Method for simulating elimination of tin element and weakening of texture and forming performance of ultra-low carbon steel in laboratory

Abstract

The invention discloses a method for simulating elimination of tin element and weakening of texture and forming performance of ultra-low carbon steel in a laboratory, which comprises the following steps: S1, smelting: taking industrial pure iron as a matrix, adding 0.01-0.03% by mass of Sn and 0.01-0.1% by mass of one or two rare earth elements of La and Ce, and smelting to obtain a cast ingot; s2, hot rolling is conducted, specifically, the cast ingot is subjected to hot rolling after being heated and subjected to heat preservation, coiling is conducted after rolling, and air cooling is conducted to the room temperature after coiling; s3, cold rolling is conducted, specifically, surface oxides of the coiled base body are removed, and cold rolling is conducted; and S4, recrystallization annealing is conducted, specifically, recrystallization annealing treatment is conducted on the base body obtained after cold rolling, and crystal grains in the base body obtained after recrystallization annealing are distortionless equiaxed crystal grains. The rare earth element and the element Sn are added to react with each other, segregation of Sn at the grain boundary is inhibited, and therefore the weakening effect of Sn on the ultra-low carbon steel texture and forming performance is relieved; the steel is subjected to large cold rolling reduction and subsequent recrystallization annealing treatment, and the final steel has a high {111} texture and a high plastic strain ratio.

Description

Technical Field

[0001] The invention relates to the technical field of ultra-low carbon steel processing, in particular to a method for laboratory simulation of eliminating tin element weakening of ultra-low carbon steel texture and forming performance. Background Art

[0002] Ultra-low carbon steel forms α texture under large cold rolling reduction ( <110> / / RD) and deformation γ texture ({111} / / ND), and a strong recrystallized γ texture is formed in the subsequent recrystallization annealing process, so that it has a higher n value (work hardening index) and r value (plastic strain ratio), thereby obtaining excellent deep drawing performance and no aging, and is widely used in the automotive industry.

[0003] Smelting ultra-low carbon automotive steel plates based on scrap steel can save energy and significantly reduce carbon emissions, and help the green and low-carbon development of the steel and automobile industry chain. However, in the process of large-scale accumulation and recycling of scrap steel, some residual elements (such as tin, etc.) are difficult to remove in conventional steelmaking methods, and are continuously enriched in steel, which has an adverse effect on the quality of steel. The residual tin element seriously weakens the recrystallized γ texture of ultra-low carbon steel, reduces its n value and r value, and is not conducive to the cold plastic deformation processing of ultra-low carbon steel. In addition, the adverse effects of residual tin on the texture and forming properties of ultra-low carbon steel are difficult to reduce and eliminate through deformation and annealing processes, which restricts the application prospects of ultra-low carbon automotive steel plates produced with scrap steel as raw materials.

[0004] Therefore, it is urgent to provide a solution for laboratory simulation of eliminating the weakening of the texture and forming properties of ultra-low carbon steel by tin elements. Summary of the invention

[0005] In order to solve the above problems, the technical solution of the present invention provides a method for laboratory simulation to eliminate the weakening of the texture and formability of ultra-low carbon steel by tin elements, thereby improving the formability of ultra-low carbon steel.

[0006] According to a first aspect of the technical solution of the present invention, there is provided a method for simulating in a laboratory the elimination of the weakening of the texture and forming performance of ultra-low carbon steel by tin elements, comprising:

[0007] S1. Smelting: using industrial pure iron as a matrix, adding 0.01% to 0.03% Sn and 0.01% to 0.1% of one or two rare earth elements selected from La and Ce, and smelting to obtain an ingot;

[0008] S2, hot rolling: heating and keeping the ingot warm, hot rolling it, coiling it, and air cooling it to room temperature after coiling it;

[0009] S3, cold rolling: removing the surface oxide of the substrate after coiling, and performing cold rolling;

[0010] S4, recrystallization annealing: the cold-rolled matrix is ​​subjected to recrystallization annealing treatment, and the grains in the matrix after the recrystallization annealing are equiaxed grains without distortion.

[0011] In the above scheme, in step S1, the purity of the industrial pure iron, Sn, La and Ce is 99.99%.

[0012] In the above scheme, in step S1, the substrate is placed in a vacuum arc furnace at 5×10- 5 The melting is carried out under a vacuum degree of Pa.

[0013] In the above scheme, in step S2, the ingot is heated to 1000°C and kept at this temperature for 2 hours before hot rolling.

