CN117626373A

CN117626373A - Surface treatment device and method for strip

Info

Publication number: CN117626373A
Application number: CN202311545897.1A
Authority: CN
Inventors: 代锋先; 赵军军; 廖芳芳; 郭瑞·弗拉基米尔; 图尔尹·尤里; 科利斯尼琴科·奥莱格; 格雷纽克·安德里; 佩雷申科·斯维亚托斯拉夫; 斯卡奇科夫·伊戈尔; 塔尔多夫·亚历山大
Original assignee: Barton Welding Institute Of National Academy Of Sciences Of Ukraine; China Ukraine Baton Welding Research Institute Foreign Economic Representative Office; Zhejiang Baton Welding Technology Co ltd; Zhejiang Barton Welding Technology Research Institute
Current assignee: Barton Welding Institute Of National Academy Of Sciences Of Ukraine; China Ukraine Baton Welding Research Institute Foreign Economic Representative Office; Zhejiang Baton Welding Technology Co ltd; Zhejiang Barton Welding Technology Research Institute
Priority date: 2023-11-20
Filing date: 2023-11-20
Publication date: 2024-03-01

Abstract

The invention relates to a surface treatment device and method of a strip, comprising a sealed box body, a plurality of supporting rollers for conveying the strip and a pretreatment device for cleaning the surface of the strip; the two sides of the sealed box body are provided with a strip outlet and a strip inlet for the strip to pass through; the pretreatment device comprises a plurality of heaters with electrolyte jet flow; the invention has simple structure, and the belt supporting roller, the heater and the electromagnetic vibration exciter are arranged; the electric energy utilization rate is improved; the nozzle on the heater is made into a truncated cone shape, and the electrolyte jet is limited by the dielectric wall; the anode in the heater is made in the form of an electrically conductive plate with an area at least 10 times the cross section of the nozzle ensuring the hydrodynamic transfer of positive ions to the strip surface and the recombination of negative ions on the anode surface.

Description

Surface treatment device and method for strip

Technical Field

The invention relates to the technical field of surface engineering, in particular to a surface treatment device and method for a strip.

Background

Patent [1] is known: (A. S. No.1615241A1 USSR, MKI5C 25F 7/00.1989, publication No. 07/05. Publication No. 47) according to this method, an anodized elongated product is pulled through a cathodically polarized electrode and a vapor layer is formed around the anodized product. During pulling along the length of the product, two or more plasma treated (vaporized) regions are formed in the region of the vapor layer.

The disadvantage of this method is that during electrolysis, oxygen released at the product surface oxidizes the product surface and at the same time corrodes the grain boundaries. This method cannot remove scale formed on the surface of the product during the hot rolling.

The device comprises an electrolyte tank, input and output connections and is equipped with a steam outlet channel. The steam outlet channel is provided with a through-hole frame and is coaxial with the longitudinal axis. The steam outlet channel is made of two or more conical funnels, which are arranged in sequence along the channel for pulling the work piece and are connected to each other by a large diameter through-hole frame.

The steam outlet is spirally arranged and can rotate around the longitudinal axis.

The device is designed for electrochemical polishing of wires, and a rotary funnel is adopted. The rotating funnel creates additional electrolyte mixing and thus increases the resistance, thereby increasing the temperature of the electrolyte and the energy intensity of the surface treatment.

Patent [2] is known: (a method and apparatus for cleaning a part with a plasma jet directed at the surface of the part, no.4.555 612USA,1985.MKI4V23K 9/00. Foreign. 1986) which generates a negative voltage on the surface of the part to maintain a cathodic current between the part and the equipment electrode. The disadvantage of this method is that the formation of a constant plasma jet does not allow to obtain a high energy density, which at high current densities in the plasma jet can lead to overheating of the surface, generating overheated steam at the overheated surface. The heated surface after plasma treatment is cooled by reducing the current density, but is easily oxidized by overheated water vapor.

To implement the method, a device is added which periodically converts the cathodic current from an initial value required to clean the part to a second, lower value current having the same direction and accelerates the movement of the plasma jet over the surface of the part. When the current value changes, it does not pass through zero. By this means, cleaning of the surface of the part can be achieved, while at the same time reducing surface damage [2].

The current density through the electrolyte depends on the ion number, current intensity and flow rate. In this method and apparatus, the movement of the high-speed electrolyte does not transfer charge, and thus the current density cannot be increased.

Closest to the present invention is the known patent [3]: (A method for cleaning a surface of a metal product, publication No. 7, no. 2055947Russia,MKI6 C25F 1/00.1996, 10/03), which continuously supplies an electrolyte to the surface of the product and generates a potential difference between the product and an electrode. The energy in the steam layer on the surface of the product is increased by switching the micro-arc discharge current in the steam gas layer before the cleaning process transitions to the heating process.

A disadvantage of the known method is that the energy loss when heating the electrolyte is great. This is due to the lower current intensity in the micro-arc discharge region. The method is performed at a relatively low voltage, and the release of energy depends on the velocity of the jet in the electrolyte, which tends to cause uneven surface cleaning and uneven heating, so that the method cannot clean the surface of the part with high quality and uniformity.

Furthermore, the low energy density in the micro-arc does not cause thermo-mechanical activation of the surface, which can be achieved by rapid heating and rapid cooling of the surface in the discharge region.

The gas discharge is mainly concentrated in the convex portions of the smooth strip surface, i.e. the tops of the asperities of the smooth surface, and the remaining portions of the surface, i.e. the pit portions between the asperities, are not actually treated. In addition, the conductivity of the electrolyte depends on the speed of the individual jets in the electrolyte, turbulence, external magnetic fields, and the distribution of the gravitational field in the electrolyte. When using known methods, non-uniformities in these parameters can adversely affect the stability and quality of the strip surface treatment.

In view of the above, improvements are needed.

