A method for rolling threaded steel

Abstract

The embodiment of the present invention provides a method for rolling threaded steel, wherein the specifications of the rolled threaded steel are φ12 threaded steel, φ14 threaded steel, φ16 threaded steel, φ18 threaded steel and φ20 threaded steel, and the threaded steel rolling method comprises: for rolling the threaded steel of different specifications, the first 18 rolling mills all adopt the same rolling pass and hole structure; and special rolling passes and hole types are selected from the 19th to 24th rolling mills to respectively roll the threaded steel of different specifications. Through this scheme, when switching threaded steel of different specifications, the first 18 rolling mills do not need to change the hole structure, and the adjustment work of the 19th to 24th rolling mills is greatly reduced, thereby saving the time required for adjustment and improving work efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of steel production, and in particular to a threaded steel rolling method. Background Art

[0002] The double-high bar production line layout technology is one of the world's cutting-edge process layouts. It has the characteristics of high precision, high output, and a wide variety of product specifications. It is currently widely used in the production of rebar. The most commonly used double-high bar production line has a rolling mill arrangement of "6+6+6+4×2+2×2", of which the "6+6+6 (rough rolling + medium rolling + pre-finishing rolling)" unit equipment is a short stress rolling mill, and the "4×2+2×2 (finishing rolling + diameter reduction)" unit equipment is a modular rolling mill. Since the 18# train, the rolling line is a double-line split type divided into two. The production tasks of the double-high bar production line can cover the specifications of double-cut Φ12 rebar to Φ20 rebar, and the production types are more. Under the influence of market environment and warehousing logistics and other factors, the double-high bar production line must frequently switch product specifications.

[0003] The modular rolling mill requires stable incoming materials and high dimensional accuracy. Therefore, in terms of technology, the pre-finishing rolling material size is designed according to the material size and elongation coefficient of each pass of the modular rolling mill of each specification, which are 12 screws Φ18.5 round, 14 screws and 18 screws Φ23 round, 16 screws and 20 screws Φ24.5 round. Taking the material shape of the last pass of pre-finishing rolling as the node, considering the stability and uniformity of the cutting hole shape, three series of hole shapes A, D, and E are designed respectively. See the attached for details. Figure 2 At the same time, in the upstream part with the same hole type, different product specifications also need to adjust the roll gap to achieve the function of rolling different material types with a single hole type.

[0004] In the process of implementing the present invention, the inventors found that there are at least the following problems in the prior art:

[0005] When it is necessary to produce rebars of different specifications and switch equipment, it is necessary to replace multiple rolling mill equipment and adjust the material roll gap on a large scale, which leads to long equipment replacement time, long finished product size adjustment process, low production control stability, and an average of 4 to 6 hours per rolling change, affecting the monthly effective operation rate by more than 4.5%. The adjustment process causes excessive metal quality loss, and downtime causes energy waste. At the same time, large-scale equipment replacement is accompanied by high labor intensity, which consumes employees' energy and has an adverse impact on stable production. Therefore, how to reduce the switching and adjustment work time and improve production efficiency when rolling rebars of different specifications is a problem that needs to be solved. Summary of the invention

[0006] The embodiment of the present invention provides a method for rolling threaded steel bars to solve the problem in the prior art that a lot of adjustment time is required when rolling threaded steel bars of different specifications.

[0007] To achieve the above-mentioned purpose, an embodiment of the present invention provides a method for rolling rebar, wherein the specifications of the rolled rebar are φ12 rebar, or φ14 rebar, or φ16 rebar, or φ18 rebar and φ20 rebar, and the rebar rolling method comprises: for rolling the rebars of different specifications mentioned above, the first 18 rolling mills all adopt the same rolling passes and hole structure; and special rolling passes and hole structures are selected from the 19th to 24th rolling mills to respectively roll the rebars of different specifications mentioned above.

[0008] Furthermore, the first 18 rolling mills all use the same rolling passes and hole structure, specifically including: determining 16 common rolling passes and hole structures from the first 18 rolling mills; wherein, the rolling mill stands corresponding to the common rolling passes are: the 1st to 10th stands, and the 13th to 18th stands use the same rolling passes and hole structure, and the 11th and 12th stands are empty.

