Preparation method of high-corrosion-resistance rare earth phosphorized high-strength steel BT170P1 cold-rolled steel strip

Abstract

The invention discloses a preparation method of a high-corrosion-resistance rare earth phosphorized high-strength steel BT170P1 cold-rolled steel strip, which comprises the steps of smelting, heating, rough rolling, finish rolling, acid rolling, continuous annealing, leveling and the like, the cold-rolled steel strip with good stamping forming performance is finally obtained, and the microstructure of the steel plate is mainly ferrite. By executing the smelting and continuous casting narrow window control process and the adding time and adding method of the rare earth, the condition of high purity of molten steel can be achieved, and the content of the rare earth in the steel can be precisely hit. According to the process, parameters are accurately controlled, the action effect of rare earth in steel can be exerted, and improvement of the corrosion resistance of the steel plate by the process is controlled.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgical materials, and particularly relates to a preparation method of a cold-rolled steel strip of high corrosion-resistant rare-earth and phosphorus-added high-strength steel BT170P1. Background Art

[0002] Cold-rolled products of IF steel are mostly used for automotive parts with large deformation and complex structures, and automobile manufacturers usually have multiple automobile assembly production lines. Therefore, some automobile companies' shearing and distribution production lines transport the stamped parts or white bodies to the assembly bases in other regions by sea or other means. Some automobile companies mostly transport automobile parts to overseas countries for assembly by sea. During the transportation process, they will be exposed to marine atmosphere. Due to the large amount of salt in the environment, long transportation distance and time, and the fact that the cold-rolled products have no coating on the surface, corrosion, rust spots and other phenomena are likely to occur on the product surface. In addition, one of the R & D tasks in the automotive industry is to extend the service life of automobile bodies. There are usually three factors causing automobile aging: corrosion, collision and wear, among which corrosion aging is the most common and serious. The present invention studies the influence of rare-earth Ce on the size and quantity of MnS inclusions in aluminum-deoxidized IF steel through industrial tests, reduces the corrosion active points on the matrix, and reduces the corrosion reaction rate, providing technical guidance for industrial application to further improve the cleanliness control of phosphorus-added high-strength steel products through new ways. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation method of a cold-rolled steel strip of high corrosion-resistant rare-earth and phosphorus-added high-strength steel BT170P1, so that the steel plate has good corrosion resistance.

[0004] The method of the present invention uses medium-thick slab continuous casting billets as hot-rolled raw materials, and conducts processes such as heating, rough rolling, finish rolling, acid rolling, continuous annealing and tempering, etc., and finally obtains a cold-rolled steel strip with good stamping formability. The microstructure of the steel plate is mainly ferrite.

[0005] Through test detection, the r90 value representing the formability index is detected. The average r90 value of the steel plate with rare-earth addition is 2.05, and the average r90 value of the product without rare-earth addition is 1.91.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A preparation method of a cold-rolled steel strip of high corrosion-resistant rare-earth and phosphorus-added high-strength steel BT170P1 of the present invention includes the following steps:

[0008] Smelting and continuous casting: The hot metal is subjected to desulfurization pretreatment. The requirement for the slag cleaning area of the hot metal is greater than 95%. The sulfur content of the hot metal entering the converter is required to be less than 0.002%. During the tapping process of the converter, argon is turned on at the 1 / 4 moment, and then the ladle top slag operation is carried out first. 4.5 - 5.5 kg / t of quicklime and an appropriate amount of slag-forming agent are added using a feeding chute. The amount of quicklime added is calculated according to the converter tonnage to form the ladle top slag; after the converter tapping is completed, 0.3 - 0.5 kg / t of aluminum pellets are added to modify the top slag; after the decarbonization, deoxidation, and alloying in the RH process are completed, 0.15 - 0.20 kg / t of aluminum pellets are added to modify the top slag; RH furnace vacuum degassing is carried out, and deep decarbonization treatment is carried out according to the in-place composition and temperature of the RH molten steel; after decarbonization is completed, after circulating for more than 4 minutes, ferro-manganese, ferrophosphorus, and ferrotitanium alloys are added to adjust the composition. After the composition adjustment is completed, ensure that the vacuum degree is maintained below 80 Pa and circulate for more than 5 minutes. When the active oxygen in the steel is ≤ 3 ppm before breaking the vacuum, according to the actual molten steel amount, a commercially available ferroalloy containing 30% rare earth lanthanum and cerium is added as required, and the vacuum is circulated for more than 2 minutes before starting to break the vacuum; the continuous caster adopts constant casting speed control, and the casting speed range is 1.2 - 1.6 m / min. The protective casting is adopted during the casting process of the continuous caster;