[0014] In the above scheme, in step S2, the initial temperature of the hot rolling is 950°C to 1000°C, the final rolling temperature is 830°C to 860°C, and the hot rolling reduction ratio is 65% to 70%.

[0015] In the above scheme, in step S2, the coiling temperature is 600°C to 650°C, and the coiling time is 30 minutes.

[0016] In the above scheme, in step S3, the cold rolling reduction ratio is 80% to 85%, and the thickness of the substrate after cold rolling is 0.9 mm to 1.1 mm.

[0017] In the above scheme, in step S4, the annealing temperature is 600° C. to 650° C., and the annealing time is 30 minutes.

[0018] In the above scheme, in step S4, the recrystallization annealing treatment is performed by heating in a box furnace.

[0019] According to a second aspect of the technical solution of the present invention, there is provided an ultra-low carbon steel, which is manufactured by using the laboratory simulation method described in any one of the above schemes to eliminate the weakening of the texture and forming properties of the ultra-low carbon steel by tin elements.

[0020] Beneficial effects of the present invention:

[0021] The invention discloses a method for laboratory simulation of eliminating the weakening of the texture and forming performance of ultra-low carbon steel by tin element, wherein rare earth elements are added to react with element Sn to inhibit the segregation of Sn at grain boundaries, thereby reducing the weakening effect of Sn on the texture and forming performance of ultra-low carbon steel; the steel is subjected to large cold rolling and pressing to form a fiber-like long strip deformation structure, and the subsequent recrystallization annealing treatment is transformed into fine equiaxed grains, eliminating work hardening, reducing strength and improving plasticity, and finally the steel has a strong {111} texture and a high plastic strain ratio, thereby obtaining good forming performance, and adding rare earth elements can further improve the forming performance of ultra-low carbon steel, thereby improving the yield strength, tensile strength and elongation of the steel plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0023] Figure 1 This is an ODF diagram of the ultra-low carbon steel after recrystallization annealing according to Example 1 of the present invention;

[0024] Figure 2 This is an ODF diagram of the ultra-low carbon steel after recrystallization annealing according to Example 2 of the present invention;

[0025] Figure 3 This is an ODF diagram of the ultra-low carbon steel after recrystallization annealing according to Example 3 of the present invention;

[0026] Figure 4 This is an ODF diagram of the ultra-low carbon steel of Example 4 of the present invention after recrystallization annealing;

[0027] Figure 5 This is an ODF diagram of the ultra-low carbon steel of Example 5 of the present invention after recrystallization annealing;

[0028] Figure 6 This is an ODF diagram of the ultra-low carbon steel of Comparative Example 1 of the present invention after recrystallization annealing;

[0029] Figure 7 This is an ODF diagram of the ultra-low carbon steel of Comparative Example 2 of the present invention after recrystallization annealing;

[0030] Figure 8 This is the ODF diagram of the ultra-low carbon steel of comparative example 3 of the present invention after recrystallization annealing.

[0031] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0032] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0033] The terms "first", "second", etc. in the specification and claims of the present disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or described herein, for example.

[0034] In addition, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements explicitly listed, but may include other steps or elements not explicitly listed or inherent to such process, method, product, or apparatus.

[0035] Multiple includes two or more.

[0036] It should be understood that the term "and / or" used in this disclosure is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone.

[0037] An embodiment of the technical solution of the present invention provides a method for laboratory simulation of eliminating the weakening of the texture and formability of ultra-low carbon steel by tin elements, comprising:

[0038] S1. Smelting: using industrial pure iron as a matrix, adding 0.01% to 0.03% Sn and 0.01% to 0.1% of one or two rare earth elements selected from La and Ce, and smelting to obtain an ingot;

[0039] S2, hot rolling: the ingot is heated and kept warm before hot rolling, coiled after rolling, and air-cooled to room temperature after coiling;

[0040] S3, cold rolling: removing the surface oxide of the substrate after coiling and performing cold rolling;

[0041] S4, recrystallization annealing: the cold-rolled matrix is ​​subjected to recrystallization annealing treatment, and the grains in the matrix after recrystallization annealing are equiaxed grains without distortion.

[0042] In step S1, the purity of industrial pure iron, Sn, La and Ce is 99.99%.

[0043] Since the content of C and N interstitial atoms in ultra-low carbon steel is very low, refining is required during the smelting process, but it is difficult to achieve this condition in laboratory smelting. The content of other elements in industrial pure iron is low, and the carbon content is closer to ultra-low carbon steel. Therefore, industrial pure iron is used to add Sn element to simulate ultra-low carbon steel.

