High-strength packaging steel strip continuous annealing heat treatment equipment and heat treatment method thereof

Abstract

The invention provides high-strength packaging steel strip continuous annealing heat treatment equipment and a heat treatment method thereof, and relates to the technical field of packaging steel strip heat treatment. The continuous annealing heat treatment equipment for the high-strength packaging steel strip comprises an inlet sealing section, a heating annealing section and an outlet sealing section which are arranged in sequence, a plurality of guide roller groups for conveying the steel strip and medium-frequency transverse and longitudinal magnetic induction heaters are alternately arranged in the heating annealing section; and the medium-frequency transverse and longitudinal magnetic induction heaters can adjust the magnetic field direction to generate a transverse magnetic field of which the magnetic field direction is vertical to the surface of the steel strip or a longitudinal magnetic field of which the magnetic field direction is parallel to the surface of the steel strip. The medium-frequency transverse and longitudinal magnetic induction heater capable of adjusting the magnetic field direction is adopted for conducting heat treatment on the steel strip, the steel strip can be efficiently, rapidly and evenly heated, decarburization and nitriding treatment is achieved in the annealing process of the heating annealing section, the strength and toughness of the surface of the steel strip are improved, and the mechanical property of the high-strength packaging steel strip is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat treatment of packaging steel strips, and specifically to a high-strength packaging steel strip continuous annealing heat treatment device and a heat treatment method thereof. Background Art

[0002] Packaging steel strapping, commonly known as strapping, is a narrow strip packaging material with high tensile strength and a certain elongation. It is divided into three categories according to its mechanical properties: low-strength steel strapping, medium-strength steel strapping and high-strength steel strapping.

[0003] For high-strength packaging steel strips, the selection of raw steel is very important. The appropriate chemical composition and content in the raw steel will help improve the mechanical properties of the packaging steel strips, simplify their manufacturing process, and reduce process costs.

[0004] At present, high-strength steel strips need to be manufactured using low-alloy steel, alloy structural steel or high-quality carbon structural steel. The process flow is generally hot-rolled coil - raw material longitudinal shearing - pickling - cold rolling - tempering treatment - slitting. The equipment and process required for the tempering treatment process are relatively complex and the production cost is high. For example, salt bath furnaces and lead bath furnace heating devices are used. These equipment for preparing high-strength steel strips have the disadvantages of relatively low heating efficiency, uneven heating temperature, easy overburning, low output, etc. Lead quenching will also cause environmental pollution, and the mechanical properties of the prepared steel strips are unstable and uneven. Summary of the invention

[0005] The purpose of the present invention application is to provide a high-strength packaging steel strip continuous annealing heat treatment equipment and a heat treatment method thereof, so as to partially or completely solve the problems raised in the above-mentioned background technology.

[0006] In the first aspect, the present invention provides a high-strength packaging steel strip continuous annealing heat treatment equipment, comprising an inlet sealing section, a heating annealing section, and an outlet sealing section arranged in sequence; a plurality of guide roller groups and medium-frequency transverse and longitudinal magnetic induction heaters for conveying the steel strip are alternately arranged in the heating annealing section, and the medium-frequency transverse and longitudinal magnetic induction heater can adjust the direction of the magnetic field to generate a transverse magnetic field with a magnetic field direction perpendicular to the surface of the steel strip or to generate a longitudinal magnetic field with a magnetic field direction parallel to the surface of the steel strip.

[0007] Optionally, the medium frequency horizontal and vertical magnetic induction heater includes a mounting frame, a cross bracket, and a support plate. The outer side of the cross bracket is rotatably mounted on the mounting frame through a rotating shaft, and the L-shaped support plate is mounted on the outer side of the mounting frame. The first conveying roller group and the second conveying roller group are mounted on the cross bracket, and the conveying directions of the first conveying roller group and the second conveying roller group are perpendicular to each other; a pair of rectangular induction heating coils are arranged on the swing arm of the cross bracket on which the first conveying roller group is mounted, and the second conveying roller group is located between the two induction heating coils, and an internal gear is installed on the shaft end of the rotating shaft on the outer side of the cross bracket after passing through the mounting frame, and a driven pulley and a driving pulley are rotatably mounted on the support plate, and the driven pulley is connected to the driving pulley through a synchronous belt drive, and the rotating shaft of the driving pulley is coaxially connected to the output shaft of a driving motor fixedly mounted on the mounting frame, and the rotating shaft of the driven pulley is connected to the external gear after passing through the support plate, and the external gear is meshed with the internal gear.

