High-temperature high-pressure rolling production method for thick steel plate
By using a high-temperature, high-pressure rolling method combined with continuous casting, heating, and straightening processes, the problems of coarse grains, segregation, and inclusions in thick steel plates have been solved, resulting in improved performance and stability of thick steel plates, which are suitable for engineering applications such as bridges, high-rise buildings, and shipbuilding.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-01
- Publication Date
- 2026-04-03
AI Technical Summary
Existing technologies for producing thick steel plates suffer from problems such as coarse grains, segregation and inclusion defects, and poor process compatibility, leading to unstable performance and potential safety hazards, especially in engineering applications such as high-rise buildings and shipbuilding.
By employing a high-temperature, high-reduction rolling method, combined with continuous casting, heating, and straightening processes, and by controlling the superheat of molten steel, casting speed, heating time, and calcium-iron wire feeding, core grain refinement, compositional uniformity, and microstructure uniformity are achieved, and the rolling strategy is optimized to improve performance.
It significantly improves the core grain size and performance qualification rate of thick steel plates, increases impact performance by 30%, and improves Z-axis performance by 45%, making it suitable for major projects such as bridges, high-rise buildings, and shipbuilding.
Smart Images
Figure CN121776243A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of metallurgical manufacturing technology, specifically to a high-temperature, high-reduction rolling production method for thick steel plates. Background Technology
[0002] Thick steel plates (thickness ≥ 80 mm) are widely used in major engineering projects such as bridges, high-rise buildings, and shipbuilding. Their performance stability is one of the core factors determining the safety of engineering structures, and they play an irreplaceable role in ensuring the quality and service life of major national engineering projects.
[0003] However, existing technologies face numerous key challenges in the production of thick steel plates, severely hindering performance improvements and the reliability of their engineering applications:
[0004] Coarse grain problem: In the traditional rolling strategy, the reduction per pass is insufficient, and the rolling force is difficult to be effectively transferred to the core of the steel plate. As a result, the core grains are not sufficiently refined, which directly affects the impact performance and Z-axis performance of the steel plate and poses a potential threat to the impact resistance and lamellar tear resistance of engineering structures.
[0005] Segregation and inclusion defects: Frequent segregation and MnS inclusion problems in billets result in a high rate of unqualified Z-direction performance of thick steel plates, which greatly limits their application in engineering scenarios with high sensitivity to lamellar tearing (such as steel structure nodes of high-rise buildings).
[0006] Poor process matching: The distribution of reduction during the rolling stage is unreasonable, and the control of final rolling temperature and deformation is not precise, resulting in insufficient uniformity of steel plate structure, which further affects the stability and consistency of its comprehensive mechanical properties.
[0007] Given the crucial role of thick steel plates in major engineering projects, and the significant shortcomings of existing production technologies in areas such as grain refinement, compositional homogenization, and synergistic process control, this invention provides a high-temperature, high-pressure rolling production method for thick steel plates. This method achieves core grain refinement, compositional segregation and inclusion control, and microstructure homogenization optimization in thick steel plates. It will not only provide high-performance guarantees for major projects such as bridges, high-rise buildings, and shipbuilding in my country, but also promote the technological upgrading of steel rolling processes and enhance my country's core competitiveness in the field of high-end steel materials. Summary of the Invention
[0008] To address the shortcomings of the existing technologies, this invention provides a high-temperature, high-reduction rolling production method for thick steel plates. By improving billet design, rolling strategy, and heating process, the method achieves core grain refinement, compositional segregation and inclusion control, and microstructure uniformity optimization in thick steel plates, significantly improving the performance qualification rate of thick steel plates.
[0009] To achieve the above objectives, the specific technical solution of the present invention is as follows:
[0010] This invention provides a high-temperature, high-reduction rolling production method for thick steel plates, including continuous casting, heating, rolling, and straightening processes. The rolling process includes: a roughing stage employing a high-temperature, high-reduction strategy, controlling the initial rolling temperature at 1160-1200 ℃ and a single-pass reduction ≥ 35 mm to fully break down the original austenite grains; and a finishing stage employing a low-temperature, high-reduction strategy, with an initial rolling temperature ≤ 850 ℃, controlling the cumulative deformation ≥ 40%, and a final rolling temperature of 770-830 ℃ to improve the uniformity of the core microstructure.
