Low-cost flaw detection guaranteeing container plate and production method thereof

Abstract

The invention discloses a low-cost flaw detection guaranteed container plate and a production method thereof. The container plate comprises the following chemical components: 0.14 to 0.20 percent of C, less than or equal to 0.40 percent of Si, 1.20 to 1.30 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.010 percent of S, 0.004 to 0.025 percent of Als, 0.10 to 0.20 percent of Cr, 0.08 to 0.15 percent of Ca / Als and the balance of Fe and inevitable impurities. The carbon equivalent CEV of the steel plate is 0.34-0.44%; the production method comprises the procedures of converter smelting, LF refining, continuous casting, hot delivery, heating, rolling and cooling. The internal grain structure of the steel plate provided by the invention is uniform, and the grain size deviation between a core part and a surface structure does not exceed 0.5 grade; and the flaw detection qualification rate is more than 98%.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a low-cost flaw detection container plate and a production method thereof. Background Art

[0002] Medium and thick plate Q345R is widely used in boiler, petrochemical industry and various pressure vessel industries. In recent years, with the widespread use of high-pressure vessels and ultra-high-pressure vessels, higher requirements have been put forward for the safety of pressure vessels; steel plates are the main material for making pressure vessels, and a good flaw detection pass rate is a key factor in ensuring the safe operation of pressure vessels.

[0003] The new national standard GB / T 713 stipulates that the Mn content of Q345R steel plate meets 1.20%~1.70%, and the S content meets 0~0.010wt%; therefore, the composition design of domestic Q345R mainly adopts high Mn or high Mn+Nb / V element combination; Mn content is 1.30~1.60wt%, Nb or V content is 0.010~0.030wt%; at the same time, most steel companies limit the S content to 0~0.005wt%; on the one hand, it leads to high smelting costs, and on the other hand, the higher the Mn content, the more serious the MnS segregation degree in the core of the steel plate, which is more likely to cause the steel plate to fail to pass the flaw detection or even the steel plate to be delaminated. In addition, in order to solve the problem of low qualified rate of steel plate flaw detection, domestic enterprises usually adopt the production method of combining post-furnace LF refining + VD (RH) process, which leads to a series of problems such as long production cycle and high cost of VD (RH) process.

[0004] The patent application with publication number CN117026064A discloses a method for manufacturing Q345R steel plate, which improves the comprehensive mechanical properties of the material by adding Nb and V microalloy elements to the steel and adding an appropriate amount of Ni element to refine the grains after normalizing. However, this method not only has high alloy cost, but also a long production cycle, and is not suitable for enterprises with compact layout of steel rolling interface.

[0005] The patent application with publication number CN110592480A discloses a thick Q345R steel plate with excellent low-temperature impact toughness in the core and a manufacturing method. By adding microalloying elements such as Nb, V, Ti, and Ni and through controlled rolling and controlled cold rolling + heat treatment normalizing + high-temperature tempering process, the heat treatment temperature, holding time and other parameters of the steel plate are accurately controlled to obtain a uniform and fine ferrite + pearlite + microalloying element precipitate metallographic structure with excellent strength and toughness ratio. This method is suitable for the production of 60-100mm specification Q345R, ensuring the uniformity of thick specification steel plates in the thickness direction, but this method has high alloy and process costs, and is not suitable for the production of container plates with specifications below 30mm, and has not fundamentally solved the current situation of low-cost flaw detection container plate production. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a low-cost flaw detection container plate and a production method thereof. By adopting a low Mn and micro Cr component design, starting from reducing the center segregation index of the ingot and improving the penetration rolling effect of the steel plate, the formation of the hard phase structure in the core of the steel plate is eliminated to the greatest extent, and the uniformity of the internal grain structure of the steel plate is improved. The grain size deviation between the core and the surface structure does not exceed 0.5 levels; the flaw detection pass rate of the steel plate is above 98%.

[0007] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is:

[0008] A low-cost flaw detection container plate, the chemical composition of which is C: 0.14-0.20%, Si≤0.40%, Mn: 1.20-1.30%, P≤0.025%, S≤0.010%, Als: 0.004-0.025%, Cr: 0.10-0.20%, Ca / Als: 0.08-0.15, the balance is Fe and unavoidable impurities; the carbon equivalent CEV of the steel plate is 0.34-0.44%.

[0009] Furthermore, the steel plate of the present invention has a thickness of 8 to 30 mm.