[0008] Optionally, a limiting mechanism is arranged on the inner side of the support plate, and the limiting mechanism includes a mounting plate and an electric push rod. The electric push rod is fixed to the support plate through the mounting plate. A limiting block is fixed at the push rod end of the electric push rod, and four limiting grooves matching the limiting block are evenly arranged on the side of the inner gear.

[0009] Optionally, a first heat insulation board is arranged on the outer side of the first conveying roller group, and a second heat insulation board is arranged on the outer side of the second conveying roller group, and both the first heat insulation board and the second heat insulation board are fixedly mounted on the cross bracket.

[0010] Optionally, a plurality of temperature sensors are further provided in the heating and annealing section, and each temperature sensor is located below and in front of a corresponding guide roller group in the conveying direction of the steel strip.

[0011] Optionally, the heating annealing section is divided into a decarburization zone, a cooling zone, and a nitriding zone. Hydrogen gas distribution pipes are arranged on both the upper and lower sides of the decarburization zone, and the inlet of the hydrogen gas distribution pipe is connected to a hydrogen access port arranged at the starting end of the decarburization zone for connecting to an external hydrogen gas source. Nitrogen gas distribution pipes are arranged on both the upper and lower sides of the cooling zone, and the inlet of the nitrogen gas distribution pipe is connected to a nitrogen access port arranged at the starting end of the cooling zone for connecting to an external nitrogen gas source. Ammonia gas distribution pipes are arranged on both the upper and lower sides of the nitriding zone, and the inlet of the ammonia gas distribution pipe is connected to an ammonia access port arranged at the starting end of the nitriding zone for connecting to an external ammonia gas source. A mixed gas outlet is arranged at the tail end of the nitriding zone.

[0012] In a second aspect, the present invention provides a method for continuous annealing heat treatment of a high-strength packaging steel strip, using the above-mentioned continuous annealing heat treatment equipment for the high-strength packaging steel strip, comprising:

[0013] The hot-rolled steel strip is automatically fed and enters the heating annealing section from the entrance sealing section. It is heated by medium-frequency transverse or longitudinal magnetic induction heaters. After being discharged from the exit sealing section, it is water-cooled to obtain the heat-treated steel strip.

[0014] Optionally, the continuous annealing heat treatment method for high-strength packaging steel strip also includes: during induction heating in the heating annealing section, hydrogen, nitrogen and ammonia are introduced into the decarburization zone, cooling zone and nitriding zone from the hydrogen inlet, nitrogen inlet and ammonia inlet respectively to perform decarburization, cooling and nitriding.

[0015] Optionally, the temperature of the decarburization zone is controlled to be 975-995°C, the temperature of the cooling zone is controlled to be 775-875°C, the temperature of the nitriding zone is controlled to be 750-850°C, and the running speed of the steel strip is controlled to be 1-5m / min.

[0016] Optionally, the chemical composition of the steel strip after heat treatment is as follows in percentage by mass: C≤0.03%, Mn≤1.2%, P≤0.012%, S≤0.008%, Si≤0.8%, Cr 24-26%, Ni 6-8%, Mo 3-5%, N 0.24-0.32%, Cu≤0.5%, and the rest is iron.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] In the present invention application, a medium-frequency transverse and longitudinal magnetic induction heater capable of adjusting the direction of the magnetic field is used to heat treat the steel strip, which can efficiently, quickly and evenly heat the steel strip, and realize decarburization and nitriding treatment during annealing in the heating annealing section, thereby improving the strength and toughness of the steel strip surface and the corrosion resistance of the steel strip, so that the high-strength packaging steel strip obtained by heat treatment has stable mechanical properties, a tensile strength of 1230-1380MPa, and an elongation of not less than 38%, which meets the requirements of high-strength packaging steel strip. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of the high-strength packaging steel strip continuous annealing heat treatment equipment applied for by the present invention;

[0020] Figure 2 for Figure 1 A schematic diagram of the structure of the medium frequency transverse and longitudinal magnetic induction heater;

[0021] Figure 3 It is a structural schematic diagram of a medium frequency transverse and longitudinal magnetic induction heater without a first heat insulation plate and a second heat insulation plate;

[0022] Figure 4 for Figure 3 A partial enlarged view of the middle A;

[0023] Figure 5 for Figure 4 The front view of the inner gear;

