A method for producing fine-blanking steel 65Mn-Cr continuous casting slab and controlling central segregation

Abstract

The application provides a fine blanking steel 65Mn-Cr continuous casting slab and a production method for controlling central segregation, and the key process for controlling central segregation of the fine blanking steel is formed through the synergic control of the argon blowing system in the smelting process, the LF tapping temperature, the tundish superheat, the optimization control of the continuous casting constant speed, the crystallizer weak cooling, the secondary cooling weak cooling, the electromagnetic stirring and the light pressing at the solidification end, compared with the prior art, the ideal fine blanking steel continuous casting slab macrostructure result is obtained, the central segregation degree of the casting slab is obviously reduced, the central segregation of the fine blanking steel 65Mn-Cr continuous casting slab reaches the C class 0.5 level or below, and the casting slab quality is obviously improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of steel production, and particularly relates to a production method of fine blanking steel 65Mn-Cr continuous casting slab and control of central segregation. BACKGROUND

[0002] In order to ensure the performance stability and part quality of fine blanking steel products, it is crucial to reduce banded structure and improve high cleanliness. The central segregation of the casting slab is the most important influencing factor, which can cause the internal composition of the casting slab to be uneven, and has a genetic influence on the uniformity of the structure and performance of the fine blanking steel plate.

[0003] A method for controlling central segregation of fine blanking steel 40MnB continuous casting slab is disclosed in a patent with the publication number CN 110656219 A published on January 7, 2020, 1) molten steel meeting the chemical composition of fine blanking steel 40MnB is smelted by top and bottom combined blowing converter and refined by LF furnace; 2) the molten steel is transported to the RH furnace for vacuum degassing treatment, and the other alloying elements in the molten steel except Mg are adjusted to the design composition range of fine blanking steel 40MnB, and magnesium alloy wire is fed into the molten steel before the molten steel leaves the RH furnace; 3) during the continuous casting process, the superheat degree of the molten steel in the tundish is controlled to be 15-25℃. The method reduces the production cost of fine blanking steel continuous casting slab, improves the quality of fine blanking steel continuous casting slab, and the central segregation level of the continuous casting slab is ≤0.5, and the man scale rating is ≤2.0 level. However, it does not disclose how to solve the problem of central segregation of fine blanking steel 65Mn-Cr continuous casting slab.

[0004] A method for controlling central segregation and porosity of fine blanking steel continuous casting slab is disclosed in a patent with the publication number CN 109550915 A published on April 2, 2019, which mainly aims at 16MnCr5 steel, and the measures taken are: 1) during the continuous casting process, the casting speed of the continuous casting machine is controlled to be 1.1-1.2 m / min, and the superheat degree of the molten steel in the tundish is controlled to be 20-30℃; 2) the continuous casting slab is subjected to light reduction at the solidification end, and the reduction rate of the light reduction at the solidification end is 0.56-1.1 mm / min, and the length of the reduction interval is 4.5-7.0 m. However, it also does not disclose how to solve the problem of central segregation of fine blanking steel 65Mn-Cr continuous casting slab. SUMMARY

[0005] The purpose of this invention is to provide a production method for fine-stamped 65Mn-Cr continuously cast slabs and to control center segregation. The steel grade of this invention has a carbon content of 0.64-0.68%, belonging to hypoeutectoid steel. This invention reduces center segregation in fine-stamped steel slabs by optimizing the argon blowing system during the smelting process, controlling the temperature at the refining station outlet, and optimizing the weak cooling process in the crystallizer and secondary cooling system, the two-stage electromagnetic stirring process within the fan-shaped section of the casting machine, and the light pressure process at the end of solidification. This further improves the center quality of the slab, enhances the 65Mn-Cr hot-rolled strip microstructure, and improves the quality of fine-stamped steel strip coils.

