Method for reducing internal cracks of soft reduction continuous casting billet
By optimizing the chamfer structure and stress distribution of the billet, the problem of internal cracks in the billet during continuous casting was solved, thereby improving the quality of the billet and the yield.
Patent Information
- Application Number
- CN202510845273.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-23
- Publication Date
- 2025-11-07
AI Technical Summary
During continuous casting, central cracks and V-shaped cracks are easily formed inside the billet, especially in thick billets with high alloy content, which affects the yield and product quality. Existing light reduction processes cannot effectively solve this problem.
By optimizing the chamfer structure of the billet and combining it with finite element numerical simulation analysis, the stress field is adjusted, the optimal chamfer angle and length are determined, the temperature field and stress state of the billet are optimized, and the formation of cracks during the light pressing process is reduced.
It significantly reduced the incidence of internal cracks in billets under light pressure, improved billet quality and yield, and enhanced product quality.
Smart Images
Figure CN120911162A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of continuous casting, in particular, especially relates to a method for reducing internal cracks of continuous casting billets with light press-down. BACKGROUND
[0002] In the continuous casting process, the molten steel is initially solidified to form a shell in the mold, then enters the secondary cooling zone for further solidification, and finally completes the center shrinkage in the light press-down area. However, due to uneven solidification shrinkage, inclusion segregation, stress concentration in the brittle temperature range (BTR), and other factors, internal center cracks and V-shaped cracks are easily formed in the billet, and such problems are more likely to occur in thick specifications and high alloy content steel billets, affecting the yield rate and the quality of the final product.
[0003] The traditional light press-down process is a method of applying a certain amount of compression deformation to the billet during the final solidification stage to reduce center segregation and shrinkage. The light press-down method is prone to stress concentration during deformation, and the depth of the effect is limited, which may cause local overpressure and exacerbate the formation of internal cracks. Currently, the improved methods for light press-down mainly include increasing the light press-down amount or optimizing the cooling strategy, but the effect is relatively limited. Therefore, how to optimize the stress state of the continuous casting billet and improve the uniformity of light press-down deformation has become the key to solving the crack problem. SUMMARY
[0004] To solve the above problems, the present application provides a method for reducing internal cracks of continuous casting billets with light press-down, which optimizes the continuous casting chamfering technology, improves the temperature of the slab corner, combines finite element numerical simulation analysis, changes the stress field at the end of slab solidification, and effectively compensates for the shrinkage caused by solidification. The optimal chamfer structure is selected through billet stress experiment, so that the press-down deformation is more uniform, and the internal crack occurrence rate is reduced. In industrial experiments, this method significantly reduces the internal crack occurrence rate of light press-down billets, and improves the billet quality and yield rate.
[0005] The technical means adopted by the present application are as follows: A method for reducing internal cracks of continuous casting billets with light press-down, specifically comprising the following steps: S1, establishing a three-dimensional finite element model including a billet and a pair of press-down rolls, the three-dimensional finite element model being used to simulate the stress distribution of the billet during the deformation process when the billet is subjected to light press-down processing under the press-down rolls; S2, designing multiple groups of light press-down processing parameters for the chamfer angle, each group using the same light press-down amount and chamfer length and different chamfer angles; Using the three-dimensional finite element model, the shear stress distribution of the billet in the brittle temperature range under each group of light press-down processing parameters is simulated, and the relationship between the chamfer angle and the maximum shear stress in the corresponding brittle temperature range is determined: as the chamfer angle increases, the maximum shear stress in the corresponding brittle temperature range gradually decreases; The slab light press-down processing experiment is carried out according to each group of light press-down processing parameters respectively, and the maximum chamfer angle corresponding to the situation that the longitudinal corner of the processed slab does not collapse is the optimal chamfer angle; S3, a plurality of groups of light press-down processing parameters are designed for the chamfer length, each group adopts the same light press-down amount as that in step S2, the optimal chamfer angle determined in step S2, and different chamfer lengths; A three-dimensional finite element model is adopted to simulate the tensile stress distribution of the slab in the brittle temperature range under each group of light press-down processing parameters, and the relationship between the chamfer length and the maximum tensile stress in the corresponding brittle temperature range is determined: the maximum tensile stress in the corresponding brittle temperature range gradually decreases with the increase of the chamfer length; and then the chamfer length at the minimum maximum tensile stress in the brittle temperature range is determined as the optimal chamfer length; S4, the slab is subjected to light press-down processing according to the optimal chamfer angle determined in step S2 and the optimal chamfer length determined in step S3.
