A method for rolling optimization of gear steel rectangular continuous casting billet frame segregation based on metal flow behavior analysis

Abstract

The application discloses a gear steel rectangular continuous casting billet frame segregation rolling optimization method based on metal flow behavior analysis and belongs to the technical field of metallurgy. The method comprises the following steps: obtaining the initial cross-sectional size and rolling process of the gear steel rectangular continuous casting billet which has frame segregation morphology problems after rolling; establishing a finite element analysis model based on the initial cross-sectional size and rolling process of the gear steel rectangular continuous casting billet to simulate the metal flow behavior in the rolling process; analyzing the metal flow behavior in each pass rolling process and identifying the dominant factors influencing the frame segregation morphology evolution; and adjusting the rolling process of the rolling pass interval corresponding to the dominant factors. The application analyzes the metal flow behavior in the gear steel rectangular continuous casting billet rolling process based on the finite element analysis means, identifies the dominant factors influencing the frame segregation morphology evolution, and accordingly carries out targeted optimization, so that the length-width ratio of the frame segregation characteristic zone is reduced and tends to be 1, and the directionality is weakened.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to an optimization method for frame-type segregation rolling of rectangular continuous casting billets for gear steel based on metal flow behavior analysis. Background Technology

[0002] Gear steel is widely used in key components of automobiles, construction machinery, and general transmission systems. This type of material typically undergoes multiple processes such as continuous casting, hot rolling, forging, machining, and carburizing and quenching. During service, it is subjected to alternating bending stress and contact stress, thus placing high demands on the steel's compositional uniformity, microstructure uniformity, and consistency of heat treatment response.

[0003] Rectangular billets have more mature rolling processes and equipment, resulting in better production stability and economy. Therefore, they are still widely used in engineering applications. However, in actual production, a segregation morphology commonly exists, characterized by a closed or near-closed ring shape distributed along a certain position on the billet cross-section, often referred to as frame segregation. This type of segregation is mostly located near the boundary between columnar and equiaxed crystal regions. Its formation is closely related to solute redistribution at the end of solidification, enrichment of residual liquid phase between dendrites, and uneven growth of the solidified structure, manifesting as localized component enrichment and structural differences. Due to its spatial scale and positional stability, frame segregation is difficult to completely eliminate during subsequent hot working and heat treatment. When the aspect ratio of this type of segregation characteristic region deviates significantly from 1, its morphology exhibits a clear directionality, making it easily elongated or retained during rolling deformation, thus forming segregation regions of a certain scale on the cross-section. When such areas coincide with critical stress-bearing parts of the gear (such as the tooth root and tooth surface contact area), it can easily lead to inconsistent local structural transformation behavior and performance distribution, thus adversely affecting the service performance of the parts.

[0004] To address segregation in steel, existing technologies primarily focus on continuous casting process control. This includes measures such as reducing steel superheat, optimizing casting speed, employing electromagnetic stirring (EMS), and applying gentle pressure reduction to improve solidification structure and mitigate center segregation. Additionally, high-temperature diffusion annealing can promote the diffusion of alloying elements in the solid state, thereby reducing the compositional gradient. However, these methods primarily target center segregation, offering limited improvement for the specific distribution pattern of frame segregation. Furthermore, high-temperature diffusion treatment typically suffers from high energy consumption and production rhythm limitations, restricting its application in large-scale continuous production.

[0005] Hot rolling, as a crucial link between continuous casting and the final product, not only performs the function of dimensional forming but also has a significant impact on the internal microstructure and segregation morphology evolution of the material. However, existing rolling process designs primarily focus on dimensional accuracy and rolling stability, typically employing a compression deformation path along a single direction. The die configuration and steel-turning operation are mainly used to achieve dimensional control and forming requirements, lacking targeted regulation of the internal strain distribution and metal flow behavior of the material.