Disclosure of Invention

The main purpose of this patent is to the problem that exists to prior art, proposes a strip surface treatment device and method that improves stability, production efficiency and clean quality when clean, realizes the thermo-mechanical activation of surface and reduces material and energy consumption cost simultaneously.

In the electrolytic plasma treatment process, it is necessary to reduce the heat loss of the electrolyte by increasing the current intensity in the micro-arc discharge range.

The object of the present invention is to achieve a high quality and uniform cleaning of the strip surface. Secondary pollution caused by splashing of electrolyte on the treated surface is avoided, and the secondary pollution is also an influence factor of high-quality processing.

A second object of the invention is to control the current density and reduce the electrical energy loss in the electrolyte by means of which the jet direction of the electrolyte coincides with the current direction, i.e. the hydrodynamic component of the electrolyte conductivity is achieved (charge transfer by high velocity flow).

The invention also aims at achieving a thermomechanical activation of the strip surface layer, ensured by a high-speed heating and rapid cooling of the strip surface in the region of the action of the electric discharge. The invention also aims at accurately locating the area of the gas discharge. The gas discharge can be generated not only at the tops of the microprotrusions but also at the pits between the microprotrusions.

The main object of the invention is also to ensure uniformity of the speed, turbulence, external magnetic field, gravitational field distribution in the electrolyte, etc. of the individual jets in the electrolyte. Non-uniformity of these parameters can adversely affect the stability and quality of the strip surface treatment.

A surface treatment device for a strip comprises a sealed box body, a plurality of supporting rollers for conveying the strip and a pretreatment device for cleaning the surface of the strip; the two sides of the sealed box body are provided with a strip outlet and a strip inlet for the strip to pass through; the pretreatment device comprises a plurality of heaters with electrolyte jet flow; wherein, a plurality of heaters are arranged at two sides of the strip, and the heaters at the two sides are arranged towards the plane of the strip; a plurality of heaters are assembled in the sealed box body; an electromagnetic vibration exciter is also arranged in the sealing box body, the electromagnetic vibration exciter is fixed above the heater, the sealing box body is provided with an electrolyte discharge port, and an exhaust port for exhausting waste gas generated in the treatment process is arranged at the upper part of the sealing box body.

As a preferable scheme of the invention, the electromagnetic vibration exciter is provided with a strip guide rail, and the strip guide rail is close to the inlet position of the strip.

As a preferred embodiment of the invention, a plurality of heaters are arranged across the strip.

As a preferable mode of the present invention, a passage is formed outside the heater, and the electrolyte enters the heater through the passage.

As a preferred embodiment of the present invention, the heater is mounted with a cable, and the heater is connected to an anode of the power supply through the cable.

As a preferred embodiment of the invention, the outlet of the heater is formed with a gap through which electrolyte switches electrical energy between the anode heater and the cathode surface.

As a preferable mode of the present invention, the heater is a tank heater; the distance between the heater edge and the strip surface is 2-5 mm.

In a preferred embodiment of the present invention, the electrodes in the heater are in a grid shape, and the grid-shaped area is at least 10 times that of the heater groove.

As a preferable scheme of the invention, the mesh anode in the heater is semi-cylindrical, the focal length is positioned at the boundary of the turbulent layer, and the length of the focal length is not less than 30mm.

A method of treating a surface of a strip, comprising the steps of:

step 1, a strip moves between a plurality of heaters of a sealed box body through a supporting roller;

step 2, the slotting nozzle of the heater is opposite to the surface of the strip and is placed at an acute angle with the axis of the moving direction of the strip; continuously supplying an electrolyte to the surface of the strip by a heater, generating a potential difference in the electrolyte between the strip and the grid-like electrodes, the potential difference being sufficient to form a vapor layer on the surface of the strip and converting into micro-arc discharge;

step 3, with continuous supply of electrolyte, the resistance of electrolyte in the gap of the heater outlet increases and energy is released; switching electrical energy between the anode heater and the cathode surface through the gap by the electrolyte; forming a gas layer;

step 4, discharging to break down the gas layer and destroy pollutants on the surface of the strip; reducing the oxidized metal.

As a preferred embodiment of the present invention, in the step 2, the potential difference generated between the cathode and anode surfaces of the strip is 50-100V higher than the potential required for plasma heating; vibration with the frequency of 40-60 Hz and the amplitude of 0.05-0.1 mm is applied to the surface of the treated strip, so that a turbulent layer with high resistance is formed on the surface of the strip by electrolyte, and the electrolyte is supplied by anode jet flow perpendicular to the surface of the cathode strip.

As a preferred embodiment of the present invention, the electrolyte is a water-based alkaline electrolyte, and the consumption of the electrolyte by the heater is such that the temperature at which the electrolyte heats up due to a voltage drop does not exceed 80 ℃.

The beneficial effects of the invention are as follows:

1. the invention has simple structure, and the belt supporting roller, the heater and the electromagnetic vibration exciter are arranged; the electric energy utilization rate is improved; the nozzle on the heater is made into a truncated cone shape, and the electrolyte jet is limited by the dielectric wall; the anode in the heater is made in the form of an electrically conductive plate with an area at least 10 times the cross section of the nozzle ensuring the hydrodynamic transfer of positive ions to the strip surface and the recombination of negative ions on the anode surface.

2. In the device for treating the surface of the strip, the anode surface facing the surface of the strip to be treated is semi-cylindrical, the focal point of the anode surface is positioned on the surface of the strip, and the focal length is not less than 30mm; the electrolyte flow is concentrated on the surface of the strip to ensure concentration of (electrolyte flow) energy on the surface to be treated.

