Rod and wire rolling method for eliminating steel billet corner defects and rolling mill rack

Abstract

The invention belongs to the technical field of wire rolling, and particularly discloses a rod and wire rolling method for eliminating steel billet corner defects and a rolling mill stand. The method comprises the following steps that firstly, a heated steel billet is conveyed to a steel rotating device; then the steel billet enters a steel rotating roller way under the action of a guide and guard guide plate, the steel billet is rotated by 45 degrees through a steel rotating device, and the corner of the steel billet is aligned with a groove hole in a roller; then the steel billet is conveyed to a rolling mill through a conveying roller way and a V-shaped anti-torsion guide roller; and finally, the steel billet is rolled into a steel bar through seven passes of rough rolling, wherein large deformation is adopted in the first pass. In order to solve the problem of residual crack defects in billet corner rolling, a pass system is optimized, and the mode that upper and lower flat rollers and left and right vertical rollers are used for simultaneous pressing-down rolling in four directions is adopted, so that the problems that in the continuous casting process, due to the fact that the billet corner cooling speed is higher than that of other parts, shrinkage is uneven, and tensile stress is generated on the surface are solved; therefore, cracks are generated at the corners of the steel billets, and the product quality is influenced.

Description

Technical Field

[0001] The present invention relates to the technical field of wire rod rolling, and particularly relates to a bar and wire rod rolling method and a rolling mill stand for eliminating corner defects of steel billets. Background Art

[0002] In the production process of bar and wire rods in the iron and steel industry, corner defects of steel billets have always been one of the key problems restricting product quality. Such defects are mainly manifested as corner microcracks, stress concentration, and folding defects generated during subsequent rolling processes, seriously affecting the surface quality, mechanical properties, and service life of products. Especially in the production of high-value-added products such as special steel, the existence of corner defects directly leads to a decrease in product qualification rate, an increase in production costs, and even affects the performance requirements of the end application field. Therefore, how to effectively eliminate corner defects of steel billets has become a technical problem that iron and steel enterprises urgently need to solve.

[0003] The formation of corner defects of steel billets is closely related to continuous casting and rolling processes. During continuous casting, the cross-section of the corner of the square billet is sharp, and its cooling rate is significantly faster than other parts. Due to uneven cooling, large tensile stresses will be generated in the corner area during solidification shrinkage; when the tensile stress exceeds the tensile strength of the material, microcracks will form on the corner surface. These microcracks not only cannot heal during subsequent rolling processes, but will further expand due to the severe deformation of the metal, and even cause stress concentration. In traditional rolling processes, the pass design in the rough rolling stage often cannot effectively improve the corner state. For example, when using a 6-pass rolling pass system of flat box - box - oval - round - oval - round, the rolling in the first two passes (flat box and box) only reduces the width surface of the rolled piece, and almost no plastic deformation occurs in the corner metal. This design results in the corner sharp points always protruding, and defects such as microcracks in the corners of the steel billets cannot be welded by rolling. Instead, they deteriorate further under the action of tensile stresses generated by spread deformation. In addition, the flow path of corner metal during rolling is complex, and local stress concentration is prone to cause folding defects, ultimately resulting in defects such as cracks and pits on the surface of the finished product, seriously affecting the fatigue resistance and processing performance of the product.

[0004] The elimination of corner defects of steel billets is the core link to improve the quality of bar and wire rod products. Therefore, to solve the above problems, it is necessary to design a bar and wire rod rolling method for eliminating corner defects of steel billets. By redesigning the rough rolling pass system, it is possible to solve the problem that during continuous casting, due to the faster cooling rate of the corners of the steel billets than other parts, uneven shrinkage generates tensile stresses on the surface, resulting in cracks in the corners of the steel billets and affecting product quality. Summary of the Invention

[0005] The object of the present invention is to provide a bar and wire rolling method for eliminating corner defects of billets, so as to solve the problem that during the continuous casting process, due to the faster cooling rate of the billet corners than other parts, uneven shrinkage occurs, resulting in tensile stress on the surface, which causes cracks at the billet corners and affects the product quality.

[0006] To achieve the above object, the basic solution provided by the present invention is: a bar and wire rolling method for eliminating corner defects of billets, including the following steps: S1: Steel billet rotation: First, the heated billet is transported to the steel billet rotation device through the furnace exit roller table, and then under the action of the guard plate, the billet enters the steel billet rotation roller table. The billet is rotated 45° by the upper and lower torsion rollers, so that the corners of the billet are aligned with the groove holes of the upper rollers of the rolling mill. Then, the billet is transported to the rolling mill through the transport roller table and the V-shaped anti-torsion guide rollers; S2: Rough rolling: Then, the billet with a size of 150mm*150mm is rolled into steel bars through 7 passes of rough rolling. The deformation coefficient of the first pass > 1.2, the deformation coefficient of the second pass is 1.15 - 1.20, and the deformation coefficient of the third to seventh passes is 1.3 - 1.4.

