CN111424210B - Hot-rolled wire rod for welding wire and production method thereof - Google Patents

Hot-rolled wire rod for welding wire and production method thereof Download PDF

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CN111424210B
CN111424210B CN202010242130.1A CN202010242130A CN111424210B CN 111424210 B CN111424210 B CN 111424210B CN 202010242130 A CN202010242130 A CN 202010242130A CN 111424210 B CN111424210 B CN 111424210B
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wire rod
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molten steel
hot
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CN111424210A (en
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麻晗
郭慧英
张宇
王纳
张亚运
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Institute Of Research Of Iron & Steel shagang jiangsu Province
Jiangsu Shagang Group Co Ltd
Zhangjiagang Rongsheng Special Steel Co Ltd
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Institute Of Research Of Iron & Steel shagang jiangsu Province
Jiangsu Shagang Group Co Ltd
Zhangjiagang Rongsheng Special Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/24—Selection of soldering or welding materials proper
    • B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
    • B23K35/3053—Fe as the principal constituent
    • B23K35/3073—Fe as the principal constituent with Mn as next major constituent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/40—Making wire or rods for soldering or welding
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Metal Rolling (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

The invention discloses a hot-rolled wire rod for welding wires and a production method thereof. The wire rod comprises the following chemical components in percentage by weight: C. 0.060-0.075%; 0.80-0.88% of Si; 1.40-1.48% of Mn; p is less than or equal to 0.013%, S is less than or equal to 0.010%, Ti is 0.005-0.020%, and the balance of Fe and inevitable impurities. The steel is prepared by a molten steel smelting process, a refining process, a casting process, a heating process, a temperature-controlled rolling process and a stelmor slow cooling process which are sequentially carried out, wherein the temperature-controlled rolling process comprises the following steps: descaling a steel billet by high-pressure water, rolling the steel billet into a wire rod, wherein the inlet temperature of a finishing mill is less than or equal to 880 ℃, advancing the wire rod on a production line for at least 50m after finishing rolling, then performing water cooling, and spinning after cooling, wherein the spinning temperature is 880-910 ℃; the stelmor slow cooling process comprises the following steps: and (3) carrying out heat preservation and slow cooling on the wire rod on a stelmor slow cooling line, closing a heat preservation cover and a draught fan air port, and enabling the cooling speed of the wire rod in a phase change temperature range to be less than or equal to 0.8 ℃/s. The structure, the strength and the plasticity of the wire rod are uniform, the strength difference of the poker is less than or equal to 25MPa, and the wire rod is more suitable for high-speed drawing.

Description

Hot-rolled wire rod for welding wire and production method thereof
Technical Field
The invention belongs to the field of steel material production, and particularly relates to a hot-rolled wire rod for a welding wire and a production method thereof.
Background
ER70S-6 wire is currently the most widely used gas shielded wire of the carbon steel series, and is typically drawn from hot rolled wire rod of 5.5mm diameter.
Welding wire production enterprises are forced to be under increasingly severe industrial competition and production cost pressure, the drawing speed in the welding wire processing process is urgently needed to be increased so as to improve the production efficiency, and correspondingly, higher standards and requirements are provided for the performance of a wire rod for the welding wire, particularly the related performance influencing the drawing speed.
Through research, the performances and the quality of stripping of iron scale on the surface of the wire rod, the uniformity of the structure and the mechanical property of the wire rod and the like can influence the drawing speed.
For example, in the production process of processing a wire rod into a welding wire, a mechanical peeling method is usually adopted to remove iron oxide scales on the surface of the wire rod, and then a drawing process is performed. When the stripping performance of the iron oxide scale on the surface of the wire rod is poor, the iron oxide scale is always remained on the surface of the wire rod due to incomplete removal in mechanical stripping, so that poor surface lubrication is caused, abnormal damage or loss of a die is increased, the wire rod is further scratched to cause wire breakage, vicious circle is formed, and the improvement of the drawing speed is limited. Therefore, the stripping performance of the iron oxide scale is improved by controlling the thickness and the structure of the iron oxide scale, and the method is extremely important for meeting the requirements of welding wire production enterprises on the drawing speed.
For another example, the continuity of high plasticity of other parts of the wire rod is seriously affected by the local hard phase structures such as abnormal bainite or martensite of the wire rod, so that the wire rod is integrally deformed unevenly to cause wire breakage in drawing.
Disclosure of Invention
The invention aims to provide a hot-rolled wire rod for welding wires and a production method thereof, which can optimize the quality and the performance of the obtained wire rod so as to further meet the requirements of welding wire production enterprises.