[0006] Further, in the three-dimensional finite element model, the x-axis is the width direction of the slab, the y-axis is the thickness direction of the slab, and the z-axis is the continuous casting direction.
[0007] Further, when the light press-down processing parameters are designed in step S2, the chamfer angle is between 30°-60°.
[0008] Further, when the light press-down processing parameters are designed in step S3, the chamfer length is between 30mm-60mm.
[0009] Further, the optimal chamfer angle determined in step S2 is 45°, and the optimal chamfer length determined in step S3 is 60mm.
[0010] Compared with the prior art, the present application has the following advantages: The method for reducing internal cracks of light press-down continuous casting slab provided by the present application optimizes the chamfer structure of the slab, optimizes the temperature field of the corner of the slab, rapidly increases the temperature field of the chamfer surface, effectively avoids the solidification of the edge slab shell, optimizes the stress state of the slab, significantly reduces the deformation resistance, makes the press-down deformation more uniform, and reduces the internal defect rate of the slab. BRIEF DESCRIPTION OF DRAWINGS
[0011] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.
[0012] Figure 1A schematic diagram of the sampling position of the internally cracked casting blank for Example 1.
[0013] Figure 2 A schematic diagram of the boundary of the internal crack obtained by scanning the sample by an energy dispersive spectrometer (EDS) for Example 1.
[0014] Figure 3 A three-dimensional finite element model established in Example 1.
[0015] Figure 4 The shear stress distribution of the casting blank in the brittle temperature range under different chamfer angles for Example 1, wherein, Fig. (a) corresponds to the actual design, Fig. (b) corresponds to the chamfer angle of 30°, Fig. (c) corresponds to the chamfer angle of 40°, Fig. (d) corresponds to the chamfer angle of 45°, and Fig. (e) corresponds to the chamfer angle of 60°.
[0016] Figure 5 A graph of the maximum shear stress of the casting blank in the brittle temperature range with the change of the chamfer angle for Example 1.
[0017] Figure 6 The tensile stress distribution of the casting blank in the brittle temperature range under different chamfer lengths for Example 1, wherein, Fig. (a) corresponds to the actual design, Fig. (b) corresponds to the chamfer length of 30 mm, Fig. (c) corresponds to the chamfer length of 50 mm, and Fig. (d) corresponds to the chamfer length of 60 mm.
[0018] Figure 7 A graph of the maximum tensile stress of the casting blank in the brittle temperature range with the change of the chamfer length for Example 1.
[0019] Figure 8 The macrostructure photos of the carbon chamfered casting blank subjected to light press-down processing using the optimized chamfer structure for Example 1, wherein, Fig. (a) corresponds to the cross section of the casting blank, and Fig. (b) corresponds to the longitudinal section of the casting blank. DETAILED DESCRIPTION
[0020] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. The description of the at least one exemplary embodiment is actually only illustrative in nature and by no means as any limitation to the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the scope of protection of the present application.
