Rare earth cold-rolled steel plate for ultralow-carbon double-sided enamel and preparation method thereof

Abstract

The invention relates to an ultra-low carbon rare earth cold-rolled steel sheet for double-sided enamel and a preparation method thereof. The ultra-low carbon rare earth cold-rolled steel sheet comprises the following chemical components in percentage by weight: 0.001-0.009% of C, less than or equal to 0.003% of Si, 0.15-0.40% of Mn, 1t of P, 1t of S and the balance of Fe. The alloy comprises the following components in percentage by weight: 0.005% of Fe, 0.035%-0.055% of S, 0.040%-0.100% of Ti, 0.02%-0.05% of Al, 0.0055%-0.0080% of N, 0.0040%-0.0070% of B, 0.001%-0.02% of Ce, 0.001%-0.030% of O and the balance of Fe and inevitable impurities. Compared with the prior art, precious metal elements such as Cr, Nb, V and Mo do not need to be added, the mechanical property and fish scaling resistance of the cold-rolled enamel steel before and after enameling are not changed, and the prepared ultra-low carbon cold-rolled enamel steel has good formability and fish scaling resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of enameled steel production, and relates to an ultra-low carbon rare earth cold-rolled steel plate for double-sided enameling and a preparation method thereof. Background Art

[0002] Enameled steel products have the strength and excellent formability of the base metal material, and also have the advantages of the surface enamel layer being beautiful, easy to clean, corrosion-resistant, wear-resistant and high-temperature-resistant. Therefore, they are widely used in light industry, home appliances, metallurgy, chemical industry, construction and other industries.

