Method for controlling thickness and structure of oxide scale on surface of high-carbon 87B wire rod

Abstract

The invention discloses a control method for the thickness and structure of oxide scale on the surface of a high-carbon 87B wire rod, and relates to the technical field of metallurgy. Comprising the following steps that S1, the temperature of a high-carbon 87B wire rod passing through a first air cooling section and a second air cooling section of an air cooling line is controlled to be 700-650 DEG C after the high-carbon 87B wire rod goes out of the second air cooling section; s2, the temperature of the high-carbon 87B wire rod is controlled to be 650-600 DEG C after the high-carbon 87B wire rod passes through a third air cooling section and a fourth air cooling section of the air cooling line and goes out of the fourth air cooling section; s3, the temperature of the high-carbon 87B wire rod passing through the fifth air cooling section and the sixth air cooling section of the air cooling line is controlled to be 550-500 DEG C after the high-carbon 87B wire rod is discharged out of the sixth air cooling section; and S4, the temperature of the high-carbon 87B wire rod passing through the seventh air cooling section and the eighth air cooling section of the air cooling line is controlled to be lower than 400 DEG C after the high-carbon 87B wire rod goes out of the eighth air cooling section. The purpose of controlling the thickness and the structure of the oxide scale on the surface of the high-carbon 87B wire rod is achieved by spraying water mist on the stelmor air cooling line and controlling the cooling speed of different cooling sections on the stelmor air cooling line.

Description

Technical Field

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

[0002] High carbon steel wire rod is the main raw material for producing steel strands. After different drawing processes, high carbon steel wire rods are produced into steel strands of different specifications for users to use. In order to ensure the smooth progress of the drawing process, users need 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 iron oxide on the surface of the high carbon steel wire rod will reduce the bonding force between the phosphating film and the substrate, causing the phosphating film to fall off during the drawing process, and the wire rod substrate to directly contact the drawing die, increasing the drawing resistance, affecting the surface quality of the wire drawing, and even causing the drawing to break. Therefore, it is necessary to remove the iron oxide on the surface of the high carbon steel wire rod as much as possible before the phosphating treatment of the wire rod to form a relatively stable and uniform surface state, thereby ensuring a good phosphating effect.

[0003] The structure of the iron oxide scale of high carbon steel wire rod is generally two layers: the inner FeO layer and the outer Fe3O4 layer. FeO is relatively loose and easy to remove by pickling, while Fe3O4 is relatively dense and difficult to remove during the pickling process. Moreover, Fe3O4 is distributed in the outer layer of the oxide layer. After the reaction with the acid is completed, the inner FeO may continue to react with the acid, which will affect the speed of the pickling process. Reducing the Fe3O4 content in the iron oxide scale of high carbon steel wire rod or destroying the continuity of the outer Fe3O4 layer is conducive to improving the pickling rate and effect. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a method for controlling the thickness and structure of the iron oxide scale on the surface of high-carbon 87B wire rod, by spraying water mist on the Stelmore air-cooling line, the iron oxide scale on the surface of the wire rod will be broken after the water droplets contact the red-hot wire rod, and point-distributed cavities will be formed on the surface of the iron oxide scale. The water droplets are gasified to produce water vapor, which reduces the partial pressure of oxygen in the surrounding cooling gas, realizes the reduction of the oxygen content in the cooling medium on the Stelmore air-cooling line, reduces the oxygen supply capacity of the cooling medium to the iron oxide scale at high temperature, reduces the oxygen content in the high-temperature iron oxide scale, reduces the content of difficult-to-pickling Fe3O4 in the surface iron oxide scale layer, and at the same time controls the cooling rate of different cooling sections on the air-cooling line to avoid the preferential nucleation of pro-eutectoid Fe3O4, and reduces the content of island-shaped pro-eutectoid Fe3O4 inside the iron oxide scale, thereby controlling the thickness and structure of the iron oxide scale.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows: A method for controlling the thickness and structure of iron oxide scale on the surface of a high carbon 87B wire rod comprises the following steps: S1, high carbon 87B wire rod passes through the 1st and 2nd air cooling sections of the air cooling line, and the air volume of the fan is controlled to 18000-20000m 3 / h, spraying atomized water into the air duct through the aerosol nozzles installed on both sides of the air cooling section, using the air blown by the fan and the atomized water to form a mixed medium to cool the high carbon 87B wire rod, and controlling the temperature of the high carbon 87B wire rod after the second air cooling section to be 700-650°C, wherein 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%, and the air cooling line is a Stelmore air cooling line with a water spray system; S2, high carbon 87B wire rod passes through the 3rd and 4th air cooling sections of the air cooling line, and the fan air volume is controlled to 15000-16000m 3 / h, spray atomized water into the air duct through the aerosol nozzles installed on both sides of the air cooling section, use the air blown in by the fan and the atomized water to form a mixed medium to cool the high carbon 87B wire rod, and control the temperature of the high carbon 87B wire rod after the 4th air cooling section to be 650-600℃; S3, high carbon 87B wire rod passes through the 5th and 6th air cooling sections of the air cooling line, and the air volume of the fan is controlled to 15000-16000m 3 / h, spray atomized water into the air duct through the aerosol nozzles installed on both sides of the air cooling section, use the air blown in by the fan and the atomized water to form a mixed medium to cool the high carbon 87B wire rod, and control the temperature of the high carbon 87B wire rod after the 6th air cooling section to be 550-500℃; S4, high carbon 87B wire rod passes through the 7th and 8th air cooling sections of the air cooling line, without water spraying, and the fan air volume is controlled at 10000-15000m 3 / h, and the temperature of the high carbon 87B wire rod after the 8th air cooling stage is controlled to be below 400℃.

