RU2365668C2 - Method of restoration of sound caracteristics of metal cast percussion musical instrument - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to restoration of damaged metal articles, namely to the methods of fixing internal defects in cast percussion musical instruments occurring at the time of using the instruments as well as during manufacturing them and the invention can be used to fix the defects of bells. The instrument is heated in the gaseous medium under the pressure of 1000-2000 atm to reach the temperature of plastic flow of the instrument material and it is kept for as long as one hour minimum. Then the pressure is reduced by 2-3 times and the instrument is kept for 3 hours minimum, which is then followed by pressure release to the atmospheric level with the following temperature reduction to the room temperature for as long as it is required for the instrument material to recrystallise. Neutral gas environment is used, for instance, inert gas environment.

EFFECT: fixed internal defects of the instrument material such as cracks, bubbles, pipes, slag inclusions and fine clear sound.

2 cl, 9 dwg

Description

The invention relates to the restoration of damaged metal products, in particular to methods for restoring the sound characteristics of metal cast percussion musical instruments arising both in the operation of the products and in their manufacture, and can be used in bell-ringing to fix bell defects, improve acoustic properties and increase strength data bells used for ringing.

A known method of eliminating porosity in the casting of metal bell housings by extrusion molding with crystallization under pressure (patent RU No. 2307402, class G01K 1/00, publ. September 27, 2007). The method allows to avoid the appearance of cracks in the process of casting a bell. However, the method may not be applicable to eliminate internal defects of already cast products.

A known method of eliminating cracks in the surface layer of a metal part, including heating the part in a muffle furnace and subsequent fusion of the crack with a laser-arc source (patent RU No. 2056253, class B23P 6/04, publ. March 20, 1996). This method has limited application, since it allows you to eliminate cracks in the details of a simple form; This method, for example, does not allow to eliminate cracks in large-sized products of complex shape, which can also include bell products.

The closest in technical essence and the achieved effect is a method of eliminating cracks in the surface layer of a part, including heating the part at a temperature of at least 970 ° C in a gas medium containing nickel chloride, after heating, alimentation or chromoalting is carried out at a temperature of at least 400 ° C and then carry out plastic deformation of the alitized or chromoalitic layer with a gaseous medium under a pressure of at least 30 MPa at a temperature of at least 600 ° C (patent RU No. 2305027, class B23P 6/00, published on August 27, 2007).

This method also has limited use, since it does not allow to eliminate internal defects in the form of discontinuities, shells, cracks, gas voids of cast metal products, in particular bells and other cast percussion musical instruments.

As can be seen from the above analogues, the problem is that church and other bells for many centuries are made by casting (mainly from bell bronze and cast iron) and must have internal defects in the form of discontinuities: cracks, bubbles, shells, slag inclusions and etc. These defects worsen the acoustic characteristics of the bell (timbre, clarity and playing time) and its performance, since any discontinuity is a stress concentrator that accelerates the split of the bell when it rings. Therefore, depending on the quality of the casting and operating conditions, the bell could last one day, or it could last centuries.

The objective of the invention is to develop a method for restoring the sound characteristics of metal cast percussion musical instruments to obtain beautiful clear sound.

The problem is solved by the proposed method of restoring the sound characteristics of a metal cast percussion musical instrument, which consists in the fact that the instrument is heated in a gas medium at a pressure of 1000-2000 atmospheres to the temperature of plastic deformation of the instrument material and is held for at least one hour, then the pressure is reduced by 2 -3 times and can withstand at least 3 hours, after which they carry out pressure relief to atmospheric pressure, followed by lowering the temperature to room temperature for a time sufficient o for recrystallization of tool material.

The method is carried out in a neutral gas environment, for example in an inert gas environment.