[0021] The present application is directed to the problem that the light-pressed slab, especially the thick-gauge and high-alloy slab, is prone to crack during production, and provides a method for reducing internal cracks of light-pressed continuous casting slab, specifically comprising the following steps: S1, a three-dimensional finite element model including a slab and a pair of pressing rolls is established by using a finite element analysis software, and the three-dimensional finite element model is used to simulate the stress distribution of the slab during deformation when the slab is subjected to light-pressing under the pressing rolls; S2, a plurality of sets of light-pressing processing parameters are designed for the chamfer angle, each set adopts the same light-pressing reduction and chamfer length and different chamfer angles; The three-dimensional finite element model is used to simulate the shear stress distribution of the slab in the brittle temperature range under each set of light-pressing processing parameters, and the relationship between the chamfer angle and the maximum shear stress in the corresponding brittle temperature range is determined: the maximum shear stress in the corresponding brittle temperature range gradually decreases with the increase of the chamfer angle; The light-pressing processing experiment of the slab is carried out according to each set of light-pressing processing parameters respectively, and the maximum chamfer angle corresponding to the case that the longitudinal corner of the processed slab does not collapse is the optimal chamfer angle; S3, a plurality of sets of light-pressing processing parameters are designed for the chamfer length, each set adopts the same light-pressing reduction as step S2, the optimal chamfer angle determined in step S2, and different chamfer lengths; The three-dimensional finite element model is used to simulate the tensile stress distribution of the slab in the brittle temperature range under each set of light-pressing processing parameters, and the relationship between the chamfer length and the maximum tensile stress in the corresponding brittle temperature range is determined: the maximum tensile stress in the corresponding brittle temperature range gradually decreases with the increase of the chamfer length; and then the chamfer length at the minimum maximum tensile stress in the brittle temperature range is determined as the optimal chamfer length; S4, the light-pressing processing of the slab is carried out according to the optimal chamfer angle determined in step S2 and the optimal chamfer length determined in step S3, and the optimized chamfer angle and chamfer length can reduce the internal cracks of the continuous casting slab.
[0022] Further, in the three-dimensional finite element model, the x-axis is the width direction of the slab, the y-axis is the thickness direction of the slab, and the z-axis is the continuous casting direction.
[0023] Further, by adjusting the default threshold value in the three-dimensional finite element model that determines whether to average the stress calculation of the nodes, the smoothness and continuity of the obtained stress nephogram are controlled, so as to optimize the performance of the three-dimensional finite element model and the visualization effect of the simulation results.
[0024] Further, in the simulation process of steps S2 and S3, the calculation range of the three-dimensional finite element model covers the process from the entry of the slab into the pressing section to the complete solidification; other material parameters, boundary conditions, etc. can refer to the actual production data.
[0025] Furthermore, in step S2, when designing the light-pressure processing parameters, the chamfer angle is between 30° and 60°.
[0026] Furthermore, in step S3, when designing the light pressing processing parameters, the chamfer length is between 30mm and 60mm.
[0027] Furthermore, the optimal chamfer angle determined in step S2 is 45°, and the optimal chamfer length determined in step S3 is 60mm.
[0028] The method for reducing internal cracks in continuously cast billets under light pressure provided by this invention can reduce internal cracks caused by stress concentration and localized overpressure during the production process under light pressure. This method is based on mathematical modeling and finite element analysis, and involves experimental design to optimize the chamfer structure of the billet, optimize the temperature field at the corners of the billet, and adjust the stress distribution during solidification, thereby reducing localized stress concentration and ultimately reducing the formation of internal cracks in the billet. This method can achieve technical optimization without significantly altering existing continuous casting equipment, improving billet quality and yield, enhancing product quality, and boosting enterprise competitiveness.
[0029] In industrial experimental verification, the optimized chamfer angle and length using the method described in this invention significantly reduced the incidence of center cracks in the cast billet. Macroscopic microstructure photographs of medium-carbon chamfered cast billets under light pressure conditions observed in industrial experiments are shown below. Figure 8 As shown, the number of cracks in the central region of the slab is significantly reduced. This method optimizes the stress state of the slab, making the reduction deformation more uniform, reducing the incidence of internal cracks, and improving the quality of the slab. It is an effective improvement on traditional production methods and is suitable for the production of lightly reduced slabs with high quality requirements.
[0030] Example 1 Samples were taken from a cast billet with internal cracks at a steel plant. The sampling locations are as follows: Figure 1 As shown, Figure 1 In this diagram, BTR (Brittle temperature range) represents the brittle temperature range, Width represents the (cast billet) width, Thickness represents the (cast billet) thickness, Casting direction represents the continuous casting direction, corresponding to the z, x, and y axes respectively, and Sample position represents the sampling location, located on the yz plane. An energy dispersive spectroscopy (EDS) instrument was used to scan the internal crack boundaries of the sample; the scanning results are shown below. Figure 2As shown, crack propagation along the metal boundary is related to the local stress generated by deformation. If the internal crack is perpendicular to the stress axis, the initial crack will become the main factor causing further crack propagation, and carbon compounds will also accumulate near the crack boundary. The area indicated by the arrow in the figure is more prone to cracking due to the stress generated by solidification and thermal gradient, and a brittle phase can form in this area under these circumstances. When the crack edge has tensile stress (tensile stress is the stress generated when a material is stretched under external force, which usually leads to crack formation), this area will become a fracture-prone area.