[0009] Further, special rolling passes and pass types are selected from the 19th to 24th rolling mills, specifically including: when the specification of the current rebar to be rolled is φ12 rebar, the 19th to 24th mills are selected as special rolling passes for φ12 rebar; if the specification of the current rebar to be rolled is φ14 rebar or φ16 rebar, the 19th, 20th, 23rd and 24th mills are selected as special rolling passes for φ14 rebar or φ16 rebar; if the specification of the current rebar to be rolled is φ18 rebar or φ20 rebar, the 23rd and 24th mills are selected as special rolling passes for φ18 rebar or φ20 rebar.

[0010] Furthermore, before the first 18 rolling mills all adopt the same rolling pass and hole structure, it also includes: setting the rolling line to be composed of a roughing mill, an intermediate rolling mill, a pre-finishing mill, a finishing mill and a diameter reducing mill in sequence, wherein a double-line slicing setting is performed starting from the finishing mill, the roughing mill includes 6 rolling mills, the intermediate rolling mill includes 6 rolling mills, the pre-finishing mill includes 6 rolling mills, the finishing mill includes 4×2 rolling mills, and the diameter reducing mill includes 2×2 rolling mills. The 1st to 6th rolling mills are roughing mills, the 7th to 12th rolling mills are intermediate rolling mills, the 13th to 18th rolling mills are pre-finishing mills, the 19th to 22nd rolling mills are finishing mills, and the 23rd and 24th rolling mills are diameter reducing mills.

[0011] Furthermore, the first 18 rolling mills all use the same rolling passes and hole structure, and also include: setting corresponding hole structures on the 1st to 10th stands, and the 13th to 18th stands respectively; among them, the hole structure used by the 6th rolling mill is φ84mm circular; the hole structure used by the 10th rolling mill is φ54mm circular.

[0012] Furthermore, the rebar rolling method also includes: adjusting the roll gap of the rolling mill to control the output size.

[0013] Further, the roll gap of the rolling mill is adjusted to control the discharge size, specifically including: if the specification of the rebar to be rolled is φ12 rebar, or φ14 rebar, or φ18 rebar, the roll gap of the 17th rolling mill and the roll gap of the 18th rolling mill are adjusted so that the discharge size after passing through the 18th rolling mill is φ22 circle; if the specification of the rebar to be rolled is φ16 rebar, or φ20 rebar, the roll gap of the 17th rolling mill and the roll gap of the 18th rolling mill are adjusted so that the discharge size after passing through the 18th rolling mill is φ24 circle.

[0014] Furthermore, before entering the first rolling mill, the cross-sectional size of the incoming material is 165mm×165mm.

[0015] The above technical solution has the following beneficial effects:

[0016] After the original double-high bar production line is improved by the technical solution of the present invention, when switching the rebar specifications, the 1st to 18th batches do not need to replace the rolling mill equipment, and the 1st to 16th batches do not need to adjust the material size too much, reducing the replacement of the rolling mill equipment by 7 batches and the material adjustment by 8 passes, which greatly reduces the labor intensity of employees. At the same time, the smaller material adjustment amount shortens the adjustment process of specification switching, improves the stability of production control, and reduces the metal quality loss of adjustment. At the same time, the rolling time is reduced to 2 hours, which is shortened to 50% of the original time, increasing the monthly effective operation rate by 2.2%, and reducing energy consumption.