[0003] Cold-rolled enameled steel is often used in household products and building panels requiring high formability. However, scale-scaling is the most critical flaw of enameled steel. Because scale-scaling is unpredictable, it can occur immediately after enameling, 24 hours later, a week later, or even six months later. Once it occurs, the enameled steel product is rendered scrap. To improve the scale-scaling resistance of enameled steel, the most common method is to add microalloying elements to the steel to form a large number of inclusions and second-phase precipitates, thereby simultaneously improving the steel's strength and scale-scaling resistance. Currently, the elements added to ultra-low-carbon enameled steel mostly combine titanium with other elements. This is because titanium is a strong carbon and nitride former. Titanium combines with oxygen, carbon, nitrogen, and sulfur to form both simple and complex compounds. Titanium fixes carbon, nitrogen, and sulfur, enhancing plasticity and scale-scaling resistance. For example, in the patent publication number CN1704494A, entitled “Cold-rolled enameled steel with excellent fishscale resistance and ultra-deep drawing properties and its manufacturing method”, the carbon content of the cold-rolled enameled steel is ≤0.005%, and the Ti content satisfies the formula: 4C+3.42N+0.5S+0.02~0.04% (each element in the formula represents its mass fraction); in the patent publication number CN102899565A, entitled “A cold-rolled enameled steel and its manufacturing method”, the carbon content is 0.002~0.010%, and the Ti content control requirement is Nb+ΔTi≥0.02%, Ti=4C+3.42N+1.5S+ΔTi; and in CN1045 Patent 813A, titled "Enameled Steel Sheet and Method for Manufacturing the Same," specifies a carbon content of <0.0025%, a Ti content of no more than 0.05%, and a Nb content of no more than 0.05%, with the total Ti and Nb content ranging from 0.001% to 0.05%. Patent publication number CN100396808C, titled "Cold-Rolled Enameled Steel with Excellent Fishscale Resistance and Ultra-Deep Drawing Properties and Method for Manufacturing the Same," specifies a carbon content of ≤0.005%, but limits the Ti content to (4C + 3.42N + 1.5S) + (0.02-0.04%), with the remainder being iron and other unavoidable impurities. Furthermore, the requirement is that 0.01% ≤ C + 0.5S + 0.886N ≤ 0.03%. All of these invention patents address ultra-low carbon steel and clearly define a proportional model for the relationship between Ti content and the contents of other elements. There are also some invention patents that do not explicitly propose the composition design of Ti element + other elements, but also propose in the description to use the titanium-containing precipitate phase formed by titanium and oxygen, carbon, nitrogen and sulfur as a hydrogen trap for enameling steel.For example, in the patent publication number CN111154955A, entitled “Production method of ultra-deep drawn cold-rolled enameled steel”, the C content of the cold-rolled enameled steel is controlled at 0.003-0.008%, and the Ti content is controlled at 0.070-0.010%. In the patent publication number CN117758140A, entitled “A method for producing ultra-deep drawn cold-rolled enameled steel sheets by semi-steel smelting”, the C content of the cold-rolled enameled steel is controlled at 0.002-0.008%, and the Ti content is controlled at Controlled at 0.085-0.120%; in the patent with publication number CN117488207A, entitled "A method for controlling the performance grading of ultra-deep drawn cold-rolled enameled steel sheets", the C content in the cold-rolled enameled steel is disclosed to be 0.002-0.008%, and the Ti content is controlled at 0.085-0.120%; in addition, there is also an IF steel production method, but with increased Ti and S contents, that is, by controlling the production process, Ti4C2S2 second phase particles are precipitated during the production process. For example, patent publication number CN107868908A, entitled "A Cold-Rolled Enameled Steel for Deep Drawing Double-Sided Dry Enameling and Production Method," lists a carbon content of 0.0015-0.0060% and a Ti content controlled at 0.06-0.10%. Patent publication number CN101082107A, entitled "Ultra-Low Carbon Cold-Rolled Deep Drawing Enameled Steel and Production Method," lists a carbon content of 0.002-0.005% and a Ti content controlled at 0.05-0.09%. A third approach to enameling steel involves simultaneously adding one or more of Cu, Cr, Ni, Mo, and B, in addition to controlling the Ti content. The purpose is to form composite oxides of Mn and other elements, increasing hydrogen traps, and to improve enamel adhesion and pinhole resistance. For example, patent publication number CN102251174A, entitled "A Method for Manufacturing Enameled Steel and Cold-Rolled Sheet," specifies that the carbon content in the cold-rolled enameled steel be ≤0.004%, and the titanium content be controlled between 0.005% and 0.020%. Patent publication number CN 115305411A, entitled "A Method for Efficient Production of Ultra-Deep Drawing Cold-Rolled Enameled Steel," specifies that the carbon content in the cold-rolled enameled steel be ≤0.005%, and the titanium content be controlled between 0.09% and 0.12%. Cu is also added, with the content controlled between 0.20% and 0.50%. In summary, current technology for ultra-low-carbon enameled steel primarily enhances the steel's fishscale resistance by adding titanium to create irreversible hydrogen traps. However, excessive titanium content in the steel can reduce the enamel's adhesion and affect the overall enameling performance of the steel sheet.In the patent with publication number CN116200670A, entitled "A cold-rolled enameled steel sheet with excellent adhesion properties and its manufacturing method", the published C content is: 0.001~0.002%, Nb: 0.01~0.04%. Instead of adding Ti element, Cu, Nb and Mo elements are added to generate Mn-Nb or other element composite oxides in the steel sheet, which act as second-phase particles to act as hydrogen traps, thereby preventing scale explosion of the steel sheet after enameling.

[0004] While increasing the carbon content of low-carbon enameled steel improves material strength, the majority of the carbon in the steel exists as Fe₃C. At high temperatures, Fe₃C decomposes to release free carbon, which reacts with moisture and other gases in the kiln during the enameling process to generate CO, CO₂, and H₂. The higher the carbon content, the more harmful gases are produced during enameling, increasing their potential for damage. These gases can cause pinhole defects and fishscale, which compromises the quality of the enameling. Therefore, niobium, vanadium, titanium, and boron are currently added to form compounds with carbon. These compounds are beneficial for improving the steel's fishscale resistance. For example, Publication No. CN102251192A, entitled "A Vitreous Enameled Steel and Its Manufacturing Method," discloses a method for preparing enameled steel containing ≤0.05% carbon and containing one or more of B, Cu, Nb, V, and Ti, with the total amount controlled to 0.01-0.3%. Publication number CN101684532A discloses "Cold-rolled enameled steel for water heaters and its production method." The steel has a carbon content of 0.01%-0.08%, requires Ti of 0.02-0.12%, and has an excess titanium content of: Ti-(4C+3.43N+1.5S)≤0. Furthermore, the steel contains Nb. This suggests that the addition of Ti and Nb also forms compounds with carbon.

