A steel material and a method for producing the same, a steel for packaging, a metal can

Abstract

The application provides a kind of steel and its preparation method, steel for packaging, metal can, belongs to the field of steel preparation.The chemical composition of the steel includes: C, Si, Mn, Alt, P, S, N and Fe;Among them, the content of C is 0.12%~0.15% by mass fraction, the content of Si is ≤0.03%, the content of Mn is 0.50%~0.80%, the content of Alt is 0.030%~0.060%, the content of P is <0.012%, the content of S is <0.010%, the content of N is ≤0.003%;The microstructure of the steel includes: ferrite, pearlite and tertiary cementite;The content of ferrite is 80%~88% by volume fraction, the content of pearlite is 10%~15%, and the content of tertiary cementite is 2%~5%.Low-carbon component design is adopted, without adding other alloy elements, refined ferrite grains and small interlamellar spacing pearlite structure are obtained to realize high strength and high plasticity of the material, the strength of the material is significantly improved, and the forming property of the material is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel production, and particularly relates to a steel and a preparation method thereof, a packaging steel and a metal can. BACKGROUND

[0002] The packaging steel is a cold-rolled low-carbon steel plate or strip plated with tin or chromium on both sides through electroplating. With the continuous thinning of the can wall, users have put forward higher requirements for the comprehensive performance of the packaging steel.

[0003] The packaging steel mainly realizes the thinning of the material thickness and the improvement of the strength through the secondary cold rolling process after annealing, but the secondary cold rolling will also cause the decrease of the elongation after fracture and the increase of the planar anisotropy of the material, that is, the ductility and uniformity of the material are significantly reduced. From the actual application, there are two problems in the process of processing the metal can, one is the stamping cracking caused by the low elongation, especially the transverse cracking caused by the low elongation in the TD direction of the material; the other is the flange edge folding and earing defects in the forming process caused by the large planar anisotropy.

[0004] To continuously improve the ductility and uniformity of steel for packaging and optimize its forming performance, advanced steel plants at home and abroad have made a lot of beneficial explorations around the composition, annealing and secondary cold rolling process of the material. Patent CN110462089A discloses a steel plate and its manufacturing method, as well as a bottle cap and a DRD can, the composition of which is (mass percent): 0.006% < C < 0.010%, Si < 0.05%, 0.05% < Mn < 0.60%, S < 0.05%, P < 0.05%, 0.02% < Al < 0.05%, Cr < 0.04%, 0.014% < N < 0.018%, bloom soaking temperature > 1200℃, FDT > 870℃, 550℃ < CT < 750℃, cold rolling reduction > 88%, continuous annealing soaking temperature 660-760℃, soaking time > 60s, after soaking, cooling to 300-450℃ temperature range at a cooling rate > 10℃ / s, then cooling to < 140℃ temperature range at a cooling rate of 5-30℃ / s, secondary cold rolling reduction 10% < DCR < 40%, preferably 15% < DCR < 35%, finished product thickness < 0.20mm, yield strength 620-700MPa. This patent uses a high-nitrogen composition system, which needs to blow nitrogen (N2) into the molten steel in the steelmaking process and add manganese nitride (MnN) alloy to achieve nitrogen enrichment, which has a high smelting cost. In addition, the preferred secondary cold rolling reduction of this patent is 15% < DCR < 35%, which often leads to a significant decrease in material elongation after fracture, especially in the TD direction, which is not conducive to the improvement of material forming performance. Patent CN106086643A discloses a high-strength high-elongation tin-plated raw plate and its secondary cold rolling method, the composition of which is (mass percent): 0.065% < C < 0.12%, 0.2 < Mn < 0.8%, 0.01 < Alt < 0.08%, 0.003 < N < 0.015%, 0.001% < B < 0.005%, 0.01 < Cr < 0.05%, 0.001 < Ti < 0.1%, 0.001 < Nb < 0.2%, 0.01 < Cu < 0.03%, 0.002% < Mo < 0.008%, primary cold rolling reduction 85%~90%, annealing soaking temperature 620~680℃, secondary cold rolling reduction 5~13%, yield strength Rp 0.2 ≥520MPa, RD, 45°, TD direction elongation ≥10%. The yield strength Rp 0.2The control is about 520 MPa, the actual thickness is greater than 0.22 mm, the strength level and the thickness specification limit the application range, and in addition, the patent adds some alloy elements, which is not conducive to the continuous reduction of product cost. The patent CN114058946A discloses a low anisotropy high strength high elongation steel base and tin-plated sheet and a preparation method thereof, and the composition is (mass percent): C: 0.06% to 0.08%, Si≤0.02%, Mn: 0.35% to 0.6%, P≤0.015%, S≤0.012%, Als: 0.005% to 0.02%, N: 0.006% to 0.010%, and the rest is Fe and impurities. Ferrite: the key process parameters include annealing soaking temperature 640°C to 660°C, fast cooling section cooling rate 50°C / s to 90°C / s, fast cooling final cooling temperature≤250°C, primary cold rolling reduction≥87%, and flattening elongation 2% to 3%. The patent uses flattening with small reduction after annealing to replace secondary cold rolling, and the elongation of the finished product and the anisotropy are greatly improved, but from the patent examples, the actual strength level of the product is about 460 MPa, and the application range is relatively limited.