In order to achieve one of the above objects, an embodiment further provides a hot-rolled wire rod for welding wire, the hot-rolled wire rod for welding wire comprising the following chemical components in percentage by weight: C. 0.060-0.075%; 0.80-0.88% of Si; 1.40-1.48% of Mn; p is less than or equal to 0.013%, S is less than or equal to 0.010%, Ti is 0.005-0.020%, and the balance of Fe and inevitable impurities.
Wherein, the chemical components and contents of C, Si, Mn and Ti have the following functions: c is one of important elements in the wire rod for the welding wire, so that the strength of the welding seam metal can be effectively improved; si is used as a main deoxidizing element and a strengthening element in the welding process; mn is used as a main strengthening element of weld metal and a main deoxidizing element in the welding process; ti can refine weld joint structure, and the toughness of weld metal is synchronously improved. In summary, the reasonable weight percentage range of the elements can ensure the toughness of the weld metal and the smooth operation of the welding process, the low total amount of the elements can cause insufficient weld strength, the high total amount of the elements can easily cause component segregation, the sensitivity of the hard phase structure generated by the wire rod is increased, and the drawing performance is deteriorated. Therefore, through content research and experiments on the components, the content of C is controlled to be 0.060-0.075%, the content of Si is controlled to be 0.80-0.88%, the content of Mn is controlled to be 1.40-1.48%, and the content of Ti is controlled to be 0.005-0.020%.
Further, P, S, an excessively high content of P, S as an impurity element in the wire rod, is liable to cause component segregation at the final stage of solidification of the molten steel, and is disadvantageous in wire rod drawing, and an excessively high content of P, S is disadvantageous in low-temperature toughness of the weld. Therefore, it is preferable that the range of P content is 0.013% or less and the range of S content is 0.010% or less.
Therefore, by optimizing the content of C, Si and Mn elements and simultaneously adding and optimizing the content of Ti elements, the wire rod has better structure and strength, reduces macro and micro segregation, greatly improves the drawing speed of the wire rod in the drawing welding wire, can be used for drawing finished welding wires with the diameter of less than or equal to 1.2mm at the drawing speed of 30m/s and above, has far-exceeding expected improvement compared with the drawing speed of 18-23 m/s in the prior art, also improves the welding seam structure, improves the toughness of the welding seam, and improves the welding performance of the welding wire.
As a further improvement of an embodiment, the chemical composition of the hot-rolled wire rod for welding wire further comprises the following components in percentage by weight: cr + Ni + Cu + Mo is less than or equal to 0.05 percent; and the number of the first and second electrodes,
the carbon equivalent Ceq ═ C ] + [ Mn ]/6+ [ Si ]/24+ [ Ni ]/40+ [ Cr ]/5+ [ Mo ]/4+ [ V ]/14 is less than or equal to 0.35. Therefore, by controlling impurity elements such as Cr, Ni, Cu, Mo and the like and carbon equivalent, the difficulty of microstructure control in the processes of microsegregation and steel rolling is reduced, the structure and the strength of the wire rod are improved, and the drawing speed of the wire rod in the drawing welding wire is further ensured.
In order to achieve one of the above objects, one embodiment provides a method for producing a hot-rolled wire rod for a welding wire, which includes a molten steel smelting process, a refining process, a casting process, a heating process, a temperature-controlled rolling process, and a stelmor slow-cooling process, which are sequentially performed to obtain a hot-rolled wire rod for a welding wire;
the temperature control rolling process comprises the following steps: descaling the steel billet obtained in the heating procedure by high-pressure water, rolling the steel billet into a wire rod, wherein the inlet temperature of a finishing mill is less than or equal to 880 ℃, advancing the wire rod on a production line for at least 50m after finishing rolling, then performing water cooling, and spinning after cooling, wherein the spinning temperature is 880-910 ℃;
the stelmor slow cooling process comprises the following steps: and (3) carrying out heat preservation and slow cooling on the wire rod obtained in the temperature control rolling procedure on a stelmor slow cooling line, closing a heat preservation cover and a draught fan air port, and enabling the cooling speed of the wire rod in a phase change temperature range to be less than or equal to 0.8 ℃/s.
According to the embodiment, the thickness and the structure of the iron scale on the surface of the wire rod are effectively controlled by controlling the inlet temperature, the water cooling time, the spinning temperature and the stelmor slow cooling of the finishing mill, so that the thickness of the obtained iron scale on the surface of the wire rod is more than 10 microns, and the wire rod obtained based on the embodiment has excellent stripping performance compared with the prior art and is favorable for improving the drawing speed of the wire rod when the wire rod is drawn into a welding wire.