[0005] Currently, some methods use aluminum oxide in steel as a hydrogen trap. For example, publication number CN111057828A discloses "A High-Oxygen Enameled Steel and Its Production Method," and publication number CN107916371A discloses "A Production Method for Enameled Steel," with a carbon content of ≤0.01% to 0.07%. These patents either improve steelmaking processes or utilize low-carbon aluminum-killed steel production methods to control free oxygen, sulfur, and manganese in the molten steel, generating inclusion particles such as MnS, MnO, and Al2O3 that act as hydrogen traps to improve scale resistance.

[0006] However, the aforementioned patents using Ti compounds as irreversible hydrogen traps suffer from excessively high Ti content in the steel, which reduces the enamel's adhesion and affects the overall enameling performance of the steel plate. Patents involving high-oxygen steel, while having a higher oxygen content in the steel is beneficial for decarburization, also form a large number of coarse oxide inclusions in the steel. While these inclusions can improve the steel plate's scale resistance and adhesion, they can also severely impair its plasticity and surface quality, reducing its workability. Summary of the Invention

[0007] The purpose of the present invention is to provide an ultra-low carbon double-sided enameled rare earth cold-rolled steel plate and its preparation method in order to overcome at least one defect of the above-mentioned prior art. The present invention controls the type and amount of inclusions inside the steel by a smelting method without adding alloys, and then controls the grain size, type and amount of precipitated phases of the steel plate by heat treatment to increase the mechanical properties and hydrogen storage capacity of the enameled steel, thereby improving the material mechanical properties and fishscale resistance of the enameled steel; the enameled steel of the present invention has good material properties and improved enameling properties.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] One of the technical solutions of the present invention is to provide an ultra-low carbon rare earth cold-rolled steel sheet for double-sided enameling, wherein the rare earth cold-rolled steel sheet for enameling comprises the following chemical components in weight percentage:

[0010] C: 0.001~0.009%, Si: ≤0.003%, Mn: 0.15~0.40%, P: <0.005%, S: 0.035~0.055%, Ti: 0.040~0.100%, Al: 0.02~0.05%, N: 0.0055~0.0080%, B: 0.0040~0.0070%, Ce: 0.001~0.02%, O: 0.001~0.030%, and the rest are Fe and unavoidable impurities.

[0011] As a preferred technical solution, the molten steel composition of the rare earth cold-rolled steel sheet for enamel includes the following chemical components in weight percentage:

[0012] C: 0.002~0.008%, Si: ≤0.003%, Mn: 0.15~0.40%, P: <0.005%, S: 0.035~0.055%, Ti: 0.040~0.10%, Al: 0.02~0.05%, N: 0.0055~0.0079%, B: 0.0040~0.0070%, Ce: 0.001~0.02%, O: 0.001~0.030%, and the balance is Fe and unavoidable impurities.

[0013] Furthermore, the microstructure of the rare earth cold-rolled steel sheet for enameling is ferrite, and a large number of Ce-containing particles, such as CeAlO3, CeS, Ce2O2S, etc., are distributed in the ferrite matrix, followed by inclusions such as Al2O3, MnO, MnS, BN, etc., and there are also a large number of Ti-containing precipitates, such as TiS, TiN and Ti4C2S2, etc. The inclusions of the produced rare earth cold-rolled steel sheet for enameling are mainly CeAlO3, MnO, MnS, TiS, TiN, Ti4C2S2, etc., followed by a small amount of inclusions such as Al2O3, BN, CeS, Ce2O2S, etc.

