Method for controlling segregation and net carbon of ultrahigh-strength 92-grade tire cord steel

Abstract

The invention provides an ultrahigh-strength 92-grade tire cord steel segregation and net carbon control method which comprises the following steps: (1) continuous casting cooling: molten steel meeting the chemical component requirements of 92-grade tire cord steel is continuously cast into a continuous casting billet, the continuous casting billet is cooled by adopting an aerial fog weak cooling process method, and the secondary cooling specific water flow is 0.20-0.40 L / kg; (2) electromagnetic stirring: adopting crystallizer electromagnetic stirring with high electromagnetic intensity and tail end electromagnetic stirring on the section of the continuous casting billet; (3) continuous casting pulling speed: casting a continuous casting blank at a low pulling speed; (4) continuous casting light and heavy reduction: carrying out large reduction and multi-rack continuous reduction on the section of the continuous casting billet; and (5) heating the continuous casting billet: increasing the heating temperature of the continuous casting billet to 1200 DEG C or above, and prolonging the heating time of the continuous casting billet to 180 minutes or above. The segregation index is reduced to 1.06 from the original 1.20, the qualified rate of wire rod net carbon is increased to 99% or above from the original 95%, and the wire breakage rate of customer processing is reduced to 2.5 times / ton from the original 4.5 times / ton.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wire rod production, in particular to a segregation and network carbon control method for super-high-strength 92-grade cord steel. BACKGROUND

[0002] The original super-high-strength 92-grade cord steel is produced by adopting a small billet 160*160 continuous casting process and a corresponding rolling process, and the conventional segregation and network carbon control method for the super-high-strength 92-grade cord steel has unstable core quality, too high segregation and network carbon levels, which leads to high wire breakage rate of customers and cannot meet batch production. SUMMARY

[0003] In view of the deficiencies in the prior art, the present application provides a segregation and network carbon control method for super-high-strength 92-grade cord steel.

[0004] The present application achieves the above technical purpose through the following technical means.

[0005] A segregation and network carbon control method for super-high-strength 92-grade cord steel, comprising the following steps:

[0006] (1) Continuous casting cooling: molten steel with 92-grade cord steel chemical composition requirements is continuously cast into a continuous casting billet, and the continuous casting billet cooling adopts a gas mist weak cooling process method, and the secondary cooling water quantity is 0.20-0.40 L / kg;

[0007] (2) Electromagnetic stirring: the continuous casting billet section adopts high electromagnetic intensity crystallizer electromagnetic stirring and end electromagnetic stirring;

[0008] (3) Continuous casting speed: the continuous casting billet is poured by low casting speed;

[0009] (4) Continuous casting light and heavy reduction: large reduction amount and multi-rack continuous reduction are adopted for the continuous casting billet section;

[0010] (5) Continuous casting billet heating: the continuous casting billet heating temperature is increased to above 1200℃, and the continuous casting billet heating time is prolonged to above 180 minutes.

[0011] Further, the 92-grade cord steel chemical composition weight percentage is: C: 0.89-0.96%, Mn: 0.20-0.50%, Si: 0.10-0.30%, Cr: 0.10-0.30%, P≤0.015%, S≤0.010%, Ni≤0.05%, Cu≤0.05%, Mo≤0.03%, Al≤0.003%.

[0012] Further, the continuous casting billet section specification is 200*240mm 2 .

[0013] Further, the current intensity of the electromagnetic stirring of the crystallizer is 550 A, and the current frequency is 3 HZ.

[0014] Further, the current intensity of the terminal electromagnetic stirring is 600 A, and the current frequency is 10 HZ.

[0015] Further, the drawing speed is ≤1.3 m / min.

[0016] Further, the reduction is greater than 10% of the thickness of the continuous casting billet.

[0017] Further, the number of passes of the multi-stand reduction is 6 passes.

[0018] The present application has the following beneficial effects:

[0019] The present application improves the segregation of the continuous casting billet from the source by using the innovative combination method of the 200*240 square continuous casting gas mist cooling, low drawing speed, electromagnetic stirring, light and heavy reduction, etc., and improves the segregation of the rod and the mesh carbon by prolonging the heating time and improving the heating temperature of the continuous casting billet. Compared with the original process, the segregation index is reduced from 1.20 to 1.06, the rod mesh carbon qualification rate is improved from 95% to more than 99%, the customer processing wire breakage rate is reduced from 4.5 times / ton to 2.5 times / ton, and the batch application of the ultra-high strength steel cord is realized. DETAILED DESCRIPTION

[0020] The present application will be further described below in conjunction with specific embodiments, but the scope of protection of the present application is not limited thereto.

