Tinplate and its manufacturing method

Abstract

The present application belongs to the technical field of alloy materials, and specifically relates to tinplate and its manufacturing method. The manufacturing method of tinplate according to the present application adopts the composition design of low carbon aluminum killed steel, designs the contents of elements such as C, Mn, Al and N in tinplate without increasing the alloy content and the difficulty of controlling production, and combines with the corresponding processes of hot rolling, cold rolling, annealing and flattening, fully utilizes the strengthening effect of traditional elements carbon and manganese, combines with the control of aluminum nitride precipitation in hot rolling, selects a suitable cold rolling reduction, controls the ferrite grain size and cementite precipitation in steel by continuous annealing and overaging treatment, and combines with a specific flattening process to produce tinplate with small change in strength and hardness, high elongation and short yield platform, and the tin content of the alloy is reasonably controlled, and the requirements for press formability, pressure resistance and surface gloss of the top cover of an aerosol can are met, and the composition of the tinplate is simple, the process is simple and easy to implement, and the production cost is low.

Description

[Technical field]

[0001] The present application is in the technical field of alloy materials, and in particular, relates to tinplate and its manufacturing method.

[0002] This application claims priority to a Chinese patent application bearing application number 202211264096.3 and entitled "Tinplate and its manufacturing method" filed with the China Patent Office on October 17, 2022, the entire contents of which are incorporated herein by reference. [Background technology]

[0003] An aerosol can is a metal packaging container for storing various reagent products such as air purifiers and insecticides, and is composed of three parts: a top cover, a can body, and a bottom cover. Among them, the top cover is the most complicated to deform, and is generally obtained by performing press deformation processing multiple times using tinplate with a thickness of 0.30 to 0.45 mm. The requirements for press formability of the tinplate are high, and if the strength (or hardness) of the tinplate is too high, ridging is likely to occur during pressing. In addition, after the top cover is connected to the can body and the bottom cover, it is subjected to pressure from the reagents filled in the can, so the tinplate must have a certain strength (or hardness). In particular, in the case of high-pressure aerosol cans, the requirements for pressure resistance are higher, and the desired strength of the tinplate is correspondingly higher. In addition, since the top cover is an exterior part, a transparent paint is applied to the surface to maintain metallic luster, and it is also necessary to maintain a constant color and luster of the appearance, and since the tinplate is stretched and deformed during the processing of the top cover, the surface is likely to become black. Therefore, it is necessary to develop a tinplate that meets the requirements for press formability, pressure resistance and surface gloss of the top cover of an aerosol can.

[0004] According to the requirements for press formability and pressure resistance of the top cover of an aerosol can, the conventional tinplate for the top cover of an aerosol can mainly adopts the following two kinds of composition design. (1) Low carbon aluminum killed steel is used and a batch annealing process is adopted. The annealing time is long, carbon and nitrogen atoms are sufficiently precipitated, and good aging resistance is obtained, which results in good press formability. (2) Interstitial free steel (i.e. IF steel) is adopted to form an interstitial free ferrite structure. It has good aging resistance, and alloy elements such as Mn, Ti and B are added to improve the hardness of the steel sheet by solid solution strengthening and precipitation strengthening to meet the pressure resistance requirements. According to the requirements for the surface gloss of the top cover of an aerosol can, the conventional technology increases the amount of tin plating to maintain the surface gloss of the cover after pressing.

[0005] For example, the prior art discloses anti-aging tinplate, which adopts a composition design of low carbon aluminum killed steel with C 0.02-0.06% and Al 0.005-0.040% and is produced by a batch annealing process, and can meet the formability requirements for top cover processing. However, the hardness range of the product is 55±4, which is too low and can only be used for ordinary low pressure cans and cannot meet the high pressure requirements for top covers of medium pressure cans and high pressure cans. In addition, the temperature inside the batch annealed steel coil is not uniform, so the hardness of the head, middle and tail parts of the steel coil changes greatly, which is disadvantageous for a production line that manufactures covers at high speed.