[0014] One of the technical solutions of the present invention is to provide a method for preparing the ultra-low carbon double-sided enameled rare earth cold-rolled steel sheet, which includes smelting, continuous casting, hot rolling, pickling and annealing heat treatment steps.

[0015] Furthermore, during the hot rolling process, the heating temperature is 1150-1250°C, and after the insulation is completed, the steel is taken out of the furnace for rolling, the rough rolling temperature is above 1050°C, and the final rolling temperature is 850-950°C.

[0016] Furthermore, after the hot rolling process, the steel is cooled to 680-800° C. and coiled.

[0017] Furthermore, pickling includes pickling and cold rolling.

[0018] Furthermore, the reduction ratio of the cold rolling is not less than 75%.

[0019] Furthermore, the annealing temperature is 740-800°C.

[0020] Furthermore, the annealing is performed by continuous annealing or hood annealing.

[0021] Furthermore, the holding time of continuous annealing is 60 to 120 seconds, and after the holding is completed, it is cooled to room temperature at a rate of 30 to 50°C / s. The holding time of hood annealing is 5 to 10 hours, which is determined according to the coil diameter. However, all temperatures of the materials in the coil must be between 740 and 800°C for at least 5 hours. After the holding is completed, it is cooled to room temperature with the furnace.

[0022] The present invention controls the content of each element and the effects are as follows:

[0023] Carbon (C): controlled below 0.01%. Because the carbon content in steel is high, it reacts with oxygen during enameling to generate CO gas. When the gas is discharged, it will cause defects such as pinholes, bubbles, and scale in the porcelain layer. High carbon content also easily leads to a large heat-affected zone in welding.

[0024] Silicon (Si): Si ≤ 0.003%. Adding a small amount of silicon to steel can easily form lattice distortion zones due to the large difference in radius between Si atoms and iron atoms, achieving solid solution strengthening. The number of lattice distortion zones increases after high pressure reduction and crushing. After recrystallization annealing, the grain boundaries that prevent hydrogen diffusion increase, improving anti-scale performance.

[0025] Manganese (Mn): Controlled within the range of 0.15-0.40%. Manganese is a very weak deoxidizer. When the carbon content is very low and the oxygen content is very high, it has a deoxidizing effect, forming MnO inclusions during the smelting process. Manganese can also combine with sulfur in the steel to form MnS inclusions. Both of these can act as irreversible hydrogen traps, improving the steel's anti-scale performance.

[0026] Phosphorus (P): P: <0.005%. Phosphorus is a harmful element. If the phosphorus content is too high, it will easily segregate at the grain boundaries, affecting the quality of the enamel. In the present invention, the lower the phosphorus content, the better.

[0027] Sulfur (S): 0.035-0.055% sulfur is added to the steel. On the one hand, it forms MnS inclusions with manganese in the steel, and on the other hand, it forms TiS and Ti4C2S2 precipitation phases with Ti to increase hydrogen storage traps, improve anti-scale performance and precipitation strengthening effects.

[0028] Titanium (Ti): Maintain within the range of 0.040-0.10%. Titanium is a strong carbon and nitride-forming element. It combines with oxygen, carbon, nitrogen, and sulfur to form both simple and complex compounds. Titanium fixes carbon, nitrogen, and sulfur, improving plasticity and scale resistance. However, excessive Ti content can reduce the adhesion of the enamel and affect the overall enameling performance of the steel plate.

[0029] Aluminum (Al): Controlled within the range of 0.02-0.05%. Aluminum is a strong deoxidizing element. A high aluminum content reduces the oxygen content in the steel. Aluminum forms coarse aluminum oxide inclusions in the steel, resulting in poor plasticity and poor workability.

[0030] Boron (B): Maintain within the range of 0.0040-0.0060%. Boron is a strong nitride-forming element. Boron reacts with nitrogen to precipitate BN particles. Through process control, finely dispersed BN particles can be distributed throughout the steel, improving the steel's anti-scale performance. However, excessive boron content can easily cause cracking at the corners of continuous casting slabs. Adding titanium can prevent the formation of large amounts of boron nitride and reduce the crack sensitivity of continuous casting slabs.