[0021] A segregation and mesh carbon control method of an ultra-high strength 92 grade cord steel includes the following steps:

[0022] 1) Component control: The chemical component of the 92 grade cord steel YLX92A is as follows: C: 0.89-0.96%, Mn: 0.20-0.50%, Si: 0.10-0.30%, Cr: 0.10-0.30%, P≤0.015%, S≤0.010%, Ni≤0.05%, Cu≤0.05%, Mo≤0.03%, and Al≤0.003%.

[0023] 2) Continuous casting cooling: The molten steel with the chemical component requirement of the 92 grade cord steel is continuously cast into a continuous casting billet with a section size of 200*240 mm 2 , the continuous casting billet cooling adopts the gas mist weak cooling process method, the secondary cooling water quantity is 0.20-0.40 L / kg, and the continuous casting billet cooling is more uniform.

[0024] 3) Electromagnetic stirring: The continuous casting billet 200*240 mm 2The cross section adopts crystallizer electromagnetic stirring with higher electromagnetic intensity (current intensity of 550 A, current frequency of 3 HZ) and end electromagnetic stirring (current intensity of 600 A, current frequency of 10 HZ).

[0025] 4) Casting speed: The continuous casting billet is cast by low casting speed (≤1.3 m / min), so that the macrostructure of the continuous casting billet is more uniform, the center porosity and segregation degree are lighter, and suitable solid phase rate (50-80%) of the casting billet is obtained, the best light and heavy pressing position is obtained, so as to reduce the carbon segregation index.

[0026] 5) Light and heavy pressing of continuous casting: the continuous casting billet 200*240mm 2 is pressed by large pressing amount (the pressing amount is greater than 10% of the thickness of the continuous casting billet), multi-rack (6 times of pressing), so that the solute elements are homogenized and distributed, so as to realize the reduction of the carbon segregation index.

[0027] 6) Heating of continuous casting billet: by increasing the heating temperature to above 1200℃ and prolonging the heating time to above 180 minutes, the carbon element of the continuous casting billet is fully diffused, so as to further reduce the segregation, and reduce the carbon level of the final finished wire rod.

[0028] Compared with the conventional process control method, the technical indexes of the super high strength cord steel YLX92A wire rod and the user processing performance are expected to have the following effects:

[0029] (1) The average carbon segregation index of YLX92A continuous casting billet can be reduced from 1.20 to 1.06.

[0030] (2) The qualified rate of the net carbon of YLX92A is increased from 95% to more than 99%.

[0031] (3) The average wire breaking rate of customer processing can be reduced from 4.5 times / ton to 2.5 times / ton.

[0032] Example 1

[0033] 1) Composition control: the chemical composition of the 92-grade cord steel YLX92A is as follows: C: 0.92%, Mn: 0.35%, Si: 0.20%, Cr: 0.18%, P: 0.010%, S: 0.004%, Ni: 0.007%, Cu: 0.008%, Mo: 0.003%, Al: 0.0007%.

[0034] 2) Continuous casting cooling: the molten steel with the chemical composition requirements of the 92-grade cord steel is continuously cast into a continuous casting billet with a cross section size of 200*240mm 2 , and the continuous casting billet cooling adopts the gas mist weak cooling process method, the secondary cooling water quantity is 0.30 L / kg, and the continuous casting billet cooling is more uniform.

[0035] 3) Electromagnetic stirring: continuous casting billet 200*240mm 2 The cross section adopts crystallizer electromagnetic stirring with higher electromagnetic intensity (current intensity is 550 A, current frequency is 3 HZ) and end electromagnetic stirring (current intensity is 600 A, current frequency is 10 HZ).

[0036] 4) Continuous casting speed: the continuous casting billet is cast by low speed (1.30 m / min) so that the macrostructure of the continuous casting billet is more uniform, the center porosity and segregation degree are lighter, and suitable solid phase rate (60%) of the casting billet is obtained to get the best light and heavy pressing position, thereby reducing the carbon segregation index.

