SE442641B - INSTALLATION FOR THERMAL OR CHEMICAL THERMAL TREATMENT OF THE WORKING METAL - Google Patents

Description

8102556- 10 15 20 25 30 35 1 2 is placed on the stand through an open oven lid, after which the lid is closed and the fan and the heating device are started. Gas flows through the heating device under the influence of the fan and transfers the heat to the charge (charge).

The loading basket with the kit is periodically rotated 180 ° around the vertical axis.

This known furnace does not provide the desired high efficiency, since the treatment in this takes place in batches and the time required for carrying out auxiliary operations for loading and unloading, as well as the heating and cooling time constitute the greater proportion of the process time.

Because this oven is equipped with a turning mechanism, the oven is not closed tightly enough. Nor can oxidation-free curing be carried out directly in this known furnace directly from the temperature for thermal and chemical-thermal treatment.

An electric oven is known (compare, for example, the Soviet inventor's certificate ll1793, which comprises a lined housing, which has the shape of a cone with heating elements and a muffle with a lid, and electromagnets arranged between the housing and the muffle with pole pieces facing the muffle. The electromagnets are arranged on the conical side surface of the muffle.

Workpieces to be treated are loaded by means of a guide screw or a groove through a loading opening in the lid in the lid, where they are held by means of a magnetic field generated by the electromagnets. As the workpieces heat up, they lose their magnetic properties but are retained on the inclined wall by the electromagnets under the influence of the frictional force.

After the workpieces have completely lost their magnetic properties, they slide by gravity downwards along the sloping wall to a hardening tank.

In this known furnace, an angle between the center axes of the electromagnets is determined by the conicity (acute angle of the cone) of the walls of the workroom, which conicity is calculated provided that the workpieces are retained, depending on their weight and shape and not dependent on other physical reasons, for example on conditions to ensure the desired field symmetry, impact on the course of chemical reactions at the interface (phase surface) between gas phase and solid phase, and polymorphic and allopropic transformations in the heat treatment. A device for generating the magnetic field does not ensure the desired concentration of the magnetic flux in the working zone.

A shaft furnace for nitriding workpieces is also known (compare, for example, the Soviet inventor certificate 558967), which comprises a lined housing with heating elements, a muffle with a removable lid and fan, a device for generating a magnetic field and a device for charging. ) and output of workpieces.

In the muffle, a solenoid for generating the magnetic field is freely arranged in such a way that a guaranteed process gap is left between the solenoid and the walls and between the solenoid and the bottom part of the muffle, respectively.

The solenoid is made up of a frame with winding of wire consisting of an alloy containing 20% Cr and 80% Ni and is intended to be fed with electric current by means of a current-supplying means arranged in the furnace housing.

The known oven works as follows: You insert the workpieces into the muffle, close it with the lid and let an ammonia stream pass through the muffle. The supply voltage is applied across the heating elements and the solenoid individually, so that they can work independently of each other.

When alternating current is used to generate the magnetic field, the diamagnetic effect resulting from the set of workpieces will weaken the effect of the external magnetic field.

In this known furnace, the parameters of the electromagnetic field 8102556-1 10 15 20 25 30 35 4 are difficult to control, the solenoid for generating the magnetic field having a low efficiency. The solenoid in this known furnace is more of an additional heating element than a generator for generating electromagnetic fields, since it is made of an alloy containing 20% Cr and 80% Ni. The energy supplied to the solenoid is converted practically entirely into heat and not into energy in the electromagnetic field; The fact that such a generator for generating an electromagnetic field has a low efficiency also results from considerable magnetic flux extinction, which results in instability of the parameters of the electromagnetic field in the muffle working space. In order to be able to generate a uniform field, the ratio between the diameter of the solenoid and its length must be 1:10, which cannot be ensured due to the geometric dimensions and shape of the furnace muffle.

This known furnace thus requires high energy consumption for generating a magnetic field strength of not only a few tens of kA / m but also a few tens of A / m.

In this oven, the effect of the solenoid on the constant holding accuracy of the predetermined temperature is not completely eliminated either, which - in combination with all the disadvantages - makes it impossible to change the process parameters and the quality of the diffusion layers impossible.

The efficiency of the known furnace is considerably reduced by the fact that the furnace operates batchwise and by the fact that the loading and unloading of workpieces is very time-consuming and requires special devices and mechanisms.

In addition, it is difficult to uniformly heat the batch of workpieces and to ensure circulation of the saturating medium. The magnetic field performs limited functions and is only intended to affect the saturation speed.

It should be noted that the solenoid is exposed to the effect of the process temperature and that the aggressive medium, which reduces its service life. Because the power supply means for supplying electricity to the high temperature zone must be electrically insulated and tightly closed, the functional safety of the equipment and the personal safety are reduced. Also, in this oven, oxidation-free hard workpieces can not be immediately lowered from the nitriding temperature.