As a further improvement of an embodiment, in the temperature-controlled rolling process, the descaling water pressure is greater than or equal to 18MPa, and the intermediate rolling mill adopts a machining groove, so that the scale on the surface of the billet can be effectively removed, the residual scale can be prevented from being pressed into the deep tissue of the wire rod in the process of rolling the wire rod, meanwhile, the surface smoothness of the wire rod can be ensured through the machining groove, the increase of the surface defects of the wire rod due to the rough surface of the groove can also be avoided, the pressing depth of the scale of the wire rod obtained based on the method is less than or equal to 10 μm, the tissue and the strength performance of the wire rod can be ensured, and the drawing speed of the wire rod when the wire rod is drawn into a welding wire can be further improved.
As a further improvement of an embodiment, on the stelmor slow cooling line, the total length of all the heat-insulating covers is more than 80m, so that the length of the wire rod maintained on the heat-insulating slow cooling conveying roller is more than 80m, the inlet roller way speed of the stelmor slow cooling line is less than or equal to 0.18m/s, and the outlet roller way speed of the stelmor slow cooling line is less than or equal to 0.40 m/s. Therefore, the lower cooling speed can be further ensured to be maintained, the residence time between the phase change temperature intervals is prolonged, the thickness and the structure of the iron oxide scale on the surface of the wire rod can be reasonably controlled to improve the mechanical stripping performance of the iron oxide scale, the uniformity of the internal structure of the wire rod is improved, and the drawing speed of the wire rod when the wire rod is drawn into a welding wire is further improved.
As a further improvement of an embodiment, the molten steel smelting step includes: smelting a smelting raw material consisting of molten iron and scrap steel in a converter, wherein the molten iron accounts for more than 90% of the smelting raw material by weight, and adding ferrosilicon, silicomanganese, low-carbon ferromanganese and lime into the molten steel in sequence in the tapping process. Therefore, the high purity of the molten steel components is ensured by controlling the weight percentage of the molten iron and the adding time of various alloys and lime, so that the structure and the strength of the wire rod are finally improved, the drawing speed of the wire rod when the wire rod is drawn into a welding wire is further improved, and the welding performance of the welding wire can be improved.
In a further improvement of an embodiment, in the molten steel smelting process, the addition amount of the ferrosilicon is 12.5 ± 0.5kg/t, the addition amount of the silicomanganese is 7.0 ± 0.5kg/t, and the addition amount of the low-carbon ferromanganese is 12.0 ± 0.5 kg/t. Therefore, compared with the prior art, the embodiment surprisingly discovers that the high purity of the molten steel components is unexpectedly and greatly improved under the sequence by regulating and controlling the adding sequence of various alloys, and further improves the purity, the structure and the strength of the wire rod.
As a further improvement of an embodiment, the chemical composition of the scrap steel satisfies: c is less than or equal to 0.15 percent; si is less than or equal to 0.95 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.020%, S is less than or equal to 0.015%, Cr + Ni + Cu + Mo is less than or equal to 0.10%, and the balance is Fe and inevitable impurities. By selecting high-quality scrap steel with purest chemical components and less impurity content, the difficulty of impurity removal in the subsequent steps is reduced, and the high purity of molten steel components is ensured.
As a further improvement of an embodiment, the refining step: refining the molten steel obtained in the molten steel smelting process in an LF furnace for more than 35min, deoxidizing and desulfurizing by making white slag for more than 15min during the refining period, adjusting the content of other alloys to meet a target range before feeding a titanium iron wire, and carrying out soft stirring for more than 15min at the later stage of refining;
the casting process comprises the following steps: and carrying out full-protection casting on the molten steel obtained in the refining process, wherein the superheat degree of the molten steel is 18-35 ℃, the casting blank keeps a constant drawing speed, and the drawing speed is 2.5-2.7 m/min, so as to obtain a steel blank. Therefore, through the time control of feeding the titanium iron wire, the burning loss of titanium in the early stage of refining is avoided, the yield of titanium elements is improved, the chemical components of the final wire rod are optimized, the production cost is effectively controlled, the structure and the strength of the wire rod can be ensured by the chemical components and the percentage of the chemical components in the embodiment, and the welding performance of the prepared welding wire is ensured; and the time management and control of various treatments in the refining and the control of casting modes, superheat degree, drawing speed and the like greatly improve the homogenization of molten steel to reduce the macro and micro segregation of the blank, so that the structure and strength of the finally obtained wire rod are improved, and the drawing speed of the wire rod when the wire rod is drawn into a welding wire is further improved.