[0006] Under the aforementioned rolling conditions, the frame-shaped segregation structure formed during continuous casting often extends along the rolling direction during deformation. Its characteristic region morphology tends to elongate, with a large aspect ratio, resulting in a certain directional and dimensional stability of the segregated region in the cross-section, which is detrimental to its further homogenization. Simultaneously, due to the lack of a systematic design for the deformation path, the strain distribution varies in different regions within the material, making it difficult for the segregated region to be effectively reconstructed through deformation. Summary of the Invention

[0007] The purpose of this invention is to provide an optimization method for frame segregation rolling of rectangular continuous casting billets for gear steel based on metal flow behavior analysis. By constructing multi-directional deformation paths, optimizing die combinations and steel-turning strategies, the internal strain distribution and metal flow behavior of the material can be controlled, so that the aspect ratio of the frame segregation feature area approaches 1 and its spatial scale is reduced, thereby reducing the probability of it hitting key stress parts.

[0008] To solve the above-mentioned technical problems, the present invention is implemented using the following technical solution:

[0009] This invention provides an optimization method for frame-type segregation rolling of rectangular continuous casting billets for gear steel based on metal flow behavior analysis, comprising:

[0010] The initial cross-sectional dimensions and rolling process parameters of the rectangular continuous casting billet of gear steel with frame-shaped segregation morphology after rolling were obtained.

[0011] A finite element analysis model is established based on the initial cross-sectional dimensions of the rectangular continuous casting billet of the gear steel and the rolling process parameters to simulate the metal flow behavior during the rolling process.

[0012] The metal flow behavior during each rolling pass was analyzed to identify the dominant factors influencing the evolution of the frame segregation morphology.

[0013] Based on the aforementioned dominant factors, the rolling process for the corresponding rolling pass intervals is adjusted.

[0014] Optionally, the metal flow behavior includes:

[0015] The distribution and continuity of metal flow lines;

[0016] Equivalent strain distribution in different regions of the rolled piece cross section;

[0017] Coordination of metal flow in both width and height directions;

[0018] The degree of flow participation and redistribution in the frame-type segregation region during the rolling process.

[0019] Optionally, in the analysis of the metal flow behavior during each rolling pass to identify the dominant factors influencing the evolution of the frame segregation morphology,

[0020] When the metal streamlines extend continuously along the rolling direction within the rolling pass interval and the streamline bending angle is less than 15°, the dominant factors affecting the evolution of the frame segregation morphology are determined to be insufficient streamline reconstruction.

[0021] When the equivalent variation between the core and the surface of the cross section is greater than 0.20 within the rolling pass interval, the dominant factors affecting the evolution of the frame segregation morphology are determined to be insufficient core deformation penetration.

[0022] When the ratio of the equivalent strain average value in the width direction to the height direction of the rolled section deviates from 1 by more than 20% within the rolling pass interval, it is determined that the dominant factors affecting the evolution of the frame segregation morphology include insufficient deformation coordination in the width and height directions.

[0023] When the equivalent strain level of the region corresponding to the frame segregation is less than 80% of the average cross-sectional level in the rolling pass interval, the dominant factor affecting the morphological evolution of the frame segregation is determined to be insufficient flow participation.

[0024] Optionally, adjusting the rolling process for the corresponding rolling pass range based on the dominant factor includes:

[0025] In the rolling pass intervals where the degree of streamline reconstruction is insufficient, increase the transition passes, adjust the sequence of pass entry, and extend the cross-sectional change process to increase the flow reconstruction opportunities and promote the bending and redistribution of the corresponding area of ​​frame segregation.

[0026] In the rolling pass section where the core deformation penetration is insufficient, the reduction distribution is coordinated, the deformation path is extended, and the deformation bearing mode of each pass is adjusted to improve the ability of deformation to be transferred to the interior of the cross section and enhance the plastic participation of the core and segregation region.

[0027] In the rolling pass section where the deformation coordination in the width and height directions is insufficient, the turning rhythm, the alternating configuration of the pass type, and the deformation bearing relationship in different directions are adjusted to optimize the flow and improve the coordination of metal flow within the cross section.

[0028] In rolling passes with insufficient flow participation, multi-directional, phased deformation paths are constructed, along with increased transition deformation, adjusted pass combinations, and steel-turning methods, to enhance the local disturbance and redistribution capabilities of this region.

