CN108754091B - High-temperature molten salt for rapidly and continuously heating thin strip steel and heating method thereof - Google Patents
High-temperature molten salt for rapidly and continuously heating thin strip steel and heating method thereof Download PDFInfo
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- CN108754091B CN108754091B CN201810611673.9A CN201810611673A CN108754091B CN 108754091 B CN108754091 B CN 108754091B CN 201810611673 A CN201810611673 A CN 201810611673A CN 108754091 B CN108754091 B CN 108754091B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/34—Methods of heating
- C21D1/44—Methods of heating in heat-treatment baths
- C21D1/46—Salt baths
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
Abstract
The invention discloses high-temperature molten salt for rapidly and continuously heating thin strip steel and a heating method thereof, wherein the molten salt consists of barium chloride and any one or more of calcium chloride, potassium chloride or sodium chloride, and the melting point of the molten salt is 600-700 ℃. The composition of the molten salt meets the process temperature, so that the molten salt is in a liquid state. The thin electrical steel strip can be rapidly and uniformly heated to the required process temperature of 900-1200 ℃.
Description
Technical Field
The invention belongs to the technical field of molten salt heating by heat treatment, and particularly relates to high-temperature molten salt for quickly and continuously heating thin strip steel and a heating method thereof.
Background
Modern cold rolled electrical steel production requires annealing. The current annealing is completed by a continuous annealing furnace, and the general annealing is directly heated by gas combustion and then heated by a completely isolated radiant tube. The protective gas (nitrogen-hydrogen mixed gas) for the cold-rolled electrical steel continuous annealing furnace prevents (reduces) the phenomena of surface oxidation, internal oxidation and internal nitridation under the high-temperature condition, and improves the performance of the cold-rolled electrical steel. The protective gas maintains positive pressure to prevent the external gas from entering the furnace.
The heating speed of the continuous annealing of the cold-rolled electrical steel has obvious influence on the performance of a final product, and the product performance can be improved due to the high heating speed. In addition, the oxidation degree also has a remarkable influence on the product performance, which is particularly remarkable on high-grade electrical steel.
In order to increase the heating rate of electrical steel, Japanese patent application laid-open No. 5-59441(JPH0559441A, 1993.03.09) utilizes the electrical resistance of electrical steel strip, and the electrical resistance heats the electrical steel to a temperature required for recrystallization. However, the contact resistance of the connection point of the electric circuit fluctuates greatly due to the movement and the shape of the electrical steel, so that the steel strip cannot be heated uniformly.
Similarly, Japanese patent No. CN02814192.X- "ultrahigh magnetic flux density single-oriented electrical steel sheet having excellent high magnetic field iron loss and coating properties and method for producing the same" of New day iron requires a heating rate of > 100 ℃/s, actually 300 ℃/s or 400 ℃/s, before decarburization annealing in order to obtain oriented silicon steel having high magnetic induction and low iron loss. Japanese patent No. CN 200780014827.6-method for producing grain-oriented electrical steel sheet with high magnetic flux density and CN 200780018947.3-method for producing grain-oriented electrical steel sheet with high magnetic flux density similarly require heating rate, and induction heating is required for rapid heating.
In the heat treatment (lump) of a tool or a die made of high-speed steel or the like, the japanese patent CN200880011115.3 "continuous annealing method and continuous annealing apparatus for a steel strip having a curie point" of new japanese iron employs salt bath heating in order to ensure uniformity (prevention, reduction of deformation), prevention of oxidation, and rapidity of heating. Because the workpieces treated by the heat treatment are small, the volume of the salt bath furnace is small, and the salt is static. Meanwhile, the heating time is long for the dissolution of carbides in the steel. Because the heat treatment temperature of the workpiece is higher, the melting point of the salt bath is also high.
In the continuous heating of the steel strip, the temperature of the steel strip is related to the temperature of the heating furnace and the running speed (time). Therefore, the temperature of the steel strip is influenced by a plurality of factors, the fluctuation is large, and the control of the oxidation state is difficult.
The high-speed heating in the heat treatment process of the electrical steel can improve the magnetic performance, but because the steel has a Curie point (ferromagnetic disappearance temperature), when the heating temperature of the steel strip is improved by adopting induction heating, the efficiency of the induction heating above the Curie point temperature is greatly reduced, and the heating speed is restricted. However, the heating rate of other methods is difficult to increase, and a new high-rate heating method is required.
