阅读说明：本技术 粗拉断丝率低于3次每千吨的82级帘线钢及其生产方法 (82-grade cord steel with coarse wire breaking rate lower than 3 times per kiloton and production method thereof ) 是由 鲁修宇 仇东丽 张贤忠 朱冬梅 张向亮 于 2021-08-11 设计创作，主要内容包括：本发明特别涉及粗拉断丝率低于3次每千吨的82级帘线钢及其生产方法,属于钢材制备技术领域,方法包括：铁水脱硫→转炉冶炼→吹氩→LF炉处理→方坯连铸→方坯加热→高线轧制→斯太尔摩控冷→集卷；在650℃以上进行快冷处理,可以保证足够的过冷度,避免渗碳体的异常析出；在650℃后缓冷可延长珠光体生长时间,使得珠光体片层间距较大,而且氧化铁皮更加厚实致密。珠光体片层间距较大可保证盘条具有较强的塑性,氧化铁皮厚实致密可以提高氧化铁皮在粗拉过程中的剥落完整性,避免细小氧化铁皮在粗拉轮上粘连造成的盘条表面划伤,保证盘条表面质量。(The invention particularly relates to 82-grade cord steel with a rough wire breakage rate lower than 3 times per kiloton and a production method thereof, belonging to the technical field of steel preparation, and the method comprises the following steps: molten iron desulphurization → converter smelting → argon blowing → LF furnace treatment → square billet continuous casting → square billet heating → high speed wire rolling → stelmor controlled cooling → coil collection; the rapid cooling treatment is carried out at the temperature of more than 650 ℃, so that the sufficient supercooling degree can be ensured, and the abnormal precipitation of cementite is avoided; after the temperature is 650 ℃, the slow cooling can prolong the growth time of pearlite, so that the space between pearlite lamellae is larger, and the iron scale is thicker and more compact. The wire rod can be ensured to have stronger plasticity due to the larger distance between pearlite lamellae, the scale can be thickened and compacted to improve the peeling integrity of the scale in the rough-drawing process, the surface scratch of the wire rod caused by the adhesion of the small scale on a rough-drawing wheel is avoided, and the surface quality of the wire rod is ensured.)

1. A method for producing a grade 82 cord steel having a gross breakage rate of less than 3 per kiloton, the method comprising:

desulfurizing molten iron to obtain desulfurized molten iron;

carrying out converter smelting on the desulfurized molten iron to obtain molten steel;

carrying out LF refining on the molten steel to obtain refined molten steel;

continuously casting the refined molten steel; obtaining a casting blank;

heating the casting blank to obtain a casting blank to be rolled;

rolling the casting blank to be rolled, and then performing controlled cooling to obtain cord steel; the chemical composition of the steel comprises the following components in percentage by mass: c: 0.79% -0.83%, Si: 0.20% -0.45%, Mn: 0.45% -0.65%, P: less than or equal to 0.015%, S: less than or equal to 0.015 percent, Cu: less than or equal to 0.10 percent, Ni: less than or equal to 0.20 percent, Cr: 0.10% -0.18%, (Nb + V + Ti): less than or equal to 0.10 percent, N: less than or equal to 0.007 percent, Als: less than or equal to 0.008 percent, and the balance of Fe and inevitable impurities; in the controlled cooling, when the temperature of the rolled casting blank is higher than the preset temperature, the speed of the conveying roller way is gradually increased; when the temperature of the rolled casting blank is lower than a preset temperature, the speed of the conveying roller way is gradually reduced, and the preset temperature is 650 +/-5 ℃.

2. A method of producing a grade 82 cord steel having a rough wire breakage rate of less than 3 per kiloton as claimed in claim 1, wherein the cooling means for controlled cooling is a stelmor air cooling line comprising 14 sets of blower roller tables having an initial speed of 0.8m/s ± 0.05 m/s.

3. The method for producing 82-grade cord steel with a rough wire breakage rate lower than 3 times per kiloton according to claim 2, wherein in the controlled cooling, when the ambient temperature is lower than 10 ℃, the blower roller ways from 1 st to 9 th are controlled to be gradually increased by 3% ± 0.2%, and the blower roller ways from 10 th to 14 th are controlled to be gradually decreased by 5% ± 0.2%; and when the environmental temperature is not lower than 10 ℃, controlling the 1 st to 11 th fan roller ways to gradually increase by 3% +/-0.2%, and controlling the 12 th to 14 th fan roller ways to gradually decrease by 5% +/-0.2%.