[0029] Optionally, after adjusting the rolling process for the corresponding rolling pass range based on the dominant factor, the method further includes:

[0030] The adjusted rolling process was verified to evaluate its effect on improving the segregation morphology of the frame.

[0031] Optionally, the verification of the adjusted rolling process to evaluate its effect on improving the segregation morphology of the frame type includes:

[0032] Based on the adjusted rolling process, the rectangular continuous casting billet of the gear steel is rolled, and the microstructure of the rolled sample is observed at low magnification. The major axis and minor axis dimensions of the frame segregation characteristic zone are measured, and its aspect ratio is calculated.

[0033] Optionally, the heating regime of the gear steel rectangular continuous casting billet before rolling is the same as the heating regime of the gear steel rectangular continuous casting billet with frame-shaped segregation morphology problems after rolling before rolling.

[0034] Optionally, the aspect ratio of the frame-type segregation feature area in the low magnification of the actual object of the gear steel rectangular continuous casting billet after rolling is greater than 1.2.

[0035] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: Based on finite element analysis, this invention analyzes the metal flow behavior, equivalent strain distribution, deformation coordination in the width and height directions, and the degree of flow participation in the corresponding region of frame segregation during the rolling process of rectangular continuously cast gear steel billets. It identifies key cross-sectional regions and dominant factors affecting the evolution of frame segregation morphology, and accordingly optimizes transition passes, pass sequence, turning rhythm, and reduction distribution to construct a multi-directional, staged rolling path. This method enhances the flow participation and redistribution capacity of the corresponding region of frame segregation during the rolling process, promoting its transformation from a continuously elongated state to a more uniform morphology. It reduces the aspect ratio of the frame segregation characteristic region to near 1, weakens its directionality, and shrinks its spatial scale. Compared with existing methods that mainly rely on continuous casting end control or diffusion treatment, this invention combines finite element analysis with on-site process optimization, requiring no significant modification to the main equipment. It can be directly implemented in existing hot rolling production lines, exhibiting good engineering adaptability and promotional value. Meanwhile, the present invention can improve the uniformity of the microstructure and properties of gear steel products, improve the consistency of subsequent heat treatment, and reduce the adverse effects of frame segregation on key stress parts, thereby helping to improve product quality stability and service reliability. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments or related technologies of this disclosure, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 These are schematic diagrams of hole types A, B, and C in Embodiment 1 provided by the present invention;

[0038] Figure 2 This is a low-magnification image of the actual object after rolling using the original rolling process of Embodiment 1 provided by the present invention;

[0039] Figure 3 This is a schematic diagram of the frame-type segregation zone structure in the final pass of the adjusted rolling process provided in Embodiment 1 of the present invention.

[0040] Figure 4 This is a low-magnification image of the actual object after rolling using the adjusted rolling process of Embodiment 1 provided by the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure / invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0042] This invention introduces an optimization method for frame-type segregation rolling of rectangular continuous casting billets for gear steel based on metal flow behavior analysis, referencing... Figure 1 The optimization method for frame-type segregation rolling of rectangular continuous casting billets for gear steel based on metal flow behavior analysis in this invention includes:

[0043] S1, obtain the initial cross-sectional dimensions and rolling process parameters of the rectangular continuous casting billet of gear steel that has frame-type segregation morphology problems after rolling.

[0044] S2. A finite element analysis model was established based on the initial cross-sectional dimensions and rolling process parameters of the rectangular continuous casting billet of gear steel to simulate the metal flow behavior during the rolling process.

[0045] This invention is suitable for optimizing the rolling process of rectangular continuously cast gear steel billets with frame-like segregation morphology after rolling. For rectangular continuously cast gear steel billets with frame-like segregation morphology after rolling, a finite element analysis model of the rolling process is established, taking into account the initial cross-sectional dimensions, pass parameters, turning method, roll gap value, reduction distribution, and cross-sectional changes between passes, to simulate the metal flow behavior during the rolling process.

[0046] S3 analyzes the metal flow behavior during each rolling pass to identify the dominant factors influencing the evolution of frame segregation morphology.