[0010] Furthermore, the steel plate of the present invention has a yield strength level of 360 MPa or more, an impact energy of 50 J or more at 0°C, a metallographic structure of ferrite + pearlite, and a grain size deviation between the core and surface structures of no more than 0.5 levels.

[0011] Furthermore, the flaw detection pass rate of the steel plate of the present invention is above 98%.

[0012] The functions of the alloy elements in the low-cost flaw detection container plate of the present invention are as follows:

[0013] C: C is the most basic strengthening element in steel and can be infinitely dissolved in iron. The higher the C content, the higher the strength of the steel, but the worse the plasticity and welding performance. Therefore, the C content should be reduced as much as possible while ensuring the strength to ensure the plasticity and toughness of the steel plate. The present invention controls the C content to 0.14-0.20%.

[0014] Si: Si is an important reducing agent and deoxidizing agent. It can dissolve in ferrite and austenite to improve the hardness and strength of steel. In carbon manganese steel, every 0.1% increase in silicon can increase the tensile strength of hot-rolled steel by about 7.8-8.8MPa, the yield strength by about 3.9-4.9MPa, and the elongation by about 0.5%. However, when the silicon content exceeds 0.4%, it causes a decrease in the area reduction rate, especially a significant decrease in impact toughness. On the other hand, controlling a lower Si content is beneficial to improving the surface quality of steel. Therefore, considering cost performance, the maximum Si content is controlled at 0.40%.

[0015] Mn: Mn significantly reduces the Arl temperature, bainite transformation temperature and retained austenite content, and because the alloy is cheap, it plays a role in solid solution strengthening in the composition design. However, it is easy to produce segregation and banded structure, causing abnormal structure and performance of the core of the steel plate. Therefore, the Mn content is controlled at 1.20-1.30%.

[0016] P and S: P tends to segregate at grain boundaries, reducing the plasticity and toughness of steel. It is a harmful element. Theoretically, the lower the content, the better. However, considering the cost and feasibility of smelting, P is controlled to be ≤ 0.025% and S ≤ 0.010%.

[0017] Als: It mainly plays a deoxidation role in the present invention. Too low Al content will lead to poor deoxidation of molten steel and increase the possibility of subcutaneous bubble defects in the slab. Too high Al content will cause an increase in second phase precipitates in the steel, further leading to grain boundary embrittlement and increasing the sensitivity of hot delivery cracks of the cast slab. Therefore, the Al content is controlled at 0.004-0.025%.

[0018] Cr: Cr can inhibit the formation of polygonal ferrite and pearlite and promote the formation of acicular ferrite. This structure can effectively refine the grains and has a good match between strength and toughness. It can improve the strength and hardness of carbon steel in the rolled state and make up for the strength loss caused by reducing Mn. At the same time, Cr is a low-cost alloying element, which is beneficial to reducing production costs. Studies have shown that for every 0.07% reduction in Mn, 0.022% Cr needs to be increased, so the Cr content is controlled to be 0.10-0.20%.

[0019] Ca: Adding an appropriate amount of metallic calcium to steel can process the high-melting-point brittle Al2O3 inclusions produced by aluminum deoxidation into low-melting-point calcium-aluminate spherical composite inclusions with a higher calcium content (such as 12CaO·7Al2O3, etc.), prevent nozzle nodules, promote the floating of inclusions, and improve the cleanliness of molten steel; however, adding excessive Ca will increase the CaO content of inclusions, so the Ca content is controlled at Ca / Als: 0.08~0.15%.

[0020] The method for producing a low-cost flaw detection container plate of the present invention comprises the steps of converter smelting, LF refining, continuous casting, hot delivery, heating, rolling and cooling.

[0021] Furthermore, in the converter process of the present invention, during the steel tapping process, 200-300 kg of active lime and 500-800 kg of refined synthetic slag are added to perform preliminary slag washing on the molten steel.

[0022] Adding active lime and synthetic slag during the steel-making process can, on the one hand, prevent the molten steel from absorbing air and keep the molten steel warm; on the other hand, it can speed up the reduction of slag on the surface of the molten steel and promote the rapid production of reducing slag in LF refining.

[0023] Furthermore, in the LF refining process of the present invention, the slag basicity is controlled to be 4.2-4.4, and according to the Als content in the molten steel, [Ca] / [Als] is controlled to meet 0.08-0.15, and then the net argon blowing time of the molten steel is maintained at more than 8 minutes.

