Method for controlling the thickness and structure of the surface scale of high-carbon 87b wire rod

Abstract

The application discloses a high-carbon 87B wire rod surface oxide scale thickness and structure control method and relates to the technical field of metallurgy. The method comprises the following steps: S1, after the first and second air cooling sections of the air cooling line, the temperature of the high-carbon 87B wire rod after the second air cooling section is controlled to be 700-650 DEG C; S2, after the third and fourth air cooling sections of the air cooling line, the temperature of the high-carbon 87B wire rod after the fourth air cooling section is controlled to be 650-600 DEG C; S3, after the fifth and sixth air cooling sections of the air cooling line, the temperature of the high-carbon 87B wire rod after the sixth air cooling section is controlled to be 550-500 DEG C; and S4, after the seventh and eighth air cooling sections of the air cooling line, the temperature of the high-carbon 87B wire rod after the eighth air cooling section is controlled to be lower than 400 DEG C. Through the method of spraying water mist on the Stelmor air cooling line and controlling the cooling speed of different cooling sections on the Stelmor air cooling line, the purpose of controlling the high-carbon 87B wire rod surface oxide scale thickness and structure is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metallurgy, in particular to a method for controlling the thickness and structure of the surface oxide scale of high-carbon 87B wire rod. BACKGROUND

[0002] High-carbon steel wire rod is the main raw material for producing steel strand at present. After different drawing processes, high-carbon steel wire rod is produced into steel strand products of different specifications for users to use. In order to ensure the smooth progress of the drawing process, the user needs to perform a series of surface treatments on the surface of the high-carbon steel wire rod before drawing, so as to obtain a phosphating film with lubricating effect on the surface of the high-carbon steel wire rod. The presence of the surface oxide scale of the high-carbon steel wire rod will reduce the adhesion between the phosphating film and the substrate, resulting in the phosphating film falling off the substrate and directly contacting the drawing die during the drawing process, increasing the drawing resistance and affecting the drawing surface quality, and even leading to drawing fracture. Therefore, the surface oxide scale of the high-carbon steel wire rod needs to be removed as much as possible before phosphating treatment, so as to form a relatively stable and uniform surface state, thereby ensuring good phosphating effect.

[0003] The structure of the surface oxide scale of the high-carbon steel wire rod is generally two layers: an inner FeO layer and an outer Fe3O4 layer. FeO is relatively loose and easy to remove by pickling, while Fe3O4 is relatively dense and not easy to remove during pickling. Moreover, Fe3O4 is distributed in the outer layer of the oxide layer, and after the reaction of Fe3O4 with acid is completed, the inner FeO layer can continue to react with acid, which will affect the speed of the pickling process. Reducing the content of Fe3O4 in the surface oxide scale of the high-carbon steel wire rod or destroying the continuity of the outer Fe3O4 layer is conducive to improving the pickling rate and effect. SUMMARY

[0004] In view of the above technical problems, the present application provides a method for controlling the thickness and structure of the surface oxide scale of high-carbon 87B wire rod. Water mist is sprayed on the Stelmor air cooling line, and after the water droplets contact the red-hot wire rod, the surface oxide scale of the wire rod will be broken, and a large number of point-shaped distribution cavities will be formed on the surface of the oxide scale. Water droplets vaporize to produce water vapor, which reduces the oxygen partial pressure in the surrounding cooling gas, reduces the oxygen content in the cooling medium on the Stelmor air cooling line, reduces the oxygen supply capacity of the cooling medium to the oxide scale at high temperature, reduces the oxygen content in the high-temperature oxide scale, reduces the content of difficult-to-pickling Fe3O4 in the surface oxide scale layer, controls the cooling rate at different cooling stages on the air cooling line to avoid the preferential nucleation of proeutectoid Fe3O4, and reduces the content of island-shaped proeutectoid Fe3O4 in the oxide scale, thereby controlling the thickness and structure of the oxide scale.

[0005] In order to achieve the above purpose, the technical scheme of the present application is as follows:

[0006] A method for controlling the thickness and structure of the surface oxide scale of high-carbon 87B wire rod, comprising the following steps:

[0007] S1 high-carbon 87B wire rod passes through the first and second air-cooling sections of the air-cooling line, with the fan airflow controlled at 18,000-20,000 m³ / h. 3 / h, atomized water is sprayed into the air duct through aerosol nozzles installed on both sides of the air-cooling section. The air blown in by the fan and the atomized water form a mixed medium to cool the high carbon 87B wire rod. The temperature of the high carbon 87B wire rod after exiting the second air-cooling section is controlled at 700-650℃. The chemical composition of the high carbon 87B wire rod is: C: 0.85-0.92%, Si: 0.20-0.30%, Mn: 0.70-0.80%, P: ≤0.015%, S: ≤0.015%. The air-cooling line is a Stellmore air-cooling line with a water spray system.