[0011] Furthermore, during continuous casting, the superheat of the molten steel is controlled at 15-25 °C, and the casting speed is 0.85 m / min. This invention, by controlling the superheat of the molten steel within a low range, promotes the formation of equiaxed crystals, refines the grains, and makes the internal structure of the slab more uniform and dense, significantly improving the Z-axis properties and overall mechanical properties of the subsequent steel plate. Controlling the casting speed at both low superheat and low casting speed facilitates the replenishment of solidification shrinkage by the molten steel, reduces central porosity, and results in a thicker and more uniform shell, reducing the risk of leaks. This invention, by combining low superheat with low casting speed, can significantly reduce segregation and MnS inclusions.
[0012] Furthermore, the slab obtained from continuous casting has a cross-section of 360 mm.
[0013] Furthermore, in the heating process, the preheating section temperature is 600-900 ℃, the heating section temperature is 1130-1280 ℃, the soaking section temperature is 1200-1240 ℃, and the temperature difference between the core and surface of the slab is controlled to be ≤ 25 ℃ during the heating process.
[0014] Furthermore, the heating period lasts 3-4 hours, the soaking period lasts ≥ 35 minutes, and the total heating time is 4.8-6.6 hours. In this invention, extending the heating period to 3-4 hours and setting the total heating time to 4.8-6.6 hours promotes uniform temperature in the billet core and reduces segregation. Simultaneously, calcium-iron wire feeding during heating strengthens calcium treatment, promoting MnS inclusion spheroidization and reducing Z-axis performance risks. Through this synergistic treatment of "wire feeding process + heating coordination," this invention efficiently modifies inclusions during the slab heating stage, addressing the Z-axis performance defects in thick steel plates caused by MnS inclusions at the source, laying the foundation for subsequent microstructure refinement and performance improvement in the rolling process.
[0015] Furthermore, in the roughing stage, the reduction per pass is 35-40 mm.
[0016] Furthermore, in the straightening process, pre-straightening is first performed using re-straightening, with a maximum straightening force of ≥ 1000 tons to ensure the straightness of the pre-straightened steel plate.
[0017] The present invention also provides thick steel plates produced using the aforementioned production method.
[0018] Compared with the prior art, the advantages of the present invention are:
[0019] This invention improves billet design, rolling strategy, and heating process to achieve refined core grains, controlled compositional segregation and inclusions, and optimized microstructure uniformity in thick steel plates. Specifically, the original core grain size is improved from coarse (ASTM 3-4 grade) to uniformly refined (ASTM 6-7 grade), resulting in an impact performance improvement of ≥30%. The first-pass yield of steel plates with a thickness ≥80 mm is increased from 50% to ≥85%, and the average Z-axis performance is improved from ≤40% to ≥45%. This method is applicable to various types of steel, including bridge steel, ship plates, and high-strength building steel plates, enabling stable production of ultra-thick specifications (such as 140 mm Q420qD). Attached Figure Description
[0020] Figure 1 Metallographic images of the steel plates of Example 1 and Comparative Example 1 with different thicknesses are shown. Detailed Implementation
[0021] To enable those skilled in the art to clearly and completely understand the technical solution of the present invention, the present invention will be further described in detail below with reference to embodiments. Obviously, the embodiments described herein are only for explaining the present invention and are not intended to limit the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0022] This invention provides a method for producing thick steel plates by high-temperature, high-reduction rolling, comprising:
[0023] 1. Continuous casting process:
[0024] The superheat of the molten steel is controlled at 15-25 °C, the casting speed is 0.85 m / min, and the continuous casting billet has a cross-section of 360 mm. This invention, by controlling the superheat of the molten steel within a low range, promotes the formation of equiaxed crystals, refines the grains, and makes the internal structure of the slab more uniform and dense, significantly improving the Z-axis properties and overall mechanical properties of the subsequent steel plate. Controlling the casting speed at both low superheat and low casting speed facilitates the replenishment of solidification shrinkage by the molten steel, reduces central porosity, and results in a thicker and more uniform billet shell, reducing the risk of run-out. This invention, by combining low superheat with low casting speed, can significantly reduce segregation and MnS inclusions.