Drawings

FIG. 1 is a cross-sectional view of a surface treatment apparatus for a strip material of the present invention;

FIG. 2 is a plan view of a surface treatment apparatus for a strip material of the present invention;

FIG. 3 is a schematic view of the surface treatment apparatus of the strip of the present invention;

FIG. 4 is a schematic view of the heating system arrangement and the strip two side surface heating temperature fields of the present invention;

FIG. 5 is a schematic illustration of electrolyte jet traces on the surface of the strip of the present invention;

FIG. 6 is a graph of the electric field intensity distribution over the electrolyte jet and the turbulent layer of the strip surface of the present invention;

FIG. 7 is a schematic diagram of a heat loss model in an electrolyte heater of the present invention;

FIG. 8 is a schematic view (a) of the surface of a strip material prior to electrolytic plasma treatment in accordance with the present invention;

FIG. 9 is a schematic view (b) of the surface of the strip material prior to electrolytic plasma treatment in accordance with the present invention;

FIG. 10 is a schematic view (c) of the surface of the strip material prior to electrolytic plasma treatment in accordance with the present invention;

FIG. 11 is a schematic view (d) of the surface of the strip material prior to electrolytic plasma treatment in accordance with the present invention;

FIG. 12 is a graph (a) of the contamination of localized areas of the surface of a strip prior to electrolytic plasma treatment in accordance with the present invention;

FIG. 13 is a graph (b) of the contamination of localized areas of the surface of a strip prior to electrolytic plasma treatment in accordance with the present invention;

FIG. 14 is a graph (c) of the contamination of localized areas of the surface of a strip prior to electrolytic plasma treatment in accordance with the present invention;

FIG. 15 is a graph (d) of the contamination of localized areas of the surface of a strip prior to electrolytic plasma treatment in accordance with the present invention;

reference numerals illustrate: the device comprises a strip 1, a strip guide rail 2, an electromagnetic vibration exciter 3, a heater 4, a channel 5, a cable 6, a gap 7, a sealed box 8, an electrolyte discharge port 9, a strip outlet 10, a strip inlet 11, an exhaust port 12, a pretreatment device 23, a strip supporting roller 25, a first surface heating temperature field 32, a first heating surface 33 of the strip, a second heating surface 34 of the strip, a second surface heating temperature field 36, a first electrolyte laminar flow jet 51, a first anode 53, a second electrolyte laminar flow jet 55 and a second anode 56.

Detailed Description

The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

1-3, wherein FIG. 1 is a cross-sectional view of a surface treatment apparatus for a strip material of the present invention; FIG. 2 is a plan view of a surface treatment apparatus for a strip material of the present invention; FIG. 3 is a schematic view of the surface treatment apparatus of the strip of the present invention;

a surface treatment device for a strip material comprises a sealed box body 8, a plurality of supporting rollers 25 for conveying the strip material 1 and a pretreatment device 23 for cleaning the surface of the strip material 1; the supporting roller 25 is also a roller for keeping the strip 1 in a tensioned state, and a strip outlet 10 and a strip inlet 11 for the strip 1 to pass through are formed on two sides of the sealed box body 8; the pretreatment device 23 comprises a plurality of heaters 4 with electrolyte jets; wherein a plurality of heaters 4 are installed at both sides of the strip material 1, and the heaters 4 at both sides are installed toward the plane of the strip material 1; a plurality of heaters 4 are assembled in the sealed box 8; an electromagnetic vibration exciter 3 is also arranged in the sealing box body 8, the electromagnetic vibration exciter 3 is fixed above the heater 4, and magnetic poles are positioned on two sides of the strip 1 and parallel to a bus of the strip 1.

The sealed box body 8 is provided with an electrolyte discharge port 9, and the upper part of the sealed box body 8 is provided with an exhaust port 12 for discharging waste gas generated in the treatment process; the electromagnetic vibration exciter 3 is provided with a strip guide rail 2, and the strip guide rail 2 is close to the position of the strip inlet 11; a channel 5 is formed at the outer side of the heater 4, electrolyte enters the heater 4 through the channel 5, a cable 6 is arranged on the heater 4, and the heater 4 is connected to an anode of a power supply through the cable 6; the heater 4 and the electromagnetic vibration exciter 3 are both fixed in a sealed box 8.

The invention has simple structure, and the belt supporting roller, the heater and the electromagnetic vibration exciter are arranged; the electric energy utilization rate is improved; the nozzle on the heater is made into a truncated cone shape, and the electrolyte jet is limited by the dielectric wall; the anode in the heater is made in the form of an electrically conductive plate with an area at least 10 times the cross section of the nozzle ensuring the hydrodynamic transfer of positive ions to the strip surface and the recombination of negative ions on the anode surface.

A plurality of heaters 4 positioned at both sides of the strip material 1 are arranged in a crossing manner; the heaters 4 are arranged on two sides of the strip 1, and the heaters 4 are arranged in opposite directions, namely towards the plane of the strip; the heater is rotated to cross the long axes of the grooves, ensure that the temperature fields do not overlap and can form thermoelastic vibrations. The crossing angle is determined by the processing speed and ranges from 120 degrees to 160 degrees; the heaters are placed on both sides of the strip, the distance between the two heaters being sufficient to cool the surface of the strip below the phase transition temperature, which ensures thermal cycling of the thin layer of the surface, thus ensuring uniformity of the layer structure and an increase in its surface energy.

The number of heaters 4 is three or more, and the jet thereof may cover the entire width of the belt.

The outlet of the heater 4 is formed with a gap 7, and the electrolyte switches the electric energy between the anode heater and the cathode surface through the gap 7; in particular, the conductivity of the electrolyte jet in the electrode gap of the device is provided by the electrostatic and dynamic components, and the anode surface ensures the combination of negative ions and the generation of high-density positive ions (particles).

High potential is formed at the interface between the cathode and the turbulent electrolyte layer, and the uniformity of the resistance of the electrolyte layer on the surface of the product is ensured by electromagnetic excitation. Turbulence forms a variable boundary of the electrolyte layer facing the strip, in which layer the electric field strength fluctuates, which is the core of the discharge. The spatial distribution of the product surface discharge follows a statistical law.