In combination with the above, compared with the prior art, the processing method of the hot-rolled wire rod for the welding wire of the embodiment reduces the macro and micro segregation of the blank by improving the uniformity and purity of the molten steel components, and improves the surface defect depth, the harness cord structure and strength uniformity, the mechanical stripping property and plasticity of the iron scale and the like of the wire rod, so that the wire rod finally obtained by the processing method has the tensile strength of less than or equal to 520MPa, the harness cord strength difference of less than or equal to 25MPa, the section shrinkage of more than or equal to 80%, the volume percentage of the hard phase structure of less than or equal to 1%, the pressing depth of the iron scale of less than or equal to 10 μm, and the thickness of the iron scale of more than or equal to 10 μm, thereby finally ensuring that the wire rod can be used for drawing a finished welding wire with the diameter of.
Detailed Description
In one embodiment of the invention, the hot rolled wire rod for the welding wire comprises the following chemical components in percentage by weight: C. 0.060-0.075%; 0.80-0.88% of Si; 1.40-1.48% of Mn; p is less than or equal to 0.013%, S is less than or equal to 0.010%, Ti is 0.005-0.020%, and the balance of Fe and inevitable impurities.
And preferably, the chemical components of the hot-rolled wire rod for welding wires further comprise the following components in percentage by weight: cr + Ni + Cu + Mo is less than or equal to 0.05 percent; and the number of the first and second electrodes,
the carbon equivalent Ceq ═ C ] + [ Mn ]/6+ [ Si ]/24+ [ Ni ]/40+ [ Cr ]/5+ [ Mo ]/4+ [ V ]/14 is less than or equal to 0.35.
Wherein, in the above formula of the carbon equivalent Ceq, the middle brackets "[ ]" represents the weight percentage of the element therein, for example, [ C ] represents the weight percentage of C.
Further, the present embodiment provides a method for producing the hot-rolled wire rod for a welding wire, which includes a molten steel smelting process, a refining process, a casting process, a heating process, a temperature-controlled rolling process, and a stelmor slow cooling process, which are sequentially performed to obtain the hot-rolled wire rod for a welding wire.
The respective steps described above will be described in the following order of execution.
(1) Molten steel smelting process
Smelting raw materials consisting of molten iron and scrap steel in a converter, wherein the scrap steel is preferably high-quality scrap steel, such as a head and tail billet cut from low-carbon steel smelting, but is not limited to the above, and the chemical composition of the scrap steel specifically satisfies the following conditions: c is less than or equal to 0.15 percent; si is less than or equal to 0.95 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.020%, S is less than or equal to 0.015%, Cr + Ni + Cu + Mo is less than or equal to 0.10%, and the balance is Fe and inevitable impurities. By selecting high-quality scrap steel with purest chemical components and less impurity content, the difficulty of impurity removal in the subsequent steps is reduced, and the high purity of molten steel components is ensured.
The molten iron accounts for more than 90 percent of the smelting raw materials by weight, and the high purity of the molten steel components is ensured by controlling the weight percent of the molten iron. In addition, the weight percentage of S in each ladle of molten iron is less than or equal to 0.03 percent, and the weight percentage of P is less than or equal to 0.09 percent.
When the converter in the molten steel smelting process taps 1/3, ferrosilicon, silicomanganese, low-carbon ferromanganese and lime are added into molten steel in sequence to adjust the component content and slagging in the molten steel.
Further, the adding amount of the ferrosilicon alloy is 12.5 plus or minus 0.5kg/t, namely the ferrosilicon alloy is added into the molten steel according to the proportion of adding 12.5 plus or minus 0.5kg of the ferrosilicon alloy into each ton of the molten steel; similarly, the addition amount of the silicon-manganese alloy is 7.0 +/-0.5 kg/t, and the addition amount of the low-carbon ferromanganese alloy is 12.0 +/-0.5 kg/t. Through research, compared with the prior art, the method and the device have the advantages that the high purity of the molten steel components is unexpectedly and greatly improved by regulating and controlling the adding sequence of various alloys, and further the purity, the structure and the strength of the wire rod are improved.
