Cold-rolled enamel steel having anti-scaling performance and method for manufacturing the same

Abstract

This invention belongs to the field of enamel steel production, specifically relating to a cold-rolled enamel steel with anti-scaling properties and its preparation method. This invention significantly improves the anti-scaling ability of the enamel steel by adding trace element W to form nanoscale (Ti,W)C precipitates, effectively capturing hydrogen atoms; it also achieves excellent formability, reaching the level of ultra-deep drawing steel. This invention also provides a method for preparing the aforementioned cold-rolled enamel steel with anti-scaling properties, including hot metal pretreatment, converter steelmaking, refining, continuous casting, hot rolling, cold rolling, and annealing. Compared with existing technologies, this invention not only improves the anti-scaling properties of the enamel steel but also ensures good formability, enabling the material to meet the requirements of demanding applications.

Description

Technical Field

[0001] This invention belongs to the field of enamel steel production, specifically relating to a cold-rolled enamel steel with anti-scaling properties and its preparation method. Background Technology

[0002] Enamel is a composite material made by fusing inorganic glassy materials onto a base metal, bonding them firmly to the metal. Enamel products combine the high strength and excellent formability of metallic materials with the corrosion resistance, wear resistance, and high-temperature resistance of the enamel layer, making them widely used in light industry, home appliances, metallurgy, chemical industry, and construction. Steel is a commonly used base material for enamel products. Based on different rolling processes, enamel steel can be divided into cold-rolled enamel steel and hot-rolled enamel steel. Compared to hot-rolled enamel steel, cold-rolled enamel steel has superior formability and is therefore often used to manufacture products with high formability requirements, such as daily utensils, ovens, architectural decorative panels, and desulfurization and denitrification equipment. In the application of cold-rolled enamel steel, in addition to certain requirements for its formability, it is also required to have good anti-scaling properties. This is because scaling is a common and fatal defect in enamel products; once scaling occurs, it means the scrapping of the enamel product. The presence of a large amount of freely diffusing hydrogen in steel is the main cause of scaling in enamel steel. Introducing numerous defects into steel, such as grain boundaries, dislocations, micropores, inclusions, and second-phase precipitates, is a primary method to improve the anti-scaling properties of enamel steel. The most common method involves adding microalloying elements to the steel to form a large number of nano-sized precipitates, thereby simultaneously improving the strength and anti-scaling properties of the enamel steel.

[0003] For some enamel products with extremely high requirements for formability, the base metal often uses cold-rolled enamel steel with ultra-deep-drawing properties, and the corresponding patents mostly adopt an ultra-low carbon + Ti micro-alloying composition design. For example, in patent CN100396808A, entitled "Cold-rolled enamel steel with excellent anti-scaling and ultra-deep-drawing properties and its manufacturing method," the disclosed cold-rolled enamel steel has a C content of less than or equal to 0.005%, and Ti = 4C + 3.42N + 0.5S + 0.02~0.04% (in this formula, each element represents its mass fraction). In patent CN 102251174A, entitled "A type of enamel steel and its cold-rolled sheet manufacturing method," the disclosed cold-rolled enamel steel has a C content of less than or equal to 0.004%, and the Ti content is controlled between 0.005% and 0.020%. Patent CN 115305411A, entitled "A Method for High-Efficiency Production of Ultra-Deep Drawing Cold-Rolled Enameled Steel," discloses a cold-rolled enamel steel with a carbon content of less than or equal to 0.005% and a titanium content controlled between 0.09% and 0.12%. Patent CN 111154955A, entitled "A Production Method of Ultra-Deep Drawing Cold-Rolled Enameled Steel," discloses a cold-rolled enamel steel with a carbon content controlled between 0.003% and 0.008% and a titanium content controlled between 0.070% and 0.010%.

[0004] Cold-rolled enamel steel designed with the above composition mainly relies on second-phase precipitates such as TiC, TiS, and Ti4C2S2 in the steel to improve its anti-scaling properties. TiC, TiS, and Ti4C2S2 capture hydrogen at the interface between these precipitates and the ferrite matrix. The smaller the size of these precipitates, the stronger their hydrogen-capturing ability, and the better the anti-scaling ability of the enamel steel. However, unfortunately, compared to TiC, TiS and Ti4C2S2 are larger in size, and their hydrogen-capturing ability is significantly reduced at the same volume fraction. This results in the failure to fully utilize the anti-scaling properties of cold-rolled enamel steel, and scaling phenomena occur frequently. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a cold-rolled enamel steel with excellent anti-scaling properties and its preparation method through component optimization and process control.