4. The method for producing the 82-grade cord steel with the rough wire breakage rate lower than 3 times per kiloton according to claim 1, wherein the superheat degree of molten steel in a continuous casting tundish is less than or equal to 20 ℃, the drawing speed of the continuous casting is 1.00-1.30 m/min, the continuous casting adopts a solidification tail end dynamic soft reduction process, and the total pressing amount of a casting blank is more than or equal to 15 mm.

5. The method for producing 82-grade cord steel with a rough breaking rate lower than 3 times per kiloton according to claim 1, wherein the desulfurization adopts a magnesium powder spraying desulfurization process, and the sulfur content in the molten desulfurization iron is less than or equal to 0.010% by mass.

6. The method for producing 82-grade cord steel with a rough breaking rate lower than 3 times per kiloton according to claim 1, wherein the tapping temperature of converter smelting is 1630-1700 ℃, the tapping time of converter smelting is not less than 4min, the bottom argon blowing time of converter smelting is not less than 4min, the pressure of bottom argon blowing is 0.3-0.6 MPa, and the flow rate of bottom argon blowing is 7.0Nm³/min-10.0Nm³/min。

7. Method for producing a grade 82 cord steel with a rough breaking rate lower than 3 times per kiloton according to claim 1, characterized in that said LF refining uses CaO-SiO₂-Al₂O₃Refining slag system, controlling the slag alkalinity of LF refining to be 1.5-3.5, wherein the LF refining time is more than or equal to 28min, and blowing argon in the whole LF refining process.

8. The method for producing 82-grade cord steel with a rough breaking rate lower than 3 times per kiloton according to claim 1, wherein the temperature of the heating soaking section is 1100-1250 ℃, the temperature difference of the heating section is less than or equal to 30 ℃, the heating atmosphere is a reducing atmosphere, and the heating time is 125-185 min.

9. The method for producing 82-grade cord steel having a rough breaking rate of less than 3 times per kiloton according to claim 1, wherein the rolling start temperature is 950 ℃ to 1050 ℃, the rolling finish temperature is 880 ℃ to 920 ℃, the sizing temperature is 890 ℃ to 930 ℃, and the rolling laying temperature is 910 ℃ to 940 ℃.

10. 82-grade cord steel with a gross breakage rate lower than 3 per kiloton, characterized in that the steel is prepared by the production method of 82-grade cord steel with a gross breakage rate lower than 3 per kiloton according to claims 1 to 9.

Technical Field

The invention belongs to the technical field of steel preparation, and particularly relates to 82-grade cord steel with a coarse wire breakage rate lower than 3 times per kiloton and a production method thereof.

Background

The cord steel wire rod is a raw material for manufacturing a tire meridian, the demand of the cord steel wire rod exceeds 200 ten thousand tons, the demand of the cord steel wire rod is increased year by year, and the downstream deep processing procedure is long and comprises drawing and heat treatment of twenty more passes. The iron scale on the surface of the wire rod needs to be removed before the wire rod is subjected to continuous cold drawing, and with increasingly severe social requirements on energy conservation and environmental protection, the procedure of removing the iron scale of the wire rod of the cord steel is changed from acid washing to mechanical descaling, so that the requirement of a user on the thickness of the iron scale on the surface of the cord steel is changed. In the pickling process, the thinner the iron scale on the surface of the wire rod is, the easier the wire rod is to be removed in the pickling process; and in the mechanical descaling process, the thicker and firmer the iron scale on the surface of the wire rod, the easier the integral falling is realized.

In the mechanical descaling process, the wire rod is repeatedly bent, and the iron oxide scale on the surface of the wire rod is stripped from the matrix, so that the wire rod has the subsequent drawing condition. The wire rod is only subjected to bending action during mechanical descaling and is not subjected to drawing deformation, and the fracture occurring in this process is called rough fracture. The wire rod needs to be welded manually after being subjected to rough drawing, so that the risk of breakage of materials in the subsequent processing process is increased, unnecessary manual labor is generated, and partial material waste is caused.

