 1 mH1 mHO, 1 m. The forms are placed in an annular groove 1 filled with water. In this case, the forms 3 are immersed in the water by 0.8-1.0 mm, a turbine is installed in the channel with a speed of 600-1,800 rpm. During turbine operation, the flow of water is directed to the priming position. In this case, the flow rate of water, depending on the rotational speed of the turbine, varies from 3 to

21 m / min. When the molds approach the pouring position, they are fixed by a stopper (retractable rail) 4. With the help of the retractable rail, the mold is fixed to a moving stream of water. Then fill

a porous casting mold with 35 L steel. As the metal is filled, the mold is immersed in water. Depending on the size of the porosity, the immersion of the forms in the water when they are poured occurs at different heights.

(see tab. 1). into water depending on ot the porosity of the mold material and the weight of the metal being poured Table 1 Porosity,

The rate of cooling of castings with an increase in the porosity of the material (open pores, through) from 20 to 80% increases from 50 to 325 ° C / min (see tab. 2). After filling the molds with metal, the stopper is retracted, the mold with the casting, being on the plate, is cooled down, then transferred to the following areas: removing the molds from the channel, disassembling and removing the castings, preparing the molds for the next casting. The proposed method allows for the transportation and cooling of molds and molds. Table 2

Dependence of the cooling rate of castings on the value of the porosity of the mold material

afloat, free up thousands of tons of conveyors, rotary machines, tens of thousands of kilowatt-hours of electricity, increase productivity and improve the sanitary and hygienic conditions of foundries, produce castings with high accuracy, operational reliability and low cost.

Claims (2)

1. A method of producing castings in porous casting molds, including their manufacture, transporting, casting in a fixed position with molten metal and subsequent cooling of porous casting molds with filled metal, characterized in that, in order to simplify the process of producing castings, transportation, pouring and cooling of porous casting molds are carried out when placed in a coolant flow . 2. A method according to claim 1, characterized in that the cooling rate of the casting molds is 50-325 ° C / min with a porosity of 20-807 °. Sources of information taken into account in the examination 1.Dubinin N.P. Iron casting in metal molds. M., Mashgiz, 1958, p. 73. 2.Nikolaenko E. G. et al. Casting in lined metal molds. - “Foundry production, 1969, No. 1, s 1-3. i LrrrJ