WO2008150250A1 - Ultrasonic tool for hardening and relaxation treatment of metals - Google Patents

Abstract

The invention relates to an ultrasonic tool for deformation hardening and relaxation treatment of metals. Said invention is based on the use of ultrasonic oscillation energy and can be used in the machine and ship building industries and others industrial sectors, in particular for treating metal surfaces and weld seams of critical structures, operating under conditions of vibrational loads, in order to increase the fatigue strength thereof. The aim of the invention is to reduce the level of heating of an ultrasonic converter by increasing the effectiveness of forced air cooling and the reliability of temperature monitoring of an ultrasonic piezoceramic converter and to increase the service life of the working surfaces of the tool and the impact elements thereof. For solving said problem, a temperature sensor is mounted directly on the rear face of the ultrasonic converter. Some of structural elements are provided with orifices for passing compressed air into a treatment area and the emitter parts are provided with a heat exchange surface in the form of a radiator. The operating end face of a vibrational speed transformer and the ends of the impact elements are provided with a hard-alloy coating. The reciprocating motion sensor of the emitter is made in such a way that it is magnetosensitive and is placed in front of a permanent magnet which is secured in a body. The use of the invention for ultrasonic impact tools makes it possible to reduce the heat of the ultrasonic converter, extend the operational cycle, decrease the wear of the surfaces of the impact elements and the emitter, control the processing modes and to increase the performance and the reliability of the tool.

Description

 ULTRASONIC TOOL FOR STRENGTHENING AND RELAXING PROCESSING OF METALS

The invention relates to the field of technological use of energy of ultrasonic vibrations to create a high-frequency impact on metals and can be applied in engineering, shipbuilding and other industries, in particular, for strain hardening and relaxation processing of metal surfaces of parts and welds of critical structures that work in vibration loading conditions and are subject to fatigue failure. Surface hardening of metal products and welds, as a final technological operation, significantly increases the efficiency of machine parts, increases their quality and service life. Today, methods of surface plastic deformation (PPD), such as rolling by balls and rollers, shot peening, pneumatic and electrodynamic processing, vibration rolling, and others, are widely used. Significantly increased interest in high-energy types of surface treatment, which include surface hardening using ultrasonic vibrations. The test results and operating practice show that in the processing of metals and, especially, high-strength materials, the ultrasonic method is the most effective. With its help, it is possible to significantly increase the mechanical properties of structural materials and, above all, to increase the fatigue strength and wear resistance. In turn, the productivity and quality of the ultrasonic treatment process, energy consumption and ease of use are largely dependent on the design and type of ultrasonic instrument.

A known ultrasonic tool for finishing the surface of parts (Russian Patent JNa 2266805 Cl, IPC B24B 39/00, 2005), containing an ultrasonic emitter, which includes a magnetostrictive transducer and a vibrational velocity transformer (TKC) rigidly connected to it. The emitter is located in a tank equipped with a liquid cooling system. The tank is located in the tool body and contacts it through a spring, which is necessary for pressing the emitter to the work surface with a certain force. According to the invention, the TKC is rigidly connected by a pin to a cylindrical hardened steel extension waveguide, the length of which is a multiple of λ / 2, where λ is the longitudinal wavelength in the waveguide material. At the weekend the end of the waveguide is a holder having the form of a glass with through holes in the end, in which the rods with bulges are installed. An annular groove is made in the nodal plane of the waveguide, in which the balls are placed with the possibility of rolling, and the union nut screwed to the glass limits its movement along the axis of the waveguide towards the placement of the rods due to the balls protruding above the surface of the waveguide. The tank is equipped with a coolant inlet and outlet and is secured with a union nut in the TKC nodal plane.

In the known device, as a source of ultrasonic vibrations, a magnetostrictive transducer is used, the efficiency (efficiency) of which is significantly lower than that of a piezoelectric transducer. In addition, magnetostrictive converters require liquid cooling and the supply of appropriate hoses, which in total increases the weight of the device and creates inconvenience, especially when working with a hand tool. The use of a steel waveguide extension also increases the weight of the device and the acoustic loss due to the additional threaded connection.