[0008] S2 and high-carbon 87B wire rods pass through the 3rd and 4th air-cooling sections of the air-cooling line, with the fan airflow controlled at 15000-16000 m³ / h. 3 / h, atomized water is sprayed into the air duct through the atomizing nozzles installed on both sides of the air-cooling section. The air blown in by the fan and the atomized water form a mixed medium to cool the high carbon 87B wire rod. The temperature of the high carbon 87B wire rod after exiting the 4th air-cooling section is controlled to be 650-600℃.

[0009] S3 and high-carbon 87B wire rods pass through the 5th and 6th air-cooling sections of the air-cooling line, with the fan airflow controlled at 15000-16000 m³ / h. 3 / h, atomized water is sprayed into the air duct through the atomizing nozzles installed on both sides of the air-cooling section. The air blown in by the fan and the atomized water form a mixed medium to cool the high carbon 87B wire rod. The temperature of the high carbon 87B wire rod after exiting the 6th air-cooling section is controlled to be 550-500℃.

[0010] S4 and high-carbon 87B wire rods pass through the 7th and 8th air-cooling sections of the air-cooling line, without water spraying, with the fan airflow controlled at 10,000-15,000 m³ / h. 3 / h, control the temperature of the high-carbon 87B wire rod after the 8th air-cooling section to be below 400℃.

[0011] Furthermore, the preparation process of the high-carbon 87B wire rod is as follows:

[0012] A. Place the steel billet into a heating furnace and heat it at a temperature of 880-1080℃ for 75-95 minutes.

[0013] B. After heating, the steel billet is descaled by high-pressure water at a pressure of 17-20 MPa. The iron oxide scale on the surface of the steel billet is removed before rolling.

[0014] C. Rolling includes roughing and finishing. The roughing temperature is 900-920℃, the finishing temperature is 890-910℃, and the wire drawing temperature is 870-890℃, finally producing high carbon 87B wire rod.

[0015] Furthermore, the diameter of the high-carbon 87B wire rod is 12-14 mm.

[0016] Furthermore, the aerosol nozzles on both sides of the air-cooling section use compressed air and water as the medium, wherein: the working air pressure is 0.1-0.3 MPa; the water pressure is 0.2-0.5 MPa; and the gas flow rate is 2-5 m³ / h. 3 / h; water flow rate is 100-400L / h.

[0017] Furthermore, the billet dimensions are 150×150×12000mm. 3 -160×160×12000mm 3 Square steel billet.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: A high-carbon 87B wire rod iron oxide scale with a thickness of 10-13 μm is obtained through the above method. The iron oxide scale is mainly composed of FeO, and dot-shaped voids are formed on the surface of the iron oxide scale, which disrupts the continuity of the Fe3O4 layer on the surface of the wire rod, making it easier for acid to react with the inner FeO layer. At the same time, due to the reduction of oxygen content in the cooling medium and the control of cooling rate, the amount of Fe3O4 generated during the phase transformation process in the iron oxide scale on the surface of the wire rod is reduced, thus reducing the Fe3O4 content in the iron oxide scale on the surface of the wire rod. This controls the thickness and structure of the iron oxide scale, accelerates the dissolution of the iron oxide scale on the surface of the wire rod, speeds up the pickling of the iron oxide scale, and reduces the acid consumption in the pickling process. Attached Figure Description

[0019] Figure 1 A schematic diagram of the iron oxide scale on the surface of high-carbon 87B wire rod for comparison;

[0020] Figure 2 This is a schematic diagram of the iron oxide scale on the surface of the high-carbon 87B wire rod obtained in Embodiment 1 of the present invention;

[0021] Figure 3 This is a schematic diagram of the iron oxide scale on the surface of the high-carbon 87B wire rod obtained in Embodiment 2 of the present invention;

[0022] Figure 4 This is a schematic diagram of the iron oxide scale on the surface of the high-carbon 87B wire rod obtained in Embodiment 3 of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0024] Example 1

[0025] A method for controlling the thickness and structure of iron oxide scale on the surface of high-carbon 87B wire rod includes the following steps:

[0026] The chemical composition is C: 0.87%, Si: 0.25%, Mn: 0.75%, P: 0.010%, S: 0.007%, and the dimensions are 150×150×12000mm. 3 The steel billet is placed in a heating furnace and heated to 880℃ for 75 minutes. After heating, the billet is descaled using high-pressure water at a pressure controlled at 17 MPa. Once the iron oxide scale on the billet surface is removed, it is rolled at a roughing temperature of 900℃, a finishing temperature of 890℃, and a wire drawing temperature of 870℃, finally producing a 12mm diameter high-carbon 87B wire rod. This high-carbon 87B wire rod is then fed into a Stellmore air-cooling line equipped with spray nozzles for cooling. Atomized water is sprayed into each cooling section. The spray nozzles installed on both sides of the air-cooling section have a working air pressure of 0.1 MPa, a water pressure of 0.2 MPa, and a gas flow rate of 2 m³ / s. 3 / h; water flow rate is 100L / h;

[0027] S1, the high-carbon 87B wire rod passes through the first and second air-cooling sections of the air-cooling line. Atomized water is sprayed into the high-carbon 87B wire rod using atomized water nozzles located on both sides of the air-cooling section to cool it. The fan airflow is controlled at 18000 m³ / h. 3 / h, control the temperature of the high carbon 87B wire rod after the second air-cooling section to 700℃;

[0028] S2. The high carbon 87B wire rod passes through the 3rd and 4th air-cooling sections of the air-cooling line. Atomized water is sprayed into the high carbon 87B wire rod through the aerosol water nozzles set on both sides of the air-cooling section to cool the high carbon 87B wire rod. The air volume of the fan is controlled at 15000m3 / h, and the temperature of the high carbon 87B wire rod after exiting the 4th air-cooling section is controlled at 650℃.

[0029] S3 and high-carbon 87B wire rods pass through the 5th and 6th air-cooling sections of the air-cooling line. Atomized water is sprayed into the high-carbon 87B wire rods through atomized water nozzles located on both sides of the air-cooling section to cool them, with the fan airflow controlled at 15000 m³ / h. 3 / h, control the temperature of the high carbon 87B wire rod after the 6th air-cooling section to 550℃;

[0030] S4 and high-carbon 87B wire rods pass through the 7th and 8th air-cooling sections of the air-cooling line, without water spraying, and the fan airflow is controlled at 10,000 m³ / h. 3 / h, control the temperature of the high carbon 87B wire rod after the 8th air-cooling section to 380℃.

[0031] Figure 1 To compare the morphology and structure of iron oxide scale, by Figure 1 It can be seen that the iron oxide scale on the surface of the wire rod has a typical double-layer iron oxide scale structure. The outer layer of iron oxide scale is a smooth, flat, and continuously and uniformly distributed Fe3O4 layer, while the inner layer is a mixed layer of Fe3O4 and FeO with a large number of island-like grains, with a thickness of 14-15μm. Figure 2 The iron oxide scale structure on the surface of the wire rod obtained by this invention is significantly different from that of the comparative example. The iron oxide scale layer is not obvious, and the iron oxide scale on the outer surface is distributed in a serrated and discontinuous manner. The inner layer does not contain Fe3O4 island-like grains. The entire iron oxide scale layer is mainly composed of FeO, and the thickness of the iron oxide scale is 10-11 μm.

[0032] Example 2

[0033] A method for controlling the thickness and structure of iron oxide scale on the surface of high-carbon 87B wire rod includes the following steps:

[0034] The chemical composition is C: 0.92%, Si: 0.30%, Mn: 0.80%, P: 0.012%, S: 0.008%, and the dimensions are 155×155×12000mm. 3 The steel billet is placed in a heating furnace and heated to 980℃ for 85 minutes. After heating, the billet is descaled using high-pressure water at a pressure controlled at 18 MPa. Once the iron oxide scale on the billet surface is removed, it is rolled at a roughing temperature of 910℃, a finishing temperature of 900℃, and a wire drawing temperature of 880℃, finally producing a 13mm diameter high-carbon 87B wire rod. This high-carbon 87B wire rod is then fed into a Stellmore air-cooling line equipped with spray nozzles for cooling. Atomized water is sprayed into each cooling section. The spray nozzles installed on both sides of the air-cooling section have a working air pressure of 0.2 MPa, a water pressure of 0.3 MPa, and a gas flow rate of 3 m³ / h. 3 / h; water flow rate is 250L / h;

[0035] S1, the high-carbon 87B wire rod passes through the first and second air-cooling sections of the air-cooling line. Atomized water is sprayed into the high-carbon 87B wire rod using atomized water nozzles located on both sides of the air-cooling section to cool it. The fan airflow is controlled at 19000 m³ / h. 3 / h, control the temperature of the high carbon 87B wire rod after the second air-cooling section to 650℃;