[0024] Figure markings: 1-guide roller group, 2-medium frequency horizontal and vertical magnetic induction heater, 201-mounting frame, 202-cross bracket, 203-induction heating coil, 204-first heat insulation plate, 205-second heat insulation plate, 206-first conveying roller group, 207-second conveying roller group, 208-support plate, 209-inner gear, 2091-limiting groove, 210-outer gear, 211-driven pulley, 212-driving pulley, 213-synchronous belt, 214-driving motor, 215-limiting block, 216-mounting plate, 217-electric push rod, 3-temperature sensor, 4-inlet sealing section, 5-outlet sealing section, 6-hydrogen inlet, 7-hydrogen gas distribution pipe, 8-nitrogen inlet, 9-nitrogen gas distribution pipe, 10-ammonia inlet, 11-ammonia gas distribution pipe, 12-mixed gas outlet, 13-steel belt. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0026] like Figures 1 to 5 As shown, in the first aspect, the present invention provides a high-strength packaging steel strip continuous annealing heat treatment equipment, comprising an inlet sealing section 4, a heating annealing section, and an outlet sealing section 5 arranged in sequence; a plurality of guide roller groups 1 and medium-frequency transverse and longitudinal magnetic induction heaters 2 for conveying the steel strip 13 are alternately arranged in the heating annealing section, and the medium-frequency transverse and longitudinal magnetic induction heaters 2 can adjust the direction of the magnetic field to generate a transverse magnetic field with a magnetic field direction perpendicular to the surface of the steel strip 13 or to generate a longitudinal magnetic field with a magnetic field direction parallel to the surface of the steel strip 13; a plurality of temperature sensors 3 are also provided in the heating annealing section, and each temperature sensor 3 is located in front of and below the corresponding guide roller group 1 in the conveying direction of the steel strip 13.

[0027] In the present invention, the medium-frequency transverse and longitudinal magnetic induction heater 2 can adjust the direction of the magnetic field to be transverse or longitudinal. The transverse direction is to generate a transverse magnetic field perpendicular to the surface of the steel strip 13, and the longitudinal direction is to generate a longitudinal magnetic field parallel to the surface of the steel strip 13. When the transverse magnetic field is adopted, it can be used to quickly heat and heat the steel strip 13, and when the longitudinal magnetic field is adopted, it can be used to fine-tune the temperature of the steel strip 13 to ensure the temperature uniformity in the width direction of the steel strip 13 during the heat treatment of the steel strip 13. The present invention is based on multiple medium-frequency transverse and longitudinal magnetic induction heaters 2 that can adjust the direction of the magnetic field to achieve flexible selection of multiple heating and annealing modes for the steel strip 13, such as multiple medium-frequency transverse and longitudinal magnetic induction heaters 2 that generate transverse magnetic fields are continuously arranged to form a transverse heating zone, multiple medium-frequency transverse and longitudinal magnetic induction heaters 2 that generate longitudinal magnetic fields are continuously arranged to form a longitudinal heating zone, and multiple medium-frequency transverse and longitudinal magnetic induction heaters 2 that generate transverse or longitudinal magnetic fields are alternately arranged to form a longitudinal and transverse alternating heating zone.

[0028] Specifically, the medium frequency horizontal and vertical magnetic induction heater 2 includes a mounting frame 201, a cross bracket 202, and a support plate 208. The outer side of the cross bracket 202 is rotatably mounted on the mounting frame 201 through a rotating shaft, and the L-shaped support plate 208 is mounted on the outer side of the mounting frame 201. The cross bracket 202 is mounted with a first conveying roller group 206 and a second conveying roller group 207. The conveying directions of the first conveying roller group 206 and the second conveying roller group 207 are perpendicular to each other. A pair of rectangular induction heating coils 203 are arranged on the swing arm of the cross bracket 202 on which the first conveying roller group 206 is mounted. The feed roller group 207 is located between the two induction heating coils 203. The rotating shaft on the outer side of the cross bracket 202 passes through the mounting frame 201 and the inner gear 209 is installed on the rear shaft end. The driven pulley 211 and the driving pulley 212 are rotatably installed on the support plate 208. The driven pulley 211 and the driving pulley 212 are connected through a synchronous belt 213. The rotating shaft of the driving pulley 212 is coaxially connected to the output shaft of the driving motor 214 fixedly set on the mounting frame 201. The rotating shaft of the driven pulley 211 passes through the support plate 208 and is connected to the outer gear 210, and the outer gear 210 is meshed with the inner gear 209.