Also known is a vibration impact tool with ultrasonic excitation (Russian Patent JMo 2179919 C2, IPC B25D 9/14, B06B 1/08, B06B 1/12, B24B 39/04, 2000), comprising a housing with elastic vibration-isolating gaskets and an ultrasound source, consisting of magnetostrictive transducer and TKC. The ultrasound source is housed in a housing with the possibility of reciprocating motion, and the clip with strikers is installed near the end of the TKC. The device has a forced air cooling system, while the magnetostrictive transducer and TKC are fixed in the sleeve, which is located on the slide rails connected to the housing. Between the outer surface of the sleeve and the inner surface of the housing there is a gap for the release of compressed air.

The known device uses an air cooling system to remove heat from a magnetostrictive vibrator that does not have a developed heat exchange surface, which reduces the cooling efficiency, and the absence of a temperature sensor can lead to uncontrolled overheating and failure of the tool. The holder with the strikers, which become very hot during operation, is the second heat source, which in this case is not amenable to forced cooling, therefore, heat generation in the processing zone heats the TKC and other parts of the device, which leads to additional interruptions in operation for cooling them and reduces performance. Another disadvantage of the known device is its fragility, which is caused by the abrasion of steel dies, which in turn destroy the end face of the TKC. Lack of an indicator of the clamping of the strikers to the surface to be treated and a complex clamping system, consisting of a spring and compressed air, lead to instability of ultrasonic vibro-shock processing (UZVUO).

The closest to the proposed device in terms of features and technical result is an ultrasonic tool for strain hardening and relaxation processing of metals (Patent of Ukraine N ° 68264, IPC B24B 39/00, B06B 1/06, 2007), containing a housing with a protective rubber cover and cover , in which an ultrasonic transducer connected to the TKC and having a holder with percussion elements is installed. The ultrasonic transducer is mounted in a glass with the possibility of axial reciprocating motion inside the housing. Here are the sensors for the reciprocating motion of the ultrasonic transducer and its temperature, which are included in the start and stop system of the ultrasonic oscillation generator. A handle with an elastic cover and the possibility of rotation around the axis of the housing is also fixed on the body. The metal cup covers the ultrasonic transducer and the TKC, which in the nodal plane is mounted on the edge of the cup through a vibration-proof gasket. Here, a cylindrical nozzle is also installed on the same axis with a thin end of the TKC, and the holder is located on the free end of the nozzle with the possibility of rotation around its axis and quick removal. The pneumatic chamber is made in the form of a cavity between the lid and the bottom of the glass, and the ultrasonic transducer is a composite piezoceramic vibrator. A spring is located in the pneumatic chamber, providing reciprocating movement of the moving part of the tool.

The known instrument has an ineffective cooling system due to the fact that the ultrasonic transducer does not have a developed heat exchange surface and is placed in a sealed metal canister, which only gives off heat through the movement of atmospheric air when the volume of the air chamber changes. The heated holder with hammers is cooled only by free cooling. Placing the temperature sensor at the bottom of the glass leads to an error in measuring the temperature of the ultrasonic transducer, so the instrument may overheat and fail during prolonged use. Using an optical sensor with a shutter as a reciprocating motion sensor leads to malfunctions during operation of the tool in conditions of vibration, shock, exposure to dust and humidity.

Drummers eventually destroy the end face of the TKC and wear themselves, which reduces tool life. Installing the spring in the air chamber between the bottom of the cup and the cover the housing at the point where the wires are connected to the temperature and reciprocating motion sensors, as well as the power wires of the ultrasonic transducer, can cause wire breaks during repeated bending deformations.

The basis of the invention is the task of improving the well-known ultrasonic tool for strain hardening and relaxation processing of metals by reducing heating by increasing the efficiency of forced air cooling of the ultrasonic transducer and heated structural elements, as well as increasing the reliability of temperature control for the most critical heating element - piezoceramic ultrasonic converter. At the same time, measures have been taken to reduce wear on the working surfaces of the strikers and the end face of the TKC. This will make it possible to increase the productivity of the ultrasonic air-ignition control system, increase the reliability and service life of the tool, and ensure safety and convenience during its operation.

