SU971572A1 - Method for treating solidifying alloy with ultrasonic oscillations - Google Patents

Description

The method relates to the field of foundry and metallurgy, in particular, to methods for increasing the density of casting and ingots using ultrasound.

The solidification and crystallization of the casting is accompanied by a decrease in its volume and filtration of the melt through the capillaries between the growing crystals. In places where the melt filtration stops, pores appear. In this way, a very common defect of castings is formed. Porosity, the intensification of the filtration feed of the castings reduces their porosity and increases the density.

. When processing melts by ultrasound, waves exert additional pressure on the liquid metal, helping to filter it between crystals.

A known method of treating molten metal with ultrasound is that the melt is treated with ultrasound at a temperature higher than JJKvidyca.

However, for this method, the nature of: high energy intensity and egsha effectiveness of the effect on the compaction of castings, due to the fact that the processing of the melt is performed with a sound before the start of the npoi eccoB I shrinkage and filtration feed of the casting.

Closest to the invention in its technical essence and achieved, my goal is a method for the ultrasonic treatment of a crystallizing melt by introducing a radiator into its upper part 2.

The essence of the method is

10 that in the upper part of the mold between the molten melt and the emitter, an acoustic contact is established by immersion and the treatment of the melt with ultrasonic is started. The sonication is performed before the ingot is completely hardened. In this case, a necessary condition is the constant contact of the radiator with the liquid phase and, therefore, the absence of contact with the solid phase of the casting or ingot until its main mass is completely solidified.

The main disadvantages of the known methods are their high energy capacity and low effect on improving the filtration supply of castings; for a small amount of ultrasonic pressure, which causes an insufficient increase in density

30 castings. The purpose of the invention is to improve the quality of castings, in particular, their density of intensification of filtration feeds. . The goal is achieved by the fact that in the method of processing a crystallizing alloy by ultrasound, including the effect on the crystallizing melt in the direction of gravity by ultrasonic oscillations, the frequency of which is adjusted and maintained during crystallization in resonance with the frequency of the natural oscillations of the casting, the contact between the casting and the radiator is established after forming in the casting at least 384 .3% of the solid phase with the intensity of ultrasonic vibrations of 0.7–7.0 W / s and then increasing the intensity by 1–9 W / cm per s 9.5-10.5% increase in the amount of hard phase. The principal difference of this method of increasing the density of castings using ultrasound from the known method is that the density of castings does not increase due to the emergence of new centers of crystallization and grain refinement, but due to the intensification of filtration feeding of castings through the use of a new phenomenon - the ultrasonic capillary effect, which excited by the proposed method. The magnitude of the overpressure acting on the melt is tens and hundreds times the usual ultrasonic pressure. This contributes to a sharp increase in the rate of melt filtration between growing crystals, improving the feeding of the casting and increasing its density. The beginning of the ultrasonic treatment of castings coincides with the beginning of the process of their filtration feed, corresponding, depending on the type of melt and the conditions of its cooling, to the formation of 35 to 45% of the solid phase. During this period of melt flow between the crystals, it does not experience any particular difficulties due to the high porosity and. small hydraulic resistance of the casting skeleton. Therefore, in order to intensify the filtration, rather small pressures created by the ultrasound-induced fluctuations of W / cm. During the crystallization process, due to an increase in the amount of solid phase, 1 irregularities on the surface of the crystals, the formation and entanglement of the second, third, and higher orders of dendritic branches are increased. the porosity decreases and the hydraulic resistance of the casting skeleton sharply increases. Due to this, the filtration supply of the solidifying casting is significantly hampered, and at the end of the solidification period, higher pressure, created by ultrasound, whose intensity increases by 1.9 W /, is required to impregnate the pores with the melt. cm for every 10% increase in the amount of solid phase. The indicated limits of the required ultrasound intensity are due to the large variety of the crystalline structure of the solidifying castings and depend on the physical properties of the melts. Below are nine examples of the implementation of the proposed method in comparison with the method taken for the prototype, and the method without ultrasonic treatment. Conducted ultrasonic processing of hardened ingots of bronze brand VROY. The source of oscillation is the UZT-9 generator, equipped with automatic tuning to the resonant frequency. The ingots weighed 10 kg, the temperature was measured with chromel-aluminum thermocouples, and the results were recorded with a potentiometer. The amount of the solid phase formed was determined using the Cu-Sn state diagram, depending on the ingot temperature. Ultrasonic processing of ingots was carried out after the formation of 38, 43 and 48% of the solid phase of the ingot. For this, a mechanical contact was established between the ultrasonic oscillator and the crystal skeleton. The resonant frequency was tuned automatically. Processing was carried out in three modes. The initial treatment intensity is O, 7; 3 and 7 W / cm. An increase in intensity of 1, 4, and 9 W / cm for every 10% of the newly formed solid phase, respectively. In order to improve the comparative results under similar conditions, ingots were cast and crystallized without ultrasonic treatment and according to the method taken as a prototype. Samples were cut from the ingots to determine the density and strength of the bronze. The density of the samples was determined by the hydrostatic method, and the strength standard. The test results are presented in the table.

Claims (1)

Claim A method of treating a crystallizing alloy with ultrasound, including the action of the crystallizing melt in the direction of gravity by ultrasonic vibrations, the frequency of which is adjusted and maintained during crystallization in resonance with the natural frequency of the casting, characterized in that, in order to improve the quality of castings, in particular density, by intensifying the filtration power, the contact between the casting and the emitter is established after the formation of at least 38-43% of the solid phase and intensify ultrasonic vibrations 0,7-7., 0 W / cm ^1, and then to increase the intensity 1-9 W / cm for every ^5% increase in the number 9.5-10.5 'solid phase.