The high reinforcement is the inevitable development trend of the tire cord steel, and according to data in the tire industry, the weight of the steel for the tire can be reduced by 10 percent when the tire cord steel is improved by one strength grade, so that the rolling resistance of the tire can be reduced, and the oil consumption of automobiles can be reduced. However, as the strength of the wire rod is improved, the probability of the wire rod to be subjected to rough breaking is increased, according to the requirements of users, the rough breaking rate of the 82-grade cord steel should be less than 3.0 times/kiloton, but the actual breaking rate level of the 82-grade cord steel is about 20.0 times/kiloton, which is much higher than the requirements of users.

The types of rough snapping of the cord steel wire rod mainly include three types: foreign matter is pressed in, necked down and leveled and brittle failure. Foreign matter is pressed into the surface of the wire rod, and foreign matters such as cutting nodules on the end part of a billet, broken roll collar particles in a rolling line and the like which are not cleaned are pressed into the surface of the wire rod, so that the integrity of the wire rod is damaged; the necking is mainly due to the fluctuation of tension in rolling, and the diameter of a wire rod becomes thin until the wire rod is broken by pulling; the flush brittle fracture is mainly caused by that the surface of the wire rod is scratched in the process of transportation, a crack source is formed, and the brittle fracture occurs. According to the occurrence frequency, three types of fractures are arranged as follows: flush brittle fracture (70%), neck (20%), foreign matter pressed in (10%). Although the rough snapping of cord steel coils appears in many forms, the main reason can be attributed to the low plasticity of the coil, which is insufficient to compensate for its surface defects. Under the condition of avoiding scratches as much as possible, the rough breaking phenomenon of the cord thread steel can be greatly reduced by improving the plasticity of the wire rod and the uniformity of the whole wire rod, the labor cost is reduced, the labor efficiency is improved, and the obvious economic cost is achieved.

The Chinese patent application CN111069280 discloses a production method of a low-strength cord steel wire rod, and the purpose of improving the structure performance of the wire rod is achieved by designing parameters such as the number of cooling water tanks, the pressure of a water cooling tank, the spinning temperature, the roller speed, the air volume of a fan and the like after finish rolling. The wire rod produced by the technical scheme of the invention has the following properties: the tensile strength of the 72-grade cord steel wire rod is 700-980 MPa; the tensile strength of the 82-grade cord steel wire rod is 900-1100 MPa; the tensile strength of the 92-grade cord steel wire rod is 1000-1230 MPa; the sorbite content of the cord steel wire rod of any level is less than or equal to 80 percent, the level of the network carbide is less than or equal to 3, and the size of the pearlite colony is 20-40 mu m. The technical scheme of the invention can improve the quality problems of the core part and the surface of the wire rod generated in the drawing process, and the wire breakage rate in the drawing and stranding processes can be reduced by more than 50%.

The Chinese patent application CN109082597 discloses a hot-rolled wire rod for a cord thread with the tensile strength of 2000MPa and a production method thereof, which reduces the carbon content, improves the silicon content and the matching process, and enables the diameter of the wire rod to reach 3.0-3.5 mm on the premise of ensuring that the tensile strength is more than 4000MPa, so that the homogenization performance of the section structure of the wire rod is better, the gamma crystal grains are micronized, the aging during wire drawing processing is inhibited, and the fracture of a cementite is inhibited; and the strength and the wire drawing limit of the wire are improved, the number of times of strand twisting and wire breaking is not more than 2 per ton of steel, and the secondary processing of a user can be omitted and simplified, so that the production cost is reduced and the production efficiency is improved.

The Chinese patent application CN111534753 provides a chromium alloyed cord steel wire rod and a production process thereof, wherein microalloying is adopted, the content of chromium is increased, the content of carbon and manganese are reduced to make up the performance of the wire rod and a finished steel wire, the carbon segregation of the wire rod is improved, the probability of net carbon formation is reduced, the plasticity and the processing performance of the wire rod can be improved, and the ply breakage rate of the steel wire rod cord in the processing process is reduced.

The Chinese invention patent application CN111996349 discloses a production method of a low-strength and high-elongation cord steel wire rod, which adopts the method of hot-machine rolling and properly reducing the cooling speed after spinning to produce the low-strength and high-elongation cord steel wire rod with excellent indexes, thereby not only ensuring the subsequent drawing performance of the wire rod, but also improving the fatigue performance of the product by more than 15 percent, thereby prolonging the service cycle of materials and saving more materials.