The salt bath heating of tool steel is performed for small workpieces and is not adaptable to continuous strip heating (melting point, oxidation, heating time, fluidity, etc.). The fluidized bed heating of the tool steel utilizes conductive powder and is electric heating.
At present, a continuous annealing production line is mostly adopted for cold-rolled electrical steel, the thickness of an annealed product is generally 0.50mm, 0.35mm, 0.3mm, 0.25mm, 0.2mm and the like, the width is generally 1000 mm-1250 mm, and the running speed is more than 100 m/min; in order to realize higher heating speed, the front end of a common annealing line heating furnace adopts non-oxidation heating (NOF), and the strip steel is heated by adopting an open fire combustion mode, the heating speed is generally controlled to be dozens of ℃ (20-30 ℃/s), the requirement for further improving the product quality cannot be met, and in addition, the surface oxidation of the strip steel is inevitably caused, and the performance (particularly the iron loss) of the strip steel is reduced; the improved heating mode adopts radiant tube heating (RTF), but the heating speed is obviously reduced (less than or equal to 20 ℃/s). By adopting the two heating methods, thermal stress is often caused due to uneven heating, and the strip shape is influenced.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides high-temperature molten salt for rapidly and continuously heating thin strip steel and a heating method thereof, aiming at improving the heating effect and improving the magnetic property of the electrical steel strip after the molten salt continuous heat treatment line.
In order to achieve the purpose, the invention adopts the technical scheme that:
the high-temperature molten salt for rapidly and continuously heating the thin strip steel comprises barium chloride and any one or more of calcium chloride, potassium chloride or sodium chloride, and the melting point of the molten salt is 600-700 ℃.
The molten salt consists of barium chloride and calcium chloride, and the content of the calcium chloride in each mole of the molten salt is 0.52-0.70 mole.
The content of the calcium chloride is 0.64 mol, and the melting point of the molten salt is 608 ℃.
The molten salt consists of barium chloride and potassium chloride, and the content of the potassium chloride in each mole of the molten salt is 0.55-0.73 mole.
The content of the sodium chloride is 0.555 mol, and the melting point of the molten salt is 649 ℃.
The molten salt consists of barium chloride and sodium chloride, and the content of the sodium chloride in each mole of the molten salt is 0.50-0.70 mole.
The content of the sodium chloride is 0.601 mol, and the melting point of the molten salt is 650 ℃.
The invention also provides a method for heating the thin strip steel by the high-temperature molten salt, which comprises the steps of heating the high-temperature molten salt to the annealing temperature, spraying the high-temperature molten salt onto the strip steel from the strip steel outlet end of the heating furnace, enabling the sprayed heating molten salt to move in the reverse direction with the strip steel, enabling the strip steel to be immersed by the molten salt, and enabling the molten salt to flow out of the strip steel inlet end of the heating furnace and enter a molten pool.
Preferably, a molten salt inlet arranged at the strip steel outlet end of the heating furnace and the molten pool are heated and conveyed through a circulating heating conveying system. The circulation heating conveying system comprises a molten salt conveying pipeline, an inlet and an outlet of the molten salt conveying pipeline are respectively connected with a molten salt inlet and an outlet of the heating furnace, and the system further comprises a molten salt preheater and a molten salt heater group which are sequentially arranged from the inlet end to the outlet end of the molten salt conveying pipeline.
The molten salt heater group comprises a gas heater and an electric heater, wherein the gas heater is used for heating the molten salt preheated by the preheater, and the electric heater is used for further heating the molten salt heated by the gas heater.
The molten salt preheated by the preheater is guided into the molten salt heater group through the molten salt pump to be heated, and then the molten salt is guided into the inlet of the heating furnace from the outlet of the molten salt conveying pipeline.
The molten salt pump is arranged on a conveying pipeline between the preheater and the gas heater.
In the method, the molten salt is heated to 800-1100 ℃ outside the furnace, is conveyed through a pipeline, and is sprayed onto the strip steel at the outlet of the heating furnace in the continuous annealing furnace through a nozzle. The heated molten salt and the strip steel move in the reverse direction, and the strip steel is immersed by the molten salt. The rapid heat exchange is completed by the contact of the electrical steel strip and the molten salt. Meanwhile, the temperature of the strip steel is not higher than the temperature of the molten salt entering the heating furnace of the continuous annealing furnace. And then molten salt flows into a molten pool from a molten salt outlet arranged at the strip steel inlet end of the heating furnace, and liquid salt in the molten pool flows to a molten salt inlet of the strip steel continuous heating furnace after being heated, so that heating and cooling circulation is formed, and continuous heating of the strip steel is completed.