To solve the problem in an ultrasonic tool for strain hardening and relaxation processing of metals, containing a housing in which a metal cup is mounted with sliding possibility, covering with a gap an ultrasonic piezoceramic transducer (SCP), which contains a vibrational velocity transformer (TKC) connected in its nodal the plane with the edge of the glass, where on the same axis with the output end of the TKC, a cylindrical nozzle is fixed on which the holder with shock is elastically fixed elements, a temperature sensor mounted on the bottom of the glass, a pin-shaped stopper located in the longitudinal groove of the body and mounted on the surface of the glass, the glass being mounted with the possibility of axial reciprocating movement relative to the body, which is detected by the displacement sensor, and the sensor is included in the system start generator of ultrasonic vibrations, and in the pneumatic chamber between the bottom of the glass and the housing cover there is a compression spring, according to the invention, an indicator is mounted in the tool body p is the pressure force of the shock elements in the form of a calibrated scale for the displacement of the stopper, the temperature sensor is installed on the rear end of the soft starter, in the bottom of the glass there is an opening with a fitting for the passage of compressed air, and in TKC there are through holes that connect the cavity of the glass with the space between the output end of TKC and the nozzle, while the holder is provided with holes in the axial direction, the soft starter has a heat exchange surface in the form of ribs, the height of which is less than the gap between the glass and TKC, and the outlet end face of the latter and the working ends of the shock elements s have a high hardness, e.g., due to the carbide coating, wherein the displacement sensor is designed as a magnet mounted on the case, and installed opposite it in a glass of a magnetic sensor, for example, a Hall sensor.

To increase the efficiency of heat removal from the ultrasonic transducer, forced air cooling is used. Cold air through the fitting in the bottom of the cup enters its internal cavity, passes in the gap between the heat-emitting ribs of the piezoceramic transducer plates, cooling them, then through the through holes in the TKC it enters the nozzle cavity, and then the hammer holders and through the holes in the latter exit into the surrounding space taking also heat from the heated parts of the shock assembly. The large heat exchange side surface of the converter plates and the perforations in the holder provide efficient heat transfer. Fixing the temperature sensor directly on the back plate of the piezoceramic transducer increases the reliability of temperature information of overheating sensitive piezoceramic rings. At the same time, the ultrasonic generator is switched off by the instrument when the rings are heated to a predetermined temperature under extreme conditions. The next start of the tool is possible only after the temperature of the rings is reduced to an acceptable one, which increases its reliability.

The displacement sensor of the ultrasonic transducer relative to the housing turns on the ultrasonic generator only after reliable contact of the projectiles with the surface of the processing zone and automatically turns it off after removing the minimum force of the projectiles. It is made in the form of a magnetic Hall sensor. The sensor is enclosed in a sealed stainless steel cup and interacts through its walls with a magnet that is mounted on the housing. This design increases the reliability of its operation, which reduces the risk of the converter idling and, accordingly, its unacceptable overheating.

The implementation of the original end face of TKC with the deposition of a hard alloy, for example, by the electrospark method, significantly reduces the destructive effect of impactors on the radiating surface, and increases the tool life. The same coating is carried out on the spherical surface of the impact elements, which acts on the surface to be machined, which also increases the overall resource of the tool, improves the quality of the ultrasonic shock absorbers and reduces tool downtime for replacing worn hammers.

The elastic axial reciprocating movement of the ultrasonic transducer relative to the housing provides a shock to the impactors to the work surface with a certain force. The degree of plastic deformation of the metal surface depends on the clamp force at a constant amplitude of the oscillations of the transducer, therefore, control of the pressing force by the degree of elastic deformation (displacement of the locking pin relative to the housing) by the displacement indicator makes it possible to control the modes of the ultrasonic vibrating system and optimize it depending on the strength of the material being processed, as well as on the design features of the part or product.

The vibrations that occur during the processing of products are largely damped due to the shock-absorbing properties of the spring and the air that is inside the pneumatic chamber. The use of the damping properties of air, when it is displaced from the pneumatic chamber through a narrow damping slot or retracted during the reverse stroke, reduces the harmful effect of vibrations on the operator's hands.

The invention is explained by schematic drawings, in which figure 1 shows the proposed ultrasonic instrument in section, and figure 2 is a view from the side of the pin (view along arrow A).

