Installation for plasma hardening of KTZ wheels. Manual plasma hardening method

Owners of patent RU 2313581:

The invention relates to the field of heat treatment. To obtain a hardened surface without melting with a sufficient depth of hardening, surface hardening is carried out by moving a direct-action plasma arc along the surface of the hardened product at reverse polarity, when the electrode is the anode and the product is the cathode. 3 ill.

The invention relates to mechanical engineering and is intended for surface hardening of parts.

It is known that surface hardening (hardening) of parts is carried out with gas burners, high-frequency inductors, laser beams and other sources of surface heating. Since the 80s, plasma hardening with a direct arc has become widespread; it burns between the electrode (plasmatron) and the product. In this case, an arc of direct polarity is used, when the non-consumable electrode is the cathode, and the product is the anode. (Metal science and heat treatment of metals, 1988, No. 12, p. 35 in the article “Strengthening the working surfaces of cast iron parts by plasma melting” by N.S. Shepelev, M.V. Selivanova and others).

The disadvantage of plasma hardening with direct polarity is that the quality of hardening largely depends on the speed of movement of the plasma arc along the surface of the product. With its increase, the depth of hardening sharply decreases (Welding production, 2003, No. 2, p. 26 in the article “Surface hardening of steel parts by a compressed electric arc” by A.E. Mikheev, S.S. Ivasev and others). The properties of the hardened layer are influenced to an even greater extent by the length of the arc. Usually, for each mode, the optimal arc length is selected, at which the arc burns stably. None of the authors of known publications has attempted to study the effect of arc length on hardening properties. This happened because it is extremely difficult to trace. Usually, even a small increase in arc length from the optimal value sharply reduces the depth and hardness of hardening, and shortening the arc leads to melting of the surface, which is often a rejection sign.

The high sensitivity of the quality of hardening to the speed of movement and the length of the plasma arc has determined that plasma hardening is carried out only in automatic installations, where the two above parameters can be precisely adjusted and accurately maintained during the hardening process. Until recently, manual plasma hardening was not used precisely because the inevitable fluctuations in the manual process in the arc length and hardening speed lead to melting of the surface or do not provide its hardening.

The objective of the present invention is to reduce the sensitivity of hardening quality to the length of the arc, the speed of its movement and, based on this, to find the possibility of performing plasma hardening manually without melting the surface.

The problem was solved by using a reverse polarity arc for surface hardening, when the electrode is the anode and the product is the cathode.

Plasma hardening was carried out on an automatic installation of a cylinder made of steel 40 with a diameter of ⊘60 mm at a speed of 43.6 m/hour at a current of 60 A. It was found that both in direct and reverse polarity with an arc length of 9 mm (the distance from the plasma torch nozzle exit to surface of the part), melting of the hardened track does not occur. Figure 1 shows templates cut from a plasma-hardened sample performed at an arc length of 3 mm. It can be seen from them that when hardened with reverse polarity (pos. 1.), the surface of the hardened track does not have melting, and when hardened with direct polarity (pos. 2.), there is melting in the middle of the hardened tracks, forming a bead with a height of 0.12 mm. When increasing the length of the straight polarity arc to 6 mm, it was not possible to avoid melting, but the height of the bead decreased to 0.06 mm. Thus, an arc of reverse polarity, even with significant shortening, does not cause melting of the hardened surface, whereas even a slight shortening of an arc of direct polarity leads to melting.

Figure 2 shows the distribution of microhardness over the depth of hardening performed by an arc of straight polarity. It shows that with an increase in arc length from 3 mm to 9 mm, there was a decrease in: microhardness from H 500 500 to H 500 450; and hardening depths from 0.9 mm to 0.7 mm.

Figure 3 shows a similar microhardness distribution over the hardening depth, but performed by an arc of reverse polarity. In this case, the opposite pattern takes place: with an increase in arc length from 3 mm to 9 mm, the microhardness and hardening depth did not decrease, but increased: microhardness - from Н 500 480 to Н 500 640, and hardening depth - from 0.7 mm to 1 .1 mm. From this we can draw the following conclusions about the advantages of plasma hardening with reverse polarity compared to hardening with direct polarity.

1. With an arc length of 9 mm, when in both cases there is no melting, at reverse polarity the microhardness is higher (H 500 640 instead of H 500 430) and the quenching depth is greater (1.1 mm instead of 0.7 mm).

2. The maximum values ​​of microhardness and hardening depth at reverse polarity were obtained with a long (9 mm) arc, which is more convenient than a short one for conducting the process manually. Because with a short arc, the plasmatron body interferes with observation of it, which creates difficulties in directing the arc to the required location.

The foregoing allows us to conclude that in reverse polarity when plasma hardening is carried out manually, when fluctuations in the length of the arc and the speed of its movement occur, it is still possible to obtain a hardened surface without melting with a sufficient depth of hardening.

Practical application of the new method

A stamp made of 5ХНМ steel, weighing 2200 kg, is used for hot stamping of VT-20 titanium. During manufacturing, it is strengthened by volumetric hardening and tempering at HB 340. After 1100 stampings, it is upset to restore the engraving. As you move away from the surface during precipitation, the hardness of the engraving decreases and after 8 precipitations it reached HB 300. The stamp was subject to disposal, because its repeated volumetric hardening was impossible, because having lost in thickness, during volumetric hardening it would have received unacceptable deformation. Then the complex-profile engraving of the stamp was manually strengthened by plasma hardening at reverse polarity. Surface hardness increased to HB 540, and removal rate increased to 1862 stampings. Thus, manual plasma hardening not only extended the service life of the stamp, but also increased its durability during the company by 1.7 times (from 1100 pcs. to 1862 pcs.).

A stamp made of 8Х3 steel is used for cold blanking of blanks from 30ХГСА steel with a thickness of 6.5 mm. Usually ˜5 thousand pieces are cut on it, subjected to stripping, and an additional 10 thousand pieces are cut. and disposed of. The stamp along the working edges was strengthened manually by plasma hardening with reverse polarity; the hardness of the edges increased from HRC 52 to HRC 60. With two cleanings, the die cut 40 thousand pieces, which is 2.6 times more than the die cuts without plasma hardening (15 thousand pieces).

A die made of 5ХВ2С steel is used for hot blanking of blanks from 30ХГСА steel with a thickness of 10 mm. Usually, with periodic trimmings, he cuts 8 thousand blanks. After manual plasma hardening along the working edges, the hardness increased from HRC 54 to HRC 62, and the die operating time increased to 42.2 thousand pieces, i.e. 5.3 times.

