A method for reducing the rolling force in producing high-strength pickled plates above 420MPa

Abstract

The present application relates to the technical field of steel rolling, and in particular to a method for reducing the rolling force of high-strength pickled plates above 420MPa; the method comprises: adjusting the composition of the slab to obtain a cast slab; subjecting the cast slab to pre-rolling heating, rough rolling and finish rolling to obtain a steel plate rolled with a low rolling force; wherein, the terminal temperature of the pre-rolling heating is controlled to increase by a first preset increase, the final rolling temperature of the finish rolling is controlled to increase by a second preset increase, and the outlet temperature of the rough rolling is controlled to increase by a third preset increase: by adjusting the composition of the slab, and then by respectively increasing the terminal temperature of the pre-rolling heating, the outlet temperature of the rough rolling and the temperature before the finish rolling, the risk of increasing the rolling force during the rolling stage is comprehensively reduced, thereby achieving a reduction in the rolling force.

Description

Technical Field

[0001] The present application relates to the technical field of steel rolling, and in particular to a method for reducing the pickling rolling force in producing high-strength steel of 420MPa or above. Background Art

[0002] The characteristics of high-strength steel are high strength and hardness. During the hot rolling stage, high-temperature heating is required to reduce the deformation resistance of high-strength steel during the rolling process, thereby improving the plasticity of high-strength steel. The product of high-strength steel - high-strength pickled plate generally uses a low-temperature process during the production process. This process will make the high-strength plate have a greater rolling force when rolling in the finishing mill, which will cause the oxide film of the roller to fall off due to the resonance of the rolling mill, affecting the quality of the strip; excessive rolling force will lead to reduced stability of the strip, which is prone to deviation and scrap accidents, as well as low control accuracy of the thickness of the strip head and other problems that restrict the performance of high-strength plates.

[0003] The root cause of the above problems is that the rolling force during the rolling process of high-strength steel is too large. Therefore, how to reduce the rolling force during the rolling process of high-strength steel is a technical problem that urgently needs to be solved. Summary of the invention

[0004] The present application provides a method for reducing the rolling force in producing high-strength plates above 420 MPa level, so as to solve the technical problem that the rolling force of high-strength steel is difficult to reduce in the prior art.

[0005] In a first aspect, the present application provides a method for reducing the rolling force for producing high-strength plates of 420 MPa or above, the method comprising:

[0006] Adjusting the composition of the slab to obtain a cast ingot;

[0007] The ingot is subjected to pre-rolling heating, rough rolling and finish rolling to obtain a steel plate rolled with a low rolling force;

[0008] The end point temperature of the pre-rolling heating is controlled to be increased by a first preset increase, the final rolling temperature of the finishing rolling is controlled to be increased by a second preset increase, and the outlet temperature of the rough rolling is controlled to be increased by a third preset increase;

[0009] The first preset temperature increase is 30° C. to 60° C., the second preset increase accounts for 50% to 65% of the first preset increase, and the third preset increase accounts for 2% to 10% of the first preset increase.

[0010] Optionally, the pre-rolling heating includes a preheating section, a first heating section, a second heating section and a soaking section, wherein the terminal temperature of the first heating section is increased by the first preset increase amount.

[0011] Optionally, the pre-rolling heating includes a preheating section, a first heating section, a second heating section and a soaking section, wherein the terminal temperature of the first heating section is increased by the first preset increase amount.

[0012] Optionally, adjusting the composition of the slab to obtain the cast slab specifically includes:

[0013] Controlling the Mn element content in the slab to decrease by a first preset amount;

[0014] Controlling the Nb element content in the slab to decrease by a second preset amount;

[0015] The Ti element content in the slab is controlled to increase by a third preset amount to obtain a cast slab.

[0016] Optionally, the first preset amount is 0.1% to 0.3%, the second preset amount is 0.01% to 0.04%, and the third preset amount is 0.03% to 0.06%.

[0017] Optionally, the finishing rolling includes: rolling in the form of a first group of finishing rolling stands, a second group of finishing rolling stands, a third group of finishing rolling stands, a fourth group of finishing rolling stands, a fifth group of finishing rolling stands, a sixth group of finishing rolling stands and a seventh group of finishing rolling stands, the roller diameters of the first group of finishing rolling stands to the fourth group of finishing rolling stands are 730 mm to 760 mm, and the roller diameters of the fifth group to the seventh group of finishing rolling stands are 630 mm to 660 mm.