[0009] Heating and hot rolling process:

[0010] (1) For finished product thickness ≤ 3.0 mm: The heating furnace temperature is controlled at 1180°C - 1220°C, the soaking temperature of the heating furnace is 1190°C - 1230°C, the residence time in the furnace is 180 - 240 min, the soaking time is 30 - 60 min, and the slab outlet temperature is 1200°C - 1240°C;

[0011] (2) For finished product thickness > 3.0 mm: The heating furnace temperature is controlled at 1180°C - 1210°C, the soaking temperature of the heating furnace is 1190°C - 1220°C, the residence time in the furnace is 180 - 240 min, the soaking time is 30 - 60 min, and the slab outlet temperature is 1190°C - 1230°C;

[0012] After high-pressure water descaling, rolling is carried out. The rough rolling starting temperature is 1150°C - 1800°C, the finishing rolling temperature is 895°C - 925°C, and the coiling temperature is 620°C - 635°C;

[0013] Acid rolling process: The acid rolling rolling schedules for different thicknesses are carried out according to the following table:

[0014] Final thickness (mm) Raw material thickness (mm) Final thickness ≥ 0.70 and < 0.80 3.5 Final thickness ≥ 0.80 and < 0.90 3.8 Final thickness ≥ 0.90 and < 1.00 4.0 Final thickness ≥ 1.00 and < 1.20 4.3 Final thickness ≥ 1.20 and < 1.50 4.5 Final thickness ≥ 1.50 and < 1.80 5.0 Final thickness ≥ 1.80 and < 2.00 5.5

[0015] Annealing process: The annealing process is carried out according to the following table:

[0016]

[0017] Production process speed requirements:

[0018] Thickness (mm) Speed (m / min) ≥0.7-<1.1 150±15 ≥1.1-<1.5 110±15 ≥1.5-<2.0 100±15

[0019] Levelling process:

[0020] Thickness (mm) Skin pass elongation (%) Thickness ≥ 0.7 and < 1.1 0.6±0.05 Thickness ≥ 1.1 and < 2.0 0.7±0.05 。

[0021] Furthermore, 5 kg / t of quicklime and an appropriate amount of slag formers are added using a blanking chute.

[0022] Furthermore, according to the actual molten steel amount, a commercially available ferroalloy containing 30% rare earth lanthanum and cerium is added at 0.2 kg per ton of steel.

[0023] Furthermore, in the annealing process: when the thickness difference is equal to 1.0 times, the outlet temperature control range of the heating section and soaking section is required to be ±10°C; when the thickness difference exceeds 1.0 times, the outlet temperature control range of the heating section and soaking section is required to be ±15°C.

[0024] Furthermore, the chemical composition design scheme of the steel strip by mass percentage is as follows:

[0025] C ≤ 0.0030%, Si: 0.030 - 0.070%, Mn: 0.055 - 0.065%, P: 0.040 - 0.055%, S ≤ 0.0090%, Ti: 0.040 - 0.060%, Al: 0.030 - 0.070%, Ce: 0.0015 - 0.025%, N ≤ 0.004%, O ≤ 0.003%, and the rest is iron and other inevitable impurities.

[0026] Furthermore, through experimental detection, the r90 value representing the formability index is detected, and the average r90 value of the rare earth-added steel strip is 2.05.

[0027] Furthermore, the specific process of this method can more effectively exert the effect of rare earth in steel and improve the corrosion resistance of the steel plate.

[0028] Compared with the prior art, the beneficial technical effects of the present invention:

[0029] Implementing the smelting, continuous casting narrow window control process, the addition timing and addition method of rare earth described in the present invention can achieve the condition of higher purity of molten steel and the method of accurately hitting the rare earth content in steel. The precisely controlled parameters of the hot rolling and cold rolling processes described in the present invention can exert the effect of rare earth in steel and control the improvement of the corrosion resistance of the steel plate.

