Hot-rolled high-strength steel and plate shape control and optimization method thereof

Abstract

The invention discloses hot-rolled high-strength steel and a method for controlling and optimizing the shape of the hot-rolled high-strength steel, and belongs to the field of production methods of the hot-rolled high-strength steel. The tensile strength level of the hot-rolled high-strength steel is 500-700 MPa, and the thickness of the hot-rolled high-strength steel is 2.0- According to the plate shape control and optimization method, a steel coil is obtained through the production technological processes of plate blank heating, rough rolling, finish rolling, laminar cooling and coiling, the steel coil is fed into a cover type annealing furnace to be subjected to stress relief annealing treatment, hot-rolled high-strength steel with the good plate shape is obtained, according to the annealing technology, the temperature is increased to 450-550 DEG C from the room temperature, and the heating time is 3.5-4.5 h; the annealing temperature ranges from 450 DEG C to 550 DEG C, and the annealing time ranges from 19.5 h to 20.5 h; and stopping fire, performing furnace cooling in a bell-type furnace, and when the temperature is reduced to 180-220 DEG C, taking out and performing air cooling to room temperature. The method can effectively solve the problem that the plate shape is poor after the internal stress is released after the subsequent steel plate is uncoiled or coiled because the internal stress of the existing hot-rolled steel plate is non-uniform.

Description

Technical Field

[0001] The invention belongs to the technical field of hot-rolled high-strength steel production methods, and relates to a method for improving the plate shape of hot-rolled high-strength steel by using a bell-type annealing furnace, and specifically relates to a hot-rolled high-strength steel and a method for controlling and optimizing the plate shape thereof. Background Art

[0002] With the promotion and application of microalloying elements such as Nb, V, and Ti in hot-rolled high-strength steel, the strength level of hot-rolled steel plates has been greatly improved. Along with this, the microstructure of high-strength steel has been significantly refined, and the precipitation of the second phase has increased significantly. Under the influence of large fluctuations in the hot rolling process and uneven temperature, the grain size of high-strength steel and the amount of second phase precipitation are uneven in the length, width, and thickness directions of the steel plate, which also leads to uneven internal stress of the steel plate. After the steel plate is unrolled or coiled, the internal stress is released, resulting in poor plate shape, which affects the final use of users. Therefore, solving the plate shape problem is of great significance for improving the quality and promoting the application of hot-rolled high-strength steel products.

[0003] After searching, CN202311268132.8 discloses a method for eliminating the edge waves of hot-rolled free-rolled strip, which adopts the "narrow-wide-narrow-wide-narrow-wide" "bamboo-shaped" rolling mode, specifically including: 1) free rolling of products with a furnace temperature range of 1210-1240℃; 2) when the length of the rolled strip reaches 40-45 kilometers, reverse width free rolling begins, and the entire finishing work roll rolling cycle is up to 110 kilometers; 3) the maximum width of the reverse width transition material is less than 300mm different from the width of the previous product; 4) the hot-rolled strip with a thickness of 1.2-25.4mm is divided into more than 5 thickness levels, and the thickness of the first transition material for free rolling is not less than two thickness levels of the main rolled material. When solving the problem of the rolling plate shape of reverse width products, give full play to the advantage of the rolling mill that can change the convexity of the strip, control the hot-rolled plate shape with the convexity, solve the plate shape problem, realize the alternating rolling of wide and narrow materials within the cycle, and improve production capacity.

[0004] CN202210835311.4 discloses a method for controlling the shape of hot-rolled thin plates, which is characterized by comprising the following steps: 1) When the surface temperature of the billet is above 500°C before rough rolling, the billet is charged into a furnace for reheating, the heating time is ≥150min, and the heating temperature is 1280-1320°C; 2) rough rolling + finishing rolling, the billet surface temperature is ≥1100°C at the end of rough rolling, and the billet surface temperature is 880°C-930°C at the end of finishing rolling. The rolling convexity is continuously and evenly reduced from 60IU to 20IU along the rolling direction of the billet; 3) After finishing rolling, the cooling process is controlled, first spraying water for rapid cooling, and then slowly cooling in the air. During the rapid cooling process, the upper and lower water volumes are both 25% of the rated total water volume, the water pressure is 1.2-1.6 bar, the cooling rate is 25-35℃ / s, the outlet water temperature of the strip after water spray rapid cooling is controlled between 640-700℃, and the slow cooling time in the air is controlled between 18-25s; 4) After the cooling, the plate is coiled when its surface temperature is ≥600℃. After coiling, the steel coil enters the insulation wall for further cooling, the temperature entering the insulation wall is ≥500℃, the cooling time is ≥48h, and it is removed from the insulation wall when the temperature is lower than 100℃.

