Preparation method of medium-high carbon steel

Abstract

The invention provides a preparation method of medium-high carbon steel. The preparation method comprises the following steps that a medium-high carbon steel plate is sequentially subjected to heating solution treatment, hot rolling treatment, coiling, acid pickling and cold rolling treatment, and medium-high carbon steel is prepared; wherein the temperature of the heating solution treatment ranges from 1150 DEG C to 1200 DEG C, the outlet temperature of the hot rolling treatment ranges from 850 DEG C to 900 DEG C, and the coiling temperature ranges from 600 DEG C to 650 DEG C. The preparation method can improve the surface quality of the pickled steel, and weakens or even eliminates the white spot defect of the pickled surface.

Description

Technical Field

[0001] The invention relates to the technical field of alloys, and in particular to a method for preparing medium-high carbon steel. Background Art

[0002] Medium-high carbon steel is one of the commonly used steels for hardware tools, electronic parts and automotive parts, but the white oxide residue on the surface will make the parts unsightly and affect the electroplating process. There are many methods to improve the oxide content of strip steel in traditional technology. For example, by adopting strong deoxidation with aluminum during steel tapping, adding high-alumina high-basicity refining slag system, weak stirring of argon and vacuum treatment, etc., rapid slag formation, good deoxidation and adsorption of inclusions are achieved, and the floating time of inclusions in the refining process is guaranteed. At the same time, by specifying the order of adding materials and avoiding exposed oxidation, the purity and quality of steel are further improved. This method can effectively control the oxygen content, the level and content of inclusions in steel, thereby improving the purity of steel, but it mainly controls the generation of oxides during the smelting process of molten steel, and it is difficult to effectively reduce the probability of iron scale during rolling pickling. Traditional technology pays little attention to improving the residual oxide on the pickling surface of medium-high carbon steel, and even if there is, it mostly involves wear-resistant steel. How to effectively reduce the generation of oxides during the pickling and rolling of medium-high carbon steel strip is a problem that still needs to be solved.

[0003] Therefore, the traditional technology still needs to be improved. Summary of the invention

[0004] Based on this, the present application provides a method for preparing medium-high carbon steel, which can effectively reduce the generation of oxides during the pickling and rolling process of medium-high carbon steel strip.

[0005] The technical solution of this application is as follows.

[0006] In a first aspect of the present application, a method for preparing medium-high carbon steel is provided, comprising the following steps:

[0007] The medium-high carbon steel plate is subjected to heating solution treatment, hot rolling treatment, coiling, pickling, and cold rolling treatment in sequence to prepare the medium-high carbon steel;

[0008] Wherein, the temperature of the heating solution treatment is 1150°C to 1200°C, the outlet temperature of the hot rolling treatment is 850°C to 900°C, and the coiling temperature is 600°C to 650°C.

[0009] In the above method, the temperature of the heating solution treatment, hot rolling treatment and coiling is controlled to be kept within an appropriate range lower than the control temperature of the traditional technology. While ensuring the strength of the steel, the thickness of the iron oxide scale formed in the hot rolling process is effectively reduced, the iron oxide scale is made loose, the surface quality of the steel after pickling is improved, and the white spot defects on the pickling surface are weakened or even eliminated.

[0010] At the same time, lowering the temperature of heating solution treatment, hot rolling treatment and coiling is also beneficial to reducing production costs.

[0011] In some embodiments, after the hot rolling step and before the coiling step, the following steps are further included:

[0012] The medium-high carbon steel plate subjected to the hot rolling treatment is subjected to laminar cooling treatment;

[0013] Wherein, during the laminar cooling process, two groups of interval sparse cooling modes are adopted in the front stage.

[0014] The cooling mode of the front section of the laminar cooling treatment is further regulated to further reduce the residual amount of white oxide during the cooling process.

[0015] In some of the embodiments, in the two groups of interval sparse cooling modes, the cooling time is 1 min to 3 min.

[0016] In some of the embodiments, in the pickling step, the pickling speed is 50 m / min to 100 m / min.

[0017] The pickling speed in the pickling step is further regulated, and the contact time between the oxidized iron scale and the pickling solution is prolonged by appropriately reducing the pickling speed, thereby improving the pickling effect on the oxidized iron scale.