Plasma hardening of the crown gear teeth of a steel-pouring crane was carried out. Difficult access to the surface of the teeth required increasing the length of the arc to 20 mm. This did not affect the quality of hardening and the service life of the ring gears increased from 6 months. up to 17 months, because 2.8 times.

A method of surface hardening of products, including hardening by moving a direct-action plasma arc across the surface of the product, excited between the electrode and the product, characterized in that in order to prevent melting of the hardened surface while simultaneously ensuring sufficient depth and hardness of the hardened layer, plasma hardening is performed at reverse polarity when the electrode is the anode, and the product is the cathode.

Similar patents:

The invention relates to methods for hardening products and can be used mainly in mechanical engineering for induction hardening of products such as axles, shafts, which have a complex configuration of hardened areas at the exit points of splines, grooves, flats, etc.

EXPERIENCE IN IMPLEMENTING PLASMA HARDENING

TO EXTEND THE SERVICE LIFE OF MACHINE PARTS

In the field of surface hardening of metal products, plasma exposure to concentrated energy sources is increasingly used. But often the approaches of designers to the design of parts with a wear-resistant working surface by hardening are limited by the requirements for the use of high-frequency heat, carburization or nitriding. The accumulated experience in introducing plasma hardening indicates the high economic efficiency of its use. Especially when the customer enterprise is the end user and comprehensively carries out the strengthening and operation of products. Technologically competent use of plasma hardening can significantly expand the list of hardened parts. Thus, this technology allows the heat treatment of parts of various sizes, both with relatively simple geometry (rolls, shafts, wheels, tires, pulleys, etc.) in automatic mode, and surfaces with a developed profile (gears, stamp engravings, sprockets, spline connections, etc.) in manual and automatic modes. Plasma hardening without reflow does not deteriorate the surface parameters after machining, therefore it is effectively integrated into the technological process of manufacturing or repairing parts as a finishing operation. A wide range of iron-carbon alloys hardened by plasma hardening - from low-carbon steels to cast irons - requires the implementation of installations that provide a wide range of control of the power, length and concentration of the plasma arc. The latest generation of installations developed by the department fully meets these requirements. These units are more powerful and allow you to harden parts to a depth of more than 2 mm. As an example, Fig. 1 shows data on the depth, hardness and structure of the hardening zone on a sample of 30ХН2МА steel.

One of these installations, designed for hardening with hand tools (UPZR1) is shown in Fig. 2. Rated operating current – ​​220 A. Installation weight – no more than 160 kg, supply voltage – 380 V, power – no more than 20 kVA, consumption of plasma-forming gas (argon) is no more than 10 l/min. The productivity of UPZR1 is 180...300 cm 2 of processed surface per minute.

The principle of operation of the UPZR is to create a direct plasma (compressed) arc using a power source, oscillator and plasma torch. Due to the thermal effect of the arc, when moving the holder with the plasma torch relative to the surface being processed, a hardened strip is obtained, the width of which is adjusted by the distance from the end of the plasma torch to the product and the voltage on the electromagnetic coil of the scanning device. In order to expand the technological capabilities of the installation, combined-action plasma arc treatment is also provided. In this case, two arcs burn simultaneously in the plasmatron (between the cathode and the plasmatron nozzle and between the cathode and the surface of the part), the electrical power of each of them is independently regulated, which allows the heat input to be varied within a wide range.

According to the results of production tests of club necks (steel 45) of the pilgerstan rolls of the Seversky Pipe Plant, hardened by a similar installation, wear resistance after plasma hardening increased three times, the service life of the hardened parts increased by 30% (Fig. 3).

With the help of this installation, the inserts of the PKZe-800 press dies are hardened for the production of steel grinding balls for PROMKO OJSC (Fig. 4). As a result of surface hardening of the engravings, the durability of the stamps increased by 2.7 times.

The service life of shot blaster blades (steel 45) hardened using UPZR-1 at Metalist OJSC (Kachkanar) increased threefold with an increase in hardness from 26..30 to 50 HRC (Fig. 5.).

At Seversky Pipe Plant OJSC, with the help of UPZR-1, a 45L steel gear was hardened directly on the crane of the scrap metal processing shop (Fig. 6). Before hardening, the wheel was urgently replaced with an unhardened one. Plasma heat treatment increased the hardness from HB 200 to 51 HRC.

For Uralpromtekhservice LLC (Ekaterinburg), plasma hardening of guide planes (ShKh15 steel) from HB 250 to 60 HRC was carried out (Fig. 7)

This installation is successfully operating at the Biysk Mechanical Plant. In 2012, the UPZR-1 installation was purchased by the Severonickel Combine of the Kola Mining and Metallurgical Company (Monchegorsk).

In 2011, the UPZR-2 installation was created using inverter arc power sources; it allows you to strengthen smaller parts with hand tools, for example, gears with module 3. Rated operating current - 150 A. UPZR-2 weight - no more than 80 kg, voltage supply network – 220 V, power consumption – 12 kVA. Productivity – 30…120 cm 2 of processed surface per minute.

Splined joints of edger shafts made of 5ХНМ steel for EVRAZ NTMK OJSC from 37 to 58 HRC were successfully processed using this installation (Fig. 8, 9).

Rice. 9. (x 2)

The UPZR-2 installation was used to strengthen grippers made of SCh30 cast iron for Yugson-service LLC (Tyumen) from 40 to 60 HRC (Fig. 10).

Installations for plasma hardening in manual mode make it possible to harden parts of spline joints, keyways, gear teeth, die engravings and other products with working surfaces of complex shape, but the results of hardening, especially the stability of the properties of the treated surface, are largely determined by the qualifications and experience of the operator.

Plasma hardening units can overcome this drawback in automatic mode. For example, the UPZA-1 installation (Fig. 11) for processing the surface of parts that are bodies of revolution, using standard mechanical equipment (machines, manipulators, rotators, etc.) for positioning the part and (or) a plasma torch.

Direct plasma torches are used as arc generators, i.e. a plasma arc burns between the cathode of the plasmatron and the product being hardened. Rated supply voltage – 380 V, rated operating current – ​​300 A, power consumption no more than 40 kVA, weight no more than 300 kg. The installation is equipped with interlocks and safety devices that eliminate hardening defects and failure of the plasma torch in the event of problems with water and gas supply, as well as in the event of malfunctions of the machine moving the workpiece.

At the production site of TUR-1 LLC (Perm), using UPZA-1, ribbed rollers (steel 50) of the rolling field of the 5000 mill for the Magnitogorsk Iron and Steel Works were hardened with an increase in hardness from 27 HRC to 59 HRC (Fig. 12).