[0029] For the same steel strip 13, when the first roll of hot-rolled steel strip 13 enters the annealing heating section for annealing treatment, each medium-frequency horizontal and vertical magnetic induction heater 2 flexibly and timely adjusts the magnetic field direction of the induction heating coil 203 through the driving motor 214 according to the temperature information of the steel strip 13 detected by the corresponding temperature sensor 3 arranged in front, and adjusts the electrical parameters of each induction heating coil 203 at the same time to ensure the uniformity of the heating temperature and high heating efficiency; when the same steel strip 13 enters the annealing heating section for annealing treatment subsequently, there is no need to change the magnetic field direction, thereby ensuring the consistency of the annealing quality of the same steel strip 13.

[0030] Specifically, a limiting mechanism is provided inside the support plate 208, and the limiting mechanism includes a mounting plate 216 and an electric push rod 217. The electric push rod 217 is fixed to the support plate 208 through the mounting plate 216. The push rod end of the electric push rod 217 fixes the limiting block 215, and four limiting grooves 2091 matching the limiting block 215 are evenly provided on the side of the inner gear 209. When the electric push rod 217 drives the limiting block 215 to be inserted into the limiting groove 2091, the cross bracket 202 is prevented from rotating, thereby improving the operation stability of the medium frequency horizontal and vertical magnetic induction heater 2.

[0031] Specifically, a first heat insulation board 204 is disposed outside the first conveying roller group 206 , and a second heat insulation board 205 is disposed outside the second conveying roller group 207 . Both the first heat insulation board 204 and the second heat insulation board 205 are fixedly mounted on the cross bracket 202 .

[0032] Specifically, the heating and annealing section is divided into a decarburization zone, a cooling zone, and a nitriding zone. Hydrogen distribution pipes 7 are arranged on both the upper and lower sides in the decarburization zone. The inlet of the hydrogen distribution pipe 7 is communicated with a hydrogen inlet 6 arranged at the starting end of the decarburization zone and used for connecting an external hydrogen gas source. Nitrogen distribution pipes 9 are arranged on both the upper and lower sides in the cooling zone. The inlet of the nitrogen distribution pipe 9 is communicated with a nitrogen inlet 8 arranged at the starting end of the cooling zone and used for connecting an external nitrogen gas source. Ammonia distribution pipes 11 are arranged on both the upper and lower sides in the nitriding zone. The inlet of the ammonia distribution pipe 11 is communicated with an ammonia inlet 10 arranged at the starting end of the nitriding zone and used for connecting an external ammonia gas source. A mixed gas outlet 12 is arranged at the end of the nitriding zone. During the annealing process in the heating and annealing section, hydrogen, nitrogen, and ammonia are introduced in stages, realizing the decarburization and nitriding treatment of the steel strip 13 and improving the mechanical properties of the surface of the steel strip 13.

[0033] In the present invention application, the hydrogen distribution pipe 7, the nitrogen distribution pipe 9, and the ammonia distribution pipe 11 can at least adopt a "rich" - shaped structure.

[0034] In a second aspect, the present invention application provides a continuous annealing heat treatment method for a high - strength packaging steel strip, adopting the continuous annealing heat treatment equipment for a high - strength packaging steel strip described in any one of the above - mentioned first aspects, including:

[0035] The hot - rolled steel strip 13 is automatically fed, enters the heating and annealing section from the inlet sealing section 4, undergoes intermediate - frequency transverse or longitudinal magnetic induction heating by an intermediate - frequency transverse and longitudinal magnetic induction heater, and after being discharged from the outlet sealing section 5, is further cooled by water to obtain the heat - treated steel strip.

[0036] The continuous annealing heat treatment method for the high - strength packaging steel strip further includes: when performing induction heating in the heating and annealing section, steps of introducing hydrogen, nitrogen, and ammonia into the decarburization zone, the cooling zone, and the nitriding zone respectively from the hydrogen inlet, the nitrogen inlet, and the ammonia inlet for decarburization, cooling, and nitriding.

[0037] Specifically, hydrogen is introduced from the hydrogen inlet 6 for air replacement, so that a hydrogen atmosphere is formed inside the inlet sealing section 4, the heating and annealing section, and the outlet sealing section 5. The hot - rolled steel strip 13 is automatically fed, enters the heating and annealing section from the inlet sealing section 4, and undergoes intermediate - frequency transverse or longitudinal magnetic induction heating by the intermediate - frequency transverse and longitudinal magnetic induction heater 2. After decarburization treatment in the decarburization zone, it enters the cooling zone, nitrogen is introduced from the nitrogen inlet 8 to cool the steel strip 13 passing through the cooling zone, ammonia is introduced from the ammonia inlet 10 to perform nitriding treatment on the steel strip 13 entering the nitriding zone. After being discharged from the outlet sealing section 5, it is further cooled by water to obtain the heat - treated steel strip 13, and the mixed gas is discharged through the mixed gas outlet 12.