[0025] 2. Heating process:
[0026] The preheating section temperature is 600-900 ℃; the heating section temperature is 1130-1280 ℃, and the heating time is 3-4 h; the soaking section temperature is 1200-1240 ℃, and the soaking time is ≥ 35 min; the total heating process time is 4.8-6.6 h, and the temperature difference between the core and surface of the slab is controlled to be ≤ 25 ℃ during the heating process.
[0027] Calcium-iron wire feeding is completed during the conveying process before the slab enters the heating furnace. After feeding, the slab is immediately sent into the heating furnace. The high temperature during the heating process promotes the reaction between calcium and inclusions. The wire feeding speed is controlled at 2-4 m / s, and the wire feeding amount is 300-500 m / furnace to ensure complete modification of inclusions such as MnS. Multi-point wire feeding is adopted, with 2-3 wire feeding points evenly arranged in the width direction of the slab to ensure that the calcium element is evenly distributed in the core and to achieve full-section inclusion modification.
[0028] This invention extends the heating period to 3-4 hours, setting the total heating time to 4.8-6.6 hours. This promotes uniform temperature in the billet core and reduces segregation. Simultaneously, calcium-iron wire feeding during heating strengthens calcium treatment, promoting the spheroidization of MnS inclusions and reducing the risk to Z-axis performance. Through this synergistic treatment of "wire feeding process + heating coordination," this invention efficiently modifies inclusions during the slab heating stage, addressing the problem of unsatisfactory Z-axis performance in thick steel plates caused by MnS inclusions at its source. This lays the foundation for subsequent microstructure refinement and performance improvement in the rolling process.
[0029] 3. Rolling process:
[0030] In the roughing stage, a high-temperature and high-reduction strategy is adopted, controlling the initial rolling temperature at 1160-1200 ℃ and the single-pass reduction at ≥35 mm, so as to fully break the original austenite grains.
[0031] In the finishing rolling stage, a low-temperature, high-reduction strategy is adopted, controlling the initial rolling temperature to ≤ 850 ℃, controlling the cumulative deformation to ≥ 40%, and the final rolling temperature to 770-830 ℃, in order to improve the uniformity of the core structure. If the finishing rolling temperature exceeds 850 ℃, it will lead to the inability to effectively refine the grains, resulting in coarse grains in the steel plate, which in turn leads to the deterioration of the steel plate's strength, toughness, plasticity and other properties.
[0032] 4. Straightening process:
[0033] First, pre-straightening is performed using a return straightening method, with a maximum straightening force of ≥ 1000 tons, to ensure the pre-straightened steel plate is straight.
[0034] The technical solution of the present invention will be clearly and completely described below.
[0035] Example 1
[0036] This embodiment uses a high-temperature, high-reduction rolling method to produce 124 mm Q370qD steel plates. The specific steps are as follows:
[0037] (1) Billet preparation:
[0038] The dimensions of the slab are: length 2600 mm, width 2195 mm, and thickness 360 mm.
[0039] (2) Heating process:
[0040] The feeding speed of the calcium iron wire is controlled at 3 m / s, and the feeding amount is 400 m / furnace;
[0041] The preheating section temperature was 700 ℃ for 9 min; the heating section temperature was 1170 ℃ for 219 min; the soaking section temperature was 1220 ℃ for 139 min, and the total heating time was 367 min; the temperature difference between the core and surface of the slab during the heating process was 10 ℃.
[0042] (3) Rolling process:
[0043] In the roughing stage, a high-temperature and high-reduction strategy is adopted. The initial rolling temperature is 1200 ℃, the single-pass reduction is 40 mm, and the cumulative reduction is 120 mm for three consecutive passes.