The invention has the beneficial effects that: the salt bath heating is adopted, the liquid salt is in direct contact with the steel strip, the heating speed is high, the temperature and oxidation controllability is high, and the heated steel strip has uniform temperature and small deformation. The liquid salt completely covers the steel plate, the heating is uniform, and the steel plate stress caused by the temperature difference is greatly reduced, so that the deformation of the steel plate is caused. The liquid salt completely covers the strip steel, so that the strip steel is isolated from oxygen in the heating process, and the oxidation is reduced. The method can realize the reduction of rapid heating and oxidation, and improve the magnetic property of the annealed strip steel. Because the surface oxidation is reduced, the annealing temperature can be subsequently increased, the iron loss is reduced, and the surface quality of the product is improved.
The composition of the molten salt meets the process temperature, so that the molten salt is in a liquid state. The thin electrical steel strip can be rapidly and uniformly heated to the required process temperature of 900-1200 ℃.
Drawings
The description includes the following figures, the contents shown are respectively:
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic diagram of the structure of the purification device of the present invention.
Labeled as:
1. the device comprises a strip steel, 2, a heating furnace, 3, a soaking furnace, 4, a preheater, 5, a molten salt pump, 6, a gas heater, 7, an electric heater, 8, a nozzle, 9, an inlet pipe, 10, a container, 13 and a vacuum device.
Detailed Description
The following detailed description of the embodiments of the present invention will be given with reference to the accompanying drawings for a purpose of helping those skilled in the art to more fully, accurately and deeply understand the concept and technical solution of the present invention and to facilitate its implementation.
Electrical steel strips are manufactured by smelting, continuous casting, hot rolling, and then acid pickling and cold rolling to the thickness and width of the finished product, and annealing is required to obtain the required properties. The invention provides a molten salt of liquid in a wide temperature range, and the magnetic property of electrical steel after the molten salt is subjected to continuous heat treatment. The molten salt is described in detail below:
a high-temperature fused salt for quickly and continuously heating thin strip steel is composed of barium chloride and one or more of calcium chloride, potassium chloride and sodium chloride, and has a melting point of 600-700 ℃. The high-temperature molten salt can be stable at high temperature (above 1000 ℃), the high-temperature heating effect is good, and the magnetic property of the electrical steel after the molten salt is subjected to continuous heat treatment line is improved.
As a preferred high-temperature molten salt, the molten salt is composed of barium chloride and calcium chloride, and the content of the calcium chloride in each mole of the molten salt is 0.52-0.70 mole. The molten salt with the proportion can meet the requirements that the surface temperature of a steel strip entering a heating furnace rises and surface crystals can be rapidly melted. The calcium chloride content is preferably 0.64 mole and the melting point of the molten salt is 608 ℃.
As a second preferred high temperature molten salt, the molten salt is composed of barium chloride and potassium chloride, and the potassium chloride content is 0.55-0.73 mol per mol of molten salt. The molten salt with the proportion can meet the requirements that the surface temperature of a steel strip entering a heating furnace rises and surface crystals can be rapidly melted. The molten salt with the proportion can meet the requirements that the surface temperature of a steel strip entering a heating furnace rises and surface crystals can be rapidly melted. The content of sodium chloride is preferably 0.555 mole, and the melting point of the molten salt is 649 ℃.
As a third preferred high temperature molten salt, the molten salt is composed of barium chloride and sodium chloride, and the content of the sodium chloride in each mole of the molten salt is 0.50-0.70 mole. The molten salt with the proportion can meet the requirements that the surface temperature of a steel strip entering a heating furnace rises and surface crystals can be rapidly melted. The molten salt with the proportion can meet the requirements that the surface temperature of a steel strip entering a heating furnace rises and surface crystals can be rapidly melted. The content of sodium chloride is preferably 0.601 mol, and the melting point of the molten salt is 650 ℃.
The invention also provides a method for heating the thin strip steel by the high-temperature molten salt, which comprises the steps of heating the high-temperature molten salt to the annealing temperature, spraying the high-temperature molten salt onto the strip steel from the strip steel outlet end of the heating furnace, enabling the sprayed heating molten salt to move in the reverse direction with the strip steel, immersing the strip steel by the molten salt, and enabling the molten salt to flow out of the strip steel inlet end of the heating furnace and enter a molten pool.