[0017] In addition, the technical solution of this application also has the following characteristics:

[0018] After adopting this technical solution, the reserve volume of 7 offline rolling mills was reduced by 50%, the inventory amount was reduced, the pressure on roll processing and the workload of roll preparation in the production workshop were reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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 will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a schematic diagram of the rolling process when rolling φ12-φ20 threaded steel bars in an embodiment of the present invention;

[0021] Figure 2 It is a schematic diagram of the rolling process when rolling φ12~φ20 threaded steel in the prior art;

[0022] Figure 3 It is a schematic diagram of the hole structure on each rolling mill in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] like Figure 1 and Figure 3 As shown, an embodiment of the present invention provides a threaded steel rolling method, which is used to roll threaded steel with a specification of φ12 threaded steel, or φ14 threaded steel, or φ16 threaded steel, or φ18 threaded steel and φ20 threaded steel, and the threaded steel rolling method includes:

[0025] S101. For the rolling of the above-mentioned rebars of different specifications, the first 18 rolling mills all adopt the same rolling pass and hole structure;

[0026] S102. Select special rolling passes and pass types from the 19th to 24th rolling mills to respectively roll the above-mentioned rebars of different specifications.

[0027] In the prior art, the rolling pass arrangement for Φ12 threaded steel bar to Φ20 threaded steel bar is as follows: Figure 2As shown. As can be seen from the figure, when the production task is switched from Φ12 rebar to Φ14 rebar, the hole structure needs to be adjusted at the 9th rolling mill, and then in the process from the 9th to the 24th, a total of 12 rolling passes are required (among which the 11th, 12th, 21st and 22nd are empty and no hole structure adjustment is required); for Φ16 rebar, the hole structure needs to be adjusted at the 10th rolling mill, and then in the process from the 10th to the 24th, a total of 9 rolling passes are required (among which the 11th, 12th, 17th, 18th, 21st and 22nd are empty and no hole structure adjustment is required); for Φ18 rebar and Φ20 For rebar, the hole structure needs to be adjusted at the 18th rolling mill, and then from the 18th to the 24th rolling mill, a total of 2 rolling passes are required (the 23rd and 24th rolling mills, and the rest are empty). In summary, in the current technology, when switching between Φ12 rebar and Φ20 rebar, more rolling mills need to adjust the hole structure, which is labor-intensive and inefficient; and for Φ14 and Φ16 rebar, there are also more rolling passes.

[0028] To this end, the idea of ​​this application to solve this problem is to reduce the replacement of rolling mill equipment and the adjustment of material size when switching production specifications, reduce the time for changing rolling, reduce energy consumption, improve the effective operation rate and production stability, and reduce the labor intensity of employees. The specific improvements include the unification of multi-series hole types, reducing the number of equipment replacements for specification switching, unifying the range of material size to reduce the material roll gap adjustment for specification switching, and solving the contradiction between the high requirements of the module mill for incoming materials and the simplification of multi-series hole types by establishing a matching relationship between the material extension of each specification module mill and the pre-finishing rolling output.

[0029] Furthermore, the step S101 specifically includes:

[0030] S1011, determining 16 common rolling passes and hole structures from the first 18 rolling mills; wherein,

[0031] The rolling mill stands corresponding to the common rolling passes are: the 1st to 10th stands and the 13th to 18th stands adopt the same rolling passes and hole structure, and the 11th and 12th stands are empty.

[0032] The step S102 specifically includes:

[0033] S1021. When the specification of the rebar to be rolled is φ12 rebar, the 19th to 24th passes are selected as special rolling passes for φ12 rebar;

[0034] S1022. When the specification of the rebar to be rolled is φ14 rebar or φ16 rebar, the 19th, 20th, 23rd and 24th passes are selected as special rolling passes for φ14 rebar or φ16 rebar;

[0035] S1023. When the specification of the rebar to be rolled is φ18 rebar or φ20 rebar, the 23rd and 24th passes are selected as special rolling passes for φ18 rebar or φ20 rebar.