[0044] In the finishing rolling stage, a low-temperature, high-reduction strategy is adopted, with an initial rolling temperature of 822 ℃, a cumulative deformation of 40%, and a final rolling temperature of 774 ℃. The head and tail S-bends are controlled, and leveling passes are used to improve the shape of the rolled plate.
[0045] After rolling, the steel plate is pre-straightened by re-straightening. The maximum straightening force should not be less than 1,000 tons to ensure that the pre-straightened steel plate is straight.
[0046] (4) Performance Testing: The 124 mm Q370qD steel plate prepared in this embodiment has a yield strength of 417 MPa, a tensile strength of 534 MPa, an elongation of 20.0%, an average impact energy of 254 J at -20 ℃, an average Z-direction property value of 45%, and a first-pass yield of 100%. The metallographic image of the 124 mm Q370qD steel plate prepared in this embodiment is shown below. Figure 1 As shown, the grain size is small and uniformly distributed, with clear grain boundaries and no obvious defects. Furthermore, in the 124 mm Q370qD steel plate prepared in this embodiment, ferrite, pearlite, and bainite are present at 1 / 4 and 3 / 4 of the plate, exhibiting uniform properties.
[0047] Comparative Example 1
[0048] (1) Preparation of billet:
[0049] The blank is made of 300 mm section (3500 mm in length, 1955 mm in width, and 300 mm in thickness).
[0050] (2) Heating process:
[0051] The feeding speed of the calcium iron wire is controlled at 3 m / s, and the feeding amount is 400 m / furnace;
[0052] The preheating section temperature was 650 ℃ for 16 min; the heating section temperature was 1143 ℃ for 249 min; the soaking section temperature was 1195 ℃ for 58 min, and the total heating time was 323 min; the temperature difference between the core and surface of the slab during the heating process was 23 ℃.
[0053] (3) Rolling process:
[0054] In the roughing stage, the initial rolling temperature is 1187 ℃, the single-pass reduction is 20 mm, and the cumulative reduction for three consecutive passes is 84 mm.
[0055] In the finishing rolling stage, the initial rolling temperature (No. 1 controlled rolling temperature) is 827 ℃, and the final rolling temperature (loaded temperature) is 820 ℃.
[0056] After rolling, the steel plate is pre-straightened by re-straightening. The maximum straightening force should not be less than 1,000 tons to ensure that the pre-straightened steel plate is straight.
[0057] The metallographic image of the thick steel plate prepared in this comparative example is shown below. Figure 1 As shown, large, irregular dark areas exist (possibly due to compositional segregation, inclusion aggregation, or abnormal phase transformation products), and the overall grain size is relatively coarse. This microstructure leads to non-uniform steel plate properties, and the segregated / inclusion areas are prone to becoming crack initiation sites, reducing the strength and toughness of the steel plate. Furthermore, in the thick-gauge steel plate prepared in this comparative example, the first quarter section is composed of ferrite + pearlite, and the third quarter section is composed of ferrite + pearlite + bainite, indicating non-uniform steel plate properties.
[0058] Comparative Example 2
[0059] (1) Preparation of billet:
[0060] The dimensions of the slab are: length 2420 mm, width 2000 mm, and thickness 360 mm.
[0061] (2) Heating process:
[0062] The feeding speed of the calcium iron wire is controlled at 3 m / s, and the feeding amount is 400 m / furnace;
[0063] The preheating section temperature was 428 ℃ for 98 min; the heating section temperature was 1169 ℃ for 234 min; the soaking section temperature was 1182 ℃ for 50 min, and the total heating time was 382 min; the temperature difference between the core and surface of the slab during the heating process was 22 ℃.
[0064] (3) Rolling process:
[0065] In the roughing stage, the initial rolling temperature is 1123 ℃ (far less than the range of 1160-1200 ℃ defined in this invention). The roughing temperature of this comparative example is too low, and the deformation resistance is large, making it difficult for the single-pass reduction in the roughing stage to be ≥ 35 mm, resulting in insufficient total deformation. In the finishing stage, the deformation resistance is too large, leading to uneven microstructure and surface quality problems.
