Ultrasonic impulse reinforcing finishing of metals

Applying of modern machines and gears working with high speeds requires from designers and technologists solution of the problem related with increasing its' working limit and working limit of parts, which are comprised in machines and gears.

Quality of surface layer is one of the most important factors defining longevity of machines and gears. Surface of mated parts thoroughly processed by well-known methods is bearer of residual macro and micro stresses, wear macro and micro chaps, embedded abrasive and other defects. To increase durability and wear resistance of parts it's necessary to apply treatment, which improves physical properties, structure and micro geometry of surface.

The following classical the most wide-spread methods of quality improvement are known:

• shot-streaming treatment: micro hardness of surface increases insignificantly, surface asperity almost don't reduce, wear durability increases by a factor of 1.5 and more;
• rolling by ball or roller: micro hardness of the surface increases in 40-60%, asperity reduces approximately from 5 to 10 class, it's usually required to make some passes of instruments along part, cold-hardening with significant thickness is constituted;
• broach: micro hardness of the surface increases in 25-35%, asperity reduces approximately from 5 to 9-11 class, insignificant cold-hardening up to 1mm;
• mintage: micro hardness of the surface increases in 20-70%, cold-hardening thickness can be up to 20-25mm, wear resistance increases in 50-100%, working limit of parts increases twice and more;
• reinforcing by blast wave: micro hardness of the surface increases in 60-70%, cold-hardening thickness can be up to 40-50mm, that isn't obtained by any other methods, but it's applying is associated with well-known technological difficulties and isn't always possible.

Ultrasonic impulse reinforcing finishing.

The first information and data about this method of treatment appeared in works of prof. Muhanov I. I. in 1964. At the present time in Russia equipment for this method of treatment are manufactured by some companies. Significant progress in this sphere has "North-West Center of Ultrasonic Technologies" under the direction of d. t. s., prof Holopov Y. V. Another name of this treatment method is "Abrasive-free finishing of metals" - BUFO. Basing on the works of prof. Muhanov and developing it inventively, applying modern ultrasonic generators and ultrasonic transducers of own elaboration, our company "Ultrasonic technique - INLAB" LLC developed, manufactures and supplies set of ultrasonic equipment IL-4 for carrying out ultrasonic impulse reinforcing finishing since 1996. The scheme of applying this method is at fig.1.

Fig. 1.

Ultrasonic treatment is used after lathe finishing. Ultrasonic instrument is installed to cutter holder of universal lathe, under the action of static force created by pressing and dynamic force created by ultrasonic oscillation system plastically deforms surface layer of part, increases micro hardness, removes residual macro and micro stresses, smoothes surface roughness and in total constructs improved surface layer with regular disposition of micro relief.

Results of applying this method of parts' surface layer improvement include characteristics of single classical methods of treatment:

• micro hardness of surface depending on initial and kind of metal increases in 300%;
• asperity reduces from 5 to 9-14 class, this quality of surface can be obtained not only at thermal treated and crude steels, but also at cast-iron, non-ferrous and stainless metals and alloys;
• cold-hardening thickness may be up to 0.1mm, in single cases it's possible to realize mode of cold forging with cold-hardening thickness up to 15-20mm;
• by optimum combination of static and dynamic forces of ultrasonic treatment it's possible to increase fluidity limit of metal and thus make a correction of part geometry;
• limit of contact persistency increases in 10-20%;
• absence of embedded to surface grains of abrasive increases up to 2 times working limit of mated parts (sliding pairs, impermeable glands, packing glands etc.), possibility of producing details for food industry (batchers etc.) and any machines and gears, where availability of abrasive in technological zone is inadmissible appears due to ultrasonic treating;
• regular micro relief increases property of detention oils and greases by treated surface;
• regular micro relief extra reduces wear for reciprocal movement of mating parts;
• corrosion resistance of treated surface increases.

As a result of complex enumerated properties parts of machines and gears, which were subject to ultrasonic impulse finishing has more wear resistance, cycle durability contact wear etc. than after grinding, rolling by ball and many other ultimate finishing methods of parts' surface treating.