[0005] Therefore, it is urgent to develop a kind of steel that can meet the technical requirements of the metal can for the thickness reduction, strength improvement and forming property optimization of the packaging steel, and effectively improve the cracking, edge wrinkle and ear defects of the packaging steel in the metal can processing process. SUMMARY

[0006] The present application provides a kind of steel and its preparation method, packaging steel, metal can, to meet the technical requirements of the metal can for the thickness reduction, strength improvement and forming property optimization of the packaging steel, effectively improve the cracking, edge wrinkle and ear defects of the packaging steel in the metal can processing process.

[0007] In a first aspect, the present application provides a kind of steel, the chemical composition of the steel includes: C, Si, Mn, Alt, P, S, N and Fe;Wherein, in mass fraction,

[0008] The content of C is 0.12% to 0.15%, the content of Si is less than or equal to 0.03%, the content of Mn is 0.50% to 0.80%, the content of Alt is 0.030% to 0.060%, the content of P is less than 0.012%, the content of S is less than 0.010%, and the content of N is less than or equal to 0.003%;

[0009] The microstructure of the steel includes ferrite, pearlite and tertiary cementite, and the volume fraction is

[0010] The content of the ferrite is 80% to 88%, the content of the pearlite is 10% to 15%, and the content of the tertiary cementite is 2% to 5%.

[0011] Optionally, the ferrite grain size is 11.5-12.5, and the pearlite interlamellar spacing is 120-150 nm.

[0012] Optionally, the ferrite grain is equiaxial polygonal, the pearlite is island-shaped distributed at the ferrite grain boundary position, and the tertiary cementite is granularly dispersedly distributed in the ferrite grain.

[0013] In a second aspect, the application provides a preparation method of the steel material in any one of the first aspect, the method comprising:

[0014] obtaining a casting blank;

[0015] sequentially heating, hot rolling, coiling, pickling, cold rolling, continuous annealing and secondary cold rolling the casting blank to obtain the steel material.

[0016] Optionally, the continuous annealing comprises a preheating section, a heating section, a soaking section and a rapid cooling section, the outlet temperature of the preheating section is 150-180℃, the heating speed of the heating section is 20-30℃ / s, the outlet temperature of the heating section is 730-750℃, the soaking temperature of the soaking section is 730-750℃, the soaking time of the soaking section is 50-80 s, and the cooling speed of the rapid cooling section is 40-60℃ / s, and the final cooling temperature of the rapid cooling section is 200-250℃.

[0017] Optionally, the cold rolling reduction is 85-90%, and the secondary cold rolling reduction is 8-12%.

[0018] Optionally, the heating temperature is 1180-1220℃, the final rolling temperature is 850-890℃, and the coiling temperature is 600-640℃.

[0019] In a third aspect, the application provides a packaging steel, comprising a steel material substrate and a functional layer attached to at least part of the surface of the steel material substrate.

[0020] The steel material substrate is the steel material in any one of the embodiments of the first aspect.

[0021] The functional layer comprises at least one of a tin plating layer and a chromium plating layer.

