Control method for high-speed wire rod hot-rolled wire rod with average oxide scale thickness smaller than or equal to 2 microns

Abstract

The invention discloses a control method for a high-speed wire rod hot-rolled wire rod with the average thickness of oxide scale smaller than or equal to 2 microns, which comprises the following steps of: (1) reducing the generation of oxide scale in the production process by controlling the rolling temperature of a finishing mill and the finish rolling temperature of a reducing sizing mill; (2) oxidation of the wire rod at high temperature is reduced in a manner of air sealing of a rear guide groove of a finishing mill and a reducing and sizing mill; (3) reducing the production rate of the oxide scale on the air cooling line by controlling the spinning temperature; and (4) the cooling speed of the fan is controlled, and the temperature interval of oxide scale production is quickly strided. Compared with a high-speed wire produced by a normal process, the high-speed wire obtained by the control method disclosed by the invention has the advantages that the scale thickness is reduced to below 2 microns, the metal yield per ton of steel is increased by about 2Kg after surface pretreatment of downstream wire drawing manufacturers, the iron loss is reduced, and the economic benefit of an industrial chain is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a control method for a high-speed wire hot-rolled wire rod with an average oxide scale thickness of ≤2 μm. Background Art

[0002] High-speed wire hot-rolled wire rods are widely used in all aspects of production. The hot-rolled wire rods are drawn into steel wires of corresponding specifications by drawing process, which are used in tire frames, ropes, cables, hoses, etc., with large consumption and wide application.

[0003] Hot rolled coils can only get the ideal size and strength after further processing. Generally, they need to go through surface pretreatment to remove the surface oxide scale for further drawing production. Under the same specifications, the thinner the oxide scale of the wire rod, the higher the metal recovery rate of the downstream drawing manufacturer. At the same time, the thinner the oxide scale of the hot rolled wire rod, the higher the yield rate of the steel mill, and both upstream and downstream manufacturers have good economic benefits.

[0004] Taking the high-speed wire hot-rolled wire rod with a wire diameter of 6.5 as an example, the oxide scale thickness of the hot-rolled wire rod produced by the current high-speed wire hot-rolled wire rod rolling technology is generally above 5μm, and the weight of the oxide scale per ton is about 6Kg. Every 1μm reduction in the oxide scale thickness can reduce the iron loss by about 1Kg, with significant economic benefits. Therefore, a new process is urgently needed to reduce the oxide scale thickness of high-speed wire hot-rolled wire rod as much as possible. Summary of the invention

[0005] Technical problem to be solved: In response to the above technical problem, the present invention provides a control method for high-speed wire hot-rolled wire rod with an average iron oxide scale thickness of ≤2μm, so as to improve the yield of wire rod production, reduce iron loss, increase the metal recovery rate of downstream manufacturers, and improve the economic benefits of the industrial chain.

[0006] Technical solution: A control method for high-speed hot-rolled wire rod with an average oxide scale thickness of ≤2μm, comprising the following steps:

[0007] (1) Reduce the generation of iron oxide scale during the production process by controlling the rolling temperature of the finishing mill and the final rolling temperature of the sizing mill;

[0008] (2) Reduce the oxidation of wire at high temperature by sealing the guide groove after the finishing mill and the sizing mill;

[0009] (3) By controlling the spinning temperature, the production rate of iron oxide scale on the air cooling line is reduced;

[0010] (4) Control the cooling speed of the fan to quickly cross the temperature range of iron oxide production.

[0011] Preferably, the outlet temperature of the finishing mill is controlled below 950°C, and the final rolling temperature of the sizing mill is controlled below 900°C; when the manganese content is ≥0.6wt.% or the chromium content is ≥0.25wt.%, the outlet temperature of the finishing mill is controlled below 970°C, and the final rolling temperature of the sizing mill is controlled below 920°C.

[0012] Preferably, the amount of cooling water between the frames of the finishing mill and the reducing and sizing mill is increased by 30%, and the pressure is controlled at 0.3-0.35 MPa.

[0013] Preferably, the finishing mill and the guide groove after sizing are sealed with industrial nitrogen.

[0014] Preferably, the spinning temperature is 800°C to 850°C.

[0015] Preferably, the air volume of a single cooling fan of the post-spinning air cooling line is greater than 200,000 cubic meters per hour, and the number of fans is determined according to the wire diameter specifications.

[0016] Beneficial effect: The invention provides a control method for high-speed wire hot-rolled wire rod with an average oxide scale thickness of ≤2μm, wherein the oxide scale thickness is ≤2μm. Compared with the high-speed wire produced by the normal process, the oxide scale thickness is reduced to below 2μm, and the downstream wire drawing factory increases the metal yield per ton of steel to about 3Kg after surface pretreatment, reduces iron loss, and improves the economic benefits of the industrial chain. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the empty guide groove of the present invention. DETAILED DESCRIPTION

[0018] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0019] Example 1

[0020] A control method for a high-speed hot-rolled wire rod with an average oxide scale thickness of ≤2 μm, comprising the following steps:

[0021] (1) By controlling the rolling temperature of the finishing mill and the final rolling temperature of the reducing and sizing mill, the generation of iron oxide scale in the production process is reduced; specifically: the outlet temperature of the finishing mill is controlled below 950°C, and the final rolling temperature of the reducing and sizing mill is controlled below 900°C; when the manganese content is ≥0.6wt.% or the chromium content is ≥0.25wt.%, the outlet temperature of the finishing mill is controlled below 970°C, and the final rolling temperature of the reducing and sizing mill is controlled below 920°C. The cooling water volume between the frames of the finishing mill and the reducing and sizing mill is increased by 30%, and the pressure is controlled at 0.3-0.35MPa.