[0018] In some embodiments, the heating solution treatment time is 30 min to 60 min.

[0019] In some embodiments, the hot rolling treatment time is 1 min to 3 min.

[0020] In some embodiments, the cold rolling treatment is performed at a temperature of 30° C. to 80° C. and for a time of 30 min to 60 min.

[0021] In some of the embodiments, the components of the medium-high carbon steel plate include, by mass percentage, 0.2%-1.0% C, 0.1%-0.50% Si, 0.1%-1.4% Mn, P≤0.02%, S≤0.02%, 0<Cr+Ni+Mo≤2.0%, 0<Al≤0.06% and the remainder Fe and unavoidable impurities.

[0022] In some of the embodiments, the medium-high carbon steel plate has a thickness of 0.3 mm to 10 mm and a width of 900 mm to 2250 mm.

[0023] In some of the embodiments, the medium-high carbon steel plate includes any one of S35C continuous casting slab and 65MN continuous casting slab. DETAILED DESCRIPTION

[0024] For ease of understanding of the present application, the present application will be described more fully below, and preferred embodiments of the present application are provided. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0026] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0027] The "range" disclosed in the present application can be defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values, and any end value can be included or excluded independently, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a specific parameter, it is understood that the range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are also listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to listing the parameter as, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is expressed as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9 and 10.

[0028] In this application, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel schemes of "yes" or "no". If there are multiple "options" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "option" is independent.

[0029] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0030] One embodiment of the present application provides a method for preparing medium-high carbon steel, comprising the following step S10.

[0031] S10: The medium-high carbon steel plate is subjected to heating solution treatment, hot rolling treatment, coiling, pickling, and cold rolling treatment in sequence to prepare medium-high carbon steel.

[0032] The temperature of the heating solution treatment is 1150°C to 1200°C, the outlet temperature of the hot rolling treatment is 850°C to 900°C, and the coiling temperature is 600°C to 650°C.

[0033] In the above method, the temperature of the heating solution treatment, hot rolling treatment and coiling is controlled to be kept within an appropriate range lower than the control temperature of the traditional technology. While ensuring the strength of the steel, the thickness of the iron oxide scale formed in the hot rolling process is effectively reduced, the iron oxide scale is made loose, the surface quality of the steel after pickling is improved, and the white spot defects on the pickling surface are weakened or even eliminated.

[0034] At the same time, lowering the temperature of heating solution treatment, hot rolling treatment and coiling is also beneficial to reducing production costs.

[0035] Optionally, the temperature of the heating solution treatment may be 1150°C, 1160°C, 1170°C, 1180°C, 1190°C, or 1195°C.

[0036] Optionally, the outlet temperature of the hot rolling process may be 850°C, 860°C, 870°C, 880°C, 890°C, 895°C.

[0037] Optionally, the coiling temperature may be 600°C, 610°C, 620°C, 630°C, 640°C, or 645°C.

[0038] In some embodiments, after the hot rolling step and before the coiling step, the following step S21 is further included:

[0039] S21: subjecting the hot-rolled medium-high carbon steel plate to laminar cooling.

[0040] Among them, during the laminar cooling process, two groups of interval sparse cooling modes are adopted in the front stage.

[0041] When laminar header cooling is used, two methods, dense cooling and sparse cooling, can be used according to the arrangement of the headers. Sparse cooling refers to a cooling method in which the headers are opened at intervals, also known as interval sparse cooling, which can be spaced one or more headers.

[0042] In traditional technology, when laminar cooling is performed on steel plates after hot rolling, centralized cooling is often used in the front section. The heat conduction inside the steel plate is much lower than the convective heat exchange on the surface of the steel plate, resulting in a large temperature difference between the surface and the center of the steel plate during cooling, which leads to uneven internal structure of the steel plate and easy generation of iron oxide scale. However, during sparse cooling, there is an air cooling section in the middle of the water cooling section, so that the steel plate can return to temperature in time during air cooling, making the temperature of the entire steel plate uniform, which can reduce the probability of iron oxide scale generation.

[0043] In some of the embodiments, in the two-group interval sparse cooling mode, the cooling time is 1 min to 3 min.