Accordingly, the overlapping condition of the cathode light spots under a certain unit area current density and productivity can be predicted.

The effectiveness of the discharge on the impact of the product surface depends on its power. To increase the discharge power, a capacitor is mounted in the circuit at a potential 60-100V higher than the potential required for forming the plasma layer during the process.

The heater 4 is a groove heater; wherein the electrolyte jet is limited by the dielectric wall, and the distance between the edge of the heater 4 and the surface of the strip 1 is 2-5 mm; the electrodes in the heater 4 are in a grid shape, and the grid-shaped area is at least 10 times of that of the heater groove; this ensures efficient transfer of electrical energy to the turbulent electrolyte layer of the sheet surface; the heaters 4 are mounted on both sides of the strip and face each other (i.e. towards the plane of the strip), the heaters being rotated so that the axes of the heater pockets intersect; the crossing angle is determined by the processing speed and ranges from 120 to 160 degrees. Heaters are placed on both sides of the strip material and are spaced apart a distance sufficient to cool the surface of the strip material below the phase transition temperature.

The heater process parameters should be selected so that they are sufficient to heat the surface layer (up to 5 μm) above the phase transition temperature and the distance between the heaters should be sufficient to cool the surface layer below the phase transition temperature.

Hydrogen is adsorbed on the surface of the cathode of the strip, the current intensity on the turbulent electrolyte layer and the hydrogen layer is 200-500 kV/m, and the turbulent electrolyte layer and the hydrogen layer are broken down by discharge, so that surface pollutants are removed and surface iron oxide is reduced.

The two sides of the strip are treated by three or more electrolyte jet flows, and the angle between the jet flow and the bus of the strip is 10-15 degrees.

In order to ensure that the electric field intensity in the turbulent electrolyte layer is the same, the net anode in the heater 4 is semi-cylindrical, the focal length is positioned at the boundary of the turbulent layer, and the length of the focal length is not less than 30mm.

The heater 4 is fixed below a crucible (not shown) containing the liquid metal at a distance that ensures cooling of the strip surface to 400-450 c at a given speed of movement.

In this embodiment, the strip 1 can be pulled in a crucible.

The above features improve process quality and uniformity and reduce strip deformation and warpage.

Cleaning of the strip surface is performed by a tank electrolytic heater with built-in electrodes, and the cleaned strip is pulled through a heater and cooling system and wound. In a tank heater, in which the electrolyte jet is limited by dielectric walls, the electrodes in the heater are made in the form of semi-cylindrical grids, the total area of the holes is not less than 10 times that of the tank of the heater, the heaters are mounted on both sides of the strip so that the tank makes an acute angle with the generatrix of the strip. The distance between the edge of the heater groove and the surface of the strip is 2-3 mm, and the heater is rotated so that the long axis of the heater is parallel to one side of the strip and forms an obtuse angle with the axis of the heater on the other side. Heaters are positioned on either side of the strip at a spacing sufficient to cool the surface of the strip below the transformation temperature.

A method of treating a surface of a strip, comprising the steps of:

step 1, the strip 1 moves between a plurality of heaters 4 of a sealed box 8 through a supporting roller 25;

step 2, the grooving nozzle of the heater 4 is positioned at an acute angle relative to the axis of the moving direction of the strip 1 and relative to the surface of the strip 1; continuously supplying an electrolyte to the surface of the strip 1 by the heater 4, generating a potential difference in the electrolyte between the strip 1 and the grid-like electrodes, the potential difference being sufficient to form a vapor layer on the surface of the strip 1 and to switch micro-arc discharge; the potential difference generated between the cathode and anode surfaces of the strip is 50-100V higher than the potential required by plasma heating; applying vibration with the frequency of 40-60 Hz and the amplitude of 0.05-0.1 mm to the surface of the treated strip, so that electrolyte forms a turbulent layer with high resistance on the surface of the strip, and the electrolyte is supplied by anode jet flow perpendicular to the surface of the cathode strip; in particular, the electrolyte jet is introduced from the anode vertically into the cathode treated surface of the strip by means of a dielectric wall, thereby confining the electrolyte jet. Another feature is that the fixed electromagnetic excitation can cause vibration of the surface of the strip, ensuring that a turbulent electrolyte layer with high electrical resistance can be formed on the surface of the strip.

Step 3, with continuous supply of electrolyte, the resistance of electrolyte in the gap at the outlet of heater 4 increases and energy is released; the electrolyte switches electrical energy between the anode heater and the cathode surface through the gap 7; forming a gas layer;

step 4, the discharge breaks down the gas layer to destroy pollutants on the surface of the strip 1; reducing the oxidized metal.

The electrolyte is a water-based alkaline electrolyte, and the consumption of the electrolyte by the heater is such that the temperature of the electrolyte heated by the voltage drop does not exceed 80 ℃.

Consumable used in the method: basic aqueous solutions, e.g. Na ₂ CO ₃ An aqueous solution; 10-15% of electrolyte; 120kWh/m ² Is provided.

Fig. 2 shows the distance e between the heaters 4 and the distance b from the heater edge to the electromagnetic exciter.

As shown in fig. 4, heaters are provided at both sides of the strip material 1 to heat the first heating surface 33 of the strip material and the second heating surface 34 of the strip material in a cyclic heating manner; the first heating surface 33 of the strip forms a first surface heating temperature field 32; the second heating surface 34 of the strip material forms a second surface heating temperature field 36; on the surface of the strip, the electromagnetic vibration exciter 3 generates high-frequency vibration, and forms a turbulent electrolyte layer on the surface of the strip. Energy is released in the layer, evaporated and heated to the temperature required for plasma formation. The power mode of the heater and the speed of movement of the ribbon can heat a thin layer (up to 100 μm) to the phase transition temperature of the ribbon. Because the heaters are placed at a certain distance, when the strip moves, the heated layer has time to cool 100-200 ℃ and is heated to the phase transition temperature again by the next heater. The temperature of the strip skin is thus subjected to thermal cycles in the phase transition temperature range, the number of cycles being dependent on the number of heaters.

