A control method for improving tail quality of thin-gauge high-strength steel

Abstract

The application discloses a control method for improving tail quality of thin-gauge high-strength steel, and the method comprises the following steps: calibrating parameters of a rough rolling mill and a finishing mill; adjusting the distance between the head tail of the intermediate billet in the rough rolling mill and the rolling center line, and setting the tail short stroke value of the entry side guide plate of the finishing mill; based on the calibrated rolling mill parameters, when the tail of the thin-gauge high-strength steel is rolled, the short stroke value is increased based on the set tail short stroke value of the entry side guide plate of the finishing mill, the parameters of the automatic opening of the entry side guide plate of the finishing mill are set, and the parameters of the roll gap of the finishing mill are set. The application can solve the local folding, one-side tail flinging and rolling failure caused by the inconsistent extension of the two sides of the strip steel due to the temperature, rolling pressure, abnormal plate shape adjustment and the like in the actual production process, and the production efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hot-rolled strip production, in particular to a control method for improving the tail quality of thin-gauge high-strength steel. BACKGROUND

[0002] “Hot instead of cold” steel is the main result of the current development of hot continuous rolling technology and the main means of reducing carbon emissions in the steel industry. Steel enterprises and downstream users need a large amount of “hot instead of cold” steel from the comprehensive consideration of carbon emissions and costs. In particular in the automobile industry, thin-gauge high-strength steel is the main means of automobile lightweighting, which can significantly reduce the weight of the automobile while ensuring the strength of the automobile, and is the main means of cost savings. Therefore, the market demand for thin-gauge high-strength steel increases year by year.

[0003] However, thin-gauge high-strength steel has poor stability in the production process due to high strength and large rolling pressure. In particular, the tail shape of the strip is extremely difficult to control when the tail temperature of the hot-rolled strip decreases, the rolling force rises rapidly, and the restraining effect of tension on the shape disappears. Abnormalities such as tail throwing and rolling are frequently occurring in the production process, which worsens the tail quality and, in severe cases, requires roll replacement, affecting the efficiency of the rolling line.

[0004] The current control of thin-gauge tail quality is mainly from the rolling force, such as a method for improving the head or tail shape quality of hot-rolled strip (application number: 201110296426.2), which optimizes the switching of the bending roll force at the head and tail of the hot-rolled strip to control the shape and avoid abnormalities such as rolling. A method for improving the tail quality of hot-rolled strip (application number: CN201811572757.2) controls the closing timing of lubrication rolling to reduce the rolling force fluctuation of the strip tail and avoid quality problems caused by the intensification of the tail wave.

[0005] However, the above measures control the tail quality under uniform deformation conditions. In actual production, the tail has inconsistent elongation due to temperature, rolling pressure, and other factors, resulting in non-uniform deformation. In severe cases, it can cause one-sided tail throwing and rolling, which requires roll replacement and seriously affects production efficiency. Measures need to be taken to control and solve the above problems. SUMMARY

[0006] The present application aims to provide a control method for improving the tail quality of thin-gauge high-strength steel. To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] A control method for improving the tail quality of thin-gauge high-strength steel, characterized in that the method comprises,

[0008] Calibrating parameters of roughing mill and finishing mill: adjusting the distance between the head and tail of the intermediate billet in the roughing mill deviating from the rolling center line, and setting the short stroke value of the tail of the entry side guide plate of the finishing mill;

[0009] Based on the calibrated rolling mill parameters, when rolling the tail of the thin gauge high strength steel, the short stroke value is increased by 20-40 mm based on the set short stroke value of the tail of the entry side guide plate of the finishing mill, the parameters of the automatic opening of the entry side guide plate of the finishing mill are set, and the parameters of the roll gap of the finishing mill are set.

[0010] Further, by adjusting the roll gap of the roughing mill, the distance between the head and tail of the intermediate billet in the roughing mill deviating from the rolling center line is adjusted.

[0011] Further, the distance between the head and tail of the intermediate billet in the roughing mill deviating from the rolling center line is preferably ≤60mm.

[0012] Further, the setting of the short stroke value of the tail of the entry side guide plate of the finishing mill includes:

[0013] The short stroke of the entry side guide plate of each of the finishing mills F2, F3, F4, F5, F6 and F7 is set separately for the head, middle and tail.

[0014] Further, the short stroke of the entry side guide plate of the same finishing mill is set to the same value.

[0015] Further, when rolling the tail of the thin gauge high strength steel, the short stroke value is increased by 20-40 mm based on the set short stroke value of the tail of the entry side guide plate of the finishing mill.