[0044] Furthermore, there is no particular requirement for the cooling method in the latter stage of the laminar cooling treatment.

[0045] In some of the embodiments, in the pickling step, the pickling speed is 50 m / min to 100 m / min.

[0046] The pickling speed in the pickling step is further regulated, and the contact time between the oxidized iron scale and the pickling solution is prolonged by appropriately reducing the pickling speed, thereby improving the pickling effect on the oxidized iron scale.

[0047] Optionally, the pickling speed may be 50 m / min, 60 m / min, 65 m / min, 70 m / min, 80 m / min, 90 m / min, or 95 m / min.

[0048] In some embodiments, the heating solution treatment time is 30 min to 60 min.

[0049] In some embodiments, the hot rolling treatment time is 1 min to 3 min.

[0050] In some embodiments, the cold rolling treatment is performed at a temperature of 30° C. to 80° C. and for a time of 30 min to 60 min.

[0051] In some of the embodiments, the components of the medium-high carbon steel plate include, by mass percentage, 0.2%-1.0% C, 0.1%-0.50% Si, 0.1%-1.4% Mn, P≤0.02%, S≤0.02%, 0<Cr+Ni+Mo≤2.0%, 0<Al≤0.06% and the balance Fe and unavoidable impurities.

[0052] In some of the embodiments, the medium-high carbon steel plate has a thickness of 0.3 mm to 10 mm and a width of 900 mm to 2250 mm.

[0053] In some of the embodiments, the medium-high carbon steel plate includes any one of S35C continuous casting slab and 65MN continuous casting slab.

[0054] The present application will be described below in conjunction with specific embodiments, but the present application is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present application. Under the guidance of the concept of the present application, technical personnel in the field should realize that certain changes made to the various embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0055] The following are specific embodiments.

[0056] Example 1

[0057] (1) Taking S35C continuous casting steel slab as raw material, the chemical composition and its mass percentage are as follows:

[0058] C: 0.32%, Si: 0.13%, Mn: 0.55%, S: 0.002%, P: 0.01%, Al: 0.03%, Cr: 0.15%, Cu: 0.05%, Ni: 0.02%, the rest is Fe and unavoidable impurities. Strip specifications: 3.2mm thick × 2250mm wide.

[0059] (2) The S35C continuous casting steel slab was subjected to heating solution treatment, hot rolling treatment to 3 mm, laminar cooling, coiling, pickling, and cold rolling treatment in sequence. The heating furnace solution temperature was 1180°C and the time was 40 min. The outlet temperature of the hot rolling treatment was 860°C and the hot rolling treatment time was 1 min. The laminar cooling was cooled by two groups of interval sparse cooling for 2 min until the coiling temperature reached 620°C. The pickling speed was 60 m / min. S35C steel was obtained after cold rolling. The cold rolling treatment temperature was 50°C and the time was 50 min.

[0060] (3) During the pickling process, the residual oxide white spots on the steel surface were observed. The specific results are shown in Table 1.

[0061] Example 2

[0062] (1) Taking 65MN continuous casting steel slab as raw material, the chemical composition and mass percentage of the strip steel are as follows:

[0063] C: 0.63%, Si: 0.37%, Mn: 0.45%, S: 0.003%, P: 0.02%, Al: 0.05%, Cr: 0.15%, Cu: 0.05%, Ni: 0.02%, Ti: 0.003%, the rest are Fe and unavoidable impurities. The specifications of the continuous casting steel slab are 2.8mm×2250mm.

[0064] (2) The 65MN continuous casting steel slab was subjected to heating solution treatment, hot rolling treatment to 3.2 mm, laminar cooling, coiling, pickling, and cold rolling treatment in sequence. The heating furnace solution temperature was 1190°C and the time was 60 min. The outlet temperature of the hot rolling treatment was 800°C and the hot rolling treatment time was 3 min. The laminar cooling was cooled by two groups of interval sparse cooling for 3 min to the coiling temperature of 650°C. The pickling speed was 80 m / min. After cold rolling, 65MN steel was obtained. The cold rolling treatment temperature was 80°C and the time was 60 min.