[0018] Optionally, the rough rolling includes rolling in a manner of a first group of rough rolling stands and a second group of rough rolling stands, and the roll profile of the second group of rough rolling stands is a negative crown roll profile of -0.1 mm.

[0019] Optionally, the roll crown of the rough rolling work roll is 100 μm to 200 μm.

[0020] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0021] The embodiment of the present application provides a method for reducing the rolling force in producing high-strength plates of 420MPa or above. By first controlling the component content of the raw materials of the steel before casting, the microstructure changes in the subsequent rolling stage can be controlled, and then by respectively increasing the terminal temperature of heating before rolling, the outlet temperature of rough rolling and the temperature before finishing rolling, the microstructure change of the ingot can be further completed by increasing the temperature, avoiding the need for excessive pressing force to cause the microstructure change of the ingot, thereby achieving a reduction in rolling force. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 A schematic diagram of a process for a method provided in an embodiment of the present application;

[0025] Figure 2 A detailed flowchart of the method provided in the embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0027] In one embodiment of the present application, Figure 1 As shown, a method for reducing the rolling force for producing high-strength plates above 420 MPa is provided, the method comprising:

[0028] S1. Adjust the composition of the slab to obtain a cast slab;

[0029] S2. The ingot is subjected to pre-rolling heating, rough rolling and finish rolling to obtain a steel plate rolled by a low rolling force;

[0030] The end point temperature of the pre-rolling heating is controlled to be increased by a first preset increase amount, the final rolling temperature of the finishing rolling is controlled to be increased by a second preset increase amount, and the outlet temperature of the rough rolling is controlled to be increased by a third preset increase amount.

[0031] The first preset temperature increase is 30° C. to 60° C., the second preset increase accounts for 50% to 65% of the first preset increase, and the third preset increase accounts for 2% to 10% of the first preset increase.

[0032] In the embodiment of the present application, the positive effect of the first preset temperature increase of 30°C to 60°C is that by limiting the temperature increase of the first heating section, the microstructural changes of the ingot can be fully achieved in the pre-rolling heating stage, thereby promoting a complete transformation of the metallographic structure of the ingot, avoiding the additional rolling required for the metallographic structure to change again in the subsequent rolling process, thereby reducing the rolling force of the rolling process.

[0033] The positive effect of the second preset increase amount being 50% to 65% of the first preset increase amount is that within this ratio, the metallographic structure in the ingot before the finishing entrance can be fully transformed, thereby avoiding the need for additional rolling force for rolling due to incomplete transformation.

[0034] By adjusting the end point temperature of pre-rolling heating, the final rolling temperature of finishing rolling, and the exit temperature of rough rolling, the rolling force in each subsequent rolling process can be reduced by 3% to 15%.

[0035] In some embodiments, the terminal temperature of the pre-rolling heating is 1200°C to 1240°C, the final rolling temperature of the fine rolling is 870°C to 910°C, and the outlet temperature of the rough rolling is 1060°C to 1100°C.

[0036] In some embodiments, the pre-rolling heating includes a preheating section, a first heating section, a second heating section, and a soaking section, wherein the terminal temperature of the first heating section is increased by the first preset increase amount.

[0037] In some embodiments, Figure 2 As shown, the adjusting of the slab composition to obtain the cast slab specifically includes:

[0038] S11. Controlling the Mn element content in the slab to reduce a first preset amount;

[0039] S12. Controlling the Nb element content in the slab to reduce a second preset amount;

[0040] S13. Control the Ti element content in the slab to increase to a third preset amount to obtain a cast slab.

[0041] In some embodiments, the first preset amount is 0.1% to 0.3%, the second preset amount is 0.01% to 0.04%, and the third preset amount is 0.03% to 0.06%.

[0042] By adjusting the slab composition as described above, the rolling force in each subsequent rolling process can be reduced by 5% to 11%.

[0043] In some embodiments, the finishing rolling includes: rolling in the form of a first group of finishing rolling stands, a second group of finishing rolling stands, a third group of finishing rolling stands, a fourth group of finishing rolling stands, a fifth group of finishing rolling stands, a sixth group of finishing rolling stands and a seventh group of finishing rolling stands, the roller diameters of the first group of finishing rolling stands to the fourth group of finishing rolling stands are 730 mm to 760 mm, and the roller diameters of the fifth group to the seventh group of finishing rolling stands are 630 mm to 660 mm.