In fig. 5, two heaters 4 are mounted on both sides of the strip at an acute angle to the generatrix of the strip, so that the axes of the outlet grooves intersect to ensure a uniform thermal circulation of the strip surface layer.

As shown in fig. 6, the strip surface is heated by a non-uniform distribution of the electric field strength along the electrolyte jet and the turbulent layer of the strip surface. The first and second electrolyte laminar jets 51 and 55 exiting the channel heater 4 ensure that the losses in current flow from the first and second anodes 53 and 56 to the strip cathode are minimized. The electromagnetic vibration exciter 3 forms a high-resistance layer on the surface of the strip, and voltage drop and electric energy release occur in the layer, so as to form a plasma layer and heat the surface of the strip.

In a tank heater (see fig. 3), the electrolyte jet is limited by dielectric walls made of non-conductive material. The distance between the heater edge and the strip surface is 3-5 mm. The electrodes in the heater are made as flat metal strips with a total area at least ten times the area of the cell.

The projection of the heater pocket onto a sheet of width L has the following characteristic dimensions: projection distance e, intersection angle α, distance b to electromagnetic exciter 3, see fig. 2.

Electrolyte enters the electrolyte heater through a pipe and then through a metal anode tank, where it is directed by a dielectric wall to the strip surface and closes the electrical circuit between the anode and cathode (strip). The voltage change between anode and cathode is plotted as shown in fig. 5. A plasma layer is formed at the interface of the electrolyte-strip surface.

As the strip passes through the bath electrolyte heater, the surface is subjected to plasma treatment and discharge in the plasma, creating a high heating temperature gradient. The uneven expansion (compression) of the ribbon surface breaks the surface brittle films (oxides, nitrides, carbides), and the high temperature of the hydrogen-containing plasma causes the low melting point impurities and films to evaporate rapidly while reducing the iron oxide. The strip heat dissipation and external cooling (electrolyte splash evaporation) achieve temperature equalization.

The distribution of the electrical energy and the formation of the plasma layer can be described on a schematic diagram of a heater comprising a metal anode via with a characteristic dimension Da, as shown in fig. 7. Through these openings, the electrolyte is compressed by the dielectric wall at a distance H to an outlet nozzle of diameter Dk and directed to the surface of the product. The velocity of the electrolyte and the total area of the anode holes are proportional to the nozzle area. The main loss of electrical energy occurs at the cathode surface due to the turbulence of the electrolyte jet.

In order to improve the efficiency of the device, the anode electrode is made of a conductive plate with the thickness of 1-2 mm and is fixed in the device, so that the anode electrode is projected to pass through the cross section of the narrow part of the nozzle, the minimum distance between the anode electrode and the strip is 30-50% of the thickness of the strip, and the distance between the anode surface and the cross section of the narrow part of the nozzle is 30-40 mm; the narrow part of the nozzle is in a groove shape, the long side of the groove faces to the moving direction of the strip, and the area of the narrow part is less than eight to twelve times of the area of the anode.

The strip is treated by means of a planar jet of electrolyte, which makes an angle of 0-45 DEG with the generatrix of the strip and covers the whole width of the strip. With water-based alkaline electrolytes, the tank heater consumes electrolyte and the electrolyte is heated to no more than 80 ℃ due to the voltage drop.

After electrolysis, the hydrogen layers are adsorbed on the cathode surface of the plate, and they are broken down by discharge because the current intensity on the hydrogen layers is 200-500 kV/m.

In order to increase the energy density, in the device for strip surface treatment, the anode surface facing the surface of the strip to be treated is semi-cylindrical, the focal point of the anode surface is positioned on the surface of the strip, and the focal length is not less than 30mm. The electrolyte flow is concentrated on the strip surface by means of dielectric walls in the device to ensure concentration of (electrolyte flow) energy on the surface to be treated.

All of the above important features ensure high conductivity of the electrolyte, provided by the electrostatic and dynamic components and the recombination of negative ions at the anode. A high potential is formed at the interface between the cathode (product) and the perturbation electrolyte layer. Due to the high electric field strength of the electric potential, the vortex layer is penetrated by the discharge. Since turbulence forms a variable boundary of the electrolyte layer facing the strip, fluctuations in the electric field strength are formed within the layer, which is the core of the discharge.

The spatial distribution of the product surface discharge follows a statistical law. Thus, the overlap of the cathode spots at a certain current density and productivity can be predicted. The effectiveness of the discharge on the strip surface depends on the power of the discharge. A capacitor is mounted in the circuit, the discharge power is increased, and the treatment is performed at a potential 60 to 100V higher than the potential required for forming the plasma layer.

The surface treatment device is characterized by having a slot made of a non-conductive material wall, the jet being limited by the non-conductive wall and by a flat anode having a total area at least 10 times the cross-sectional area of the heater nozzle, which ensures an efficient transfer of electrical energy to the strip surface. In order to ensure that the electric field intensity in the layers adjacent to the surface of the strip is the same, anode grids in the heater are semi-cylindrical, a focal point is positioned on the surface of the strip, and the focal length is not less than 30mm.

The potential difference between the surface of the strip and the electrode is 50-100V higher than the voltage required for plasma heating. In addition, the jet of electrolyte is limited by the dielectric wall, and the electrolyte is supplied under hydrostatic pressure perpendicular to the sheet surface by a planar jet.