With the help of such an installation, many parts were strengthened at Seversky Pipe Plant OJSC (Polevskoy). Including technological templates (steel 32G2), the service life of which after plasma hardening increased by 40% (Fig. 13). Plasma hardening increased the hardness of the working surface from HB 180 to 50 HRC.

Such installations have found their use in hardening spacer rings for OJSC Uralmashzavod (steel 34ХН1М) with an increase in hardness from 33..35 to 59 HRC, for hardening pulley grooves (steel 45), for CJSC Uralmash Drilling Equipment with an increase in hardness from 27 to 52 HRC, shafts steel 40X with increased hardness from HB 236 to 52 HRC for OJSC "SPETSNEFTEKHIMMASH" (Krasnokamsk), etc.

Among the most notable variants of technological solutions for hardening with an UPZA installation, we should note the hardening of pusher rods of shear presses (made in France) at JSC Pipe Metallurgical Company in Polevskoy (Fig. 14). The length of the rod is more than 9 meters, diameter – 180mm. It was made for emergency replacement from 21ХМФА steel. Plasma hardening succeeded in increasing the hardness of the surface layer from HB 130 to 40 HRC without longitudinal deformation of the rod, and the shear press has continued to operate uninterruptedly for more than two years.

UPZA units were manufactured and supplied to the Poltava Mining and Processing Plant (Komsomolsk, Ukraine), NPO Technogroup LLC (Volgograd), Mechanical Plant (Biysk). Such installations work effectively when hardening flanges of locomotive tires at the Lebedinsky and Kachkanarsky mining and processing plants.

The design of installations for plasma hardening is based on the use of units and blocks of modern serial welding equipment, which ensures small dimensions, mobility, high operational reliability, ease of operation and maintenance.

In 2012, employees of the plasma processes laboratory of the Nizhny Tagil Technological Institute created and successfully tested a universal plasma hardening installation in manual and automatic mode UUPZ-1 (Fig. 15). With the help of this equipment, it became possible to strengthen almost any parts, both with relatively simple geometry and surfaces with a developed profile. An inverter rectifier was developed and manufactured at UrFU as a source of plasma arc. Supply voltage – 380 V, rated operating current – ​​350 A, installation efficiency – 0.9; weight – no more than 40 kg.

The mobility of UUPZ-1 allows hardening to be carried out on-site at the customer’s production site. For example, Uraltekhpromservice LLC (Ekaterinburg) carried out heat treatment of shafts (40X steel) with an increase in hardness from 27 to 62 HRC (Fig. 16). Shaft diameter 170 mm, length 3500 mm.

For JSC SPETSNEFTEKHIMMASH (Krasnokamsk), the splines and journals of the shafts (steel 40X) were hardened from 25 to 52 HRC (Fig. 17).

All of the listed installations satisfy the conditions of industrial operation and meet the environmental and safety requirements for carrying out argon-arc welding work.

The implementation of such installations does not require significant capital expenditures. It is necessary to organize one or more workplaces (depending on the desired volume of implementation), similar to workplaces for argon arc welding. The workplace must be provided with a source and drain of tap water for cooling the plasma torch.

NEWS IT

STATE UNIVERSITY

SEA AND RIVER FLEET NAMED AFTER ADMIRAL S. O. MAKAROV^

2. SP 52-104-2006*. Steel fiber concrete structures. - M.: NIIZhB: OJSC "National Research Center "Construction", 2010. - 68 p.

3. Rabinovich F. N. Composites based on dispersed reinforced concrete. Questions of the theory of design, technology, construction / F. N. Rabinovich. - M.: Publishing house ASV, 2004. - 560 p.

4. SNiP 2.03.01-84*. Concrete and reinforced concrete structures. - M.: NIIZhB Gosstroy USSR, 1989. - 80 p.

5. SNiP 2.03.03-85*. Reinforced cement structures. - M.: NIIZhB Gosstroy USSR, 1986. -

UDC 621.785; 621.791; 621.762 V. A. Korotkov,

The UDGZ-200 installation, developed in 2002, allows you to manually harden something that had not previously been hardened, quickly wore out and became the reason for frequent and expensive repairs. “The deterioration of surface roughness and dimensional distortion during hardening are so insignificant that many parts after it do not require finishing machining, but are immediately sent into operation, which reduces the duration and cost of their production. The plasma hardening layer is many times more wear-resistant than metal in a normalized or bulk state hardening and tempering, which makes the use of plasma hardening highly effective. Plasma hardening with the UDGZ-200 installation is carried out without supplying water to the part, which allows it to be carried out not only in specialized thermal shops, but also at the place of processing and operation of the parts. This, in addition to the fact, The fact that hardening with the UDGZ-200 installation is mastered by welders of the 2nd and 3rd categories simplifies its implementation in production.

Developed in 2002, setting UDGZ-200 allows you to manually temper what had previously not been subject to hardening, wear out quickly and cause frequent and costly repairs. Deterioration of surface roughness and dimensional distortion during hardening so minor that many of the items after her do not needfinish machining, and immediately sent to the operation, "which reduces the duration and cost of production. Layer of plasma hardening surpasses in wear metal in the normalized condition or bulk quenched and tempered, "which makes use of a highly effective plasma hardening. Plasma hardening installation UDGZ-200 is produced "without the water supply is not the item that allows her not only in specialized thermal shops, but also at the place of processing and operation details. This coupled "with the fact that the hardening installation UDGZ- 200 master welder 2-3 discharges facilitates its introduction intoproduction.

Key words: plasma surface hardening, wear resistance.

Key words: plasma surface hardening, wear resistance.

In the modern age of robots and “unmanned” industries, the development of manual technology may seem misguided. However, manual technologies demonstrate survivability due to their versatility. In the world, the bulk of welding (more than 80%) continues to be performed with electrodes or semi-automatic welding machines, that is, manually. By analogy, it was believed (this calculation was justified) that with the development of a manual surface hardening method, the volume of its use would increase and

Dr. Tech. Sciences, Professor, Nizhny Tagil Branch

Ural Federal University

TECHNOLOGY of manual plasma hardening

TECHNOLOGY MANUAL PLASMA HARDENING

Introduction

TWO HUNDRED AND K

state university

MARINE AND RIVER FLEET NAMED AFTER ADMIRAL S. O. MAKAROV

this is due to those products that were previously impossible to harden for one reason or another. These are the contact surfaces of equipment housings and frames, as well as other large-sized parts. Their thermal hardening by known methods is hampered by their large size and weight, as well as poor susceptibility to hardening of some of the steels from which they are made. At the same time, strengthening these surfaces is important in solving problems of increasing the time between overhauls and equipment reliability.