[0036] When each hole structure is Figure 3 After the improved design shown, when switching between different specifications of rebar, the rolling pass can be changed to Figure 1 The way shown:

[0037] When rolling Φ12, Φ14, Φ16, Φ18, and Φ20 rebars, the first 18 rolling mills have the same passes and hole types, of which 16 common rolling passes and hole types are determined, and the 19th to 24th rolling mills use special passes and hole types; and for Φ14 to Φ20 rebars, on the basis of sharing the same passes and the same hole types with the 1st to 18th rolling mills of Φ12 rebar, they all start to switch to special rolling passes from the 19th rolling mill. Φ14 rebar and Φ16 rebar need to go through 4 rolling passes from the 19th to the 24th (the 21st and 22nd passes are empty and no hole structure adjustment is required); Φ18 rebar and Φ20 rebar need to go through 2 rolling passes from the 19th to the 24th (the 23rd and 24th passes, and the rest are empty). Therefore, in general, when switching from Φ12 to Φ14 rebar and Φ16, Φ18 and Φ20 rebar production, the number of material adjustments is reduced, the number of rolling passes is also reduced, and the working speed is significantly improved; at the same time, Φ14~Φ20 rebars are all transferred to special rolling passes from the 19th, so the workload of adjusting the hole structure is greatly reduced, and the labor efficiency is improved.

[0038] Furthermore, before step S101, the method further includes:

[0039] S001. Set the rolling line to consist of a roughing mill, an intermediate mill, a pre-finishing mill, a finishing mill and a reducing mill in sequence, wherein a double-line cutting setting is performed starting from the finishing mill, the roughing mill includes 6 trains of mills, the intermediate mill includes 6 trains of mills, the pre-finishing mill includes 6 trains of mills, the finishing mill includes 4×2 trains of mills, and the reducing mill includes 2×2 trains of mills.

[0040] The overall layout of the improved rolling line has not changed, and double-line slitting is still performed after the pre-finishing mill to maximize production efficiency.

[0041] Furthermore, the step S101 further includes:

[0042] S1012, respectively set corresponding hole structures on the 1st to 10th trains and the 13th to 18th trains; among them, the hole structure used by the 6th train is set to a φ84mm circle; the hole structure used by the 10th train is set to a φ54mm circle.

[0043] Furthermore, the threaded steel rolling method further comprises:

[0044] S103, adjusting the roll gap of the rolling mill to control the discharge size, that is, when the pass profile of the 17th and 18th rolling mills remains unchanged (Φ12, Φ14, Φ16, Φ18, Φ20 rebars use the same pass profile in the 17th and 18th rolling mills), different roll gaps are set according to different specifications of the rebars.

[0045] The step S103 specifically includes:

[0046] S1031, if the specification of the rebar to be rolled is φ12 rebar, φ14 rebar, or φ18 rebar, adjust the roll gap between the 17th and 18th rolling mills so that the size of the material after passing through the 18th rolling mill is φ22;

[0047] S1032. If the specification of the rebar to be rolled is φ16 rebar or φ20 rebar, adjust the roll gaps of the 17th and 18th rolling mills so that the size of the output material after passing through the 18th rolling mill is φ24.

[0048] Furthermore, before entering the first rolling mill, the cross-sectional size of the incoming material is 165 mm × 165 mm. The rebar rolling method of this solution and the related equipment and hole structure used can better adapt to the incoming material of this specification.

[0049] The specific measures for adjusting the prior art in this application are as follows (T in the figure represents a flat roller, a hole-free type):

[0050] 1. There are differences between empty passes and non-empty passes in the replacement of rolling mill equipment. The hole type sequence of φ12 rebar 11#~18# machine train is arranged to 13#~20# machine train (even if the 11# and 12# trains after improvement are empty passes), and the 17# and 18# passes of φ16 rebar and φ20 rebar are increased, and the layout of φ12 rebar~φ20 rebar 1#~18# trains is unified. The rolling mill frames and hole profiles of the present invention are arranged as follows: 1-5# rolling mills are flat rolls without hole profiles, 6# rolling mill hole profile is circular hole profile 6A, 7# rolling mill hole profile is elliptical 7A, 8# rolling mill hole profile is circular hole profile 8A, 9# rolling mill hole profile is elliptical hole profile 09, 10# rolling mill hole profile is circular hole profile 10B, 11# rolling mill and 12# rolling mill are empty, 13# rolling mill is flat roll, 14# rolling mill hole profile is box hole 14D, 15# rolling mill hole profile is double circular pre-cut hole profile 15K, 16# rolling mill hole profile is cutting hole profile 16K, 17# rolling mill hole profile is elliptical 17C, 18# rolling mill hole profile is circular 18K, and starting from 19# rolling mill, the rolling passes and rolling hole profiles change with different specifications of rebar.