[0030] When rare earth Ce is added to steel, Ce combines with active O and S in the steel to have a lower Gibbs free energy and is extremely easy to form CeAlO3 and Ce2O2S. On the other hand, when rare earth Ce is added, it first combines with S in the steel and precipitates earlier than MnS during solidification, forming small-sized spherical inclusions, which can significantly reduce the size and quantity of MnS inclusions at each position of the continuous casting billet, thereby reducing the probability of matrix corrosion induced by MnS inclusions in the steel. In addition, the cerium-containing inclusions are spherical in shape and have no tip positions, with better fusion with the steel matrix. The passivation film at the interface between the inclusions and the matrix is not easily damaged by erosive ions, reducing the corrosion active sites on the matrix. At the same time, rare earth can make the inclusions in the steel evenly distributed, effectively reducing the anode area, thus greatly reducing the probability of matrix corrosion induced by inclusions. Rare earth in steel generates Ce 3+ ions during the corrosion process, and these rare earth ions combine with SO4 2- generated during the corrosion process to form insoluble rare earth sulfates covering the anode. Ce 3+ can be oxidized to Ce 4 + , and Ce 4+ is a strong oxidant, and its oxidation ability is greater than that of oxygen in the air. It can oxidize Fe 2+ to Fe 3+ , and Ce 4+ is reduced to Ce 3+ . Not only does it promote the formation of stable iron phosphates, but rare earth ions also form colloidal precipitates of rare earth phosphates or rare earth dihydrogen phosphates with H3PO4 at pH = 4 - 5, covering the anode together with various insoluble phosphates, preventing the dissolution of iron, thereby slowing down the corrosion of the matrix.

[0031] The present invention effectively adopts the action of rare earth and reasonable composition design and narrow-window process control in the whole manufacturing process to realize the stable preparation of high corrosion-resistant phosphorus-added high-strength steel BT170P1 cold-rolled steel strip. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described below in conjunction with the drawings.

[0033] Figure 1 is the weight gain rate curve of the specimen;

[0034] Figure 2 is the comparison of the corrosion depth of the specimen;

[0035] Figure 3 is the impedance amplitude modulus and phase angle of No. 1 and No. 2;

[0036] Figure 4 is the comparison of the AC impedance of No. 1 and No. 2 test steels at different immersion periods;

[0037] Figure 5It is the C Nyquist diagram and polarization curve;

[0038] Figure 6 It is the scanning detection result of the corrosion layer of the cross-section of the sample without rare earth addition. (a) Microscopic morphology and detection point positions at the junction of the corrosion layer and the matrix; (b) Energy spectrum diagram of the detection point; (c) Microscopic morphology at the junction of the corrosion layer and the matrix after magnification and detection points "1" and "2"; (d) Energy spectrum diagram of point "1"; (e) Energy spectrum diagram of point "2";

[0039] Figure 7 It is the scanning detection result of the corrosion layer of the cross-section of the sample with rare earth addition. (a) Microscopic morphology and detection point positions at the junction of the corrosion layer and the matrix; (b) Energy spectrum diagram of the detection point; (c) Microscopic morphology at the junction of the corrosion layer and the matrix after magnification and the detection point; (d) Energy spectrum diagram of the detection point. Specific implementation method

[0040] A preparation method of a high corrosion-resistant rare earth and phosphorus added high-strength steel BT170P1 cold-rolled steel strip, which makes the steel plate have good corrosion resistance.

[0041] The method of the present invention uses medium-thick slab continuous casting billets as hot-rolled raw materials, and undergoes processes such as heating, rough rolling, finish rolling, pickling rolling, continuous annealing and tempering, etc., and finally obtains a cold-rolled steel strip with good stamping formability. The microstructure of the steel plate is mainly ferrite.

[0042] Through experimental detection, the r90 value representing the formability index is detected. The average r90 value of the steel plate with rare earth addition is 2.05, and the average r90 value of the product without rare earth addition is 1.91.