[0005] As can be seen from the above, the existing technology mainly controls the plate shape problem of hot-rolled high-strength steel from the aspects of rolling process and laminar cooling process, and there is no method for improving the plate shape of high-strength steel through a hood annealing furnace. Summary of the invention

[0006] The technical problem to be solved by the present invention is that the existing hot-rolled steel plate has uneven internal stress, which leads to the problem of poor plate shape after the internal stress is released after the subsequent uncoiling or splitting of the steel plate.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] In a first aspect, the present invention provides a method for controlling and optimizing the plate shape of hot-rolled high-strength steel: a steel coil is obtained through a production process of slab heating, rough rolling, finish rolling, laminar cooling, and coiling, and the steel coil is sent to a bell-type annealing furnace for stress relief annealing to obtain hot-rolled high-strength steel with good plate shape; wherein the annealing process comprises the following steps:

[0009] 1) Heating stage: heating from room temperature to 450℃~550℃, heating time 3.5h~4.5h;

[0010] 2) Annealing stage: annealing temperature 450℃~550℃, annealing time 19.5h~20.5h;

[0011] 3) Cooling section: Stop the fire and cool in the bell-type furnace. When it cools to 180℃~220℃, take the steel coil out of the bell-type furnace and air cool to room temperature.

[0012] In the above step 1), N2 was introduced into the heating section from the beginning of heating, and the N2 flow rate was 14.5m3 / h~15.5m 3 / h.

[0013] In the above step 2), N2 was continuously introduced into the annealing section, and the N2 flow rate was 29.5m 3 / h~30.5m 3 / h.

[0014] The slab heating is carried out in any of the following ways:

[0015] The slab is sent into the heating furnace by hot delivery and hot charging, and the charging temperature is 500℃~700℃;

[0016] After the ingot stack is slowly cooled to room temperature, it is sent to the slab heating furnace by cold loading. When stacking the ingots, hot ingots with a temperature higher than 500°C must be stacked on both sides, and the ingots should not be placed on the top and bottom layers of the stack.

[0017] The above-mentioned rough rolling is carried out by using two single-stand reversible rough rolling mills. The sickle bend value is monitored in real time at the exit of the two rough rolling mills, and the feedback is fed back to the control system to adjust the inclination value of the rolling mill in real time, so as to control the rough rolling sickle bend within the range of -20mm to 20mm.

[0018] The above-mentioned finishing rolling is carried out by using a 6-7-stand irreversible finishing rolling mill unit. The first two stands adopt a positive shifting method with a roll shifting amount of 50mm-100mm, the middle 2-3 stands adopt a positive shifting method with a roll shifting amount of 0mm-50mm, and the last two stands adopt a negative shifting method with a roll shifting amount of -50mm-0mm; the convexity of the finishing mill outlet is controlled in the range of 20μm-50μm, and the wedge shape is controlled in the range of no more than 30μm.

[0019] The laminar cooling adopts a sparse cooling method, the header opening mode is open 1 and closed 1, and the cooling rate is 10°C / s to 30°C / s; after cooling to 590°C to 610°C, it is coiled, and after the coiled steel coil is cooled to room temperature, it is sent to a hood annealing furnace for stress relief annealing.

[0020] In a second aspect, the present invention provides a hot-rolled high-strength steel produced by the above-mentioned method for controlling and optimizing the plate shape of hot-rolled high-strength steel.

[0021] The tensile strength level of the above-mentioned hot-rolled high-strength steel is 500MPa to 700MPa (tensile strength is 500MPa to 800MPa), and the thickness specification is 2.0mm to 12.0mm.