[0007] The beneficial effects of the present invention are as follows: (1) The present invention adopts a pass system of 7 passes of rough rolling of regular octahedron - elliptical square - circular - elliptical - circular - elliptical - circular. In the first pass, high deformation is applied to the four corners of the billet simultaneously through the regular octahedron pass, forcing the corner metal to be pressed down, welding microcracks, and rolling the sharp corners into smooth arcs, eliminating the protrusions at the billet corners, thereby eliminating the stress concentration source and avoiding corner defects caused by stress concentration; (2) The rolling mill uses the cooperation of upper and lower flat rollers and left and right vertical rollers to roll the billet in multiple directions, so that the billet is evenly pressured during the rolling process, dispersing the rolling force to the whole rolled piece, and thus avoiding local stress concentration at the billet corners and reducing folding defects; (3) Through the conical steel billet rotation roller table and V-shaped anti-torsion guide rollers of the steel billet rotation device, the billet is accurately guided into the rolling mill, so that the four corners of the billet are completely aligned with the groove holes of the rollers, avoiding uneven deformation caused by angle deviation, and improving the rolling stability and finished product qualification rate.

[0008] Solution two, this is the optimization of the basic solution. In S1, the temperature of the billet during rough rolling is 1020°C - 1060°C; an appropriate rolling temperature can improve the plasticity of the billet, reduce the deformation resistance, and thus reduce the rolling force requirement and protect the life of the rollers.

[0009] Solution 3, which is the optimization of the basic solution. In S2, the rolling passes from the 1st pass to the 7th pass during rough rolling are in sequence an octahedron shape, an oval-square shape, a circular shape, an elliptical shape, a circular shape, an elliptical shape, and a circular shape. The steel billet is rolled into a regular octagon with a side length of 70 mm in the 1st pass. Using an octahedron pass in the 1st pass can evenly distribute the corner deformation to eliminate the edges and corners of the steel billet. At the same time, it provides a regular cross-section for subsequent pass matching, improving the rolling stability. The passes from the 2nd pass to the 7th pass are gradually transitioned to disperse the deformation stress and avoid the formation of cracks due to repeated stress on the corners.

[0010] Solution 4, which is the optimization of the basic solution. In S2, the roll gap value of the 1st pass is 15 mm, the roll gap value of the 2nd pass is 18 mm, and the roll gap values of the 3rd pass to the 7th pass are all 15 mm. Using a smaller roll gap value in the first pass in combination with a high deformation coefficient can force the corner material to fill the roll groove to eliminate initial defects. Increasing the roll gap value in the 2nd pass can relieve the material flow resistance and prevent surface tearing. The roll gap values of the 3rd pass to the 7th pass are unified, maintaining the rolling stability and ensuring the dimensional accuracy of the rolled piece.

[0011] Solution 5, which is the optimization of the basic solution. In S2, the deformation coefficient of the 1st pass is 1.209, the deformation coefficient of the 2nd pass is 1.18, the deformation coefficient of the 3rd pass is 1.35, the deformation coefficient of the 4th pass is 1.37, the deformation coefficient of the 5th pass is 1.357, the deformation coefficient of the 6th pass is 1.375, and the deformation coefficient of the 7th pass is 1.335. Appropriate deformation can avoid the generation of internal cracks in the steel billet due to excessive deformation in a single pass, and at the same time balance the repair of the steel billet corners and the overall deformation efficiency.

[0012] Solution 6, which is the optimization of the basic solution. In S2, the working roll diameter of the 1st pass is 565 mm, the working roll diameter of the 2nd pass is 492 mm, the working roll diameter of the 3rd pass is 468 mm, the working roll diameter of the 4th pass is 488 mm, the working roll diameter of the 5th pass is 479 mm, the working roll diameter of the 6th pass is 492 mm, and the working roll diameter of the 7th pass is 464 mm. Using a larger working roll diameter in the first pass can enhance the rigidity of the roll and withstand higher deformation forces. The working roll diameter gradually decreases in subsequent passes, thereby reducing the contact time between the roll and the rolled piece, and thus reducing the temperature rise and oxidation of the rolled piece.