[0031] Cerium (Ce): Controlled within the range of 0.001-0.02%. MnS and Al2O3 in steel are considered the most common non-metallic inclusions in steel. They appear in strips or spindles in the steel, destroying the continuity of the matrix, acting as notches and stress concentrations, and generating microcracks at the interface between the inclusions and the matrix, reducing the toughness of the steel and affecting the processing properties of the steel. After adding the rare earth element Ce, the strips or spindles of MnS and Al2O3 become dispersed and spherical, and their number increases. Secondly, the addition of Ce can also increase the amount of Ti-containing precipitation, that is, increase the number of irreversible hydrogen traps, which is beneficial to improving the strength and anti-scale explosion performance of the steel. However, an excessively high Ce content will reduce the proportion of 1-3μm rare earth inclusions.

[0032] Oxygen (O): Oxygen in steel is controlled within the range of 0.001% to 0.030%. A high oxygen content in steel not only facilitates decarburization but also forms a large number of oxide inclusions, which improve the steel plate's scale resistance and adhesion. However, excessive oxide inclusions can severely impair the steel plate's plasticity and surface quality.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The present invention controls the type and quantity of inclusions in the steel by a smelting method without adding alloys, and then controls the grain size, type and quantity of precipitated phases in the steel plate by heat treatment to increase the mechanical properties and hydrogen storage capacity of the enameled steel, thereby improving the mechanical properties and fishscale resistance of the enameled steel.

[0035] (2) By adopting the method of the present invention, there is no need to add precious metal elements such as chromium (Cr), niobium (Nb), vanadium (V) and molybdenum (Mo), and the mechanical properties and anti-scale explosion properties of the cold-rolled enameled steel remain unchanged before and after enameling. The prepared ultra-low carbon double-sided enameled rare earth cold-rolled steel sheet has good formability and anti-scale explosion properties, good material properties and improved enameling properties, and can meet the production needs of enameled parts in industries such as home appliances, kitchenware, sanitary ware and construction, and has good cost reduction and efficiency improvement capabilities and market potential. DETAILED DESCRIPTION

[0036] The present invention is described in detail below with reference to specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0037] Unless otherwise specified, the equipment used in the following examples are all conventional equipment in the art; the reagents used are all commercially available products or prepared by conventional methods in the art unless otherwise specified. Anything not described in detail in the following examples can be achieved by conventional experimental means in the art.

[0038] Example 1:

[0039] An ultra-low carbon double-sided enameled rare earth cold-rolled steel sheet and a preparation method thereof, the specific steps are as follows:

[0040] The molten steel is smelted with a certain chemical composition ratio, the chemical composition of which is shown in Table 1, and continuously cast to obtain a steel billet. The steel billet is heated to 1200°C, and after holding, it is first rough rolled at 1100°C, and then finish rolled at 900°C. The rolled steel is cooled to 740°C and then coiled. The steel is first pickled, and then cold rolled at a reduction rate of 80%, and continuously annealed at 770°C. After holding for 90s, it is cooled to room temperature at a rate of 40°C / s to obtain an ultra-low carbon rare earth cold-rolled steel sheet for double-sided enameling.

[0041] Example 2:

[0042] An ultra-low carbon double-sided enameled rare earth cold-rolled steel sheet and a preparation method thereof are basically the same as those in Example 1, except that the chemical composition of the molten steel is different, as shown in Table 1, and the annealing method is different, hood annealing at 770°C, followed by 7 hours of insulation and then cooling to room temperature with the furnace.

[0043] Table 1 Chemical composition of the rare earth cold-rolled steel sheet for ultra-low carbon double-sided enamel in the embodiment

[0044] Case C Si Mn P S Ti Alt N B Ce TO Fe Example 1 0.008 0.003 0.27 0.004 0.042 0.093 0.046 0.006 0.0061 0.005 0.0021 the remaining Example 2 0.006 0.003 0.27 0.004 0.048 0.093 0.032 0.006 0.0046 0.01 0.0023 the remaining

[0045] Among them, Alt is the content of all aluminum components in the molten steel, including the content of aluminum in the form of acid-soluble aluminum, and TO is the content of all oxygen components in the molten steel, including the content of oxygen in the form of oxides.

