A method for improving the edge quality of hot-rolled strips of high-grade non-oriented silicon steel

Abstract

This invention belongs to the field of non-oriented silicon steel technology and discloses a method for improving the edge quality of hot-rolled strip steel of high-grade non-oriented silicon steel, including the following steps: 1) setting vertical rolls at the entrance of each stand of the finishing mill and giving a single-sided reference side pressure P. 基 ;2) Detect F i The real-time temperature of the strip at the frame inlet is used to obtain the lateral pressure coefficient L in the length direction. i And the lateral pressure coefficient W in the width direction i ;3) According to F i The thickness H of the strip at the frame entrance is used to obtain the thickness lateral compression coefficient H. i ;4) Select the compositional lateral pressure coefficient X based on the sum of the percentage contents X of Si and Als in the steel. i ;5) Calculate F i Real-time single-sided side pressure P of the vertical roller at the frame entrance i =P 基 ×L i ×W i ×H i ×X i The side pressure is dynamically adjusted based on the calculation results. This invention dynamically adjusts the side pressure of the vertical rolls at the entrance of each stand in the finishing mill to correct strip deviation and improve edge cracks, thereby achieving optimal edge quality.

Description

Technical Field

[0001] This invention belongs to the field of non-oriented silicon steel technology, specifically relating to a method for improving the edge quality of high-grade non-oriented silicon steel hot-rolled strip. Background Technology

[0002] Non-oriented silicon steel is a widely used soft magnetic material in the power and electronics industries. High-grade non-oriented silicon steel is mainly used to manufacture the cores of large and medium-sized motors and generators with large capacity. High-grade non-oriented silicon steel achieves its high magnetic induction and low iron loss properties by adding silicon and aluminum while reducing other alloying elements. Due to the low carbon and high silicon content in the steel, and the relatively low heating temperature required in the process, high-grade non-oriented silicon steel is mostly rolled in the fully ferrite region during hot rolling. This results in lower strip strength and thermoplasticity, making it prone to edge cracking defects during rolling. These edge cracking defects can easily lead to strip breakage during cold rolling, seriously jeopardizing the production quality and safety of the cold rolling process.

[0003] To prevent cold-rolled strip breakage caused by edge cracks in hot-rolled steel sheets, edge trimming is often required. However, this process reduces production efficiency and increases production costs. Therefore, it is necessary to find new methods to improve the edge quality of hot-rolled high-grade non-oriented silicon steel. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology by providing a method for improving the edge quality of hot-rolled strip of high-grade non-oriented silicon steel. Vertical rolls are set at the entrance of each stand of the finishing mill, and the lateral pressure of the vertical rolls is dynamically controlled during the rolling process to correct strip deviation and improve edge cracks, thereby obtaining the best edge quality and improving the efficiency of subsequent cold rolling production and product yield.

[0005] To address the technical problem proposed in this invention, this invention provides a method for improving the edge quality of high-grade non-oriented silicon steel hot-rolled strip, comprising the following steps:

[0006] 1) Install vertical rolls at the entrance of each stand in the finishing mill, and give a single-sided reference side pressure P. 基 ;

[0007] 2) Detection of F i The real-time temperature of the strip at the frame inlet is used to obtain the lateral pressure coefficient L in the length direction. i And the lateral pressure coefficient W in the width direction i ;

[0008] 3) According to F i The thickness H of the strip at the frame entrance is used to obtain the thickness lateral compression coefficient H. i ;

[0009] 4) Select the compositional lateral pressure coefficient X based on the sum of the percentage contents X of Si and Als in the steel. i ;

[0010] 5) Calculate F i Real-time single-sided side pressure P of the vertical roller at the frame entrance i =P 基 ×L i ×W i ×H i ×X i The lateral pressure is dynamically adjusted based on the calculation results.

[0011] In the above scheme, the F i The stand is the i-th stand of the finishing mill, where i = 1 to 7.

[0012] In the above scheme, in step 1), P 基 It is 40±5mm.

[0013] In the above scheme, in step 2), L i =T 均 / T i In the formula:

[0014] T i For F i Real-time temperature at the center of the strip width at the rack entrance;

[0015] T 均 For the entire length of the strip steel passing through F i The average real-time temperature at the width center of the rack entrance, since this parameter needs to be measured along the entire length of the strip through F. i Since the temperature can only be obtained after the machine frame is assembled, it has a time lag. Therefore, the average value of the real-time temperature at the center of the width across the entire length range measured once under the same production process is taken as T. 均 .

[0016] In the above scheme, in step 2), W i =T 边 / T 均 In the formula:

[0017] T 边 For the entire length of the strip steel passing through F i The average real-time temperature within a 10mm radius of the width edge at the rack entrance; this parameter needs to be measured along the entire length of the strip through F... i Since the temperature can only be obtained after the machine frame is assembled, it has a time lag. Therefore, the average value of the real-time edge temperature measured once over the entire length range under the same production process is taken as T. 边 .