[0038] In some embodiments, the hot-rolled steel strip 13 is made of 2507 stainless steel, the temperature of the decarburization zone is controlled to be 980±5°C, the temperature of the cooling zone is 780±5°C, the temperature of the nitriding zone is 755±5°C, and the running speed of the steel strip 13 is 2.5m / min; the chemical composition of the heat-treated steel strip 13 is as follows by mass percentage: C 0.03%, Mn 1.2%, P 0.012%, S 0.008%, Si0.8%, Cr 25%, Ni 7%, Mo 4%, N 0.28%, Cu 0.5%, and the rest is iron. Performance test: tensile strength is 1230MPa, and elongation is 38%.

[0039] In some embodiments, the hot-rolled steel strip 13 is made of 2507 stainless steel, the temperature of the decarburization zone is controlled to be 985±5°C, the temperature of the cooling zone is 850±5°C, the temperature of the nitriding zone is 800±5°C, and the running speed of the steel strip 13 is 2.5m / min; the chemical composition of the heat-treated steel strip 13 is as follows in mass percentage: C 0.03%, Mn 1.2%, P 0.011%, S 0.007%, Si0.8%, Cr 25%, Ni 7%, Mo 4%, N 0.28%, Cu 0.5%, and the rest is iron; performance test: tensile strength is 1380MPa, and elongation is 40%.

[0040] In some embodiments, in the present application, the hot-rolled steel strip 13 is made of 2507 stainless steel, the temperature of the decarburization zone is controlled to be 990±5°C, the temperature of the cooling zone is 870±5°C, the temperature of the nitriding zone is 845±5°C, and the running speed of the steel strip 13 is 1-5m / min; the chemical composition of the heat-treated steel strip 13 is as follows in mass percentage: C 0.03%, Mn 1.2%, P 0.01%, S 0.005%, Si 0.8%, Cr 25%, Ni 7%, Mo 4%, N 0.28%, Cu 0.5%, and the rest is iron; performance test: tensile strength is 1230MPa, elongation is 41%.

[0041] The hot-rolled steel strips 13 in the above embodiments are all made of 2507 stainless steel. The present invention adopts a medium-frequency transverse and longitudinal magnetic induction heater 2 for annealing treatment, which reduces the heat treatment temperature of the 2507 stainless steel and improves the mechanical properties of the steel strip 13, making the mechanical properties of the steel strip 13 more stable and uniform.

[0042] In the continuous annealing heat treatment method of the high-strength packaging steel strip applied for by the present invention, the steel strip is heat treated by adopting a medium-frequency transverse and longitudinal magnetic induction heater capable of adjusting the direction of the magnetic field, so that the steel strip can be heated quickly and evenly with high efficiency, and decarburization and nitriding treatment is achieved during annealing in the heating annealing section, thereby improving the strength and toughness of the steel strip surface and the corrosion resistance of the steel strip, so that the high-strength packaging steel strip obtained by heat treatment has stable mechanical properties, a tensile strength of 1230-1380MPa, and an elongation of not less than 38%, which meets the requirements of the performance parameters of the high-strength packaging steel strip product.

Claims

1. A high-strength packaging steel strip continuous annealing heat treatment equipment, characterized in that: It comprises an inlet sealing section, a heating and annealing section and an outlet sealing section which are arranged in sequence; a plurality of guide roller groups and medium-frequency transverse and longitudinal magnetic induction heaters for conveying the steel strip are alternately arranged in the heating and annealing section, and the medium-frequency transverse and longitudinal magnetic induction heaters can adjust the direction of the magnetic field to generate a transverse magnetic field with a magnetic field direction perpendicular to the surface of the steel strip or a longitudinal magnetic field with a magnetic field direction parallel to the surface of the steel strip.