[0006] The specific technical solution of this invention is as follows:

[0007] The present invention provides a precision-stamped 65Mn-Cr continuous casting slab, comprising the following components by mass percentage:

[0008] C: 0.64-0.68wt%, Si: 0.20-0.37wt%, Mn: 0.95-1.10wt%, Cr: 0.13-0.22wt%, S < 0.01wt%, P ≤ 0.02wt%, Al: 0.006-0.030wt%, with the balance being Fe and unavoidable impurities.

[0009] This invention provides a production method for controlling center segregation in 65Mn-Cr continuous casting slabs for precision stamping, comprising the following steps:

[0010] 1) Smelting process;

[0011] 2) Continuous casting process;

[0012] 3) Weak cooling of the crystallizer;

[0013] 4) Second cold, weak cold;

[0014] 5) End-effector electromagnetic stirring;

[0015] 6) Lightly press down at the end of the solidification process in continuous casting.

[0016] The smelting process described in step 1) is as follows: after the LF refining is completed, the bottom blowing argon flow rate is 200-300 L / min and the soft blowing is 8 minutes or more, and the argon pressure is 0.3-0.4 MPa; the temperature of the molten steel leaving the station is: 55-65℃ for the first casting furnace and 35-55℃ for the continuous casting furnace.

[0017] Step 2) The continuous casting process specifically includes: constant casting speed control during continuous casting, with a target working speed of 0.95–1.15 m / min; superheat of the tundish in the initial casting furnace at 30–40°C, and superheat of the tundish in the continuous casting furnace at 10–30°C; immersion nozzle insertion depth in the crystallizer at 115–125 mm; vibration parameters: vibration frequency f = 150–20Vc, amplitude 3 mm.

[0018] Step 3) The crystallizer is weakly cooled, specifically: 450-500 L / min for the narrow face of the crystallizer and 3600-3900 L / min for the wide face of the crystallizer;

[0019] Step 4) The secondary cooling method specifically refers to a water volume of 0.3L / kg to 0.5L / kg.

[0020] Furthermore, in step 4), the secondary cooling water distribution ratio is as follows: foot roller secondary cooling water distribution ratio 13.0-18.6%, section 0 20.5-20.8%, section I 10.7-11.5%, section II 8.4-9.2%, section III 8.1-8.6%, section IV 9.7-10.6%, section V 7.1-9.5%, section VI 8.2-10.7%, section VII 4.2-4.8%, and section VIII 1.9-3.9%.

[0021] Step 5) The end electromagnetic stirring is specifically as follows: two-stage electromagnetic stirring is used. The first stage electromagnetic stirring position is the second section of the arc segment, with a casting speed of 0.95-1.15 m / min and a billet shell solidification thickness of 41.47-54.70 mm under weak cooling process conditions. The electromagnetic stirring current is 380-420 A and the frequency is 4.0 Hz. The second stage electromagnetic stirring position is the fourth section of the arc segment. At this time, the solid fraction at the center of the billet is 0.05-0.18, and the electromagnetic stirring current is 430-470 A and the frequency is 3.5 Hz.

[0022] The steel grade of this invention has a carbon content of 0.64-0.68%, belonging to hypoeutectoid steel and high-carbon steel. Its solidification process involves a wide two-phase region, a long solidification time in the mushy region, and significant shrinkage, resulting in severe center segregation and porosity defects in the cast billet. This invention employs a two-stage stirring + end-stage light reduction process. On the one hand, this effectively reduces the temperature gradient in the mushy region during the later stages of solidification, thereby reducing the size of the mushy region and the degree of segregation. On the other hand, accurate reduction at the end of solidification helps alleviate center porosity and segregation defects in the cast billet. The key feature of this invention lies in the optimal area of ​​the two-stage stirring and the accurate implementation of the end-stage reduction process.

[0023] Step 6) The light reduction at the end of the continuous casting solidification is as follows: The light reduction range at the end of the solidification is: the central solid fraction is 0.4-0.95, and the reduction amount in both stages is 5mm.