The problem of manual plasma hardening was solved in 2002 at Kompozit LLC, created in 1990 at the Nizhny Tagil branch of UPI (now UrFU). Here we developed the method and installation UDGZ-200 for manual plasma hardening. The installation (Fig. 1, Table 1) is equipped with a burner, the small size of which makes it convenient for manual manipulation and allows one to reach hard-to-reach places, that is, to strengthen, which was previously operated without strengthening and became the reason for frequent and expensive repairs.

Rice. 1. Hardening using the UDGZ-200 installation: on the left - manually, on the right - by robot

Table 1

Characteristics of the UDGZ-200 installation and the plasma hardening process

Hardening process Installation UDGZ-200

Productivity - 25-85 cm2/min Working gas - argon (15 l/min) Hardening depth -0.5-1.5mm Hardness - HRC35-65 (depending on steel grade) Mains voltage - 380 V Power - 10 kW Weight - 20 + 20 kg (power supply and burner cooling unit)

The UDGZ-200 unit is manufactured according to TU 3862-001-47681378-2007. By the end of 2013, more than 50 units were produced. installations that have been supplied to enterprises in Russia, Ukraine, Kazakhstan, and Kyrgyzstan. In 2008, the installation was awarded a silver medal at the Geneva Salon of Inventions and Innovations

In quenching, the welder moves the arc across the surface at a speed that causes the surface under the arc to “sweat” (a state prior to melting). This is no more difficult to control than melting during welding, but it provides the necessary heat for hardening and prevents gross melting of the surface. Work on the installation is mastered by welders of the 2-3rd category, and it can be used in mechanized, automated and robotic (Fig. 1, right) complexes, which makes it suitable for use in modern high-tech industries. The presence of UDGZ-200 units compensates for the lack of traditional equipment for hardening and makes hardening environmentally friendly.

General information about the properties of the hardened layer

The arc leaves on the surface hardened stripes 7-12 mm wide, painted with “tarnish colors”, that is, covered with a thin film of oxides, which do not have a significant effect on the roughness in the range Rz 8-60 (Fig. 2). The depth of the hardened layer is ~ 1 mm, due to which there is no significant deformation of the hardened parts. This, combined with a minimal change in roughness, allows many parts to be sent into operation without labor-intensive finishing machining of the hard hardened layer, which reduces the cost of their production.

Rice. 2. Plasma arc and the hardened strip it leaves behind

Calculations and experiments have established that when quenching massive bodies in modes typical of UDGZ-200, cooling rates exceed critical ones. When hardening the plates, they decrease, but the possibility of incomplete hardening of carbon steels (to hardness ~ HV360) remains for thicknesses > 4 mm. This makes it possible to perform hardening without supplying water to the heating site, which simplifies the organization of workplaces and allows the UDGZ-200 installation to be used at repair sites, at the place of machining and operation of parts, and not only in heat treatment shops. Thanks to this, the range of hardened parts is expanding - something that was previously inaccessible can be hardened.

Rice. 3. Hardness distribution in the plasma hardening layer on steel 40

The typical structure of the hardened layer is similar to the heat affected zone in the base metal of welded joints. A dendritic structure may form at the surface

from its melting; Below there is an area of ​​overheating with enlarged grains; then a fine-grained normalization section; even lower is the section of incomplete recrystallization, followed by the last section - tempering. Thus, the hardness of the hardened layer decreases gradually as it moves away from the surface (Fig. 3), which prevents the formation of spalls.

Wear resistance of plasma hardening layer

The wear resistance of steels with plasma hardening was studied using a friction machine according to the “disc-pad” scheme without lubrication. Disc rotation speed (d 40*10 mm) 425 rpm. There were five test stages of 5 minutes each with a load of 200 N in the first four and a one-and-a-half increase in load to 300 N in the 5th stage, with weighing after each stage to determine wear. At the first stage, the pairs are worn in; stages 2–4 characterize the established wear process. The fifth stage shows the ability of friction pairs to withstand overload; In all cases of plasma hardening, no increase in wear was observed at the fifth stage. Three pairs of samples were tested in each material combination.

Rice. 4. Average wear (g) of disks (D) made of structural steels with different hardness (HB) at stages 2-4 of steady wear. Types of disk hardening:

Norm - normalization, 03 - volumetric hardening with tempering, PZ - plasma hardening

A comparison was made of the wear resistance of discs made of structural steels during friction against a normalized block made of steel 45. From Fig. Figure 4 shows that in the normalized state, the wear of alloy steel 30KhGSA is approximately three times less than that of carbon steel 45. Volumetric hardening and tempering had almost no effect on the wear of steel 30KhGSA. Plasma hardening, compared with the normalized state, significantly reduced the wear of both steels: approximately 10 times for steel 45 and 4 times for steel 30KhGSA.

From the table 2 shows that plasma hardening of rail steel pads reduced their wear by 126 times; at the same time, the unstrengthened wheel steel disk not only did not reduce wear resistance, but also increased it by 2.1 times. A significant increase in wear resistance as a result of plasma hardening is explained by a change in the wear mechanism. Friction surfaces without hardening had the ability to “seize,” that is, to form spot welded joints with protrusions of microroughness, which created an abrasive factor that accelerated wear. The elimination of setting phenomena due to hardening by plasma hardening led to slower wear through the fatigue dispersion mechanism.

table 2

Effect of plasma hardening on wear* of rail steel in friction pairs with wheel steel

Block, rail steel Disc, wheel steel 65G

Condition Wear, g Keys Condition Wear, g Keys

Without hardening 1.507 1.0 Sorbitization 2.125 1.0

With plasma hardening 0.012 126 Sorbitization 1.021 2.1

* Total for 1-4 test cycles.

It was also found that hardened discs made of low-carbon steel 20GL reduce wear compared to the normal state by ~9 times, and mating pads made of the same steel - by 1.8 times. This implies the feasibility of using the UDGZ-200 installation for strengthening the contact surfaces of equipment body parts, which are usually made of low-carbon steels and are not subjected to thermal hardening due to high costs with a minimal strengthening effect.