[0022] Optionally, the packaging steel satisfies at least one of the following properties: thickness ≤0.18 mm, tempering degree DR-9, hardness HR30T 71-81, yield strength Rp 0.2 ≥620 MPa, earing rate <5%, and RD, 45° and TD direction elongation >5%.

[0023] In a fourth aspect, the present application provides a metal can comprising a metal structural component made of the packaging steel according to any one of the third aspect, wherein the metal structural component comprises at least one of a can lid, a can body and a can bottom.

[0024] Compared with the prior art, the above technical solution provided by the embodiments of the present application has the following advantages:

[0025] By adopting the low-carbon composition design, without adding other alloy elements, and obtaining refined ferrite grains and fine pearlite interlamellar spacing to realize high strength and high plasticity of the material, the material strength is significantly improved, and the material forming performance is improved. The thickness of the packaging steel obtained by the present application is ≤0.18mm, the tempering degree reaches DR-9 level, the hardness HR30T is 71-81, the yield strength Rp 0.2 ≥620MPa, the RD, 45°, TD three-way elongation, especially the TD direction elongation is >5%, and the earing rate is <5%. BRIEF DESCRIPTION OF DRAWINGS

[0026] The drawings incorporated into the specification and forming a part thereof, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0028] Figure 1 A flowchart of a steel preparation method provided by the embodiments of the present application is shown in the figure.

[0029] Figure 2 A metallographic structure diagram of the steel provided by the embodiment 1 of the present application is shown in the figure.

[0030] Figure 3 A transmission electron microscope morphology diagram of the pearlite structure of the steel provided by the embodiment 1 of the present application is shown in the figure. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0032] Various embodiments of the present application can exist in a range of forms; it should be understood that the description in a range form is merely for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the range described has been specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has been specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in the present description, it refers to any cited number (fraction or integer) within the indicated range.

[0033] In addition, in the description of the present application, the terms "include", "contain" and the like mean "include but not limited to". In the present text, relational terms such as "first" and "second" and the like are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. In the present text, "and / or" describes the association between the associated objects, which means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. Where A and B can be singular or plural. In the present text, "one or more" means one or more, and "multiple" means two or more. "At least one", "at least one of the following" or the like means any combination of the items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0034] Unless otherwise specifically stated, the various raw materials, reagents, instruments and equipment used in the present application can be purchased on the market or can be prepared by existing methods.

[0035] In a first aspect, the present application provides a steel material, the chemical composition of the steel material comprising: C, Si, Mn, Alt, P, S, N and Fe; wherein, in terms of mass fraction,

[0036] The content of C is 0.12% to 0.15%, the content of Si is ≤0.03%, the content of Mn is 0.50% to 0.80%, the content of Alt is 0.030% to 0.060%, the content of P is <0.012%, the content of S is <0.010%, and the content of N is ≤0.003%;

[0037] The microstructure of the steel material comprises ferrite, pearlite and tertiary cementite, and the volume fraction of the ferrite is 80-88%, the volume fraction of the pearlite is 10-15%, and the volume fraction of the tertiary cementite is 2-5%.

[0038] The content of the ferrite is 80-88%, the content of the pearlite is 10-15%, and the content of the tertiary cementite is 2-5%.

[0039] The effects and the limited ranges of the above-mentioned main alloying elements are as follows:

[0040] The positive effect of controlling the content of C to be 0.12-0.15%: C is the most economical and effective strengthening element in steel, and plays an important role in strengthening in the present application. When the content of C is lower than 0.12% in the present application, sufficient pearlite structure cannot be formed in the cooling process after annealing soaking. When the content of C is higher than 0.15%, the element diffusion is accelerated in the annealing soaking and cooling process, the content of pearlite is increased, and the lamellar spacing of the structure is significantly increased. The roughening of the structure leads to a significant decrease in the plasticity of the material. The content of C can be 0.12%, 0.13%, 0.14%, 0.15%, etc.

[0041] The positive effect of controlling the content of Si to be ≤0.03%: the higher the content of Si, the higher the enrichment degree of SiO2 on the surface of the strip steel, and the worse the adhesion between the plated layer and the strip steel substrate after cold rolling and electroplating, and the worse the corrosion resistance of the plated layer. The content of Si is limited to ≤0.03% in the present application to ensure the corrosion resistance of the material. The content of Si can be 0.01%, 0.015%, 0.02%, 0.03%, etc.