[0006] This invention provides a cold-rolled enamel steel with excellent anti-scaling properties; the chemical composition of the cold-rolled enamel steel by weight percentage is: C≤0.003%, Si≤0.02%, Mn:0.10~0.20%, P≤0.012%, S≤0.010%, Al:0.02~0.04%, Ti:0.07~0.10%, 0.39≤Ti / W≤0.52, N≤0.0030%, O≤0.0010%, with the remainder being Fe and unavoidable impurities.

[0007] The roles of the main chemical elements in this invention are as follows:

[0008] C: It is mainly combined with Ti and W to produce nano-sized (Ti,W)C, which can not only play the role of precipitation strengthening, but also act as a hydrogen trap to improve the anti-scaling performance.

[0009] Si: Si has an adverse effect on the surface quality of enamel steel. The lower the Si content, the better. Considering the actual control capabilities in industrial production, the Si content is controlled to be less than or equal to 0.02%.

[0010] Mn: Mn is a strengthening element in steel. In order to ensure the strength of the cold-rolled enamel steel of this invention, the Mn content is controlled at 0.10 to 0.20%.

[0011] Al: Al is the most commonly used deoxidizing element in steel. In order to ensure the control target of oxygen content in the enamel steel of this invention, the Al content is set to 0.02-0.04%.

[0012] Ti: The main function of Ti is to combine with C and N to ensure that there are no interstitial C and N atoms in the enamel steel of the present invention, so as to ensure that the cold-rolled enamel steel of the present invention has ultra-deep drawing performance.

[0013] W's main role is to combine with Ti and C to form (Ti,W)C. Because (Ti,W)C has a finer size (compared to TiC, Ti4C2S2, and TiS), it further improves the anti-scaling properties of cold-rolled enamel steel. When the atomic ratio of Ti to W is between 1.5 and 2, the size of (Ti,W)C is minimized; therefore, the mass fraction ratio of Ti to W is controlled between 0.39 and 0.52.

[0014] This invention imposes strict limits on the content of residual elements such as P, S, N, and O. The production process is also a major factor affecting the anti-scaling performance of cold-rolled enamel steel. In addition to strictly controlling the chemical composition, the production process must also be strictly controlled to obtain cold-rolled enamel steel with excellent anti-scaling properties.

[0015] This invention also provides a method for preparing the above-mentioned cold-rolled enamel steel with excellent anti-scaling properties, including hot metal pretreatment, converter steelmaking, refining, continuous casting, hot rolling, cold rolling, and annealing, the detailed steps of which are as follows:

[0016] 1. Iron pretreatment: Desulfurize the molten iron to obtain desulfurized molten iron;

[0017] 2. Converter steelmaking: The desulfurized molten iron is transferred to a converter to begin the smelting process;

[0018] 3. Refining: Transfer the product obtained in step 2 to an RH furnace for refining;

[0019] 4. Continuous casting: The product obtained in step 3 is continuously cast;

[0020] 5. Hot rolling: The product obtained in step 4 is hot rolled;

[0021] 6. Cold rolling: The product obtained in step 5 is cold rolled;

[0022] 7. Annealing: Anneal the product obtained in step 6 to obtain the final product.

[0023] Furthermore, the desulfurization process used in the molten iron pretreatment in step 1 is the KR desulfurization process, and the S content of the desulfurized molten iron is less than or equal to 0.006 wt%, which can ensure that the S content in the final cold-rolled enamel steel is less than or equal to 0.010 wt%.

[0024] Furthermore, in step 2, the converter steelmaking process adopts a top and bottom combined blowing + full-process argon blowing process, and the tapping temperature is ≥1650℃;

[0025] Furthermore, in step 3, the vacuum degree during refining should be less than or equal to 15 Pa, and the pure degassing time should be greater than or equal to 10 min;

[0026] Furthermore, in step 4, the billet pulling speed during continuous casting is 0.8–1.0 m / min, the secondary cooling water volume is 0.20–0.30 L / kg, and the crystallizer cooling water volume is 120 ± 10 m³ / min. 3 / h;

[0027] Furthermore, in step 5, the furnace temperature during hot rolling is 1230-1260℃, the rough rolling temperature is above 1050℃, the final rolling temperature is 900-930℃, and the coiling temperature is 680-720℃.