The main object of the present invention is to provide such a plant for thermal and chemical-thermal treatment of metal workpieces, which makes it possible to ensure continuous work of the plant, to control the parameters of the magnetic field, to intensify the treatment and to improve the treatment quality of the workpieces. by applying suitable design elements, appropriately selecting their position relative to each other, eliminating the effect of temperature and saturation on the components of the device for generating the magnetic field during processing and eliminating the mutual influence of the heating elements and the magnetic system by the generating field the desired parameters and by the workpieces during the treatment moving in the working zone of the plant at the same time as the devices for loading and dispensing workpieces operate in an adaptive manner.

This is achieved according to the present invention by means of a plant for thermal or chemical-thermal treatment of metal workpieces with a housing (1) comprising a workpiece receiving muffle (2) with heating element (7) and thermal insulation (ll) and a at the muffle (2) arranged device for generating a magnetic field, which plant has devices for loading and discharging workpieces and for supplying and diverting a diffusion gas, wherein - the muffle (2) is made of non-magnetic material, - the device for generating the magnetic field consists of a plurality successively placed closed electromagnet systems, arranged to surround the muffle (2) along its entire length. - that each electromagnet system (14, 15, 16) can be individually switched on and off.

It is suitable that the closed magnet system is made up of electromagnets, which are assembled in pairs into a muffle surrounding cassette, the central axes of the opposite electromagnets in each pair being located on a single straight line, while the central axes of pairs of in the cassette adjacent electromagnets intersect at right angles (ie are perpendicular to each other), and on the other hand a heating element arranged in the muffle in the form of a bifilar spiral.

It is suitable that the discharge device is built up of guides with gripping means arranged therein and with drive device for moving the gripping means.

The arrangement of said structural elements and their suitable mutual position in the plant makes it possible to generate a magnetic field with adjustable strength (of not more than 40 kA / m) by using the closed magnetic field, cooling, heat protection and independent work of the electromagnets. In this case, the magnetic system is not exposed to the action of the aggressive saturation medium.

The electromagnets assembled to a cassette ensure - when switched successively - transport of the workpieces during their processing, stirring and feeding of the workpieces into the curing tank under conditions in which the treated surface of the workpieces is not oxidized. By arranging the heating element in the muffle, you can increase the heating speed of the workpieces and reduce the amount of heat that leaks into the surrounding space. Because the heating element consists of a bifilar spiral, the magnetic field generated in the working space of the muffle by the electromagnets is not distorted.

The plant according to the invention makes it possible to improve the physical and mechanical properties of the treated workpieces and to intensify the chemical-thermal treatment by 1.5-2 times. The invention is described in more detail below with reference to the accompanying drawing, in which Fig. 1 shows that a section through the plant according to the invention for thermal and chemical-thermal treatment of metal workpieces and Fig. 2 shows a section along the line II-II in Fig. 1. The plant according to the invention for thermal and chemical-thermal treatment of metal workpieces comprises a housing 1 (Fig. 1), in which a muffle 2 is arranged, which is tightly connected to a feed container 3 in a device for loading workpieces and with a hardening tank 4 in a device for discharging treated workpieces. The muffle 2 is made of non-magnetic steel. In the muffle 2, in a second quartz tube 5 on a receiving mandrel 6 of ceramic material, a heating element 7 is arranged, which has the shape of a bifilar spiral. The lower end of the quartz tube 5 is tightly closed, while its upper end is inserted through hermetic sealing devices 8 for the housing of the feed container 3 into a cooled unit 9 provided with hermetic sealing devices 10 for supplying the supply voltage. A thermal insulation 11 is arranged around the muffle 2. Outside the thermal insulation 11, electromagnets are arranged, which comprise closed magnetic flow conductors 12, which are separated from each other by means of diamagnetic spacers 13. Between the magnetic flow conductors 12 and the thermal insulation 11, coils 16 are arranged on cores 14 with pole pieces 15.

The hardening tank 4 consists of a container, which by means of a partition wall 17 is divided into two parts, one of which is connected to the muffle 2 and provided with an electromagnet 18, the drawbar 19 of which is arranged to support a separating member 20, which is held by a spring 21. In the second part of the hardening tank 4, guides 22 belonging to a cam member are arranged, which support an electromagnet-controlled gripping member 23, which is connected to a drive device in the form of a hydraulic cylinder 24 for moving the gripping member 23. Perforated partitions 25 and 25, respectively, are arranged in both parts of the curing tank 4. Between the hardening tank 4 and the electrically controlled gripping member 23, a container 27 for treated workpieces provided with a perforated bottom part is arranged in an upper position. A hydraulic pump 28 with an electric drive device 29 is connected by a suction and a pressure pipeline to the curing tank 4 and the hydraulic cylinder 24 respectively. Pipe nozzles 30 and 31 for supply and removal of gases are arranged in the housing of the feed container 3 and the curing tank 4, respectively. The pipe fittings 31 are connected to the atmosphere by an oil lock 32. The feed container 3 is provided with a tightly closable lid 33 and a thermal insulation 34.