[0006] The prior art also discloses tinplate for the top cover of an aerosol can and its manufacturing method, which adopts a composition design of interstitial-free steel (i.e., IF steel) with 0.0015-0.0030% C, 0.50-0.60% Mn, 0.045-0.065% Ti, and 0.0002-0.0006% B, which has excellent aging resistance and low press crack rate, but requires the C content to be controlled to 15-30 ppm, which increases the difficulty of steelmaking production, and also increases the smelting cost due to the addition of a large amount of alloy elements such as Mn, Ti, and B. In addition, the temperature of the hot rolling and annealing process is high, the power consumption of the process is large, and the oxide scale becomes thick during the hot rolling process and is difficult to remove, which is likely to cause surface quality problems in the subsequent process, and the difficulty of production control is high. Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, the technical problem to be solved by the present application is to provide a tinplate and a manufacturing method thereof by solving the above-mentioned defects existing in the tinplate in the prior art. [Means for solving the problem]

[0008] Therefore, the present application provides the following technical solutions:

[0009] The present application includes the steps of steel making and continuous casting, hot rolling, pickling and cold rolling, continuous annealing and flattening, and tin plating, In the process of steelmaking and continuous casting, the mass percentage of the chemical components of the slab is controlled as follows: C0.020~0.040%, Mn0.15~0.25%, Si≦0.03%, P≦0.015%, S≦0.010%, Al0.03~0.06%, N≦0.0030%, and the balance is Fe and other unavoidable impurities. The mass contents of Al and N elements satisfy the relationship formula Al≧0.02%+11.57N; In the process of hot rolling, the slab heating temperature is controlled at 1180-1220℃, the intermediate slab thickness is controlled at 40-42mm, the final rolling temperature is controlled at 860-890℃, and the coiling temperature is controlled at 640-670℃. In the process of continuous annealing and flattening, the strip temperature in the quenching section is controlled at 360-380°C, and the cooling rate is controlled at 100-130°C / s. The strip after cooling enters the aging section. In the aging section 1 region, the strip temperature is 400-420°C, and the aging time is 60-80s. In the aging section 2 region, the strip temperature range is 320-420°C, and the aging time is 120-140s. The flattening is performed by using a double frame flattening machine. The flattening rolling force of the frame 1 is 4000-4500kN, the flattening rolling force of the frame 2 is 3000-3500kN, the strip tension is 40-60kN, and the flattening elongation is 1.4-1.6%.

[0010] Alternatively, in the tin plating process, the single-sided tin plating amount is 2.7~2.9g / m 2 The strip speed is controlled to 320-380 m / min, the reflow temperature to 260-263°C, and the height from the reflow device to the water quenching tank to 4.2-4.6 m.

[0011] Optionally, the steelmaking and continuous casting includes smelting molten steel in a converter, followed by RH refining and continuous casting of slabs.

[0012] Optionally, the hot rolling includes rough rolling, finish rolling, laminar cooling, and coiling to obtain hot rolled steel coils.

[0013] Optionally, the hot rolled steel coil has a thickness of 2.5 to 3.0 mm.

[0014] Optionally, the pickling and cold rolling includes unwinding, pickling, trimming, cold rolling, and coiling the hot rolled steel coil to obtain a cold coil; In the process of pickling and cold rolling, the thickness of the cold coil is controlled to be 0.30-0.45 mm, and the cold rolling reduction is controlled to be 85-88%.

[0015] Optionally, the continuous annealing and flattening includes uncoiling, degreasing, cleaning, continuous annealing, flattening, trimming and coiling the cold coil to obtain an annealed steel coil.

[0016] Optionally, during the continuous annealing process, the strip speed is controlled at 400-450m / min, and the strip temperature in the soaking section is controlled at 740-760℃; The planarization is a dry planarization.

[0017] Optionally, the tin plating includes unwinding, degreasing, pickling, electroplating, reflowing, passivating, oiling, and winding the annealed steel coil to obtain a tin-plated steel coil; The reflow is an induction reflow, which has the advantages of increasing the temperature rapidly and keeping the energy consumption of the alloy layer low.

[0018] The present application provides a tinplate produced by the above-mentioned production method.