[0022] The beneficial effects of the present invention are as follows: the present invention adopts a hood annealing furnace for stress relief annealing, providing a new idea for improving the plate shape. Compared with the traditional slow cooling pit stress relief annealing or conventional heat treatment furnace stress relief annealing, the hood annealing furnace adopts N2 protection, which can improve the plate shape while avoiding the generation of thick iron oxide scale during heating. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The plate shape of the steel after uncoiling and stripping in Example 1;

[0024] Figure 2 The plate shape of the steel after uncoiling and stripping in Example 2;

[0025] Figure 3 The plate shape of the steel after uncoiling and slitting in Comparative Example 1;

[0026] Figure 4 This is the plate shape of the comparative example 2 steel after uncoiling and stripping. DETAILED DESCRIPTION

[0027] The technical solution of the present invention can be specifically implemented in the following manner.

[0028] The present invention provides a method for controlling and optimizing the plate shape of hot-rolled high-strength steel. Firstly, the reason why the hot-rolled high-strength steel described in the present invention is prone to plate shape defects is briefly explained.

[0029] With the technological progress of microalloyed steel, microalloying elements such as Nb and Ti are widely used in hot-rolled high-strength steel. Domestic and foreign steel enterprises generally use Nb and Ti microalloying to carry out industrial trial production of hot-rolled high-strength steel. Nb mainly plays a role in promoting grain refinement in steel. It is easy to form NbC precipitation phase during the finishing rolling process. This precipitation phase and Nb dissolved in austenite can both play a role in pinning austenite grain boundaries and promoting grain refinement. Each process of hot rolling of Ti is easy to form a second phase precipitation, which can precipitate deformation-induced precipitation, interphase precipitation, and supersaturated precipitation in the rolling, laminar cooling, and coiling stages. At the same time, the above-mentioned precipitation is relatively sensitive to temperature. When the hot rolling process is unstable, the cooling is uneven, and the temperature is uneven, it is easy to cause different grain sizes and precipitation phase quantities at different positions of the steel plate, resulting in uneven internal stress distribution of the steel plate, which in turn leads to plate shape defects.

[0030] Secondly, the main reasons for limiting the production process parameters in the method for controlling and optimizing the hot-rolled high-strength steel plate shape described in the present invention are explained.

[0031] First, in terms of heating system. During the cooling process of the billet, the temperature of the billet surface drops faster and the temperature of the billet core drops slower, so the normal air-cooled billet will produce thermal stress in the thickness direction. The use of billet stacking and slow cooling is conducive to reducing the temperature difference between the billet surface and the core, reducing the difference in grain size between the billet surface and the core, and reducing internal stress. The use of hot delivery and hot loading can also effectively reduce the difference in billet grain size, temperature drop and internal stress. At the same time, compared with cold loading, the temperature of the billet core is higher when hot delivery and hot loading is used, which is conducive to the penetration of rolling deformation into the billet core, which is conducive to improving the uniformity of steel plate structure and reducing the uneven internal stress in the thickness direction of the steel plate.

[0032] Second, in terms of rolling process. The shape of the steel plate has a genetic effect from the rough rolling unit to the finishing unit, so the shape of the rough rolled steel plate must be controlled first. The present invention detects the sickle bend at the outlet of the rough rolling unit and feeds back to the rough rolling control system to adjust the inclination value of the rolling mill, thereby controlling the rough rolling sickle bend within the range of -20mm to 20mm. Secondly, the control of convexity and wedge shape during finishing rolling is crucial to improving the plate shape. The present invention provides the roller shifting control requirements for each finishing rolling stand. Among them, the first two stands adopt positive shifting to reduce the convexity of the steel plate, but the roll shifting amount cannot be too high to avoid the steel plate from generating middle waves. The present invention limits the roll shifting amount of the first two stands to 50mm~100mm; the middle 2~3 stands continue to adopt positive shifting to reduce the convexity of the steel plate. Since the thickness of the steel plate is reduced after rolling by the first two stands, the roll shifting amount is reduced compared with the first two stands. The present invention stipulates that the roll shifting amount of the middle 2~3 stands is 0mm~50mm; the last two stands adopt negative shifting, with a roll shifting amount of -50mm~0mm. First, it is to avoid the convexity being too low, resulting in excessive reduction in the center of the steel plate and thus forming middle waves. Second, it is to increase the reduction of the width edge of the steel plate, so that the plate shape of the steel plate at the finish rolling outlet is controlled to be "micro edge wave". Therefore, the present invention limits the convexity of the finishing mill outlet to be controlled in the range of 20μm~50μm, and the wedge shape is controlled to be no higher than 30μm.