Fig. 2 shows a section along the line II-II through the plant according to the invention, where it can be seen that center lines of the opposite coils 16 arranged on one magnetic current conductor 12 lie on a straight line, while center lines of the adjacent pairs of electro magnetic coils 16 are perpendicular to each other.

The system works as follows. A curing liquid is poured into the curing tank 4 (Fig. 1) to a level which lies above the lower end surface of the partition wall 17 a distance which is 1.5-2 times greater than the pressure of the curing liquid column height expressed in mm. The workpieces are loaded into the feed container 3, which is then closed by the lid 33. Gas used as saturation medium is supplied through the nozzle 30 and displaces air from the feed container 3, the muffle 2 and the curing tank 4, discharging it to the atmosphere. through the pipe fittings 31 and the oil lock 32. The supply voltage is then applied across the heating element 7 by means of the tightly closed unit 9. The workpieces are held in the muffle 2 by means of the separating means 20. When the temperature in the muffle 2 reaches 450-500 ° C, the DC voltages generates a magnetic DC field. The magnetic flux occurs between the pole pieces -15 and hits the workpieces present in the muffle 2, which results in these being retained in the field from each electromagnet.

The workpieces are heated in this case by the radiant energy from the heating element 7 and by heat transfer, which reduces the heating time and the power consumption of the heating element 7 by 2-4 times. After the time required to provide a diffusion layer of the desired depth, the electromagnet 18 is activated, which by means of the drawbar 19, by compressing the spring 21, moves the separating means 20 downwards and opens the muffle 2. At the same time the supply voltage is disconnected from the coils 16 on the the lower electromagnet, wherein a portion (a set) of workpieces falls against the partition wall 25 and further into the curing liquid and is collected at the bottom surface of the curing tank 4. The isolating means 20 then returns to the initial position and the supply voltage is applied across the coil 16 of the lower electromagnet, at the same time as the supply voltage is disconnected from the overlying coils 16 of the adjacent electromagnet.

At the same time as the workpieces partially move downwards, they are turned 90 ° in that the center axes of the coils 16 of the adjacent electromagnets are perpendicular to each other. The overhead coils 16 of the adjacent electromagnets are then switched in the same order, which leads to batches (portions) of workpieces being fed from above from the feed container 3 into the curing tank 4. At each switching of the electromagnet coils 16, the workpieces are turned 90 °, of the saturation medium over the workpieces. The electromagnetically controlled gripping member 23 moves in the guides of the cam member by means of the hydraulic cylinder 24, engages the workpieces collected at the bottom surface of the tank 4 and discharges them to the container 27. - .._.___... ._. In order for the oven to be able to operate with the highest possible efficiency, the number of workpieces fed into the container 3 must correspond to the number of workpieces processed per shift.

In the plant according to the invention, the power consumption of the heating element is reduced by 2-3 times, whereby the capacity of the plant increases. By carrying out the curing in an oxidation-free atmosphere immediately after the diffusion saturation, the wear resistance and corrosion resistance of the treated workpieces increase, and the workpieces also have a high surface quality. After nitriding, the hardness of workpieces of unalloyed steels with medium and high carbon content increases by 2-3 times.

Claims (5)

1. 0 15 20 25 30 8102556-1 ll CLAIMS 1. Installation for thermal or chemical-thermal treatment of metal workpieces with a housing (1) comprising a workpiece receiving muffle (2) with heating element (7) and thermal insulation ( ll) and a device arranged at the muffle (2) for generating magnetic fields, which plant has devices for loading and discharging workpieces and for supplying and diverting a diffusion gas, characterized in that - the muffle (2) is made of non-magnetic material , - that the means for generating the magnetic field consists of a plurality of successively placed closed electromagnetic systems, arranged to surround the muffle (2) along its entire length, - that each electromagnetic system (14, 15, 16) is enclosed. individually switchable and disconnectable. Plant according to claim 1, characterized in that one or more magnetic systems (14 - 16) are arranged to be disconnected successively from below in order for the workpieces held in the muffle (2) held in the muffle (2) to slide downwards to the nearest connected magnetic system or to the device placed under the muffle (2) for discharging treated workpieces. k ä n n e - k ä n n e - Plant according to claim 1, characterized in that the closed magnetic system is composed of electromagnets, which are assembled in pairs to a cassette surrounding a muffle (2), the center lines of the opposing electromagnets in each pair lying on a straight line, while the centerlines of adjacent electromagnetic cartridges are perpendicular to each other. Plant according to Claim 1, characterized in that the heating element (7) consists of a bifilar spiral arranged in the muffle (2). Plant according to one of the preceding claims, characterized in that the device for discharging treated workpieces consists of the guide: (22) with a gripping member (23) slidable along them and a drive device for moving the gripping member (23). .