A method for controlling cooling after wire rod rolling

Abstract

The present application relates to the technical field of steel smelting, and particularly relates to a kind of wire rod post-rolling controlled cooling method, using Stelmor roller way, before phase change ends, making wire rod in roller way advancing direction swing left and right, roller way before phase change ends is divided into several roller way sections, from entry section, the advancing speed of roller way is alternately distributed as slow, fast, slow, fast, the speed variation range of adjacent two roller way sections is 15%~20%; wherein, wire rod phase change end point is the position that the average temperature of wire rod two sides lap joint point is lower than 600 DEG C. Using the method can improve the uniformity of transverse wire rod cooling, further reduce the same circle strength fluctuation of produced wire rod, without frequently adjusting the angle of Jialing device, and can be suitable for the production of various specifications of wire rod.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, and specifically to a method for controlled cooling after wire rod rolling. Background Technology

[0002] Over 90% of high-carbon steel wire rods undergo further processing such as cold drawing before use. This places high demands on the uniformity of their strength. Excessive fluctuations in wire rod strength can lead to large tension fluctuations during drawing, affecting wire drawing and resulting in large fluctuations in the mechanical properties of the finished wire, thus impacting the wire's pass rate. Therefore, downstream steel wire processing enterprises require that the microstructure and strength fluctuations of the original high-carbon steel wire rods be as small as possible.

[0003] The production process of high-carbon steel wire rod is generally as follows: billet heating → hot rolling → wire drawing → controlled cooling. Currently, the most common high-speed wire rod controlled cooling system is the Steyrmo line. After being drawn into coils, the wire rod enters the Steyrmo roller conveyor for transport, where subsequent coils fall on top of previous coils, and airflow from below the roller conveyor accelerates cooling. However, because the wire rod is densely packed at the overlap points on both sides of the Steyrmo line, while the middle section is loosely packed, there is a situation where the sides cool slowly and the middle cools quickly. This results in uneven cooling in both the transverse and longitudinal directions, leading to uneven strength within the same coil. The wire rod after being drawn into coils exhibits characteristics of uneven transverse packing and multi-stage variable cross-sections in the longitudinal direction.

[0004] In existing technologies, the Jialing device is often used to solve the above problems. It adjusts the airflow distribution on the Steyrmo roller conveyor, increasing the airflow at the overlapping points on both sides and decreasing it in the middle to achieve a more uniform cooling rate for the coil and reduce the strength fluctuations within the same coil. However, the optimal airflow distribution differs for different coil specifications, and the Jialing device cannot adjust it in a timely manner. Furthermore, it is difficult to achieve perfect centering of the coil on the Steyrmo roller conveyor. Even with airflow adjustment, the cooling at the overlapping points on both sides remains uneven, leading to increased strength fluctuations within the same coil. Existing technologies also use methods that alter the roller conveyor speed to misalign the overlapping points of the coil to improve cooling uniformity. However, when using this method, the roller conveyor can only accelerate when there is no drop section. If it decelerates, faster-moving coils can easily insert into slower-moving coils, resulting in reverse insertion and causing the coil to tip and jam during coiling. This limits the applicability of this method. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of the prior art in improving the cooling uniformity of steel wire rods. When using the Jialing device to improve the cooling uniformity of wire rods, it is not possible to adjust in a timely manner when dealing with wire rods of different specifications. When changing the speed of the roller conveyor to make the overlap point of the wire rod misaligned, due to the problem of reverse insertion, it can only accelerate but not decelerate when there is no roller conveyor drop section, which limits the use of this method. Moreover, the strength fluctuation difference of the same coil of the obtained wire rod is still quite large. Therefore, the present invention provides a method for controlled cooling of wire rods after rolling.

[0006] Therefore, the present invention provides the following technical solution:

[0007] The wire rod cooling method after rolling provided by this invention uses a Stellmor roller conveyor. Before the phase transformation ends, the wire rod is made to sway left and right in the forward direction of the roller conveyor. The roller conveyor before the phase transformation ends is divided into several roller conveyor sections. From the inlet section, the forward speed of the roller conveyor is distributed in an alternating pattern of slow, fast, slow, fast. The speed variation range between adjacent roller conveyor sections is 15% to 20%. The end point of the wire rod phase transformation is the position where the average temperature of the overlapping points on both sides of the wire rod is below 600°C.

