Method for smelting production and rolling structure regulation and control of medium carbon steel easy to draw

Abstract

The invention discloses an easy-to-draw medium carbon steel smelting production and rolling structure regulation and control method, which comprises the following steps of: in a steelmaking process, firstly ensuring that a molten iron time sequence is normal, and avoiding the time sequence is late due to iron waiting; the desulfurization rate is guaranteed, and the sulfur content of molten iron entering the furnace is required to be smaller than 0.020%; during refining, normal argon blowing in the whole process must be guaranteed according to operation regulations, and a refining slag system is an aluminum-free slag system; rolling, wherein the rolling process parameters and the Stelmor roller way speed are determined according to the carbon content in the steel; the technical regulation of heating operation is strictly executed, residual oxygen is controlled to be below 4%, cooling is conducted in time when rolling is stopped, rolling line accidents are reduced, and the in-furnace time is prevented from being too long; finishing head and tail non-cold sections, and trimming defect parts; two finished wire rods are rolled in different times in each furnace through pickling, cracks, scabs and folding surface defects which are visible to naked eyes are avoided after pickling, and if yes, the wire rods are modified. The invention aims to enable the produced medium carbon steel wire rod to meet the drawing use requirement and ensure that the drawing process of a user is smooth at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of metal smelting and rolling, and in particular relates to a method for smelting and producing medium carbon steel that is easy to draw and for regulating and controlling rolling structure. Background Art

[0002] Medium carbon steel wire rod is commonly used in drawing processing to produce prestressed steel wire, carbon spring steel wire, high-strength high-quality carbon structural steel wire, oil quenched and tempered carbon spring steel wire, galvanized steel wire, galvanized stranded wire rope, etc. It has good tensile strength and plasticity. It is a high value-added wire product with broad application prospects. In the preparation and application process of medium carbon steel drawing materials, many aspects need to be paid attention to to ensure that its quality and performance meet the requirements of use. The purpose of this patent is to provide a method for smelting and producing medium carbon steel wire rods that are easy to draw and for regulating the rolling structure to meet the requirements of drawing and use, while ensuring that the user's drawing process is smooth. Summary of the invention

[0003] The purpose of the present invention is to provide a method for smelting and producing medium carbon steel that is easy to draw and for regulating and controlling rolling structure, which meets the requirements for drawing use and ensures that the drawing process of the user proceeds smoothly.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention discloses a method for smelting and producing medium carbon steel that is easy to draw and for controlling rolling structure, comprising:

[0006] 1) Steelmaking process

[0007] Steelmaking must first ensure that the timing of molten iron is normal to avoid delays due to waiting for iron; ensure the desulfurization rate, and the sulfur content of molten iron entering the furnace is required to be less than 0.020%; strictly control the smelting charge to 100±2 tons, stabilize the steel output, ensure clearance, and ensure stable in-situ composition; in order to ensure the stability of the carbon composition for refining and avoid over-oxidation steel, adopt high-pull supplementary blowing operation, and pull carbon 0.20≤C≤0.35; if the final slag is thin, the slag can be appropriately thickened; before steel tapping, the clay plug must be blocked and the slag must be blocked to reduce the amount of slag. If the slag blocking fails, the slag must be removed to ensure the supply of refined steel. Stability of composition; endpoint control target: C ≥ 0.08%, T ≥ 1630℃; top slag technology is used for steel tapping, and the top slag addition requirements are: 190-210kg of small-grained lime and 90-110kg of fluorite; when tapping, strengthen contact with tank repairers and perform argon blowing operations according to regulations; argon control requirements: large argon stirring in the early stage of steel tapping, and when the steel tapping volume is greater than 2 / 3, the argon flow rate is reduced to perform slag blocking operations to ensure the melting of the top slag material; manganese iron deoxidation and alloying are used, and aluminum-free deoxidation is used for final deoxidation, and the deoxidizer addition amount is 3-3.3kg / ton of steel;