[0044] In the present application, the roller diameters of the first to fourth finishing rolling stands are 730 mm to 760 mm, and the positive effect is that within the diameter range, the diameter is smaller than that of the general finishing rolling process, and the rolling force can be reduced by 6-10% for every 20 mm reduction in roller diameter, thereby ensuring that the rolling force in the front section of the finishing rolling is sufficient, and at the same time, in conjunction with the previous process, the rolling force required for rolling can be fully reduced.

[0045] The positive effect of the roller diameter of the fifth to seventh finishing mill stands being 630mm to 660mm is that within this diameter range, the rolling force in the latter stage of finishing rolling can be guaranteed to be sufficient and reasonable, and products with qualified performance can be obtained, while the rolling force in the latter half can be reduced.

[0046] In some embodiments, the rough rolling includes rolling in a manner of a first group of rough rolling stands and a second group of rough rolling stands, wherein the roll profile of the second group of rough rolling stands is a negative crown roll profile of -0.1 mm.

[0047] In the present application, the positive effect of the roller profile of the second group of rough rolling stands being a negative convex roller profile of -0.1 mm is that within the range of the negative convexity, the rolling force during the rough rolling process can be made uniform, thereby preventing the generation of intermediate waves in the subsequent finishing rolling process; when the negative convexity value is less than the maximum value of the endpoint of the range, the adverse effect that will be caused is to prevent the generation of intermediate waves during the finishing rolling process. Too small a negative convexity will result in insufficient rolling force during the rough rolling process, resulting in the finishing rolling process requiring a larger set bending roll force, thereby increasing the rolling force of the finishing rolling.

[0048] In some embodiments, the target crown of the rough rolling is 100 μm to 200 μm.

[0049] Example 1

[0050] like Figure 2 As shown, a method for reducing the rolling force for producing high-strength plates above 420 MPa level, the method comprising:

[0051] S11. Controlling the Mn element content in the slab to reduce a first preset amount;

[0052] S12. Controlling the Nb element content in the slab to reduce a second preset amount;

[0053] S13. Control the Ti element content in the slab to increase the third preset amount to obtain a cast slab;

[0054] S2. The ingot is heated before rolling, rough rolled and finish rolled to obtain a steel plate rolled by a low rolling force;

[0055] Among them, the terminal temperature of pre-rolling heating is controlled to increase by a first preset increase, the final rolling temperature of finishing rolling is controlled to increase by a second preset increase, and the outlet temperature of rough rolling is controlled to increase by a third preset increase.

[0056] The pre-rolling heating includes a preheating section, a first heating section, a second heating section and a soaking section, wherein the terminal temperature of the first heating section is increased by a first preset increase amount, and the first preset temperature increase amount is 40°C.

[0057] The ratio of the second preset increase amount to the first preset increase amount is 60%, and the ratio of the third preset increase amount to the first preset increase amount is 5%.

[0058] The first preset amount is 0.2%, the second preset amount is 0.03%, and the third preset amount is 0.05%.

[0059] Finishing rolling includes: rolling in the form of a first group of finishing rolling stands, a second group of finishing rolling stands, a third group of finishing rolling stands, a fourth group of finishing rolling stands, a fifth group of finishing rolling stands, a sixth group of finishing rolling stands and a seventh group of finishing rolling stands, the first group of finishing rolling stands having a roll diameter of 759.5 mm, the second group of finishing rolling stands having a roll diameter of 755.4 mm, the third group of finishing rolling stands having a roll diameter of 746.1 mm, the fourth group of finishing rolling stands having a roll diameter of 733.8 mm, the fifth group of finishing rolling stands having a roll diameter of 647.3 mm, the sixth group of finishing rolling stands having a roll diameter of 631.2 mm and the seventh group of finishing rolling stands having a roll diameter of 657.6 mm.

[0060] Among them, the pressure of each group of finishing mill stands is shown in Table 1.

[0061] Table 1

[0062]

[0063] The rough rolling includes rolling in a first group of rough rolling stands and a second group of rough rolling stands, and the roll profile of the second group of rough rolling stands is a negative crown roll profile of -0.1 mm.