Rice. 5. Wear of cast iron pads due to friction against steel discs ZOHGSA

Cast iron pads were prepared: VC120, VC60, SCH25, and discs made of ZOHGSA steel (NV 330); the test results are presented in Fig. 5. VCh60 cast iron without plasma hardening immediately suffered wear to a depth of 3 mm, that is, 250 times more than usual. The wear of gray cast iron SCh25 was even greater, so these results are not shown in the graph. The plasma-hardened VCh60 cast iron received the least wear, which turned out to be ~50% less than the wear of VCh120 cast iron. The wear of gray cast iron SCh25 with plasma hardening, although greater than the wear of VCh120 by ~ 80%, is not catastrophic as the wear of SCh25 without plasma hardening. From this we can draw a conclusion about the feasibility of using plasma hardening of bearing housings of large gearboxes made of cast iron and other products.

Examples of practical applications of plasma hardening

The cone bodies of fine and medium crushing crushers (KSMD-2200, Sandvik-7800, FKB-2100, etc.) quickly wear out along the contact zone with replaceable armor. At the Kachkanarsky GOK, up to 25 cones were subject to restoration by surfacing annually. At the end of 2011, they began to harden them by plasma hardening (Fig. 6), thanks to which the need for restoration of worn cones in 2013 decreased to 5 pieces, that is, five times.

Rice. 6. The cone body of the medium crusher, the contact belt of which is strengthened by plasma hardening

Rice. 7. Technological drum with a gear ring strengthened by plasma hardening

The ring gear (40GL) of a large-sized technological drum (Fig. 7), working in mesh with the drive gear (34ХН1М), is an expensive product. The operating time to the maximum wear of the teeth (30%) was: the ring gear - 2 months, the drive gear - one month. Plasma hardening increased the time before wear of the hardened layer 1 mm thick: for the crown - up to 4 months, and for the drive gear - up to 2.5 months. Then, during scheduled preventive maintenance, without dismantling the parts, the teeth were re-hardened using the UDGZ-200 installation. Until the teeth wear out to the limit, hardening is repeated 4 times, which increases the service life of the ring gear to 12-16 months, and the drive gear to 6-8 months, that is, approximately 7 times. Savings from the use of plasma hardening amounted to 38 million rubles. with the effectiveness of investments in plasma hardening of 5 rubles. savings per ruble of costs.

The strands of rope blocks and drums wear out quickly. The small dimensions of the burner of the UDGZ-200 installation allow them to be hardened (Fig. 8). At the Kachkanarsky Mining and Processing Plant, plasma hardening of two turns, most often included in the work, of the rope drums of the “pressure” unit of the EKG-8 mining excavator and tripled their time between repairs; At the same time, an increase in the service life of the ropes was noticed.

Rice. 8. Rope drum (left) and plasma-hardened pulleys

Half of the rails (KR-100) of the crane track were hardened by plasma hardening, and the other half were delivered without hardening. After a year of operation, the wear of non-hardened rails amounted to 2 mm, and the wear of hardened rails was characterized as “attrition.” After another year of operation, the wear of unhardened rails was 4 mm, and the wear of hardened rails reached a measurable value of about 1 mm.

Conclusion

The UDGZ-200 installation, developed in 2002, allows you to manually harden something that had not previously been hardened, quickly wore out and became the reason for frequent and expensive repairs.

The deterioration of surface roughness and dimensional distortion during hardening are so insignificant that many parts do not require finishing machining after hardening, but are immediately sent into operation, which reduces the duration and cost of their production.

The plasma hardening layer is many times more wear-resistant than metal in a normalized or volumetric hardening and tempering state, which makes the use of plasma hardening highly effective.

Plasma hardening with the UDGZ-200 installation is carried out without supplying water to the part, which allows it to be carried out not only in specialized thermal shops, but also at the place of processing and operation of the parts. This, combined with the fact that hardening with the UDGZ-200 installation is mastered by welders of the 2nd-3rd category, simplifies its implementation in production.

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4. Berdnikov A. A. Hardening of cast iron rolls by plasma hardening / A. A. Berdnikov, V. S. Demin, E. L. Serebryakova [etc.] // Steel. - 1995. - No. 1. - P. 56-59.

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6. Orlov P.I. Fundamentals of design: reference and method. Manual: in 2 books. / P. I. Orlov; edited by P. N. Uchaeva. - M.: Mechanical Engineering, 1988. - Book. 1. - 560 s.

7. Korotkov V. A. Investigations into plasma quenching / V. A. Korotkov, A. V. Shekurov // Welding International. - 2008. - Vol. 22, no. 7.

8. Korotkov V. A. Surfacing of plungers for high-pressure vessels / V. A. Korotkov, S. P. Anan’ev,

A. V. Shekurov II Welding International. - 2013. - T. 27, No. 5.

9. Theory of welding processes / ed. V.M. Uneven. - M.: Publishing house of MSTU im. N. E. Bauman, 2007.

In the hardening zone from the solid phase, the hardened layer has pronounced heterogeneity. Closer to the treated surface, the solid solution is saturated with carbon, which contributes to the formation of an increased amount of austenite. The lower boundary of the residual layer is Fig. 2.21. Distribution of microhardness along the depth of the hardened layer of U10 steel after plasma hardening with different initial states.

There is significantly less austenite, as a result of which maximum hardness is achieved. In addition, a larger amount of undissolved carbides is observed at the lower boundary of the layer.

The initial state of the steel is of great importance for obtaining high hardness. Thus, in steel U8, U10 (preliminarily volume-hardened), a diffusion-free reverse martensitic transformation becomes possible with the inheritance of the austenitic defect structure of martensite with complete inhibition of the effects of softening and recrystallization during plasma heating, Fig. 2.21.

When hardening, without melting, pre-hardened steel (U 10) with the original martensite structure, a third layer appears in the heating zone - a tempering layer (highly dispersed trostite structure). The microhardness of the tempered layer with a trostite structure is 4000-4300 MPa. The formation of a tempering zone at the boundary of the hardened layer with the original structure can play the role of a “soft” layer that can inhibit the development of cracks propagating from the surface.

Alloy tool steels

Steels 9ХФ, 9ХФМ, 9ХС, 9Х5ВФ, 6ХС, 55Х7ВСМФ, 7ХНМА, 8Н1А, ИХ, 13Х, ХВГ with and without surface melting were subjected to plasma hardening.

During hardening without surface melting, a finely dispersed structure of high-carbon martensite and retained austenite appears in the melting zone. Due to the high rate of melting and crystallization, undissolved carbides are observed in the melting zone. The high alloying of martensite in the melting zone provides high microhardness values ​​(12000-14000 MPa). However, in most cases, microcracks appear in the fusion zone, which leads to chipping and spalling of the strengthened layer.