[0008] According to the operating procedures, the refining process must ensure normal argon blowing throughout the whole process, and the refining slag system is aluminum-free; slag desulfurization and heating operations are carried out according to the composition and temperature of the incoming molten steel. The refining furnace strictly implements slag heating and composition fine-tuning, and disorderly heating and disorderly argon blowing are strictly prohibited; refining must ensure that the white slag time is greater than or equal to 20 minutes, and a slag sample is taken before leaving the site. The main process parameters of the continuous casting process are controlled as follows:

[0009] Temperature control Molten steel superheat in tundish℃ Pulling speed m / min First furnace pouring ≤45 1.5 Process temperature control range ≤30 1.9～2.1 Process temperature control target 25～30 2.0

[0010] Before the first ladle is poured, fill the middle ladle with argon for 3-5 minutes to displace the air and reduce the oxidation of molten steel. During the entire casting process, the pouring must be protected and the long nozzle must be blown with argon. The middle ladle nozzle uses the Shandong Zibo immersion nozzle. Pay close attention to the nozzle quality during production and keep records; when the middle ladle is filled with 12 tons of molten steel, add the covering agent first, and then add carbonized rice husks for insulation when the ladle is full. The protective slag uses 82B special protective slag; when the large ladle is poured with 110t of molten steel in a tank, calibrate the temperature or adjust it according to the actual situation of continuous measurement, and contact the refining in time to adjust the upper steel temperature of each furnace of steel; the target superheat is required to be controlled at ≤30℃, and the target constant pulling speed is 2.0m / min, and the pulling speed control range is ±0.1m / min; the electric stirring of the crystallizer uses 3.5Hz, 200A; the final stirring uses 8.0Hz, 260A; during the pouring process, pay close attention to the surface quality of the ingot, and shut down the flow in time if abnormal problems are found;

[0011] During the production process, each ingot is numbered. After the ingot is off the production line, it is placed in a slow cooling pile for 36 hours. The target temperature in the slow cooling pit is above 450℃. After slow cooling, it is sent to the wire rod mill for rolling.

[0012] 2) Rolling

[0013] Before rolling, the long product mill checks the surface quality of the ingots and selects the ingots with surface defects; during rolling, high-pressure water descaling is started to ensure that the working pressure of the descaling water and the smooth flow of the nozzles are guaranteed, and the pressure is ≥7MPa to ensure that all the iron oxide scale on the surface of the steel billet is removed; the rolling process parameters and the Stelmor roller speed depend on the carbon content in the steel;

[0014] Strictly implement the technical regulations for heating operations to ensure that the residual oxygen is controlled below 4%, cool down in time when rolling is stopped, reduce rolling line accidents, and prevent the steel from being in the furnace for too long. Trim the uncooled sections at the head and tail of the finishing, and trim the defective parts. Pickle 2 finished wire rods from different coils in each furnace. After pickling, there shall be no cracks, scars, or folding surface defects visible to the naked eye. If there are any, the wire rods shall be re-judged.

[0015] Furthermore, the top slag addition requirements are: 200kg of small-grained lime and 100kg of fluorite.

[0016] Furthermore, the amount of deoxidizer added is 3.16 kg / ton of steel.

[0017] Furthermore, during production, we must frequently observe abnormal leakage and cracks in the sprue of the middle package, and if any ingots are found to be on the crack line of the sprue, all the ingots will fall behind.

[0018] Furthermore, the average superheat of a normal pouring furnace exceeds 40°C and is left behind; the ingots with large liquid level fluctuations and flocculent flow are picked out and left behind.

[0019] Furthermore, the maximum pulling speed is not allowed to exceed 2.1m / min. If the pulling speed exceeds 2.1m / min, encrypted sampling will be carried out for each stream, and if the pulling speed exceeds 2.3m / min, the ingot will be left behind.

[0020] Furthermore, its chemical composition in mass percentage is: C: 0.40-0.60%, Si: 0.17-0.37%, Mn: 0.50-0.70%, P: ≤0.020%, S≤0.015%, N≤0.0050%, and the rest is Fe and impurities. At the same time, the residual elements are required to be controlled: Cr≤0.20%, Ni≤0.20%, Cu≤0.20%.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are:

[0022] The medium carbon steel wire rod produced by the present invention meets the drawing use requirements and ensures that the user's drawing process proceeds smoothly.

