Production method of low-welding-crack-sensitivity rare earth microalloyed 07MnNiMoDR steel plate for storage tank

Abstract

The invention discloses a production method of a low-welding-crack-sensitivity rare earth microalloying 07MnN iMoDR steel plate for a storage tank. The production method comprises the steps of KR desulfurization, converter smelting, LF refining, RH refining, continuous casting, heat preservation pit slow cooling, heating, rolling, cooling, hot straightening, shearing, flaw detection, hardening and tempering and sampling inspection. The C-Mn component design is adopted, a proper amount of Mn, Mo, Ni and Cr elements, V, Ti and rare earth element microalloying narrow component control is added, the performance stability of the thick steel plate for the storage tank is improved, meanwhile, the welding crack sensitivity is reduced, the welding performance of the steel plate is improved, the process design window is widened, the batch production efficiency is improved, and the 40-50 mm steel plate for the storage tank is stably produced in batches. The steel plate is excellent in mechanical property, the ductility is larger than 20%, the impact energy of the steel plate at the temperature of 50 DEG C below zero can reach 180 J or above, and the welding joint crack sensitivity index Pcm is smaller than 0.20%.

Description

Technical Field

[0001] The invention belongs to the technical field of hot rolling, and in particular relates to a method for producing a rare earth microalloyed 07MnNiMoDR ​​steel plate for a storage tank with low welding crack sensitivity. Background Art

[0002] 07MnNiMoDR ​​quenched and tempered high-strength steel plates for low crack sensitivity pressure vessels are mainly used to manufacture spherical tanks that match their service temperatures, and are mainly used to manufacture cryogenic spherical tanks for different media and volumes such as oxygen, nitrogen, propylene, and ethylene.

[0003] The document "Study on Heat Treatment Process, Organization and Properties of 07MnNiMoDR ​​Steel" analyzes the changes in the microstructure and low-temperature properties of 07MnNiMoDR ​​steel under different heat treatment processes (quenching, tempering, simulated post-weld heat treatment), which is a laboratory study; this patent provides a method for producing rare earth micro-alloyed 07MnNiMoDR ​​tank steel plates with low welding crack sensitivity, clarifies the specific production process, and is suitable for mass production.

[0004] The document "07MnNiMoVDR Pressure Vessel Steel Production Process and Microstructure Performance" provides a production method for 07MnNiMoVDR with a thickness of 12-27mm. This method provides a production method for 07MnNiMoVDR rare earth microalloyed quenched and tempered steel plate with a thickness of 40-50mm. The addition of rare earth reduces the sensitivity of low welding cracks. The production process of slab quenching + hot charging reduces the manufacturing cost. Compared with the above patented process, it is stable, easy to control, and has excellent low-temperature toughness and weldability.

[0005] The document "Study on the Microstructure and Properties of Low Welding Crack Sensitivity Steel 07MnNiMoDR" provides a heat treatment and tempering process for 07MnNiMoVDR with a thickness of 48mm; this method provides a full-process production process for 07MnNiMoVDR rare earth micro-alloyed quenched and tempered steel plate, which is more suitable for the refined process control of wide and thick plate production and improves the stability of product mass production.

[0006] As the strength of steel plates increases, their welding performance decreases significantly and the sensitivity of welding cracks increases. In particular, as the welding line energy increases, the performance of the welding heat affected zone of traditional low-alloy high-strength steel deteriorates. Generally, high-strength plates need to be welded before use. At present, improving welding efficiency and reducing welding costs through high line energy welding has become a hot trend in the field of pressure vessels. In order to improve the performance of the heat affected zone of thick plate welding, rare earth steel plates use fine, dispersed, and composition-controlled oxide inclusions generated during the steelmaking process to change the organization and grain size of the steel and improve the welding performance of the steel. Rare earth oxides delay the bainite transformation during welding and inhibit the formation of upper bainite structure. On the other hand, fine rare earth oxide inclusions inhibit the growth of austenite grains. In addition, previous studies on the effects of different rare earth, oxygen and sulfur contents on inclusions in steel and the effects of rare earth inclusions on austenite grain boundaries have shown that controlling the formation of rare earth sulfides in steel is more conducive to improving the toughness of the welding heat affected zone than rare earth oxide, rare earth aluminate and rare earth oxysulfide inclusions. In view of the above principles, through a large number of experimental studies, it is proposed that the welding crack sensitivity index Pcm of steel plates with low welding crack sensitivity be revised as follows:

[0007] Pcm(%)=C+Si / 30+(Mn+Cu+Cr) / 20+Ni / 60+Mo / 15+V / 10+5B-120Ce Summary of the invention

[0008] The purpose of the present invention is to provide a method for producing a rare earth microalloyed 07MnNiMoDR ​​tank steel plate with low welding crack sensitivity, which adopts a quenching and tempering heat treatment process, adopts a low-carbon component design, adds appropriate amounts of Mn, Mo, Ni, Cr elements, V, Ti and rare earth elements for microalloying narrow component control, and accurately controls the rolling and heat treatment processes to ensure that the steel plate has low welding crack sensitivity and excellent comprehensive performance, especially the low-temperature toughness meets the high standards of users.

[0009] The present invention clarifies the batch production process of the entire process through the production process of slab quenching + hot charging.

[0010] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0011] The present invention discloses a method for producing a rare earth microalloyed 07MnNiMoDR ​​steel plate for a storage tank with low welding crack sensitivity, comprising:

[0012] 1) The tapping temperature of the converter is 1620-1660℃, and the single slag process is adopted for smelting. The converter adopts single slag operation, uses high-quality active lime, and the final slag basicity is controlled at 3.0-3.5; and self-produced high-quality scrap steel is used to reduce the [S] brought in by scrap steel; the bottom blowing gas of the converter adopts the full-process argon blowing mode, and the end point is hit as much as possible in one time to reduce the increase of nitrogen in the molten steel due to supplementary blowing;

[0013] 2) Refining accurately controls the composition, and the amount of white ash added is ≥5kg / ton of steel. The slag sample must be dipped during the refining process to ensure that the white slag is quickly formed and kept for a certain period of time;

[0014] 3) The molten steel is subjected to RH furnace treatment, the RH vacuum treatment time is not less than 20 minutes, the pure degassing time is not less than 5 minutes, the minimum vacuum degree is 260Pa, and the off-site hydrogen content is less than or equal to 2.0ppm;

[0015] 4) In order to ensure the quality of slabs with a certain compression ratio, 300mm thick continuous casting slabs are selected, the center segregation of the slab is not greater than B1.0, the center looseness is not greater than 2.5, and the middle crack is not greater than 1.0; the superheat during continuous casting molten steel casting is controlled at 15-26℃, the argon blowing pressure of the long nozzle is ≥0.1Mpa, the argon blowing standby pressure gauge flow rate of the tundish submerged nozzle plate reaches 6-10L / min, the standby pressure gauge pressure is 0.1-0.5Bar, and the casting machine pulling speed is 0.9-1.1m / min;

[0016] 5) Optimize and adjust the acceleration time of the roller in the quenching beam, so that the slab surface quenching cooling time is controlled at 180S-250S, and design 16 sets of quenching cooling water beams; the cooling time is slow cooling time ≤250min, the slab furnace temperature is 550-620℃, the total furnace time is ≥150min, and the slab is heated in a three-stage walking beam heating furnace. The heating temperature of the first heating section is 1100-1150℃, and the heating time is 40-60 minutes; the heating temperature of the second heating section is 1200-1280℃, and the heating time is 40-60min; the ambulation temperature is 1230-1300℃, the heating time is ≥30min, the total heating time is not less than 150min, and the slab furnace temperature is 1160-1220℃;

[0017] 6) Rolling and cooling process: After the slab is heated, two-stage controlled rolling is carried out. The first stage rolling is completed on the rough rolling mill. The first stage rolling thickness is the slab thickness. The first stage rolling temperature is 1150-1190℃. The set torque is 2400kNm, the set reduction is 32mm, the rolling speed is 2.1-3.4m / s, and the single pass reduction rate in the high temperature extension stage is not less than 18%; the second stage rolling is completed on the finishing mill. The second stage rolling temperature is 890-950℃, and the second stage rolling thickness is 50-1 25mm, the second stage final rolling temperature is 820-870℃, the second stage rolling torque is set to 2200kNm, the rolling force is set to 85MN, the reduction is set to 20mm, and the final reduction rate is 5%-10% to ensure the plate shape; after the steel plate is rolled, laminar cooling is carried out, the ACC water temperature is 17-20℃, the cooling rate is 10-15℃ / s, the final cooling temperature is 590-630℃, generally the head is shielded by 0-2.0m, the tail is shielded by 0-2.5m, and the edge is shielded by 0-2.0m, and the overall temperature difference of the steel plate after returning to red is controlled to be ≤50℃;