[0051] The sizes of the circular hole types 6A, 8A, and 10B gradually decrease, and the sizes of the elliptical hole types 7A and 09 gradually decrease.

[0052] For the 19# rolling mill, the oval hole type 19D is used for rolling φ12 rebar, the oval hole type 19E is used for rolling φ14 rebar, the oval hole type 19F is used for rolling φ16 rebar, and the 19# rolling mill is empty for rolling φ18 rebar and φ20 rebar. Among them, the oval hole types 19D, 19E, and 19F have the same or similar shapes, but the sizes gradually increase.

[0053] The 20# rolling mill uses the circular hole type 20D for rolling φ12 rebar, the circular hole type 20E for rolling φ14 rebar, the circular hole type 20F for rolling φ16 rebar, and the 20# rolling mill is empty for rolling φ18 rebar and φ20 rebar. Among them, the elliptical hole types 20D, 20E, and 20F have the same or similar shapes, but the size gradually increases.

[0054] The 21# rolling mill and the 22# rolling mill rolled φ12 rebar, φ14 rebar, φ16 rebar, φ18 rebar and φ20 rebar, all of which were empty.

[0055] 23# rolling mill uses elliptical hole type 12K2 for rolling φ12 rebar, elliptical hole type 14K2 for rolling φ14 rebar, elliptical hole type 16K2 for rolling φ16 rebar, elliptical hole type 18K2 for rolling φ18 rebar, and elliptical hole type 20K2 for rolling φ20 rebar. The above-mentioned elliptical hole types 12K2, 14K2, 16K2, 18K2 and 20K2 have the same or similar shapes and gradually increase in size.

[0056] The 24# rolling mill is a finished product rolling mill. The circular hole type 12K1 is used for rolling φ12 rebar, the circular hole type 14K1 is used for rolling φ14 rebar, the circular hole type 16K1 is used for rolling φ16 rebar, the circular hole type 18K1 is used for rolling φ18 rebar, and the circular hole type 20K1 is used for rolling φ20 rebar. The circular hole types 12K1, 14K1, 16K1, 18K1 and 20K1 of the above specifications are finished product hole types, with the same or similar shapes and gradually increasing sizes.

[0057] 2. The key to multi-series pass types lies in the module mill control and the differentiation of upstream incoming material size. Adjust the module mill extension coefficient and roll gap control to achieve the optimal matching of the Φ22 circle of φ12 rebar, φ14 rebar, φ18 rebar and the Φ24mm circle of φ16 rebar and φ20mm rebar for pre-finishing rolling. The default unit of size in this application is mm.

[0058] 3. Reduce the number of pre-finishing rolling batches 14# to one GB14D hole type, and design GB15K, GB16K, GB17C, and GB18K hole types for batches 15#, 16#, 17#, and 18# respectively to replace the original hole types. On the one hand, by adjusting the gap between the 17# and 18# rolls, the same group of pre-finishing rolling hole types can be discharged with Φ22mm circles and Φ24mm circles. On the other hand, the stability and uniformity of the cutting are ensured by changing the angle and base circle of the cutting hole type.

[0059] 4. Further streamline the rough rolling, intermediate rolling hole and material type upstream of pre-finishing rolling, optimize the hole type of 6# and 8# rolling mills, use the PB10B hole type for the 10# mill, and design the 10# mill discharge as Φ54 circular universal according to the material type roll gap of the pre-finishing mill. Design the 6# mill material as Φ84 circular universal based on the material type control of the intermediate mill and the cross-sectional size of the billet as the two end nodes, and further optimize the roll gap of each pass of rough rolling.

[0060] On the double high bar production line of the present invention, the rolling speeds of the above five specifications are: φ12 rebar: 38m / s, φ14 rebar: 29m / s, φ16 rebar: 23m / s, φ18 rebar: 18m / s, φ20 rebar: 15m / s. The design of the rolling pass and pass type of the present invention enables the above five specifications to achieve the maximum commonality of pass and pass type under high-speed rolling, and ensures that the rolled products meet national standards.