[0016] Further, the parameters of the automatic opening of the entry side guide plate of the finishing mill are set, preferably the parameters of the automatic opening of the entry side guide plate of the finishing mills F5, F6 and F7 are set.

[0017] Further, the setting of the parameters of the automatic opening of the entry side guide plate of the finishing mills F5, F6 and F7 includes:

[0018] When the tail of the strip steel leaves F4, the F5 entry side guide plate continues to open, and when the tail leaves F5, the cumulative opening of the F5 entry side guide plate is ≤30mm;

[0019] When the tail of the strip steel leaves F5, the F6 entry side guide plate continues to open, and when the tail leaves F6, the cumulative opening of the F6 entry side guide plate is ≤30mm;

[0020] When the tail of the strip steel leaves F6, the F7 entry side guide plate continues to open, and when the tail leaves F7, the cumulative opening of the F7 entry side guide plate is ≤40mm.

[0021] Further, the parameters of the finishing mill roll gap are set, preferably, the parameters of the F6, F7 finishing mill roll gap are set.

[0022] Further, the parameters of the F6, F7 finishing mill roll gap are set, preferably, the parameters of the F6, F7 finishing mill roll gap are set.

[0023] When the tail of the strip leaves F4, the F6-F7 roll gap starts to slowly linearly lift, the cumulative lift of F6 is ≤0.5mm, and the cumulative lift of F7 is ≤0.8mm.

[0024] The technical effects and advantages of the present application are as follows:

[0025] Thin gauge high strength steel has the characteristics of heavy rolling load and fast rolling speed in the production process. When the tail of the strip is rolled, the rolling load is further increased due to the decrease of temperature, which aggravates the instability of the production process, causes the strip to frequently occur rolling and affects the surface quality of the strip and the continuity of production, thereby restricting the improvement of the production line efficiency. The present application provides an efficient and stable thin gauge high strength steel tail quality control method without increasing investment. The main reason for the rolling of thin gauge high strength steel in the finishing mill is that the temperature of the tail of the strip is low, the equivalent resistance is large, the shape adjustment precision is high, and the difficulty is great. When the adjustment is not timely or the adjustment precision is insufficient, the strip deviation is aggravated, the local folding is formed at the side guide plate, and under the action of folding, the rolling pressure on both sides is greatly different, thereby causing uneven deformation and leading to local rolling. By controlling the rough rolling shape, the rolling stability of the finishing mill is effectively improved, and the shape adjustment amount is reduced; by adjusting the opening degree of the finishing mill side guide plate, the local folding phenomenon caused by the deviation of the strip is effectively avoided; by controlling the roll gap of the last stand with a special mode, the unevenness of the rolling rate on both sides caused by local folding is effectively solved. Through the implementation of the present application, the local folding, one-sided tail throwing and rolling caused by the inconsistency of the extension of the strip on both sides due to temperature, rolling pressure, abnormal plate shape adjustment and the like in the actual production process are solved, and the production efficiency is improved.

[0026] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application can be realized and attained by the structure particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A flow chart of the thin gauge high strength steel tail quality control method of the present application is shown;

[0028] Figure 2 A single value control chart of the number of tail rolling from June 2020 to June 2021 according to the implementation is shown. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0030] To solve the problems in the prior art, the present application discloses a control method for improving tail quality of thin-gauge high-strength steel, which comprises the following steps: calibrating parameters of rough rolling mill and finishing rolling mill; adjusting the distance between the head and tail of the intermediate billet and the rolling center line in the rough rolling mill; based on the calibrated rolling mill parameters, when the rolling thickness is less than or equal to 3.0 mm and the tensile strength is greater than or equal to 400 MPa, increasing the short stroke value on the basis of the set short stroke value of the tail of the entry side guide plate of the finishing rolling mill, setting the short stroke value of the tail of the entry side guide plate of the finishing rolling mill, setting the parameters of the automatic opening of the entry side guide plate of the finishing rolling mill and setting the parameters of the roll gap of the finishing rolling mill, so as to improve the tail quality of the thin-gauge high-strength steel.

[0031] Further, the plate shape has strong heredity in the continuous rolling production process, and when the intermediate billet deviates from the center line more in the rough rolling, the deviation will be aggravated under the action of the reduction rate in the finishing rolling process, so it is necessary to control the distance between the head and tail of the intermediate billet and the rolling center line. In the production process, the distance between the head and tail of the intermediate billet and the rolling center line is controlled by adjusting the roll gap of the rough rolling mill, preferably, when the thin-gauge high-strength steel is rolled, the distance between the head and tail of the intermediate billet and the rolling center line is ensured to be less than or equal to 60 mm by timely adjusting the roll gap inclination.