[0006] Furthermore, the preparation process of the high carbon 87B wire rod is as follows: A. Put the steel billet into the heating furnace for heating at a temperature of 880-1080°C for a heating time of 75-95 minutes; B. Dephosphorize the heated steel billet with high-pressure water. The pressure of the high-pressure water is controlled at 17-20Mpa. The iron oxide scale on the surface of the steel billet is removed before rolling. C. Rolling includes rough rolling and finish rolling, wherein the rough rolling temperature is 900-920°C, the finish rolling temperature is 890-910°C, the spinning temperature is 870-890°C, and finally high carbon 87B wire rod is produced.

[0007] Furthermore, the diameter of the high carbon 87B wire rod is 12-14 mm.

[0008] Furthermore, the medium used by the air mist nozzles on both sides of the air cooling section is compressed air and water, wherein: the working air pressure is 0.1-0.3MPa; the water pressure is 0.2-0.5Mpa; the gas flow rate is 2-5m 3 / h; water flow rate is 100-400L / h.

[0009] Furthermore, the steel billet specifications are 150×150×12000mm 3 -160×160×12000mm 3 Square billet.

[0010] 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 10-13um is obtained by the above method, the iron oxide scale is mainly composed of FeO, and point-distributed cavities are formed on the surface of the iron oxide scale, which destroys the continuity of the Fe3O4 layer on the wire rod surface, making it easier for the acid to react with the FeO in the inner layer. At the same time, due to the reduction of the oxygen content in the cooling medium and the control of the cooling rate, the amount of Fe3O4 generated in the iron oxide scale on the wire rod surface during the phase change process is reduced, and the content of Fe3O4 in the iron oxide scale on the wire rod surface is reduced, thereby controlling the thickness and structure of the iron oxide scale, accelerating the dissolution of the iron oxide scale on the wire rod surface, accelerating the pickling speed of the iron oxide scale, and reducing the acid consumption in the pickling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of iron oxide scale on the surface of high carbon 87B wire rod of comparative example; Figure 2 Schematic diagram of iron scale on the surface of high carbon 87B wire rod obtained in Example 1 of the present invention; Figure 3 Schematic diagram of iron scale on the surface of high carbon 87B wire rod obtained in Example 2 of the present invention; Figure 4 It is a schematic diagram of the iron oxide scale on the surface of the high carbon 87B wire rod obtained in Example 3 of the present invention. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0013] Embodiment 1, A method for controlling the thickness and structure of iron oxide scale on the surface of a high carbon 87B wire rod comprises the following steps: The chemical composition is C: 0.87%, Si: 0.25%, Mn: 0.75%, P: 0.010%, S: 0.007%, and the specifications are 150×150×12000mm 3 The steel billet is put into a heating furnace for heating at a temperature of 880°C for 75 minutes. The heated steel billet is dephosphorized by high-pressure water, and the pressure of the high-pressure water is controlled at 17Mpa. After the iron oxide scale on the surface of the steel billet is cleaned, it is rolled. The rough rolling temperature is 900°C, the finishing rolling temperature is 890°C, and the wire-spinning temperature is 870°C. Finally, a high-carbon 87B wire rod with a diameter of 12mm is made. The made high-carbon 87B wire rod is sent to the Stelmore air cooling line with a water spray nozzle for cooling. Atomized water is sprayed in each cooling section. The working air pressure of the spray nozzles installed on both sides of the air cooling section is 0.1MPa; the water pressure is 0.2Mpa; the gas flow rate is 2m 3 / h; water flow rate is 100L / h; S1, high carbon 87B wire rod passes through the 1st and 2nd air cooling sections of the air cooling line, and uses the aerosol nozzles set on both sides of the air cooling section to spray atomized water to cool the high carbon 87B wire rod. The fan air volume is controlled to 18000m 3 / h, the temperature of high carbon 87B wire rod after the second air cooling stage is controlled to be 700℃; S2, high carbon 87B wire rod passes through the 3rd and 4th air cooling sections of the air cooling line, and the high carbon 87B wire rod is cooled by spraying atomized water through the aerosol nozzles arranged on both sides of the air cooling section, and the air volume of the fan is controlled to be 15000m3 / h, and the temperature of the high carbon 87B wire rod after the 4th air cooling section is controlled to be 650℃; S3, high carbon 87B wire rod passes through the 5th and 6th air cooling sections of the air cooling line, and the high carbon 87B wire rod is cooled by spraying atomized water through the aerosol nozzles set on both sides of the air cooling section. The air volume of the fan is controlled to 15000m 3 / h, the temperature of high carbon 87B wire rod after the 6th air cooling stage is controlled to be 550℃; S4, high carbon 87B wire rod passes through the 7th and 8th air cooling sections of the air cooling line without water spraying, and the fan air volume is controlled to 10000m 3 / h, and the temperature of the high carbon 87B wire rod after the 8th air cooling stage is controlled to be 380℃.

[0014] Figure 1 The morphology and structure of the iron oxide scale are shown in the comparative example. Figure 1 It can be seen that the iron oxide scale on the wire rod surface has a typical double-layer iron oxide scale structure. The outer iron oxide scale is a smooth, flat, continuous and uniform Fe3O4 layer, and 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 2The iron oxide structure on the surface of the wire rod obtained by the present invention is significantly different from that of the comparative example. The iron oxide structure on the surface of the high carbon 87B wire rod obtained by Example 1 of the present invention is not obvious, and the iron oxide layer on the outer surface is distributed in a zigzag discontinuous manner. The inner layer does not contain Fe3O4 island grains. The entire iron oxide layer is mainly composed of FeO, and the thickness of the iron oxide layer is 10-11 μm.

