Production method of large-thickness blank 09MnNiDR steel plate with core copious cooling toughness

Abstract

The invention discloses a production method of a large-thickness blank 09MnNiDR steel plate with core cryogenic toughness. The production method comprises the steps of component smelting, refining, pouring of superheat degree and control over the rolling procedure. According to the method, harmful elements and impurities of molten steel can be reduced, core segregation is relieved, the steel plate structure is optimized, core grains are refined, and therefore the cryogenic toughness of the steel plate core is improved. The operation method is convenient and effective, and the cryogenic toughness requirement of a large-thickness blank finished 09MnNiDR steel plate core can be met with low cost. According to the large-thickness blank 09MnNiDR steel plate with the requirement for the core cryogenic toughness, the one-time qualified rate is increased from 40% and stabilized to 97% or above, and the problem that the qualified rate of the core cryogenic toughness of the large-thickness blank 09MnNiDR steel plate is low is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of low-temperature container steel production technology, and in particular relates to a method for producing a thick 09MnNiDR steel plate with deep-cold toughness in the core. Background Art

[0002] Low-temperature pressure vessel steel 09MnNiDR now generally requires core impact toughness, with impact temperatures often below -70°C and absorbed energy values above 80J – both exceeding standard requirements. For steel plates thicker than 60mm, meeting these toughness requirements using billet-finished material is extremely difficult. Once core toughness fails, it is virtually impossible to salvage the plate, resulting in a high probability of scrap and significant quality loss. Producing the plate using ingots is also extremely costly. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for producing a thick 09MnNiDR steel plate with deep cryogenic toughness in the core. By controlling the smelting composition, refining process, pouring superheat, and rolling process, the deep cryogenic toughness of the core of the thick 09MnNiDR steel plate is greatly improved at a relatively low cost.

[0004] In order to solve the above method problems, the method scheme adopted by the present invention is:

[0005] A method for producing a thick 09MnNiDR steel plate with deep-cold toughness in the core, comprising controlling the following processes: smelting composition, refining, pouring superheat and rolling.

[0006] Preferably, the smelting composition process is controlled according to low carbon, medium-high manganese, low phosphorus and low sulfur, and the control quality range is: carbon 0.05-0.07%, manganese 1.30-1.40%, phosphorus ≤0.010%, sulfur ≤0.002%.

[0007] In the present invention, the controlled smelting composition is based on the fact that carbon and manganese are easily segregated elements. Carbon exceeding 0.07% and manganese exceeding 1.40% in the molten steel will exacerbate segregation in the steel plate. Phosphorus and sulfur are harmful elements and significantly impact impact toughness. Phosphorus exceeding 0.01% and sulfur exceeding 0.002% in the molten steel will exacerbate the deterioration of impact toughness. Therefore, in the composition design, a control range of 0.05-0.07% carbon, 1.30-1.40% manganese, ≤0.010% phosphorus, and ≤0.002% sulfur is adopted to achieve improved impact toughness without sacrificing steel plate strength.

[0008] Preferably, in the refining process, the vacuum degree is maintained below 66 Pa for 18 minutes, and the soft blowing time at normal pressure is 12 to 15 minutes. Normal pressure is 0.1 MPa, which refers to one atmosphere, that is, the gas pressure produced by the atmosphere we live in.

[0009] The controlled refining process described in the present invention is that the same type of steel plates produced by traditional refining processes can only meet the core impact resistance above -50°C. Therefore, a refining process with a vacuum holding time of 18 minutes below 66Pa and a normal pressure soft blowing time of 12 to 15 minutes is adopted, which can reduce the gas content by 20 to 30% and the inclusion content by 50 to 60%, thereby reducing their impact on impact toughness.

[0010] Preferably, the superheat degree in the pouring superheat degree process is 5-15°C.

[0011] To ensure a smoother pouring process, the present invention typically controls the pouring superheat, typically between 15°C and 35°C. This can exacerbate central segregation in the billet and negatively impact the core's impact toughness. Therefore, while ensuring high-purity molten steel quality in the early stages, reducing the pouring superheat to 5°C and 15°C can reduce the proportion of central segregation below Class B level 0.5 by 40% to 50%.