[0032] Further, the tail opening degree value of the entry side guide plate of the finishing rolling mill is set, specifically, the short stroke of the entry side guide plate of the finishing rolling mill F2, F3, F4, F5, F6 and F7 is set separately for the head, the middle and the tail, and to ensure the rolling stability, the short stroke of the entry side guide plate head, middle and tail of the same finishing rolling mill is set to the same value. When the thin-gauge high-strength steel is rolled, the load is heavy when the tail is rolled due to the reduction of tension and temperature, the plate shape change is not easy to control, the deviation is aggravated, especially when the speed of the rear rack is fast and the plate shape changes rapidly, therefore, the opening degree of the F2, F3, F4, F5, F6 and F7 side guide plate is increased by 20-40 mm on the basis of the setting of the head and the middle, and the short stroke of the head and the middle of the side guide plate of the finishing rolling mill F2, F3, F4, F5, F6 and F7 is set in sequence, as shown in Table 1:

[0033] Table 1: Setting of the tail short stroke of the F2-F7 side guide plate when the tail is rolled

[0034]

[0035] As shown in Table 1, when rolling the tail section of thin-gauge high-strength steel, the short stroke value is increased by 20-40mm based on the previously set short stroke value for the tail section of the finishing mill inlet side guide plate. Specifically, the short stroke of the head and middle side guide plates of F2 is set to 40mm, the short stroke of the head and middle side guide plates of F3 is set to 50mm, the short stroke of the head and middle side guide plates of F4 is set to 60mm, the short stroke of the head and middle side guide plates of F5 is set to 70mm, the short stroke of the head and middle side guide plates of F6 is set to 80mm, and the short stroke of the head and middle side guide plates of F7 is set to 90mm.

[0036] Furthermore, during the rolling tail section, when thin-gauge high-strength steel deviates from its designated path, it will collide with the side guide plate, causing localized folding. This can lead to localized crushing after the rolls bite the steel, especially on the downstream stands where the strip thickness is thin and the rolling speed is high, resulting in a higher frequency of occurrence. Therefore, it is necessary to set control logic for the tail side guide plate, i.e., to set parameters for the automatic opening of the finishing mill inlet side guide plate. Preferably, parameters are set for the automatic opening of the F5, F6, and F7 finishing mill inlet side guide plates, so that the downstream stand side guide plates automatically open during the rolling tail section. Depending on the stand, the maximum opening distance is ≤40mm.

[0037] When rolling thin-gauge high-strength steel, when the tail of the strip leaves F4, the F5 inlet side guide plate remains open, and the cumulative opening of the F5 inlet side guide plate is ≤30mm when the tail leaves F5; when the tail of the strip leaves F5, the F6 inlet side guide plate remains open, and the cumulative opening of the F6 inlet side guide plate is ≤30mm when the tail leaves F6; when the tail of the strip leaves F6, the F7 inlet side guide plate remains open, and the cumulative opening of the F7 inlet side guide plate is ≤40mm when the tail leaves F7.

[0038] Furthermore, when the strip deviates, it will form local folds. Under the same roll gap action, the folded part will have a larger reduction, and the metal will undergo uneven deformation, resulting in rolling damage. This can be optimized by setting the parameters of the finishing mill roll gap. Preferably, the parameters of the finishing mill roll gaps F6 and F7 are set so that when the tail of the strip leaves F4, the F6-F7 roll gap begins to slowly and linearly rise, with the cumulative rise of F6 ≤ 0.5 mm and the cumulative rise of F7 ≤ 0.8 mm.

[0039] The technical solution of the present invention will be further described in conjunction with specific embodiments.

[0040] according to Figure 1 The process shown controls the distance between the head and tail of the intermediate billet and the rolling center line. During the production process, the distance between the roughing mill intermediate billet and the rolling center line is controlled by adjusting the roll gap. When rolling thin-gauge high-strength steel, the distance between the head and tail of the intermediate billet and the rolling center line is ≤60mm by timely adjustment of the roll gap inclination.