[0031] This embodiment uses the method provided by the present invention to reduce internal cracks in continuously cast billets under light pressure and optimizes the chamfer structure processed under light pressure. Specifically, it includes the following steps: S1. Establish a three-dimensional finite element model including the billet and a pair of pressing rolls. The three-dimensional finite element model is used to simulate the stress distribution during the deformation process of the billet under light pressing rolls. In the three-dimensional finite element model, the x-axis is the width direction of the billet, the y-axis is the thickness direction of the billet, and the z-axis is the continuous casting direction. By adjusting the default threshold for determining whether the stress at the decision nodes is averaged in the three-dimensional finite element model, the smoothness and continuity of the obtained stress cloud map are controlled, thereby optimizing the performance of the three-dimensional finite element model and the visualization effect of the simulation results.
[0032] The three-dimensional finite element model established in this embodiment is as follows: Figure 3 As shown, in Figure 3 Different colors are used to represent the specific temperatures at different locations on the billet; in Example 1, the default threshold Avg for determining whether nodal stresses are averaged in the three-dimensional finite element model is set to 75%. S2. Four sets of light pressing processing parameters are designed for chamfer angles of 30°, 40°, 45° and 60°. Each set uses the same light pressing amount and chamfer length of 50mm. A three-dimensional finite element model was used to simulate the tensile stress distribution of the cast billet within the brittle temperature range under various light-pressure processing parameters, such as... Figure 4 As shown, the relationship between the chamfer angle and the maximum shear stress within the corresponding brittle temperature range was determined, and the results are as follows. Figure 5 As shown: with increasing chamfer angle, the maximum shear stress within the corresponding brittle temperature range gradually decreases; shear stress is the stress generated between adjacent layers within the material due to relative slippage, and its direction is parallel to the tangential surface of the material, rather than perpendicular to it; within the brittle temperature range, excessive shear stress may cause cracks to appear inside or on the surface of the cast billet, and reducing shear stress helps to reduce defects; with increasing chamfer angle, tensile stress transforms into compressive stress. Tensile stress is the stress generated when the material is stretched under external force, which usually leads to crack formation; compressive stress is the stress generated when the material is compressed under external force, and appropriate compressive stress helps to improve the central density of the cast billet; According to the light press-down processing parameters of each group, it is found that when the angle between the chamfer surface and the hot surface is greater than 45°, the longitudinal corner of the casting blank will collapse, so the optimal chamfer angle is determined to be 45° in this embodiment; S3, a plurality of light press-down processing parameters are designed for the chamfer length of 30mm, 50mm and 60mm, each group adopts the same light press-down amount as step S2 and the optimal chamfer angle of 45°, which can effectively reduce the press-down shear stress and convert the tensile stress into compressive stress, which helps to reduce the formation of cracks and improve the center density of the casting blank, and does not cause the collapse of the longitudinal corner of the casting blank; A three-dimensional finite element model is used to simulate the tensile stress distribution of the casting blank in the brittle temperature range under each group of light press-down processing parameters, as shown in Figure 6 It can be seen that the stress concentration in the corner area of the casting blank is reduced, and the relationship between the chamfer length and the maximum tensile stress in the corresponding brittle temperature range is determined, as shown in Figure 7 The maximum tensile stress in the corresponding brittle temperature range gradually decreases with the increase of the chamfer length; and the chamfer length at which the maximum tensile stress in the brittle temperature range is the smallest is determined as the optimal chamfer length, i.e. 60mm, which can reduce the tensile stress in the brittle temperature range and help to reduce the formation of cracks; S4, the deformation of the casting blank mainly occurs in the center area of the un-solidified zone, and the increase of the chamfer length can effectively avoid the solidification of the edge shell, so the use of the optimized chamfer length in the light press-down process can reduce the center segregation in the continuous casting process; the main internal cracks of the as-cast casting blank are affected by the maximum shear stress and tensile stress in the brittle temperature zone (BTR), and with the increase of the chamfer angle, the maximum shear stress and its influence range in the BTR region, and the maximum tensile stress are all reduced, so the optimized chamfer angle can reduce the center cracks of the continuous casting blank; in combination, the optimal chamfer design scheme is obtained, i.e. the optimal chamfer angle is 45° and the optimal chamfer length is 60mm.