[0043] The design scheme of the hot-rolled raw material composition is as follows:

[0044] The mass fraction of elements is: C≤0.0030%, Si: 0.030 - 0.070%, Mn: 0.055 - 0.065%, P: 0.040 - 0.055%, S≤0.0090%, Ti: 0.040 - 0.060%, Al: 0.030 - 0.070%, RE(Ce): 0.0015 - 0.025%, N≤0.004%, O≤0.003%, and the rest are iron and other inevitable impurities.

[0045] The preparation method of the high corrosion-resistant rare earth and phosphorus added high-strength steel BT170P1 cold-rolled steel strip includes the following steps:

[0046] Smelting and continuous casting: The hot metal is subjected to desulfurization pretreatment. The requirement for the area of the hot metal slag to be removed is greater than 95%. The sulfur content of the hot metal entering the converter is required to be less than 0.002%. During the tapping process of the converter, argon is turned on at the 1 / 4 moment, and then the ladle top slag is made first. 5 kg / t of quicklime and an appropriate amount of slag-making agent are added using a feeding chute. The addition amount of quicklime is calculated according to the converter tonnage to make the ladle top slag; after the converter tapping is completed, aluminum pellets are added at 0.3 - 0.5 kg / t of steel to modify the top slag. After the decarburization, deoxidation and alloying in the RH process are completed, aluminum pellets are added at 0.15 - 0.20 kg / t of steel to modify the top slag. RH furnace vacuum degassing is carried out, and deep decarburization treatment is carried out according to the RH molten steel in-place composition and temperature. After decarburization is completed, after circulating for more than 4 minutes, alloys such as ferromanganese, ferrophosphorus, and ferrotitanium are added to adjust the composition. After the composition adjustment is completed, ensure that the vacuum degree is guaranteed to be below 80 Pa and circulate for more than 5 minutes. When the active oxygen in the steel is ≤ 3 ppm before breaking the vacuum, according to the actual molten steel amount, a commercially available ferroalloy containing 30% rare earth lanthanum and cerium is added at 0.2 kg / t of steel, and the vacuum is circulated for more than 2 minutes before starting to break the vacuum. The continuous casting machine adopts constant casting speed control, and the casting speed range is 1.2 - 1.6 m / min. Protective casting is adopted during the casting process of the continuous casting machine.

[0047] Heating and hot rolling process:

[0048] (1) Finished product thickness ≤ 3.0 mm: The heating furnace temperature is controlled at 1180 °C - 1220 °C, the soaking temperature of the heating furnace is 1190 °C - 1230 °C, the residence time in the furnace is 180 - 240 min, the soaking time is 30 - 60 min, and the slab discharging temperature is 1200 °C - 1240 °C.

[0049] (2) Finished product thickness > 3.0 mm: The heating furnace temperature is controlled at 1180 °C - 1210 °C, the soaking temperature of the heating furnace is 1190 °C - 1220 °C, the residence time in the furnace is 180 - 240 min, the soaking time is 30 - 60 min, and the slab discharging temperature is 1190 °C - 1230 °C.

[0050] After high-pressure water descaling, rolling is carried out. The rough rolling starting temperature is 1150 °C - 1800 °C, the finish rolling temperature is 895 °C - 925 °C, and the coiling temperature is 620 °C - 635 °C.

[0051] Acid rolling process: The acid rolling rolling schedules for different thicknesses execute the specifications in the following table

[0052] Table 1 Raw material thickness requirements for products with different thicknesses

[0053] Final thickness (mm) Raw material thickness (mm) ≥0.70～＜0.80 3.5 ≥0.80～＜0.90 3.8 ≥0.90～＜1.00 4.0 ≥1.00～＜1.20 4.3 ≥1.20～＜1.50 4.5 ≥1.50～＜1.80 5.0 ≥1.80～＜2.00 5.5

[0054] Annealing process: The annealing process executes the set specifications in Table 2 below

[0055] Table 2 Annealing furnace process parameters

[0056]

[0057]

[0058] Table 3 Production Process Speed Requirements

[0059] Thickness (mm) Speed (m / min) ≥0.7～<1.1 150±15 ≥1.1～<1.5 110±15 ≥1.5～<2.0 100±15

[0060] Skin Passing Process:

[0061] Table 4 Skin Pass Mill Process Parameters

[0062] Thickness (mm) Skin pass elongation (%) ≥0.7～<1.1 0.6±0.05 ≥1.1～<2.0 0.7±0.05

[0063] Implementation Case 1:

[0064] Select the cold-rolled steel strip of conventional composition design plus phosphorus high-strength steel BT170P1 (1# sample group) and the cold-rolled steel strip of high corrosion-resistant plus phosphorus high-strength steel BT170P1 (2# sample group) for comparative analysis. Figure 1 It is the weight gain rate curve of the sample. From the weight gain curve of the sample, the corrosion of the IF steel sample is an exponential curve. As time extends, the weights of the 1# and 2# samples increase more and more, and the weight gain of the sample without rare earth is significantly greater than that of the sample with rare earth. After 6 days, the corrosion rate of the 2# sample slows down significantly while the corrosion of the 1# sample continues to develop. The comparison of the samples on the 15th day shows that the 1# sample is 0.17% while the 2# sample is 0.14%. The test data shows that the sample with rare earth exhibits better corrosion resistance. In the initial stage of corrosion, a large number of corrosion ions in the corrosion solution can directly reach the corrosion surface of the test steel, with a small reaction resistance and a large corrosion rate. As the corrosion time extends, the corrosion products gradually deposit on the corrosion surface to form a dense rust layer, which hinders the further corrosion of the matrix. Cerium can improve the adhesion between the rust layer and the steel matrix, and at this time the corrosion resistance of the steel is further enhanced. After 6 days, the rust layer products fall off to some extent, the thickness decreases, and the reaction resistance decreases slightly, resulting in a small increase in the corrosion rate.

[0065] Figure 2 It is the comparison of the corrosion depth of the samples. Among them, the corrosion depths of the 1# sample corresponding to the test cycles of 3 days, 6 days and 15 days are 8.46μm, 27.21μm and 67.04μm respectively, while the corrosion depths of the 2# sample under the corresponding conditions are 5.54μm, 21.04μm and 58.08μm respectively. The test results show that the corrosion resistance of the sample without rare earth is significantly lower than that of the sample with rare earth implementing the present invention.

[0066] Implementation Case 2:

[0067] The cold-rolled steel strip of phosphorus-added high-strength steel BT170P1 with conventional composition design (sample group 1#) and the cold-rolled steel strip of phosphorus-added high-strength steel BT170P1 with high corrosion resistance (sample group 2#) were selected for comparative analysis. From Figure 3 It can be seen that the initial corrosion processes of the 1# and 2# steels are similar, and the cathodic corrosion current density of the 2# steel is lower than that of the 1# steel, proving that the corrosion resistance of the 2# steel is better than that of the 1# steel. Figure 3 The impedance spectroscopy results show that the phase angle of the initial corrosion process of the 2# steel sample is also smaller than that of the 1# steel sample, which is consistent with the law obtained in Case 1.

[0068] Figure 4 The following shows the comparison of the impedance spectra of the 1# and 2# test steels at different immersion periods. From Figure 4 it can be seen that with the extension of the immersion time, the radius of the capacitive reactance arc of the 2# sample is larger than the resistance of the 1# steel. The radius of the capacitive reactance arc of both test steels shows a trend of first increasing and then decreasing, while the radius of the capacitive reactance arc of the 1# test steel decreases significantly with the extension of the immersion period. The sample results show that the 2# sample has better corrosion resistance.

[0069] Figure 5 The following shows the polarization curves of the 1# and 2# test steels. The intersection point of the reverse extension line of the 2# steel sample is smaller than that of the 1# steel sample, indicating that the 2# steel has a smaller current density and corrosion resistance. With the increase of the frequency, the self-corrosion current density gradually increases.