[0019] Optionally, the tinplate has a thickness of 0.30 to 0.45 mm, a hardness (HR30T) of 58±2, a yield strength of 300 to 350 MPa, a tensile strength of 360 to 400 MPa, an elongation after break of 33 to 38%, and a yield elongation of ≦3%, the microstructure of the tinplate is equiaxed ferrite + cementite particles, the grain size of the ferrite is 10 to 11 grade, and the cementite is uniformly dispersed and distributed. The amount of tin plating on one side of the tinplate is 2.7 to 2.9 g / m 2 where the tin content of the alloy is 0.4-0.6 g / m 2 It is.

[0020] Functions of the main components designed in this application and their selective description C: C is the most economical strengthening element in steel, and maintaining a constant C content during steelmaking is advantageous for achieving the strength and hardness of the material at low cost. With the increase in C content, the hardness of the material increases, and if the C content is too high, the hardness of the tinplate is too high, which is likely to cause the elongation rate to decrease, reducing the press formability and aging resistance of the tinplate. In addition, the control range of the C content affects the change in material hardness, but if the control range is too narrow, the steelmaking cost will increase significantly. Therefore, in this application, the C content is set to 0.02-0.04%. Mn: Mn is a solid solution strengthening element that can improve the strength of steel plate without obviously reducing plasticity, and when Mn combines with S to form MnS, it reduces the hot brittleness of steel. However, if the Mn content is too high, it increases the cost of the alloy. Therefore, in this application, the Mn content is set to 0.15-0.25%. Si: Si is easily oxidized when it is enriched on the surface of the steel, which is detrimental to the surface quality and coatability of the steel sheet. Therefore, the lower the Si content, the better. In the present application, Si≦0.03%. P: P has a strong solid solution strengthening effect, but is prone to segregation to form band-like structures, which reduces the plasticity and toughness of the steel sheet and is detrimental to formability. In the present application, P≦0.015%. S: In tinplate, S is a harmful impurity element that easily forms sulfide inclusions and is disadvantageous in forming the steel sheet. In the present application, S is set to ≦0.010%. N: In tinplate, N is a harmful impurity element. When N atoms are dissolved in gaps, the strength and hardness of the steel sheet are improved, the plasticity is reduced, and stretcher strain marks are likely to occur during press deformation of the steel sheet. Therefore, it is necessary to reduce the N content in the steel, and in this application, N≦0.0030%. Al: Al is added in the steelmaking process as a deoxidizer, and Al can combine with N to form AlN. Since N in steel cannot be completely removed, a certain amount of Al is added to fix N in steel and improve aging resistance. If Al, which acts to fix nitrogen, is maintained at a certain excess ratio, it is favorable for N in low carbon steel to be sufficiently fixed, that is, (Al-0.02%) / 27≧6×(N / 14). However, if the Al content is too high, the amount of inclusions in steelmaking increases, the pourability of continuous casting becomes poor, and the cost of the alloy increases. Therefore, in the present application, the range of the Al content is set to 0.03-0.06%, and the relationship formula Al≧0.02%+11.57N is satisfied.