[0015] Example 2: A method for controlling the thickness and structure of iron oxide scale on the surface of a high carbon 87B wire rod comprises the following steps: The chemical composition is C: 0.92%, Si: 0.30%, Mn: 0.80%, P: 0.012%, S: 0.008%, and the specifications are 155×155×12000mm 3 The steel billet is put into a heating furnace for heating at a temperature of 980°C for 85 minutes. The heated steel billet is dephosphorized by high-pressure water, and the pressure of the high-pressure water is controlled at 18Mpa. After the iron oxide scale on the surface of the steel billet is cleaned, it is rolled. The rough rolling temperature is 910°C, the finishing rolling temperature is 900°C, and the wire-spinning temperature is 880°C. Finally, a high-carbon 87B wire rod with a diameter of 13mm is made. The made high-carbon 87B wire rod is sent to the Stelmore air cooling line with a water spray nozzle for cooling. Atomized water is sprayed in each cooling section. The working air pressure of the spray nozzles installed on both sides of the air cooling section is 0.2MPa; the water pressure is 0.3Mpa; the gas flow rate is 3m 3 / h; water flow rate is 250L / h; S1, high carbon 87B wire rod passes through the 1st and 2nd air cooling sections of the air cooling line, and uses the aerosol nozzles set on both sides of the air cooling section to spray atomized water to cool the high carbon 87B wire rod. The fan air volume is controlled to 19000m 3 / h, the temperature of high carbon 87B wire rod after the second air cooling stage is controlled to be 650℃; S2, high carbon 87B wire rod passes through the 3rd and 4th air cooling sections of the air cooling line, and the high carbon 87B wire rod is cooled by spraying atomized water through the aerosol nozzles set on both sides of the air cooling section. The air volume of the fan is controlled to 15500m 3 / h, the temperature of high carbon 87B wire rod after the 4th air cooling stage is controlled to be 600℃; S3, high carbon 87B wire rod passes through the 5th and 6th air cooling sections of the air cooling line, and the high carbon 87B wire rod is cooled by spraying atomized water through the aerosol nozzles set on both sides of the air cooling section. The air volume of the fan is controlled to 15500m 3 / h, the temperature of high carbon 87B wire rod after the sixth air cooling stage is controlled to be 500℃; S4, high carbon 87B wire rod passes through the 7th and 8th air cooling sections of the air cooling line, without water spraying, and the fan air volume is controlled to 12500m 3 / h, and the temperature of the high carbon 87B wire rod after the 8th air cooling stage is controlled to be 350℃.

[0016] Figure 1 The morphology and structure of the iron oxide scale are shown in the comparative example. Figure 1 It can be seen that the iron oxide scale on the wire rod surface has a typical double-layer iron oxide scale structure. The outer iron oxide scale is a smooth, flat, continuous and uniform Fe3O4 layer, and 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 structure on the surface of the wire rod obtained by the present invention is significantly different from that of the comparative example. The iron oxide structure on the surface of the high carbon 87B wire rod obtained by Example 2 of the present invention is not obvious, and the iron oxide layer on the outer surface is discontinuously distributed in a zigzag shape. The inner layer contains only individual Fe3O4 island grains. The entire iron oxide layer is mainly composed of FeO, and the thickness of the iron oxide layer is 10-13 μm.