[0070] Implementation Case 3:

[0071] The cold-rolled steel strip of phosphorus-added high-strength steel BT170P1 with conventional composition design (sample group 1#) and the cold-rolled steel strip of phosphorus-added high-strength steel BT170P1 with high corrosion resistance (sample group 2#) were selected for comparative analysis: The morphology, size and distribution of MnS inclusions in steel seriously affect the corrosion resistance of steel. Mn and S elements in the sample are easy to form strip-shaped inclusions, and the corrosion potential is lower. The ability of strip-shaped inclusions to induce pitting corrosion is greater than that of short-strip and spherical inclusions, and it is more likely to cause corrosion. MnS inclusions are rolled and elongated during the rolling process of thin-gauge strip steel and are close to the near-surface of the strip steel. In the corrosion solution, each corrosion decomposition reaction is shown in Equation 1. The Fe 3+ produced by the corrosion and dissolution of the steel matrix undergoes hydrolysis reaction to generate H + , and at the same time MnS dissolves to produce HS - , H + and HS - further corrode the matrix around the inclusions (Equation 2), thus deteriorating the corrosion performance of the steel matrix. In addition, during the corrosion process, MnS inclusions undergo electrochemical dissolution to produce sulfur-containing precipitates, as shown in Equation 3. In the absence of erosive Cl -Under certain conditions, sulfur has a corrosive effect and induces pitting corrosion of the steel matrix. The products of both chemical dissolution and electrochemical dissolution of MnS inclusions are erosive, which causes corrosion of the steel matrix and reduces the corrosion resistance of the steel matrix.

[0072]

[0073] Therefore, in the aluminum-killed IF steel used in the experiment, the long and large-sized MnS inclusions serve as pitting corrosion initiation sites. During the corrosion process, they react with [H] in the solution, which is extremely likely to accelerate corrosion, increase the corrosion kinetic energy, and lead to a decline in the corrosion resistance of the steel. Therefore, effective control of MnS inclusions can play a positive role in the relevant properties of the steel.

[0074] Figure 6 、 Figure 7 Figure shows the cross-sectional corrosion layer scanning detection results of the specimen after 15 days of dry-wet cycling test. It can be seen from the figure that the thickness of the corrosion layer of the specimen without rare earth addition is 25 μm, which is significantly thicker than that of the specimen with rare earth addition (10 μm). A large amount of substances such as [Mn] and [S] are found at the interface between the corrosion layer and the steel matrix. Near the corrosion layer of Specimen 2#, it is mainly [Fe] and O. When rare earth Ce is added to the steel, Ce combines with active O and S in the steel with lower Gibbs free energy and is extremely likely to form CeAlO3 and Ce2O2S. On the other hand, the addition of rare earth Ce first combines with S in the steel and precipitates earlier than MnS during solidification, forming small-sized spherical inclusions, which can significantly reduce the size and quantity of MnS inclusions at various positions of the slab, thereby reducing the probability of matrix corrosion induced by MnS inclusions in the steel. In addition, the shape of cerium-containing inclusions is spherical, without a tip position, and has better fusion with the steel matrix. The passivation film at the interface between the inclusion and the matrix is not easily damaged by erosive ions, reducing the corrosion active sites on the matrix. At the same time, rare earth can make the inclusions in the steel evenly distributed, effectively reducing the anode area, thereby greatly reducing the probability of matrix corrosion induced by inclusions.

[0075] Rare earth in the steel generates Ce 3+ ions during the corrosion process. These rare earth ions form insoluble rare earth sulfates with SO4 2- generated during the corrosion process and cover the anode. Ce 3+ can be oxidized to Ce 4+ . Ce 4+ is a strong oxidant, and its oxidation ability is greater than that of oxygen in the air. It can oxidize Fe 2+ to Fe 3+ . Ce 4+ is then reduced to Ce 3+, not only promoting the formation of stable iron phosphate, but also the rare earth ions form colloidal precipitates of rare earth phosphate or rare earth dihydrogen phosphate with H3PO4 at pH = 4 - 5, covering the anode together with various insoluble phosphates, preventing the dissolution of iron, and thus slowing down the corrosion of the substrate.