[0037] 5) Continuous casting light and heavy pressing: the continuous casting billet 200*240mm 2 is pressed by adopting large pressing amount (the pressing amount is greater than 10% of the thickness of the continuous casting billet) and multi-rack (6 times of pressing amount are 2mm / 3mm / 4mm / 5mm / 5mm / 3mm) continuous pressing, so that the solute elements are homogenized and distributed, thereby realizing the reduction of the carbon segregation index.

[0038] 6) Continuous casting billet heating: heating temperature: 1210℃, heating time: 201 minutes, so that the carbon element of the continuous casting billet is fully diffused, thereby further reducing the segregation.

[0039] Based on the steps of example 1, the following results are obtained:

[0040] (1) The average carbon segregation index of YLX92A continuous casting billet is reduced from 1.20 to 1.06.

[0041] (2) The qualified rate of YLX92A net carbon is increased from 95% to 99.4%.

[0042] (3) The average wire breaking rate of customer processing is reduced from 4.5 times / ton to 2.32 times / ton.

[0043] Example 2

[0044] 1) Composition control: the chemical composition of 92-grade cord steel YLX92A is as follows: C: 0.93%, Mn: 0.37%, Si: 0.22%, Cr: 0.20%, P: 0.009%, S: 0.005%, Ni: 0.008%, Cu: 0.010%, Mo: 0.002%, Al: 0.0008%.

[0045] 2) Continuous casting cooling: the molten steel with the chemical composition requirements of 92-grade cord steel is continuously cast into a continuous casting billet with a cross-sectional size of 200*240mm 2 , and the continuous casting billet cooling adopts the gas mist weak cooling process method, the secondary cooling water quantity is 0.28 L / kg, and the continuous casting billet cooling is more uniform.

[0046] 3) Electromagnetic stirring: CCM 200*240mm 2 The cross section adopts crystallizer electromagnetic stirring with higher electromagnetic intensity (current intensity is 550 A, current frequency is 3 HZ) and end electromagnetic stirring (current intensity is 600 A, current frequency is 10 HZ).

[0047] 4) CCM casting speed: The CCM is cast by low casting speed (1.25 m / min) to make the macrostructure of the CCM more uniform, the center porosity and segregation degree lighter, and at the same time, the suitable solid phase rate (70%) of the CCM is obtained, the best light and heavy pressing position is obtained, thereby reducing the carbon segregation index.

[0048] 5) CCM light and heavy pressing: The CCM 200*240mm 2 The cross section adopts large pressing amount (the pressing amount is greater than 10% of the thickness of the CCM) and multi-rack (6 times of pressing amount are 1 mm / 2 mm / 4 mm / 5 mm / 5 mm / 5 mm) continuous pressing, so that the solute elements are homogenized and distributed, thereby realizing the reduction of the carbon segregation index.

[0049] 6) CCM heating: heating temperature: 1230℃, heating time: 210 minutes, so that the carbon element of the CCM is fully diffused, thereby further reducing the segregation. Thus further reducing the segregation, while reducing the carbon level of the final finished wire rod net.

[0050] Based on the steps of example 2, the following results are obtained:

[0051] (1) The average carbon segregation index of YLX92A CCM is reduced from 1.20 to 1.04.

[0052] (2) The carbon net pass rate of YLX92A is increased from 95% to more than 99.4%.

[0053] (3) The average wire breaking rate of customer processing is reduced from 4.5 times / ton to 2.4 times / ton.

[0054] Example 3

[0055] 1) Composition control: The chemical composition of 92-grade cord steel YLX92A is: C: 0.91%, Mn: 0.38%, Si: 0.23%, Cr: 0.19%, P: 0.008%, S: 0.003%, Ni: 0.009%, Cu: 0.011%, Mo: 0.004%, Al: 0.0006%.

[0056] 2) CCM cooling: The molten steel with the chemical composition requirements of 92-grade cord steel is continuously cast into a cross-sectional size of 200*240mm 2The continuous casting billet is cooled by a gas mist weak cooling process, and the secondary cooling water quantity is 0.25 L / kg, so the continuous casting billet is cooled more uniformly.