[0041] When rolling thin gauge high-strength steel, the short stroke of the entry side guide plate of the finishing mill F2, F3, F4, F5, F6 and F7 is set to be gradually increased for the head, middle and tail part respectively, and the short stroke of the entry side guide plate of the same finishing mill is set to be the same value; when rolling the tail part, the opening degree of the side guide plate of F2, F3, F4, F5, F6 and F7 is increased by 20-40mm based on the setting of the head and middle part;

[0042] When rolling the tail part, the parameters of the automatic opening of the entry side guide plate of the downstream finishing mill are set, preferably, the parameters of the automatic opening of the entry side guide plate of F5, F6 and F7 are set, and the maximum opening distance is ≤40mm according to different racks;

[0043] For the optimized parameters of the roll gap of the finishing mill, the roll gap of F6 / F7 is automatically opened according to the position of the strip when rolling the tail part; the optimized parameters of the roll gap of the finishing mill are preferably that the parameters of the roll gap of F6, F7 are set, and when the tail part of the strip leaves F4, the roll gap of F6-F7 starts to slowly linearly lift, the cumulative lifting of F6 is ≤0.5mm, and the cumulative lifting of F7 is ≤0.8mm.

[0044] According to the above method, the tail part quality control is carried out in Xichang Steel Vanadium hot rolling line since January 2021, the deviation of the head and tail of the intermediate billet from the center line in the rough rolling and the setting of the side guide plate of the finishing mill F2-F7 are included in the post operation procedure, the control logic of the tail part side guide plate and the control logic of the roll gap are optimized and directly solidified through the first level automation to realize automatic control. Figure 2 The single value control chart of the number of tail part rolling breakage from June 2020 to June 2021 is shown according to the implementation condition Figure 2 It can be seen that through the collection of the rolling breakage data from June 2020 to June 2021 by the production report system, the number of tail part rolling breakage is obviously reduced after the implementation of the method. Due to the production characteristics of the conventional hot rolling line, the rolling breakage cannot be completely eliminated, but the effect is significantly improved through the implementation. The average number of tail part rolling breakage before the implementation is 13.71 times per month, and the average number of tail part rolling breakage after the implementation is 8.5 times per month.

[0045] Finally, it should be noted that: the above only describes the preferred embodiments of the present application and is not used to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced by equivalents, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A control method for improving tail quality of a thin gauge high strength steel, characterized by, The method comprises, Calibrating parameters of the roughing mill and the finishing mill: adjusting the distance between the head and tail of the intermediate billet in the roughing mill and the rolling center line to be less than or equal to 60 mm, and setting the short stroke value of the tail of the entry side guide plate of the finishing mill; wherein the setting of the short stroke value of the tail of the entry side guide plate of the finishing mill comprises: setting the short stroke of the entry side guide plate of each finishing mill F2, F3, F4, F5, F6 and F7 for the head, the middle and the tail separately; the short strokes of the head, the middle and the tail of the entry side guide plate of the same finishing mill are set to the same value; the short strokes of the head and the middle of the side guide plate of the finishing mills F2, F3, F4, F5, F6 and F7 are set in sequence in an increasing manner; Based on the calibrated rolling mill parameters, when rolling the tail of the thin gauge high strength steel, the short stroke value of the tail of the entry side guide plate of the finishing mill is increased by 20-40 mm based on the setting of the short stroke value of the tail of the entry side guide plate of the finishing mill, the parameters of the automatic opening of the entry side guide plate of the finishing mill are set, and the parameters of the roll gap of the finishing mill are set; wherein The setting of the parameters of the automatic opening of the entry side guide plate of the finishing mill comprises setting the parameters of the automatic opening of the entry side guide plate of the finishing mills F5, F6 and F7; The setting of the parameters of the automatic opening of the entry side guide plate of the finishing mill F5, F6 and F7 comprises: When the tail of the strip leaves F4, the entry side guide plate of F5 is continuously opened, and when the tail leaves F5, the cumulative opening of the entry side guide plate of F5 is less than or equal to 30 mm; When the tail of the strip leaves F5, the entry side guide plate of F6 is continuously opened, and when the tail leaves F6, the cumulative opening of the entry side guide plate of F6 is less than or equal to 30 mm; When the tail of the strip leaves F6, the entry side guide plate of F7 is continuously opened, and when the tail leaves F7, the cumulative opening of the entry side guide plate of F7 is less than or equal to 40 mm; The setting of the parameters of the roll gap of the finishing mill F6 and F7 comprises: When the tail of the strip leaves F4, the roll gap of F6-F7 starts to slowly linearly lift, the cumulative lifting of F6 is less than or equal to 0.5 mm, and the cumulative lifting of F7 is less than or equal to 0.8 mm. The distance between the head and tail of the intermediate billet in the roughing mill and the rolling center line is adjusted by adjusting the roll gap of the roughing mill.

2. The control method for improving tail end quality of thin gauge high strength steel according to claim 1, characterized in that, ​

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