The Chinese patent application CN106480360 discloses a high-carbon steel wire rod and a control method of oxide inclusions thereof, wherein ferroalloy ferrosilicon and ferromanganese are added in the refining process, wherein the content of Ca is 0.015-0.05%, and the content of Mg is 0.02-0.05%. The oxide inclusion size of the cord steel wire rod produced by the method is not more than 15um, and the broken wire is not more than 0.4 times per ton in the production process of a 0.20mm single cord steel wire.

Chinese patent application CN110629132 discloses a coil rod for ultra-high strength steel cord and a manufacturing method thereof, the manufacturing method comprises the following steps in sequence: in the steel smelting stage, smelting molten steel with the number density of inclusions not less than 0.5/mm 2 and the size of inclusions not more than 30 mu m, wherein the number density of the inclusions is not more than 5 mu m; a casting blank stage, namely casting the molten steel tapped in the steel smelting stage into a casting blank with a central carbon segregation value of 0.92-1.08; in the cogging stage, cogging the casting blank into an intermediate blank with a central carbon segregation value of 0.95-1.05; a rolling stage, wherein the intermediate billet is rolled into the wire rod; and controlling the cooling stage, and carrying out temperature control cooling on the wire rod to obtain the wire rod with high cleanliness, high homogeneity and tensile strength of less than or equal to 1150MPa, wherein the wire rod can be used for an ultrahigh-strength steel cord with monofilament tensile strength of more than or equal to 3600MPa, and can ensure lower drawing wire breakage rate, twisting wire breakage rate and die consumption and higher yield.

The Chinese patent application CN105506479 discloses a wire rod for 70-grade cord outer winding and a production method thereof, wherein the steel comprises the following components in percentage by weight: c: 0.68-0.72%, Mn: 0.20-0.45%, Si: 0.20-0.40%, P is less than or equal to 0.010%, S is less than or equal to 0.010%, Mg: 0.0003% -0.0008%, Ca: 0.0002% -0.006%, total oxygen: 0.0015-0.0025%, Cu less than or equal to 0.05%, and the balance of iron and inevitable impurities. The method comprises the steps of refining LF at 1540-1590 ℃ for 60-120 minutes; the superheat degree of molten steel of the continuous casting tundish is not more than 30 ℃; the cooling speed of the rolled wire rod before phase change is 10-15 ℃/s, the phase change temperature is 650-670 ℃, and the wire rod coiling temperature is 250-400 ℃. The sorbite content of the produced wire rod is between 65 and 80 percent, and the wire breakage rate is not more than 0.4 times per ton.

Disclosure of Invention

The application aims to provide 82-grade cord steel with a rough wire breakage rate lower than 3 times per kiloton and a production method thereof so as to reduce the wire breakage rate of the cord steel.

The embodiment of the invention provides a production method of 82-grade cord steel with a rough wire breakage rate lower than 3 times per kiloton, which comprises the following steps:

desulfurizing molten iron to obtain desulfurized molten iron;

carrying out converter smelting on the desulfurized molten iron to obtain molten steel;

carrying out LF refining on the molten steel to obtain refined molten steel;

continuously casting the refined molten steel; obtaining a casting blank;

heating the casting blank to obtain a casting blank to be rolled;

rolling the casting blank to be rolled, and then performing controlled cooling to obtain cord steel; in the controlled cooling, when the temperature of the rolled casting blank is higher than the preset temperature, the speed of the conveying roller way is gradually increased; when the temperature of the rolled casting blank is lower than a preset temperature, the speed of the conveying roller way is gradually reduced, and the preset temperature is 650 +/-5 ℃.

Optionally, the cooling device for controlling cooling is a stelmor air cooling line, the stelmor air cooling line includes 14 groups of fan roller tables, and the initial speed of the fan roller tables is 0.8m/s ± 0.05 m/s.

Optionally, in the controlled cooling, when the ambient temperature is lower than 10 ℃, the blower roller ways from 1 st to 9 th are controlled to be gradually increased by 3% ± 0.2%, and the blower roller ways from 10 th to 14 th are controlled to be gradually decreased by 5% ± 0.2%; and when the environmental temperature is not lower than 10 ℃, controlling the 1 st to 11 th fan roller ways to gradually increase by 3% +/-0.2%, and controlling the 12 th to 14 th fan roller ways to gradually decrease by 5% +/-0.2%.