[0024] By optimizing and accurately controlling the refining, soft blowing, tapping temperature, crystallizer and secondary cooling weak cooling process, electromagnetic stirring process, and light reduction process, a fine-stamped steel continuous casting slab with an ideal low-magnification microstructure was obtained. Weak cooling was used in both the crystallizer and secondary cooling process, with a secondary cooling water volume of 0.3L / kg-0.5L / kg. A two-stage electromagnetic stirring system was employed within the fan-shaped section of the casting machine. The first stage of stirring aimed to control the solidification structure, with an optimal shell thickness of 40-55mm. The second stage of stirring aimed to control the homogenization of the slab core, with an optimal central solid fraction not exceeding 0.2%. As a crucial means of controlling center segregation, the light reduction interval at the end of solidification had a solid fraction of 0.4-0.95, and the total reduction from both stages was 5mm. This control method significantly improved the center segregation of the fine-stamped steel slab, with the center segregation not exceeding Class C, grade 1.0.

[0025] This invention produces fine-stamped steel continuously cast slabs using the above-mentioned technical solution. A cross-sectional sample of the slab is machined to a smooth, clean mirror finish. This sample is then immersed in a 1:1 hydrochloric acid aqueous solution at 70°C for 20 minutes. After pickling, the slab is graded under low magnification. Testing shows that the center segregation of the fine-stamped steel 65Mn-Cr continuously cast slab reaches below Class C, grade 0.5, proving the feasibility of this technical solution.

[0026] The control of center segregation in 230mm×1255mm cross-section continuous casting slabs of 65Mn-Cr fine-stamping steel is mainly achieved through the coordinated control of argon blowing regime during smelting, LF tapping temperature, and tundish superheat, as well as optimized control of processes such as constant casting speed, weak cooling in the crystallizer, weak cooling in the secondary cooling system, electromagnetic stirring, and light reduction at the end of solidification. These key processes form the core technology for controlling center segregation in fine-stamping steel. Compared with existing technologies, this invention achieves ideal low-magnification results for continuous casting slabs of fine-stamping steel, significantly reducing the degree of center segregation. The center segregation of 65Mn-Cr continuous casting slabs reaches below Class C 0.5, resulting in a significant improvement in slab quality. Attached Figure Description

[0027] Figure 1 Low-magnification microstructure of the cross-section of the continuously cast slab produced by the original method;

[0028] Figure 2 Low-magnification microstructure of the cross-section of the continuously cast slab produced in Example 1;

[0029] Figure 3 Low-magnification microstructure of the cross-section of the continuously cast slab produced in Example 2;

[0030] Figure 4 Low magnification microstructure of the cross-section of the continuously cast slab produced in Comparative Example 1. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0033] A production method for controlling center segregation in 65Mn-Cr continuous casting slabs (using the original method) includes the following steps:

[0034] When producing 65Mn-Cr continuous casting slabs for fine stamping steel using the original method, the composition is: C: 0.65wt%, Si: 0.35wt%, Mn: 0.99wt%, Cr: 0.17wt%, S: 0.004wt%, P: 0.010wt%, Al: 0.024wt%, with the balance being Fe. The production process steps are as follows:

[0035] 1) Steelmaking process: After LF refining, the bottom blowing argon flow rate is 190L / min, the soft blowing time is 7min, the argon pressure is 0.37MPa, the molten steel leaving the LF station, the superheat of the molten steel in the casting furnace is 50℃, and the superheat of the sample furnace is 30℃.

[0036] 2) Continuous casting process: The constant casting speed of the casting machine is 1.15m / min; the superheat of the tundish in the first casting furnace is 35℃, and the superheat of the tundish in the sampling furnace is 25℃;

[0037] 3) Cooling of the crystallizer: 550L / min for the narrow face of the crystallizer and 4200L / min for the wide face of the crystallizer. The temperature difference between the inlet and outlet water of the narrow and wide faces is 6.8℃ and 5.9℃, respectively.