[0008] In the wire rod controlled cooling method provided by the present invention, in order to make the wire rod swing left and right in the forward direction of the roller table, a method of installing guide rollers on both sides of the roller table can be adopted. Specifically, the guide rollers are installed at equal intervals and are installed alternately on both sides of the roller table. The distance between the equidistant guide rollers is 2 to 3 m.

[0009] Preferably, the wire rod exhibits a left-right swaying state in the forward direction of the roller conveyor, with an swaying amplitude of 2 to 5 cm.

[0010] Preferably, after the phase change of the wire rod is completed, it is restored to a straight line along the direction of the roller conveyor. The wire rod can also be restored to a straight line by using guide rollers.

[0011] Preferably, the speed at the exit section of the Steyrmo roller conveyor is 0.6 to 0.8 m / s.

[0012] Preferably, the speed at the entrance section of the Steyrmo roller conveyor is 0.7 to 1.1 m / s.

[0013] Preferably, the length of the roller conveyor section is 8 to 10 m.

[0014] Preferably, the number of roller conveyor sections before the end of the phase change is ≥3.

[0015] Preferably, in the roller conveyor section before the wire rod phase transformation is completed, the air volume in the middle of the fan is 30% to 45% of the air volume at the edge.

[0016] Preferably, the fan is not turned on in the roller conveyor section after the wire rod phase transformation is completed.

[0017] Preferably, the specifications of the wire rod are 11mm≤φ≤15mm.

[0018] Preferably, the wire rod is made of high-carbon steel with a carbon content of 0.60% to 1.10%.

[0019] The technical solution of this invention has the following advantages:

[0020] The post-rolling controlled cooling method for wire rod provided by this invention utilizes a Stellmor roller conveyor. Before the phase transformation ends, the wire rod is made to oscillate left and right in the forward direction of the roller conveyor. The roller conveyor before the phase transformation ends is divided into several sections. From the inlet section, the forward speed of the roller conveyor is distributed in an alternating pattern of slow, fast, slow, fast, with the speed variation between adjacent sections being 15% to 20%. The phase transformation ends when the average temperature of the overlap points on both sides of the wire rod is below 600°C. This method can improve the uniformity of transverse wire rod cooling, further reduce the strength fluctuation of the same coil in the produced wire rod, is not limited by the height difference of the roller conveyor, does not require frequent adjustment of the angle of the galvanizing device, and is applicable to the production of various specifications of wire rod. Continuously changing the roller conveyor speed and making the wire rod oscillate left and right in the forward direction of the roller conveyor can continuously change the position of the overlap points of the wire rod, making the overlap points more dispersed and helping to improve the uniformity of cooling within the same coil.

[0021] Furthermore, during the production of wire rod, after the wire is unwinding, it is conveyed on a roller conveyor. The coils of later coils fall on top of the coils of earlier coils. If this relationship is disrupted, the coils will interlock, causing them to tip over and jam during winding. To prevent this, the parameters of each section of the roller conveyor must ensure a certain overlap between the coils. In actual operation, if the speed is reduced in a section without a drop section, the faster coils can easily insert into the slower coils in front, making winding impossible. Therefore, generally, the roller conveyor speed only increases and never decreases when there is no drop section (roller conveyor drop section); otherwise, it is easy for reverse insertion to occur. In this invention, the speed can be increased first to pull the coil apart when there is no drop section, and then the speed can be reduced to restore it to near the original position, instead of reducing the speed again at the original position. This avoids the problem of reverse insertion and allows for an alternating distribution of fast, slow, and fast roller conveyor speeds.

[0022] The post-rolling controlled cooling method for wire rod provided by this invention restores the wire rod to a straight line along the roller conveyor direction after the phase transformation is completed. This makes the coiling process smoother and also improves the coil shape quality of the coiled wire rod. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a top view of the shape of the wire rod swaying left and right along the length direction on the Steyrmo roller conveyor in the embodiments of the present invention and Comparative Examples 2 and 3.