[0036] S2 and high-carbon 87B wire rods pass through the 3rd and 4th air-cooling sections of the air-cooling line. Atomized water is sprayed into the high-carbon 87B wire rods through atomized water nozzles located on both sides of the air-cooling section to cool them. The fan airflow is controlled at 15500 m³ / h. 3 / h, control the temperature of the high carbon 87B wire rod after the fourth air-cooling section to 600℃;

[0037] S3 and high-carbon 87B wire rods pass through the 5th and 6th air-cooling sections of the air-cooling line. Atomized water is sprayed into the high-carbon 87B wire rods through atomized water nozzles located on both sides of the air-cooling section to cool them, with the fan airflow controlled at 15500 m³ / h. 3 / h, control the temperature of the high carbon 87B wire rod after the 6th air-cooling section to 500℃;

[0038] S4 and high-carbon 87B wire rods pass through the 7th and 8th air-cooling sections of the air-cooling line, without water spraying, and the fan airflow is controlled at 12500 m³ / h. 3 / h, control the temperature of the high carbon 87B wire rod after the 8th air-cooling section to 350℃.

[0039] Figure 1 To compare the morphology and structure of iron oxide scale, by Figure 1 It can be seen that the iron oxide scale on the surface of the wire rod has a typical double-layer iron oxide scale structure. The outer layer of iron oxide scale is a smooth, flat, and continuously and uniformly distributed Fe3O4 layer, while the inner layer is a mixed layer of Fe3O4 and FeO with a large number of island-like grains, with a thickness of 14-15μm. Figure 3 The iron oxide scale structure on the surface of the wire rod obtained by this invention is significantly different from that of the comparative example. The iron oxide scale layer is not obvious, and the iron oxide scale on the outer surface is distributed in a serrated and discontinuous manner. The inner layer contains only a few Fe3O4 island-like grains. The entire iron oxide scale layer is mainly composed of FeO, and the thickness of the iron oxide scale is 10-13 μm.

[0040] Example 3

[0041] A method for controlling the thickness and structure of iron oxide scale on the surface of high-carbon 87B wire rod includes the following steps:

[0042] The chemical composition is C: 0.86%, Si: 0.25%, Mn: 0.70%, P: 0.012%, S: 0.008%, and the dimensions are 160×160×12000mm. 3The steel billet is placed in a heating furnace and heated to 1080℃ for 95 minutes. After heating, the billet is descaled using high-pressure water at a pressure controlled at 20 MPa. Once the iron oxide scale on the billet surface is removed, it is rolled at a roughing temperature of 920℃, a finishing temperature of 910℃, and a wire drawing temperature of 890℃, finally producing a 14mm diameter high-carbon 87B wire rod. This high-carbon 87B wire rod is then fed into a Stellmore air-cooling line equipped with spray nozzles for cooling. Atomized water is sprayed into each cooling section. The spray nozzles installed on both sides of the air-cooling section have a working air pressure of 0.3 MPa, a water pressure of 0.5 MPa, and a gas flow rate of 5 m³ / s. 3 / h; water flow rate is 400L / h;

[0043] S1. The high-carbon 87B wire rod passes through the first and second air-cooling sections of the air-cooling line. Atomized water is sprayed into the high-carbon 87B wire rod using atomized water nozzles located on both sides of the air-cooling section to cool it. The fan airflow is controlled at 20,000 m³ / h. 3 / h, control the temperature of the high carbon 87B wire rod after the second air-cooling section to 700℃;

[0044] S2 and high-carbon 87B wire rods pass through the 3rd and 4th air-cooling sections of the air-cooling line. Atomized water is sprayed into the high-carbon 87B wire rods through atomized water nozzles located on both sides of the air-cooling section to cool them. The fan airflow is controlled at 16000 m³ / h. 3 / h, control the temperature of the high carbon 87B wire rod after the fourth air-cooling section to 630℃;

[0045] S3 and high-carbon 87B wire rods pass through the 5th and 6th air-cooling sections of the air-cooling line. Atomized water is sprayed into the high-carbon 87B wire rods through atomized water nozzles located on both sides of the air-cooling section to cool them, with the fan airflow controlled at 16000 m³ / h. 3 / h, control the temperature of the high carbon 87B wire rod after the 6th air-cooling section to 525℃;

[0046] S4 and high-carbon 87B wire rods pass through the 7th and 8th air-cooling sections of the air-cooling line, without water spraying, and the fan airflow is controlled at 15000 m³ / h. 3 / h, control the temperature of the high carbon 87B wire rod after the 8th air-cooling section to 350℃.