Optionally, the superheat degree of the continuous casting tundish molten steel is less than or equal to 20 ℃, the continuous casting pulling speed is 1.00-1.30 m/min, the continuous casting adopts a solidification tail end dynamic soft reduction process, and the total casting blank pressing amount is more than or equal to 15 mm.

Optionally, the desulfurization adopts a magnesium powder spraying desulfurization process, and the sulfur content in the desulfurized molten iron is less than or equal to 0.010% by mass.

Optionally, the tapping temperature of the converter smelting is 1630-1700 ℃, the tapping time of the converter smelting is not less than 4min, the bottom-blown argon time of the converter smelting is not less than 4min, the pressure of the bottom-blown argon is 0.3-0.6 MPa, and the flow rate of the bottom-blown argon is 7.0Nm³/min-10.0Nm³/min。

Optionally, the LF refining adopts CaO-SiO₂-Al₂O₃Refining slag system, controlling the slag alkalinity of LF refining to be 1.5-3.5, wherein the LF refining time is more than or equal to 28min, and blowing argon in the whole LF refining process.

Optionally, the temperature of the heating soaking section is 1100-1250 ℃, the temperature difference of the heated section is less than or equal to 30 ℃, the heating atmosphere is a reducing atmosphere, and the heating time is 125-185 min.

Optionally, the rolling start temperature is 950-1050 ℃, the rolling finish rolling temperature is 880-920 ℃, the sizing temperature is 890-930 ℃, and the rolling spinning temperature is 910-940 ℃.

Based on the same inventive concept, the embodiment of the invention also provides 82-grade cord steel with the rough wire breakage rate lower than 3 times per kiloton, the steel is prepared by the production method of the 82-grade cord steel with the rough wire breakage rate lower than 3 times per kiloton, and the chemical components of the steel comprise the following components in percentage by mass: c: 0.79% -0.83%, Si: 0.20% -0.45%, Mn: 0.45% -0.65%, P: less than or equal to 0.015%, S: less than or equal to 0.015 percent, Cu: less than or equal to 0.10 percent, Ni: less than or equal to 0.20 percent, Cr: 0.10% -0.18%, (Nb + V + Ti): less than or equal to 0.10 percent, N: less than or equal to 0.007 percent, Als: less than or equal to 0.008 percent, and the balance of Fe and inevitable impurities.

One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

the embodiment of the invention provides a production method of 82-grade cord steel with a rough wire breakage rate lower than 3 times per kiloton, which comprises the following steps: desulfurizing molten iron to obtain desulfurized molten iron; carrying out converter smelting on the desulfurized molten iron to obtain molten steel; refining the molten steel to obtain refined molten steel; continuously casting the refined molten steel; obtaining a casting blank; heating the casting blank to obtain a casting blank to be rolled; rolling the casting blank to be rolled, and then performing controlled cooling to obtain cord steel; in the controlled cooling, when the temperature of the rolled casting blank is higher than the preset temperature, the speed of the conveying roller way is gradually increased; when the temperature of the rolled casting blank is lower than a preset temperature, the speed of a conveying roller way is gradually reduced, and the preset temperature is 650 +/-5 ℃; in the rolling and cooling control process, the concept of front quick cooling and rear slow cooling is adopted for controlling through roller speed adjustment. The rapid cooling treatment is carried out above the preset temperature, so that the sufficient supercooling degree can be ensured, and the abnormal precipitation of cementite is avoided; after the temperature is preset, the growth time of pearlite can be prolonged through slow cooling, so that the distance between pearlite lamellae is larger, and iron scales are thicker and more compact. The wire rod can be ensured to have stronger plasticity due to the larger distance between pearlite lamellae, the scale can be thickened and compacted to improve the peeling integrity of the scale in the rough-drawing process, the surface scratch of the wire rod caused by the adhesion of the small scale on a rough-drawing wheel is avoided, and the surface quality of the wire rod is ensured.

The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

FIG. 1 is a flow chart of a method provided by an embodiment of the present invention;

FIG. 2 is a microstructure of a steel provided by an embodiment of the present invention in FIG. 1;

FIG. 3 is a microstructure of a steel provided by an embodiment of the present invention as shown in FIG. 2.

Detailed Description

The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.

Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

In order to solve the technical problems, the general idea of the embodiment of the application is as follows:

according to an exemplary embodiment of the present invention, there is provided a method of producing a grade 82 cord steel having a gross breakage rate of less than 3 per kiloton, the method comprising:

s1, desulfurizing molten iron to obtain desulfurized molten iron;

as an optional implementation mode, a magnesium powder spraying desulfurization process is adopted, and the outbound [ S ] is less than or equal to 0.010 percent.

S2, carrying out converter smelting on the desulfurized molten iron to obtain molten steel;

as an optional implementation mode, the tapping temperature is 1630-1700 ℃; tapping time is more than or equal to 4 min; C. mn and Si are controlled according to the lower limit of standard components; the time of bottom blowing argon is more than or equal to 4 min; argon pressure is 0.3-0.6 MPa; argon flow of 7.0-10.0 Nm³/min。

S3, carrying out LF refining on the molten steel to obtain refined molten steel;

as an alternative implementationIn the mode, the LF refining adopts CaO-SiO₂-Al₂O₃Refining the slag system, and controlling the target value of the slag alkalinity to be 1.5-3.5; the treatment time of the LF furnace is more than or equal to 28min, and argon is blown in the whole process.

S4, continuously casting the refined molten steel; obtaining a casting blank;

as an optional implementation mode, the superheat degree of the tundish molten steel is less than or equal to 20 ℃; the pulling speed is 1.00-1.30 m/min; the total reduction of the casting blank is more than or equal to 15mm by adopting a solidification tail end dynamic soft reduction process. The section size of the casting blank is 200 multiplied by 200mm, and the casting blank is specified to be 6000-6080 mm; the center segregation of the billet is less than or equal to 1.15, and direct degradation judgment is not needed.

By controlling the superheat degree and the soft reduction of the molten steel, the center segregation stability (less than or equal to 1.15) of the steel billet is ensured, and the precipitation tendency of the reticular cementite is reduced from the source.

S5, heating the casting blank to obtain a casting blank to be rolled;

as an optional implementation mode, the temperature of a soaking section for heating is 1100-1250 ℃, and the temperature difference of the cross section is less than or equal to 30 ℃; the furnace pressure is kept at micro positive pressure, and the atmosphere in the furnace is kept at weak reducing atmosphere; the furnace time is 125-185 min.

S6, rolling the casting blank to be rolled, and then performing controlled cooling to obtain cord steel; in the controlled cooling, when the temperature of the rolled casting blank is higher than the preset temperature, the speed of the conveying roller way is gradually increased; when the temperature of the rolled casting blank is lower than a preset temperature, the speed of the conveying roller way is gradually reduced, wherein the preset temperature is 650 +/-5 ℃, and the preset temperature comprises but is not limited to 645 ℃, 646 ℃, 648 ℃, 650 ℃, 652 ℃, 654 ℃ and 655 ℃, and preferably 650 ℃.

As an optional implementation mode, high-speed wire rolling is adopted for rolling, the initial rolling temperature of the high-speed wire rolling is 950-1050 ℃, the temperature of the high-speed wire rolling entering a finishing mill is 880-920 ℃, the temperature of the high-speed wire entering a reducing sizing mill is 890-930 ℃, the spinning temperature is 910-940 ℃, the outlet speed of 20 frames of pre-finishing rolling is 7.8m/s, and the diameter of a wire rod is 5.5 mm.

In this embodiment, the cooling device for controlling cooling is a stelmor air cooling line, the stelmor air cooling line is 97 meters long, and the total number of the 14 sets of fans is 210000m for # 1-4 fans³The air volume of a No. 5-10 fan is 154000m³The air volume of a No. 11-14 fan is 125000m³H is used as the reference value. The fan power turn-on condition is as follows: the 1# to 2# fans are opened by 80 percent, the 3# to 5# fans are opened by 100 percent, and the 6# and subsequent fans are opened by 80 percent; the heat preservation cover is fully opened.