[0038] 4) The immersion nozzle insertion depth of the crystallizer is 115-125 mm, and the vibration parameters are: vibration frequency f = 150-20Vc, amplitude 3 mm. The specific water flow rate for secondary cooling is 0.50 L / kg. The water distribution ratio of each zone in the secondary cooling system is shown in Table 1.

[0039] Table 1. Cold water distribution ratio (%) for Method 2 (original method)

[0040] foot roller 0 section I II III IV V VI VII VIII 13.69 22.52 10.48 8.38 10.21 9.82 11.31 10.49 1.3 1.8

[0041] 5) Electromagnetic stirring: Electromagnetic stirring in the fan-shaped one section, inlet and outlet two positions, stirring parameters are 400-450 A, 4.5 Hz.

[0042] 6) Light reduction at the end of solidification: The solid fraction in the reduction interval is 0.3-0.75, and the reduction sections are 8 and 9, with reductions of 2 mm and 1.0 mm respectively;

[0043] 7) The cross-section of the fine-stamped steel continuous casting slab obtained in Example 1 was machined into a smooth and clean mirror-finish sample. It was then immersed in a 1:1 hydrochloric acid aqueous solution at 70°C for 20 minutes. After pickling, the slab was subjected to low magnification as shown in the image. Figure 1 As shown.

[0044] Example 1

[0045] A production method for controlling center segregation in 65Mn-Cr continuous casting slabs of precision stamping steel. The produced continuous casting slabs have the following composition: C: 0.66wt%, Si: 0.31wt%, Mn: 1.05wt%, Cr: 0.19wt%, S: 0.001wt%, P: 0.018wt%, Al: 0.01wt%, with the balance being Fe.

[0046] Example 1: The production process includes the following steps:

[0047] 1) Steelmaking process: After LF refining, the bottom blowing argon flow rate is 260L / min, the soft blowing time is 10min, the argon pressure is 0.37MPa, the molten steel leaving the LF station, the superheat of the molten steel in the casting furnace is 65℃, and the superheat of the sample furnace is 43℃.

[0048] 2) Continuous casting process: The constant casting speed of the casting machine is 1.15m / min; the superheat of the tundish in the first casting furnace is 39℃, and the superheat of the tundish in the sampling furnace is 18℃.

[0049] 3) Cooling of the crystallizer: 500L / min for the narrow face of the crystallizer and 3900L / min for the wide face of the crystallizer. The temperature difference between the inlet and outlet water of the narrow and wide faces is 6.5℃ and 5.7℃, respectively.

[0050] 4) The immersion nozzle insertion depth of the crystallizer is 115-125 mm, and the vibration parameters are: vibration frequency f = 150-20Vc, amplitude 3 mm. The specific water flow rate for secondary cooling is 0.47 L / kg. The water distribution ratio of each zone in the secondary cooling is shown in Table 2.

[0051] Table 2. Cooling water distribution ratio (%) in Example 1

[0052] foot roller 0 section I II III IV V VI VII VIII 13.19 20.78 11.48 9.15 8.56 10.59 9.46 10.66 4.2 1.93

[0053] 5) End-stage electromagnetic stirring: Two-stage electromagnetic stirring is used. The first stage electromagnetic stirring position is the second section of the arc segment. When the casting speed is 1.15m / min, the solidified billet shell thickness is 41.47mm under this weak cooling process condition. The electromagnetic stirring current is 420A and the frequency is 4.0Hz. The second stage electromagnetic stirring position is the fourth section of the arc segment. At this time, the solidity at the center of the billet is 0.05 under this condition. The electromagnetic stirring current is 460A and the frequency is 3.5Hz.