[0018] 7) Heat treatment process: Shot blasting is required before quenching of the steel plate. The quenching and holding temperature is 900-920℃, the quenching and holding time is more than 10 minutes, and water cooling is adopted; the tempering and holding temperature is 600-650℃, the tempering and holding time is more than 20 minutes, and air cooling is adopted;

[0019] The chemical composition of the steel plate by mass percentage includes: C: 0.06-0.08%, Si: 0.20-0.30%, Mn: 1.40-1.60%, P: ≤0.010%, S: ≤0.005%, Als: 0.015-0.032%, Ni: 0.20-0.30%, Cr: 0.15-0.25%, V: 0.035-0.045%, Mo: 0.15-0.25%, Ce: ≤0.0020%, H≤1.7ppm, O: ≤0.0050%, N: ≤0.0060%; the rest is iron and unavoidable impurities.

[0020] Furthermore, the thickness of the steel plate is 40mm-50mm.

[0021] Furthermore, the chemical composition of the steel plate by mass percentage includes: C: 0.07, Si: 0.26, Mn: 1.51, P: 0.007, S: 0.002, Als: 0.026, Ni: 0.23, Cr: 0.20, V: 0.039, Mo: 0.22, Ce: 0.0005, H: 1.0ppm, O: 0.0029, N: 0.0041, Pcm: 0.13; the remainder is Fe and unavoidable impurities.

[0022] Furthermore, the chemical composition of the steel plate by mass percentage includes: C: 0.06, Si: 0.27, Mn: 1.53, P: 0.008, S: 0.002, Als: 0.028, Ni: 0.26, Cr: 0.22, V: 0.038, Mo: 0.17, Ce: 0.0004, H: 1.0ppm, O: 0.0030, N: 0.0040, Pcm: 0.13; the remainder is Fe and unavoidable impurities.

[0023] Furthermore, the chemical composition of the steel plate by mass percentage includes: C: 0.08, Si: 0.27, Mn: 1.54, P: 0.007, S: 0.001, Als: 0.029, Ni: 0.27, Cr: 0.21, V: 0.035, Mo: 0.22, Ce: 0.0002, H≤0.9ppm, O:≤0.0024, N:≤0.0035, Pcm: 0.18; the remainder is Fe and unavoidable impurities.

[0024] Furthermore, the structure of the produced steel plate at T / 4 is mainly tempered bainite and bainite, and the structure at T / 2 is mainly bainite. The structure is fine and uniform, and the grain size is 9-11.

[0025] Furthermore, the produced steel plates have good crack arresting ability, which ensures the reliability of the material during use.

[0026] Compared with the prior art, the beneficial technical effects of the present invention are:

[0027] (1) The thickness of the steel plate is 40mm-50mm;

[0028] (2) Proper alloying of the steel plate reduces the alloy cost while ensuring the performance of the steel plate;

[0029] (3) The slab adopts quenching process and is directly warm-loaded, which reduces energy consumption and improves performance stability;

[0030] (4) The addition of appropriate amount of rare earth elements reduces the welding crack sensitivity coefficient and improves the welding performance of the steel plate;

[0031] The outstanding advantage of the present invention is that it adopts C-Mn composition design, adds appropriate amounts of Mn, Mo, Ni, Cr elements, V, Ti and rare earth elements to control the narrow composition of microalloying, improves the performance stability of thick specification storage tank steel plates, reduces the sensitivity of welding cracks, improves the welding performance of steel plates, broadens the process design window, improves batch production efficiency, and stably produces 40mm-50mm storage tank steel plates. After actual production and inspection, its mechanical properties are excellent, the strength of the steel plates in each embodiment meets the standard requirements, the elongation is greater than 20%, the impact energy of the steel plate at -50℃ can reach more than 180J, and the welding crack sensitivity index Pcm is less than 0.20%. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described below in conjunction with the accompanying drawings.