The hydrogen layer is adsorbed on the surface of the strip material, the current intensity on the turbulent electrolyte layer and the hydrogen layer is 200-500 kV/m, and the turbulent electrolyte layer and the hydrogen layer are broken down by discharge, so that the discharge removes surface pollutants and reduces ferric oxide. The treatment is carried out using a water-based alkaline electrolyte, the consumption of which is determined according to the amount of which it passes through the tank heater, ensuring that the electrolyte heating temperature due to the voltage drop does not exceed 80 ℃.

The interaction of an electric field and a hydrodynamic field in such devices is described in the literature of ostumov g.a. There is a cross-over effect between the electrodes in the electrolyte. On the one hand, the electric field generates volumetric forces of mechanical nature in the fluid medium, i.e. "prime mover", these forces in the fluid dynamic equation being added to inertia, attraction, air pressure and adhesion; on the other hand, the flow of the charged medium having a density ρ generates electric convection.

The total current density in the electrolyte is the sum of the densities of the three individual currents. First, the conduction current or "migration current" -ions move relative to the liquid in which they are contained under the influence of electrostatic forces, independent of their concentration or the movement of the whole liquid. Secondly, the diffusion current, the same ion, diffuses as a concentration gradient of the charge neutral molecule against itself with respect to the surrounding liquid under the action of osmotic pressure, independent of the electric field strength or the movement of the liquid. Finally, convective ions move in the electrolytic solution as if they were "frozen" in neutral liquids, independent of the electric field strength or their concentration gradient.

The linear relationship of three current densities, which are hardly related to each other, can be expressed by the Nernst-Planck relationship:

wherein:

u _i zi (i=numbers 1, 2, 3.) indicates class i departureCharacteristic parameters of the sub-group-mobility and valence;

р _i ＝n _i z _i e,n _i ,j _i -local bulk density distribution of charge, ion concentration and current density caused by class i ions;

e, v-electric field strength and liquid flow velocity;

=kt/e-specific osmotic potential: the specific osmotic potential of the aqueous solution was about 25.9mV at room temperature t=300K (26.85 ℃);

k, e—boltzmann constant and electron charge modulus.

At Na (Na) ₂ CO ₃ Na is formed in the aqueous solution ⁺ ，CO ^- ，OH ^- ，H ⁺ Ions. The negatively charged ions release excess electrons as they pass through the pores of the anode, and the cations are carried away by the hydrodynamic flow of electrolyte and recombine at the cathode surface of the product (see fig. 7).

The ion species are very complex, their interactions with each other, with the electrodes, and with the electrolyte heater insulating wall, but the convective current is much greater than the diffusion and migration currents due to the large charge volume, high electrolyte flow rate, and therefore the diffusion and migration currents can be ignored in the calculation. Only hydrodynamic components ensure sufficient conductivity of the electrolyte and significantly increase the power density of the surface heating (up to 3x10 ³ W/cm ² )。

The conversion of electrical energy into thermal energy occurs primarily at the plasma layer-cathode-of the heated surface of the product. The energy distribution within the heater (see figure 6) can be expressed as,

Q _k ＝U _ak J _ak -Q _p -Q _d ,,

wherein: q (Q) _k -energy for heating the plasma layer and the cathode;

Q _p -energy consumed by evaporating the plasma electrolyte;

Q _d -a plasma layer spokeEnergy is radiated;

J _ak -current through the plasma layer;

U _ak -a potential voltage of the plasma layer.

The plasma layer thickness is small (h=2-3 mm) with respect to the plasma layer length (dk=30-50 mm), so the energy dissipation (Qd) in the form of radiation is negligible. Electrolyte heating is the result of current diffusion and migration. The main convection conduction mechanism occurs in the heater and the main energy is dissipated in the formation of the plasma layer and the treatment of the sheet surface, a steep drop in voltage in the plasma layer being observed (see fig. 6). This explains the low loss of electrolyte heating.

In the plasma layer, energy is transferred into the product in a specific form of unbalanced discharge. The discharge is distributed in a film shape, has low gas temperature and high electron temperature, and is in diffusion connection with the surface of the liquid anode. Under the effect of pressure change at the discharge position, the surface of the liquid electrode performs oscillatory motion. Thus, the size of the gap between the liquid electrode and the cathode surface varies periodically. The electric field strength of the electrolyte itself is not high (about 10V/cm), but the electric field strength in the plasma layer is variable and can reach 1000 to 100000V/cm.

Increasing the voltage (about 240-320V) increases the electric field strength in the plasma layer, which can provide conditions for thermoelectric emission (thermionic emission) and discharge formation. There is a steady glow in the electrode gap. The electric field voltage in the plasma layer is 2-4 orders of magnitude higher than in the electrolyte.

Fig. 6 is an electric field intensity distribution of electrolyte jet and turbulent layer at the plate surface. The high resistance at the gap is provided by the turbulence of the electrolyte, and the drop in electric field strength occurs mainly in the gap. The electric energy is mainly used for treating the surface of the strip material, and the high utilization rate of the electric energy is ensured.

The electrolytic plasma treatment device for the strip material works according to the following procedures: the strip is moved between a set of electrolyte heaters, the heater grooving nozzles being positioned at an acute angle α relative to the strip surface, to the axis of the direction of strip movement. The electrolyte is supplied by a heater which completes the electrical circuit between the anode electrode (placed inside the heater) and the surface of the cathode strip. The resistance of the electrolyte in the gap increases and energy is released. A gas layer, i.e. a heated gas-plasma layer, is formed. The discharge breaks down the gas layer, destroying contaminants on the strip surface. Since the strip surface is connected as a cathode to the circuit, a heated hydrogen layer will form on the strip surface, which heats the surface layer of the strip, reducing the metal oxide.

The following detailed description is provided:

the strip surface is affected by physical and chemical recombination of electric discharge, cyclic heating of the surface layer in a hydrogen medium, pulsating gas pressure. The surface thin layer of the strip material can be circularly heated while the oxide is cleaned and reduced.