Plasma hardening without melting the surface of alloyed tool steels leads to the formation of a highly inhomogeneous structure in the hardened zone. Due to the incompleteness of the austenitization processes, martensite + undissolved cementite + retained austenite are formed in the strengthened layer. (So ​​in steel 9ХФ and 9ХФМ the amount of retained austenite reaches 35%, and in steel 55Х7ВСМФ up to 40%. The amount of retained austenite decreases along the depth of the hardened zone and already at a depth of 80-100 microns does not exceed its content in this steel during conventional volumetric hardening.

Table 2.8.

Hardness of steel after cold treatment /liquid nitrogen/

To eliminate retained austenite after plasma hardening, cold treatment was carried out. It is known that in alloyed tool steels the end point of the martensitic transformation lies below room temperature. With further cooling of these steels in liquid nitrogen, a martensitic transformation occurs, and the amount of retained austenite noticeably decreases, Table. 2.8.

Studies have shown that cold treatment brings alloy tool steels closer in hardness to hard alloys (HRC E 65-80) and is at the same level

with high-speed tool steels (HRC e 65-69).

However, the use of this

Rice. 2.22. Distribution of microhardness along the depth of the hardened zone on steel after plasma hardening (non-melting)

operations for practical purposes are very difficult and require further research.

When hardening alloy tool steels, an “effect” of maximum hardness is noted at a certain depth from the surface, Fig. 2.22. When hardening alloyed tool steels

Lower cooling rates are required than for carbon ones, because The austenite in them is more than 13Х(1), steel 9ХС(2), steel 9ХФМ(3) is resistant to decay. Alloying elements are capable of forming compounds with carbon (in the form of carbides that retain carbon in poorly soluble compounds) that prevent saturation of austenite. However, the influence of alloying elements on the microhardness of the strengthened layer decreases with increasing carbon content. Steels in which the chromium content exceeds 2-3% are strengthened less effectively due to the strong influence of alloying impurities on the hardening process.

High-speed tool steels

A ready-made tool, which has undergone final heat treatment and is made from various grades of steel R18, R6M5, RUM4K8, is subjected to plasma hardening with and without surface melting.

When hardening with melting of the surface of P18 steel, carbides dissolve in the melting zone, the degree of alloying and the stability of austenite increase. As a consequence, the hardness is lower than the hardness of steel after conventional heat treatment.

Structure and phase composition of steels after plasma hardening and furnace tempering

steel grade	Processing method	Structure	Phase components
			Solid solution									Carbides
			Number of phases,%		Composition by weight, %							Carbide type and quantity%	Total composition by weight, %
			α	γ	C	W	Mo	V	Cr	Co	Fe		C	W	Mo	V	Cr	Co	Fe
Р6М5* R6M5**	Plasma hardening	Martensite + retained austenite + carbide	64. 1	26.8	0.4	3.35	3.1	1.1	4.2	-	87.85	MS-1,1, M 6 S-8.0	4.0	31.5	22.5	7.3	3.4	-	31.3
	Plasma hardening + tempering at 570º C		86.2	-	0.2	2.4	1.6	0.6	4.2	-	91.0	MS-2.6, M 6 S-7, M 2 S-3.1 M 27 S-1.1 M 23 C6, M 7 C 3, M 3 C	6.1	26.3	30.5	9.1	6.5	-	21.5
R9M4K8*	Plasma hardening		62.0	29.0	0.6	5.0	3.0	1.7	3.7	8.9	77.1	MS-1.8, M 6 S-7.2 intermetallic compound	4.4	4.03	19.5	8.1	3.3	2.2	22.2
R9M4K8**	Plasma hardening + tempering at 580º C		86.2	-	0.2	3.2	1.8	1.2	2.9	9.2	81.5	MS-3.8, M 2 S-3.6 M 6 S-7.4 M 27 S 6, M 7 C 3,	5.8	39.4	20.6	8.0	8.0	2.4	15.8
* Martensite + austenite (solid solution) **Tempered martensite (solid solution), retained austenite within the measurement error

When hardening without surface melting, the structure of the hardened layer consists of finely needle-shaped martensite + retained austenite + carbides. The hardness of steel (9500-12300 MPa) exceeds the hardness after conventional heat treatment, Fig. 2.23.

For high-speed steels, it is also possible to use cold treatment after plasma hardening, which increases the hardness of the hardened zone on R6M5 steel from 10,000 to 12,000 MPa, on R18 steel to 11,500 MPa, R9M4K8F to 13,800 MPa.

To increase the hardness of hardened high-speed steel after plasma hardening, tempering can be used, which favorably changes the structure and phase composition of the steel, Table. 2.9.

Rice. 2.23. Microhardness of steel R18 (1), R6M5 (2) and R9M4K8F (3) after plasma hardening without melting

When hardening high-speed steels, hardening without surface melting is most effective. Optimal values ​​of plasma hardening must be selected for each tool made of the same steel. In addition, the increase in the hardness of pre-hardened steel very strongly depends on the duration of plasma heating (the dependence for high-speed steels НV=f(t)) has an extremum), because The duration of heating determines the rate of phase and structural transformations in the strengthened layer.

Stamped tool steels

Surface hardening of Kh17F1 steel was carried out with and without surface melting. We used steel that underwent standard heat treatment (quenching and tempering) and without it, Fig. 2.24. The studies have shown that the presence in the structure of this steel of a larger amount of carbides (15-25% by weight) requires high quenching temperatures to completely dissolve the carbides and obtain high hardness. After traditional hardening, a significant amount (12%) of excess carbides and a large amount of retained austenite remain in the structure

We propose to introduce a progressive method of surface plasma hardening, which increases the resistance and durability of tools, rolling rolls and machine parts for various purposes.

1. The essence of plasma hardening

Low-temperature plasma (5000...50000 0 K) is a concentrated energy source and is increasingly used for surface hardening of machine parts and tools made of various alloys.

The essence of plasma hardening is local heating of a surface area at rates of 10 3 ...10 4 0 C/s to high temperatures, followed by cooling at a supercritical speed due to heat removal into the internal layers of the product. In this case, a specific finely dispersed structure with high performance characteristics is formed.

2. Advantages of plasma hardening

When hardening with concentrated energy sources, due to the specificity of the treatment (high heating and cooling rates), it is possible to obtain a structure and properties of the surface layer that are unattainable with traditional methods of heat treatment.