[0054] 6) Lightly press down at the end of solidification: The solid fraction in the pressing interval is 0.4-0.95, and the pressing sections are 10 and 11, with pressing down of 3.0 mm and 2.0 mm respectively;

[0055] 7) The cross-section of the fine-stamped steel continuous casting slab obtained in Example 1 was machined into a smooth and clean mirror-finish sample, soaked in a 1:1 hydrochloric acid aqueous solution at 70°C for 20 minutes, and then the slab was graded at low magnification after pickling.

[0056] 8) As shown in Table 3, the center segregation of the billet can reach Class C 0.5 level.

[0057] Table 3. Statistics on Segregation Grade and Equiaxed Crystal Ratio of Cast Billets

[0058] Sample number Casting billet segregation rating Casting billet proportion of equiaxed crystal (%) 1 (north) C0.5 55 2 (middle) C1.0 50 3 (south) C0.5 53

[0059] Example 2

[0060] A method for producing a fine-stamped steel 65Mn-Cr continuous casting slab and controlling center segregation, wherein the continuous casting slab produced in Example 2 has the following composition: C: 0.65wt%, Si: 0.28wt%, Mn: 1.00wt%, Cr: 0.20wt%, S: 0.005wt%, P: 0.012wt%, Al: 0.015wt%, with the balance being Fe.

[0061] The production process includes the following steps:

[0062] 1) Steelmaking process: After the LF refining is completed, the bottom blowing argon flow rate is 210L / min, the soft blowing time is 10min, the argon pressure is 0.33MPa, the superheat of the molten steel leaving the LF station is 63℃, and the superheat of the molten steel leaving the LF station is 51℃.

[0063] 2) Continuous casting process: The constant casting speed of the casting machine is 0.95m / min; the superheat of the tundish in the first casting furnace is 38℃, and the superheat of the tundish in the second casting furnace is 26℃.

[0064] 3) Cooling of the crystallizer: 460L / min for the narrow face of the crystallizer and 3600L / min for the wide face of the crystallizer. The temperature difference between the inlet and outlet water of the narrow and wide faces is 6.4℃ and 5.5℃, respectively.

[0065] 4) The immersion nozzle insertion depth of the crystallizer is 115-125 mm, and the vibration parameters are: vibration frequency f = 150-20Vc, amplitude 3 mm. The specific water flow rate for secondary cooling is 0.31 L / kg, and the water distribution ratio of each zone in the secondary cooling is shown in Table 4.

[0066] Table 4. Cooling water distribution ratio (%) in Example 2

[0067] foot roller 0 section I II III IV V VI VII VIII 17.35 20.80 11.32 8.80 8.42 10.26 7.43 8.49 4.72 2.41

[0068] 5) End-stage electromagnetic stirring: Two-stage electromagnetic stirring is used. The first stage electromagnetic stirring position is the second section of the arc segment. When the casting speed is 0.955m / min, the solidified billet shell thickness is 54.70mm under this weak cooling process condition. The electromagnetic stirring current is 380A and the frequency is 4.0Hz. The second stage electromagnetic stirring position is the fourth section of the arc segment. At this time, the solidity of the billet center is 0.18 under this working condition. The electromagnetic stirring current is 440A and the frequency is 3.5Hz.

[0069] 6) Lightly press down at the end of solidification: The solid fraction in the pressing interval is 0.4-0.95, the pressing sections are sections 8 and 9, and the pressing is 2.5mm and 2.5mm respectively;

[0070] 7) The cross-section of the fine-stamped steel continuous casting slab obtained in Example 2 was machined into a smooth and clean mirror-finish sample, soaked in a 1:1 hydrochloric acid aqueous solution at 70°C for 20 minutes, and then the slab was graded at low magnification after pickling.

[0071] 8) As shown in Table 5, the center segregation of the billet can reach Class C 0.5.