[0025] Figure 2 This is a top view schematic diagram showing the state in which the wire rod is restored to a straight line in the forward direction of the Steyrmo roller conveyor in the embodiments of the present invention and Comparative Examples 2 and 3. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Experimental equipment

[0028] The Stellmore Line:

[0029] Fan air volume: 198,000 m³ / h;

[0030] Roller parameters: φ120mm;

[0031] Roller spacing and roller conveyor length: Roller spacing 5cm;

[0032] Entrance section: 4m;

[0033] Sections 1 to 10: Each section of the roller conveyor is 9m long;

[0034] Exit section: 4m.

[0035] Example 1

[0036] This embodiment provides a method for controlled cooling of wire rod after rolling. The material used is 82B (chemical composition by weight percentage: C: 0.82%, Mn: 0.78%, Si: 0.25%, Cr: 0.15%, with the remainder being Fe and unavoidable impurities), a small square billet with a cross-section of 140mm × 140mm. The 82B billet is heated to 1170℃, with the air-to-coal ratio controlled to ≤0.7 during heating. The finishing rolling temperature is 930℃, the final rolling speed is 40m / s, and the wire drawing temperature is 870℃, resulting in a wire rod diameter of 13mm. The wire rod is then drawn onto the Steyrmore roller conveyor for cooling.

[0037] The modifications to the Steyrmo roller conveyor are as follows:

[0038] At the entrance of sections 1 to 7 of the Steilmo roller conveyor, a guide roller is installed every 3m on both sides, and the guide rollers are installed alternately on both sides of the roller conveyor.

[0039] The method is as follows:

[0040] During operation on the Steyrmo roller conveyor, guide rollers in sections 1 to 6 cause the wire rod to oscillate laterally along its length, with an amplitude of 5 cm. The shape of the wire rod on the Steyrmo roller conveyor is as follows: Figure 1 As shown. At the entrance of section 7, guide rollers are used to restore the wire rod to a straight line in the direction of the roller conveyor's advance, as shown. Figure 2 As shown in Table 1, the speed of each section of the Stellmor roller conveyor, the fan air volume setting, and the average temperature at the overlap point on both sides of the wire rod at the outlet are all as described in this embodiment.

[0041] Table 1

[0042]

[0043] Example 2

[0044] This embodiment provides a controlled cooling system and method for wire rod after rolling. The material used is 87B (chemical composition by weight percentage: C: 0.88%, Mn: 0.75%, Si: 0.20%, Cr: 0.15%, with the remainder being Fe and unavoidable impurities), a small square billet with a cross-section of 140mm × 140mm. The 87B billet is heated to 1170℃, with the air-to-coal ratio controlled to ≤0.7 during heating. The finishing rolling temperature is 930℃, the final rolling speed is 36m / s, and the wire drawing temperature is 870℃, resulting in a wire rod diameter of 14mm. The wire rod is then drawn onto the Steyrmore roller conveyor for cooling.

[0045] The modifications to the Steyrmo roller conveyor are as follows:

[0046] At the entrance of sections 1 to 7 of the Steilmo roller conveyor, a guide roller is installed every 3m on both sides, and the guide rollers are installed alternately on both sides of the roller conveyor.

[0047] The method is as follows:

[0048] During operation on the Steyrmo roller conveyor, guide rollers in sections 1 to 6 cause the wire rod to oscillate laterally along its length, with an amplitude of 3 cm. The wire rod's shape on the Steyrmo roller conveyor is as follows: Figure 1 As shown. At the entrance of section 7, guide rollers are used to restore the wire rod to a straight line in the direction of the roller conveyor's advance, as shown. Figure 2 As shown in Table 2, the speed of each section of the Stellmor roller conveyor, the fan air volume setting, and the average temperature at the overlap point on both sides of the wire rod at the outlet are all as described in this embodiment.

[0049] Table 2

[0050]

[0051] Example 3

[0052] This embodiment provides a controlled cooling system and method for wire rod after rolling. The material used is 87B-1 (chemical composition by weight percentage: C: 0.88%, Mn: 0.75%, Si: 0.50%, Cr: 0.15%, V: 0.03%, with the remainder being Fe and unavoidable impurities), a small square billet with a cross-section of 140mm × 140mm. The 87B-1 billet is heated to 1200℃, with the air-to-coal ratio controlled to ≤0.6 during heating. The finishing rolling temperature is 950℃, the final rolling speed is 32m / s, and the wire drawing temperature is 880℃, resulting in a wire rod diameter of 15mm. The wire rod is then drawn onto the Steyrmore roller conveyor for cooling.

