Acid pickling method for thick-specification high-strength hot-rolled steel plate

Abstract

The invention discloses an acid pickling method for a thick-specification high-strength hot-rolled steel plate. The problems that an existing hot-rolled steel plate with the thickness being 7-10 mm, the width being 900-1400 mm and the tensile strength being 1000-1200 MPa is low in acid pickling efficiency and poor in acid pickling quality are mainly solved. According to the technical scheme, the pickling method for the thick-specification high-strength hot-rolled steel plate comprises the steps that (1) a hot-rolled steel coil is subjected to uncoiling pretreatment, a hot-rolled steel coil head is leveled, and the hot-rolled steel coil head is reversely bent step by step in a segmented mode through a bending roller arranged at an inlet preparation station of a pickling unit; 2) uncoiling a hot rolled steel coil; 3) pickling the hot-rolled steel plate; (4) coiling: the hot-rolled steel plate subjected to acid pickling is subjected to rinsing, hot air drying and oiling, and then coiling is performed; and when the strip tail is drifted, the anti-wrinkling roller automatically presses down to reduce the bending degree of the strip tail, so that the strip is prevented from being extruded and broken in the straightening machine. According to the method, the hot-rolled steel plate does not need to be annealed and softened before pickling, and the pickling cost of the thick-specification high-strength hot-rolled steel plate is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to a pickling method of hot-rolled steel plate, in particular to a pickling method of thick-gauge high-strength hot-rolled steel plate; specifically, to a pickling method of hot-rolled steel plate with a thickness of 7-10 mm, a width of 900-1400 mm, and a tensile strength of 1000-1200 MPa, belonging to the technical field of pickling of hot-rolled steel plate. BACKGROUND

[0002] Steel plates with a carbon content greater than 0.4% cannot be produced on a continuous pickling production line due to welding problems, and high-strength steel with a thickness greater than 6 mm or high alloy content and a yield strength greater than 600 MPa is also not suitable for production on a continuous pickling production line because it is difficult to weld through or the weld is prone to porosity.

[0003] Push-pull type pickling production lines are more suitable for high-carbon high-alloy, high-strength, and high-thickness hot-rolled steel plates because they are not limited by welding. High-strength and high-thickness hot-rolled steel plates are prone to loose coiling during pickling because of high internal stress, so interlayer misalignment is inevitable, which can cause surface scratches and affect surface quality. In addition, high-strength steel is difficult to flatten due to the large curvature of the inner circle of the hot-rolled coil during tail flinging, so the tail is prone to extrusion between the straightening rollers when passing through the straightening machine, affecting the production rhythm. Furthermore, high-strength and high-thickness pickled steel plates are prone to layering errors and edge overflow during coiling due to difficulty in centering, so pickling of high-strength and high-thickness hot-rolled steel plates has always been a difficult technical problem in the pickling field.

[0004] Chinese patent with application publication number CN115228933A discloses a production method for hot-rolled pickled high-strength steel with a thickness of 6 mm or more, which discloses a method for ensuring threading by controlling the uncoiling tension and setting the nine-roll straightening pressure, and controlling the coiling tension to achieve hot-rolled steel coils with a thickness of 6-12 mm and a yield strength of 300-600 MPa. This method is suitable for steel coils with lower strength and is not suitable for high-strength steel with a yield strength exceeding 600 MPa.

[0005] Chinese patent with application publication number CN116393530A discloses a control method for threading of thick-gauge steel strips with a thickness of 8 mm or more, which discloses a method of gradually uncoiling no more than 1 / 4 turn at a time by manual control, in which the guide plate is lifted from 45° to 50°, maintained for 10-20 s, and then restored. In fact, this method is a plastic deformation of the steel plate, and it is not suitable for high-strength steel.

[0006] The Chinese patent with the application publication number CN116020899 A discloses a control method for thick-gauge pickling steel coiling mislayering, and discloses that the smooth coiling of a steel coil with a thickness of more than 8 mm and a tensile strength of more than 500 MPa is realized by optimizing the coiling tension setting. However, according to the setting formula of the coiling tension in the disclosure, the coiling tension will be more than 300 KN when the thickness of the steel plate reaches 8 mm, the width reaches 1000 mm, and the tensile strength reaches 1000 MPa, which is basically impossible to realize by a conventional coiling machine.

[0007] The existing 7-10 mm thick, 1000-1200 MPa tensile strength hot-rolled steel plate uses the method of first annealing to reduce the internal stress and strength of the steel plate, and then uncoiling and pickling, which has the problems of high production cost, great difficulty in pickling, and low pickling efficiency. SUMMARY

[0008] The purpose of the present application is to provide a pickling method for thick-gauge high-strength hot-rolled steel plates, mainly solving the problems of low pickling efficiency and poor pickling quality of the existing 7-10 mm thick, 900-1400 mm wide, 1000-1200 MPa tensile strength hot-rolled steel plates.