[0024] Controlling the slag basicity to 4.2-4.4 can speed up the reduction treatment of ladle slag, so that the treated slag can absorb inclusions more effectively. The purpose of controlling [Ca] / [Als] to meet 0.08-0.15 is that when an appropriate amount of metallic calcium is added to the steel, the high-melting-point brittle Al2O3 inclusions produced by aluminum deoxidation can be processed into low-melting-point calcium-aluminate spherical composite inclusions (such as 12CaO·7Al2O3, etc.) with a high calcium content, preventing nozzle nodules and cleaning molten steel; in addition, since the affinity of Ca and S elements is also very strong, the strip-shaped FeS and MnS inclusions in the steel can be transformed into high-melting-point spherical (2400℃) CaS inclusions, reducing the degree of MnS center segregation. At the same time, by maintaining a clean blowing time of more than 8 minutes, about 85% of the spherical Ca-based inclusions are more easily floated and removed during the clean blowing process of the molten steel, and the remaining fine spherical inclusions will not be elongated during hot rolling, which improves the stability of the structural properties of the steel. Therefore, it is crucial to reasonably control the content of [Ca] and [Als] in the molten steel to make the number and size of Ca-based inclusions in the molten steel more reasonable to improve the cleanliness of the molten steel.

[0025] Furthermore, in the continuous casting process (260*1900mm section) of the present invention, the connection between the large ladle and the middle ladle is sealed with argon, and protective casting is adopted throughout the process; the superheat of the middle ladle is controlled at 5-25°C, and the pulling speed is 1.10-1.15M / min; a medium-strength cold water meter is used to control the water ratio to 0.45-0.47L / kg, and the water ratio of the arc section, the straightening section, and the horizontal section is 3:2:1; electromagnetic stirring is adopted in the secondary cooling zone, the current is 180-360A, and the frequency is 4-6HZ; and dynamic light pressure is adopted at the end of solidification, with a pressure reduction of 5-6mm; the ingot is cut online to detect the internal quality, and the center segregation is controlled to be better than Class C 1.0, and there are no center cracks and shrinkage holes.

[0026] Low superheat and high casting speed casting are conducive to promoting the production of equiaxed crystals and reducing center segregation. By optimizing the proportion of secondary cooling water and reducing the amount of cooling water in the subsequent straightening and horizontal sections, the heat loss of the ingot itself can be reduced; at the same time, under this water ratio, the straightening zone of the ingot is just above 912°C, which can avoid the straightening zone from falling into the third brittle zone of steel to the greatest extent, improve the crack resistance sensitivity of the ingot, and improve the surface quality of the ingot. Electromagnetic stirring in the secondary cooling zone can break the formation of the transcrystalline structure of columnar crystals during solidification, prevent columnar crystal bridging, and produce defects such as center cracks and shrinkage cavities. By using dynamic light pressure at the end of solidification, the liquid core can be redistributed, the degree of center segregation can be reduced, and the quality of the core of the ingot can be improved.

[0027] Furthermore, in the hot delivery process of the present invention, all the cut-to-size ingots are hot delivered to the middle plate heating furnace via a roller conveyor with a heat-insulating cover, and the temperature of the hot-delivered edges and corners of the ingots is ≥800°C, and the surface center temperature is ≥950°C.

[0028] Furthermore, the heating process of the present invention adopts a three-stage heating mode of preheating section, heating section and soaking section, and the total heating time is 90 to 100 minutes; wherein, the temperature of the preheating section is less than 1150°C, the temperature of the first heating section is 1200±30°C, the temperature of the second heating section is 1250±20°C, and the temperature of the soaking section is 1220±20°C; the first heating section and the second heating section are each maintained for 20 to 25 minutes, and the soaking section is maintained for 25 to 30 minutes.

[0029] Furthermore, in the rolling process of the present invention, the starting rolling temperature is controlled at 1030-1100°C, and the reduction rates of the three passes after rough rolling are all greater than 17%. The large reduction rate can break the dendrites inside the ingot and reduce the banded structure; the intermediate billet after rolling adopts an intermediate cooling system IC to control the temperature difference between the surface and the core of the steel plate to be ≥60°C; the surface of the intermediate billet is rapidly cooled to promote the formation of a fine crystal layer on the surface of the intermediate billet, making the intermediate billet hard on the outside and soft on the inside, which is convenient for the deformation in the finishing stage to penetrate into the inside and achieve uniformity of the structure in the thickness direction; the final temperature of the waiting temperature is ≤900°C, the waiting temperature thickness is ≥60mm, and the final rolling temperature is controlled at 790-880°C.