[0044] In step S1, the substrate is placed in a vacuum arc furnace at 5×10 -5 The melting is carried out under a vacuum degree of Pa.

[0045] In step S2, the ingot is heated to 1000°C and kept at this temperature for 2 hours before hot rolling.

[0046] In step S2, the initial temperature of hot rolling is 950°C to 1000°C, the final rolling temperature is 830°C to 860°C, and the hot rolling reduction ratio is 65% to 70%.

[0047] In step S2, the coiling temperature is 600°C to 650°C, and the coiling time is 30 minutes.

[0048] In step S3, the cold rolling reduction ratio is 80% to 85%, and the thickness of the substrate after cold rolling is 0.9 mm to 1.1 mm, preferably 1 mm. The number of cold rolling times is 8 to 12 times, preferably 10 times.

[0049] In step S4, the annealing temperature is 600° C. to 650° C., and the annealing time is 30 minutes.

[0050] In step S4, the recrystallization annealing treatment is performed by heating in a box-type furnace.

[0051] After annealing, the formability of the ultra-low carbon steel plate is evaluated by uniaxial tension. Specifically, the n value (work hardening index) and r value (plastic strain ratio) are evaluated. The r value is measured and calculated using a vernier caliper.

[0052] According to a second aspect of the technical solution of the present invention, there is provided an ultra-low carbon steel, which is manufactured by using the above-mentioned laboratory simulation method to eliminate the weakening of the texture and forming performance of the ultra-low carbon steel by the tin element.

[0053] Example 1

[0054] The laboratory simulation method of eliminating the weakening of the texture and forming performance of ultra-low carbon steel by tin elements in this embodiment includes the following production steps: First, industrial pure iron is used as the matrix, 0.03% Sn and 0.017% La are added by mass fraction, and a vacuum arc furnace is used for smelting to obtain a suction casting ingot. The ingot is heated to 1200°C, kept warm for 2 hours, and then hot rolled. The hot rolling reduction is 66.7%, the final rolling temperature is 850°C, and the temperature is kept at 600°C for 30 minutes after rolling, and then air-cooled to room temperature. Then, the hot-rolled plate is cold-rolled with a deformation of 80% to obtain a cold-rolled sheet with a thickness of 1 mm. The cold-rolled plate is heated to 600°C and kept warm for 30 minutes for recrystallization annealing.

[0055] Example 2

[0056] The laboratory simulation method of eliminating the weakening of the texture and forming performance of ultra-low carbon steel by tin elements in this embodiment includes the following production steps: First, industrial pure iron is used as the matrix, 0.03% Sn and 0.034% La are added by mass fraction, and a vacuum arc furnace is used for smelting to obtain a suction casting ingot. The ingot is heated to 1200°C, kept warm for 2 hours, and then hot rolled. The hot rolling reduction is 66.7%, the final rolling temperature is 850°C, and the temperature is kept at 600°C for 30 minutes after rolling, and then air-cooled to room temperature. Then, the hot-rolled plate is cold-rolled with a deformation of 80% to obtain a cold-rolled sheet with a thickness of 1 mm. The cold-rolled plate is heated to 600°C and kept warm for 30 minutes for recrystallization annealing.

[0057] Example 3

[0058] The laboratory simulation method of eliminating the weakening of the texture and forming performance of ultra-low carbon steel by tin elements in this embodiment includes the following production steps: First, industrial pure iron is used as the matrix, 0.03% Sn and 0.102% La are added by mass fraction, and a vacuum arc furnace is used for smelting to obtain a suction casting ingot. The ingot is heated to 1200°C, kept warm for 2 hours, and then hot rolled. The hot rolling reduction is 66.7%, the final rolling temperature is 850°C, and the temperature is kept at 600°C for 30 minutes after rolling, and then air-cooled to room temperature. Then, the hot-rolled plate is cold-rolled with a deformation of 80% to obtain a cold-rolled sheet with a thickness of 1 mm. The cold-rolled plate is heated to 600°C and kept warm for 30 minutes for recrystallization annealing.