[0033] Third, in terms of laminar cooling process. During laminar cooling, the cooling of the steel plate along the width direction is uneven. Heat transfer occurs along the upper and lower surfaces in the middle of the width of the steel plate, while the edges of the width of the steel plate can dissipate heat along the sides in addition to the upper and lower surfaces of the steel plate. The temperature drops faster at the edges of the width of the steel plate, resulting in a finer structure at the edges, and the austenite → ferrite phase transformation occurs more preferentially at the edges of the width of the plate than in the middle of the width of the plate. Since the linear expansion coefficient of austenite is higher than that of ferrite, the edges of the steel plate shrink and tensile stress is generated. This tensile stress combined with the "micro-edge wave" created by the finishing mill is conducive to offsetting the internal stress of the steel plate and improving the shape of the steel plate. On the other hand, the laminar cooling water cooling rate also has a great influence on the plate shape of the steel plate. When a faster cooling rate is used, it is easy to cause a difference in the structure of the surface and the core of the steel plate in the thickness direction, resulting in a finer surface structure and a coarser core structure, which will also cause residual stress. At the same time, after the cooling rate is increased, a large amount of cooling water accumulates on the surface of the steel plate and cannot be removed in time. It may also cause the laminar cooling water on the surface of the steel plate to be unable to circulate in time, affecting the cooling efficiency. Therefore, the present invention requires that laminar cooling adopts sparse cooling, the header opening mode is on 1 and off 1, and requires a lower cooling rate of 10℃ / s~30℃ / s.

[0034] Fourth, in terms of the hood annealing process, since the main purpose of the annealing process is to reduce the residual stress of the steel plate, the annealing temperature should not be too high and should be lower than the austenite recrystallization temperature range and the ferrite pearlite transformation range, but the temperature should not be too low, otherwise the stress relief effect will be limited. Therefore, the present invention limits the annealing temperature to 450℃~550℃. At the same time, in order to reduce the thermal stress during heating and cooling, the present invention sets the heating rate and cooling rate at a lower level. In the heating stage, the heating time is set to be longer, 3.5h~4.5h. In the cooling stage, the steel coil is cooled to 180℃~220℃ in the annealing furnace.

[0035] The technical solution and effects of the present invention are further illustrated below through practical examples.

[0036] Example

[0037] Example 1 610L steel with a thickness of 10 mm and a tensile strength of 663 MPa was prepared by slab heating-rough rolling-finishing rolling-laminar cooling-coiling-hood annealing. The specific preparation steps are as follows.

[0038] The ingot was sent to the heating furnace for heating by hot delivery and hot loading, with an entry temperature of 603°C and an exit temperature of 1210°C. Six passes were used for rough rolling, and the sickle bending value of the intermediate billet after rough rolling was 15mm. Seven stands (2+3+2) were used for finishing rolling, and the roll shifting amounts of each stand were 97mm, 55mm, 35mm, 27mm, 12mm, -10mm, and -32mm, respectively. The convexity of the finishing outlet was 39μm, and the wedge shape was 18μm. The laminar cooling adopted a sparse cooling mode of open 1 and close 1, and the steel was cooled to 608°C at a cooling rate of 18°C / s for coiling and cooling to room temperature. The steel coil was sent to a bell-type annealing furnace for stress relief annealing, and the steel coil was heated to 488°C for 4.1h, and the flow rate was 14.9m 3 / h of N2 protective gas; keep warm at 488℃ for 19.8h, and the N2 flow rate during the insulation period is 30.3m 3 / h. After annealing, the steel coil is placed in a bell-type furnace for furnace cooling. After cooling to 211°C, the steel coil is taken out of the bell-type furnace and air-cooled to room temperature.

[0039] The 610L steel prepared by the process described in Example 1 has a plate shape after uncoiling and slitting. Figure 1 It can be seen that after the steel in Example 1 is uncoiled and stripped, there is no lateral bending or warping, and the plate shape is good.

[0040] Example 2 700L steel with a thickness of 8 mm and a tensile strength of 724 MPa was prepared by slab heating-rough rolling-finishing rolling-laminar cooling-coiling-hood annealing. The specific preparation steps are as follows.