[0047] The analysis focuses on the internal metal flow behavior of the rolled piece during each rolling pass. Key aspects of this analysis include: the distribution and continuity of metal streamlines; the equivalent strain distribution in different regions of the rolled piece cross-section; the coordination of metal flow in the width and height directions; and the degree of flow participation and redistribution in the frame segregation region during the rolling process.

[0048] Among them, when the metal streamlines extend continuously along the rolling direction within the rolling pass interval and the streamline bending angle is less than 15°, the dominant factor affecting the evolution of the frame segregation morphology is considered to be insufficient streamline reconstruction. When the streamline reconstruction is insufficient, the streamline bending angle is small, and the metal as a whole still mainly flows continuously along the main deformation direction. The flow path changes little, making it difficult to form bends, cuts, and recombinations that are beneficial to the corresponding areas of frame segregation. The segregation characteristic area is more likely to be elongated and retained along the rolling direction.

[0049] When the equivalent strain difference between the core and surface layers within the rolling pass exceeds 0.20, the dominant factor influencing the evolution of the frame-type segregation morphology is insufficient core deformation penetration. Insufficient core deformation penetration results in an excessively large strain difference between the surface and core layers, indicating that plastic deformation is mainly concentrated in the surface region and its transmission to the interior of the cross-section is insufficient. The core and its surrounding frame-type segregation regions participate in deformation to a low degree, which is detrimental to the overall reconstruction and homogenization of the segregation morphology.

[0050] When the ratio of the equivalent strain average in the width direction to the height direction of the rolled piece cross-section deviates from 1 by more than 20% within the rolling pass interval, it is determined that the dominant factor affecting the evolution of the frame segregation morphology is insufficient deformation coordination in the width and height directions. When the deformation coordination in the width and height directions is insufficient, the difference in deformation distribution between the width and height directions of the rolled piece cross-section is too large. The plastic flow within the cross-section is mainly dominated by a single direction, making it difficult to form a multi-directional deformation state with alternating width and height directions. This is therefore unfavorable for obtaining balanced flow disturbance and redistribution opportunities in the corresponding region of frame segregation.

[0051] When the equivalent strain level of the region corresponding to the frame segregation is less than 80% of the average cross-sectional level within the rolling pass interval, the dominant factor affecting the morphological evolution of the frame segregation is determined to be insufficient flow participation. When flow participation is insufficient, the strain level of the region corresponding to the frame segregation is significantly lower than the overall cross-sectional average level. During rolling, it mainly passively deforms with the surrounding metal and fails to fully participate in local flow reconstruction, making it difficult to achieve morphological dispersion and spatial redistribution through compression, lateral flow, and local shearing. Based on the dominant factor, the rolling process for the corresponding rolling pass interval is adjusted.

[0052] By analyzing the metal flow behavior during each rolling pass, the dominant factors influencing the evolution of frame segregation morphology and their corresponding rolling pass intervals were identified. The rolling process for these dominant factors within their respective rolling pass intervals was then adjusted.

[0053] Specifically, in rolling passes where the degree of streamline reconstruction is insufficient, transition passes are added, the sequence of pass insertion is adjusted, and the cross-sectional change process is extended to increase the flow reconstruction opportunities and promote the bending and redistribution of the corresponding area of ​​frame segregation.

[0054] In rolling passes where core deformation penetration is insufficient, the reduction distribution is coordinated, the deformation path is extended, and the deformation bearing method of each pass is adjusted to improve the ability of deformation to be transferred to the interior of the cross section and enhance the plastic participation in the core and segregation areas.

[0055] In the rolling pass section where the deformation coordination in the width and height directions is insufficient, the turning rhythm, alternating pass configuration, and deformation bearing relationship in different directions are adjusted to optimize the flow of metal within the cross section.

[0056] In rolling passes with insufficient flow participation, multi-directional, phased deformation paths are constructed, along with increased transition deformation, adjusted pass combinations, and steel-turning methods, to enhance the local disturbance and redistribution capabilities of this region.

[0057] The above-mentioned adjustment measures are implemented in a coordinated manner around four aspects: streamline reconstruction, core deformation penetration, deformation coordination in width and height directions, and the degree of flow participation in the segregation area. By jointly adjusting the transition pass number, pass sequence, steel turning rhythm, and pressing distribution, all judgment indicators are improved towards the optimization target at the same time, thereby achieving comprehensive control over the segregation morphology of the frame type.

