CN110328229B - Method for controlling thickness of scale of 70-grade cord steel wire rod suitable for mechanical descaling - Google Patents
Method for controlling thickness of scale of 70-grade cord steel wire rod suitable for mechanical descaling Download PDFInfo
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- CN110328229B CN110328229B CN201910345065.2A CN201910345065A CN110328229B CN 110328229 B CN110328229 B CN 110328229B CN 201910345065 A CN201910345065 A CN 201910345065A CN 110328229 B CN110328229 B CN 110328229B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/16—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B41/00—Guiding, conveying, or accumulating easily-flexible work, e.g. wire, sheet metal bands, in loops or curves; Loop lifters
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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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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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
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B2201/00—Special rolling modes
- B21B2201/06—Thermomechanical rolling
Abstract
The method for controlling the thickness of the scale of the 70-grade cord steel wire rod suitable for mechanical descaling comprises the following steps: conventionally smelting and casting to form a blank; heating a casting blank; descaling by high-pressure water; hot rolling; spinning; and carrying out subsequent processes. The invention can ensure the thickness of the iron scale to be within 16-25um and control Fe in the iron scale3O4The content is not more than 25%, so that the requirement of mechanical dephosphorization of customers is better met, the environment is protected, and the product performance and the quality are ensured.
Description
Technical Field
The invention relates to a steel smelting method, in particular to a smelting method for controlling the iron scale of a cord steel wire rod, which is more suitable for controlling the thickness of the iron scale of a 70-grade cord steel wire rod subjected to mechanical descaling.
Background
The tyre cord steel for automobile tyre is the most important material for producing tyre supporting skeleton-steel cord. Generally, a cord steel wire rod is subjected to rough drawing after being descaled, then is subjected to heat treatment, is plated with copper and zinc, is drawn again to be 0.15-0.38mm, and is stranded. Due to the large drawing deformation, the requirements on the surface quality of the wire rod are strict in addition to the internal quality. Especially, the thickness and the composition of the iron scale directly influence the descaling effect of the wire rod. And the grade 70 cord steel wire rod is one of the most widely used cord steel wire rods at present.
Previously, cord steel wire rods were typically descaled by acid pickling. Because the steel scale removing mode pollutes the environment, at present, the scale removing mode of a wire rod mechanical shelling is widely adopted by research and development of technicians in the technical field. However, mechanical descaling can be significantly affected by either too thin or too thick scale on the wire rod. Because the iron matrix has certain plasticity in the drawing process of mechanical shelling of the wire rod, the wire rod generates plastic deformation when receiving tensile force, and Fe attached to the iron matrix2O3、 Fe3O4The FeO layer inevitably receives additional elongation deformation, and thus additional tensile stress is generated. Due to Fe on the iron matrix2O3、Fe3O4The FeO layer has poor plasticity, and when the additional stress exceeds the allowable stress, cracks are generated in the iron oxide scale layer and the iron matrix layer, and the iron oxide scale on the outer layer is cut into isolated iron oxide scale islands. And with the increase of the elongation, the crack is expanded along the interface of the iron matrix and the iron scale, so that the iron scale falls off. Because the binding force of the thin iron scale is poor, iron oxide skin islands formed when the thin iron scale is subjected to external force are small, powdery falling is formed, the crack expansion cannot be sustained, and therefore the descaling rate is poor when the thin iron scale is mechanically descaled; the thicker iron scale has strong self-bonding force, the iron scale islands formed when external force is applied are larger, and cracks are smoothly expanded, so that the scale breaking rate is high during mechanical descaling. In addition, the scale is too thick, the mechanical descaling time is longer, the efficiency is lower, and the yield of a user is greatly influenced. It has been found that the scale formation amount and the descaling rate have a positive correlation, but when the scale formation amount per unit area exceeds a certain value, the descaling rate does not increase significantly with the increase in the scale formation amount per unit area. Therefore, the thickness of the iron scale must be controlled to be not less than 15 μm but not more than 28 μm, and the composition of the iron scale is controlled at the same time, so that the mechanical peeling efficiency of the cord steel wire rod can be greatly improved.