[0012] Preferably, the rolling process adopts a method of alternating horizontal and longitudinal rolling, a first-stage high-temperature and large-reduction rolling combined with a second-stage low-temperature rolling with no less than 6 passes, and low red-return temperature control;

[0013] The first stage rolling temperature is 950-980℃, with at least 3 passes and a reduction of 30mm or more. The second stage rolling temperature is 800-830℃, with a reduction of 5-20mm. The red-returning temperature of the steel plate after rolling is controlled between 550-600℃.

[0014] Preferably, the steel plates produced by the production method have a first pass rate of -85°C to -70°C core impact toughness of more than 97%.

[0015] Preferably, the thickness of the steel plate produced by the production method is 60 mm to 110 mm.

[0016] The controlled rolling process described in this invention fails to meet the requirements for increasing dislocations, homogenizing the microstructure, and refining the grains through conventional rolling methods and post-rolling red-hot temperature control. Therefore, alternating transverse and longitudinal rolling is employed during the rolling process to increase dislocations and reduce the three-dimensional tensile stress in the steel plate core. A first-stage rolling process, at a temperature of 950-980°C with at least three passes of 30 mm or more, is combined with a second-stage low-temperature rolling process at 800-830°C with at least six passes of 5-20 mm reduction. This achieves grain breakup and homogenization, improves core porosity, and promotes the formation of bainite and reversed austenite, creating a tough microstructure characterized by "fine grains and high plasticity" in the steel plate core. A controlled cooling process is employed to maintain the red-hot temperature between 550-600°C, increasing the proportion of lath bainite and homogenizing the microstructure. This rolling process can reduce the impact temperature of steel plates by 20-30°C and improve impact energy absorption by 40-45%.

[0017] The beneficial effects of adopting the above control method are:

[0018] 1. The design of low carbon, medium manganese, low phosphorus and low sulfur components can reduce the segregation of steel plates and reduce the content of harmful elements, which means that the strength of the steel plates will not be lost while improving the impact toughness.

[0019] 2. The vacuum degree below 66Pa is maintained for 18 minutes, and the soft blowing time at normal pressure is 12 to 15 minutes. This can not only meet the requirements of limiting gas removal and maximizing inclusion removal, but also provide the best guarantee for impact toughness at the source without affecting the production rhythm.

[0020] 3. Controlling the pouring superheat at 5-15℃ can ensure smooth pouring of the molten steel smelted according to the process in "2" and reduce center segregation;

[0021] 4. Alternating cross-rolling and longitudinal rolling, high-temperature and high-reduction rolling in the first stage combined with low-temperature multi-pass rolling in the second stage and low red-return temperature control can improve internal porosity, optimize structure, refine grains, and improve both impact toughness and lossless grade.

[0022] 5. The thick 09MnNiDR steel plate produced by the present invention, which requires deep-cold toughness of the core, has a core impact toughness qualification rate that is stable at above 97%. DETAILED DESCRIPTION

[0023] Example 1:

[0024] This example produces 13 75mm thick 09MnNiDR steel plates. The control method includes designing low carbon, medium-high manganese, low phosphorus, and low sulfur compositions, maintaining a vacuum below 66 Pa for 18 minutes, soft blowing at normal pressure for 12-15 minutes, a pouring superheat of 5-15°C, alternating horizontal and vertical rolling, a first-stage high-temperature, high-reduction rolling method combined with a second-stage, low-temperature, multi-pass rolling method, and low red-return temperature control. The details are as follows:

[0025] (1) Smelting ingredients: carbon 0.06%, manganese 1.35%, phosphorus 0.007%, sulfur 0.0020%;

[0026] (2) The vacuum holding time below 66 Pa is 18 minutes, and the normal pressure soft blowing time is 15 minutes;

[0027] (3) Pouring superheat 15℃;

[0028] (4) First stage rolling at 980℃: 2 passes in transverse direction and 3 passes in longitudinal direction, with a reduction of 30 mm in 3 passes;

[0029] Second stage: 830℃ rolling: 6 passes, with a reduction of 10-20mm;

[0030] The red-return temperature of steel plate after rolling: 580℃.

[0031] According to the control method of this embodiment, the impact energy absorption value of the steel plate after rolling at -70°C is between 210 and 355J, and the impact energy absorption value at -85°C is between 130 and 310J.