[0013] Solution VII, which is the optimization of the basic solution. In S2, the rolling speed of the first pass is 0.28 m / s, the rolling speed of the second pass is 0.334 m / s, the rolling speed of the third pass is 0.446 m / s, the rolling speed of the fourth pass is 0.611 m / s, the rolling speed of the fifth pass is 0.829 m / s, the rolling speed of the sixth pass is 1.14 m / s, and the rolling speed of the seventh pass is 1.522 m / s. Adopting a lower rolling speed in the first pass can ensure that the corners of the billet are fully filled in the roll grooves, thereby eliminating the corner defects of the billet. The rolling speeds from the second pass to the seventh pass gradually increase, which not only improves the production efficiency but also avoids surface scratches or uneven deformation of the rolled piece due to sudden speed changes through the gradually increasing rolling speed.

[0014] Solution VIII, which is the optimization of the basic solution. A bar and wire mill stand for eliminating corner defects of billets, characterized by including a portal frame. A first bearing seat is bolted to the portal frame. A first roll shaft is rotatably connected to the first bearing seat. A first roll is provided on the first roll shaft. Second bearing seats are bolted to both sides of the portal frame. A second roll shaft is rotatably connected to the second bearing seat. A second roll is provided on the second roll shaft. Roll grooves are provided on both the first roll and the second roll. Through the cooperative action of the upper and lower first rolls and the left and right second rolls, the four corners of the billet are simultaneously rolled, so that the billet is uniformly pressured during the rolling process and the rolling force is dispersed to the whole billet, directly applying reduction deformation to the corners of the billet, thereby avoiding stress concentration at the corners of the billet and reducing the micro-crack defects at the corners of the billet. Description of the Drawings

[0015] Figure 1 is the pass schematic diagram of the first pass to the seventh pass in a bar and wire rolling method for eliminating corner defects of billets according to the present invention; Figure 2 is the three-dimensional view of a bar and wire mill stand for eliminating corner defects of billets according to the present invention; Figure 3 is the front view of a bar and wire mill stand for eliminating corner defects of billets according to the present invention. Detailed Embodiments

[0016] The present invention will be further described in detail below through specific embodiments: The reference numerals in the accompanying drawings of the specification include: 1, portal frame; 2, first bearing seat; 3, first roll shaft; 4, first roll; 5, second bearing seat; 6, second roll shaft; 7, second roll; 8, roll groove.

[0017] Example 1 A bar and wire rolling method for eliminating corner defects of billets, as Figures 1 to 3 shown, includes the following steps: S1: Steel Rotation: First, convey the heated billet to the guide device through the discharging roller table. Then, under the action of the guide plate, make the billet enter the steel rotation roller table. Next, rotate the billet by 45° through the upper and lower torsion rollers to align the corner of the billet with the groove of the upper roll of the rolling mill. Then, convey the billet to the rolling mill through the transport roller table and the V-shaped anti-torsion guide rollers; S2: Rough Rolling: It is possible to roll the billet with a size of 150mm * 150mm into a steel bar through 7 passes of rough rolling. During rough rolling, the temperature of the billet is 1020°C - 1060°C. Among them, the rolling pass of the first pass is a regular octagon, the roll gap value is 15mm, the deformation coefficient is 1.209, the working roll diameter is 565mm, and the rolling speed is 0.28m / s; the rolling pass of the second pass is an ellipse-square shape, the roll gap value is 18mm, the deformation coefficient is 1.18, the working roll diameter is 492mm, and the rolling speed is 0.334m / s; the rolling pass of the third pass is a circular shape, the roll gap value is 15mm, the deformation coefficient is 1.35, the working roll diameter is 468mm, and the rolling speed is 0.446m / s; the rolling pass of the fourth pass is an elliptical shape, the roll gap value is 15mm, the deformation coefficient is 1.37, the working roll diameter is 488mm, and the rolling speed is 0.611m / s; the rolling pass of the fifth pass is a circular shape, the roll gap value is 15mm, the deformation coefficient is 1.357, the working roll diameter is 479mm, and the rolling speed is 0.829m / s; the rolling pass of the sixth pass is an elliptical shape, the roll gap value is 15mm, the deformation coefficient is 1.375, the working roll diameter is 492mm, and the rolling speed is 1.14m / s; the rolling pass of the seventh pass is a circular shape, the roll gap value is 15mm, the deformation coefficient is 1.335, the working roll diameter is 464mm, and the rolling speed is 1.522m / s.

[0018] Example 2 As Figures 1 to 3 described: A bar and wire rod rolling mill stand for eliminating corner defects of billets, including a portal frame 1. A first bearing block 2 is bolted to the portal frame 1. A first roll shaft 3 is rotatably connected to the first bearing block 2. A first roll 4 is provided on the first roll shaft 3. Second bearing blocks 5 are bolted to both sides of the portal frame 1. A second roll shaft 6 is rotatably connected to the second bearing block 5. A second roll 7 is provided on the second roll shaft 6. Roll grooves 8 are provided on both the first roll 4 and the second roll 7.