[0072] Table 5. Statistics on Segregation Grade and Equiaxed Crystal Ratio of Cast Billets

[0073] Sample number Casting billet segregation rating Casting billet proportion of equiaxed crystal (%) 1 (north) C0.5 52 2 (middle) C0.5 47 3 (south) C0.5 51

[0074] Example 3

[0075] A method for producing a fine-stamped steel 65Mn-Cr continuous casting slab and controlling center segregation, wherein the continuous casting slab produced in Example 3 has the following composition: C: 0.67wt%, Si: 0.29wt%, Mn: 1.02wt%, Cr: 0.17wt%, S: 0.008wt%, P: 0.011wt%, Al: 0.008wt%, with the balance being Fe.

[0076] The production process includes the following steps:

[0077] 1) Steelmaking process: After the LF refining is completed, the bottom blowing argon flow rate is 290L / min, the soft blowing time is 8min, the argon pressure is 0.31MPa, the superheat of the molten steel leaving the LF station is 61℃, and the superheat of the molten steel leaving the LF station is 48℃.

[0078] 2) Continuous casting process: The constant casting speed of the casting machine is 1.05 m / min; the superheat of the tundish in the first casting furnace is 36℃, and the superheat of the tundish in the sampling furnace is 23℃;

[0079] 3) Cooling of the crystallizer: 480L / min for the narrow face of the crystallizer and 3800L / min for the wide face of the crystallizer. The temperature difference between the inlet and outlet water of the narrow and wide faces is 6.1℃ and 5.4℃, respectively.

[0080] 4) The immersion nozzle insertion depth of the crystallizer is 115-125 mm, and the vibration parameters are: vibration frequency f = 150-20Vc, amplitude 3 mm. The specific water flow rate for secondary cooling is 0.42 L / kg, and the water distribution ratio of each zone in the secondary cooling is shown in Table 6.

[0081] Table 6. Distribution ratio of secondary cooling water (%)

[0082] foot roller 0 section I II III IV V VI VII VIII 16.7 20.7 10.82 8.67 8.25 10.43 8.12 9.67 4.63 2.01

[0083] 5) End-effector electromagnetic stirring:

[0084] Two-stage electromagnetic stirring is used. The first stage of electromagnetic stirring is located in the second section of the arc. When the casting speed is 1.05 m / min, the solidified billet shell thickness is 46.52 mm under this weak cooling process condition. The electromagnetic stirring current is 410 A and the frequency is 4.0 Hz. The second stage of electromagnetic stirring is located in the fourth section of the arc. At this time, the solidity at the center of the billet is 0.10 under this condition. The electromagnetic stirring current is 470 A and the frequency is 3.5 Hz.

[0085] 6) Lightly press down at the end of solidification: The solid fraction in the pressing interval is 0.4-0.95, the pressing sections are 9 and 10, and the pressing is 2.0 mm and 3.0 mm respectively;

[0086] 7) The cross-section of the fine-stamped steel continuous casting slab obtained in Example 3 was machined into a smooth and clean mirror-finish sample, soaked in a 1:1 hydrochloric acid aqueous solution at 70°C for 20 minutes, and then the slab was graded at low magnification after pickling.

[0087] 8) As shown in Table 7, the center segregation of the billet can reach Class C 0.5.

[0088] Table 7. Statistics on Segregation Grade and Equiaxed Crystal Ratio of Cast Billets

[0089] Sample number Casting billet segregation rating Casting billet proportion of equiaxed crystal (%) 1 (north) C0.5 52 2 (middle) C0.5 50 3 (south) C0.5 53

[0090] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

[0091] Comparative Example 1

[0092] A method for producing a fine-stamped steel 65Mn-Cr continuous casting slab and controlling center segregation, wherein the continuous casting slab produced in Comparative Example 1 has the following composition: C: 0.64wt%, Si: 0.21wt%, Mn: 0.98wt%, Cr: 0.15wt%, S: 0.003wt%, P: 0.015wt%, Al: 0.022wt%, with the balance being Fe.