[0041] The ingots were stacked and slowly cooled before being cold loaded, and the ingots were sent to the heating furnace for heating, with a furnace temperature of 1231°C. Six passes were used for rough rolling, and the sickle bending value of the intermediate ingot after rough rolling was 17mm. Seven stands (2+3+2) were used for finishing rolling, and the roll shifting amounts of each stand were 89mm, 57mm, 32mm, 24mm, 15mm, -13mm, and -28mm, respectively. The convexity of the finishing outlet was 30μm, and the wedge shape was 21μm. The laminar cooling adopted a sparse cooling mode of open 1 and close 1, and the steel was cooled to 595°C at a cooling rate of 17°C / s for coiling and cooling to room temperature. The steel coils were sent to a bell-type annealing furnace for stress relief annealing, and the steel coils were heated to 493°C for 4.2h, and the flow rate was 15.1m 3 / h of N2 protective gas; keep warm at 493℃ for 20.5h, and the N2 flow rate during the insulation period is 30.0m 3 / h. After annealing, the steel coil is placed in a bell-type furnace for furnace cooling. After cooling to 195°C, the steel coil is taken out of the bell-type furnace and air-cooled to room temperature.

[0042] The 700L steel prepared by the process described in Example 2 has a plate shape after uncoiling and slitting. Figure 2 It can be seen that after the steel in Example 2 is uncoiled and stripped, there is no lateral bending or warping, and the plate shape is good.

[0043] Comparative Example 1: 700L steel with a thickness of 7 mm and a tensile strength of 738 MPa was prepared by slab heating-rough rolling-finishing rolling-laminar cooling-coiling-hood annealing. The specific preparation steps are as follows.

[0044] The billet is stacked and slowly cooled before being cold-charged, and the billet is sent to the heating furnace for heating, with a furnace temperature of 1222°C; the rough rolling adopts 6 passes, and the sickle bending value of the intermediate billet after rough rolling is 20mm; the finishing rolling adopts 7 stands (2+3+2) for rolling, and the roll shifting amount of each stand is 92mm, 61mm, 43mm, 31mm, 20mm, -5mm, -21mm respectively, and the convexity of the finishing rolling outlet is 29μm, and the wedge shape is 15μm; the laminar cooling adopts the front-stage centralized cooling mode (that is, the first five groups of headers are opened in sequence without interval in the middle until the coiling temperature reaches the requirement) and the steel is cooled to 608°C at a cooling rate of 35°C / s for coiling, and naturally cooled to room temperature. Then the steel coil is sent to the bell-type annealing furnace for stress relief annealing, and the steel coil is heated to 208°C for 2.3h, and the flow rate is 14.9m 3 / h of N2 protective gas; keep warm at 208℃ for 19.8h, and the N2 flow rate during the insulation period is 30.3m 3 / h. After annealing, the steel coil is placed in a bell-type furnace for furnace cooling. After cooling to 211°C, the steel coil is taken out of the bell-type furnace and air-cooled to room temperature.

[0045] The 700L steel prepared by the process described in Comparative Example 1 has a plate shape after uncoiling and slitting. Figure 3 It can be seen that the steel in Example 1 has serious lateral bending after uncoiling and stripping, which is manifested as the strips on both sides bending outward, indicating that the edges of the steel coil width direction are under compressive stress. This is mainly due to the front-stage concentrated cooling mode adopted in laminar cooling, which leads to a large cooling rate at the edges of the steel plate width, and the superposition of the effects of grain refinement and thermal stress. In addition, the hood annealing temperature is low, only 208℃, and the stress relief effect is not great, which ultimately leads to poor steel plate shape.

[0046] In comparative example 2, 510L steel with a thickness of 12 mm and a tensile strength of 576 MPa was prepared by slab heating-rough rolling-finishing rolling-laminar cooling-coiling-hood annealing.

[0047] The ingot is sent into the heating furnace for heating by hot delivery and hot loading, with an entry temperature of 544°C and an exit temperature of 1202°C. The rough rolling adopts 6 passes, and the sickle bending value of the intermediate billet after rough rolling is 18mm. The finishing rolling adopts 7 stands (2+3+2), and the roll shifting amounts of each stand are 134mm, 99mm, 57mm, 45mm, 32mm, 20mm, and 12mm respectively. The convexity of the finishing rolling outlet is 33μm, and the wedge is 16μm. The laminar cooling adopts a sparse cooling mode of open 1 and close 1, and the steel is cooled to 615°C at a cooling rate of 14°C / s for coiling. The steel coils are hot stacked and slowly cooled to room temperature. The temperature of other steel coils used for hot stacking is 485°C.