After retrieval: the document with Chinese patent application No. CN201610974216.7 discloses a method for controlling the scale of a hot rolling cord steel wire rod. The document is used for controlling the surface scale of a wiredrawing type cord steel hot-rolled wire rod by adopting a mechanical descaling mode, the composition and the thickness of the surface scale of the cord carbon steel hot-rolled wire rod are controlled by controlling the spinning temperature and a stelmor cooling process, and the spinning temperature is ensured to be in a temperature range of 850-870 ℃ by adjusting the water quantity of a water tank after finish rolling. From the relevant data and the practical production on site, when the spinning temperature is lower than 890 ℃, the red rust generated on the rolled steel wire rod of the cord thread cannot be completely eliminated. The reason is that the plasticity of the iron scale and the matrix is different, the iron scale and the matrix deform together and keep integrity during high-temperature rolling, the deformation of the iron scale is large during low-temperature rolling, cracks and falling are easy to generate, the matrix can be further oxidized, red rust is easy to generate under the cooling water and oxygen-enriched environment, and the higher requirements of users cannot be met.
The Chinese patent application No. CN201410282904.8 discloses an 80-grade cord steel wire rod suitable for acid cleaning and descaling, which comprises the following chemical components in percentage by weight: 0.79-0.83% of C, 0.20-0.45% of Mn, 0.20-0.35% of Si, less than or equal to 0.010% of P, less than or equal to 0.010% of S, 0.0002-0.0010% of Mg0, Al: 0.00020 to 0005 percent and less than or equal to 0.05 percent of Cu. The sulfur content of the molten iron is less than 0.005 percent; the smelting end point of the converter is less than or equal to 0.010 percent, the smelting end point of the converter is less than or equal to 0.0001 percent, the smelting end point of the converter is less than or equal to 0.0003 percent, the smelting end point of the converter is less than or equal to 0.010 percent, the smelting end point of the converter is less than or equal to 0.0001 percent. LF refining temperature is 1530-1580 ℃, and time is 60-100 min. The superheat degree of molten steel of the continuous casting tundish is less than or equal to 30 ℃. The heating time of the continuous rolling blank is 2.5-3 h, and the lower soaking temperature is 1100 +/-15 ℃; the high-pressure water descaling pressure of the billet after being taken out of the heating furnace is not lower than 15 MPa; the wire rod spinning temperature is 860-890 ℃, the finish rolling deformation rate is less than or equal to 120s < -1 >, the air cooling speed before the phase change of the wire rod is 25-28 ℃/s, and the air cooling speed in the phase change process is 2-4 ℃/s. Although the strength level of the document meets higher requirements of users, the phenomenon of red rust generation of the wire rod cannot be completely eliminated in the scale thickness control like the above document. The reason is that the plasticity of the iron scale and the matrix is different, the iron scale and the matrix deform together and keep integrity during high-temperature rolling, the deformation of the iron scale is large during low-temperature rolling, cracks and falling are easy to generate, the matrix can be further oxidized, red rust is easy to generate under the cooling water and oxygen-enriched environment, and the higher requirements of users cannot be met.
The iron oxide on the surface of the steel wire rod of the cord can be generally divided into three layers, Fe2O3、Fe3O4FeO exists in a layered mode from outside to inside, and the brittleness and the adhesive force of oxide layers with different components are different from those of a matrix. The thickness of the iron scale is greatly different due to different forming conditions, the thickness of each layer in the iron scale is different, but the appearance of each layer is fixed, the FeO layer is loose and has larger holes; the Fe3O4 layer is relatively compact and also has more defects and pores; fe2O3The layers are most compact but are extremely thin and generally not readily discernible. Furthermore, from a process point of view, the adhesion of various iron scales to metals is different, the failure stress of FeO is about 0.04kg/mm2, the failure stress of Fe3O4 is about 4kg/mm2, and Fe2O3The failure stress of (2) is about 1kg/mm 2. It follows that the most advantageous conditions for descaling should occur if the main component of the scale of the wire rod is FeO and the Fe content in the scale should be minimized3O4The content of (a).
Therefore, the thickness and the structure of the scale of the widely used 70-grade cord steel wire rod are controlled, the effect of mechanical descaling of downstream users is met, and the method has very practical significance.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides the iron scale with the thickness controlled between 16 and 25um and Fe in the iron scale3O4The content is not more than 25 percent, the smelting method is environment-friendly, ensures the product performance and quality and is suitable for controlling the scale of the 70-grade cord steel wire rod subjected to mechanical descaling.