[0009] The method of the present application completely solves the quality problems of the 7-10 mm thick, 900-1400 mm wide, 1000-1200 MPa tensile strength hot-rolled steel plates during pickling, such as uncoiling and uncoiling, tailing and breaking, and coiling mislayering.

[0010] The technical idea of the present application is to use a bending roller with segmented pressure heads to assist uncoiling, and after uncoiling and cutting off the unqualified parts by a cross-cutting shear, the steel coil enters the uncoiler, and the uncoiling is assisted by the pressure of the anti-wrinkle roller to realize the entry of the strip head into the entrance straightener. After the strip steel passes through the straightener smoothly and is pickled, the tension setting is optimized during coiling to avoid coiling mislayering and overflowing edges, and the anti-wrinkle roller automatic feeding function is developed during tailing to reduce the bending degree of the tail and avoid extrusion and breaking in the straightener.

[0011] The technical solution of the present application is a pickling method for thick-gauge high-strength hot-rolled steel plates, the thickness of the hot-rolled steel plate is 7-10 mm, the width is 900-1400 mm, the yield strength is 600-900 MPa, and the tensile strength is 1000-1200 MPa, comprising the following steps:

[0012] 1) Hot-rolled steel coil uncoiling pretreatment, the strip head of the hot-rolled steel coil is flattened, and the strip head is gradually bent in reverse by the bending rollers arranged at the entrance preparation station of the pickling unit; after the strip head of the hot-rolled steel coil is straightened, the unqualified part of the strip head is cut off by a cross-cutting shear; and then the hot-rolled steel coil is wound;

[0013] 2) hot-rolled steel coil uncoiling, uncoiling the hot-rolled steel coil with an uncoiler, pressing down the hot-rolled steel coil head with a wrinkle prevention roller, and sending the hot-rolled steel coil head into an entry straightening machine; the hot-rolled steel plate after uncoiling is sent into an acid pickling unit;

[0014] 3) hot-rolled steel plate pickling, pickling the hot-rolled steel plate with a push-pull type pickling unit, and the length of the pickling tank is 30-60m;

[0015] 4) coiling, after the hot-rolled steel plate after pickling is rinsed, hot air dried, and oiled, the hot-rolled steel plate is coiled; the tensile strength of the hot-rolled steel plate is <1100MPa, the unit coiling tension of the hot-rolled steel plate is 1.90-1.56kg / mm 2 , the total coiling tension of the hot-rolled steel plate is 152-204KN; the tensile strength of the hot-rolled steel plate is ≥1100MPa, the unit coiling tension of the hot-rolled steel plate is 2.28-1.77kg / mm 2 , and the total coiling tension of the hot-rolled steel plate is 146-202KN; when the tail of the strip is thrown, the tail is automatically pressed down through the wrinkle prevention roller, and the degree of bending of the tail is reduced by controlling the pressing amount and pressing force of the wrinkle prevention roller.

[0016] Further, in step 1), the thickness of the hot-rolled steel plate is 7.0-8.0mm, the segmented length of the hot-rolled steel coil head bent reversely by the bending roller is 180-200mm; the thickness of the hot-rolled steel plate is 8.1-9.0mm, the segmented length of the hot-rolled steel coil head bent reversely by the bending roller is 160-180mm; the thickness of the hot-rolled steel plate is 9.1-10.0mm, and the segmented length of the hot-rolled steel coil head bent reversely by the bending roller is 150-160mm; the effect is good.

[0017] Further, in step 1), the diameter of the bending roller is Φ200mm.

[0018] Further, in step 4), the pressing amount of the wrinkle prevention roller is 70-75mm; and the pressing force of the wrinkle prevention roller is 0.3-0.4MPa.

[0019] The reasons for adopting the production process are as follows:

[0020] 1, the setting of the segmented length of the hot-rolled steel coil head bent reversely by the bending roller in the uncoiling pretreatment process

[0021] Because the internal stress of the hot-rolled coil with high strength and high thickness is large, the strip steel after uncoiling still presents the original bending state, and after being flattened by the conventional straightening machine, the strip steel is still better than the rebound and will restore the original bending state, which affects the subsequent normal production. In the application, a set of bending rollers with a diameter of Φ200mm are arranged at the entry preparation station of the pickling unit, and the segmented length is adjusted to 150-200mm according to the thickness interval to gradually segment and bend reversely, so as to realize the flattening of the head of the strip steel and prevent the coil from loosening.