[0066] Comparative Example 3
[0067] (1) Preparation of billet:
[0068] The dimensions of the slab are: length 3930 mm, width 2193 mm, and thickness 360 mm.
[0069] (2) Heating process:
[0070] The feeding speed of the calcium iron wire is controlled at 3 m / s, and the feeding amount is 400 m / furnace;
[0071] The preheating section temperature was 745 ℃ for 28 min; the heating section temperature was 1182 ℃ for 214 min; the soaking section temperature was 1230 ℃ for 145 min, and the total heating time was 387 min; the temperature difference between the core and surface of the slab during the heating process was 17 ℃.
[0072] (3) Rolling process:
[0073] In the roughing stage, a high-temperature and high-reduction strategy was adopted. The initial rolling temperature was 1200 ℃, and the rolling was carried out in 3 consecutive passes, with a cumulative reduction of 126 mm and an average reduction of 42 mm per pass.
[0074] In the finishing rolling stage, the initial rolling temperature was 748 ℃, the cumulative deformation in the second stage was 27.73%, less than 40%, and the final rolling temperature was 743 ℃ (far less than the range of 770-830 ℃ defined in this invention). In the roughing stage of this comparative example, the temperature was high and the pressure was high, but due to the unreasonable setting of the cumulative deformation and final rolling temperature in the finishing rolling stage, the steel plate impact was not in line with the requirements.
[0075] In summary, this invention employs continuous casting, heating, rolling, and straightening processes to prepare thick-gauge steel plates. The rolling process includes: a roughing stage using a high-temperature, high-reduction strategy, controlling the initial rolling temperature at 1160-1200 ℃ and a single-pass reduction ≥35 mm; and a finishing stage using a low-temperature, high-reduction strategy, with an initial rolling temperature ≤850 ℃, controlling the cumulative deformation ≥40%, and a final rolling temperature of 770-830 ℃. This invention, through specific rolling strategies and heating processes, achieves core grain refinement, compositional segregation and inclusion control, and microstructure uniformity optimization in thick-gauge steel plates, significantly improving the performance qualification rate of thick-gauge steel plates.
[0076] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.
Claims
1. A method for producing thick steel plates by high-temperature, high-reduction rolling, characterized in that, The process includes continuous casting, heating, rolling, and straightening. The rolling process includes: in the roughing stage, a high-temperature, high-reduction strategy is adopted, with the initial rolling temperature controlled at 1160-1200 ℃ and a single-pass reduction of ≥ 35 mm; in the finishing stage, a low-temperature, high-reduction strategy is adopted, with the initial rolling temperature ≤ 850 ℃, the cumulative deformation controlled at ≥ 40%, and the final rolling temperature at 770-830 ℃.
2. The method for producing thick steel plates by high-temperature, high-reduction rolling according to claim 1, characterized in that, During the roughing stage, the reduction per pass is 35-40 mm.
3. The method for producing thick steel plates by high-temperature, high-reduction rolling according to claim 1, characterized in that, During the continuous casting process, the superheat of the molten steel is controlled at 15-25℃.
4. The method for producing thick steel plates by high-temperature, high-reduction rolling according to claim 1, characterized in that, In the heating process, the preheating section temperature is 600-900 ℃, the heating section temperature is 1130-1280 ℃, and the soaking section temperature is 1200-1240 ℃.
5. The method for producing thick steel plates by high-temperature, high-reduction rolling according to claim 4, characterized in that, The heating period lasts for 3-4 hours, the soaking period lasts for ≥ 35 minutes, and the total heating process time is 4.8-6.6 hours.
6. The method for producing thick steel plates by high-temperature, high-reduction rolling according to claim 4, characterized in that, In the heating process, calcium-iron wire is simultaneously used for calcium-enhanced treatment.
7. The method for producing thick steel plates by high-temperature, high-reduction rolling according to claim 1, characterized in that, In the straightening process, pre-straightening is first performed using re-straightening, with a maximum straightening force of ≥1000 tons.
8. Thick steel plates produced by the production method according to any one of claims 1-7.