[0021] The method for producing tinplate described in the present application achieves both press formability and pressure resistance of tinplate, which are necessary for the top cover of an aerosol can, and economical production. Important steps of each process in the production method described in the present application will be described. Steelmaking: Through RH vacuum degassing treatment, the C content can be accurately controlled within the range of 0.02-0.04%, and the solid solution strengthening effect of C can be fully utilized to achieve the desired tinplate hardness. The RH process can also effectively remove N and reduce the N content in the steel, which is favorable for press formability, and also reduces the Al content required to fix N. Hot rolling: Through the austenitic rolling process, the heating temperature and rolling temperature of the slab are controlled low, and the thickness of the intermediate slab is properly controlled, thereby avoiding problems such as high energy consumption, poor surface quality, and coarse grains caused by high temperature rolling. If the heating temperature of the slab is too high, a large amount of AlN will be dissolved in the heating process, and the solid solution nitrogen content will increase, and a higher aluminum content and a longer high temperature coiling time will be required to fully precipitate AlN; on the other hand, if the temperature is too low, it will be difficult to roll and the final rolling temperature will be easy to be low, so the heating temperature of the slab is controlled at 1180-1220°C. If the thickness of the intermediate slab is too small, the temperature will drop significantly in the rolling process, and the final rolling temperature cannot be guaranteed, and the temperature uniformity of the steel coil will be poor; if the thickness of the intermediate slab is too large, it will be more difficult to roll. Therefore, the thickness of the intermediate slab is set to 40-42mm. By adopting a low final rolling temperature while ensuring that the temperature is higher than the Ar3 transformation point, two-phase rolling is avoided, and the final rolling temperature is set to 860 to 890°C. If the coiling temperature is too high, coarse crystal grains are likely to be formed and strength is reduced, while if the temperature is too low, it is unfavorable for precipitation of solute N, so the coiling temperature is set to 640 to 670°C. Cold rolling: If the cold rolling reduction is too large, the recrystallization temperature will be high, and a higher annealing temperature will be required. In addition, the grain size of the steel plate will be small after annealing, the hardness will be large, and the yield platform will be extended, which is unfavorable to the uniform deformation in the pressing process. If the cold rolling reduction is too small, the grain size of the steel plate will be coarse, the hardness will be low, and thinner hot rolling raw materials will be required, which will increase the production cost. Therefore, the cold rolling reduction is set to 85-88%. Continuous annealing: Continuous annealing is a crucial process for controlling the structure and properties of steel sheets. It involves heating the steel sheet above the recrystallization temperature and carrying out the processes of recovery, recrystallization, grain growth and cementite precipitation. First, the strip speed and the temperature of the soaking section are combined to obtain a ferrite structure with a certain grain size. Rapid cooling (100-130°C / s) is also used to supersaturate the solute C atoms in the ferrite and obtain sufficient precipitation storage energy. In the first aging, an overaging process is adopted, in which the strip is reheated after quenching to the aging temperature (400-420°C) and kept at room temperature for a certain period of time, which promotes the rapid and large precipitation of cementite; the second aging is gradient aging, which makes full use of the strip temperature (320-420°C) and prolongs the keeping time, which further precipitates cementite and reduces the adverse effect on press deformation caused by the solubilization of C atoms in the gaps. Therefore, according to the composition, hot rolling and cold rolling process of the steel plate of the present application, a reasonable annealing process is used, that is, the strip speed is 400-450m / min, in the soaking section, the temperature is 740-760℃, in the quenching section, the temperature is 360-380℃, the cooling rate is 100-130℃ / s, in the aging section 1 region, the strip temperature is 400-420℃, the aging time is 60-80s, and in the aging section 2 region, the strip temperature range is 320-420℃, and the aging time is 120-140s. Flattening: The flattening action includes adjusting the mechanical properties of the steel plate after annealing, imparting various surface structures and roughness to the strip, and improving the shape and quality. Adopting the mode of large rolling force and small tension is favorable to obtaining more mobile dislocations and reducing the yield elongation rate, but the rolling force is too large and the tension is too small, which is unfavorable to the control of the shape and surface structure of the strip. Therefore, the rolling forces of the two flattening frames are 4000-4500kN and 3000-3500kN respectively, and the strip tension is 40-60kN. For low carbon aluminum killed steel, as the flattening elongation rate increases, the yield strength of the steel plate decreases and then increases, and when the flattening elongation rate reaches 1.2% or more, the yield platform of the annealed steel plate with a thickness of 0.30-0.45mm can be eliminated. When the yield strength reaches the lowest point, the flattening elongation can be continued to be improved to 1.4% or more, so as to achieve more mobile dislocations and properly improve the yield strength and hardness of the steel plate; however, if the flattening elongation is too high, it will significantly improve the hardness, reduce the plasticity, and also increase the load of the flattening machine, so the flattening elongation should not exceed 1.6%. Reflow: The tinplate is rapidly heated to a temperature above the melting point of tin (232℃) by the reflow equipment, which melts the tin plating layer to smooth the surface and forms a tin-iron alloy layer, thereby improving the adhesion and corrosion resistance of the tin layer. If the reflow temperature is too low, the tin layer will not reflow sufficiently, and if the reflow temperature is too high, the alloy layer will be thick and the oxidation of the tin layer will be serious. Therefore, the reflow temperature is set to 260-263℃, and the reflow equipment is adjusted so that the height of the water quenching tank is 4.2-4.6m, and the reflow reaction time is controlled, thereby reducing the thickness of the tin-iron alloy layer, keeping the amount of tin plating constant, and reserving more of the pure tin layer, which is more shiny, thereby improving the surface gloss of the cover produced by pressing the tinplate and avoiding the problem of darkening. Effect of the Invention