[0048] The 510L steel prepared by the process described in Comparative Example 2 has a plate shape after uncoiling and slitting. Figure 4 It can be seen that after the steel in comparative example 2 is uncoiled and stripped, the strips on both sides bend outwards. This is mainly due to the large amount of roll shifting in the finishing rolling process, which is positive shifting, resulting in the shape of the steel plate after rolling. At the same time, after the steel coil is coiled, hot stacking is used to eliminate internal stress, but the stacking slow cooling temperature is low, which does not significantly reduce the internal stress of the steel plate, and finally causes the steel plate to bend sideways after stripping.

Claims

1. A method for controlling and optimizing the shape of hot-rolled high-strength steel plate, characterized in that: The steel coil is obtained through the production process of slab heating, rough rolling, finish rolling, laminar cooling and coiling, and the steel coil is sent to the bell-type annealing furnace for stress relief annealing to obtain hot-rolled high-strength steel with good plate shape; wherein the annealing process includes the following steps: 1) Heating stage: heating from room temperature to 450℃~550℃, heating time 3.5h~4.5h; 2) Annealing stage: annealing temperature 450℃~550℃, annealing time 19.5h~20.5h; 3) Cooling section: Stop the fire and cool in the bell-type furnace. When it cools to 180℃~220℃, take the steel coil out of the bell-type furnace and air cool to room temperature.

2. The method for controlling and optimizing the hot-rolled high-strength steel plate shape according to claim 1, characterized in that: In step 1), N2 was introduced into the heating section from the beginning of heating, and the N2 flow rate was 14.5m 3 / h~15.5m 3 / h.

3. The method for controlling and optimizing the hot-rolled high-strength steel plate shape according to claim 1, characterized in that: In step 2), N2 was continuously introduced into the annealing section, and the N2 flow rate was 29.5m 3 / h~30.5m 3 / h.

4. The method for controlling and optimizing the hot-rolled high-strength steel plate shape according to claim 1, characterized in that: The slab is heated by hot delivery and hot loading into a slab heating furnace, and the loading temperature is 500°C to 700°C.

5. The method for controlling and optimizing the hot-rolled high-strength steel plate shape according to claim 1, characterized in that: The slab heating is carried out after the stack of cast billets is slowly cooled to room temperature and then sent to the slab heating furnace by cold loading. When the cast billets are stacked, hot billets with a temperature higher than 500°C must be stacked on both sides, and the billets should not be placed on the top and bottom layers of the stack.

6. The method for controlling and optimizing the hot-rolled high-strength steel plate shape according to claim 1, characterized in that: The rough rolling is carried out by using two single-frame reversible rough rolling mills. The sickle bend value is monitored in real time at the exits of the two rough rolling mills and fed back to the control system to adjust the inclination value of the rolling mill in real time, so as to control the rough rolling sickle bend within the range of -20mm to 20mm.

7. The method for controlling and optimizing the hot-rolled high-strength steel plate shape according to claim 1, characterized in that: The finishing rolling is carried out by an irreversible finishing rolling mill with 6 to 7 stands. The first two stands adopt a positive shifting method with a roll shifting amount of 50 mm to 100 mm, the middle 2 to 3 stands adopt a positive shifting method with a roll shifting amount of 0 mm to 50 mm, and the last two stands adopt a negative shifting method with a roll shifting amount of -50 mm to 0 mm. The convexity of the finishing mill outlet is controlled in the range of 20 μm to 50 μm, and the wedge shape is controlled in the range of no more than 30 μm.

8. The method for controlling and optimizing the hot-rolled high-strength steel plate shape according to claim 1, characterized in that: The laminar cooling adopts a sparse cooling method, the header opening mode is open 1 and closed 1, and the cooling rate is 10°C / s to 30°C / s; after cooling to 590°C to 610°C, coiling is performed, and after the coiled steel coil is cooled to room temperature, it is sent to a bell-type annealing furnace for stress relief annealing treatment.

9. A hot-rolled high-strength steel, characterized in that: The hot-rolled high-strength steel plate is obtained by the method for controlling and optimizing the shape of the hot-rolled high-strength steel plate as described in any one of claims 1 to 8.

10. The hot-rolled high-strength steel according to claim 9, characterized in that: The tensile strength level is 500MPa~700MPa, and the thickness specification is 2.0mm~12.0mm.

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