[0022] (2) Reduce the oxidation of wire rods at high temperatures by sealing the guide grooves after the finishing mill and the sizing mill; specifically: the guide grooves after the finishing mill and the sizing mill are empty (such as Figure 1 (As shown) industrial nitrogen gas sealing is adopted, and a nitrogen input pipeline is connected to one side of the entrance end of each section of the guide groove. Nitrogen is input when the rolled material passes through, and the pressure is about 0.3MPa, which effectively reduces the generation of iron oxide scale.

[0023] (3) By controlling the spinning temperature, the rate of formation of iron oxide scale on the air cooling line is reduced; specifically: the spinning temperature is 840°C to 850°C.

[0024] (4) Control the cooling speed of the fan to quickly cross the temperature range of iron oxide generation; specifically, the air volume of a single cooling fan of the post-spinning air-cooling line is greater than 200,000 cubic meters per hour, 7 fans are used for the wire diameter of 5.5 mm, 8 fans are used for the wire diameter of 6.5 mm, and 9 fans are used for the wire diameter of 7 mm. The larger the specification, the more fans are needed. The specific fan air volume is shown in Table 1 below:

[0025] Table 1 Air volume of the fan in Example 1

[0026]

[0027] The wire rod produced by the process of Example 1 was tested and the thickness was measured at points divided by 120° on the circumference of the cross section of the wire rod. The arithmetic average thickness of the oxide scale at the three points was about 2 μm.

[0028] Example 2

[0029] (1) By controlling the rolling temperature of the finishing mill and the final rolling temperature of the reducing and sizing mill, the generation of iron oxide scale in the production process is reduced; specifically: the outlet temperature of the finishing mill is controlled below 950°C, and the final rolling temperature of the reducing and sizing mill is controlled below 900°C; when the manganese content is ≥0.6wt.% or the chromium content is ≥0.25wt.%, the outlet temperature of the finishing mill is controlled below 970°C, and the final rolling temperature of the reducing and sizing mill is controlled below 920°C. The cooling water volume between the frames of the finishing mill and the reducing and sizing mill is increased by 30%, and the pressure is controlled at 0.3-0.35MPa.

[0030] (2) Reduce the oxidation of wire rods at high temperatures by sealing the guide grooves after the finishing mill and the sizing mill; specifically: the guide grooves after the finishing mill and the sizing mill are empty (such as Figure 1 (As shown) industrial nitrogen gas sealing is adopted, and a nitrogen input pipeline is connected to one side of the entrance end of each section of the guide groove. Nitrogen is input when the rolled material passes through, and the pressure is about 0.3MPa, which effectively reduces the generation of iron oxide scale.

[0031] (3) By controlling the spinning temperature, the rate of iron oxide scale generation on the air cooling line is reduced; specifically: the spinning temperature is 820°C to 840°C.

[0032] (4) Control the cooling speed of the fan to quickly cross the temperature range of iron oxide generation; specifically, the air volume of a single cooling fan of the post-spinning air-cooling line is greater than 200,000 cubic meters per hour, 7 fans are used for the wire diameter of 5.5 mm, 8 fans are used for the wire diameter of 6.5 mm, and 9 fans are used for the wire diameter of 7 mm. The larger the specification, the more fans are needed. The specific fan air volume is shown in Table 2 below:

[0033] Table 2 Fan air volume of Example 2

[0034]

[0035] The wire rod produced by the process of Example 2 was tested and the thickness was measured at points divided by 120° on the circumference of the cross section of the wire rod. The arithmetic average thickness of the oxide scale at the three points was about 1.5 μm.

[0036] Example 3

[0037] (1) By controlling the rolling temperature of the finishing mill and the final rolling temperature of the reducing and sizing mill, the generation of iron oxide scale in the production process is reduced; specifically: the outlet temperature of the finishing mill is controlled below 950°C, and the final rolling temperature of the reducing and sizing mill is controlled below 900°C; when the manganese content is ≥0.6wt.% or the chromium content is ≥0.25wt.%, the outlet temperature of the finishing mill is controlled below 970°C, and the final rolling temperature of the reducing and sizing mill is controlled below 920°C. The cooling water volume between the frames of the finishing mill and the reducing and sizing mill is increased by 30%, and the pressure is controlled at 0.3-0.35MPa.