[0028] Furthermore, in step 6, the reduction rate during cold rolling is greater than or equal to 75%;

[0029] Furthermore, in step 7, a continuous annealing process is adopted during annealing. Hydrogen is used for gas protection throughout the annealing process. The annealing heating temperature is 820-840℃, the holding time is 60-120s, and after the holding time is completed, the temperature is cooled to room temperature at a rate of 30-50℃ / s.

[0030] The selection of the cold-rolled enamel steel production process described in this invention is explained as follows:

[0031] The KR desulfurization process is adopted, and the S content of the molten iron should be less than or equal to 0.006% after desulfurization. The converter steelmaking process adopts top and bottom combined blowing + full-process argon blowing. The vacuum degree during RH furnace refining should be less than or equal to 15 Pa, and the pure degassing time should be greater than or equal to 10 min. The main purpose of the above processes is to ensure that the chemical composition meets the requirements.

[0032] During continuous casting, the billet pulling speed is 0.8–1.0 m / min, the secondary cooling water volume is 0.20–0.30 L / kg, and the crystallizer cooling water volume is 120 ± 10 m³ / min. 3 / h, thus ensuring that the surface of the continuously cast billet is free of cracks and defects.

[0033] The furnace temperature is controlled at 1230–1260℃, the roughing temperature is controlled at above 1050℃, the final rolling temperature is controlled at 900–930℃, and the coiling temperature is controlled at 680–720℃. By using the above process, (Ti,W)C precipitates at its smallest size, which can significantly improve the anti-scaling performance.

[0034] The reduction rate during cold rolling should be greater than or equal to 75%. Continuous annealing is used during annealing, with an annealing heating temperature of 820–840℃ and a holding time of 60–120 seconds. After holding, the steel is cooled to room temperature at a rate of 30–50℃ / s. The above cold rolling and annealing processes can impart a high-strength γ-fiber texture to the cold-rolled enamel steel, giving the cold-rolled enamel steel obtained by this invention ultra-deep drawing performance.

[0035] The beneficial effects of this invention are:

[0036] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention adds an appropriate amount of W to the composition of ultra-deep drawing cold-rolled enamel steel, transforming the precipitates in the steel from TiC, Ti4C2S2, and TiS into (Ti,W)C. Compared to TiC, Ti4C2S2, and TiS precipitates, (Ti,W)C precipitates are smaller in size, resulting in higher anti-scaling performance of the enamel steel. Simultaneously, since the cold-rolled enamel steel of this invention does not contain interstitial carbon and nitrogen atoms, it possesses excellent formability, reaching the level of ultra-deep drawing steel formability. Attached Figure Description

[0037] Figure 1 The image shows the microstructure of the cold-rolled enamel steel prepared in Example 1.

[0038] Figure 2 The image shows the microstructure of the cold-rolled enamel steel prepared in Example 2. Detailed Implementation

[0039] The chemical composition of Examples 1 to 8 of the present invention is shown in Table 1. Figure 1 and Figure 2 The images show the microstructures of the cold-rolled enamel steel prepared in Examples 1 and 2 of this invention, respectively. The main production process parameters for Examples 1-8 of this invention are shown in Table 2. The remaining production process parameters are: tapping temperature 1650℃, RH refining vacuum degree 12Pa, RH refining pure degassing time 12min, billet pulling speed during continuous casting 1.0m / min, secondary cooling water ratio 0.25L / kg, and crystallizer cooling water volume 120m³.3 / h. The mechanical properties and anti-scaling properties (TH values) of Examples 1-8 of the present invention are shown in Table 3. Table 3 shows that the yield strength of all examples is ≤165MPa, the tensile strength is between 270 and 300MPa, and the elongation after fracture is greater than 42%. 90 Greater than 2.2, TH value greater than 40 min / mm 2 Furthermore, no scaling or spalling occurred after enameling. Compared to the main performance indicators of ultra-deep drawing steel (yield strength ≤170MPa, tensile strength between 260 and 330MPa),... 90 ≥2.1) It can be found that the forming performance of the cold-rolled enamel steel of the present invention has reached the level of ultra-deep drawing steel.