[0022] The technical solution of the present application has the following advantages:

[0023] The tinplate manufacturing method of the present application adopts the composition design of low carbon aluminum-killed steel, designs the content of elements such as C, Mn, Al and N in the tinplate without increasing the alloy content and the difficulty of production control, combines the corresponding processes of hot rolling, cold rolling, annealing and flattening, fully utilizes the strengthening effects of traditional elements such as carbon and manganese, combines the control of aluminum nitride precipitation in hot rolling and annealing, selects a suitable cold rolling reduction, controls the ferrite grain size and cementite precipitation in the steel by continuous annealing and overaging treatment, and combines with a specific flattening process to produce tinplate with small change in strength and hardness, high elongation and short yield platform, and meets the requirements for press formability and pressure resistance of the top cover of an aerosol can. The composition of the tinplate is simple, the process is simple and easy to implement, and the production cost is low. Specifically, the present application adopts a design combining steelmaking ingredients with the processes of hot rolling, annealing and flattening, thereby controlling the precipitation of aluminum nitride and cementite, maximizing the reduction of C and N atoms dissolved in the gaps in the steel, effectively shortening the yield platform, and favoring press formability. In the hot rolling of the present application, the rolling temperature is controlled low and the thickness of the intermediate slab is properly controlled, thereby avoiding problems such as high energy consumption, poor surface quality and coarse grains caused by high temperature rolling, improving the surface quality and uniformity of the structure of the product, and further reducing production costs.

[0024] The manufacturing method of the tinplate of the present invention adopts induction reflow to control the reflow temperature and reaction time, and also rationally controls the amount of tin in the alloy, thereby achieving the effect of accurately controlling the tin layer of the alloy. The amount of tin in the tinplate alloy is 0.4-0.6g / m 2 This is advantageous for maintaining the gloss of the tinplate surface after press deformation.

[0025] The tinplate according to the present application has a hardness (HR30T) of 58±2, a yield strength of 300-350 MPa, a tensile strength of 360-400 MPa, an elongation after fracture of 33-38%, and a yield elongation of 3% or less, among which the hardness and strength of the steel sheet can meet the requirements for pressure resistance of the top cover of an aerosol can, and the range of change in hardness and strength is small, the elongation is high, and the yield platform is short, so that no ridging occurs during pressing of the top cover of an aerosol can, and the microstructure of the steel sheet is equiaxed ferrite + cementite particles, the cementite is uniformly dispersed and distributed, and there is no band-like cementite, so that cracks caused by inconsistent local deformation are avoided and the uniformity of processing deformation is improved. By controlling the mechanical properties such as hardness, strength, elongation, and yield elongation of tinplate, as well as its microstructure, the difficult problem of achieving both press formability and pressure resistance in conventional low-carbon aluminum-killed steel is effectively solved, and the requirements for use as aerosol can top covers are met.

[0026] In order to more clearly describe the specific embodiments of the present application or the technical solutions in the prior art, the following briefly introduces drawings that need to be used in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can further obtain other drawings based on these drawings without any creative work. [Brief description of the drawings]

[0027] [Figure 1] 1 is a photograph of the microstructure of the tinplate obtained in Example 1 of the present application. [Diagram 2] 1 is a photograph of the microstructure of the tinplate obtained in Comparative Example 1 of the present application. [Diagram 3] 3 is a curve of the annealing process of an embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The following examples are provided for a better understanding of the present application, but are not limited to the best embodiment, and are not intended to limit the content and scope of protection of the present application. Any products identical or similar to those of the present application that someone obtains by combining the teachings of the present application or the features of the present application with other prior art are within the scope of protection of the present application.

[0029] In the examples, unless specific experimental steps or conditions are specified, the procedures or conditions of conventional experimental steps described in the literature in the field may be followed. Unless the manufacturers are specified, the reagents or equipment used are all ordinary reagent products available from commercial sources.

[0030] The manufacturing methods of tinplate according to the examples and comparative examples of the present application include the steps of steelmaking and continuous casting, hot rolling, pickling, cold rolling, continuous annealing and flattening, and tin plating, and specifically, the steps are as follows:

[0031] 1) Steelmaking and continuous casting: Molten steel is smelted in a converter, refined by RH, and then cast into slabs. The chemical composition of the slabs is shown in Table 1.