[0030] The final waiting temperature is controlled at ≤900℃ and the final rolling temperature is controlled at 790~880℃ to ensure that the deformation of the steel plate is always carried out in the non-recrystallization zone, reduce the mixed crystals inside the steel plate, and facilitate the homogenization of the core and surface structure of the steel plate; the thickness of the steel plate during the second stage rolling is controlled to be ≥1.8a, so that the cumulative reduction rate can be ≥80%, thereby obtaining a large number of accumulated dislocations and deformation bands, increasing nucleation points, refining grains, and dispersing the concentrated distribution of pearlite, thereby reducing the banded structure grade of the strip and improving the flaw detection performance of the steel plate.

[0031] Furthermore, in the cooling process of the present invention, the cooling water is turned on before the steel plate reaches laminar cooling, ACC cooling is adopted, 3 to 11 water groups are turned on, the cooling rate is 5 to 10°C / s, and the final cooling temperature is controlled at 650 to 700°C.

[0032] According to the thickness of the steel plate and the secondary calculation model, different ACC water groups and cooling rates can be used to accurately control the final cooling temperature of the steel plate at 650-700°C. The cooling rate is controlled at 5-10°C / s to ensure that the steel plate is fully transformed into ferrite and pearlite structures in the thickness direction, thereby ensuring the uniformity of the structure in the thickness direction of the steel plate; avoid the formation of overcooled structures on the surface of the steel plate due to excessive local cooling rate.

[0033] The beneficial effects of adopting the above technical solution are:

[0034] The present invention adopts a low Mn and low Cr composition design, starts from reducing the center segregation index of the ingot and improving the penetration rolling effect of the steel plate, thereby preventing the formation of hard phase structure in the core of the steel plate to the greatest extent, improving the uniformity of the internal grain structure of the steel plate, and the grain size deviation between the core and the surface structure does not exceed 0.5 levels; the steel plate flaw detection pass rate reaches more than 98%.

[0035] The method of the invention has the advantages of low cost and simple production process, can realize stable production of single refining of ingot and stable internal quality of steel plate, with strength level above 360Mpa and impact energy above 50J at 0℃, and product specifications covering 8-30mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a 100× microstructure image (near the surface) of the 8 mm thick container plate in Example 1;

[0037] Figure 2 It is a 100× microstructure image (thickness center) of the 8 mm thick container plate in Example 1;

[0038] Figure 3 This is a 100× microstructure image (near the surface) of the container plate with a thickness of 16 mm in Example 2;

[0039] Figure 4 It is a 100× microstructure image (thickness center) of the container plate with a thickness of 16 mm in Example 2;

[0040] Figure 5 This is a 100× microstructure image (near the surface) of the container plate with a thickness of 20 mm in Example 3;

[0041] Figure 6 This is a 100× microstructure image (thickness center) of a container plate with a thickness of 20 mm in Example 3;

[0042] Figure 7 This is a 100× microstructure image (near the surface) of the container plate with a thickness of 25 mm in Example 4;

[0043] Figure 8 is a 100× microstructure image (thickness center) of a container plate with a thickness of 25 mm in Example 4;

[0044] Fig. 9 This is a 100× microstructure image (near the surface) of the 30 mm thick container plate in Example 5;

[0045] Fig.10 It is a 100× microstructure image (thickness center) of the 30 mm thick container plate in Example 5;

[0046] Fig.11 This is a 100× microstructure image (near the surface) of the container plate with a thickness of 12 mm in Example 6;

[0047] Fig.12 This is a 100× microstructure image (center of thickness) of the 12 mm thick container plate in Example 6. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is further described in detail below through embodiments.

[0049] Examples 1-6

[0050] The chemical composition and mass percentage (wt%) of the low-cost flaw detection container plate of each embodiment are shown in Table 1.