[0023] After the implementation of the present invention, users can draw wires from Φ6.5mm to about Φ2.0 without any breakage, the drawing is smooth, and the wire breakage rate is significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] Figure 1 This is a schematic diagram of sampling after pickling;

[0026] Figure 2 Schematic diagram of the wire rod microstructure of the present invention. DETAILED DESCRIPTION

[0027] A method for smelting and producing medium carbon steel that is easy to draw and for controlling rolling structure, comprising:

[0028] Steelmaking controls the timing while ensuring the desulfurization rate. The sulfur content of the molten iron entering the furnace is required to be less than 0.020%. End point control target: C ≥ 0.08%, T ≥ 1630℃. Manganese iron is used for deoxidation and alloying, and aluminum-free deoxidation is used for final deoxidation. The amount of deoxidizer added is 3.16kg / ton of steel. According to the operating procedures, refining must ensure normal argon blowing throughout the process, and the refining slag system is an aluminum-free slag system (the slag material is lime, fluorite, and calcium carbide). Slag desulfurization and heating operations are carried out according to the composition and temperature of the molten steel of the incoming steel. The refining furnace strictly implements slag heating and composition fine-tuning. Disordered heating and disordered argon blowing are strictly prohibited. Refining must ensure that the white slag time is greater than or equal to 20 minutes, and a slag sample is taken before leaving the site. The refining component control is shown in Table 1, taking 45 steel as an example.

[0029] Table 1 Refining control composition requirements / %

[0030]

[0031] During rolling, high-pressure water descaling is turned on to ensure the working pressure of the descaling water and the smooth flow of the nozzle. The pressure is ≥7MPa to ensure that all the iron oxide scale on the surface of the billet is removed. In order to ensure the troostitization rate of the obtained structure, the following process parameters should be followed.

[0032] Table 2 Rolling process parameter settings

[0033]

[0034] The sample pickling did not show any surface defects such as cracks, scars, folds, etc. Figure 1 The wire rod was taken for microstructure analysis, as shown in Figure 2 shown.

[0035] After the method of the present invention is implemented, the user can draw the wire from Φ6.5mm to about Φ2.0 without any breakage, the drawing is smooth, and the wire breakage rate is significantly reduced.