The measures for realizing the aim are as follows:
the smelting method for controlling the thickness of the scale of the 70-grade cord steel wire rod suitable for mechanical descaling comprises the following steps:
1) conventionally smelting and casting to form a blank;
2) heating the casting blank, controlling the temperature of a soaking section to be 1030-1130 ℃, and controlling the heating time to be 100-;
3) descaling by high-pressure water until the surface of the casting blank is clean;
4) carrying out hot rolling, and controlling the initial rolling temperature of rough rolling to be 980-1040 ℃; performing conventional finish rolling;
5) carrying out a spinning process: during the period, the spinning temperature is controlled to be 930-950 ℃, and the outlet speed of a stelmor line roller way is reduced to 35-45 m/min; during air cooling, turning off 20-30% of the total air volume; covering the part which accounts for 20-30% of the whole heat-insulating cover when the heat-insulating cover is used for heat insulation;
6) and carrying out subsequent processes.
It is characterized in that: the 70-grade cord steel wire rod comprises the following components in percentage by weight: c: 0.69 to 0.75 wt%, Si: 0.15 to 0.30 wt%, Mn: 0.40-0.60 wt%, P is less than or equal to 0.025 wt%, S is less than or equal to 0.015 wt%, P + S is controlled to be less than or equal to 0.030 wt%, and the balance is Fe and inevitable impurities.
Preferably: the initial rolling temperature of rough rolling is 990-1025 ℃.
Preferably: the spinning temperature is 935-945 ℃, and the exit speed of a stelmor line roller way is reduced to 36-42 m/min.
The reason why the spinning temperature is controlled to be 930-950 ℃, preferably 935-945 ℃ in the invention is that after the wire rod is finally rolled, the purpose of increasing the spinning temperature is to accelerate the oxidation speed at a high temperature state and convert a large amount of Fe into FeO and Fe3O4And the total thickness of the iron scale is increased. The spinning temperature is too low, and Fe is easily formed in iron scale2O3And (4) organizing. Over-high spinning temperature, Fe in iron scale3O4The proportion of tissue will increase. The range of the spinning temperature is controlled, and the Fe in the iron scale on the surface of the 70-grade cord steel wire rod can be ensured3O4The tissue proportion is controlled below 25%.
The invention reduces the exit speed of the stelmor line roller way to 35 to 45 m/min; when air cooling is carried out, 20-30% of the total air volume is turned off, and when the heat preservation cover is used for preserving heat, the part which accounts for 20-30% of the total heat preservation cover is covered, because the FeO is prevented from being converted into Fe in a large amount at a low-temperature stage of about 600 DEG C3O4Occurs. Simultaneously, the speed of the roller way after phase change is reduced, so that the wire rod is positioned inThe roller way retention time is prolonged, the cooling time is correspondingly prolonged, the wire rod is cooled more sufficiently, the cooling speed can be improved, and FeO → Fe in the iron oxide is reduced3O4+ Fe conversion, lowering Fe3O4The content of the iron oxide scale is increased, and meanwhile, the cooling time is prolonged, so that the thickness of the iron oxide scale can be ensured to be within the range of 16-25um, and the requirement of downstream users on mechanical descaling can be better met.
Compared with the prior art, the invention ensures the thickness of the iron scale to be within the range of 16-25um, and can also control Fe in the iron scale3O4The content is not more than 25%, the requirement of mechanical descaling of customers is better met, and the environment is protected, and the product performance and quality are ensured.
Detailed Description
The present invention is described in detail below:
table 1 is a list of chemical ingredient values for each example of the present invention;
table 2 is a list of main process values for each example and comparative example of the present invention;
table 3 shows the scale detection of each example of the present invention and the comparative example.
The method comprises the following steps of:
1) conventionally smelting and casting to form a blank;
2) heating the casting blank, controlling the temperature of a soaking section to be 1030-1130 ℃, and controlling the heating time to be 100-;
3) descaling by high-pressure water until the surface of the casting blank is clean;
4) carrying out hot rolling, and controlling the initial rolling temperature of rough rolling to be 980-1040 ℃; performing conventional finish rolling;
5) carrying out a spinning process: during the period, the spinning temperature is controlled to be 930-950 ℃, and the outlet speed of a stelmor line roller way is reduced to 35-45 m/min; during air cooling, turning off 20-30% of the total air volume; covering the part which accounts for 20-30% of the whole heat-insulating cover when the heat-insulating cover is used for heat insulation;
6) and carrying out subsequent processes.
TABLE 1 tabulated (wt%) chemical composition values for each example of the invention and comparative example
TABLE 2 Main Process parameters of examples of the invention and comparative examples
Note: comparative examples 1 and 2 were produced using the components of examples 7 and 8 in table 1.