[0042] The positive effect of controlling the content of Mn to be 0.50-0.80%: Mn is also an important strengthening element in the present application, and the strength of the steel is further improved by the solid solution strengthening of Mn. Mn belongs to the elements that expand the austenite phase region, and can promote the transformation of austenite in the low-temperature soaking process in the α+γ two-phase region, thereby ensuring the full transformation of the pearlite type in the subsequent cooling process. When the content of Mn is lower than 0.6% in the present application, the strength requirement of the material cannot be guaranteed. When the content of Mn is higher than 0.8%, Mn segregation is easily formed in the continuous casting billet, and banded structure is easily formed in the hot-rolled strip steel, and the stamping forming performance of the cold-rolled product is deteriorated accordingly. The content of Mn can be 0.50%, 0.60%, 0.70%, 0.80%, etc.

[0043] The content of Alt is controlled to be 0.030%-0.060%, and the positive effect is that Al is an indispensable deoxidizer for steelmaking, and when the content of Al is lower than 0.025%, the technical requirement of complete deoxidization of molten steel cannot be met, and when the content of Al is too high, the number of Al2O3 inclusions in the steel increases, and the size of the inclusions becomes large, which is not conducive to stamping forming. The content of Alt is limited to the range of 0.03-0.06%. The content of Alt can be 0.030%, 0.040%, 0.050%, 0.060% and the like.

[0044] The content of P is controlled to be <0.012%, and the content of S is controlled to be <0.010%, and the positive effect is that P and S are usually considered as impurity elements in steel, and the lower the content is, the better, and for metal container packaging materials, too high content of P and S will also lead to reduced corrosion resistance of the materials. The content of P and S is limited to the range of P <0.012% and S <0.010% respectively. The content of P can be 0.003%, 0.005%, 0.007%, 0.009%, 0.012% and the like, and the content of S can be 0.003%, 0.005%, 0.007%, 0.009%, 0.010% and the like.

[0045] The content of N is controlled to be ≤0.003%, and the positive effect is that N combines with Al in steel to form coarse AlN particles under high temperature conditions, which deteriorates the toughness of the steel, and meanwhile, excessive solid-solution N atoms in the steel often lead to intensified performance fluctuation of the thin strip material before and after aging, and in view of the above, the content of N in the application is controlled to be ≤0.003%. The content of N can be 0.001%, 0.002%, 0.003% and the like.

[0046] In some embodiments, the ferrite grain size is 11.5-12.5, and the pearlite interlamellar spacing is 120-150 nm.

[0047] By reasonable design of C and Mn components and formulation of a two-phase region annealing process, refined ferrite grains and pearlite with small interlamellar spacing are obtained to realize high strength and high plasticity of the material. The ferrite grain size can be 11.5, 12.0, 12.5 and the like, and the pearlite interlamellar spacing can be 120 nm, 130 nm, 140 nm, 150 nm and the like.

[0048] In some embodiments, the ferrite grains are equiaxed polygonal, the pearlite is island-shaped distributed at the grain boundary position of the ferrite grains, and the tertiary cementite is granular and dispersedly distributed in the ferrite grains.

[0049] In a second aspect, the application provides a preparation method of the steel material in any one of the first aspect, please see Figure 1 , the method comprises:

[0050] S1, obtaining a casting blank;

[0051] S2, sequentially performing heating, hot rolling, coiling, pickling, cold rolling, continuous annealing and secondary cold rolling on the casting blank to obtain a steel product.

[0052] In some embodiments, the heating temperature is 1180-1220℃, the final rolling temperature of the rolling is 850-890℃, and the coiling temperature is 600-640℃.

[0053] The positive effect of controlling the heating temperature to be 1180-1220℃ is to ensure that the casting blank is fully heated in the heating process, eliminate columnar crystal organization in the casting blank, and improve the segregation and aggregation of alloy elements in the casting blank. The heating temperature can be 1180℃, 1190℃, 1200℃, 1210℃, 1220℃, etc.