The invention consists in the following. A molten percussion instrument, such as a bell, is placed in a thermostat, which is filled with a neutral gas medium, such as argon. Figure 1 shows a diagram of the isostatic processing of the bell. The product is heated in a neutral atmosphere with an increase in pressure to 1000-2000 atmospheres until the temperature of plastic deformation of the material of the product is reached. In the diagram, this corresponds to the time interval T ₀ -T ₁ . For each material, this is its own indicator. So, for example, bell bronze reaches plastic deformation at 520-620 ° C. At the achieved temperature, the product is maintained for a certain time, (T ₁ -T ₂ ), but not less than one hour. In this case, during the period T ₁ -T ₂ , the compression of the product that has reached plastic deformation takes place. First, the compression is carried out at a pressure of 1000-2000 atmospheres (T ₁ -T ₂ ), then the product is crimped at a pressure of 2-3 times lower than the original for at least three hours (T ₂ -T ₃ ). This allows you to reduce the technological costs of maintenance of the thermostat, but to save the conditions for the beginning of recrystallization of the material. If the exposure time is less than three hours, the elimination of internal defects in the material of the bell may pass partially, which will not allow to achieve the desired quality result. This is followed by pressure relief to atmospheric pressure, the cessation of heating and cooling of the product in the thermostat to room temperature (T ₃ -T ₄ ). Recrystallization of the discontinuity material takes place, and the material becomes like forged. Figure 2 shows an enlarged photograph of bell bronze after processing the inventive method (pseudo-forged alloy).

The temperature schedule is developed individually for each bell so that at the first stage it facilitates plastic deformation, and then correctly recrystallizes the alloy in order to restore the acoustic properties of the bell.

For experimental confirmation, we took an old bell from bell bronze, made in Russia around the end of the 19th century, with a cut diameter of 545 mm and a weight of 99 kg (~ 6 pounds) (Fig. 3). The bell sounded bad, the duration of the sound was no more than 10 seconds, which is clearly not enough for a bell of this weight. The recorded acoustic characteristics confirmed the poor state of the bell, as shown in the diagrams of Fig. 4 (frequency diagram 0.1 seconds after the impact) and Fig. 5 (bell sound attenuation diagram). Unterton frequency - 301.70 Hz (note Pel +46), attenuation angle ~ 60 degrees. The sound was recorded with a MZ-R909 mini-disk laser tape recorder using an ECM-MS907 electret condenser microphone, followed by decoding of sound recordings on a computer using the Spectra-plus program. The bell was placed in a thermostat, the latter was filled with argon and the bell was held at a temperature of 610-620 ° C and argon pressure of 1500 atm for 3 hours. Then the pressure in the thermostat was reduced to 500 atm, and at the temperature of 610-620 ° C, the aging process was continued for 5 hours. After that, the pressure was released to atmospheric pressure, and the bell cooled with the thermostat to room temperature (about 12 hours). In the experiment, a thermostat of the Swiss company "ABRA" was used with the dimensions of the loading basket: diameter - 700 mm and height - 1500 mm. Inspection of the bell after repair showed that the appearance and dimensions did not change (Fig.6). At the same time, the sound became noticeably better and longer, the sound is even with barely noticeable beats. The final assessment of the correction of internal defects of the bell gave an analysis of its acoustic characteristics before and after repair. In Fig.7 shows the frequency diagram of the sound of the bell after eliminating the internal defects of the bell, and Fig.8 and Fig.9 is a diagram of the attenuation of sound of this bell (Fig. Shows a three-dimensional diagram). It can be seen from these diagrams that the non-interton slightly changed 309.52 Hz (note # Pel -9), as it should be, in a larger direction (by 45 cents, i.e. by almost a quarter tone). The other overtones have changed accordingly. The duration of the sound has increased. Attenuation angle increased from 60 to 82 degrees

Thus, the claimed method allows to eliminate internal defects in the form of discontinuities: cracks, bubbles, shells, slag inclusions, etc., in metal percussion musical instruments. This improves the acoustic characteristics of the bell (timbre, clarity and playing time) and its performance. As a result of such processing, the bells with the configuration and composition of the material get the perfect sound, and their service life is extended many times.

The experiment showed that the inventive method is applicable for the "treatment" of old bells, in which, in addition to the initial defects, friability increases and stresses accumulate as a result of the natural aging of the material.

Claims (2)

1. A method of restoring the sound characteristics of a metal cast percussion musical instrument, which consists in the fact that the instrument is heated in a gas medium at a pressure of 1000-2000 atmospheres to the temperature of plastic deformation of the instrument material and held for at least one hour, then the pressure is reduced by 2-3 times and incubated for at least 3 hours, after which they carry out pressure relief to atmospheric pressure, followed by lowering the temperature to room temperature for a time sufficient to recrystallize the tool material. 2. The method according to claim 1, characterized in that it is carried out in a neutral gas environment, for example in an inert gas environment.

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