Preferably, a molten salt inlet arranged at the strip steel outlet end of the heating furnace and the molten pool are heated and conveyed through a circulating heating conveying system. As shown in fig. 1, the circulation heating conveying system comprises a molten salt conveying pipeline, a molten salt preheater 4 and a molten salt heater group which are sequentially arranged from the inlet end to the outlet end of the molten salt conveying pipeline, an inlet and an outlet of the molten salt conveying pipeline are respectively connected with a molten salt inlet and an outlet of a heating furnace 2, high-temperature liquid molten salt is filled in the heating furnace, an annealed electrical steel strip is completely covered by the molten salt in the heating furnace, and the heated electrical steel strip is uniformly heated (easily controlled by a plate shape) and has a very high heating speed due to good heat conductivity of. The molten salt preheated by the preheater is guided into the molten salt heater group through the molten salt pump 5 to be heated, and then is guided into the inlet of the heating furnace from the outlet of the molten salt conveying pipeline.
The molten salt heater group comprises a gas heater 6 for heating the molten salt preheated by the preheater 4 and an electric heater 7 for further heating the molten salt heated by the gas heater 6. Preferably, the molten salt pump is arranged on a conveying pipeline between the preheater and the gas heater.
The molten salt is matched with the heating process to heat the salt bath, so that the heating speed is high, the temperature is uniform, and the steel strip is prevented from being oxidized. The salt bath heating result of the molten salt is adopted, so that the iron loss of the product subjected to continuous annealing is reduced, the magnetic induction is high, and the surface quality is improved. Specifically, after the molten salt in the heating furnace 2 is preheated by the preheater 4 (the waste gas discharged by the heating furnace is adopted, the molten salt flowing through the heat exchanger is heated for the first time by the heat exchanger to improve the energy utilization efficiency, the heating temperature is relatively low), the molten salt is sent to the gas heater 6 by the molten salt pump 5 to be heated (coal gas and natural gas can be used as combustion media to be combusted in the heat exchanger, the process that the molten salt passes through the external loop of the heat exchanger is indirectly heated by heat conduction, the heating temperature is close to the temperature required by the process), then the molten salt is directly heated by the electric heater 7 to accurately raise the temperature of the molten salt to the annealing process temperature of the electrical steel thin strip, and the molten salt is conveyed to, and the molten salt is sprayed on the steel strip (the steel strip is ensured to accurately reach the process temperature when being led out from the heating furnace, the reverse flow of the steel strip and the molten salt in the heating furnace is accelerated, and the preheating and heating effects of the steel strip in the heating furnace are improved). The molten salt flows in a reverse direction to the strip inlet. The strip is heated during operation, while the molten salt is cooled. And cold molten salt is sent into the preheater from a molten salt outlet arranged at the strip steel inlet end, the heating process is circulated, the heating circulation of the molten salt is completed, and continuous and rapid heating of the continuous strip steel is realized.
By adopting the method, the cold-rolled thin electrical strip steel 1 passes through the continuous annealing furnace, because the heating furnace is filled with high-temperature molten salt, the steel strip is quickly preheated by the molten salt in the heating furnace 2 and is heated to the annealing process temperature, then the steel strip is annealed in the soaking furnace 3 in a heat preservation way, and the annealed steel strip leaves the annealing furnace to complete the subsequent process. In the continuous annealing furnace, the heating furnace 2 and the soaking furnace 3 are isolated and connected through a furnace throat, high-temperature airtight protection is performed in the furnace throat, the molten salt of the steel strip can be blown off, and the surface of the steel strip is ensured to have no molten salt when entering the annealing furnace. In the heating furnace, the flow direction of the molten salt is opposite to the movement direction of the steel strip, the annealed electrical steel strip is completely covered by the salt bath of the heating furnace, and the steel strip is heated by transferring heat to the low-temperature steel strip by means of the high-temperature molten salt, so that the temperature of the steel strip is quickly raised to the annealing process temperature; because the thermal conductivity of the molten salt is good, the heated electrical steel strip is heated uniformly (the shape of the strip is easy to control), and the heating speed is very high.
As shown in fig. 2, in order to remove volatile substances such as moisture in the molten salt, maintain the non-oxidizing property of the molten salt, and substantially prevent the oxidation of the electrical steel strip when the electrical steel strip is heated, it is preferable to provide a purification apparatus, a purification apparatus vessel 10, and a vacuum apparatus 13 for evacuating the interior of the vessel 10 in the above circulation heating and conveying system, wherein an inlet of the vessel 10 is connected to a molten salt outlet of the heating furnace 2 through an inlet pipe 9, and an outlet of the vessel 10 is connected to a molten salt heating line through an outlet pipe.