[0022] The strip thickness is 7.0-8.0mm, and the segment length of the head of the hot-rolled steel coil strip bent by the reverse bending roll is 180-200mm.

[0023] The strip thickness is 8.1-9.0mm, and the segment length of the head of the hot-rolled steel coil strip bent by the reverse bending roll is 160-180mm.

[0024] The strip thickness is 9.1-10.0mm, and the segment length of the head of the hot-rolled steel coil strip bent by the reverse bending roll is 150-160mm.

[0025] 2, strip tail anti-wrinkle roll reduction and reduction pressure setting

[0026] When the strip tail is thrown, the inner stress of the inner circle of the hot-rolled coil is larger due to smaller curvature, so the tail of the strip tail thrown away from the uncoiler drum still maintains the original bending state, and the strip tail is easily folded and pressed to be broken when entering the entry pinch roll of the straightening machine along the guide plate. The anti-wrinkle roll reduction is set to 70-75mm, and the anti-wrinkle roll reduction pressure is 0.3-0.4MPa, so that the pressing and breaking of the high-strength steel strip tail in the straightening machine can be avoided.

[0027] 3, coiling tension control setting

[0028] For high-strength steel, the strength, thickness and width of the steel grade need to be considered to set the unit tension. Generally speaking, the higher the strength of the strip, the larger the width and thickness, the larger the required unit tension. However, the tension of the current coiler generally does not exceed 200KN. For thick high-strength steel, the requirement of the steel coil circumferential deformation on the tension during coiling deformation also needs to be considered. If the tension is too large, it may be pulled off, and if it is too small, the coil shape will be poor. Through research, it is found that the coiling tension can be automatically controlled by the model according to the following rules to avoid problems such as coiling layering and overflow edge. The present application sets that the tensile strength of the hot-rolled steel plate is <1100MPa, the unit coiling tension of the hot-rolled steel plate is 1.90-1.56kg / mm 2 , and the total coiling tension of the hot-rolled steel plate is 152-204KN; the tensile strength of the hot-rolled steel plate is ≥1100MPa, the unit coiling tension of the hot-rolled steel plate is 2.28-1.77kg / mm 2 , and the total coiling tension of the hot-rolled steel plate is 146-202KN.

[0029] The method realizes the automatic control of the thick high-strength hot-rolled steel coil in the push-pull type pickling production line, and solves the efficiency problem of manual control during uncoiling.

[0030] Compared with the prior art, the present application has the following positive effects: 1. The method realizes smooth unwinding, pickling and coiling of the thick-gauge high-strength hot-rolled steel plate on the push-pull type pickling production line, and is automatically controlled, efficient and reliable throughout; the push-pull type pickling unit realizes efficient, high-quality and low-cost pickling of the hot-rolled steel plate with a yield strength of 600-900 MPa, a tensile strength of 1000-1200 MPa, an elongation after fracture of 10%-20%, a thickness of 7.0-10.0 mm and a width of 900-1400 mm. 2. The method does not need to anneal and soften the hot-rolled steel plate before pickling, thereby reducing the pickling cost of the thick-gauge high-strength hot-rolled steel plate. 3. The method improves the production efficiency and quality of the thick-gauge high-strength hot-rolled steel plate, and solves the quality problems of the hot-rolled steel plate with a thickness of 7-10 mm and a tensile strength of 1000-1200 MPa, such as easy unwinding and loose coiling, easy breakage during tail swinging, and easy layering error during coiling. DETAILED DESCRIPTION

[0031] The present application is further described below in combination with Examples 1-4, as shown in Tables 1-5.

[0032] Table 1 is the grade and specification of the steel in the examples of the present application, and Table 2 is the mechanical properties of the steel in the examples of the present application.

[0033] Table 1 is the size parameter of the steel plate in the examples of the present application.

[0034] Element Grade Thickness / mm Width / mm Cross-sectional area / mm 2 ]] Invention 7-10 900-1400 6300-14000 Example 1 42CrMo4 9.0 1350 12150 Example 2 Sk85 7.0 1250 8750 Example 3 51CrV4 8.2 1200 9840 Example 4 51CrV4 8.5 1200 10200

[0035] Table 2 is the mechanical properties of the hot-rolled steel plate in the examples of the present application.

[0036]

[0037] The hot-rolled coil is unwound by using the bending roller in the pickling unit entrance preparation station, and the unwound hot-rolled coil is pressed by the upper pressing plate and roller to ensure that the head of the hot-rolled coil enters the cross-cut smoothly; after cutting off the unqualified part, the hot-rolled coil is coiled.