[0047] Figure 1 To compare the morphology and structure of iron oxide scale, by Figure 1 It can be seen that the iron oxide scale on the surface of the wire rod has a typical double-layer iron oxide scale structure. The outer layer of iron oxide scale is a smooth, straight, and continuously and uniformly distributed Fe3O4, while the inner layer is a mixed layer of Fe3O4 and FeO with a large number of island-like grains, with a thickness of 14-15μm. Figure 4The iron oxide scale structure on the surface of the wire rod obtained by this invention is significantly different from that of the comparative example. The iron oxide scale layer is not obvious, and the iron oxide scale on the outer surface is discontinuously distributed in a serrated pattern. The inner layer contains only a few Fe3O4 island-like grains. The entire iron oxide scale layer is mainly composed of FeO, and the thickness of the iron oxide scale is 10-12 μm.

[0048] 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, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling the thickness and structure of iron oxide scale on the surface of high-carbon 87B wire rod, characterized in that, Includes the following steps: S1 high-carbon 87B wire rod passes through the first and second air-cooling sections of the air-cooling line, with the fan airflow controlled at 18,000-20,000 m³ / h. 3 / h, atomized water is sprayed into the air duct through aerosol nozzles installed on both sides of the air-cooling section. The air blown in by the fan and the atomized water form a mixed medium to cool the high carbon 87B wire rod. The temperature of the high carbon 87B wire rod after exiting the second air-cooling section is controlled at 700-650℃. The chemical composition of the high carbon 87B wire rod is: C: 0.85-0.92%, Si: 0.20-0.30%, Mn: 0.70-0.80%, P: ≤0.015%, S: ≤0.015%. The air-cooling line is a Stellmore air-cooling line with a water spray system. S2 and high-carbon 87B wire rods pass through the 3rd and 4th air-cooling sections of the air-cooling line, with the fan airflow controlled at 15000-16000 m³ / h. 3 / h, atomized water is sprayed into the air duct through the atomizing nozzles installed on both sides of the air-cooling section. The air blown in by the fan and the atomized water form a mixed medium to cool the high carbon 87B wire rod. The temperature of the high carbon 87B wire rod after exiting the 4th air-cooling section is controlled to be 650-600℃. S3 and high-carbon 87B wire rods pass through the 5th and 6th air-cooling sections of the air-cooling line, with the fan airflow controlled at 15000-16000 m³ / h. 3 / h, atomized water is sprayed into the air duct through the atomizing nozzles installed on both sides of the air-cooling section. The air blown in by the fan and the atomized water form a mixed medium to cool the high carbon 87B wire rod. The temperature of the high carbon 87B wire rod after exiting the 6th air-cooling section is controlled to be 550-500℃. S4 and high-carbon 87B wire rods pass through the 7th and 8th air-cooling sections of the air-cooling line, without water spraying, with the fan airflow controlled at 10,000-15,000 m³ / h. 3 / h, control the temperature of the high carbon 87B wire rod after the 8th air-cooling section to be below 400℃; The aerosol nozzles on both sides of the air-cooling section use compressed air and water as the medium, wherein: the working air pressure is 0.1-0.3 MPa; the water pressure is 0.2-0.5 MPa; and the gas flow rate is 2-5 m³ / h. 3 / h; water flow rate is 100-400L / h.

2. The method for controlling the thickness and structure of the iron oxide scale on the surface of high-carbon 87B wire rod according to claim 1, characterized in that, The preparation process of the high-carbon 87B wire rod is as follows: A. Place the steel billet into a heating furnace and heat it at a temperature of 880-1080℃ for 75-95 minutes. B. After heating, the steel billet is descaled by high-pressure water at a pressure of 17-20 MPa. The iron oxide scale on the surface of the steel billet is removed before rolling. C. Rolling includes roughing and finishing. The roughing temperature is 900-920℃, the finishing temperature is 890-910℃, and the wire drawing temperature is 870-890℃, finally producing high carbon 87B wire rod.

3. The method for controlling the thickness and structure of iron oxide scale on the surface of high-carbon 87B wire rod according to claim 1, characterized in that: The diameter of the high-carbon 87B wire rod is 12-14mm.

4. The method for controlling the thickness and structure of iron oxide scale on the surface of high-carbon 87B wire rod according to claim 2, characterized in that: The billet specifications are square steel billets with dimensions of 150mm×150mm×12000mm-160mm×160mm×12000mm.

Images