[0053] The modifications to the Steyrmo roller conveyor are as follows:

[0054] At the entrance of sections 1 to 7 of the Steilmo roller conveyor, a guide roller is installed every 3m on both sides, and the guide rollers are installed alternately on both sides of the roller conveyor.

[0055] The method is as follows:

[0056] During operation on the Steyrmo roller conveyor, guide rollers in sections 1 to 6 cause the wire rod to oscillate laterally along its length, with an amplitude of 2 cm. The shape of the wire rod on the Steyrmo roller conveyor is as follows: Figure 1 As shown. At the entrance of section 7, guide rollers are used to restore the wire rod to a straight line in the direction of the roller conveyor's advance, as shown. Figure 2 As shown in Table 3, the speed of each section of the Stellmor roller conveyor, the fan air volume setting, and the average temperature at the overlap point on both sides of the wire rod at the outlet are all as described in this embodiment.

[0057] Table 3

[0058]

[0059] Comparative Example 1

[0060] This comparative example provides a controlled cooling system and method for wire rod after rolling. The material used is 82B (chemical composition by weight percentage: C: 0.83%, Mn: 0.75%, Si: 0.20%, Cr: 0.15%, with the remainder being Fe and unavoidable impurities), a small square billet with a cross-section of 140mm × 140mm. The 82B billet is heated to 1170℃, with the air-to-coal ratio controlled to ≤0.7 during heating. The finishing rolling temperature is 930℃, the final rolling speed is 36m / s, and the wire drawing temperature is 870℃, resulting in a wire rod diameter of 14mm. The wire rod is then drawn onto the Steyrmore roller conveyor for cooling.

[0061] Table 4 shows the speed, fan volume setting, and average temperature at the overlap point on both sides of the wire rod at the outlet of each section of the Stellmore roller conveyor in this comparative example.

[0062] Table 4

[0063]

[0064] Comparative Example 2

[0065] This comparative example provides a controlled cooling system and method for wire rod after rolling. The material used is 82B (chemical composition by weight percentage: C: 0.82%, Mn: 0.78%, Si: 0.25%, Cr: 0.15%, with the remainder being Fe and unavoidable impurities), a small square billet with a cross-section of 140mm × 140mm. The 82B billet is heated to 1170℃, with the air-to-coal ratio controlled to ≤0.7 during heating. The finishing rolling temperature is 930℃, the final rolling speed is 40m / s, and the wire drawing temperature is 870℃, resulting in a wire rod diameter of 13mm. The wire rod is then drawn onto the Steyrmore roller conveyor for cooling.

[0066] The modifications to the Steyrmo roller conveyor are as follows:

[0067] At the entrance of sections 1 to 5 of the Steilmo roller conveyor, a guide roller is installed every 3m on both sides, and the guide rollers are installed alternately on both sides of the roller conveyor.

[0068] The method is as follows:

[0069] During operation on the Steyrmo roller conveyor, guide rollers in sections 1 to 4 cause the wire rod to oscillate laterally along its length, with an amplitude of 5 cm. The shape of the wire rod on the Steyrmo roller conveyor is as follows: Figure 1 As shown. At the entrance of section 5, guide rollers are used to restore the wire rod to a straight line in the direction of the roller conveyor's advance, as shown. Figure 2 As shown in Table 5, the speed of each section of the Stellmor roller conveyor, the fan air volume setting, and the average temperature at the overlap point on both sides of the wire rod at the outlet are all as described in this embodiment.

[0070] Table 5

[0071]

[0072] Comparative Example 3

[0073] This comparative example provides a controlled cooling system and method for wire rod after rolling. The material used is 82B (chemical composition by weight percentage: C: 0.82%, Mn: 0.78%, Si: 0.25%, Cr: 0.15%, with the remainder being Fe and unavoidable impurities), a small square billet with a cross-section of 140mm × 140mm. The 82B billet is heated to 1170℃, with the air-to-coal ratio controlled to ≤0.7 during heating. The finishing rolling temperature is 930℃, the final rolling speed is 40m / s, and the wire drawing temperature is 870℃, resulting in a wire rod diameter of 13mm. The wire rod is then drawn onto the Steyrmore roller conveyor for cooling.