An ultrasonic tool for strain hardening and relaxation processing of metals contains an ultrasonic composite piezoceramic transducer 1, which consists of two piezoceramic rings 2, compressed with a tie pin 3 between the back plate 4 and the step transformer of vibrational velocity (TKC) 5, made, for example, of titanium alloy, which has an output end b of smaller diameter. The ultrasonic transducer is installed with a gap in a sealed stainless steel cup 7 so that its edge 8 is connected to the TKC nodal plane through a vibration isolation seal 9. A cylindrical nozzle 10 is attached to the edge 8, which is placed on the same axis as the TKC. At the output end of the nozzle mounted holder 11 in the form of a glass with the possibility of rotation around its axis. On the outer surface of the holder there are spherical depressions 12, where the ball 13 enters, pressed by a flat coil spring 14 to fix the holder. Impact elements 15 are enclosed in the openings of the end face of the holder, which have thickenings at one end, preventing them from falling out of the holder. The glass 7 is installed with a gap in the housing 16 on two slide rails 17 made, for example, of fluoroplastic. The pneumatic chamber 18, formed by the inner surface of the housing 16, the outer surface of the cup and the guides 17, is connected to the external environment through the damper slot 19. A compression spring 20 is placed in the pneumatic chamber between the edge 8 of the cup and the protrusion 21 of the housing. To prevent the cup 7 from falling out of the housing 16, a stopper is fixed on it in the form of a pin 22, which can move in the longitudinal groove 23 of the housing. A magnetic sensor 24 (for example, a Hall sensor) is mounted in the glass 7, which interacts with a magnet 25 located opposite it in the housing 16 during the reciprocating motion. an ultrasonic transducer 26 is mounted on the end of the back plate 4. A cable 28 is connected through an airtight seal in the lid 27 of the glass 7, connected at one end to an ultrasonic generator (not shown), and the other to piezoceramic ring electrodes 2. A magnetic sensor 24 and a temperature sensor 26 are connected appropriate wires to the start-up circuit of the ultrasonic generator.

The housing 16 and the handle 29 attached thereto are equipped with elastic cuffs 30 and 31, for example, of porous rubber. The degree of displacement of the pin 22 in the groove 23 of the housing is displayed on the indicator 32 (Fig. 2) in the form of a ruler or bar, which has multi-colored zones (for example, green, yellow, red). In the lid 27 of the glass 7 installed fitting 33 for supplying cooling air. The back plate 4 and the thick part of the TKC 5 have a developed heat-exchange surface in the form of ribs 34. The cavity of the cup 7 is connected by the holes 35 in the TKC with the space between the thin end of the TKC 6 and the nozzle 10, and in the holder 11 holes 36 are made along the impact elements 15 for the cooling outlet air to the atmosphere. A carbide plate, for example, of BK20 alloy, is brazed to the end face 37 of the thin end of TKC 6, or a carbide coating of the same alloy is applied by electrospark. Impact elements 15 also have a carbide coating on the working spherical surfaces in contact with the surface of the product.

Ultrasonic instrument works as follows. First, the voltage of the electric network is applied to the ultrasonic generator and the air cooling system is turned on. Compressed air enters the tool through the nozzle 33, passes through the channels between the cooling fins 34, through the through holes 35, 36 in the TKC 5 and the holder 11. Impact elements 15 are brought into contact with the work surface before starting work. By pressing the handle 29, the axial displacement of the entire oscillatory system of the tool, located in the cup 7, relative to the housing 16 by 3-5 mm is achieved until the magnetic sensor 24, which is mounted on the cover of the cup 27, falls into the range of the magnet 25. B At this moment, a high-frequency voltage is applied to the piezoceramic plates, which transform it into mechanical vibrations of the ultrasonic frequency. TKC increases the amplitude of oscillations at its free end to 20-30 microns. The shock elements 15 pressed to it begin to make forced vibrations, moving in the holes of the holder 11. In this case, the kinetic energy received by the shock elements from the ultrasonic transducer is spent on deforming the surface and on the elastic rebound back. The tool is pressed to the surface with a force of the order of 40-60H, the spring 20 is deformed and the pin 22 is displaced by the corresponding distance in the groove 23. The amount of displacement proportional to the clamp of the shock elements 15 is displayed on indicator 32, which has a metric scale and can be controlled by the operator. The air in the pneumatic chamber 18 during compression of the spring is also compressed and begins to escape through the damper slot 19. The tool is informed of translational motion in the direction perpendicular to its axis and the product is processed, covering the entire necessary surface.