(2) Refining procedure
Refining the molten steel obtained in the molten steel smelting process in an LF furnace for more than 35min, deoxidizing and desulfurizing by making white slag for more than 15min during the refining period, adjusting the content of other alloys to meet a target range before feeding a titanium iron wire, and carrying out soft stirring for more than 15min at the later stage of refining. Therefore, through the time control of feeding the ferrotitanium wire, the burning loss of titanium in the early stage of refining is avoided, the yield of titanium elements is improved, the chemical components of the final wire rod are optimized, and the production cost is effectively controlled; and the time management and control of various treatments in the refining greatly improve the homogenization of molten steel, so as to reduce the macro and micro segregation of the blank, and improve the structure and strength of the finally obtained wire rod.
(3) Casting process
And performing full-protection casting on the molten steel obtained in the refining process, for example, specifically, performing full-protection casting on the molten steel by using a ladle long nozzle argon seal, a tundish covering agent and a whole nozzle full-protection argon seal so as to avoid influence of over oxidation on the purity of the molten steel, wherein the superheat degree of the molten steel is controlled to be 18-35 ℃, the casting blank keeps a constant drawing speed and the drawing speed is 2.5-2.7 m/min, and a billet with the section size of 140mm multiplied by 140mm is obtained, but the size of the billet is not limited thereto. The homogenization of molten steel is greatly improved by controlling the superheat degree, the drawing speed and the like, so that the macrosegregation and the microsegregation of a blank are reduced, and the structure and the strength of a finally obtained wire rod are improved.
Wherein, the superheat degree of the molten steel is further preferably controlled to be 18-28 ℃, so that the macro and micro segregation of the blank is further reduced.
(4) Heating step
And (3) carrying out temperature-controlled heating on the steel billet obtained in the casting process in a heating furnace, wherein the temperature of a heating section is 920-1020 ℃, more preferably 960-1020 ℃, and the temperature of a soaking section is 1080-1120 ℃, more preferably 1040-1120 ℃.
(5) Temperature controlled rolling process
And (3) rolling the billet obtained in the heating procedure into a wire rod after high-pressure water descaling, wherein the descaling water pressure is more than or equal to 18MPa, so that the scale on the surface of the billet can be effectively removed, and the residual scale can be prevented from being pressed into the deep tissue of the wire rod in the process of rolling into the wire rod.
The medium rolling mill adopts a machining rolling groove, and compared with the traditional rolling groove manufactured by the existing laser cladding method, the surface flatness of the wire rod can be ensured, and the increase of the surface defects of the wire rod caused by the rough surface of the rolling groove can also be avoided.
When the billet is rolled after descaling, the initial rolling temperature is 970-1000 ℃, the inlet temperature of a finishing mill is less than or equal to 880 ℃, and the plasticity of the rolled wire rod is improved through low-temperature rolling.
The wire rod moves forwards by at least 50m on a production line after finish rolling and then enters water cooling for cooling, then the wire rod is spun after cooling, the spinning temperature is 880-910 ℃, namely the water cooling is carried out between a rolling mill and a spinning machine, and the distance between the water cooling and the rolling mill is not less than 50m, so that the wire rod obtained through the finish rolling does not enter the water cooling immediately as in the prior art, but passes through 50m for cooling intensively under the condition of no water cooling on the production line, the duration time of the wire rod at high temperature is prolonged, the thickness and the structure of iron scale on the surface of the wire rod are controlled, and experiments prove that the stripping performance of the iron scale of the wire rod obtained based on the embodiment is greatly improved.
This embodiment can be implemented by the following scheme: three or more water cooling water tanks are arranged between the rolling mill and the wire laying head in sequence, when the wire rod passes through the three water cooling water tanks after leaving the rolling mill, only one water cooling water tank close to the wire laying head is opened, and at most two water cooling water tanks are closed. Of course, not limited thereto.
(6) Stelmor slow cooling process
And (3) carrying out heat preservation and slow cooling on the wire rod obtained in the temperature control rolling procedure on a stelmor slow cooling line, closing a heat preservation cover and a draught fan air port, and keeping the cooling speed of the wire rod in a phase change temperature interval to be less than or equal to 0.8 ℃/s, so that the retention time of the wire rod in the phase change temperature interval is prolonged, and the thickness and the structure of the iron oxide scale on the surface of the wire rod are further realized.
The total length of all the heat-insulating covers is more than 80m, so that the length of the wire rod maintained on the heat-insulating slow-cooling conveying roller is more than 80m, the speed of an inlet roller way of a stelmor slow-cooling line is less than or equal to 0.18m/s, and the speed of an outlet roller way of the stelmor slow-cooling line is less than or equal to 0.40 m/s. Therefore, the lower cooling speed can be further ensured to be maintained, the residence time between the phase change temperature intervals is prolonged, the thickness and the structure of the iron oxide scale on the surface of the wire rod can be reasonably controlled to improve the mechanical stripping performance of the iron oxide scale, the uniformity of the internal structure of the wire rod is improved, and the drawing speed of the wire rod when the wire rod is drawn into a welding wire is further improved.