TABLE 3 detection of scale in examples of the invention and comparative examples
As can be seen from table 3, when the heating time, the heating temperature, and the rough rolling start temperature were approximately equivalent, the thickness of the scale of the obtained wire rod was only 12.7um and red rust occurred in the wire rod at a spinning temperature of 886 ℃ by controlling the roller speed and the air volume. And when other processes are approximately the same, when the spinning temperature is only increased to 955 ℃, the obtained wire rod has no red rust phenomenon, but the thickness of the iron scale is higher than 28um, and the requirement of a user cannot be met.
Claims (3)
1. The method for controlling the thickness of the scale of the 70-grade cord steel wire rod suitable for mechanical descaling comprises the following steps:
1) conventionally smelting and casting to form a blank;
2) heating the casting blank, controlling the temperature of a soaking section to be 1030-1130 ℃, and controlling the heating time to be 135-plus-material 200 min;
3) descaling by high-pressure water until the surface of the casting blank is clean;
4) carrying out hot rolling, and controlling the initial rolling temperature of rough rolling to be 980-1040 ℃; performing conventional finish rolling;
5) carrying out a spinning process: during the process, the spinning temperature is controlled to be 936-950 ℃, and the outlet speed of a stelmor line roller way is reduced to 35-45 m/min; during air cooling, turning off 20-30% of the total air volume; covering the part which accounts for 20-30% of the whole heat-insulating cover when the heat-insulating cover is used for heat insulation;
6) and carrying out subsequent processes.
2. The method of controlling scale thickness in a grade 70 cord steel wire rod for mechanical descaling of claim 1 wherein: the 70-grade cord steel wire rod comprises the following components in percentage by weight: c: 0.69 to 0.75 wt%, Si: 0.15 to 0.30 wt%, Mn: 0.40-0.60 wt%, P is less than or equal to 0.025 wt%, S is less than or equal to 0.015 wt%, P + S is controlled to be less than or equal to 0.030 wt%, and the balance is Fe and inevitable impurities.
3. The method of controlling scale thickness in a grade 70 cord steel wire rod for mechanical descaling of claim 1 wherein: the initial rolling temperature of rough rolling is 990-1025 ℃.
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| CN201910345065.2A CN110328229B (en) | 2019-04-26 | 2019-04-26 | Method for controlling thickness of scale of 70-grade cord steel wire rod suitable for mechanical descaling |
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| CN113637907B (en) * | 2021-07-30 | 2022-08-26 | 武汉钢铁有限公司 | Production method of 72-grade cord steel with coarse breaking rate lower than 1.0 per kiloton |
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| CN101235476A (en) * | 2008-01-08 | 2008-08-06 | 江苏沙钢集团有限公司 | Technique for controlling hot rolling rod bundle surface iron scale |
| CN102896159B (en) * | 2011-07-29 | 2015-09-23 | 宝钢集团新疆八一钢铁有限公司 | Reduce the rolling process for cooling of wire drawing low-carbon steel rod bundle iron scale |
| CN102534094B (en) * | 2012-01-01 | 2013-05-22 | 首钢总公司 | Method for producing tire cord steel wire by converter billet continuous casting process |
| CN105132610B (en) * | 2015-08-26 | 2017-11-21 | 武汉钢铁有限公司 | The production method for controlling the high-end cord steel titanium of thin specification to be mingled with |
| CN105624564B (en) * | 2016-01-05 | 2017-10-27 | 江阴兴澄特种钢铁有限公司 | A kind of excellent carbon steel wire rod with high of fine steel cord drawing processing characteristics and manufacture method |
| CN106269934B (en) * | 2016-09-21 | 2018-07-17 | 邢台钢铁有限责任公司 | The flexible control method of cord steel iron scale quality |
| CN108237146A (en) * | 2017-12-07 | 2018-07-03 | 江苏省沙钢钢铁研究院有限公司 | A kind of method for improving cord steel oxide skin stripping performance |
| CN109082597A (en) * | 2018-09-05 | 2018-12-25 | 武汉钢铁有限公司 | A kind of tensile strength is 2000MPa grades of cord gren rods and production method |
| CN109023074B (en) * | 2018-09-05 | 2020-01-14 | 武汉钢铁有限公司 | Hot-rolled wire rod for cord thread with tensile strength of 4000MPa and production method |
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