[0033] Figure 1 This is a metallographic photo of a 50mm steel plate;

[0034] Figure 2 This is the scanning electron microscope structure of a 50mm steel plate;

[0035] Figure 3 This is the CTOD curve of 40mm steel plate (-20℃). DETAILED DESCRIPTION

[0036] The present invention is further described below with reference to the embodiments.

[0037] Example 1

[0038] The surface quenching cooling time of the slab is controlled at 190S, and the slab is directly warm loaded into the heating furnace, the heating time is 180 minutes, and the soaking time is 35 minutes. The mass percentage of the chemical composition of the slab is C: 0.07, Si: 0.26, Mn: 1.51, P: 0.007, S: 0.002, Als: 0.026, Ni: 0.23, Cr: 0.20, V: 0.039, Mo: 0.22, Ce: 0.0005, H: 1.0ppm, O: 0.0029, N: 0.0041, Pcm: 0.13; the balance is Fe and unavoidable impurities. The steel plate with a thickness of 40mm is rolled. The detailed rolling process is shown in Table 1, and its mechanical properties are shown in Table 2.

[0039] Example 2

[0040] The surface quenching cooling time of the slab is controlled at 205S, and the slab is directly warm loaded into the heating furnace, the heating time is 168 minutes, and the soaking time is 40 minutes. The mass percentage of the chemical composition of the slab is: C: 0.06, Si: 0.27, Mn: 1.53, P: 0.008, S: 0.002, Als: 0.028, Ni: 0.26, Cr: 0.22, V: 0.038, Mo: 0.17, Ce: 0.0004, H: 1.0ppm, O: 0.0030, N: 0.0040, Pcm: 0.13; the balance is Fe and unavoidable impurities. The steel plate with a thickness of 45mm is rolled. The detailed rolling process is shown in Table 1, and its mechanical properties are shown in Table 2.

[0041] Example 3

[0042] The surface quenching cooling time of the slab is controlled at 222S, and the slab is directly warm-charged into the heating furnace, the heating time is 204 minutes, and the soaking time is 48 minutes. The mass percentage of the chemical composition of the slab is: C: 0.08, Si: 0.27, Mn: 1.54, P: 0.007, S: 0.001, Als: 0.029, Ni: 0.27, Cr: 0.21, V: 0.035, Mo: 0.22, Ce: 0.0002, H≤0.9ppm, O:≤0.0024, N:≤0.0035, Pcm: 0.18; the balance is Fe and unavoidable impurities. The steel plate with a thickness of 50mm is rolled. The detailed rolling and heat treatment process is shown in Table 1, and its mechanical properties are shown in Table 2.

[0043] The chemical composition and mechanical properties of the quenched and tempered 40-50mm low welding crack sensitivity rare earth storage tank steel plate produced by this composition and process design meet the requirements of the national standard GB 19189-2011 quenched and tempered high-strength steel plate for pressure vessels. It has appropriate strength, low yield strength ratio, excellent elongation, and especially outstanding low-temperature impact performance. Users report that the welding performance is excellent.

[0044] Table 1 Process parameters of Examples 1-4

[0045]

[0046] Table 2 Mechanical properties of Examples 1-4

[0047]

[0048]

[0049] The structure of the 50mm trial steel plate of the present invention at T / 4 is mainly tempered troostite and bainite, and the structure at T / 2 is mainly bainite. The structure is fine and uniform, and the grain size is 9-11. The specific metallographic photos are as follows Figure 1 .

[0050] Figure 2 This is the scanning electron microscope structure. It can be seen from the figure that the structure of the 50mm trial steel plate at T / 4 is mainly tempered bainite and bainite, and the structure at T / 2 is mainly bainite.

[0051] Non-plastic transition temperature test

[0052] The NDTT test was carried out according to GB / T6803 standard. The test results are shown in Table 3.

[0053] Table 3 Test results of non-plastic transition temperature

[0054]

[0055] It can be seen from Table 3 that the NDTT temperature of the trial steel plate is between -45℃ and -55℃, and the NDTT temperature of the 07MnMoVR steel plate is lower.