[0040] Table 1. Chemical composition (mass fraction, %) of Examples 1-8

[0041] Example 1 0.0022 0.01 0.15 0.010 0.008 0.032 0.08 0.20 0.0030 0.0008 Example 2 0.0025 0.02 0.16 0.009 0.008 0.033 0.09 0.23 0.0025 0.0008 Example 3 0.0022 0.02 0.15 0.010 0.006 0.032 0.08 0.16 0.0028 0.0010 Example 4 0.0028 0.01 0.18 0.011 0.007 0.035 0.10 0.25 0.0026 0.0009 Example 5 0.0024 0.01 0.16 0.011 0.006 0.033 0.10 0.22 0.0028 0.0009 Example 6 0.0025 0.01 0.18 0.009 0.005 0.035 0.09 0.23 0.0025 0.0010 Example 7 0.0028 0.02 0.17 0.010 0.008 0.033 0.08 0.20 0.0031 0.0010 Example 8 0.0023 0.02 0.17 0.009 0.005 0.032 0.10 0.25 000026 0.0008

[0042] Table 2 Production process of Examples 1-8

[0043]

[0044]

[0045] Table 3 Mechanical properties and anti-explosion properties of Examples 1-8

[0046]

[0047]

Claims

1. A cold-rolled enamel steel with anti-scaling properties, characterized in that, The chemical composition of the cold-rolled enamel steel with anti-scaling properties, by weight percentage, is: C≤0.003%, Si≤0.02%, Mn: 0.10~0.20%, P≤0.012%, S≤0.010%, Al: 0.02~0.04%, Ti: 0.07~0.10%, 0.39≤Ti / W≤0.52, N≤0.0030%, O≤0.0010%, with the remainder being Fe and unavoidable impurities; the cold-rolled enamel steel with anti-scaling properties contains nano-sized (Ti,W)C precipitates; the yield strength of the cold-rolled enamel steel with anti-scaling properties is 150MPa~165MPa, the tensile strength is 270MPa~300MPa, and the elongation after fracture is 42%~46%, r 90 The concentration was 2.2%~2.3%, and the TH value was 40.5 min / mm. 2 ~45.2 min / mm 2 .

2. The method for preparing a cold-rolled enamel steel with anti-scaling properties as described in claim 1, characterized in that, Specifically, it includes the following steps: (1) Iron pretreatment: desulfurize the iron to obtain desulfurized iron; (2) Converter steelmaking: The desulfurized molten iron is transferred to the converter to start the smelting process; (3) Refining: The product obtained in step (2) is transferred to an RH furnace for refining; (4) Continuous casting: The product obtained in step (3) is continuously cast; (5) Hot rolling: The product obtained in step (4) is hot rolled; (6) Cold rolling: The product obtained in step (5) is cold rolled; (7) Annealing: Anneal the product obtained in step (6) to obtain the final product.

3. The method for preparing cold-rolled enamel steel with anti-scaling properties according to claim 2, characterized in that, In step (1), the desulfurization process used in the pretreatment of molten iron is the KR desulfurization process. The S content of the desulfurized molten iron is less than or equal to 0.006wt%, which ensures that the S content in the final cold-rolled enamel steel is less than or equal to 0.010wt%.

4. The method for preparing cold-rolled enamel steel with anti-scaling properties according to claim 2, characterized in that, In step (2), the converter steelmaking process is top and bottom blowing and full-process argon blowing, and the tapping temperature is greater than or equal to 1650℃.

5. The method for preparing cold-rolled enamel steel with anti-scaling properties according to claim 2, characterized in that, In step (3), The vacuum degree during refining is less than or equal to 15 Pa, and the pure degassing time is greater than or equal to 10 min.

6. The method for preparing a cold-rolled enamel steel with anti-scaling properties according to claim 2, characterized in that, In step (4), the billet pulling speed during continuous casting is 0.8~1.0 m / min, the secondary cooling water volume is 0.20~0.30 L / kg, and the crystallizer cooling water volume is 120±10 m³ / min. 3 / h.

7. The method for preparing cold-rolled enamel steel with anti-scaling properties according to claim 2, characterized in that, In step (5), During hot rolling, the furnace temperature is 1230~1260℃, the rough rolling temperature is above 1050℃, the final rolling temperature is 900~930℃, and the coiling temperature is 680~720℃.

8. The method for preparing cold-rolled enamel steel with anti-scaling properties according to claim 2, characterized in that, In step (6), the reduction rate during cold rolling is greater than or equal to 75%.

9. The method for preparing cold-rolled enamel steel with anti-scaling properties according to claim 2, characterized in that, In step (7), a continuous annealing process is adopted during annealing. Hydrogen is used for gas protection throughout the annealing process. The annealing heating temperature is 820~840℃, the holding time is 60~120s, and after the holding time is completed, the temperature is cooled to room temperature at a rate of 30~50℃ / s.

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