[0058] After adjusting the rolling process for the corresponding rolling pass interval based on the dominant factors, the process also includes: verifying the adjusted rolling process to evaluate its improvement effect on the frame-type segregation morphology. Specifically, this includes: rolling a rectangular continuously cast gear steel billet based on the adjusted rolling process, observing the microstructure of the rolled sample at low magnification, measuring the major and minor axis dimensions of the frame-type segregation characteristic region, and calculating its aspect ratio. The aspect ratio of the frame-type segregation characteristic region can be used to characterize its morphological directionality. A larger aspect ratio indicates a more pronounced elongation of the region along a certain direction, and a stronger directionality of the frame-type segregation; the closer the aspect ratio is to 1, the more uniform the morphology of the region, and the weaker the tendency to extend along a single direction.

[0059] When the aspect ratio of the frame-type segregation feature region in the optimized low-magnification microstructure decreases and approaches 1, it indicates that the optimized rolling process of this invention can effectively improve the morphological characteristics of the frame-type segregation feature region, weaken its directionality, and transform it from an elongated state to a more uniform morphology. Combined with on-site production results, when the trend of this indicator is consistent with the optimization target, it can be confirmed that the method of this invention has good feasibility and effectiveness.

[0060] In addition, before rolling, the rectangular continuous casting billet of gear steel is heated to a suitable temperature range for hot rolling. The heating regime before rolling is the same as the heating regime before rolling the rectangular continuous casting billet of gear steel that has frame-shaped segregation morphology problems after rolling. Conventional heating process for rolling gear steel bars can be adopted.

[0061] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0062] Example 1

[0063] In this embodiment, a rectangular continuously cast gear steel billet with an initial cross-section of 320×420 mm is selected as the original billet. The initial size of the segregation characteristic zone of the continuously cast billet frame is 220×140 mm. After conventional heating, it enters the rolling process and is rolled to 220 mm. (Reference) Figure 2 The aspect ratio of the low-magnification frame-type segregation feature region of the rolled product is 1.29. A finite element analysis model was established based on the original rolling process parameters. The original rolling process and the metal flow behavior of each pass under the original rolling process conditions are shown in the following table:

[0064] 1 A THERE IS 50 17 0.12 17 82 2 A OFF 40 15 0.15 18 85 3 A THERE IS 48 16 0.19 17 81 4 A OFF 51 15 0.20 20 80 5 B THERE IS 70 13 0.22 21 75 6 A OFF 75 14 0.21 23 79 7 C THERE IS 80 12 0.25 22 73

[0065] Analysis of the metal flow behavior during the rolling process revealed that, in the interval from the 5th to the 7th pass, the metal streamlines extend continuously along the rolling direction, and the bending angle of the streamlines is less than 15°.

[0066] There is a significant difference in equivalent strain between the core and the surface of the cross-section, with a difference greater than 0.20.

[0067] The equivalent strain deviation rate in the width and height directions exceeds 20%;

[0068] The equivalent strain level in the region corresponding to frame-type segregation is less than 80% of the average level of the cross-section.

[0069] The aspect ratio of the frame-type segregation feature region obtained from the final finite element method was 1.28, which is close to the aspect ratio of the frame-type segregation feature region in the actual rolled product at low magnification.

[0070] Based on the above analysis, the dominant factors affecting the evolution of the frame segregation morphology are: insufficient streamline reconstruction, insufficient core deformation penetration, insufficient coordination of deformation in the width and height directions, and insufficient flow participation in the 5th to 7th passes.