[0076] The embodiments described above are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a high-corrosion-resistant rare earth phosphorus-added high-strength steel BT170P1 cold-rolled steel strip, characterized in that: The steps include: Smelting and continuous casting: The molten iron is pre-treated for desulfurization. The molten iron slag cleaning area is required to be greater than 95%. The sulfur content of the molten iron entering the converter is required to be less than 0.002%. After the argon gas is turned on at 1 / 4 of the converter tapping process, the ladle top slag operation is first carried out. Use the unloading chute to add 4.5-5.5kg / t of lime and an appropriate amount of slag-making agent. The amount of lime added is calculated according to the converter tonnage to make the ladle top slag; after the converter tapping is completed, aluminum particles are added at a rate of 0.3-0.5 kg / ton of steel for top slag modification; after the RH process decarburization, deoxidation and alloying are completed, aluminum particles are added at a rate of 0.15-0.20 kg / ton of steel for top slag modification Slag modification; RH furnace vacuum degassing, deep decarburization treatment according to the RH molten steel composition and temperature; after decarburization, add metal manganese, ferrophosphorus, and ferrotitanium alloy to adjust the composition after circulating for more than 4 minutes. After the composition adjustment is completed, ensure that the vacuum degree is guaranteed to be below 80Pa and circulate for more than 5 minutes. When the active oxygen in the steel is ≤3ppm before breaking the vacuum, add the commercially available ferroalloy containing 30% of rare earth lanthanum and cerium according to the actual amount of molten steel according to demand, and start breaking the vacuum after the vacuum circulation for more than 2 minutes; the casting machine adopts constant pulling speed control, the pulling speed range is 1.2-1.6m / min, and the casting process of the casting machine adopts protective pouring; Heating and hot rolling process: (1) Finished product thickness ≤ 3.0 mm: heating furnace temperature is controlled at 1180°C-1220°C, heating furnace soaking temperature is 1190°C-1230°C, furnace time is 180-240 min, soaking time is 30-60 min, slab out-of-furnace temperature is 1200°C-1240°C; (2) Finished product thickness>3.0mm: heating furnace temperature is controlled at 1180℃~1210℃, heating furnace soaking temperature is 1190℃-1220℃, furnace time is 180-240min, soaking time is 30-60min, slab out-of-furnace temperature is 1190℃-1230℃; After high-pressure water descaling, rolling is carried out, the rough rolling temperature is 1150℃~1800℃, the finishing rolling temperature is 895℃~925℃, and the coiling temperature is 620℃~635℃; Pickling process: Pickling rolling procedures for different thicknesses are as follows: Annealing process: Annealing process is carried out according to the following table: Production process speed requirements: Leveling process: 。 2. The method for preparing the high corrosion resistance rare earth phosphorus added high strength steel BT170P1 cold rolled steel strip according to claim 1, characterized in that: Use the discharge chute to add 5kg / t of lime and appropriate amount of slag-forming agent.

3. The method for preparing the high corrosion resistance rare earth phosphorus added high strength steel BT170P1 cold rolled steel strip according to claim 1, characterized in that: According to the actual amount of molten steel, a commercially available ferroalloy containing 30% of rare earth lanthanum and cerium is added at 0.2 kg / ton of steel.

4. The method for preparing the high corrosion resistance rare earth phosphorus added high strength steel BT170P1 cold rolled steel strip according to claim 1, characterized in that: In the annealing process: when the thickness difference is equal to 1.0 times, the outlet temperature control range of the heating section and the soaking section is required to be ±10°C; when the thickness difference exceeds 1.0 times, the outlet temperature control range of the heating section and the soaking section is required to be ±15°C.

5. The method for preparing the high corrosion resistance rare earth phosphorus added high strength steel BT170P1 cold rolled steel strip according to claim 1, characterized in that: The chemical composition design scheme of the steel strip by mass percentage is as follows: C≤0.0030%, Si: 0.030-0.070%, Mn: 0.055-0.065%, P: 0.040-0.055%, S≤0.0090%, Ti: 0.040-0.060%, Al: 0.030-0.070%, Ce: 0.0015-0.025%, N≤0.004%, O≤0.003%, and the rest are iron and other inevitable impurities.

6. The method for preparing the high corrosion resistance rare earth phosphorus added high strength steel BT170P1 cold rolled steel strip according to claim 1, characterized in that: Through experimental testing, the r90 value representing the forming performance index was tested, and the average r90 value of the rare earth steel strip was 2.

05.

7. The method for preparing the high corrosion resistance rare earth phosphorus added high strength steel BT170P1 cold rolled steel strip according to claim 1, characterized in that: This method can more effectively bring into play the effect of rare earth in steel and improve the corrosion resistance of steel plates.

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