[0059] Example 4

[0060] The laboratory simulation method of eliminating the weakening of the texture and forming performance of ultra-low carbon steel by tin elements in this embodiment includes the following production steps: First, industrial pure iron is used as the matrix, 0.01% Sn and 0.041% La are added by mass fraction, and a vacuum arc furnace is used for smelting to obtain a suction casting ingot. The ingot is heated to 1200°C, kept warm for 2 hours, and then hot rolled. The hot rolling reduction is 66.7%, the final rolling temperature is 850°C, and the temperature is kept at 600°C for 30 minutes after rolling, and then air-cooled to room temperature. Then, the hot-rolled plate is cold-rolled with a deformation of 80% to obtain a cold-rolled sheet with a thickness of 1 mm. The cold-rolled plate is heated to 600°C and kept warm for 30 minutes for recrystallization annealing.

[0061] Example 5

[0062] The laboratory simulation method of eliminating the weakening of the texture and forming performance of ultra-low carbon steel by tin elements in this embodiment includes the following production steps: First, industrial pure iron is used as the matrix, 0.03% Sn and 0.062% La+0.043% Ce are added by mass fraction, and a vacuum arc furnace is used for smelting to obtain a suction casting ingot. The ingot is heated to 1200°C, kept warm for 2 hours, and then hot rolled. The hot rolling reduction is 66.7%, the final rolling temperature is 850°C, and the temperature is kept at 600°C for 30 minutes after rolling, and then air-cooled to room temperature. Then, the hot-rolled plate is cold-rolled with a deformation of 80% to obtain a cold-rolled sheet with a thickness of 1 mm. The cold-rolled plate is heated to 600°C and kept warm for 2 hours for recrystallization annealing.

[0063] Comparative Example 1

[0064] In this comparative example, industrial pure iron is used as the matrix, Sn with a mass fraction of 0.01% is added, and a vacuum arc furnace is used for smelting to obtain a suction casting ingot. The ingot is heated to 1200°C, kept warm for 2 hours, and then hot rolled. The hot rolling reduction is 66.7%, the final rolling temperature is 850°C, and the temperature is kept at 600°C for 30 minutes after rolling, and then air-cooled to room temperature. Then, the hot-rolled plate is cold-rolled with a deformation of 80% to obtain a cold-rolled sheet with a thickness of 1 mm. The cold-rolled plate is heated to 600°C and kept warm for 30 minutes for recrystallization annealing.

[0065] Comparative Example 2

[0066] In this comparative example, industrial pure iron is used as the matrix, Sn with a mass fraction of 0.03% is added, and a vacuum arc furnace is used for smelting to obtain a suction casting ingot. The ingot is heated to 1200°C, kept warm for 2 hours, and then hot rolled. The hot rolling reduction is 66.7%, the final rolling temperature is 850°C, and the temperature is kept at 600°C for 30 minutes after rolling, and then air-cooled to room temperature. Then, the hot-rolled plate is cold-rolled with a deformation of 80% to obtain a cold-rolled sheet with a thickness of 1 mm. The cold-rolled plate is heated to 600°C and kept warm for 30 minutes for recrystallization annealing.

[0067] Comparative Example 3

[0068] In this comparative example, industrial pure iron is used as the matrix, Sn is not added, and a vacuum arc furnace is used for smelting to obtain a suction cast ingot. The ingot is heated to 1200°C, kept warm for 2 hours, and then hot rolled. The hot rolling reduction is 66.7%, the final rolling temperature is 850°C, and the temperature is kept at 600°C for 30 minutes after rolling, and then air-cooled to room temperature. Then, the hot-rolled plate is cold-rolled with a deformation of 80% to obtain a cold-rolled sheet with a thickness of 1 mm. The cold-rolled sheet is heated to 600°C and kept warm for 30 minutes for recrystallization annealing.

[0069] The following tests were performed on Examples 1 to 5 and Comparative Examples 1 to 3 respectively:

[0070] Texture test: Samples were taken from the recrystallized annealed sheets obtained in Examples 1 to 5 and Comparative Examples 1 to 3 on the TD plane (the plane formed by the rolling direction and the normal direction) and the texture was tested by Electron Scatter Diffraction (EBSD). The results are shown in Figure 2. Figures 1 to 8 As shown, Sn weakens the recrystallized γ texture of ultra-low carbon steel, and the γ texture strength of the Sn-containing ultra-low carbon steel plate in the embodiment is improved after adding different contents of rare earth.