[0018] In the above scheme, the real-time temperature detection frequency is: F iThe strip at the stand entrance is inspected every 1-3 meters as it advances during rolling.

[0019] In the above scheme, in step 3), H i =H / 50, where H is in mm.

[0020] In the above scheme, in step 4), X i The value ranges from 0.35 to 0.65.

[0021] Furthermore, in step 4), when 2.5% ≤ X < 3.0%, X i The value is 0.35–0.45; when 3.0% ≤ X < 3.7%, X i The value is 0.45–0.55; when 3.7% ≤ X < 4.5%, X i It ranges from 0.55 to 0.65.

[0022] The technical concept of this invention is as follows:

[0023] During the rolling process, the internal stress and strain of metal are closely related to temperature. For hot rolling, temperature is one of the most important factors affecting the metal's resistance to deformation. Strip steel undergoes different heat exchange processes at different stages on the hot rolling line, generally including air cooling, water cooling, heat exchange with the rolls, and heat preservation. When hot-rolled strip enters the finishing mill stand, it is often subjected to low-speed biting. To reduce the temperature difference between the head and tail of the strip, the hot rolling mill gradually accelerates the rolling process after biting at the head, thus reducing the temperature drop at the tail end. The strip temperature rises accordingly. Before the strip leaves the last stand at the tail end, the acceleration decreases, resulting in a slight decrease in the final rolling temperature at the tail end. Furthermore, the edges of the strip dissipate heat faster, exhibiting a significant temperature drop compared to the middle of the strip along its width. Therefore, the temperature drop in the length and width directions of the strip will cause fluctuations in rolling force and rolling instability along the length and width directions of the strip. In particular, due to temperature fluctuations, the temperature drop at the edges will be significant, which will cause inconsistent deformation with the center part during the rolling process, resulting in the formation of edge cracks. During the high-temperature rolling process, the cracks will gradually expand.

[0024] Regarding the temperature drop along the length of the strip, the finishing rolling temperature at the head of the strip is relatively low, therefore L i =T 均 / T i ≥1, at this point, increasing the side pressure of the vertical roll is beneficial for head heat preservation, promoting dynamic recrystallization of the edge deformation structure and closure of microcracks; while the tail finishing temperature is higher, therefore L i =T 均 / T i If the value is less than 1, the lateral pressure can be appropriately reduced.

[0025] Regarding the temperature drop in the width direction of the strip, if the temperature drop is too large and the edge temperature is too low, the resistance to deformation of the microstructure will increase. In this case, increasing the lateral pressure is beneficial to the edge deformation temperature rise, promoting dynamic recrystallization and microcrack closure at the edge. If the temperature drop at the edge is small and the edge temperature is high, the resistance to deformation of the microstructure will be low. In this case, the lateral pressure can be appropriately reduced.

[0026] The thickness of the strip before the entrance of each stand in the finishing mill also has a significant impact on the side pressure of the vertical rolls. As the number of rolling passes increases, the strip thickness gradually decreases, and the applied side pressure gradually decreases. If the side pressure is too large, it will cause the edge to be pressed onto the strip, resulting in edge defects such as iron sheet being pressed in.

[0027] Alloy composition is an important factor in determining the deformation resistance of hot-rolled strip steel during the hot rolling process. The higher the Si+Al content, the greater the deformation resistance, the higher the temperature required for dynamic recrystallization of the hot-rolled structure, and the greater the amount of lateral pressure required. This promotes plastic deformation and dynamic recrystallization of the hot-rolled edge, while also serving to polish the edge.

[0028] In addition, the alloy composition directly affects the thermal conductivity and heat dissipation capacity of the hot-rolled strip, thus affecting the temperature distribution along the length and width of the strip. Therefore, the influence of the alloy composition must also be taken into account when determining the side pressure of the vertical roll.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] This invention sets vertical rolls at the entrance of each stand in the finishing mill. Based on the chemical composition of high-grade non-oriented silicon steel, the thickness of the strip, and the temperature fluctuations in the length and width directions of the strip, the optimal real-time side pressure of the vertical rolls at the entrance of each stand is calculated. During the rolling process, the side pressure of the vertical rolls is dynamically controlled to suppress and weaken hot-rolled edge cracks, ultimately improving the edge quality of hot-rolled high-grade non-oriented silicon steel strips and increasing the efficiency of subsequent cold rolling production and product yield. Attached Figure Description

[0031] Figure 1 This is a microstructure diagram of the edge of a high-grade non-oriented silicon steel hot-rolled strip in Embodiment 1 of the present invention.