[0032] Example 2:

[0033] This example produces ten 82mm thick 09MnNiDR steel plates using a control method that includes low carbon, medium-high manganese, low phosphorus, and low sulfur composition design, maintaining a vacuum below 66 Pa for 18 minutes, soft blowing at normal pressure for 12-15 minutes, a pouring superheat of 5-15°C, alternating horizontal and vertical rolling, a first-stage high-temperature, high-reduction rolling process combined with a second-stage, low-temperature, multi-pass rolling process, and low red-return temperature control. The details are as follows:

[0034] (1) Smelting ingredients: carbon 0.05%, manganese 1.38%, phosphorus 0.006%, sulfur 0.0015%;

[0035] (2) The vacuum holding time below 66 Pa is 18 minutes, and the normal pressure soft blowing time is 15 minutes;

[0036] (3) Pouring superheat 13°C;

[0037] (4) First stage rolling at 980℃: 2 passes in transverse direction and 3 passes in longitudinal direction, 30mm reduction in 3 passes and 40mm reduction in 1 pass;

[0038] Second stage: 827℃ rolling: 7 passes, with a reduction of 8 to 15 mm;

[0039] The red-return temperature of steel plate after rolling is 598℃.

[0040] According to the control method of this embodiment, the impact energy absorption value of the rolled steel plate at -70°C is between 180 and 330 J, and the impact energy absorption value at -85°C is between 180 and 290 J.

[0041] Example 3:

[0042] This example produces 18 70mm thick 09MnNiDR steel plates. The control method includes designing low carbon, medium-high manganese, low phosphorus, and low sulfur compositions, maintaining a vacuum below 66 Pa for 18 minutes, soft blowing at normal pressure for 12-15 minutes, a pouring superheat of 5-15°C, alternating horizontal and vertical rolling, a first-stage high-temperature, high-reduction rolling method combined with a second-stage, low-temperature, multi-pass rolling method, and low red-return temperature control. The details are as follows:

[0043] (1) Smelting ingredients: carbon 0.07%, manganese 1.36%, phosphorus 0.008%, sulfur 0.0020%;

[0044] (2) The vacuum holding time below 66 Pa is 18 minutes, and the normal pressure soft blowing time is 13 minutes;

[0045] (3) Pouring superheat 12°C;

[0046] (4) First stage rolling at 980°C: 2 passes in transverse direction, 3 passes in longitudinal direction, 4 passes with a reduction of 30 mm;

[0047] Second stage: 828℃ rolling: 8 passes, with a reduction of 10-20mm;

[0048] The red-return temperature of steel plate after rolling is 576℃.

[0049] According to the control method of this embodiment, the impact energy absorption value of the rolled steel plate at -70°C is between 195 and 330 J, and the impact energy absorption value at -85°C is between 130 and 280 J.

[0050] Example 4:

[0051] This example produces ten 110mm thick 09MnNiDR steel plates. The control method includes designing low carbon, medium-high manganese, low phosphorus, and low sulfur compositions, maintaining a vacuum below 66 Pa for 18 minutes, soft blowing at normal pressure for 12-15 minutes, a pouring superheat of 5-15°C, alternating horizontal and vertical rolling, a first-stage high-temperature, high-reduction rolling method combined with a second-stage, low-temperature, multi-pass rolling method, and low red-return temperature control. The details are as follows:

[0052] (1) Smelting ingredients: carbon 0.05%, manganese 1.33%, phosphorus 0.005%, sulfur 0.0012%;

[0053] (2) The vacuum holding time below 66 Pa is 18 minutes, and the normal pressure soft blowing time is 15 minutes;

[0054] (3) Pouring superheat 10℃;

[0055] (4) First stage rolling at 950 °C: 2 passes in transverse direction, 3 passes in longitudinal direction, 4 passes with a reduction of 30 mm;

[0056] Second stage: 800℃ rolling: 8 passes, with a reduction of 5 to 15 mm;

[0057] The red-return temperature of steel plate after rolling is 565℃.

[0058] According to the control method of this embodiment, the impact energy absorption value of the rolled steel plate at -70°C is between 115 and 290 J, and the impact energy absorption value at -85°C is between 85 and 210 J.