[0056] Crack Tip Opening Displacement (CTOD) Test

[0057] Crack tip opening displacement CTOD is the most effective method for fracture mechanics analysis of ductile materials (selecting materials to specify tolerance defect size, determining stress level and conducting fracture accident analysis). It is suitable for crack initiation and slow steady-state expansion of defective structures. For pressure vessel steel, its ability to resist crack initiation and steady-state expansion is an important indicator to ensure the safety of pressure vessels.

[0058] The CTOD test of crack tip opening displacement at low temperature (-20℃) was carried out on 40mm thick 07MnMoVR steel plate, and the sample was sampled horizontally. The test results are shown in Table and. The results show that the trial steel plate has good crack arrest ability, which ensures the reliability of the material during use.

[0059] Table 4 CTOD test results of 07MnMoVR 40mm steel plate at low temperature (-20℃)

[0060] B(mm) W(mm) a(mm) Δa(mm) P(kN) VP(mm) <![CDATA[δ R ]]> 25.00 30.04 15.11 0.08 44.1 0.73 0.251 25.04 30.03 15.03 0.17 47.9 1.10 0.363 25.02 30.02 14.89 0.22 47.7 1.25 0.407 25.01 30.04 15.02 0.31 48.1 1.68 0.526 25.01 30.03 15.07 0.38 48.8 2.21 0.673 25.03 30.00 15.00 0.46 51.2 2.84 0.858 25.03 30.02 15.14 0.61 51.8 3.28 0.973

[0061] Note: R =1.457(0.079+Δa); R=0.991; δ 0.05 =0.19(mm);δ 0.20 =0.41(mm)

[0062] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing a rare earth microalloyed 07MnNiMoDR ​​tank steel plate with low welding crack sensitivity, characterized in that: include: 1) The tapping temperature of the converter is 1620-1660℃, and the single slag process is adopted for smelting. The converter adopts single slag operation, uses high-quality active lime, and the final slag basicity is controlled at 3.0-3.5; and self-produced high-quality scrap steel is used to reduce the [S] brought in by scrap steel; the bottom blowing gas of the converter adopts the full-process argon blowing mode, and the end point is hit as much as possible in one time to reduce the increase of nitrogen in the molten steel due to supplementary blowing; 2) Refining accurately controls the composition, and the amount of white ash added is ≥5kg / ton of steel. The slag sample must be dipped during the refining process to ensure that the white slag is quickly formed and kept for a certain period of time; 3) The molten steel is subjected to RH furnace treatment, the RH vacuum treatment time is not less than 20 minutes, the pure degassing time is not less than 5 minutes, the minimum vacuum degree is 260Pa, and the off-site hydrogen content is less than or equal to 2.0ppm; 4) In order to ensure the quality of slabs with a certain compression ratio, 300mm thick continuous casting slabs are selected, the center segregation of the slab is not greater than B1.0, the center looseness is not greater than 2.5, and the middle crack is not greater than 1.0; the superheat during continuous casting molten steel casting is controlled at 15-26℃, the argon blowing pressure of the long nozzle is ≥0.1Mpa, the argon blowing standby pressure gauge flow rate of the tundish submerged nozzle plate reaches 6-10L / min, the standby pressure gauge pressure is 0.1-0.5Bar, and the casting machine pulling speed is 0.9-1.1m / min; 5) Optimize and adjust the acceleration time of the roller in the quenching beam, so that the slab surface quenching cooling time is controlled at 180S-250S, and design 16 sets of quenching cooling water beams; the cooling time is slow cooling time ≤250min, the slab furnace temperature is 550-620℃, the total furnace time is ≥150min, and the slab is heated in a three-stage walking beam heating furnace. The heating temperature of the first heating section is 1100-1150℃, and the heating time is 40-60 minutes; the heating temperature of the second heating section is 1200-1280℃, and the heating time is 40-60min; the ambulation temperature is 1230-1300℃, the heating time is ≥30min, the total heating time is not less than 150min, and the slab furnace temperature is 1160-1220℃; 6) Rolling and cooling process: After the slab is heated, two-stage controlled rolling is carried out. The first stage rolling is completed on the rough rolling mill. The first stage rolling thickness is the slab thickness. The first stage rolling temperature is 1150-1190℃. The set torque is 2400kNm, the set reduction is 32mm, the rolling speed is 2.1-3.4m / s, and the single pass reduction rate in the high temperature extension stage is not less than 18%; the second stage rolling is completed on the finishing mill. The second stage rolling temperature is 890-950℃, and the second stage rolling thickness is 50-1 25mm, the second stage final rolling temperature is 820-870℃, the second stage rolling torque is set to 2200kNm, the rolling force is set to 85MN, the reduction is set to 20mm, and the final reduction rate is 5%-10% to ensure the plate shape; after the steel plate is rolled, laminar cooling is carried out, the ACC water temperature is 17-20℃, the cooling rate is 10-15℃ / s, the final cooling temperature is 590-630℃, generally the head is shielded by 0-2.0m, the tail is shielded by 0-2.5m, and the edge is shielded by 0-2.0m, and the overall temperature difference of the steel plate after returning to red is controlled to be ≤50℃; 7) Heat treatment process: Shot blasting is required before quenching of the steel plate. The quenching and holding temperature is 900-920℃, the quenching and holding time is more than 10 minutes, and water cooling is adopted; the tempering and holding temperature is 600-650℃, the tempering and holding time is more than 20 minutes, and air cooling is adopted; The welding crack sensitivity index Pcm of the low welding crack sensitivity rare earth microalloyed 07MnNiMoDR ​​tank steel plate is revised as follows: Pcm(%)=C+Si / 30+(Mn+Cu+Cr) / 20+Ni / 60+Mo / 15+V / 10+5B-120Ce; The chemical composition of the steel plate by mass percentage includes: C: 0.06~0.08%, Si: 0.20~0.30%, Mn: 1.40~1.60%, P: ≤0.010%, S: ≤0.005%, Als: 0.015~0.032%, Ni: 0.20~0.30%, Cr: 0.15~0.25%, V: 0.035~0.045%, Mo: 0.15~0.25%, Ce: ≤0.0020%, H≤1.7ppm, O: ≤0.0050%, N: ≤0.0060%; the rest are iron and unavoidable impurities.