[0017] Embodiment 3, A method for controlling the thickness and structure of iron oxide scale on the surface of a high carbon 87B wire rod comprises the following steps: The chemical composition is C: 0.86%, Si: 0.25%, Mn: 0.70%, P: 0.012%, S: 0.008%, and the specifications are 160×160×12000mm 3 The steel billet is placed in a heating furnace for heating at a temperature of 1080°C for 95 min. The heated steel billet is dephosphorized by high-pressure water, and the pressure of the high-pressure water is controlled at 20 MPa. After the iron oxide scale on the surface of the steel billet is cleaned, it is rolled. The rough rolling temperature is 920°C, the finishing rolling temperature is 910°C, and the spinning temperature is 890°C. Finally, a high-carbon 87B wire rod with a diameter of 14 mm is made, and the made high-carbon 87B wire rod is sent to the Stelmore air cooling line with a water spray nozzle for cooling. Atomized water is sprayed in each cooling section. The working air pressure of the spray nozzles installed on both sides of the air cooling section is 0.3 MPa; the water pressure is 0.5 MPa; the gas flow rate is 5 m 3 / h; water flow rate is 400L / h; S1, high carbon 87B wire rod passes through the 1st and 2nd air cooling sections of the air cooling line, and uses the aerosol nozzles set on both sides of the air cooling section to spray atomized water to cool the high carbon 87B wire rod, and the fan air volume is controlled to 20000m 3 / h, the temperature of high carbon 87B wire rod after the second air cooling stage is controlled to be 700℃; S2, high carbon 87B wire rod passes through the 3rd and 4th air cooling sections of the air cooling line, and the high carbon 87B wire rod is cooled by spraying atomized water through the aerosol nozzles set on both sides of the air cooling section. The air volume of the fan is controlled to 16000m 3 / h, the temperature of high carbon 87B wire rod after the 4th air cooling stage is controlled to be 630℃; S3, high carbon 87B wire rod passes through the 5th and 6th air cooling sections of the air cooling line, and the high carbon 87B wire rod is cooled by spraying atomized water through the aerosol nozzles set on both sides of the air cooling section. The air volume of the fan is controlled to 16000m 3 / h, the temperature of high carbon 87B wire rod after the 6th air cooling stage is controlled to be 525℃; S4, high carbon 87B wire rod passes through the 7th and 8th air cooling sections of the air cooling line, without water spraying, and the fan air volume is controlled to 15000m 3 / h, and the temperature of the high carbon 87B wire rod after the 8th air cooling stage is controlled to be 350℃.