[0071] Forming performance test: For the recrystallized annealed plates obtained in the above-mentioned Examples 1 to 5 and Comparative Examples 1 to 3, tensile samples were taken along the rolling direction on the rolling surface (the plane formed by the rolling direction and the transverse direction), and their n value and r value were measured and calculated by uniaxial tensile test. The forming performance of ultra-low carbon steel was evaluated in this way. The results are shown in Table 1. Compared with Comparative Example 3, the addition of Sn in Comparative Examples 1 and 2 reduced the n value and r value of ultra-low carbon steel. The r value of the Sn-containing ultra-low carbon steel added with rare earth in Examples 1 to 5 was greater than that of the ultra-low carbon steel without rare earth added in Comparative Examples 1 to 2. Among them, the content of Sn added in Examples 1 to 3 and Example 5 was the same as that in Comparative Example 2, and the n value and r value of Examples 1 to 3 and Example 5 were significantly improved compared with Comparative Example 2. The content of Sn added in Example 4 was the same as that in Comparative Example 1, and the r value of Example 4 was significantly improved compared with Comparative Example 1.

[0072] Table 1

[0073] Serial number n value r-value Example 1 0.303 2.68 Example 2 0.316 2.74 Example 3 0.293 2.84 Example 4 0.263 2.90 Example 5 0.305 3.06 Comparative Example 1 0.291 2.73 Comparative Example 2 0.287 2.39 Comparative Example 3 0.294 3.18

[0074] In summary, the texture and formability of the ultra-low carbon steel containing the element Sn are restored after adding different amounts of rare earth as described in the present invention, indicating that the phenomenon that the residual element Sn weakens the formability of the ultra-low carbon steel can be improved by adding rare earth. The ultra-low carbon steel plates according to the present invention all show excellent formability.

[0075] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0076] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0077] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in each embodiment of the present invention.

[0078] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A method for simulating in a laboratory the elimination of the weakening of the texture and formability of ultra-low carbon steel by tin elements, characterized in that: include: S1. Smelting: using industrial pure iron as a matrix, adding 0.01% to 0.03% Sn and 0.01% to 0.1% of one or two rare earth elements selected from La and Ce, and smelting to obtain an ingot; S2, hot rolling: heating and keeping the ingot warm, hot rolling it, coiling it, and air cooling it to room temperature after coiling it; S3, cold rolling: removing the surface oxide of the substrate after coiling, and performing cold rolling; S4, recrystallization annealing: the cold-rolled matrix is ​​subjected to recrystallization annealing treatment, and the grains in the matrix after the recrystallization annealing are equiaxed grains without distortion.

2. The method for laboratory simulation of eliminating the weakening of ultra-low carbon steel texture and formability by tin element according to claim 1, characterized in that: In step S1, the purity of the industrial pure iron, Sn, La and Ce is 99.99%.

3. The method for laboratory simulation of eliminating the weakening of ultra-low carbon steel texture and formability by tin element according to claim 1, characterized in that: In step S1, the substrate is placed in a vacuum arc furnace at 5×10 -5 The melting is carried out under a vacuum degree of Pa.

4. The method for laboratory simulation of eliminating the weakening of ultra-low carbon steel texture and formability by tin element according to claim 1, characterized in that: In step S2, the ingot is heated to 1000°C and kept at this temperature for 2 hours before hot rolling.

5. The method for laboratory simulation of eliminating the weakening of ultra-low carbon steel texture and formability by tin element according to claim 1, characterized in that: In step S2, the initial temperature of the hot rolling is 950°C to 1000°C, the final rolling temperature is 830°C to 860°C, and the hot rolling reduction ratio is 65% to 70%.

6. The method for laboratory simulation of eliminating the weakening of ultra-low carbon steel texture and formability by tin element according to claim 1, characterized in that: In step S2, the coiling temperature is 600°C to 650°C, and the coiling time is 30 minutes.

7. The method for laboratory simulation of eliminating the weakening of ultra-low carbon steel texture and formability by tin element according to claim 1, characterized in that: In step S3, the cold rolling reduction ratio is 80% to 85%, and the thickness of the substrate after cold rolling is 0.9 mm to 1.1 mm.

8. The method for laboratory simulation of eliminating the weakening of ultra-low carbon steel texture and formability by tin element according to claim 1, characterized in that: In step S4, the annealing temperature is 600° C. to 650° C., and the annealing time is 30 minutes.

9. The method for laboratory simulation of eliminating the weakening of ultra-low carbon steel texture and formability by tin element according to claim 1, characterized in that: In step S4, the recrystallization annealing treatment is performed by heating in a box-type furnace.

10. An ultra-low carbon steel, characterized in that: The steel is manufactured by using the laboratory simulation method for eliminating the weakening of the texture and forming performance of ultra-low carbon steel by tin elements as described in any one of claims 1 to 9.

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