The following describes further embodiments of the present invention with 6 examples of the specific numbers 1 to 6 in combination with 3 comparative examples of the specific numbers 7 to 9.
(1) Molten steel smelting process
Smelting a smelting raw material consisting of molten iron and scrap steel in a 180t converter, wherein the weight percentage of S in each ladle of molten iron is less than or equal to 0.03%, the weight percentage of P is less than or equal to 0.09%, and the total charging amount of the smelting raw materials of 6 examples and 3 comparative examples, the weight percentage of molten iron in the smelting raw material, the weight percentage of S in the molten iron, the weight percentage of P in the molten iron, the smelting time, the weight percentage of C at the time of tapping, the weight percentage of P at the time of tapping, the tapping temperature and the like are respectively shown in Table 1;
[ Table 1]
Figure BDA0002432909860000081
In addition, the chemical components of the scrap steel in 6 embodiments meet the following requirements: c is less than or equal to 0.15 percent; si is less than or equal to 0.95 percent;
mn is less than or equal to 1.5 percent; p is less than or equal to 0.020 percent, S is less than or equal to 0.015 percent, Cr, Ni, Cu and Mo are less than or equal to 0.10 percent, and the balance is Fe and inevitable impurities, and the waste steel in 3 comparative examples does not satisfy the following chemical components: c is less than or equal to 0.15 percent; si is less than or equal to 0.95 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.020 percent, S is less than or equal to 0.015 percent, Cr + Ni + Cu + Mo is less than or equal to 0.10 percent, and the balance is common scrap steel of Fe and inevitable impurities (including all related elements which do not meet the corresponding range or part of the related elements which do not meet the corresponding range);
in 6 examples, the silicon-iron alloy, the silicon-manganese alloy, the low-carbon ferromanganese alloy and the lime were added to the molten steel in the order of addition at the time of tapping 1/3, and the specific addition amounts are shown in table 2, respectively, while in 3 comparative examples, the silicon-iron alloy, the silicon-manganese alloy, the low-carbon ferromanganese alloy and the lime were added to the molten steel in the order of addition at the time of tapping 1/3, and the specific addition amounts are shown in table 2, respectively.
[ Table 2]
Figure BDA0002432909860000091
(2) Refining procedure
Refining the molten steel obtained in the molten steel smelting process in an LF furnace, deoxidizing and desulfurizing by making white slag during the refining, adjusting the content of other alloys to meet a target range before feeding a titanium iron wire, and performing soft stirring at the later stage of refining, wherein the soft stirring takes the operation standard that the slag surface slightly fluctuates and the molten steel is not exposed.
In the 6 examples and 3 comparative examples, the casting time or continuous casting time, refining time, white slag forming time, soft stirring time, and tapping temperature are shown in table 3.
[ Table 3]
Figure BDA0002432909860000092
(3) Casting process
The molten steel obtained in the refining process is subjected to full-protection casting, for example, the full-protection casting specifically comprises ladle long nozzle argon sealing, tundish covering agent and integral nozzle full-protection argon sealing casting, so that the influence of over oxidation on the purity of the molten steel is avoided;
the degrees of superheat and the casting speeds of the molten steels in 6 examples and 3 comparative examples were controlled as shown in Table 4, and the casting was carried out while maintaining a constant casting speed, and a billet having a cross-sectional size of 140mm X140 mm was cast while keeping an electromagnetic stirring current of a mold of 350A and a frequency of 4Hz and an electromagnetic stirring current at a tip of 480A and a frequency of 10 Hz.
[ Table 4]
Figure BDA0002432909860000101
(4) Heating step
The steel billets obtained in the casting process were heated in a heating furnace at controlled temperatures, and the heating zone temperature, the soaking zone temperature, the air-fuel ratio of the soaking zone, and the holding time of 6 examples and 3 comparative examples were controlled as shown in table 5.
[ Table 5]
Figure BDA0002432909860000102
(5) Temperature controlled rolling process
And (3) removing scale from the steel billet obtained in the heating procedure through high-pressure water after the steel billet is taken out of the heating furnace, and then rolling the steel billet into a wire rod.