[0018] Figure 1 The morphology and structure of the iron oxide scale are shown in the comparative example. 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 the iron oxide scale is a smooth, flat surface with continuous and uniform distribution of Fe3O4, and the inner layer is a mixed layer of Fe3O4 and FeO with a large number of island-like grains distributed, with a thickness of 14-15μm. Figure 4 The iron oxide structure on the surface of the wire rod obtained by the present invention is significantly different from that of the comparative example. The iron oxide structure on the surface of the high carbon 87B wire rod obtained by Example 3 of the present invention is not obvious, and the iron oxide layer on the outer surface is discontinuously distributed in a zigzag shape. The inner layer contains only individual Fe3O4 island grains. The entire iron oxide layer is mainly composed of FeO, and the thickness of the iron oxide layer is 10-12 μm.

[0019] 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 principle of the present invention should be included in 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: The following steps are involved: S1, high carbon 87B wire rod passes through the 1st and 2nd air cooling sections of the air cooling line, and the air volume of the fan is controlled to 18000-20000m 3 / h, spraying atomized water into the air duct through the aerosol nozzles installed on both sides of the air cooling section, using the air blown by the fan and the atomized water to form a mixed medium to cool the high carbon 87B wire rod, and controlling the temperature of the high carbon 87B wire rod after the second air cooling section to be 700-650°C, wherein 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%, and the air cooling line is a Stelmore air cooling line with a water spray system; S2, high carbon 87B wire rod passes through the 3rd and 4th air cooling sections of the air cooling line, and the air volume of the fan is controlled to 15000-16000m 3 / h, spray atomized water into the air duct through the aerosol nozzles installed on both sides of the air cooling section, use the air blown in by the fan and the atomized water to form a mixed medium to cool the high carbon 87B wire rod, and control the temperature of the high carbon 87B wire rod after the 4th air cooling section to be 650-600℃; S3, high carbon 87B wire rod passes through the 5th and 6th air cooling sections of the air cooling line, and the air volume of the fan is controlled to 15000-16000m 3 / h, spray atomized water into the air duct through the aerosol nozzles installed on both sides of the air cooling section, use the air blown in by the fan and the atomized water to form a mixed medium to cool the high carbon 87B wire rod, and control the temperature of the high carbon 87B wire rod after the 6th air cooling section to be 550-500℃; S4, high carbon 87B wire rod passes through the 7th and 8th air cooling sections of the air cooling line without water spraying, and the fan air volume is controlled at 10000-15000m 3 / h, and the temperature of the high carbon 87B wire rod after the 8th air cooling stage is controlled to be lower than 400℃.

2. The method for controlling the thickness and structure of the oxide scale on the surface of a 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 in a heating furnace for heating at a temperature of 880-1080°C for a heating time of 75-95 min; B. Dephosphorize the heated steel billet with high-pressure water. The pressure of the high-pressure water is controlled at 17-20Mpa. The iron oxide scale on the surface of the steel billet is removed before rolling. C. Rolling includes rough rolling and finish rolling, wherein the rough rolling temperature is 900-920°C, the finish rolling temperature is 890-910°C, the spinning temperature is 870-890°C, and finally high carbon 87B wire rod is produced.

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

4. The method for controlling the thickness and structure of the oxide scale on the surface of the high carbon 87B wire rod according to claim 1, characterized in that: The medium used by the air mist nozzles on both sides of the air cooling section is compressed air and water, among which: the working air pressure is 0.1-0.3MPa; the water pressure is 0.2-0.5Mpa; the gas flow rate is 2-5m 3 / h; water flow rate is 100-400L / h.

5. The method for controlling the thickness and structure of the oxide scale on the surface of the high carbon 87B wire rod according to claim 2, characterized in that: The billet specifications are 150×150×12000mm 3 -160×160×12000mm 3 Square billet.

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