The stelmor air cooling lines comprise 14 groups of roller ways, the initial speed of the roller ways is 0.8m/s, two-stage control is adopted, the front section is gradually accelerated by adopting a certain range, the wire rod is ensured to be pulled, the lap joint point is not fixed, the cooling effect is good, the wire rod rapidly generates pearlite transformation, abnormal precipitation of reticular cementite is avoided, and the pearlite transformation is completed until the surface temperature of the wire rod is reduced to 650 ℃; after the surface temperature of the wire rod is lower than 650 ℃, the rear-section roller way gradually decelerates by adopting a certain range, so that the wire rod is ensured to form a stacking effect and slowly cool, the residual stress of the wire rod is reduced, and the larger interval between pearlite pieces and the thick and solid iron scale in the wire rod tissue are ensured.

The applicant has found that the external ambient temperature affects the quality of the final steel, with different specific controls of the external environment as follows: in the control cooling, when the environmental temperature is lower than 10 ℃, the fan roller ways from 1 st to 9 th are controlled to be gradually increased by 3% +/-0.2%, and the fan roller ways from 10 th to 14 th are controlled to be gradually decreased by 5% +/-0.2%; and when the environmental temperature is not lower than 10 ℃, controlling the 1 st to 11 th fan roller ways to gradually increase by 3% +/-0.2%, and controlling the 12 th to 14 th fan roller ways to gradually decrease by 5% +/-0.2%.

In the present embodiment, the first and second electrodes are,

1) when the external environment temperature is lower than 10 ℃, the initial speed of the roller way is 0.8m/s, the extremely difference of the speeds of the No. 1-9 fan roller ways is 1.03, and the maximum speed of the No. 9 fan roller way is 1.01 m/s; the speed range of the No. 10-14 fan roller way is 0.95, and the speed of the No. 14 fan roller way is reduced to 0.78 m/s.

2) When the external environment temperature is higher than 10 ℃, the initial speed of the roller way is 0.8m/s, the extremely difference of the speeds of the 1-11 # fan roller ways is 1.03, and the maximum speed of the 11# fan roller way is 1.07 m/s; the speed range of the 12-14 # fan roller way is 0.95, and the speed of the 14# fan roller way is reduced to 0.92 m/s.

And S7, air cooling the wire rod to room temperature, and then performing coil collecting, bundling and packaging.

According to another exemplary embodiment of the present invention, there is provided a 82-grade cord steel with a rough breaking ratio of less than 3 per kiloton, the steel being manufactured by the above-mentioned method for manufacturing the 82-grade cord steel with a rough breaking ratio of less than 3 per kiloton, and the chemical composition of the steel comprises, in mass fraction: c: 0.79% -0.83%, Si: 0.20% -0.45%, Mn: 0.45% -0.65%, P: less than or equal to 0.015%, S: less than or equal to 0.015 percent, Cu: less than or equal to 0.10 percent, Ni: less than or equal to 0.20 percent, Cr: 0.10% -0.18%, (Nb + V + Ti): less than or equal to 0.10 percent, N: less than or equal to 0.007 percent, Als: less than or equal to 0.008 percent, and the balance of Fe and inevitable impurities

The 82-grade wire rod produced by the method has the tensile strength of more than or equal to 1080MPa, the elongation of more than or equal to 7 percent, the surface shrinkage of more than or equal to 35 percent, the strength same circle difference of less than or equal to 80MPa, the pearlite sheet spacing of more than or equal to 120nm, the oxide scale thickness of more than or equal to 12 mu m, the reticular cementite of less than or equal to 1.0 grade, the sorbite rate of more than or equal to 95 percent and the surface defect depth of less than or equal to 80 mu m. The rough wire breaking rate in the deep processing process is lower than 3.0 times per kiloton.

The present application of grade 82 cord steel with a rough breaking ratio of less than 3 times per kiloton and a method for producing the same will be described in detail with reference to examples, comparative examples and experimental data.

Examples and comparative examples

82 grade cord steel with a rough wire breaking rate lower than 3 times per kiloton, wherein the chemical components of the steel are shown in the following table in percentage by mass:

the production method comprises the following steps:

s1, desulfurizing molten iron to obtain desulfurized molten iron;

s2, carrying out converter smelting on the desulfurized molten iron to obtain molten steel;

s3, refining the molten steel to obtain refined molten steel;

s4, continuously casting the refined molten steel; obtaining a casting blank;

s5, heating the casting blank to obtain a casting blank to be rolled;

s6, rolling the casting blank to be rolled, and then performing controlled cooling to obtain cord steel; in the controlled cooling, when the temperature of the rolled casting blank is higher than 650 ℃, the speed of the conveying roller way is gradually increased; when the temperature of the rolled casting blank is lower than 650 ℃, the speed of the conveying roller way is gradually reduced

The specific parameters are as follows:

related experiments:

the steels obtained in examples 1 to 4 and comparative examples 1 to N were examined and the results are shown in the following table.