[0051] Table 1 Chemical composition and content (wt%) of ultra-low microalloyed steel sheets of various embodiments

[0052] Example C Si Mn P S Als Cr Ca Ca / Al CEV 1 0.14 0.20 1.20 0.025 0.008 0.010 0.15 0.0015 0.15 0.34 2 0.16 0.25 1.30 0.015 0.010 0.004 0.20 0.0005 0.13 0.38 3 0.18 0.15 1.25 0.018 0.005 0.025 0.18 0.0025 0.1 0.39 4 0.20 0.20 1.30 0.021 0.008 0.015 0.15 0.0012 0.08 0.44 5 0.16 0.18 1.28 0.020 0.005 0.021 0.20 0.0017 0.08 0.37 6 0.15 0.33 1.22 0.017 0.006 0.019 0.10 0.0022 0.12 0.35

[0053] The production method of low-cost flaw detection container plates in each embodiment includes converter smelting, LF refining, continuous casting, hot delivery, heating, rolling, and cooling processes; the details are as follows:

[0054] (1) Converter smelting: During the steelmaking process, 200-300 kg of active lime and 500-800 kg of refined synthetic slag are added to perform preliminary slag washing on the molten steel.

[0055] (2) LF refining: The slag basicity is controlled at 4.2-4.4, and the [Ca] / [Als] is controlled to meet 0.08-0.15 according to the Als content in the molten steel. The net argon blowing time of the molten steel is then maintained at more than 8 minutes.

[0056] The parameters of the converter and LF refining and smelting processes in the embodiment are shown in Table 2.

[0057] Table 2 Parameters of converter and LF refining and smelting process in various embodiments

[0058]

[0059] (3) Continuous casting: 260*1900mm section, argon is used to seal the connection between the large and medium ladle, and protective pouring is adopted throughout the process; the superheat of the medium ladle is controlled at 5~25℃, and the casting speed is 1.10~1.15M / min; 5#~10# medium-strength cold water meters are used to control the water ratio to 0.45~0.47L / kg, and the water ratio of the arc section, straightening section, and horizontal section is 3:2:1; electromagnetic stirring is adopted in the secondary cooling zone, the current is 180~360A, and the frequency is 4~6HZ; and dynamic light pressure is adopted at the end of solidification, with a pressure reduction of 5~6mm; the ingot is cut online to detect the internal quality, and the central segregation is controlled to be better than Class C 1.0, and there is no central crack and shrinkage cavity.

[0060] (4) Hot delivery: All cut-to-size ingots are hot delivered to the middle plate heating furnace via a roller conveyor with a heat-insulating cover. The temperature of the edges and corners of the ingots during hot delivery is ≥800°C, and the temperature of the center of the surface is ≥950°C.

[0061] The process parameters of continuous casting and high temperature hot delivery of ingots in each embodiment are shown in Table 3.

[0062] Table 3 Parameters of continuous casting and high temperature hot delivery process of each embodiment

[0063]

[0064] (5) Heating: A three-stage heating mode of preheating, heating and soaking is adopted, and the total heating time is 90 to 100 minutes; wherein, the temperature of the preheating stage is less than 1150°C, the temperature of the first heating stage is 1200±30°C, the temperature of the second heating stage is 1250±20°C, and the temperature of the soaking stage is 1220±20°C; the first heating stage and the second heating stage are each maintained for 20 to 25 minutes, and the soaking stage is maintained for 25 to 30 minutes. The heating process parameters of each embodiment are shown in Table 4.

[0065] Table 4 Heating process parameters of each embodiment

[0066]

[0067] (6) Rolling: The starting rolling temperature is controlled at 1030-1100℃, and the reduction ratio of the three passes after rough rolling is greater than 17%. The intermediate billet after rolling adopts the intermediate cooling system IC, and the temperature difference between the surface and the core of the steel plate is controlled to be ≥60℃, the final temperature of the waiting temperature is ≤900℃, the waiting temperature thickness is ≥60mm, and the final rolling temperature is controlled at 790-880℃.

[0068] (7) Cooling: Before the steel plate reaches laminar cooling, the cooling water is turned on, and ACC cooling is adopted. Water groups 3 to 11 are turned on, the cooling rate is 5 to 10 °C / s, and the final cooling temperature is controlled at 650 to 700 °C.

[0069] The rolling and cooling process parameters of each embodiment are shown in Table 5.

[0070] Table 5 Rolling and cooling process parameters of each embodiment

[0071]

[0072] The performance quality of the container plate of each embodiment was tested, and the results are shown in Table 6.