2. A high-strength packaging steel strip continuous annealing heat treatment equipment as claimed in claim 1, characterized in that: The medium frequency horizontal and vertical magnetic induction heater includes a mounting frame, a cross bracket, and a support plate. The outer side of the cross bracket is rotatably mounted on the mounting frame through a rotating shaft, and the L-shaped support plate is mounted on the outer side of the mounting frame. The first conveying roller group and the second conveying roller group are mounted on the cross bracket. A pair of rectangular induction heating coils are arranged on the swing arm of the cross bracket on which the first conveying roller group is mounted, and the second conveying roller group is located between the two induction heating coils. After the rotating shaft on the outer side of the cross bracket passes through the mounting frame, an internal gear is installed on the shaft end. A driven pulley and a driving pulley are rotatably mounted on the support plate. The driven pulley and the driving pulley are connected through a synchronous belt transmission. The rotating shaft of the driving pulley is coaxially connected to the output shaft of a driving motor fixedly arranged on the mounting frame. The rotating shaft of the driven pulley passes through the support plate and is connected to the external gear, and the external gear is meshed with the internal gear.

3. A high-strength packaging steel strip continuous annealing heat treatment equipment as claimed in claim 2, characterized in that: A limiting mechanism is arranged on the inner side of the support plate, and the limiting mechanism comprises a mounting plate and an electric push rod. The electric push rod is fixed to the support plate through the mounting plate. A limiting block is fixed on the push rod end of the electric push rod, and four limiting grooves matching the limiting block are evenly arranged on the side of the inner gear.

4. A high-strength packaging steel strip continuous annealing heat treatment equipment as claimed in claim 3, characterized in that: A first heat insulation board is arranged outside the first conveying roller group, and a second heat insulation board is arranged outside the second conveying roller group. Both the first heat insulation board and the second heat insulation board are fixedly mounted on the cross bracket.

5. The high-strength packaging steel strip continuous annealing heat treatment equipment according to claim 1, characterized in that: The heating and annealing section is also provided with a plurality of temperature sensors, each of which is located in the front and lower part of the corresponding guide roller group in the direction of conveying the steel strip.

6. The high-strength packaging steel strip continuous annealing heat treatment equipment according to claim 1, characterized in that: The heating annealing section is divided into a decarburization zone, a cooling zone, and a nitriding zone. Hydrogen gas distribution pipes are arranged on both upper and lower sides of the decarburization zone, and the inlet of the hydrogen gas distribution pipe is connected to a hydrogen inlet arranged at the starting end of the decarburization zone for connecting to an external hydrogen gas source. Nitrogen gas distribution pipes are arranged on both upper and lower sides of the cooling zone, and the inlet of the nitrogen gas distribution pipe is connected to a nitrogen inlet arranged at the starting end of the cooling zone for connecting to an external nitrogen gas source. Ammonia gas distribution pipes are arranged on both upper and lower sides of the nitriding zone, and the inlet of the ammonia gas distribution pipe is connected to an ammonia inlet arranged at the starting end of the nitriding zone for connecting to an external ammonia gas source. A mixed gas outlet is arranged at the tail end of the nitriding zone.

7. A continuous annealing heat treatment method for high-strength packaging steel strip, characterized in that: The continuous annealing heat treatment equipment for the high-strength packaging steel strip according to claim 6 comprises: The hot-rolled steel strip is automatically fed and enters the heating annealing section from the entrance sealing section. It is heated by medium-frequency transverse or longitudinal magnetic induction heaters. After being discharged from the exit sealing section, it is water-cooled to obtain the heat-treated steel strip.

8. The continuous annealing heat treatment method for high-strength packaging steel strip according to claim 7, characterized in that: The high-strength packaging steel strip continuous annealing heat treatment method also includes: during induction heating in the heating annealing section, hydrogen, nitrogen and ammonia are introduced into the decarburization zone, cooling zone and nitriding zone from the hydrogen inlet, nitrogen inlet and ammonia inlet respectively to perform decarburization, cooling and nitriding.

9. The continuous annealing heat treatment method for high-strength packaging steel strip according to claim 8, characterized in that: The temperature of the decarburization zone is controlled at 975-995°C, the temperature of the cooling zone is controlled at 775-875°C, the temperature of the nitriding zone is controlled at 750-850°C, and the running speed of the steel belt is controlled at 1-5m / min.

10. The continuous annealing heat treatment method for high-strength packaging steel strip according to claim 7, characterized in that: The chemical composition of the heat-treated steel strip is as follows by mass percentage: C≤0.03%, Mn≤1.2%, P≤0.012%, S≤0.008%, Si≤0.8%, Cr 24-26%, Ni 6-8%, Mo 3-5%, N 0.24-0.32%, Cu≤0.5%, and the rest is iron.

Images