[0033] Industrial verification experiments are carried out on a continuous casting machine in a certain steel plant, and the differences in the quality of the casting blanks under different schemes are compared, the chamfer is optimized by the method described in this embodiment, the optimal length of the optimized chamfer makes the temperature field of the chamfer surface rise rapidly, effectively avoids the solidification of the edge shell, and makes the press-down force concentrate in the center area of the casting blank, so in the light press-down process, the deformation resistance is significantly reduced, and the center density of the casting blank is significantly improved; in summary, the industrial experiment results show that the method described in the present application can effectively reduce the internal cracks of the light press-down continuous casting blank and improve the quality of the casting blank, which is an effective improvement of the traditional production method and is suitable for light press-down slab production with high quality requirements.
[0034] It should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.
Claims
1. A method of reducing internal cracks in a continuously cast billet with light press-down, characterized by, Specifically comprising the following steps: S1, establishing a three-dimensional finite element model comprising a casting blank and a pair of pinch rolls, the three-dimensional finite element model being used to simulate stress distribution in the deformation process of the casting blank when the casting blank is subjected to light press-down processing under the pinch rolls; S2, designing a plurality of groups of light press-down processing parameters for the chamfer angle, each group adopting the same light press-down amount and chamfer length and different chamfer angles; Using the three-dimensional finite element model, simulating the shear stress distribution of the casting blank in the brittle temperature range under each group of light press-down processing parameters, and determining the relationship between the chamfer angle and the maximum shear stress in the corresponding brittle temperature range: as the chamfer angle increases, the maximum shear stress in the corresponding brittle temperature range gradually decreases; Respectively, according to each group of light press-down processing parameters, the casting blank light press-down processing experiment is carried out, and the maximum chamfer angle corresponding to the longitudinal corner of the casting blank after processing without collapse is the optimal chamfer angle; S3, designing a plurality of groups of light press-down processing parameters for the chamfer length, each group adopting the same light press-down amount as step S2, the optimal chamfer angle determined in step S2, and different chamfer lengths; Using the three-dimensional finite element model, simulating the tensile stress distribution of the casting blank in the brittle temperature range under each group of light press-down processing parameters, and determining the relationship between the chamfer length and the maximum tensile stress in the corresponding brittle temperature range: as the chamfer length increases, the maximum tensile stress in the corresponding brittle temperature range gradually decreases; and further determining that the chamfer length at the minimum maximum tensile stress in the brittle temperature range is the optimal chamfer length; S4, according to the optimal chamfer angle determined in step S2 and the optimal chamfer length determined in step S3, the casting blank is subjected to light press-down processing.
2. The method of reducing internal cracking of a soft-reduced continuous cast billet according to claim 1, characterized by, In the three-dimensional finite element model, the x-axis is the width direction of the casting blank, the y-axis is the thickness direction of the casting blank, and the z-axis is the continuous casting direction.
3. The method of reducing internal cracking of a soft-reduced continuous cast billet according to claim 1, characterized by, When designing the light press-down processing parameters in step S2, the chamfer angle is between 30°-60°.
4. The method of reducing internal cracking of a soft-reduced continuous cast billet according to claim 3, characterized by, When designing the light press-down processing parameters in step S3, the chamfer length is between 30mm-60mm.
5. The method of reducing internal cracking of a soft-reduced continuous cast billet according to claim 4, characterized by, The optimal chamfer angle determined in step S2 is 45°, and the optimal chamfer length determined in step S3 is 60mm.