In the apparatus for cleaning the surface of a strip (treating the surface of a strip), the angle of the long axis of the heater tank to the direction of movement of the strip is 90 DEG or less.

The anodes in the electrolyte heater consist of semi-cylindrical plates, the cylindrical generatrix of which is placed parallel to the strip surface.

For efficient operation, the actual area of the semi-cylindrical electrode must be at least 10 times higher than the area of the slot. In order to enhance the discharge power in the circuit, a pulse capacitor is installed in parallel with the electrodes.

The device uses consumables such as aqueous alkali solution such as sodium carbonate Na ₂ CO ₃ 10-15% of electrolyte with electric energy up to 120kWh/m ² 。

The quality of the thermal cycle and cleaning of the strip surface is dependent on the energy of the discharge and the discharge exposure time, and can be controlled by the width and rotation angle of the slot heater. The number of contamination spots in the sem at 60 x magnification after cleaning the strip was used as a quality standard.

The device for treating the surface of the strip adopts a device utilizing the electrolytic plasma principle, and is shown in figures 1-7, and the device passes the test verification.

The strip is treated by a planar electrolyte jet which can cover the entire width of the strip. The potential difference (300V) between the strip surface and the near-boundary electrolyte layer ensures the formation of a plasma layer. The plasma layer is adjacent to the treated surface of the strip.

A heated hydrogen layer is formed along the surface of the strip. The current intensity on the electrolyte turbulence layer and the hydrogen layer is 50-150 kv/m. Both layers are broken down by the discharge and contaminants on the strip surface, including contaminants in the surface pits, are removed and the iron oxide is reduced.

Example 1:

the strip is treated with a water-based alkaline electrolyte. Fig. 4 to 7 are schematic views of the apparatus. It consists of a standard strip feed unit and a tank electrolyte heater with built-in electrodes. The verification test is carried out according to the following method: the strip sample was pulled up to a speed of 10-30 m/s between the trough heaters.

The sample was pulled at 10, 20, 30m/s for cleaning, and the strip surface was subjected to 1, 2, 3-X multiple treatments.

The cleaning quality is assessed by the number of macroscopic stains and contaminant particles and the color of the surface.

The heating temperature of the strip surface was assessed by the presence or absence of melting marks and oxidation color.

Fig. 8 and 9 show corrosion layers (iron hydroxide) of different thickness and length with contaminants present before the strip surface treatment. Corrosion may occur in the form of localized spots or spread into a region. Under the corrosion layer, the undulations of the strip surface are not visible. Loose contaminants containing metallic and non-metallic particles, organic films, thin layers of liquids covering the surface of the plate, including areas with corrosion layers. Through these contaminants, undulations of the strip surface can be seen, which are characteristic of different steel grades. Point defects in the form of pits, nonmetallic inclusions, and localized oxide scale inclusions exist on the strip surface. Contaminants (in the form of scale) are also located in the microcavities on the surface of the strip.

Common loose contaminants and corrosion products do not normally mask the surface relief, but rather mask the pits with nonmetallic inclusions (like open pockets) and are clearly visible after the surface is cleaned with alcohol.

When alcohol is used to remove loose contaminants from the surface, it is observed that it has a unique composition of "bosses", surface pits and pits (inclusions) of various sizes.

The surface relief of the 30 steel coupon was quite different from that of Full Hard-027 steel.

After one treatment by an electrolytic plasma heater, the examination result of the surface of the strip shows that: there are no loose contaminants on the surface of the cleaned strip, see fig. 10 and 11. In the area of the surface where there is corrosion, there are defects in the form of typical etch relief. Even if treated twice (electrolytic plasma heater), circular "pits" and inclusions remain on the surface.

Example 2:

the surface of the 30 steel is provided with a heater, and after 3 times of treatment, obvious cleaning effect can be seen. In photographs of uncleaned surfaces, surface relief was hardly visible, and a layer of corrosion (highlighted yellow by the filter) was visible. Clear undulation with corrosion etching traces can be seen on both sides of the cleaned sample surface.

The surface cleaning results of Full Hard-027 steel samples showed that: the surface appears a light grey metallic color. All uneven tops, protruding "plateaus" and recessed boundaries have a melting characteristic, see fig. 11. It can be seen that all the recesses and cavities are not clear, which means that these areas are cleaned. On the cleaned surface, the concave features of "plateau" undulations can be seen. The sharp edges of the "plateau" border have marks of melting.

The thermal mechanism of nonmetallic inclusion failure can be studied by comparing the relief features of the pits (pits) with the pit boundary melting features, see fig. 12-15. Obviously, rapid heating and melting of the cavity boundaries can destroy nonmetallic inclusions. Cavities are formed at the inclusions.

A strong melting of the pit boundary and a trace of heat influence accompanied by peripheral heating of the nonmetallic inclusion can be observed. Within the recessed cavity, the presence of oxides, scale residues and melted metal particles is visible.

Example 3:

after the Full Hard-027 steel sample and the 30 steel sample were treated under the same conditions using the same energy density: the convex boundary and the uneven top of the surface of the Full Hard-027 steel sample are evenly melted; whereas no melting was observed at the surface after 30 steel coupon treatment. Melting of the cavity (pit) boundaries of nonmetallic inclusions was observed.

The electric power calculation was performed with the heater active tank width of 2.0cm and the strip width of 30.5 cm. The total heating area of one side is 61cm ² . The productivity was 20m/min.

Required current: 61×5=305A.

The power consumed to treat the surface of the sheet using an array of heaters is: 305x 300. Apprxeq.100 kVA.

At least 3 rows of heaters are required for thermal cycling and heating. In this case, their power is: 100x3 = 300kVA.

Example 4:

the invention relates to a device for treating the surface of a strip, and cleaning and verification are carried out on pollutants on the surface of the strip by using the device.