By adopting the purification device, the molten salt after the steel strip is heated in the electrical steel continuous annealing furnace is discharged into the container 10 through the introducing pipe 9, volatile substances such as water and the like in the molten salt are discharged under the vacuum maintaining condition, and the purity of the molten salt discharged from the molten salt discharge port is maintained. The vacuum tube interface on the container 10 is connected to a vacuum device via a vacuum tube. The molten salt after vacuum purification is discharged from the discharge port. Then the steel strip enters a molten salt heating circulation system to be heated and then is sent into a heating furnace to heat the steel strip. The vacuum device can be realized by adopting the existing vacuum equipment, such as a vacuum suction filter and the like. The discharge port of the container is preferably provided with a filter structure to prevent the molten salt from being discharged through the vacuum tube.
Preferably, the inlet duct 9 is tangential to the vessel wall. Or the introducing pipe is obliquely connected with the container wall, and the inclination angle is 0-5 degrees. The fused salt entering the container rotates on the wall of the container and then slowly falls down, so that the time of exposing the fused salt in vacuum is increased, and the purity of the fused salt is improved.
Specific preferable examples of using the above molten salt are as follows:
the chemical components are as follows: 0.0025% of C, 3.13% of Si, 0.20% of Mn, 0.0008% of S, 1.05% of Al, 0.0020% of N, 0.01% of Sn and the balance of Fe and inevitable impurities, heating a 0.50mm electrical steel strip, then carrying out cooling and coating after the steel strip is kept warm for a period of time in a soaking section, and obtaining a final product.
Example 1
Composition of salt heated in salt bath of molten salt is BaCl2And CaCl21 mol of molten salt of CaCl2Molar content of 0.60, BaCl2The molar content was 0.40. Mixed BaCl2And CaCl2Heated to 1050 ℃ outside the furnace to obtain a homogeneous salt solution. The 1050 ℃ salt solution is sprayed onto the electrical steel strip required to be heated from the outlet of the electrical steel continuous heating furnace, so that the steel strip is heated to 1050 ℃, and then flows into a molten pool, the molten salt flows to the inlet of the heating section of the electrical steel continuous heating furnace after being heated by an outer pipeline, the temperature of the molten salt is reduced and the temperature of the steel strip is increased through reverse flow, and then the molten salt is discharged outside the furnace and is heated to form heating and cooling circulation.
The melting point of the molten salt is 620 ℃ because of its high melting point. The strip steel entering the annealing furnace is cooled to cause salt crystallization on the surface of the strip steel, but the surface crystallization can be rapidly melted along with the increase of the surface temperature of the strip steel. Liquid molten salts enable high heating rates to be achieved.
The temperature setting of the product temperature equalization section is consistent with the temperature of the molten salt and is 1050 ℃, and the product P is1.0/502.25W/kg, magnetic induction B50Is 1.681T.
Example 2
Composition of salt heated in salt bath of molten salt is BaCl2And KCl, 1 mol of molten salt, the KCl mol content is 0.70, BaCl2The molar content was 0.30. Mixed BaCl2And KCl was heated to 1050 ℃ outside the furnace to obtain a homogeneous salt solution. 1050 ℃ saline solution is sprayed onto the electrical steel strip required to be heated from an outlet of a heating section of the electrical steel continuous heating furnace to heat the steel strip to 1050 ℃, then the steel strip flows into a molten pool, molten salt flows to an inlet of the heating section of the electrical steel continuous heating furnace after being heated through an outer pipeline, the temperature of the molten salt is reduced through reverse flow, the temperature of the steel strip is increased, and then the molten salt is discharged outside the furnace to be heated to form heating and cooling circulation.
The melting point of the molten salt is 660 ℃ due to its high melting point. The strip steel entering the annealing furnace is cooled to cause salt crystallization on the surface of the strip steel, but the surface crystallization can be rapidly melted along with the increase of the surface temperature of the strip steel. Liquid molten salts enable high heating rates to be achieved.
The temperature setting of the product temperature equalization section is consistent with the temperature of the molten salt and is 1050 ℃, and the product P is1.0/502.27W/kg, magnetic induction B50Is 1.683T.