[0064] The target convexity of finishing rolling is increased by 15μm, so the bending roll force of the first to fourth sets of stands of finishing rolling is reduced in the control model, and the reduction amount is 100KN-250KN.

[0065] Comparative Example 1

[0066] Comparing Comparative Example 1 with Example 1, the difference between Comparative Example 1 and Example 1 is:

[0067] Instead of using the method of this application, the conventional rolling method is directly adopted. The "High-strength Pickled Plate Production Implementation High-strength Pickled Plate Control Plan--2020" specifically includes:

[0068] The temperature out of the heating furnace before rolling is 1220±20℃, and the time in the furnace is not less than 240min. Under normal circumstances, the heating temperature is 1120±10℃;

[0069] The rough rolling adopts 1+5 rolling mode, the rough rolling descaling is not less than 3 passes, the rough rolling outlet temperature is controlled to be 1080±20℃, the rough rolling roll profile crown is -0.3mm, and the intermediate billet thickness is not less than 33mm;

[0070] The finishing rolling adopts double descaling, speed-up rolling, final rolling temperature of 890±20℃, convexity requirement of 50±10μm, high-speed steel roll diameter of not less than 725mm, finishing rolling calibration stiffness difference of not more than 150KN, stiffness of not less than 2500KN, and rolling force data of each group of finishing mills are shown in Table 2.

[0071] Table 2

[0072]

[0073] Comparative Example 2

[0074] Comparing Comparative Example 2 with Example 1, the difference between Comparative Example 2 and Example 1 is:

[0075] The method of adjusting the slab composition is not adopted, that is, the content of Mn and Nb elements is not reduced, and the content of Ti element is not increased. The pressing force of each finishing mill group is shown in Table 3.

[0076] Table 3

[0077]

[0078] Comparative Example 3

[0079] Comparing Comparative Example 3 with Example 1, the difference between Comparative Example 3 and Example 1 is:

[0080] Without reducing the roll diameter in the finishing rolling stage, the roll diameters and corresponding rolling forces of each finishing mill group are shown in Table 4.

[0081] Table 4

[0082]

[0083]

[0084] Comparative Example 4

[0085] Comparing Comparative Example 4 with Example 1, the difference between Comparative Example 4 and Example 1 is:

[0086] The roll profile of the second group of rough rolling stands is not set to a negative convex roll profile of -0.1 mm, and the target convexity of finishing rolling is increased by 15 μm. Therefore, the bending roll force of the first to fourth groups of stands of finishing rolling is reduced in the control model, and the reduction amount is 100 KN to 250 KN. The specific reduction is shown in Table 5.

[0087] Table 5

[0088] category F1(KN) F2(KN) F3(KN) F4(KN) Bending roll force 1 1256 1028 718 848 Rolling force 1 15213 16138 15379 14189 Bending roll force 2 1367 1244 980 1005 Rolling force 2 16324 17018 16172 14850 Reduced rolling force 1111 880 793 661 Reduced bending force 111 216 262 157

[0089] Comparative Example 5

[0090] Comparing Comparative Example 5 with Example 1, the difference between Comparative Example 5 and Example 1 is:

[0091] The end point temperature of pre-rolling heating, the outlet temperature of rough rolling and the final rolling temperature of finishing rolling are not increased. The specific conditions are shown in Table 6.

[0092] Table 6

[0093]

[0094] Related experiments:

[0095] For strip steel of the same specification, the methods of Examples 1-3 and Comparative Examples 1-5 were used for preparation, and the total reduction in rolling force during the finishing rolling process was detected. At the same time, the obtained products were tested for qualification. The results are shown in Table 7. At the same time, the method of Example 1 was subdivided, and the rolling force of each group of stands was detected, and the reduction in rolling force was calculated. The results are shown in Table 8.

[0096] Detection methods for related experiments:

[0097] The rolling force detection is all carried out using the rolling mill's own pressure head (model: SLC2040-30). The pressure head is from the same manufacturer, has the same specifications and parameters, and has a service life of 24 months.

[0098] Table 7

[0099] category Total reduction in rolling force (%) Is the product qualified? Example 1 - qualified Comparative Example 1 13.54％ qualified Comparative Example 2 7.59％ qualified Comparative Example 3 3.7％ qualified Comparative Example 4 5.33％ qualified Comparative Example 5 5.98％ qualified

[0100] Table 8

[0101]

[0102] Detailed analysis of Table 1:

[0103] The total reduction in rolling force refers to the degree of reduction in the average rolling force over the entire length during the finishing rolling process. The higher the total reduction in rolling force, the more the rolling force is reduced during the finishing rolling process.