[0071] Based on the dominant factors, two transition passes are added between the 5th and 6th passes of the original process, increasing the total number of rolling passes to 9. (Reference) Figure 1 The original process, consisting of three passes (BAC) of rapid convergence in passes 5 to 7, was adjusted to a five-pass progressive convergence path (BABAC). The compression distribution was also adjusted, and a multi-directional deformation path was constructed in conjunction with the steel-turning operation. After the initial action of the B-type pass, the final forming stage is not directly entered. Instead, the cross-section is readjusted using the A-type pass, and the B-type pass is reintroduced, causing a further redistribution of lateral and longitudinal flow in the metal near the final fracture surface. Through the gradual convergence of the A-type and C-type passes, the final forming process is completed in stages, rather than a single rapid compression. With the combined action of steel-turning in each pass, the material participates in multiple deformation processes in both the width and height directions. A finite element analysis model was established based on the adjusted rolling process and the initial cross-sectional dimensions of the gear steel rectangular continuous casting billet to simulate the metal flow behavior during rolling. The adjusted rolling process and the metal flow behavior of each pass under the adjusted rolling process conditions are shown in the table below:

[0072] 1 A THERE IS 50 17 0.12 17 82 2 A OFF 40 15 0.15 18 85 3 A THERE IS 48 16 0.19 17 81 4 A OFF 51 15 0.20 20 80 5 B THERE IS 55 21 0.18 17 82 6 A OFF 56 20 0.20 20 80 7 B THERE IS 55 23 0.17 18 81 8 A OFF 15 45 0.08 12 85 9 C THERE IS 55 22 0.16 15 82

[0073] Simulation results show that, with the adjusted rolling process, the bending angle of the metal streamlines is increased to 20°–45° in each rolling pass; the difference in equivalent strain between the core and the surface layer is reduced to 0.08–0.20; the deviation rate of equivalent strain in the width and height directions is controlled within 20%; and the ratio of the average equivalent strain in the frame segregation region to the average equivalent strain of the cross section is not less than 80%.

[0074] refer to Figure 3 The aspect ratio of the frame-shaped segregation feature region was 1.13 in the final finite element method calculation.

[0075] refer to Figure 4Based on the adjusted rolling process, rectangular continuously cast billets of gear steel were rolled, and the microstructure of the rolled samples was observed at low magnification. The major and minor axis dimensions of the frame-type segregation feature region were measured, and its aspect ratio was calculated. The calculated aspect ratio of the frame-type segregation feature region in the actual low-magnification sample was reduced to 1.11, which is close to the simulation result. It is significantly lower than before optimization and closer to 1, effectively improving the morphology of the frame-type segregation and reducing its elongation trend along a single direction.

[0076] Example 2

[0077] In this embodiment, a rectangular continuously cast gear steel billet with an initial cross-section of 320×480 mm was selected as the original billet. The initial size of the frame-type segregation feature region of the continuously cast billet was 295×150 mm. After conventional heating, it entered the rolling process and was rolled to 220 mm. The aspect ratio of the frame-type segregation feature region of the rolled product at low magnification was 1.42. A finite element analysis model was established based on the original rolling process parameters. The original rolling process and the metal flow behavior of each pass under the original rolling process conditions are shown in the following table:

[0078] 1 A THERE IS 72 12 0.23 26 72 2 A OFF 73 13 0.22 28 75 3 A THERE IS 65 14 0.21 27 77 4 A OFF 61 13 0.21 26 78 5 B THERE IS 80 12 0.27 28 71 6 A OFF 78 13 0.25 30 73 7 C THERE IS 84 11 0.35 35 70

[0079] Analysis of the metal flow behavior during the rolling process revealed that, across all passes:

[0080] The bending angle of the metal streamlines is less than 15°;

[0081] There is a significant difference in equivalent strain between the core and the surface of the cross-section, with a difference greater than 0.20.

[0082] The equivalent strain deviation rate in the width and height directions exceeds 20%;

[0083] The equivalent strain level in the region corresponding to frame-type segregation is less than 80% of the average level of the cross-section.

[0084] The aspect ratio of the frame-type segregation feature region obtained from the final finite element method was 1.42, which is the same as the aspect ratio of the frame-type segregation feature region in the actual rolled product at low magnification.

[0085] Based on the above analysis, the dominant factors affecting the evolution of the frame segregation morphology are: insufficient streamline reconstruction, insufficient core deformation penetration, insufficient coordination of deformation in the width and height directions, and insufficient flow participation in the first to seventh passes.