[0093] The production process includes the following steps:

[0094] 1) Steelmaking process: After the LF refining is completed, the bottom blowing argon flow rate is 281L / min, the soft blowing time is 8min, the argon pressure is 0.35MPa, the superheat of the molten steel leaving the LF station is 57℃, and the superheat of the molten steel leaving the LF station is 43℃.

[0095] 2) Continuous casting process: The constant casting speed of the casting machine is 1.05 m / min; the superheat of the tundish in the first casting furnace is 32℃, and the superheat of the tundish in the sampling furnace is 20℃;

[0096] 3) Cooling of the crystallizer: 485L / min for the narrow face of the crystallizer and 3820L / min for the wide face of the crystallizer. The temperature difference between the inlet and outlet water of the narrow face and the wide face is 6.2℃ and 5.3℃, respectively.

[0097] 4) The immersion nozzle insertion depth of the crystallizer is 115-125 mm, and the vibration parameters are: vibration frequency f = 150-20Vc, amplitude 3 mm. The specific water flow rate for secondary cooling is 0.42 L / kg. The water distribution ratio of each zone in the secondary cooling system is shown in Table 6.

[0098] Table 6. Distribution ratio of secondary cooling water (%)

[0099] foot roller 0 section I II III IV V VI VII VIII 16.8 20.6 10.78 8.67 8.29 10.42 8.13 9.67 4.64 2.00

[0100] 5) End-stage electromagnetic stirring: The parameters for the two-stage stirring are as follows: The current for the first-stage electromagnetic stirring is... 420A , frequency is 4.5 Hz The second stage of electromagnetic stirring uses a current of 450A and a frequency of [frequency value missing]. 4.0 Hz ;

[0101] 6) Light reduction at the end of solidification: The solid content in the reduction interval is... 0.3-0.75 The compression sections are 8 and 9, with compressions of 2.0mm and 3.0mm respectively;

[0102] 7) For the cross-sectional specimens of fine-stamped steel continuous casting slabs that do not meet the requirements of the test plan, the specimens are machined into smooth and clean mirror-finish specimens, soaked in a 1:1 hydrochloric acid aqueous solution at 70℃ for 20 minutes, and then the slabs are graded at low magnification after pickling.

[0103] 8) As shown in Table 8, the center segregation of the billet can reach Class C 0.5 level.

[0104] Table 8. Statistics on Segregation Grade and Equiaxed Crystal Ratio of Cast Billets

[0105] Sample number Casting billet segregation rating Casting billet proportion of equiaxed crystal (%) 1 (north) C2.0 52 2 (middle) B0.5 51 3 (south) C1.5 53

[0106] During the production test of Comparative Example 1, the center segregation control of the 65Mn-Cr fine stamping steel billet failed due to improper electromagnetic stirring parameters and inaccurate pressing position. Negative segregation was obvious and the center segregation defect was poor.

[0107] The data underlined above do not meet the requirements of this invention.