Wherein, the descaling water pressure, the type of the rolling groove used in the intermediate rolling mill, the amount of steel passing through the tungsten carbide roll collar used in the final two-pass finishing mill, the start rolling temperature, the finishing mill inlet temperature, the spinning temperature, etc. of 6 examples and 3 comparative examples were controlled as shown in table 6; in addition, three water boxes of 5#, 6# and 7# are arranged between the finishing mill and the laying head in sequence from front to back as the last pass of the final rolling, wherein the 5# water box is adjacent to the last rolling mill, the distance between the two water boxes is approximately 65cm, the distance between the 6# water box and the last rolling mill is 50m, and the opening conditions of the three water boxes of 5#, 6# and 7# in 6 examples and 3 comparative examples are also shown in table 6.
[ Table 6]
Figure BDA0002432909860000111
(6) Stelmor slow cooling process
And (3) carrying out heat preservation and slow cooling on the wire rod obtained in the temperature control rolling procedure on a stelmor slow cooling line, closing a heat preservation cover and a draught fan air port, and enabling the cooling speed of the wire rod in a phase change temperature range to be less than or equal to 0.8 ℃/s. The total length of all the heat-insulating covers, the inlet roller table speed, the outlet roller table speed, and the like of the stelmor slow cooling lines of 6 examples and 3 comparative examples were controlled as shown in table 7.
The cooling speed of the wire rod in the phase change temperature range can be obtained by adopting an infrared thermometer to test the temperature between the heat preservation covers of the wire rod and calculating according to the temperature.
[ Table 7]
Figure BDA0002432909860000112
Figure BDA0002432909860000121
The final wire rod product was prepared according to the above-described production method in each of 6 examples and 3 comparative examples, and the wire rod was examined.
The chemical composition and weight percentage (numerical unit,%) of the finished wire rod are shown in table 8, wherein Ceq ═ C ] + [ Mn ]/6+ [ Si ]/24+ [ Ni ]/40+ [ Cr ]/5+ [ Mo ]/4+ [ V ]/14, and the structure, mechanical properties, scale penetration depth, and mechanical scale peeling rate of the wire rod are shown in table 9.
[ Table 8]
Figure BDA0002432909860000122
[ Table 9]
Figure BDA0002432909860000123
It can be seen from the above examples and comparative examples that the hot rolled wire rod for welding wire and the production method thereof according to the embodiment control the structure type and surface quality of the hot rolled wire rod by high purity purification and homogenization control of molten steel components during smelting and control of the structure type and surface quality of the hot rolled wire rod during controlled rolling and controlled cooling, and the produced wire rod has uniform structure, strength and plasticity, the strength difference of the whole wire rod is less than or equal to 25MPa, and the hot rolled wire rod is more suitable for high-speed drawing and can promote upgrading of the existing products.
Through implementation and verification, the drawing speed of the finished wire rod produced by the production method in the embodiment 1-6 can reach more than 30m/s when the welding wire with the diameter of 1.2mm is manufactured, the content of part of elements and key production process parameters in the comparative examples 7-9 are out of the range of the embodiment, the drawing speed is only 23m/s at the highest when the welding wire with the diameter of 1.2mm is manufactured, and the wire breakage is serious when the drawing speed is further increased, so that the normal production cannot be realized.
The above-mentioned examples only express the specific embodiments of the present invention, but should not be construed as limiting the scope of the present invention. Any modifications of the present invention which would occur to those skilled in the art and which are within the spirit of the invention are considered to be within the scope of the present invention.

Claims (10)

1. A hot-rolled wire rod for welding wires is characterized by comprising the following chemical components in percentage by weight: C. 0.060-0.075%; 0.80-0.88% of Si; 1.40-1.48% of Mn; p is less than or equal to 0.013 percent, S is less than 0.010 percent, Ti is 0.005-0.020 percent, and the balance is Fe and inevitable impurities;
the wire rod is prepared by a molten steel smelting process, a refining process, a casting process, a heating process, a temperature-controlled rolling process and a stelmor slow cooling process which are sequentially carried out; wherein:
the molten steel smelting process comprises the following steps: smelting a smelting raw material consisting of molten iron and scrap steel in a converter, and adding ferrosilicon alloy, silicomanganese alloy, low-carbon ferromanganese alloy and lime into the molten steel in sequence in the tapping process;
the temperature control rolling process comprises the following steps: descaling the steel billet obtained in the heating procedure by high-pressure water, rolling the steel billet into a wire rod, wherein the inlet temperature of a finishing mill is less than or equal to 880 ℃, advancing the wire rod on a production line for at least 50m after finishing rolling, then performing water cooling, and spinning after cooling, wherein the spinning temperature is 880-910 ℃;
the stelmor slow cooling process comprises the following steps: and (3) carrying out heat preservation and slow cooling on the wire rod obtained in the temperature control rolling procedure on a stelmor slow cooling line, closing a heat preservation cover and a draught fan air port, and enabling the cooling speed of the wire rod in a phase change temperature range to be less than or equal to 0.8 ℃/s.