[0032] [Table 1]

[0033] 2) Hot rolling: The continuous casting slab is heated, rough rolled, finish rolled, laminar cooled, and coiled in sequence to obtain hot rolled steel coils with a thickness of 2.5 to 3.0 mm. Specifically, the parameters of the hot rolling process are shown in Table 2.

[0034] [Table 2]

[0035] 3) Pickling and cold rolling: The hot-rolled steel coil is unwound, pickled, trimmed, continuously cold-rolled, and wound in sequence to obtain a cold coil with a thickness of 0.30 to 0.45 mm. Specifically, the parameters of the hot-rolling process are shown in Table 3.

[0036] [Table 3]

[0037] 4) Continuous annealing and flattening: The cold coil is unwound, degreased, washed, annealed, flattened, trimmed, and coiled to obtain an annealed steel coil. The annealing process curve of the embodiment of the present application is shown in Figure 3, and the specific process parameters are shown in Tables 4 and 5.

[0038] [Table 4]

[0039] [Table 5]

[0040] 5) Tin plating: The annealed steel coil is unwound, degreased, pickled, electroplated, reflowed, passivated, oiled, and wound to obtain tin-plated steel coil (tinplate). Specifically, the process parameters are shown in Table 6.

[0041] [Table 6]

[0042] In this comparative example, except for the chemical composition of the slab, the other process operation steps and parameters are the same as those in Example 1, and the specific composition of the slab is shown in the table below.

[0043] [Table 7]

[0044] Comparative Example 5 In this comparative example, only the operation parameters of the continuous annealing are different from those in Example 1, and the specifics are shown in the table below.

[0045] [Table 8]

[0046] In this comparative example, only the operation parameters of the continuous hot rolling are different from those in Example 1, and the specifics are shown in the table below.

[0047] [Table 9]

[0048] In this comparative example, only the flattening operation parameters are different from those in Example 1, and are specifically shown in the table below.

[0049] [Table 10]

[0050] The mechanical properties, structure and tin plating amount of the tin-plated steel coils manufactured based on the above examples and comparative examples were detected. The specific test methods refer to GB / T2520-2017 "Cold-rolled tin-plated steel sheet and strip" and GB / T4335-2013 "Determination method for ferrite grain size of low-carbon cold-rolled steel sheet". The test results are shown in Table 11.

[0051] [Table 11]

[0052] The results of the formability, pressure resistance test and appearance inspection of the covers manufactured by applying the tin-plated steel coils according to the examples and comparative examples of the present application to a production line for top covers of aerosol cans are shown in Table 12. The test method for pressure resistance was performed in accordance with GB / T13042-2008 "Packaging containers - Iron aerosol cans."

[0053] In the examples of the present application, the covers produced are well molded, have no cracks or ridging, and all of the pressure resistance values ​​reach 1.8 MPa or more, which can meet the requirements for high-pressure aerosol can products, and the surface gloss of the covers is good. On the other hand, in Comparative Examples 1 and 3, the pressure resistance values ​​pass, but the covers produced have problems with cracks and ridging during molding, in Comparative Example 2, the covers are well molded, but the pressure resistance is insufficient and cannot be used for high-pressure aerosol cans, and in Comparative Examples 1 to 3, the surfaces of the covers produced appear dark. In Comparative Examples 4 to 7, the pressure resistance values ​​pass, but the covers produced have problems with cracks and ridging during molding.

[0054] [Table 12]

[0055] Fig. 1 is a photograph of the microstructure of the tinplate according to Example 1 of the present application, and as can be seen from the figure, the microstructure is equiaxed ferrite + cementite particles, where the ferrite grains are equiaxed and uniform in size, the grain size is 11, the cementite is uniformly dispersed and distributed, the number is small, and the overall structure is uniform. Fig. 2 is a photograph of the microstructure of the tinplate according to Comparative Example 1 of the present application, and as can be seen from the figure, the microstructure is equiaxed ferrite + cementite particles, where the ferrite grains are fine, the grain size is 11.5, the cementite is large in size, numerous, band-like or cluster-like, and non-uniformly distributed, and the overall structure is non-uniform, which is prone to non-uniform deformation and causes ridging and cracks in the manufacture of the cover.