The main advantages of plasma hardening:

The heating is localized, only the surface layer is strengthened, and the core remains viscous, which leads to increased resistance to wear and fatigue;

High hardness and wear resistance of the surface;

Absence or minimal deformation of hardened parts, which makes it possible to increase the accuracy of their manufacture, reduce the labor intensity of machining and the cost of manufacturing parts;

High productivity - 2 - 9 m 2 /hour;

When hardening without surface melting, subsequent mechanical processing (grinding) is not required, i.e. plasma hardening can be used as a finishing operation;

The presence of compressive stresses and a large amount of retained austenite (steel, cast iron) in the surface layer increases the resistance to the initiation and propagation of cracks;

Hardening is carried out in most cases without forced cooling, i.e. no cooling media or accessories are required.

Like other concentrated energy sources (laser, electron beam), plasma has some new capabilities:

Possibility of replacing scarce high-alloy steels with low-alloy steels, strengthened by plasma hardening;

Possibility of replacing wear-resistant steels with low-carbon steels with a deposited working layer, strengthened by plasma hardening;

Possibility of hardening local areas of the surface (edges of circular knives, cutting and bending dies, saw teeth, electric and chainsaw tires, places for cuffs, bearings, fragments of engravings of stamps and calibers of rolling rolls, etc.);

Possibility of process automation and inclusion of hardening units in flexible production systems and automatic lines.

Compared to laser hardening, plasma hardening has the following advantages:

The cost of equipment of the same power is an order of magnitude lower;

Ease of operation of the installation and its maintenance, i.e. no highly qualified service personnel required;

Mobility of the installation, i.e. the ability to move equipment and quickly install it on any machine that provides the required speed of rotation of the part or movement of the plasma torch;

It is not necessary, as with laser hardening, to apply special coatings to the surface to increase the absorption of laser radiation;

High efficiency, reaching 85%;

Possibility of smooth regulation of mode parameters within a wide range during the hardening process, i.e. changes in the depth, width, structure and properties of the hardened zone.

The disadvantages of plasma hardening include:

Partial tempering in places where hardened strips are applied;

The need to clean the surface of hardened products from various contaminants (scale, rust, oil);

The need for forced cooling of products of small diameter and small thickness to obtain high surface hardness.

3. Plasma hardening equipment and technology

The plasma hardening installation consists of:

Plasmatron (or several plasmatrons);

Power supply;

Oscillator for igniting the plasma arc;

Control panel with instrumentation;

A machine, rotator or manipulator that provides the operating speed of movement of the plasma arc relative to the surface of the product being hardened;

Devices for mounting and adjusting movements of the plasma torch;

Water supply systems for cooling plasmatron components;

Gas supply systems for supplying plasma-forming gas or a mixture of gases.

The main executive body is a plasmatron, in which low-temperature plasma is generated.

Hydrogen, nitrogen, carbon dioxide, air, argon, helium or mixtures thereof are used as plasma-forming gas. In this case, the thermophysical characteristics of the plasma change.

As power sources, you can use specialized welding rectifiers with increased open circuit voltage or conventional welding rectifiers such as VD-306, VDU-504, etc.

The choice of the type and design of the plasma torch, plasma-forming gas and power source are interconnected and depend on the specific task at hand. The power of the installation can be different and ranges from 5 to 50 kW. The installation capacity is up to 2.5 m 2 /hour, depending on the required depth and degree of application of the hardened strips.

Before hardening, the surface of the product is cleaned of contaminants. The hardening process after ignition of the arc occurs when the plasma arc (jet) moves relative to the surface of the product being hardened, which can be carried out in various ways: the part is fixed, the plasma torch moves; the part moves (rotates), the plasma torch is fixed; Both the part and the plasmatron move.

For example, hardening of cylindrical parts is carried out, as a rule, along a helical line, which is achieved by simultaneously rotating the part and moving the plasma torch along the rotation axis. When hardening the entire surface of the product, hardened strips are applied overlapping. To obtain a uniform layer depth and hardness distribution over the surface, the degree of overlap (overlap) is chosen within the range of 45...55%.

The main parameters of the plasma hardening mode, which are established on the basis of studies of prototypes or selected during the hardening process, are:

Linear speed of movement (0.5...6 cm/s);

Plasma arc current (50...1,000 A);

Arc voltage (20...200 V);

Distance from the plasma torch nozzle to the surface of the product (2...100 mm);

4. Some characteristics of the strengthened layer

Geometric characteristics include the depth and width of the plasma impact zone (PLZ). They depend on the parameters of the hardening mode, the thermophysical properties of the alloy being hardened and its structural state.

When plasma hardening with a direct and indirect arc without melting the surface, the depth of the zone can be changed within the range of 0.1...1.8 mm and up to 5 mm, respectively. The width of the zone can be adjusted within 1...40 mm. A larger width of the zone can be obtained by scanning the arc or transverse oscillations of the plasma torch. To obtain greater depth, hardening is carried out with melting, but additional mechanical processing is required, which is not always advisable.

It should be noted that even in modes in which there is no visible melting of the surface of the hardened product, a change in the microrelief occurs: the arithmetic mean deviation of the profile R a decreases, the height of microroughnesses R z decreases, the radius of curvature of the vertices r increases, i.e. Micro-melting of the tops of the irregularities occurs. This has a beneficial effect on changes in roughness parameters and not only increases the hardness of the surface, but also increases its load-bearing capacity and improves the performance properties of hardened products.

5. Materials strengthened by plasma hardening

Plasma hardening from the solid state, i.e. without melting, they mainly process steel, cast iron and titanium alloys. When hardening from a liquid state, i.e. with surface melting, some aluminum and copper alloys are added to these materials.

The hardness values ​​obtained during hardening without melting can vary within wide limits and are in HRC units e:

For low-carbon steels - 32...40;

For medium carbon steels - 52...60;

For cast iron - 50...60.

Hardness and degree of hardening depend primarily on the carbon content. Other factors also have an influence: alloying elements (chemical composition, steel class), the number and shape of graphite inclusions in cast iron, cooling conditions (weight of products, degree of overlap of stripes, presence of cooling media, etc.).

When plasma hardening with melting of steels with a carbon content > 0.4% and cast irons, the hardness is higher. However, it should be noted that in this case the plastic properties deteriorate and the tendency to cracking increases.

According to literary sources and according to the results of research conducted by employees of the Plasma Laboratory of the Nizhny Tagil branch of USTU-UPI (headed by Berdnikov A.A.) and the Problem Laboratory of Metallurgy of Yekaterinburg USTU-UPI (headed by Prof. Filippov M.A.), plasma hardening can be strengthened with high efficiency:

Carbon structural steels (45, Art. 4, etc.);

Structural low-alloy steels (38ХС, 40Х, 30ХГСА, etc.);

Low-carbon steels of varying degrees of alloying after carburization (20, 12ХН3А, 20Х2Н4А, etc.);

Spring steels (50HFA, 65G, etc.);

Die steels (4Kh5FMS, 5KhNM, etc.);

Roller (50, 60ХН, 9Х, 9Х2МФ, 150ХНМ, etc.);

Carbon instrumental (U8, U10, etc.);

Gray cast iron (with flake graphite);

Malleable cast iron (with flake graphite);

High-strength cast irons (with spherical and vermicular graphite);

Etc.