2. The hot rolled wire rod for welding wire as claimed in claim 1, wherein the chemical composition further comprises, in weight percent: cr + Ni + Cu + Mo is less than or equal to 0.05 percent; and the number of the first and second electrodes,
the carbon equivalent Ceq ═ C ] + [ Mn ]/6+ [ Si ]/24+ [ Ni ]/40+ [ Cr ]/5+ [ Mo ]/4+ [ V ]/14 is less than or equal to 0.35.
3. The production method of the hot-rolled wire rod for the welding wire according to claim 1 or 2, characterized in that the hot-rolled wire rod for the welding wire is obtained by a molten steel smelting process, a refining process, a casting process, a heating process, a temperature-controlled rolling process and a stelmor slow cooling process which are sequentially performed;
the molten steel smelting process comprises the following steps: smelting a smelting raw material consisting of molten iron and scrap steel in a converter, and adding ferrosilicon alloy, silicomanganese alloy, low-carbon ferromanganese alloy and lime into the molten steel in sequence in the tapping process;
the temperature control rolling process comprises the following steps: descaling the steel billet obtained in the heating procedure by high-pressure water, rolling the steel billet into a wire rod, wherein the inlet temperature of a finishing mill is less than or equal to 880 ℃, advancing the wire rod on a production line for at least 50m after finishing rolling, then performing water cooling, and spinning after cooling, wherein the spinning temperature is 880-910 ℃;
the stelmor slow cooling process comprises the following steps: and (3) carrying out heat preservation and slow cooling on the wire rod obtained in the temperature control rolling procedure on a stelmor slow cooling line, closing a heat preservation cover and a draught fan air port, and enabling the cooling speed of the wire rod in a phase change temperature range to be less than or equal to 0.8 ℃/s.
4. The production method of the hot-rolled wire rod for the welding wire according to claim 3, wherein in the temperature-controlled rolling process, the descaling water pressure is more than or equal to 18MPa, and a medium rolling mill adopts a machining groove.
5. The method for producing a hot-rolled wire rod for a welding wire according to claim 3, wherein the total length of all the heat-insulating covers on the stelmor slow cooling line is greater than 80m, the inlet roller speed of the stelmor slow cooling line is not greater than 0.18m/s and the outlet roller speed thereof is not greater than 0.40 m/s.
6. The method for producing a hot-rolled wire rod for a welding wire according to claim 3, wherein the molten steel smelting step comprises: the molten iron accounts for more than 90 percent of the smelting raw materials by weight.
7. The method for producing the hot-rolled wire rod for the welding wire according to claim 6, wherein in the molten steel smelting process, the addition amount of the silicon-iron alloy is 12.5 +/-0.5 kg/t, the addition amount of the silicon-manganese alloy is 7.0 +/-0.5 kg/t, and the addition amount of the low-carbon manganese-iron alloy is 12.0 +/-0.5 kg/t.
8. The method for producing a hot-rolled wire rod for welding wire according to claim 6, wherein the chemical composition of the scrap steel satisfies: c is less than or equal to 0.15 percent; si is less than or equal to 0.95 percent; mn is less than or equal to 1.5 percent; p is less than or equal to 0.020%, S is less than or equal to 0.015%, Cr + Ni + Cu + Mo is less than or equal to 0.10%, and the balance is Fe and inevitable impurities.
9. The method for producing a hot-rolled wire rod for a welding wire according to claim 6, wherein the refining step: refining the molten steel obtained in the molten steel smelting process in an LF furnace for more than 35min, deoxidizing and desulfurizing by making white slag for more than 15min during the refining period, adjusting the content of other alloys to meet a target range before feeding a titanium iron wire, and carrying out soft stirring for more than 15min at the later stage of refining.
10. The method for producing a hot-rolled wire rod for welding wire according to claim 6, wherein the casting process: and carrying out full-protection casting on the molten steel obtained in the refining process, wherein the superheat degree of the molten steel is 18-35 ℃, the casting blank keeps a constant drawing speed, and the drawing speed is 2.5-2.7 m/min, so as to obtain a steel blank.
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