[0056] Obviously, the above examples are merely illustrative and are not intended to limit the embodiments. Those skilled in the art can make various other changes or modifications based on the above description. It is not necessary and impossible to list all the embodiments here. Any obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for producing tinplate, comprising the steps of: The process includes the steps of steelmaking and continuous casting, hot rolling, pickling and cold rolling, continuous annealing and flattening, and tin plating. In the process of steelmaking and continuous casting, the mass percentages of the chemical components of the slab are controlled as follows: C: 0.020-0.040%, Mn: 0.15-0.25%, Si≦0.03%, P≦0.015%, S≦0.010%, Al: 0.03-0.06%, N≦0.0030%, the balance being Fe and other unavoidable impurities, and the mass contents of Al and N elements satisfy the relationship formula Al≧0.02%+11.57N; In the hot rolling process, the slab heating temperature is controlled at 1180-1220°C, the intermediate slab thickness is controlled at 40-42mm, the final rolling temperature is controlled at 860-890°C, and the coiling temperature is controlled at 640-670°C. the strip temperature is 740-760°C in the soaking section, and the strip temperature is 360-380°C in the quenching section, and the cooling rate is 100-130°C / s; the cooled strip enters the aging section; in the aging section 1 region, the strip temperature is 400-420°C, and the aging time is 60-80s; in the aging section 2 region, the strip temperature range is 320-420°C, and the aging time is 120-140s; the flattening is performed by using a double frame flattening machine, the flattening rolling force of frame 1 is 4000-4500kN, the flattening rolling force of frame 2 is 3000-3500kN, the strip tension is 40-60kN, and the flattening elongation is 1.4-1.6%.

2. In the tin plating process, the amount of tin plated on one side is 2.7 to 2.9 g / m 2 The method for producing tinplate according to claim 1, characterized in that the stripping speed is controlled to 320-380 m / min, the reflow temperature is controlled to 260-263°C, and the height from the reflow device to the water quenching tank is controlled to 4.2-4.6 m.

3. The method for producing tinplate according to claim 1 or 2, characterized in that the steelmaking and continuous casting include smelting molten steel in a converter, performing RH refining, and then continuously casting a slab.

4. The method for producing tinplate according to claim 1 or 2, characterized in that the hot rolling includes rough rolling, finish rolling, laminar cooling, and coiling to obtain a hot rolled steel coil.

5. The method for producing tinplate according to claim 4, characterized in that the hot rolled steel coil has a thickness of 2.5-3.0 mm.

6. The pickling and cold rolling includes unwinding, pickling, trimming, cold rolling, and coiling the hot rolled steel coil to obtain a cold coil; The method for producing tinplate according to claim 1 or 2, characterized in that in the process of pickling and cold rolling, the thickness of the cold coil is controlled to 0.30-0.45 mm, and the cold rolling reduction is controlled to 85-88%.

7. The method for producing tinplate according to claim 1 or 2, characterized in that the continuous annealing and flattening includes unwinding, degreasing, cleaning, continuous annealing, flattening, trimming, and coiling the cold coil to obtain an annealed steel coil.

8. The method for producing tinplate according to claim 7, characterized in that the flattening is a dry flattening.

9. The tin plating includes unwinding, degreasing, pickling, electroplating, reflow, passivation, oiling, and winding the annealed steel coil to obtain a tin-plated steel coil; The method for producing tinplate according to claim 1 or 2, characterized in that the reflow is an induction reflow.

10. The method for producing tinplate according to any one of claims 1 to 9, characterized in that the tinplate has a thickness of 0.30 to 0.45 mm, a hardness HR30T of 58±2, a yield strength of 300 to 350 MPa, a tensile strength of 360 to 400 MPa, an elongation after fracture of 33 to 38%, and a yield elongation of ≦3%, the microstructure of the tinplate is equiaxed ferrite + cementite particles, the grain size of the ferrite is 10 to 11 grades, and the cementite is uniformly dispersed and distributed.

11. A tinplate produced by the method according to any one of claims 1 to 10.

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