[0108] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A precision-stamped 65Mn-Cr continuously cast slab, characterized in that, The precision-stamped steel 65Mn-Cr continuous casting slab comprises the following composition by weight percentage: C: 0.64-0.68wt%, Si: 0.20-0.37wt%, Mn: 0.95-1.10wt%, Cr: 0.13-0.22wt%, S < 0.01wt%, P ≤ 0.02wt%, Al: 0.006-0.030wt%, with the balance being Fe and unavoidable impurities; The production method for controlling center segregation in the 65Mn-Cr continuous casting slab of precision stamping steel includes the following steps: 1) Smelting process; 2) Continuous casting process; 3) Weak cooling of the crystallizer; 4) Second cold, weak cold; 5) End-effector electromagnetic stirring; 6) Lightly press down at the end of the solidification process in continuous casting; The smelting process described in step 1) is as follows: after the LF refining is completed, the bottom blowing argon flow rate is 200~300L / min and the soft blowing is 8min or more, and the argon pressure is 0.3~0.4MPa; the temperature of the molten steel leaving the station is: 55~65℃ for the superheat of the casting furnace and 35~55℃ for the continuous casting furnace. Step 2) The continuous casting process specifically includes: constant casting speed control during continuous casting, with a target working casting speed of 0.95~1.15m / min; superheating of the tundish in the initial casting furnace at 30~40℃, and superheating of the tundish in the continuous casting furnace at 10~30℃. Step 3) The crystallizer is weakly cooled, specifically: 450~500 L / min for the narrow face of the crystallizer and 3600~3900 L / min for the wide face of the crystallizer; Step 4) The secondary cooling method specifically refers to a water volume of 0.3L / kg to 0.5L / kg. Step 5) The end electromagnetic stirring is specifically as follows: two-stage electromagnetic stirring is used. The first stage electromagnetic stirring position is the second section of the arc segment, with a casting speed of 0.95-1.15 m / min and a billet shell solidification thickness of 41.47~54.70 mm under weak cooling process conditions. The electromagnetic stirring current is 400 A and the frequency is 4.0 Hz. The second stage electromagnetic stirring position is the fourth section of the arc segment. At this time, the solidity at the center of the billet is 0.05~0.18, and the electromagnetic stirring current is 450 A and the frequency is 3.5 Hz. Step 6) The light reduction at the end of the continuous casting solidification is as follows: The light reduction range at the end of the solidification is: the central solid fraction is 0.4-0.95, and the reduction amount in both stages is 5mm.

2. A production method for controlling center segregation in 65Mn-Cr continuously cast slabs of precision stamping steel as described in claim 1, characterized in that, The production method includes the following steps: 1) Smelting process; 2) Continuous casting process; 3) Weak cooling of the crystallizer; 4) Second cold, weak cold; 5) End-effector electromagnetic stirring; 6) Lightly press down at the end of the solidification process in continuous casting; The smelting process described in step 1) is as follows: after the LF refining is completed, the bottom blowing argon flow rate is 200~300L / min and the soft blowing is 8min or more, and the argon pressure is 0.3~0.4MPa; the temperature of the molten steel leaving the station is: 55~65℃ for the superheat of the casting furnace and 35~55℃ for the continuous casting furnace. Step 2) The continuous casting process specifically includes: constant casting speed control during continuous casting, with a target working casting speed of 0.95~1.15m / min; superheating of the tundish in the initial casting furnace at 30~40℃, and superheating of the tundish in the continuous casting furnace at 10~30℃. Step 3) The crystallizer is weakly cooled, specifically: 450~500 L / min for the narrow face of the crystallizer and 3600~3900 L / min for the wide face of the crystallizer; Step 4) The secondary cooling method specifically refers to a water volume of 0.3L / kg to 0.5L / kg. Step 5) The end electromagnetic stirring is specifically as follows: two-stage electromagnetic stirring is used. The first stage electromagnetic stirring position is the second section of the arc segment, with a casting speed of 0.95-1.15 m / min and a billet shell solidification thickness of 41.47~54.70 mm under weak cooling process conditions. The electromagnetic stirring current is 400 A and the frequency is 4.0 Hz. The second stage electromagnetic stirring position is the fourth section of the arc segment. At this time, the solidity at the center of the billet is 0.05~0.18, and the electromagnetic stirring current is 450 A and the frequency is 3.5 Hz. Step 6) The light reduction at the end of the continuous casting solidification is as follows: The light reduction range at the end of the solidification is: the central solid fraction is 0.4-0.95, and the reduction amount in both stages is 5mm.

3. The production method according to claim 2, characterized in that, In step 4), the secondary cooling water distribution ratio is as follows: foot roller secondary cooling water distribution ratio 13.0~18.6%, section 0 20.5~20.8%, section I 10.7~11.5%, section II 8.4~9.2%, section III 8.1~8.6%, section IV 9.7~10.6%, section V 7.1~9.5%, section VI 8.2~10.7%, section VII 4.2~4.8%, and section VIII 1.9~3.9%.

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