Example 3
Composition of salt heated in salt bath of molten salt is BaCl2And NaCl, 1 mol of molten salt, the mol content of NaCl is 0.60, and BaCl2The molar content was 0.40. Mixed BaCl2And NaCl was heated to 1050 ℃ outside the furnace to obtain a homogeneous salt solution. 1050 ℃ saline solution is sprayed onto the electrical steel strip required to be heated from an outlet of a heating section of the electrical steel continuous heating furnace to heat the steel strip to 1050 ℃, then the steel strip flows into a molten pool, molten salt flows to an inlet of the heating section of the electrical steel continuous heating furnace after being heated through an outer pipeline, the temperature of the molten salt is reduced through reverse flow, the temperature of the steel strip is increased, and then the molten salt is discharged outside the furnace to be heated to form heating and cooling circulation.
The melting point of the molten salt is 600 ℃ because of its high melting point. The strip steel entering the annealing furnace is cooled to cause salt crystallization on the surface of the strip steel, but the surface crystallization can be rapidly melted along with the increase of the surface temperature of the strip steel. Liquid molten salts enable high heating rates to be achieved.
The temperature setting of the product temperature equalization section is consistent with the temperature of the molten salt and is 1050 ℃, and the product P is1.0/502.23W/kg, magnetic induction B50Is 1.679T.
Comparative example 1
Heating the strip steel to 1050 ℃ by adopting a Radiant Tube (RTF), then entering a temperature equalizing section, setting the temperature of the temperature equalizing section to 1050 ℃, and cooling and coating after preserving the heat for a period of time to obtain a final product.
The temperature setting of the product temperature equalization section is consistent with the temperature of the molten salt and is 1050 ℃, and the product P is1.0/502.36W/kg, magnetic induction B50Is 1.657T.
The invention is described above with reference to the accompanying drawings. It is to be understood that the specific implementations of the invention are not limited in this respect. Various insubstantial improvements are made by adopting the method conception and the technical scheme of the invention; the present invention is not limited to the above embodiments, and can be modified in various ways.
Claims (7)
1. A method for heating thin strip steel by high-temperature molten salt is characterized in that the molten salt is composed of barium chloride and any one or more of calcium chloride, potassium chloride or sodium chloride, the melting point of the molten salt is 600-700 ℃, the method is that the high-temperature molten salt is heated to the annealing temperature, then the high-temperature molten salt is sprayed onto the strip steel from the strip steel outlet end of a heating furnace, then the sprayed heating molten salt moves in the reverse direction with the strip steel, the strip steel is immersed by the molten salt, and finally the molten salt flows out of the strip steel inlet end of the heating furnace and enters a molten pool; a molten salt inlet arranged at the strip steel outlet end of the heating furnace and a molten pool are heated and conveyed through a circulating heating conveying system; the circulation heating conveying system comprises a molten salt conveying pipeline, a molten salt preheater and a molten salt heater group which are sequentially arranged from the inlet end to the outlet end of the molten salt conveying pipeline, an inlet and an outlet of the molten salt conveying pipeline are respectively connected with a molten salt inlet and an outlet of the heating furnace, a purifying device is arranged in the circulation heating conveying system, the purifying device comprises a container and a vacuum device used for vacuumizing the inside of the container, an inlet of the container is connected with a molten salt outlet of the heating furnace through an inlet pipe, and a discharge port of the container is connected with the molten salt heating pipeline through a discharge pipe.
2. A method of high temperature molten salt heating thin strip steel as claimed in claim 1, wherein the molten salt is composed of barium chloride and calcium chloride, and the content of calcium chloride is 0.52-0.70 mol per mol of molten salt.
3. A method of high temperature molten salt heating thin strip steel as claimed in claim 2 where the calcium chloride is present in an amount of 0.64 mole per mole of molten salt and the molten salt has a melting point of 608 ℃.
4. A method of high temperature molten salt heating thin strip steel as claimed in claim 1 where the molten salt is comprised of barium chloride and potassium chloride, the potassium chloride being present in an amount of 0.55-0.73 mole per mole of molten salt.
5. A method of high temperature molten salt heating thin strip steel as claimed in claim 4 where the potassium chloride is present in an amount of 0.555 mole per mole of molten salt and the molten salt has a melting point of 649 ℃.
6. A method of high temperature molten salt heating thin strip steel as claimed in claim 1, wherein the molten salt is composed of barium chloride and sodium chloride, and the content of sodium chloride is 0.50-0.70 mole per mole of molten salt.
7. A method of high temperature molten salt heating thin strip steel as claimed in claim 6 where the sodium chloride content is 0.601 moles per mole of molten salt and the melting point of the molten salt is 650 ℃.
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