[0061] In the above detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are clearly stated in each claim. On the contrary, as reflected in the appended claims, the invention is in a state of having less than all the features of the disclosed individual embodiments. Therefore, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0062] The disclosed embodiments are described above to enable any person skilled in the art to implement or use the present invention. Various modifications of these embodiments are obvious to those skilled in the art, and the general principles defined herein may also be applied to other embodiments without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0063] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for rolling threaded steel, characterized in that: The specification of the rolled threaded steel bar is φ12 threaded steel bar, or φ14 threaded steel bar, or φ16 threaded steel bar, or φ18 threaded steel bar, or φ20 threaded steel bar, and the threaded steel rolling method comprises: For the rolling of the above-mentioned rebars of different specifications, the first 18 rolling mills all adopted the same rolling pass and hole structure; Selecting special rolling passes and pass types from the 19th to 24th rolling mills to respectively roll the above-mentioned rebars of different specifications; The first 18 rolling mills all use the same rolling pass and hole structure, including: 16 common rolling passes and hole structures are determined from the first 18 rolling mills; wherein, The rolling mill stands corresponding to the common rolling passes are: the 1st to 10th stands, and the 13th to 18th stands adopt the same rolling passes and hole structure, and the 11th and 12th stands are empty passes; The first 18 rolling mills all use the same rolling pass and hole structure, and also include: The corresponding hole structures are set on the 1st to 10th flights, and the 13th to 18th flights respectively; among which, The hole structure used by the 6th rolling mill is set as φ84mm round; The hole structure used by the 10th rolling mill is set to φ54mm round; Before the first 18 rolling mills all adopt the same rolling pass and hole structure, it also includes: The rolling line is arranged to be composed of a roughing mill, an intermediate rolling mill, a pre-finishing mill, a finishing mill and a reducing mill in sequence, wherein a double-line slitting arrangement is performed starting from the finishing mill, the roughing mill includes 6 rolling mills, the intermediate rolling mill includes 6 rolling mills, the pre-finishing mill includes 6 rolling mills, the finishing mill includes 4×2 rolling mills, and the reducing mill includes 2×2 rolling mills; On the double high bar production line, the rolling speeds of the above five specifications are: φ12 rebar: 38m / s, φ14 rebar: 29m / s, φ16 rebar: 23m / s, φ18 rebar: 18m / s, φ20 rebar: 15m / s; The selection of special rolling passes and pass types from the 19th to 24th rolling mills specifically includes: When the specification of the rebar to be rolled is φ12 rebar, the 19th to 24th passes are selected as the special rolling passes for φ12 rebar; When the specification of the current rebar to be rolled is φ14 rebar or φ16 rebar, the 19th, 20th, 23rd and 24th passes are selected as special rolling passes for φ14 rebar or φ16 rebar; When the specification of the current rebar to be rolled is φ18 rebar or φ20 rebar, the 23rd and 24th passes are selected as special rolling passes for φ18 rebar or φ20 rebar.

2. The method for rolling threaded steel bars according to claim 1, characterized in that: The threaded steel rolling method further comprises: Adjust the mill roll gap to control the output size.

3. The method for rolling threaded steel bars according to claim 2, characterized in that: The adjusting of the roll gap of the rolling mill to control the size of the discharged material specifically includes: If the specification of the rebar to be rolled is φ12 rebar, φ14 rebar, or φ18 rebar, the roll gap of the 17th rolling mill and the roll gap of the 18th rolling mill are adjusted so that the size of the material after passing through the 18th rolling mill is φ22 round; If the specification of the rebar to be rolled is φ16 rebar or φ20 rebar, the roll gap of the 17th rolling mill and the roll gap of the 18th rolling mill are adjusted so that the size of the material after passing through the 18th rolling mill is φ24 circle.

4. The method for rolling threaded steel bars according to claim 1, characterized in that: Before entering the first rolling mill, the cross-sectional size of the incoming material is 165mm×165mm.

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