[0086] The above results indicate that, under these larger cross-sectional conditions, the region corresponding to frame-type segregation is more sensitive to deformation distribution and metal flow state. This is because, as the initial cross-sectional size increases, the internal metal volume of the billet increases, the deformation transmission path between the surface and the core lengthens, and the difficulty of coordinating flow in the width and height directions increases. This leads to plastic deformation occurring preferentially in local areas, while its transmission to the interior of the cross-section and the segregation region lags behind. Therefore, problems such as insufficient streamline reconstruction, insufficient core deformation penetration, insufficient deformation coordination in the width and height directions, and insufficient flow participation in the segregation region persist throughout the rolling process and are further amplified during subsequent cross-sectional convergence, which is detrimental to improving the morphology of frame-type segregation.

[0087] Based on the dominant factors, the number of rolling passes was increased to 13. By combining the early-stage reduction distribution coordination with the increase of transition passes in the middle and later stages, the cross-sectional change process under larger cross-sectional conditions was made smoother, reducing the phenomenon of preferential surface deformation and lag in core response. At the same time, through the alternating action of the roll pass and the cooperation of the roll-over, the alternating flow and redistribution of metal in the width and height directions were enhanced, thereby improving the flow reconstruction capability and deformation coordination within the cross-section throughout the entire process.

[0088] The adjusted rolling process and the metal flow behavior of each pass under the adjusted rolling process conditions are shown in the table below:

[0089] 1 A THERE IS 32 25 0.13 15 85 2 A OFF 40 23 0.15 16 84 3 A OFF 40 22 0.12 15 83 4 A OFF 38 21 0.11 14 85 5 A THERE IS 60 16 0.18 20 80 6 A OFF 50 18 0.16 17 81 7 B THERE IS 45 24 0.15 16 82 8 A OFF 40 22 0.13 15 83 9 A OFF 30 27 0.12 13 86 10 A OFF 30 26 0.13 14 85 11 C THERE IS 43 28 0.14 15 83 12 B OFF 30 31 0.10 13 87 13 C THERE IS 27 50 0.08 12 86

[0090] Simulation results show that, with the adjusted rolling process, the bending angle of the metal streamlines is increased to 16°–50° in each rolling pass; the difference in equivalent strain between the core and the surface layer is reduced to 0.08–0.18; the deviation rate of equivalent strain in the width and height directions is controlled within 20%; and the ratio of the average equivalent strain in the frame segregation region to the average equivalent strain of the cross section is not less than 80%.

[0091] The aspect ratio of the frame-shaped segregation feature region was 1.19 in the final finite element analysis.

[0092] refer to Figure 4 Based on the adjusted rolling process, rectangular continuously cast billets of gear steel were rolled, and the microstructure of the rolled samples was observed at low magnification. The major and minor axis dimensions of the frame-type segregation feature region were measured, and its aspect ratio was calculated. The calculated aspect ratio of the frame-type segregation feature region in the actual low-magnification sample was reduced to 1.17, which is close to the simulation result. It is significantly lower than before optimization and closer to 1, effectively improving the morphology of the frame-type segregation and reducing its elongation trend along a single direction.

[0093] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present disclosure / the present invention, and these improvements and modifications should also be considered within the scope of protection of the present disclosure / the present invention.

Claims

1. A method for optimizing frame-type segregation rolling of rectangular continuous casting billets for gear steel based on metal flow behavior analysis, characterized in that, Includes the following steps: The initial cross-sectional dimensions and rolling process parameters of the rectangular continuous casting billet of gear steel with frame-shaped segregation morphology after rolling were obtained. A finite element analysis model is established based on the initial cross-sectional dimensions of the rectangular continuous casting billet of the gear steel and the rolling process parameters to simulate the metal flow behavior during the rolling process. The metal flow behavior during each rolling pass was analyzed to identify the dominant factors influencing the evolution of the frame segregation morphology. Based on the aforementioned dominant factors, the rolling process for the corresponding rolling pass intervals is adjusted.

2. The method for optimizing frame-type segregation rolling of rectangular continuous casting billets for gear steel based on metal flow behavior analysis according to claim 1, characterized in that, The metal flow behavior includes: The distribution and continuity of metal flow lines; Equivalent strain distribution in different regions of the rolled piece cross section; Coordination of metal flow in both width and height directions; The degree of flow participation and redistribution in the frame-type segregation region during the rolling process.