The hardening technique and the design characteristics of the device correspond to the above. In example 4, the following parameters were modified:

TABLE 1

The device can simultaneously clean and heat the surface of the strip material. The cleaning process of the strip surface can be combined with the thermal cycling of the strip surface and its heating.

The most efficient cleaning and heating can be achieved by reducing the speed of movement of the strip, or increasing the number of heaters, or increasing the specific power released in the electrolyte plasma layer. The use of high electric field strength, a conductivity kinetic energy component, and a very small electrode gap ensure minimal energy loss.

An arc is used to clean the hydrogen-containing plasma layer to remove contamination of the strip surface by elements in the electrolyte.

The pretreatment device for cleaning the strip before preparing the metal coating or the surface of the strip has the advantages of high productivity, environmental friendliness and the like besides high quality index. The implementation of this technique increases productivity by approximately 3 times compared to hot alkali salt bath cleaning.

The experimental results show that: when the voltage is increased, the plasma thoroughly cleans the strip surface, see items 10 and 11 in Table 1. The heating temperature may be controlled in the range of 200 to 800 c depending on the voltage and the number of heaters.

In addition, the invention belongs to a resource saving technology, and the electric energy utilization rate is as high as 80%.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention; thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Although the reference numerals in the figures are used more herein: the method comprises the following steps of (1) a strip, (2) a strip guide, (3) an electromagnetic vibration exciter, (4) a heater, (5) a channel, (6) a cable, (7) a gap, (8) a sealed box, (9) an electrolyte discharge, (10) a strip outlet, (11) a strip inlet, (12) a vent, (23) a pretreatment device, (25) a carrier roller, (32) a first surface heating temperature field, (32) a first heating surface (33) of the strip, (34) a second heating surface (34) of the strip, (36) a second surface heating temperature field, (51) a first electrolyte laminar flow jet (51), a first anode (53), a second electrolyte laminar flow jet (55), a second anode (56), and the like, but the possibility of using other terms is not excluded. These terms are used merely for convenience in describing and explaining the nature of the invention; they are to be interpreted as any additional limitation that is not inconsistent with the spirit of the present invention.

Claims

1. A surface treatment device for a strip, characterized by: comprises a sealed box body (8), a plurality of supporting rollers (25) for conveying the belt material (1) and a pretreatment device (23) for cleaning the surface of the belt material (1); the two sides of the sealing box body (8) are provided with a strip outlet (10) and a strip inlet (11) for the strip (1) to pass through; the pretreatment device (23) comprises a plurality of heaters (4) with electrolyte jets; wherein a plurality of heaters (4) are arranged at two sides of the strip (1), and the heaters (4) at the two sides are arranged towards the plane of the strip (1); a plurality of heaters (4) are assembled in the sealed box body (8); an electromagnetic vibration exciter (3) is further arranged in the sealing box body (8), the electromagnetic vibration exciter (3) is fixed above the heater (4), the sealing box body (8) is provided with an electrolyte discharge port (9), and an exhaust port (12) for exhausting waste gas generated in the treatment process is arranged on the upper portion of the sealing box body (8).

2. A surface treatment device for a strip according to claim 1, wherein: the electromagnetic vibration exciter (3) is provided with a strip guide rail (2), and the strip guide rail (2) is close to the position of the strip inlet (11).

3. A surface treatment device for a strip according to claim 1, wherein: a plurality of heaters (4) positioned on two sides of the strip (1) are arranged in a crossing way.

4. A surface treatment device for a strip according to claim 1, wherein: a channel (5) is formed on the outer side of the heater (4), and electrolyte enters the heater (4) through the channel (5).

5. A surface treatment device for a strip according to claim 1, wherein: the heater (4) is provided with a cable (6), and the heater (4) is connected to the anode of the power supply through the cable (6).

6. A surface treatment device for a strip according to claim 1, wherein: the heater (4) is a groove type heater; the distance between the edge of the heater (4) and the surface of the strip (1) is 2-5 mm.

7. A strip surface treatment apparatus as defined in claim 6, wherein: the electrodes in the heater (4) are in a grid shape, and the grid-shaped area is at least 10 times that of the heater groove.

8. A method of treating a strip surface, based on the treatment apparatus of any one of claims 1-7; the method is characterized in that: the method comprises the following steps:

step 1, the strip (1) moves among a plurality of heaters (4) of a sealed box body (8) through a supporting belt roller (25);

step 2, the slotting nozzle of the heater (4) is placed at an acute angle relative to the surface of the strip (1) and the axis of the moving direction of the strip (1); continuously supplying an electrolyte to the surface of the strip (1) through a heater (4), generating a potential difference in the electrolyte between the strip (1) and the grid-like electrodes, the potential difference being sufficient to form a vapor layer on the surface of the strip (1) and to switch micro-arc discharge;

step 3, with continuous supply of electrolyte, the resistance of electrolyte in the gap of the outlet of the heater (4) increases and energy is released; switching the electrical energy between the anode heater and the cathode surface by the electrolyte through the gap (7); forming a gas layer;

step 4, discharging to break down the gas layer, and destroying pollutants on the surface of the strip (1); reducing the oxidized metal.

9. A method of treating a strip material according to claim 8, wherein: in the step 2, the potential difference generated between the cathode surface and the anode surface of the strip is 50-100V higher than the potential required by plasma heating; vibration with the frequency of 40-60 Hz and the amplitude of 0.05-0.1 mm is applied to the surface of the treated strip, so that a turbulent layer with high resistance is formed on the surface of the strip by electrolyte, and the electrolyte is supplied by anode jet flow perpendicular to the surface of the cathode strip.

10. A method of treating a strip material according to claim 8, wherein: the electrolyte is a water-based alkaline electrolyte, and the consumption of the electrolyte through the heater is such that the temperature of the electrolyte heated by the voltage drop does not exceed 80 ℃.