[0073] Table 6 Performance quality test results of container plates in various embodiments

[0074]

[0075] It can be seen from Table 6 that the mechanical properties of the container plate provided by the present invention fully meet the requirements of the national standard GB / T 713. The microstructures of the container plates near the surface and at the thickness center of each embodiment are shown in Table 6. Figures 1 to 12 ;Depend on Figures 1 to 12 It can be seen that the grain sizes of the surface and core of the steel plate provided by the present invention are uniform, and the microstructures are all ferrite+pearlite.

Claims

1. A low-cost flaw detection container plate, characterized in that: The chemical composition of the container plate is C: 0.14-0.20%, Si≤0.40%, Mn: 1.20-1.30%, P≤0.025%, S≤0.010%, Als: 0.004-0.025%, Cr: 0.10-0.20%, Ca / Als: 0.08-0.15, and the balance is Fe and unavoidable impurities; Its carbon equivalent CEV is 0.34~0.44%.

2. A low-cost flaw detection container plate according to claim 1, characterized in that: The container plate has a thickness of 8 to 30 mm.

3. A low-cost flaw detection container plate according to claim 1, characterized in that: The yield strength level of the container plate is above 360Mpa, the impact energy at 0°C is above 50J, the metallographic structure is ferrite + pearlite, the grain size deviation between the core and the surface structure does not exceed 0.5 levels; the flaw detection pass rate is above 98%.

4. A method for producing a low-cost flaw detection container plate according to any one of claims 1 to 3, characterized in that: It includes converter smelting, LF refining, continuous casting, hot delivery, heating, rolling and cooling processes; in the LF refining process, the slag basicity is controlled at 4.2-4.4, and according to the Als content in the molten steel, [Ca] / [Als] is controlled to meet 0.08-0.15, and then the net argon blowing time of the molten steel is maintained at more than 8 minutes.

5. A method for producing a low-cost flaw detection container plate according to claim 4, characterized in that: In the converter process, during the steel tapping process, 200-300 kg of active lime and 500-800 kg of refined synthetic slag are added to perform preliminary slag washing on the molten steel.

6. A method for producing a low-cost flaw detection container plate according to claim 4, characterized in that: In the continuous casting process, the connection between the large ladle and the middle ladle is sealed with argon, and protective casting is adopted throughout the whole process; the superheat of the middle ladle is controlled at 5-25°C, and the casting speed is 1.10-1.15M / min; a medium-strength cold water meter is used to control the water ratio to 0.45-0.47L / kg, and the water ratio of the arc section, the straightening section, and the horizontal section is 3:2:1; electromagnetic stirring is adopted in the second cooling zone, the current is 180-360A, and the frequency is 4-6HZ; and dynamic light pressure is adopted at the end of solidification, and the pressure reduction amount is 5-6mm.

7. A method for producing a low-cost flaw detection container plate according to claim 4, characterized in that: In the hot delivery process, all the cut-to-size ingots are hot delivered to the middle plate heating furnace via a roller conveyor with a heat-insulating cover. The temperature of the hot-delivered edges and corners of the ingots is ≥800°C, and the surface center temperature is ≥950°C.

8. A method for producing a low-cost flaw detection container plate according to claim 4, characterized in that: The heating process adopts a three-stage heating mode of preheating section, heating section and soaking section, and the total heating time is 90 to 100 minutes; wherein, the temperature of the preheating section is less than 1150°C, the temperature of the first heating section is 1200±30°C, the temperature of the second heating section is 1250±20°C, and the temperature of the soaking section is 1220±20°C; the first heating section and the second heating section are each maintained for 20 to 25 minutes, and the soaking section is maintained for 25 to 30 minutes.

9. A method for producing a low-cost flaw detection container plate according to claim 4, characterized in that: In the rolling process, the starting rolling temperature is controlled at 1030-1100°C, and the reduction rates of the three passes after rough rolling are all greater than 17%; the intermediate billet after rolling adopts an intermediate cooling system IC to control the temperature difference between the surface and the core of the steel plate to be ≥60°C, the final waiting temperature is ≤900°C, the waiting thickness is ≥60mm, and the final rolling temperature is controlled at 790-880°C.

10. A method for producing a low-cost flaw detection container plate according to claim 4, characterized in that: In the cooling process, the cooling water is turned on before the steel plate reaches laminar cooling, ACC cooling is adopted, 3 to 11 water groups are turned on, the cooling rate is 5 to 10°C / s, and the final cooling temperature is controlled at 650 to 700°C.

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