[0046] The mechanical properties and fishscale resistance of the cold-rolled enameled steel in the examples were tested after enameling.

[0047] As shown in Table 2, the enameled steel in this embodiment has good material properties such as tensile strength, yield strength, and elongation, and improved enameling properties such as TH value. No precious metal elements such as chromium (Cr), niobium (Nb), vanadium (V), and molybdenum (Mo) need to be added. The prepared ultra-low carbon rare earth cold-rolled steel sheet for double-sided enameling has good formability and scale resistance.

[0048] Table 2 Mechanical properties and scale resistance of rare earth cold-rolled steel sheets for ultra-low carbon double-sided enamel in the embodiment

[0049] Case Tensile strength / MPa Yield strength / MPa Elongation / % TH value Example 1 302 106 47 12 Example 2 302 93 56 14

[0050] This embodiment controls the content of each element and its effects are as follows:

[0051] Carbon (C): controlled below 0.01%. Because the carbon content in steel is high, it reacts with oxygen during enameling to generate CO gas. When the gas is discharged, it will cause defects such as pinholes, bubbles, and scale in the porcelain layer. High carbon content also easily leads to a large heat-affected zone in welding.

[0052] Silicon (Si): Si ≤ 0.003%. Adding a small amount of silicon to steel can easily form lattice distortion zones due to the large difference in radius between Si atoms and iron atoms, achieving solid solution strengthening. The number of lattice distortion zones increases after high pressure reduction and crushing. After recrystallization annealing, the grain boundaries that prevent hydrogen diffusion increase, improving anti-scale performance.

[0053] Manganese (Mn): Controlled within the range of 0.15-0.40%. Manganese is a very weak deoxidizer. When the carbon content is very low and the oxygen content is very high, it has a deoxidizing effect, forming MnO inclusions during the smelting process. Manganese can also combine with sulfur in the steel to form MnS inclusions. Both of these can act as irreversible hydrogen traps, improving the steel's anti-scale performance.

[0054] Phosphorus (P): P: <0.005%. Phosphorus is a harmful element. If the phosphorus content is too high, it will easily segregate at the grain boundaries, affecting the quality of the enamel. In the present invention, the lower the phosphorus content, the better.

[0055] Sulfur (S): 0.035-0.055% sulfur is added to the steel. On the one hand, it forms MnS inclusions with manganese in the steel, and on the other hand, it forms TiS and Ti4C2S2 precipitation phases with Ti to increase hydrogen storage traps, improve anti-scale performance and precipitation strengthening effects.

[0056] Titanium (Ti): Maintain within the range of 0.040-0.10%. Titanium is a strong carbon and nitride-forming element. It combines with oxygen, carbon, nitrogen, and sulfur to form both simple and complex compounds. Titanium fixes carbon, nitrogen, and sulfur, improving plasticity and scale resistance. However, excessive Ti content can reduce the adhesion of the enamel and affect the overall enameling performance of the steel plate.

[0057] Aluminum (Al): Controlled within the range of 0.02-0.05%. Aluminum is a strong deoxidizing element. A high aluminum content reduces the oxygen content in the steel. Aluminum forms coarse aluminum oxide inclusions in the steel, resulting in poor plasticity and poor workability.

[0058] Boron (B): Maintain within the range of 0.0040-0.0060%. Boron is a strong nitride-forming element. Boron reacts with nitrogen to precipitate BN particles. Through process control, finely dispersed BN particles can be distributed throughout the steel, improving the steel's anti-scale performance. However, excessive boron content can easily cause cracking at the corners of continuous casting slabs. Adding titanium can prevent the formation of large amounts of boron nitride and reduce the crack sensitivity of continuous casting slabs.