[0038] The hot-rolled coil is unwound by using the unwinding machine, and the head of the hot-rolled coil is pressed by the anti-wrinkle roller to avoid loose coiling; the head of the hot-rolled coil is sent to the entrance straightening machine, and the unwound hot-rolled plate is sent to the pickling unit.

[0039] After the hot-rolled coil is unwound, it is pickled, rinsed, dried, oiled and coiled to obtain the finished hot-rolled pickled steel plate; the coiling tension is established in advance to avoid problems such as layering error and overflow edge during coiling, and the anti-wrinkle roller is automatically used during tail swinging to reduce the bending degree of the tail.

[0040] The parameters of the unwinding bending roller are shown in Table 3, the control parameters of the anti-wrinkle roller used during tail swinging are shown in Table 4, and the coiling tension control parameters are shown in Table 5.

[0041] Table 3: Segmented length of the head of the hot rolled steel coil with reverse bending of the bending roll according to the inventive example

[0042] Category Segment length of reverse bend hot-rolled steel coil strip head / mm Invention 150-200 Example 1 155 Example 2 195 Example 3 165 Example 4 170

[0043] Table 4: Reduction and reduction force parameters of the anti-bending roll according to the inventive example

[0044]

[0045]

[0046] Table 5: Unit coiling tension and total coiling tension parameters of the hot rolled steel sheet according to the inventive example

[0047]

[0048] In addition to the above-mentioned embodiments, the present application can also have other implementation manners. Any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present application.

Claims

1. A pickling method for a thick-gauge high-strength hot-rolled steel sheet having a thickness of 7 to 10 mm, a width of 900 to 1400 mm, a yield strength of 600 to 900 MPa, and a tensile strength of 1000 to 1200 MPa, characterized by, The method comprises the following steps: 1) hot-rolled steel coil uncoiling pretreatment, straightening the head of the hot-rolled steel coil, gradually bending the head of the hot-rolled steel coil in sections in reverse through the bending rollers arranged in the entrance preparation station of the pickling unit; after the head of the hot-rolled steel coil is straightened, the unqualified part of the head of the hot-rolled steel coil is cut off by a cross shear; then the hot-rolled steel coil is wound; 2) hot-rolled steel coil uncoiling, the hot-rolled steel coil is uncoiled by an uncoiler, the head of the hot-rolled steel coil is pressed down by an anti-wrinkle roller, and the head of the hot-rolled steel coil is sent to an entrance straightening machine; after uncoiling, the hot-rolled steel plate is sent to a pickling unit; 3) pickling the hot-rolled steel plate, the hot-rolled steel plate is pickled by a push-pull type pickling unit, and the length of the pickling tank is 30-60 m; 4) coiling, the hot-rolled steel plate after pickling is rinsed, dried by hot air drying, oiled and coiled; the tensile strength of the hot-rolled steel plate is <1100MPa, the unit coiling tension of the hot-rolled steel plate is 1.90-1.56kg / mm 2 , the total coiling tension of the hot-rolled steel plate is 152-204KN; the tensile strength of the hot-rolled steel plate is ≥1100MPa, the unit coiling tension of the hot-rolled steel plate is 2.28-1.77kg / mm 2 , the total coiling tension of the hot-rolled steel plate is 146-202KN; when the strip tail is thrown, the strip tail is automatically pressed by the anti-wrinkle roller, and the degree of bending of the strip tail is reduced by controlling the amount of pressing and the pressing force of the anti-wrinkle roller.

2. The pickling method of a thick-gauge high-strength hot-rolled steel sheet according to claim 1, characterized by, In step 1), the thickness of the hot-rolled steel plate is 7.0-8.0 mm, the segmented length of the head of the hot-rolled steel coil bent in reverse by the bending rollers is 180-200 mm; the thickness of the hot-rolled steel plate is 8.1-9.0 mm, the segmented length of the head of the hot-rolled steel coil bent in reverse by the bending rollers is 160-180 mm; the thickness of the hot-rolled steel plate is 9.1-10.0 mm, and the segmented length of the head of the hot-rolled steel coil bent in reverse by the bending rollers is 150-160 mm.

3. The pickling method of a thick-gauge high-strength hot-rolled steel sheet according to claim 1, characterized by, In step 1), the diameter of the bending roller is Φ200 mm.

4. The pickling method of a thick-gauge high-strength hot-rolled steel sheet according to claim 1, characterized by, In step 4), the pressing-down amount of the anti-wrinkle roller is 70-75 mm, and the pressing-down pressure of the anti-wrinkle roller is 0.3-0.4 MPa.

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