[0032] Figure 2 This is a microstructure diagram of the edge of a high-grade non-oriented silicon steel hot-rolled strip, which is Comparative Example 1-1 of this invention. Detailed Implementation

[0033] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0034] Example 1 and Comparative Example 1

[0035] The chemical composition of the high-grade non-oriented silicon steel hot-rolled strip in this embodiment is shown in Table 1.

[0036] Table 1 Chemical composition of steel in this embodiment

[0037] chemical composition C(％) Mn(%) S(％) P(％) N(％) Ti (%) Si (%) Als(%) content 0.0021 0.25 0.0013 0.03 0.0018 0.0015 3.05 1.15

[0038] Note: Balance is Fe and unavoidable impurities.

[0039] The production process of high-grade non-oriented silicon steel hot-rolled strip in this embodiment includes smelting billet → billet heating → rough rolling → F1-F7 seven-stand finishing rolling. The following methods are used to improve the edge quality of the hot-rolled strip:

[0040] 1) Install vertical rolls at the entrance of each stand in the finishing mill, and give a single-sided reference side pressure P. 基 =40mm;

[0041] 2) Detection of F i Real-time temperature T at the center of the strip width at the rack entrance i The entire length of the strip passes through F i The average real-time temperature T at the center of the width of the rack entrance 均 And the entire length of the strip passes through F i The average real-time temperature T within a 10mm width range of the rack entrance. 边 The real-time temperature is detected once every 1m of strip advance during rolling, and the lateral pressure coefficient L in the length direction is obtained. i =T 均 / T i And the lateral pressure coefficient W in the width direction i =T 边 / T 均 The results are shown in Table 2;

[0042] 3) According to F i The thickness H of the strip at the frame entrance is used to obtain the thickness lateral compression coefficient H. i =H / 50, see Table 3;

[0043] 4) Select the compositional lateral pressure coefficient X based on the sum of the percentage contents X of Si and Al in the steel. i See Table 3;

[0044] 5) Calculate F i Real-time side pressure P of the vertical roller at the frame inlet i =P 基 ×L i ×W i ×H i ×X i Based on the calculation results, the side pressure of the vertical roll was dynamically adjusted, and the edge morphology of the hot-rolled strip after finishing was observed. The results are shown in Table 4.

[0045] Table 2 shows the total length and partial location L in this embodiment. i and W i Calculation results

[0046]

[0047]

[0048] Table 3 H in this embodiment i and X i The value of

[0049] parameter <![CDATA[F1 frame]]> <![CDATA[F2 frame]]> <![CDATA[F3 Frame]]> <![CDATA[F4 frame]]> <![CDATA[F5 Rack]]> <![CDATA[F6 frame]]> <![CDATA[F7 frame]]> H 42 20 12 5 3.5 3.0 2.8 <![CDATA[H i ]]> 0.84 0.40 0.24 0.10 0.07 0.06 0.056 <![CDATA[X i ]]> 0.55～0.65 0.55～0.65 0.55～0.65 0.55～0.65 0.55～0.65 0.55～0.65 0.55～0.65

[0050] Table 4. Values ​​of the Examples and Comparative Examples and Corresponding Edge Morphology of Hot-Rolled Strip Steel

[0051]

[0052] The microstructure diagram of the edge of the high-grade non-oriented silicon steel hot-rolled strip corresponding to Example 1-1 is shown below. Figure 1 It can be seen that the hot-rolled strip obtained after measuring the pressure of each stand entrance vertical roll according to the calculated single-sided side pressure is smooth at the edge and has no obvious cracks; while the microstructure of Comparative Example 1-1, which did not set the vertical rolls according to this method, is shown in the figure. Figure 2 It can be seen that when no vertical roll is installed at the mill inlet, the hot-rolled edge is uneven and there are obvious inward-extending cracks; other comparative examples have vertical rolls installed, but the side pressure of the vertical rolls is not dynamically adjusted according to the real-time temperature of the strip. If the side pressure is too small, the cracks cannot be eliminated, and if the side pressure is too large, it will cause the edge to turn over, which in turn will cause the sheet metal to be pressed in.

[0053] Example 2 and Comparative Example 2

[0054] The chemical composition of the high-grade non-oriented silicon steel hot-rolled strip in this embodiment is shown in Table 5.

[0055] Table 5 Chemical composition of steel in this embodiment

[0056] chemical composition C(％) Mn(%) S(％) P(％) N(％) Ti (%) Si (%) Als(%) content 0.0024 0.32 0.0009 0.02 0.0022 0.0021 2.55 0.75

[0057] Note: Balance is Fe and unavoidable impurities.