[0036] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for smelting and producing medium carbon steel that is easy to draw and for controlling rolling structure, characterized in that: include: 1) Steelmaking process Steelmaking must first ensure that the timing of molten iron is normal to avoid delays due to waiting for iron; ensure the desulfurization rate, and the sulfur content of molten iron entering the furnace is required to be less than 0.020%; strictly control the smelting charge to 100±2 tons, stabilize the steel output, ensure clearance, and ensure stable in-situ composition; in order to ensure the stability of the carbon composition for refining and avoid over-oxidation steel, adopt high-pull supplementary blowing operation, and pull carbon 0.20≤C≤0.35; if the final slag is thin, the slag can be appropriately thickened; before steel tapping, the clay plug must be blocked and the slag must be blocked to reduce the amount of slag. If the slag blocking fails, the slag must be removed to ensure the supply of refined steel. Stability of composition; endpoint control target: C ≥ 0.08%, T ≥ 1630℃; top slag technology is used for steel tapping, and the top slag addition requirements are: 190-210kg of small-grained lime and 90-110kg of fluorite; when tapping, strengthen contact with tank repairers and perform argon blowing operations according to regulations; argon control requirements: large argon stirring in the early stage of steel tapping, and when the steel tapping volume is greater than 2 / 3, the argon flow rate is reduced to perform slag blocking operations to ensure the melting of the top slag material; manganese iron deoxidation and alloying are used, and aluminum-free deoxidation is used for final deoxidation, and the deoxidizer addition amount is 3-3.3kg / ton of steel; According to the operating procedures, the refining process must ensure normal argon blowing throughout the whole process, and the refining slag system is aluminum-free slag system; slag making, desulfurization and heating operations are carried out according to the composition and temperature of the incoming molten steel. The refining furnace strictly implements slag heating and composition fine-tuning, and disorderly heating and disorderly argon blowing are strictly prohibited; refining must ensure that the white slag time is greater than or equal to 20 minutes, and a slag sample is taken before leaving the site; the main process parameters of the continuous casting process are controlled as shown in the following table: Before the first ladle is poured, argon is filled into the middle ladle for 3-5 minutes to displace the air and reduce the oxidation of molten steel. During the entire casting process, the pouring must be protected and argon must be blown through the long nozzle. The middle ladle nozzle uses the Shandong Zibo immersion nozzle. During the production process, pay close attention to the nozzle quality and keep records. When the molten steel in the middle ladle reaches 12 tons, add the covering agent first, and then add carbonized rice husk for insulation when the ladle is full. The protective slag uses 82B special protective slag. When the large ladle pours 110t of molten steel with a tank, calibrate the temperature or adjust it according to the actual situation of continuous measurement. Contact the refining in time to adjust the upper steel temperature of each furnace of steel. The target superheat is required to be controlled at ≤30℃, and the target constant pulling speed is 2.0m / min, with a pulling speed control range of ±0.1m / min. The electric stirring of the crystallizer adopts 3.5Hz and 200A; the final stirring adopts 8.0Hz and 260A. During the pouring process, pay close attention to the surface quality of the ingot, and shut down the flow in time if any abnormal problems are found. During the production process, each ingot is numbered. After the ingot is off the production line, it is placed in a slow cooling pile for 36 hours. The target temperature in the slow cooling pit is above 450℃. After slow cooling, it is sent to the wire rod mill for rolling. 2) Rolling Before rolling, the long product mill checks the surface quality of the ingots and selects the ingots with surface defects; during rolling, high-pressure water descaling is started to ensure that the working pressure of the descaling water and the smooth flow of the nozzles are guaranteed, and the pressure is ≥7MPa to ensure that all the iron oxide scale on the surface of the steel billet is removed; the rolling process parameters and the Stelmor roller speed depend on the carbon content in the steel; Strictly implement the technical regulations for heating operations to ensure that the residual oxygen is controlled below 4%, cool down in time when rolling is stopped, reduce rolling line accidents, and prevent the steel from being in the furnace for too long. Trim the uncooled sections at the head and tail of the finishing, and trim the defective parts. Pickle 2 finished wire rods from different coils in each furnace. After pickling, there shall be no cracks, scars, or folding surface defects visible to the naked eye. If there are any, the wire rods shall be re-judged.

2. The method for smelting and producing medium carbon steel that is easy to draw and for controlling rolling structure according to claim 1, characterized in that: The top slag addition requirements are: 200kg of small-grained lime and 100kg of fluorite.

3. The method for smelting and producing medium carbon steel that is easy to draw and for controlling rolling structure according to claim 1, characterized in that: The amount of deoxidizer added is 3.16kg / ton of steel.

4. The method for smelting and producing medium carbon steel that is easy to draw and for controlling rolling structure according to claim 1, characterized in that: During production, we must frequently observe any leakage or cracks in the sprue nozzle of the middle package, and if any cracks are found, all the ingots will fall behind.

5. The method for smelting and producing medium carbon steel that is easy to draw and for controlling rolling structure according to claim 1, characterized in that: The average superheat of a normal pouring furnace exceeds 40℃ and is left behind; the ingots with large liquid level fluctuations and flocculence are picked out and left behind.

6. The method for smelting and producing medium carbon steel that is easy to draw and for controlling rolling structure according to claim 1, characterized in that: The maximum pulling speed is not allowed to exceed 2.1m / min. If the pulling speed exceeds 2.1m / min, the sampling of each stream will be intensified. If the pulling speed exceeds 2.3m / min, the ingot will be left behind.

7. The method for smelting and producing medium carbon steel that is easy to draw and for controlling rolling structure according to claim 1, characterized in that: Its chemical composition by mass percentage is: C: 0.40-0.60%, Si: 0.17-0.37%, Mn: 0.50-0.70%, P: ≤0.020%, S≤0.015%, N≤0.0050%, and the rest is Fe and impurities. At the same time, the residual elements are required to be controlled: Cr≤0.20%, Ni≤0.20%, Cu≤0.20%.

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