[0059] Example 5:

[0060] This example produces 18 90mm thick 09MnNiDR steel plates. The control method includes designing low carbon, medium-high manganese, low phosphorus, and low sulfur compositions, maintaining a vacuum below 66Pa for 18 minutes, soft blowing at normal pressure for 12-15 minutes, a pouring superheat of 5-15°C, alternating horizontal and vertical rolling, a first-stage high-temperature, high-reduction rolling method combined with a second-stage, low-temperature, multi-pass rolling method, and low red-return temperature control. The details are as follows:

[0061] (1) Smelting ingredients: carbon 0.05%, manganese 1.31%, phosphorus 0.005%, sulfur 0.0015%;

[0062] (2) The vacuum holding time below 66 Pa is 18 minutes, and the normal pressure soft blowing time is 15 minutes;

[0063] (3) Pouring superheat 5℃;

[0064] (4) First stage rolling at 980℃: 2 passes in transverse direction and 3 passes in longitudinal direction, with a reduction of 40 mm in 3 passes;

[0065] Second stage: 825℃ rolling: 7 passes, with a reduction of 5 to 15 mm;

[0066] The red-return temperature of steel plate after rolling: 550℃.

[0067] After the control method of this embodiment, 17 steel plates were qualified: the -70°C impact energy absorption value was between 100 and 230J, the -85°C impact energy absorption value was between 98 and 236J, and the -85°C impact toughness temperature energy absorption value of one plate was 18.9J.

[0068] Example 6:

[0069] This example produces 50 60mm thick 09MnNiDR steel plates. The control method includes designing low carbon, medium-high manganese, low phosphorus, and low sulfur compositions, maintaining a vacuum below 66 Pa for 18 minutes, soft blowing at normal pressure for 12-15 minutes, a pouring superheat of 5-15°C, alternating horizontal and vertical rolling, a first-stage high-temperature, high-reduction rolling method combined with a second-stage, low-temperature, multi-pass rolling method, and low red-return temperature control. The details are as follows:

[0070] (1) Smelting composition: carbon 0.07%, manganese 1.38%, phosphorus 0.01%, sulfur 0.0019%;

[0071] (2) The vacuum holding time below 66 Pa is 18 minutes, and the normal pressure soft blowing time is 12 minutes;

[0072] (3) Pouring superheat 10℃;

[0073] (4) First stage rolling at 950 °C: 2 passes in transverse direction, 3 passes in longitudinal direction, 4 passes with a reduction of 35 mm;

[0074] Second stage: 825℃ rolling: 7 passes, with a reduction of 10-20mm;

[0075] The red-return temperature of steel plate after rolling: 600℃.

[0076] The control method of this embodiment is used for the steel plate after rolling: the impact energy absorption value at -70°C is between 233 and 336 J, and the impact energy absorption value at -85°C is between 189 and 315 J.

[0077] The above embodiments are only used to illustrate rather than limit the method scheme of the present invention. Although the present invention is described in detail with reference to the above embodiments, ordinary method personnel in this field should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for producing a thick 09MnNiDR steel plate with deep cold toughness in the core, characterized in that: Includes control of the following processes: smelting composition, refining, pouring superheat and rolling.

2. The method for producing a thick 09MnNiDR steel plate with deep cold toughness in the core according to claim 1, characterized in that: The smelting composition process is controlled according to low carbon, medium-high manganese, low phosphorus and low sulfur, and the control quality range is: carbon 0.05-0.07%, manganese 1.30-1.40%, phosphorus ≤0.010%, sulfur ≤0.002%.

3. The method for producing a thick 09MnNiDR steel plate with deep cold toughness in the core according to claim 1, characterized in that: In the refining process, the vacuum degree below 66 Pa is maintained for 18 minutes, and the normal pressure soft blowing time is 12 to 15 minutes.

4. The method for producing a thick 09MnNiDR steel plate with deep cold toughness in the core according to claim 1, characterized in that: The superheat degree in the pouring superheat degree process is 5-15°C.

5. The method for producing a thick 09MnNiDR steel plate with deep cold toughness in the core according to claim 1, characterized in that: The rolling process adopts a method of alternating horizontal and longitudinal rolling, a first-stage high-temperature large-reduction rolling method combined with a second-stage low-temperature rolling method of not less than 6 passes, and low red-return temperature control; The first stage rolling temperature is 950~980℃, with at least 3 passes and a reduction of 30mm or more. The second stage rolling temperature is 800~830℃, with a reduction of 5~20mm. The red-returning temperature of the steel plate after rolling is controlled between 550~600℃.

6. The method for producing a thick 09MnNiDR steel plate with deep cold toughness in the core according to claim 1, characterized in that: The steel plates produced by the production method have a first pass rate of -85°C to -70°C core impact toughness of more than 97%.

7. The method for producing a thick 09MnNiDR steel plate with deep cold toughness in the core according to claim 1, characterized in that: The thickness of the steel plate produced by the production method is 60mm~110mm.