[0038] (2) Reduce the oxidation of wire rods at high temperatures by sealing the guide grooves after the finishing mill and the sizing mill; specifically: the guide grooves after the finishing mill and the sizing mill are empty (such as Figure 1 (As shown) industrial nitrogen gas sealing is adopted, and a nitrogen input pipeline is connected to one side of the entrance end of each section of the guide groove. Nitrogen is input when the rolled material passes through, and the pressure is about 0.3MPa, which effectively reduces the generation of iron oxide scale.

[0039] (3) By controlling the spinning temperature, the rate of formation of iron oxide scale on the air cooling line is reduced; specifically: the spinning temperature is 800°C to 820°C.

[0040] (4) Control the cooling speed of the fan to quickly cross the temperature range of iron oxide generation; specifically, the air volume of a single cooling fan of the post-spinning air-cooling line is greater than 200,000 cubic meters per hour, 7 fans are used for the wire diameter of 5.5 mm, 8 fans are used for the wire diameter of 6.5 mm, and 9 fans are used for the wire diameter of 7 mm. The larger the specification, the more fans are needed. The specific fan air volume is shown in Table 3 below:

[0041] Table 3 Fan air volume of Example 3

[0042]

[0043] The wire rod produced by the process of Example 3 was tested and the thickness was measured at points divided by 120° on the circumference of the cross section of the wire rod. The arithmetic average thickness of the oxide scale at the three points was about 1.2 μm.

[0044] Comparative Example

[0045] (1) By controlling the rolling temperature of the finishing mill and the final rolling temperature of the reducing and sizing mill, the generation of iron oxide scale in the production process is reduced; specifically: the outlet temperature of the finishing mill is controlled below 950°C, and the final rolling temperature of the reducing and sizing mill is controlled below 890°C; when the manganese content is ≥0.6wt.% or the chromium content is ≥0.25wt.%, the outlet temperature of the finishing mill is controlled below 950°C, and the final rolling temperature of the reducing and sizing mill is controlled below 890°C. The cooling water volume between the frames of the finishing mill and the reducing and sizing mill is 350 cubic meters / hour, and the pressure is controlled at 0.2-0.25MPa.

[0046] (2) The rear guide grooves of the finishing mill and the sizing mill are not sealed with air, and the steel is passed in the ordinary way.

[0047] (3) Control the spinning temperature to 870℃~890℃.

[0048] (4) Fan air volume control setting; Specifically, the air volume of a single cooling fan of the post-spinning air cooling line is less than 200,000 cubic meters per hour. The wire diameter of 5.5 mm uses 7 fans, the wire diameter of 6.5 mm uses 8 fans, and the wire diameter of 7 mm uses 9 fans. The larger the specification, the more fans are needed. The specific fan air volume is shown in Table 4 below:

[0049] Table 4 Fan air volume of the comparative example

[0050]

[0051] The wire rod produced by the comparative process was tested and the thickness was measured at 120° points on the circumference of the wire rod cross section. The arithmetic average thickness of the oxide scale at the three points was about 6.5μm.

[0052] The above examples and comparative examples show that the control method of the present invention can successfully control the thickness of the iron oxide scale to a thickness not exceeding 2 μm.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method for high-speed hot-rolled wire rod with an average oxide scale thickness of ≤ 2 μm, characterized in that: The following steps are involved: (1) Reduce the generation of iron oxide scale during the production process by controlling the rolling temperature of the finishing mill and the final rolling temperature of the sizing mill; (2) Reduce oxidation of wire rods at high temperatures by sealing the guide grooves after the finishing mill and the sizing mill; (3) By controlling the spinning temperature, the production rate of iron oxide scale on the air cooling line is reduced; (4) Control the cooling speed of the fan to quickly cross the temperature range of iron oxide production.

2. The control method for high-speed hot-rolled wire rod with an average oxide scale thickness of ≤ 2 μm according to claim 1, characterized in that: The outlet temperature of the finishing mill is controlled below 950°C, and the final rolling temperature of the sizing mill is controlled below 900°C; when the manganese content is ≥0.6 wt.% or the chromium content is ≥0.25 wt.%, the outlet temperature of the finishing mill is controlled below 970°C, and the final rolling temperature of the sizing mill is controlled below 920°C.

3. The control method for high-speed hot-rolled wire rod with an average oxide scale thickness of ≤ 2 μm according to claim 1, characterized in that: The cooling water volume between the finishing mill and the sizing mill frames is increased by 30%, and the pressure is controlled at 0.3-0.35MPa.

4. The control method for high-speed hot-rolled wire rod with an average oxide scale thickness of ≤ 2 μm according to claim 1, characterized in that: The finishing mill and the guide groove after sizing are sealed with industrial nitrogen.

5. The control method for high-speed hot-rolled wire rod with an average oxide scale thickness of ≤ 2 μm according to claim 1, characterized in that: The spinning temperature is 800℃~850℃.

6. The control method for high-speed hot-rolled wire rod with an average oxide scale thickness of ≤ 2 μm according to claim 1, characterized in that: The air volume of a single cooling fan on the post-spinning air cooling line is greater than 200,000 cubic meters per hour, and the number of fans is determined according to the wire diameter specifications.

Images