At fig.2 there is a photo, where ultrasonic impulse finishing of figure-of-revolution outer surface at lathe are shown.

Easy using - stunning result

Fig. 2.

Ultrasonic instrument, elaborated and manufactured by "Ultrasonic technique - INLAB" LLC (fig. 3) allows to treat not only cylindrical details, but also details with eccentricity up to ±5mm.

Fig. 3.

One should consider ultrasonic reinforcing finishing as not dimensional. Size of necessary allowances is defined experimentally, depending on concrete technological parameters of treatment. In general case dimensions of details almost don't change.

Indenter is should to be primed after some time of working, priming proceeds by user and it isn't difficult.

Productivity of ultrasonic impulse reinforcing finishing is defined by the same factors, as treatment by cutting at regular mode.

It can has great importance that possibility of exception from technological system when treating details some operations and machinetools appears. Applying of ultrasonic equipment set I-4 for impulse reinforcing finishing of figure-of-revolution outer surface at lathe elaborated by "Ultrasonic technique - INLAB" LLC doesn't consider with some exceptions necessity of elaboration special technology of applying for this equipment at industry. A day of co-operative work of skilled specialists (technologist and turner) is enough to master this instrument and it's applying. Then working with ultrasonic equipment at first-order approximation will not differ from regular turner's work with cutters.

Ultrasonic set I-4 consists of:

• ultrasonic generator I-10-0.63, power output is 630 W, graduated turning of the output power, 50%, 75%, 100% of the nominal output power, working frequency is 22 kHz ± 10%, power supply - 220V, 50 Hz;
• ultrasonic instrument, clipped into cutting holder of lathe, base of instrument - magnetostrictive ultrasonic transducer with changing instrument-indenter;
• 3 changing indenters;
• connecting cable with length 4m;
• passport for ultrasonic generator and passport for ultrasonic set I-4.

Guaranty for ultrasonic generator and instrument is 1 year of continued work. Resistance of indenter depends on treated material and treatment modes. Indenter allows multiple priming by user.

Ultrasonic set is universal suit of ultrasonic equipment, it's useful for wide applying at device constructing and engineering, it can be ordered, manufactured and supplied to client without complementary accommodation of ultrasonic equipment technical parameters.

All above relates to ultrasonic impulse reinforcing finishing of figure-of-revolution outer surface at lathe.

Ultrasonic set for processing of figure-of-revolution inner surface and hollows at lathe isn't so universal. While creating of ultrasonic equipment for this applying a series of technological limitations appear. Necessity of putting into a hollow complex ultrasonic sonotrode inflicts limitations to minimum diameter and to maximum depth of processing hollow pass. At fig. 4 there is ultrasonic set for treating figure-of-revolution hollows with minimum diameter 60mm and maximum depth of pass 240mm.

Fig. 4.

Manufacturing and supplying of ultrasonic sets for treatment of figure-of-revolution inner surfaces at lathe requires precursory accommodation of technical parameters, so in most cases the set is unique and useful for solution of concrete problem.

Considering this method regardless to lathe it's possible to realize method of plane surfaces treating. Instrument for installation to mill is performed at fig. 5.

Fig. 5.

At fig. 6 there are examples of treated details of different materials.

Steel 40X	Duralumin	Bronze	Stainless steel

Fig. 6.

Fig. 7.

At fig. 7 different variations of indenters are performed.

Using experience of many years at ultrasonic impulse reinforcing finishing realization our company has elaborated and manufactured set effecting Ultrasonic reinforcing and correction of threads of pump-compressor tubes. In this set method of ultrasonic reinforcing is used for increase of quality and improvement of complex geometrical surface and thread characteristics.

By using ultrasonic equipment that is being elaborated and emitted by "Ultrasonic technique - INLAB" LLC it's possible to obtain the effect you need which isn't achievable by any other methods. All emitted equipment is protected by patents of Russia.