[0074] The modifications to the Steyrmo roller conveyor are as follows:

[0075] At the entrance of sections 1 to 7 of the Steilmo roller conveyor, a guide roller is installed every 3m on both sides, and the guide rollers are installed alternately on both sides of the roller conveyor.

[0076] The method is as follows:

[0077] During operation on the Steyrmo roller conveyor, guide rollers in sections 1 to 6 cause the wire rod to oscillate laterally along its length, with an amplitude of 5 cm. The shape of the wire rod on the Steyrmo roller conveyor is as follows: Figure 1 As shown. At the entrance of section 7, guide rollers are used to restore the wire rod to a straight line in the direction of the roller conveyor's advance, as shown. Figure 2 As shown in Table 6, the speed of each section of the Stellmor roller conveyor, the fan air volume setting, and the average temperature at the overlap point on both sides of the wire rod at the outlet are all as described in this embodiment.

[0078] Table 6

[0079]

[0080] Test Example 1

[0081] The tensile strength properties of the wire rods obtained in the embodiments and comparative examples of the present invention were tested. Eight rods were tested per coil. The testing standard used was GB / T228.8-2021 Metallic materials, tensile testing - Part 1: Test method at room temperature. The results are shown in Table 7.

[0082] Table 7

[0083]

[0084]

[0085] The tensile strength results show that the wire rods obtained using the method of this invention in the examples have high tensile strength and small fluctuations within the same roll. In contrast, the wire rods obtained in Comparative Example 1 (where the wire rod was not allowed to oscillate during cooling), Comparative Example 2 (where the wire rod oscillation was stopped before the end of the phase transformation section), and Comparative Example 3 (where the speed variation before and after a section of the roller conveyor was not within the range of 15%–20%) all exhibit low tensile strength and large fluctuations within the same roll. The controlled cooling method for wire rods after rolling in this invention can produce wire rods with high tensile strength and small fluctuations within the same roll, and it is applicable to wire rods of various diameters and high-carbon steel specifications.

[0086] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for controlled cooling of wire rod after rolling, characterized in that, Using the Stellmore roller conveyor, before the phase change is completed, the wire rod is made to sway left and right in the direction of the roller conveyor. The roller conveyor before the phase change is completed is divided into several roller conveyor sections. Starting from the inlet section, the forward speed of the roller conveyor is distributed in an alternating pattern of slow, fast, slow, fast, with the speed change range between adjacent roller conveyor sections being 15% to 20%. Among them, the end point of phase transformation of the wire rod is the position where the average temperature of the overlapping points on both sides of the wire rod is below 600℃; The wire rod exhibits a left-right swaying state in the direction of the roller conveyor, with an swaying amplitude of 2~5cm; it also includes the state in which the wire rod returns to a straight line in the direction of the roller conveyor after the phase transformation is completed. The specifications of the wire rod are 11mm≤φ≤15mm; The wire rod is made of 82B high-carbon steel or 87B high-carbon steel.

2. The method for controlled cooling of wire rod after rolling according to claim 1, characterized in that, The speed at the exit section of the Steyrmo roller conveyor is 0.6~0.8 m / s.

3. The controlled cooling method for wire rod after rolling according to claim 1, characterized in that, The speed at the entrance section of the Steyrmo roller conveyor is 0.7~1.1 m / s.

4. The method for controlled cooling of wire rod after rolling according to claim 1, characterized in that, The length of the roller conveyor section is 8~10m.

5. The method for controlled cooling of wire rod after rolling according to any one of claims 1 to 4, characterized in that, The number of roller conveyor sections before the end of the phase change is ≥3.

6. The method for controlled cooling of wire rod after rolling according to claim 1, characterized in that, In the roller conveyor section before the wire rod phase transformation is completed, the air volume in the middle of the fan is 30% to 45% of the air volume at the edge; The fan is not turned on in the roller conveyor section after the wire rod phase change is completed.

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