[0059] Cerium (Ce): Controlled within the range of 0.001-0.02%. MnS and Al2O3 in steel are considered the most common non-metallic inclusions in steel. They appear in strips or spindles in the steel, destroying the continuity of the matrix, acting as notches and stress concentrations, and generating microcracks at the interface between the inclusions and the matrix, reducing the toughness of the steel and affecting the processing properties of the steel. After adding the rare earth element Ce, the strips or spindles of MnS and Al2O3 become dispersed and spherical, and their number increases. Secondly, the addition of Ce can also increase the amount of Ti-containing precipitation, that is, increase the number of irreversible hydrogen traps, which is beneficial to improving the strength and anti-scale explosion performance of the steel. However, an excessively high Ce content will reduce the proportion of 1-3μm rare earth inclusions.

[0060] Oxygen (O): Oxygen in steel is controlled within the range of 0.001% to 0.030%. A high oxygen content in steel not only facilitates decarburization but also forms a large number of oxide inclusions, which improve the steel plate's scale resistance and adhesion. However, excessive oxide inclusions can severely impair the steel plate's plasticity and surface quality.

[0061] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. An ultra-low carbon double-sided enameled rare earth cold-rolled steel sheet, characterized in that: The rare earth cold-rolled steel sheet for enamel comprises the following chemical components in weight percentage: C: 0.001~0.009%, Si: ≤0.003%, Mn: 0.15~0.40%, P: <0.005%, S: 0.035~0.055%, Ti: 0.040~0.100%, Al: 0.02~0.05%, N: 0.0055~0.0080%, B: 0.0040~0.0070%, Ce: 0.001~0.02%, O: 0.001~0.030%, and the rest are Fe and unavoidable impurities.

2. The ultra-low carbon rare earth cold-rolled steel sheet for double-sided enameling according to claim 1, characterized in that: The microstructure of the rare earth cold-rolled steel sheet for enamel is ferrite, in which Ce-containing particles such as CeAlO3, CeS, and Ce2O2S are distributed, followed by Al2O3, MnO, MnS, and BN inclusions, and Ti-containing precipitates such as TiS, TiN, and Ti4C2S2.

3. A method for preparing an ultra-low carbon rare earth cold-rolled steel sheet for double-sided enamel according to claim 1 or 2, characterized in that: The method comprises the steps of smelting, continuous casting, hot rolling, pickling and annealing heat treatment.

4. The method for preparing an ultra-low carbon rare earth cold-rolled steel sheet for double-sided enamel according to claim 3, characterized in that: During the hot rolling process, the heating temperature is 1150-1250°C. After the insulation is completed, the steel is taken out of the furnace for rolling. The rough rolling temperature is above 1050°C and the final rolling temperature is 850-950°C.

5. The method for preparing an ultra-low carbon rare earth cold-rolled steel sheet for double-sided enamel according to claim 3, characterized in that: After the hot rolling process, the coiling temperature is 680-800℃.

6. The method for preparing an ultra-low carbon rare earth cold-rolled steel sheet for double-sided enamel according to claim 3, characterized in that: Pickling includes pickling and cold rolling.

7. The method for preparing an ultra-low carbon rare earth cold-rolled steel sheet for double-sided enamel according to claim 6, characterized in that: The reduction rate of cold rolling is not less than 75%.

8. The method for preparing an ultra-low carbon rare earth cold-rolled steel sheet for double-sided enameling according to claim 3, characterized in that: The annealing temperature is 740-800°C.

9. The method for preparing an ultra-low carbon rare earth cold-rolled steel sheet for double-sided enamel according to claim 3, characterized in that: Annealing is carried out by continuous annealing or hood annealing.

10. The method for preparing an ultra-low carbon rare earth cold-rolled steel sheet for double-sided enamel according to claim 9, characterized in that: The holding time of continuous annealing is 60 to 120 seconds. After the holding is completed, it is cooled to room temperature at a rate of 30 to 50 ° C / s. The holding time of hood annealing is 5 to 10 hours, which is determined according to the coil diameter. After the holding is completed, it is cooled to room temperature with the furnace.