3. The method for optimizing frame-type segregation rolling of rectangular continuous casting billets for gear steel based on metal flow behavior analysis according to claim 2, characterized in that, In the analysis of the metal flow behavior during each rolling pass, the dominant factors influencing the evolution of frame segregation morphology were identified. When the metal streamlines extend continuously along the rolling direction within the rolling pass interval and the streamline bending angle is less than 15°, the dominant factors affecting the evolution of the frame segregation morphology are determined to be insufficient streamline reconstruction. When the equivalent variation between the core and the surface of the cross section is greater than 0.20 within the rolling pass interval, the dominant factors affecting the evolution of the frame segregation morphology are determined to be insufficient core deformation penetration. When the ratio of the equivalent strain average value in the width direction to the height direction of the rolled section deviates from 1 by more than 20% within the rolling pass interval, it is determined that the dominant factors affecting the evolution of the frame segregation morphology include insufficient deformation coordination in the width and height directions. When the equivalent strain level of the region corresponding to the frame segregation is less than 80% of the average cross-sectional level in the rolling pass interval, the dominant factor affecting the morphological evolution of the frame segregation is determined to be insufficient flow participation.

4. The method for optimizing frame-type segregation rolling of rectangular continuous casting billets for gear steel based on metal flow behavior analysis according to claim 3, characterized in that, The adjustment of the rolling process for the corresponding rolling pass range based on the aforementioned dominant factors includes: In the rolling pass intervals where the degree of streamline reconstruction is insufficient, increase the transition passes, adjust the sequence of pass entry, and extend the cross-sectional change process to increase the flow reconstruction opportunities and promote the bending and redistribution of the corresponding area of ​​frame segregation. In the rolling pass section where the core deformation penetration is insufficient, the deformation path is coordinated and extended, and the deformation bearing mode of each pass is adjusted to improve the ability of deformation to be transferred to the interior of the cross section and enhance the plastic participation of the core and segregation region. In the rolling pass section where the deformation coordination in the width and height directions is insufficient, the turning rhythm and alternating configuration of the roll pass are adjusted, and the deformation bearing relationship in different directions is improved to optimize the coordination of metal flow within the cross section. In rolling passes with insufficient flow participation, multi-directional, phased deformation paths are constructed, along with increased transition deformation, adjusted pass combinations, and steel-turning methods, to enhance the local disturbance and redistribution capabilities of this region.

5. The method for optimizing frame-type segregation rolling of rectangular continuous casting billets for gear steel based on metal flow behavior analysis according to claim 1, characterized in that, After adjusting the rolling process for the corresponding rolling pass range based on the aforementioned dominant factors, the process further includes: The adjusted rolling process was verified to evaluate its effect on improving the segregation morphology of the frame.

6. The method for optimizing frame-type segregation rolling of rectangular continuous casting billets for gear steel based on metal flow behavior analysis according to claim 5, characterized in that, The verification of the adjusted rolling process to evaluate its effect on improving the segregation morphology of the frame type includes: Based on the adjusted rolling process, the rectangular continuous casting billet of the gear steel is rolled, and the microstructure of the rolled sample is observed at low magnification. The major axis and minor axis dimensions of the frame segregation characteristic zone are measured, and its aspect ratio is calculated.

7. The method for optimizing frame-type segregation rolling of rectangular continuous casting billets for gear steel based on metal flow behavior analysis according to claim 6, characterized in that, The heating regime of the rectangular continuous casting billet of gear steel before rolling is the same as the heating regime of the rectangular continuous casting billet of gear steel with frame-shaped segregation morphology problem after rolling before rolling.

8. The method for optimizing frame-type segregation rolling of rectangular continuous casting billets for gear steel based on metal flow behavior analysis according to claim 1, characterized in that, The aspect ratio of the frame-type segregation feature area in the low magnification of the actual material of the rectangular continuous casting billet of the gear steel, which has a frame-type segregation morphology problem after rolling, is greater than 1.2.

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