Losses that occur in a piezoceramic ultrasonic transducer heat it. Due to the large heat-exchanging surface of the fins 34, heat is removed by the air of the cooling system to the environment, simultaneously cooling the impact elements 15 and the holder 11. The air jets leaving the holes in the holder prevent the ingress of processed products (scale, rust, dirt, etc.) into the holes of the holder. In cases of operation at elevated external temperatures and possible violations of the technological regime, when the temperature of the piezoceramic rings 2 can reach a critical value, constant monitoring of the temperature by the sensor 26 is provided and the ultrasonic generator is switched off when the transducer is heated to a predetermined temperature.

Vibrations (low- and high-frequency) that occur in the tool during processing of products are partially absorbed by the vibration isolation seal 9. Additionally, the vibrations are absorbed by the spring 20 and the pneumatic chamber 18, which significantly reduces their harmful effect on the operator’s hands. The reduction of vibration loads on the operator is also due to the vibration isolation properties of elastic cuffs 30, 31. Such multi-stage protection (using various physical factors - elasticity, friction, viscosity) from the action of vibrations allows to reduce their level to the values allowed by the relevant regulatory documents when working with ultrasonic equipment. The ability to rotate the holder 11 with impact elements around its axis reduces the wear of the end face of the TKC 5, and the ability to quickly replace the holder together with impact elements increases the convenience of working with the tool due to time savings.

The use of effective heat removal from a heated piezoelectric transducer with control of its temperature and cooling of the head with shock elements increases the reliability of the tool and operational safety, and maintaining the working state of the TKC end extends the life of the tool. The multi-stage vibration protection system reduces the level of vibration in all modes of vibration-shock processing. The control of the pressure force of the shock elements, the increase in the resource of the output ends of the shock elements and their quick replacement increases the quality and UZVUO performance. The special design of the reciprocating motion sensor increases the reliability and ease of use of the instrument.

Example. A device was manufactured that had a maximum amplitude of oscillations of the piezoelectric transducer at the end of the TKC near ZOkmkm, the operating frequency of the ultrasonic generator was 22 KHz and consumed 400 W of power from the electric network. When using forced air cooling, the ultrasonic transducer and holder with shock elements had an allowable temperature of up to 60 ⁰ C with continuous operation of the device for 15 minutes Vibrations and shock loads that occurred during the processing of metal surfaces were significantly reduced by the vibration isolation system, which ensured a long and safe operation of the operator. The durability of the working end of TKC during the processing of steels of medium strength increased by 3-4 times. By maintaining the working state of the end face of TKC and the output ends of the shock elements, the surface treatment efficiency and productivity increased.

SUBSTITUTE SHEET (RULE 26)

Claims

 Claim An ultrasonic tool for hardening and relaxation processing of metals, comprising a housing in which a metal cup is mounted on the slide rails, enclosing with a gap an ultrasonic piezoceramic transducer to which a vibrational velocity transformer (TKC) is connected, connected in its nodal plane to the edge of the cup, where a cylindrical nozzle mounted coaxially to the output end of the TKC, on the free end of which a holder with percussion elements is elastically fixed, the stopper in an ide pin mounted on the surface of the glass and placed in the longitudinal groove of the housing, an air cooling system, a temperature sensor, the glass being mounted with the possibility of elastic axial reciprocating motion relative to the housing, which is detected by the sensor, the sensor being included in the start-up system of the ultrasonic vibration generator, characterized in that an additional indicator of the pressure force of the shock elements is mounted in the form of a scale for displacing the stopper, and the temperature sensor is mounted on an ultra transducer, in the bottom of the glass there is a hole for air supply, and in TKC there are through holes that connect the glass cavity with the space between the output end of the TKC and the nozzle, the holder has holes directed towards the surface to be machined, the ultrasonic transducer and TKC in the glass volume are equipped with heat exchange surface in the form of ribs, the height of which is less than the gap between the glass, the ultrasonic transducer and TKC, the output end face TKC and the output ends of the shock elements are made of high hardness relative to When contacting the material of the surface with which they are in contact, for example, with a carbide coating, the reciprocating motion sensor is magnetic and mounted in a glass of non-magnetic material, while a permanent magnet is fixed in the housing, a compression spring is installed between the edge of the glass and the inner protrusion in the housing placed in a pneumatic chamber created by the cylindrical surfaces of the housing and the glass and connected to the external environment through a damper slot. SUBSTITUTE SHEET (RULE 26)