[0065] (3) During the pickling process, the residual oxide white spots on the steel surface were observed. The specific results are shown in Table 1.

[0066] Comparative Example 1

[0067] Comparative Example 1 is basically the same as Example 1, except that the solid solution temperature of the heating furnace is 1230°C, the outlet temperature of the hot rolling treatment is 920°C, the front section of the laminar cooling adopts centralized cooling to cool to the coiling temperature of 680°C, and the pickling speed is 11m / min.

[0068] The other steps and conditions are the same as those in Example 1. Please see Table 1 for specific results.

[0069] Comparative Example 2

[0070] Comparative Example 2 is basically the same as Example 2, except that the solid solution temperature of the heating furnace is 1250°C, the outlet temperature of the hot rolling treatment is 950°C, the front section of the laminar cooling is cooled to a coiling temperature of 690°C by two groups of interval sparse cooling, and the pickling speed is 100m / min.

[0071] The other steps and conditions are the same as those in Example 2. Please see Table 1 for specific results.

[0072] The thickness, surface oxide residue, and iron oxide scale thickness of the medium-high carbon steels prepared in the embodiments and comparative examples are shown in Table 1.

[0073] Table 1

[0074] serial number Thickness / mm Surface oxide residue Iron oxide thickness / μm Example 1 3.2 The board surface is clean, without white residue 0 Example 2 2.8 The board surface is clean, without white residue 0 Comparative Example 1 3.2 Flake white oxides remain on the board surface 14 Comparative Example 2 2.8 Flake white oxides remain on the board surface 18

[0075] It can be seen from the results in Table 1 that the technical solution of the present application can improve the surface quality of steel after pickling, and reduce or even eliminate white spot defects on the pickling surface.

[0076] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0077] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of this patent shall be subject to the attached claims.

Claims

1. A method for preparing medium-high carbon steel, characterized in that: The steps include: The medium-high carbon steel plate is subjected to heating solution treatment, hot rolling treatment, coiling, pickling, and cold rolling treatment in sequence to prepare the medium-high carbon steel; Wherein, the temperature of the heating solution treatment is 1150°C to 1200°C, the outlet temperature of the hot rolling treatment is 850°C to 900°C, and the coiling temperature is 600°C to 650°C.

2. The method for preparing medium-high carbon steel according to claim 1, characterized in that: After the hot rolling step and before the coiling step, the method further includes the following steps: The medium-high carbon steel plate subjected to the hot rolling treatment is subjected to laminar cooling treatment; Wherein, during the laminar cooling process, two groups of interval sparse cooling modes are adopted in the front stage.

3. The method for preparing medium-high carbon steel according to claim 2, characterized in that: In the two groups of interval sparse cooling modes, the cooling time is 1 min to 3 min.

4. The method for preparing medium-high carbon steel according to any one of claims 1 to 3, characterized in that: In the pickling step, the pickling speed is 50m / min to 100m / min.

5. The method for preparing medium-high carbon steel according to any one of claims 1 to 3, characterized in that: The time of the heating solution treatment is 30 min to 60 min.

6. The method for preparing medium-high carbon steel according to any one of claims 1 to 3, characterized in that: The hot rolling treatment time is 1 min to 3 min.

7. The method for preparing medium-high carbon steel according to claim 6, characterized in that: The temperature of the cold rolling treatment is 30° C. to 80° C., and the time is 30 min to 60 min.

8. The method for preparing medium-high carbon steel according to any one of claims 1 to 3, characterized in that: Calculated by mass percentage, the components of the medium-high carbon steel plate include: 0.2% to 1.0% C, 0.1% to 0.50% Si, 0.1% to 1.4% Mn, P≤0.02%, S≤0.02%, 0<Cr+Ni+Mo≤2.0%, 0<Al≤0.06% and the remainder Fe and unavoidable impurities.

9. The method for preparing medium-high carbon steel according to any one of claims 1 to 3, characterized in that: The medium-high carbon steel plate has a thickness of 0.3 mm to 10 mm and a width of 900 mm to 2250 mm.

10. The method for preparing medium-high carbon steel according to any one of claims 1 to 3, characterized in that: The medium-high carbon steel plate includes any one of S35C continuous casting slab and 65MN continuous casting slab.