2. The method for producing the rare earth microalloyed 07MnNiMoDR ​​tank steel plate with low welding crack sensitivity according to claim 1, characterized in that: The thickness of the steel plate is 40mm-50mm.

3. The method for producing the rare earth microalloyed 07MnNiMoDR ​​tank steel plate with low welding crack sensitivity according to claim 1, characterized in that: The chemical composition of the steel plate by mass percentage includes: C: 0.07, Si: 0.26, Mn: 1.51, P: 0.007, S: 0.002, Als: 0.026, Ni: 0.23, Cr: 0.20, V: 0.039, Mo: 0.22, Ce: 0.0005, H: 1.0ppm, O: 0.0029, N: 0.0041, Pcm: 0.13; the balance is Fe and unavoidable impurities.

4. The method for producing the rare earth microalloyed 07MnNiMoDR ​​tank steel plate with low welding crack sensitivity according to claim 1, characterized in that: The chemical composition of the steel plate by mass percentage includes: C: 0.06, Si: 0.27, Mn: 1.53, P: 0.008, S: 0.002, Als: 0.028, Ni: 0.26, Cr: 0.22, V: 0.038, Mo: 0.17, Ce: 0.0004, H: 1.0ppm, O: 0.0030, N: 0.0040, Pcm: 0.13; the balance is Fe and unavoidable impurities.

5. The method for producing the rare earth microalloyed 07MnNiMoDR ​​tank steel plate with low welding crack sensitivity according to claim 1, characterized in that: The chemical composition of the steel plate by mass percentage includes: C: 0.08, Si: 0.27, Mn: 1.54, P: 0.007, S: 0.001, Als: 0.029, Ni: 0.27, Cr: 0.21, V: 0.035, Mo: 0.22, Ce: 0.0002, H≤0.9ppm, O:≤0.0024, N:≤0.0035, Pcm: 0.18; the balance is Fe and unavoidable impurities.

6. The method for producing the rare earth microalloyed 07MnNiMoDR ​​tank steel plate with low welding crack sensitivity according to claim 1, characterized in that: The structure of the steel plate produced is mainly tempered troostite and bainite at T / 4, and mainly bainite at T / 2. The structure is fine and uniform, with a grain size of 9-11.

7. The method for producing the rare earth microalloyed 07MnNiMoDR ​​tank steel plate with low welding crack sensitivity according to claim 1, characterized in that: The steel plates produced have good crack arresting ability, ensuring the reliability of the material during use.

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