It should be noted that the difference of the wire rod diameter can cause the change of the mechanical property, and the wire rod diameter of the 82 grade cord steel produced by the above examples and comparative examples of the application is phi 5.5 mm.

From the above table, the rough breaking ratio of the steel prepared by the method provided by the embodiment of the present invention is less than 3.0 times/kiloton, and the comparison between the comparative examples 1 and 2 and the embodiment can result in the excessively high rough breaking ratio when the degree of superheat or the roller table speed is not within the range provided by the embodiment of the present application.

Detailed description of the drawings 2-3:

as shown in fig. 2 and 3, the microstructure of the steel prepared by the method is shown in the figure, wherein:

FIG. 1 shows the scanning electron microscope morphology of the spacing between 82-grade cord steel wire rod pearlite pieces produced by the process, the preset temperature of the process is 650 ℃, and as shown in the figure, under 50000 times of magnification, the spacing between the pearlite pieces of the wire rod can be observed to be about 185nm, which is larger than the required lower limit range (not less than 120 nm).

FIG. 2 shows the scanning electron microscope appearance of the scale of cross section of 82-grade cord steel produced by the process, the preset temperature of the process is 650 ℃, and as shown in the figure, the thickness of the scale of the wire rod can be observed to be larger than the required lower limit range (not less than 12 μm) under 1300 times of magnification.

From the figure, the microstructure of the 82-grade cord steel wire rod trial-manufactured in the process range required by the patent can meet the requirement.

One or more technical solutions in the embodiments of the present invention at least have the following technical effects or advantages:

(1) the method provided by the embodiment of the invention ensures the center segregation of the steel billet to be stable (less than or equal to 1.15) by controlling the superheat degree and the soft reduction of the molten steel, and reduces the precipitation tendency of the reticular cementite from the source;

(2) in the rolling and cooling control process, the method provided by the embodiment of the invention adopts the idea of fast cooling before 650 ℃ and slow cooling after 650 ℃ to control through the roll speed regulation. The rapid cooling treatment is carried out at the temperature of more than 650 ℃, so that the sufficient supercooling degree can be ensured, and the abnormal precipitation of cementite is avoided; after the temperature is 650 ℃, the slow cooling can prolong the growth time of pearlite, so that the space between pearlite lamellae is larger, and the iron scale is thicker and more compact. The wire rod can be ensured to have stronger plasticity due to larger distance between pearlite lamellae, the stripping integrity of the iron scale in the rough drawing process can be improved due to the thick and compact iron scale, the surface scratch of the wire rod caused by the adhesion of the fine iron scale on a rough drawing wheel is avoided, and the surface quality of the wire rod is ensured;

(3) the tensile strength of the cord steel provided by the embodiment of the invention is more than or equal to 1080MPa, the elongation is more than or equal to 7%, the surface shrinkage is more than or equal to 35%, the same circle difference of the strength is less than or equal to 80MPa, the spacing of pearlite pieces is more than or equal to 120nm, the thickness of iron scale is more than or equal to 12 mu m, the mesh cementite is less than or equal to 1.0 grade, the sorbite rate is more than or equal to 95%, and the depth of surface defects is less than or equal to 80 mu m. The rough wire breaking rate in the deep processing process is lower than 3.0 times per kiloton;

(4) the method provided by the embodiment of the invention adopts two-stage control, the front section is gradually accelerated by adopting a certain range, the wire rod is ensured to be pulled away, the lap joint point is not fixed, the cooling effect is good, the wire rod rapidly generates pearlite transformation, the abnormal precipitation of reticular cementite is avoided, and the pearlite transformation is completed until the surface temperature of the wire rod is reduced to 650 ℃; after the surface temperature of the wire rod is lower than 650 ℃, the rear-section roller way gradually decelerates by adopting a certain range, so that the wire rod is ensured to form a stacking effect and slowly cool, the residual stress of the wire rod is reduced, and the larger interval between pearlite pieces and the thick and solid iron scale in the wire rod tissue are ensured.

Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.