[0058] The production process of high-grade non-oriented silicon steel hot-rolled strip in this embodiment includes smelting billet → billet heating → rough rolling → F1-F7 seven-stand finishing rolling. The following methods are used to improve the edge quality of the hot-rolled strip:

[0059] 1) Install vertical rolls at the entrance of each stand in the finishing mill, and give a single-sided reference side pressure P. 基 =40mm;

[0060] 2) Detection of F iReal-time temperature T at the center of the strip width at the rack entrance i The entire length of the strip passes through F i The average real-time temperature T at the center of the width of the rack entrance 均 And the entire length of the strip passes through F i The average real-time temperature T within a 10mm width range of the rack entrance. 边 The real-time temperature is detected once every 2m of strip advance during rolling, and the lateral pressure coefficient L in the length direction is obtained. i =T 均 / T i And the lateral pressure coefficient W in the width direction i =T 边 / T 均 The results are shown in Table 6;

[0061] 3) According to F i The thickness H of the strip at the frame entrance is used to obtain the thickness lateral compression coefficient H. i =H / 50, see Table 7;

[0062] 4) Select the compositional lateral pressure coefficient X based on the sum of the percentage contents X of Si and Al in the steel. i See Table 7;

[0063] 5) Calculate F i Real-time side pressure P of the vertical roller at the frame inlet i =P 基 ×L i ×W i ×H i ×X i Based on the calculation results, the side pressure of the vertical roll was dynamically adjusted, and the edge morphology of the hot-rolled strip after finishing was observed. The results are shown in Table 8.

[0064] Table 6 shows the total length and partial location L in this embodiment. i and W i Calculation results

[0065]

[0066]

[0067] Table 7 H in this embodiment i and X i The value of

[0068] parameter <![CDATA[F1 frame]]> <![CDATA[F2 frame]]> <![CDATA[F3 Frame]]> <![CDATA[F4 frame]]> <![CDATA[F5 rack]]> <![CDATA[F6 Frame]]> <![CDATA[F7 Frame]]> H 46 24 15 8 4.5 3.5 3.2 <![CDATA[H i ]]> 0.92 0.48 0.3 0.16 0.09 0.07 0.064 <![CDATA[X i ]]> 0.45～0.55 0.45～0.55 0.45～0.55 0.45～0.55 0.45～0.55 0.45～0.55 0.45～0.55

[0069] Table 8. Values ​​of the Examples and Comparative Examples and Corresponding Edge Morphology of Hot-Rolled Strip Steel

[0070]

[0071]

[0072] As shown in Table 8, the hot-rolled strip obtained by measuring the pressure of each stand entrance vertical roller according to the calculated single-sided side pressure in the embodiment of the present invention has a smooth edge without obvious cracks; while the edge of the comparative example 2-1, which did not set the vertical roller according to this method, is uneven, and the maximum crack depth is 0.9mm; although the other comparative examples set the vertical roller, they did not dynamically adjust the side pressure of the vertical roller according to the real-time temperature of the strip, which led to the generation of edge cracks or edge sheeting defects.

[0073] The above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, and any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for improving the edge quality of high-grade non-oriented silicon steel hot-rolled strip, characterized in that, Includes the following steps: 1) Set up vertical roll at the entry of each stand of finishing mill, give single side reference side pressure amount P 基 , P 基 = 40 ± 5 mm; 2) detecting F i real-time temperature T of the width center of the strip at the entry of the housing i , the strip full-length passing F i average value T of the real-time temperature of the width center at the entry of the housing 均 and the strip full-length passing F i average value T of the real-time temperature within the range of 10 mm of the width direction side at the entry of the housing 边 , obtaining length direction side pressure coefficient L i = T 均 / T i and width direction side pressure coefficient W i = T 边 / T 均 ; 3) According to F i The thickness H of the strip at the frame entrance, where H is in mm, is used to obtain the thickness lateral compression coefficient H. i =H / 50; 4) Select the compositional lateral pressure coefficient X based on the sum of the percentage contents X of Si and Als in the steel. i When 2.5% ≤ X < 3.0%, X i The value is 0.35~0.45; when 3.0%≤X<3.7%, X i The value is 0.45~0.55; when 3.7%≤X<4.5%, X i The value is 0.55~0.65; 5) Calculate F i Real-time single-sided side pressure P of the vertical roller at the frame entrance i =P 基 ×L i ×W i ×H i ×X i The lateral pressure is dynamically adjusted based on the calculation results.

2. The method for improving the edge quality of high-grade non-oriented silicon steel hot-rolled strip according to claim 1, characterized in that, The real-time temperature detection frequency is: F i The strip at the stand entrance is inspected every 1-3 meters as it advances during rolling.

3. The method for improving the edge quality of high-grade non-oriented silicon steel hot-rolled strip according to claim 1, characterized in that, The F i The stand is the i-th stand of the finishing mill, i=1~7.

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