[0057] 3) electromagnetic stirring: continuous casting billet 200*240mm 2 The crystallizer electromagnetic stirring (current intensity is 550 A, and current frequency is 3 HZ) and the end electromagnetic stirring (current intensity is 600 A, and current frequency is 10 HZ) with higher electromagnetic intensity are adopted.

[0058] 4) continuous casting speed: the continuous casting billet is poured by low casting speed (1.20 m / min), so that the macrostructure of the continuous casting billet is more uniform, the center porosity and segregation degree are lighter, and the suitable solid phase rate (75%) of the continuous casting billet is obtained, the best light and heavy pressing position is obtained, and the carbon segregation index is reduced.

[0059] 5) continuous casting light and heavy pressing: the continuous casting billet 200*240mm 2 The large pressing amount (the pressing amount is greater than 10% of the thickness of the continuous casting billet), multi-rack (6 times of pressing amount are 2 mm / 3 mm / 4 mm / 5 mm / 5 mm / 5 mm) continuous pressing are adopted, so that the solute element is homogenized and distributed, and the carbon segregation index is reduced.

[0060] 6) continuous casting billet heating: heating temperature is 1240 ℃, and heating time is 208 minutes, so that the carbon element of the continuous casting billet is fully diffused, and the segregation is further reduced. The segregation is further reduced, and the final finished product wire net carbon level is reduced.

[0061] Based on the steps of example 3, the following results are obtained:

[0062] (1) The average carbon segregation index of YLX92A continuous casting billet is reduced from 1.20 to 1.054.

[0063] (2) The net carbon qualified rate of YLX92A is increased from 95% to more than 99.5%.

[0064] (3) The average wire breaking rate of customer processing is reduced from 4.5 times / ton to 2.5 times / ton.

[0065] The example is a preferred embodiment of the present application, but the present application is not limited to the above-mentioned embodiment, any obvious improvement, replacement or modification made by those skilled in the art without departing from the essential content of the present application belongs to the protection scope of the present application.

Claims

1. A method for controlling segregation and mesh carbon of extra-high strength 92 grade cord steel, characterized in that, It comprises the following steps: (1) continuous casting cooling: melt with the chemical composition of 92 grade cord steel is cast into continuous casting billet, the cooling of continuous casting billet adopts the weak cooling process method of gas mist, the specific water consumption of secondary cooling is 0.20-0.40 L / kg; (2) electromagnetic stirring: the cross section of continuous casting billet adopts high electromagnetic intensity of crystallizer electromagnetic stirring and end electromagnetic stirring; (3) continuous casting speed: the continuous casting billet is cast by low casting speed; (4) continuous casting light and heavy press down: the cross section of continuous casting billet adopts large press down amount and multiple rack continuous press down; (5) continuous casting billet heating: the heating temperature of continuous casting billet is increased to above 1200℃, and the heating time of continuous casting billet is prolonged to above 180 minutes.

2. The method for controlling segregation and network carbon of the extra-high strength 92-grade cord steel according to claim 1, characterized in that, The chemical composition of 92 grade cord steel is as follows: C: 0.89-0.96%, Mn: 0.20-0.50%, Si: 0.10-0.30%, Cr: 0.10-0.30%, P≤0.015%, S≤0.010%, Ni≤0.05%, Cu≤0.05%, Mo≤0.03%, Al≤0.003%.

3. The method for controlling segregation and network carbon of the extra-high strength 92-grade cord steel according to claim 1, characterized in that, The continuous casting billet section size is 200*240mm 2 .

4. The method for controlling segregation and network carbon of the extra-high strength 92-grade cord steel according to claim 1, characterized in that, The current intensity of crystallizer electromagnetic stirring is 550 A, and the current frequency is 3HZ.

5. The method for controlling segregation and network carbon of the extra-high strength 92-grade cord steel according to claim 1, characterized in that, The current intensity of end electromagnetic stirring is 600 A, and the current frequency is 10HZ.

6. The method for controlling segregation and network carbon of high strength 92-grade cord steel according to claim 1, characterized in that, The casting speed is ≤1.3 m / min.

7. The method for controlling segregation and network carbon of high strength 92-grade cord steel according to claim 1, characterized in that, The press down amount is greater than 10% of the thickness of continuous casting billet.

8. The method for controlling segregation and network carbon of high strength 92-grade cord steel according to claim 1, characterized in that, The press down times of multiple rack is 6 times.