6. Examples of effective use of plasma hardening

A) NTMK, RBC and TsPSHB; 1985-1988, N. Tagil.

Hardening of roller straightening machine parts: bandages, rollers, faceplates made of steels 40Х, 34ХН1М, 5ХНМ. More than 700 parts were hardened.

Technical effect: increase in hardness from HB 340...420 to HRC 54...60; increase in durability by 2.5-3 times. Hardening of overhead crane ramps made of steel 38ХГН. 16 pieces hardened. Technical effect: increase in hardness from HB 360 to HRC 53...55.

b) VSMPO, 1989, Verkhnyaya Salda.

Hardening of large dies with complex engravings for semi-hot stamping of titanium. Material - die steels 5ХНМ, 5ХНВ after volumetric hardening and tempering. After several regrinds, the hardened working layer is removed and a non-heat-treated core remains.

Technical effect: increase in hardness from HB 280...380 to HRC 60...63, increase in resistance by 25...100%.

B) Vysokogorsk Mechanical Plant, 1988-1992, N. Tagil.

Hardening of teltomat guides Æ 100 mm, length 2600 mm, steel 45.

Technical effect: increased hardness from HB 420 to HRC 52...54, minimal drives (0.16...0.22 mm), improved grindability.

Hardening of shafts, axles, bearing seats, edges of flat guides and other parts (14 items) made of low-alloy structural and spring steels.

Hardening of saw bars for ELPI electric saws. Over 1000 pieces hardened, steel 7ХНМ. Technical effect: increase in hardness from HRC 41...43 to HRC 59...61.

An installation for plasma heating of hollow copper tubes for high-performance winding of inductors of various sizes was developed, manufactured and implemented at VSW.

d) UVZ, 1991, N. Tagil.

A plasma hardening installation for parts made of structural alloy steels (4 items) has been introduced.

Technical effect: increase in hardness from HB 280...380 to HRC 50...58.

e) Rezhevsky Mechanical Plant, 1990-1991, Dir.

A plasma hardening installation for cylindrical parts Æ 60...150 mm made of structural low-alloy steels has been introduced.

Technical effect: increase in hardness from HB 240...280 to HRC 50...54.

f) Lysva Metallurgical Plant, 1990...1992, Lysva.

2 plasma hardening installations have been introduced for hardening various parts (6 items) made of structural carbon and low-alloy steels.

Technical effect: minimal leads, increasing hardness from HB 260...380 to HRC 50...56.

g) Serov Metallurgical Plant, 1989-1992, Serov.

Hardening of hot rolling rolls of crimping, roughing and semi-finishing stands for rolling circles 180...200, rhombic and hexagonal rolled stock. Roll material - steel 70L, 150Х2Г2НМ.

Technical effect: increased hardness up to HRC 52...56, increased durability of rolls by 20...80%, reduced tendency to form a coarse mesh.

Hardening of cold rolling rollers for hexagon production. The roll material became 9HF after volumetric hardening and low tempering.

Technical effect: increase in hardness from HRC 54...58 to HRC 61...63, increase in roller life by 15...20%.

h) Kachkanarsky GOK, 1999-2000, Kachkanar.

A stationary installation has been introduced for plasma hardening of tire flanges of diesel locomotives, electric locomotives and traction units. As of 2003, more than 1000 bandages have been hardened.

Technical effect: increase to HRC 50...54, increase in durability by 25% compared to high-frequency hardening and 2.0...2.5 times compared to bandages in the as-delivered condition.

i) Krasnouralsk copper smelter, 1998...2001, Krasnouralsk.

Hardening of large-module drive helical gears for mills. Gear material - steel 40X and 45.

Technical effect: increase in hardness to HRC 52...56 and durability by 2.2-2.8 times.

j) NTMK, crimping, large-section, rail and beam shops 1995...2009, N. Tagil.

Hardening of steel and cast iron rolls for rolling channels, angles, circles, squares, rails, center beams, circles. More than 8,000 rolls weighing from 7 to 34 tons were hardened.

Technical effect: increasing the durability of rolls up to 80%, reducing specific consumption by 25...45% kg/t depending on the stand and the rolled profile. Actual Savings 3 - 9 rub. for 1 rub. costs.

k) NTMK, 2000-2009.

Hardening of roller straightening machine tires made of steel 45, 45 XNM for straightening long rolled products. More than 650 bandages have been hardened.

Technical effect: increase in hardness to HRC 52...56, increase in resistance by 1.6-3.1 times.

m) JSC "Gornozavodsktransport", Gornozavodsk, 2003.

A mobile (portable) installation for plasma hardening of diesel locomotive tire flanges has been introduced.

Technical effect

n) JSC "Karelian Okatysh", Kostomuksha, 2004; JSC "Mikhailovsky GOK", Zheleznogorsk, 2006; OJSC "Lebedinsky GOK", Gubkin, 2006

A stationary installation for plasma hardening of flanges and tires of diesel locomotives based on the KZh-20 machine was introduced.

Technical effect: increase in surface hardness to HRC 50...54, increase in durability by 2.0-2.5 times compared to bandages as delivered.

n) JSC "URALASBEST" (Asbest, Sverdlovsk region 2007) A stationary installation for plasma hardening of flanges and tires of diesel locomotives based on the KZh-20 machine was introduced.

Technical effect: increase in surface hardness to HRC 52...58, increase in durability by 1.8-2.5 times compared to bandages as delivered.

p) OJSC "NTMK" (Nizhny Tagil, 1995-2010) Plasma hardening of hot rolling rolls in OTs-1 (until 1999), in KSC and RBC on an ongoing basis under annual contract agreements.

Technical effect: increased durability, operating time and reduced specific consumption of rolls by 1.2-1.6 times.

Thus, plasma hardening has been introduced at many machine-building, metallurgical enterprises, and mining and processing plants in Russia. Stationary mobile installations for plasma hardening of machine parts and tools on screw-cutting lathes, surfacing lathes, rotary lathes, roll lathes and roll grinders were designed, manufactured and installed. The installations are equipped with plasma torches of our own design for arc hardening of direct and indirect action, with and without arc scanning, including manual plasma torches for hardening of local areas of machine parts and tools.