[0019] The implementation method of this embodiment is: For a bar and wire rod rolling mill stand for eliminating corner defects of billets, when the billet is transported to the rolling mill through the transport roller table, the four corners of the billet are respectively located in the roll grooves 8 on the first roll 4 and the second roll 7. At this time, drive the two first rolls 4 to apply pressure to the billet through the transmission device of the rolling mill to complete rolling.

[0020] In summary, by using an octagonal pass for the first pass of rolling, and at the same time, the rolling mill uses the coordinated action of upper and lower horizontal rolls and left and right vertical rolls to apply pressure to the four corners of the billet simultaneously, forcing the corner metal to be pressed down, welding micro-cracks, and eliminating the protrusions at the corners of the billet, thereby eliminating the stress concentration source and avoiding the problem of corner defects caused by stress concentration.

[0021] The above are only embodiments of the present invention. Common knowledge such as specific structures and characteristics known in the art are not described in detail herein. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. A bar and wire rolling method for eliminating corner defects of steel billets, characterized in that, It includes the following steps: S1: Steel billet rotation: First, convey the heated steel billet to the steel billet rotation device through the charging roller table, then make the steel billet enter the steel billet rotation roller table under the action of the guard plate, rotate the steel billet by 45° through the upper roller and the lower roller of the twisting roller, align the corner of the steel billet with the groove of the upper roller of the rolling mill, and then convey the steel billet to the rolling mill through the transport roller table and the V-shaped anti-twisting guide roller; S2: Rough rolling: Then, roll the steel billet with a size of 150mm * 150mm into a steel bar through 7 passes of rough rolling. Among them, the deformation coefficient of the first pass > 1.2, the deformation coefficient of the second pass is 1.15 - 1.20, and the deformation coefficient of the third pass to the seventh pass is 1.3 - 1.

4.

2. The bar and wire rod rolling method for eliminating corner defects of billets according to claim 1, characterized in that In S2, the temperature of the steel billet during rough rolling is 1020°C - 1060°C.

3. A bar and wire rolling method for eliminating corner defects of billets according to claim 1, characterized in that, In S2, the rolling pass shapes of the first pass to the seventh pass during rough rolling are regular octagon, ellipse square, circle, ellipse, circle, ellipse, and circle in sequence. The steel billet is rolled into a regular octagon with a side length of 70mm through the first pass of rolling.

4. A bar and wire rolling method for eliminating corner defects of steel billets according to claim 1, characterized in that In S2, the roll gap value of the first pass is 15mm, the roll gap value of the second pass is 18mm, and the roll gap values of the third pass to the seventh pass are all 15mm.

5. A bar and wire rod rolling method for eliminating corner defects of steel billets according to claim 1, characterized in that, In S2, the deformation coefficient of the first pass is 1.209, the deformation coefficient of the second pass is 1.18, the deformation coefficient of the third pass is 1.35, the deformation coefficient of the fourth pass is 1.37, the deformation coefficient of the fifth pass is 1.357, the deformation coefficient of the sixth pass is 1.375, and the deformation coefficient of the seventh pass is 1.

335.

6. A bar and wire rod rolling method for eliminating corner defects of steel billets according to claim 1, characterized in that In S2, the working roll diameter of the first pass is 565mm, the working roll diameter of the second pass is 492mm, the working roll diameter of the third pass is 468mm, the working roll diameter of the fourth pass is 488mm, the working roll diameter of the fifth pass is 479mm, the working roll diameter of the sixth pass is 492mm, and the working roll diameter of the seventh pass is 464mm.

7. A bar and wire rolling method for eliminating corner defects of billets according to claim 1, characterized in that, In S2, the rolling speed of the first pass is 0.28m / s, the rolling speed of the second pass is 0.334m / s, the rolling speed of the third pass is 0.446m / s, the rolling speed of the fourth pass is 0.611m / s, the rolling speed of the fifth pass is 0.829m / s, the rolling speed of the sixth pass is 1.14m / s, and the rolling speed of the seventh pass is 1.522m / s.

8. A bar and wire rod rolling mill stand for eliminating corner defects of steel billets, characterized in that, It includes a gantry frame (1), a first bearing seat (2) is bolted to the gantry frame (1), a first roll shaft (3) is rotatably connected to the first bearing seat (2), a first roll (4) is provided on the first roll shaft (3), second bearing seats (5) are bolted to both sides of the gantry frame (1), a second roll shaft (6) is rotatably connected to the second bearing seat (5), a second roll (7) is provided on the second roll shaft (6), and roll grooves (8) are provided on both the first roll (4) and the second roll (7).

Images