[0104] The reduction in rolling force refers to the degree of reduction in the full-length average rolling force of each group of stands during the finishing rolling process. The higher the reduction in rolling force, the more the rolling force of the corresponding stand is reduced.

[0105] From the data of Example 1, it can be seen that:

[0106] If the method of the present application is adopted, by adjusting the composition of the slab and then respectively increasing the terminal temperature of heating before rolling, the exit temperature of rough rolling and the temperature before finishing rolling, the risk of increasing the rolling force during the rolling stage can be comprehensively reduced, and the reduction of the rolling force can be effectively achieved.

[0107] From the data of Comparative Examples 1-5, it can be seen that:

[0108] If the method of the present application is not adopted, that is, if the composition of the slab is not adjusted, the terminal temperature of heating before rolling is not increased, the outlet temperature of rough rolling is not increased, and the temperature before finishing rolling is not increased, it is difficult to comprehensively achieve a reduction in rolling force.

[0109] One or more technical solutions in the embodiments of the present application also have at least the following technical effects or advantages:

[0110] (1) The method provided in the embodiment of the present application adjusts the composition of the slab and then respectively increases the terminal temperature of heating before rolling, the exit temperature of rough rolling and the temperature before finishing rolling, thereby comprehensively reducing the risk of increasing the rolling force during the rolling stage and achieving a reduction in the rolling force.

[0111] (2) In the method provided in the embodiment of the present application, although the reduction in rolling force did not reach the designed comprehensive level due to reasons such as steel type and specification, perhaps due to the gap between actual and individual tests, the experimental goal has been achieved and the rolling force of the rolling process has been reduced.

[0112] (3) The method provided in the embodiment of the present application not only reduces the rolling force during the rolling process, but also improves the stability of strip rolling, and no unstable rolling conditions such as folding and tail swinging occur during the rolling process.

[0113] (4) The parameters set in the method provided in the embodiment of the present application can be integrated into the automatic rolling process, so as to further accurately control the progress of the rolling process and further reduce the rolling force.

[0114] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0115] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for reducing the rolling force for producing high-strength plates above 420 MPa, characterized in that: The method comprises: Adjusting the composition of the slab to obtain a cast ingot; The ingot is subjected to pre-rolling heating, rough rolling and finish rolling to obtain a steel plate rolled with a low rolling force; The terminal temperature of the first heating section of the pre-rolling heating is controlled to increase by a first preset increase, the final rolling temperature of the finishing rolling is controlled to increase by a second preset increase, and the outlet temperature of the rough rolling is controlled to increase by a third preset increase; The first preset increase is 30°C to 60°C, the second preset increase accounts for 50% to 65% of the first preset increase, and the third preset increase accounts for 2% to 10% of the first preset increase; The pre-rolling heating includes a preheating section, a first heating section, a second heating section and a soaking section. The step of adjusting the composition of the slab to obtain the cast slab specifically includes: controlling the Mn element content in the slab to decrease by 0.1% to 0.3%; Control the Nb content in the slab to reduce by 0.01%~0.04%; The Ti content in the slab is controlled to increase by 0.03% to 0.06% to obtain a cast slab; The finishing rolling comprises: rolling in the form of a first group of finishing rolling stands, a second group of finishing rolling stands, a third group of finishing rolling stands, a fourth group of finishing rolling stands, a fifth group of finishing rolling stands, a sixth group of finishing rolling stands and a seventh group of finishing rolling stands, wherein the roller diameters of the first group of finishing rolling stands to the fourth group of finishing rolling stands are 730 mm to 760 mm, and the roller diameters of the fifth group of finishing rolling stands to the seventh group of finishing rolling stands are 630 mm to 660 mm; The rough rolling includes rolling in a first group of rough rolling stands and a second group of rough rolling stands, wherein the roll profile of the second group of rough rolling stands is a negative crown roll profile of ≥-0.1 mm.

2. The method according to claim 1, characterized in that The end point temperature of the pre-rolling heating is 1200°C to 1240°C, the final rolling temperature of the fine rolling is 870°C to 910°C, and the outlet temperature of the rough rolling is 1060°C to 1100°C.

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