[0054] The positive effect of controlling the final rolling temperature of the rolling to be 850-890℃ is to ensure that the strip steel is rolled in the γ single-phase zone, avoiding the uneven organization caused by rolling in the α+γ two-phase zone. The final rolling temperature of the rolling can be 850℃, 860℃, 870℃, 880℃, 890℃, etc.

[0055] The positive effect of controlling the coiling temperature to be 600-640℃ is to promote the precipitation of AlN phase in the steel to improve the aging of the finished product, while moderately coarsening the grains to reduce the subsequent cold rolling load. The cold rolling reduction rate is set to 85-90%, realizing the preliminary thinning of the strip steel thickness, and promoting the formation of α fiber texture in the cold-rolled thin strip steel. The coiling temperature can be 600℃, 610℃, 620℃, 630℃, 640℃, etc.

[0056] In some embodiments, the continuous annealing includes a preheating section, a heating section, a soaking section and a rapid cooling section, the outlet temperature of the preheating section is 150-180℃; the heating speed of the heating section is 20-30℃ / s, and the outlet temperature of the heating section is 730-750℃; the soaking temperature of the soaking section is 730-750℃, and the soaking time of the soaking section is 50-80s; the cooling speed of the rapid cooling section is 40-60℃ / s, and the final cooling temperature of the rapid cooling section is 200-250℃.

[0057] In the present application, annealing is an important production process, mainly involving four process parameters of heating rate, soaking temperature, rapid cooling section cooling speed and rapid cooling section final cooling temperature.

[0058] The outlet temperature of the preheating section can be 150℃, 160℃, 170℃, 180℃, etc.

[0059] The positive effect of controlling the heating rate of the heating section to be 20-30°C / s is to ensure that the strip steel quickly enters the temperature range of the soaking zone. If the heating rate is lower than 20°C / s, the strip steel stays in the high temperature range for too long during the heating process, which is not conducive to the refinement of the ferrite grains and the improvement of the plasticity of the microstructure after annealing. If the heating rate is higher than 30°C / s, the heating capacity of the production line is required to be higher, which makes it difficult to implement batch production stably.

[0060] The positive effect of controlling the soaking temperature to be 730-750°C is to ensure that the strip steel is soaked in the low temperature range of the α+γ two-phase region. If the soaking temperature is lower than 730°C, the retained cementite after cold rolling cannot be fully dissolved to form a certain volume fraction of austenite, which further prevents the subsequent austenite cooling phase change from being performed, and the final required pearlite structure cannot be obtained. If the soaking temperature is higher than 750°C, the cementite accelerates the dissolution to form excessive carbon-rich austenite structure, and the proportion of the pearlite structure increases and the interlamellar spacing is significantly coarsened during the subsequent cooling process. In addition, the ferrite grains formed by phase change and recrystallization grow rapidly at a too high soaking temperature, which is not conducive to the improvement of the plasticity of the material. The soaking temperature can be 730°C, 735°C, 740°C, 745°C, 750°C, etc.

[0061] The soaking time can be 50s, 55s, 60s, 65s, 75s, 80s, etc.

[0062] The positive effect of controlling the final cooling temperature of the rapid cooling section to be 200-250°C is that if the final cooling temperature is lower than 200°C, the overcooling degree is too large, and metastable phases such as residual austenite are formed in the structure, which leads to an increase in the performance fluctuation of the material before and after aging. The final cooling temperature of the rapid cooling section can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.

[0063] The positive effect of controlling the cooling rate of the rapid cooling section to be 40-60°C / s is that if the cooling rate is too low, the C element diffuses sufficiently, forming granular pearlite or pearlite with a coarsened interlamellar spacing, and the ferrite grains grow, which reduces the plasticity of the material. If the cooling rate is too high, the austenite cooling process causes non-pearlite phase change, forming martensite and other hard phases, which is also not conducive to the improvement of the plasticity and toughness of the material. The cooling rate of the rapid cooling section can be 40°C / s, 45°C / s, 50°C / s, 55°C / s, 60°C / s, etc.

[0064] In some embodiments, the cold rolling reduction rate is 85-90%, and the secondary cold rolling reduction rate is 8-12%.

[0065] The cold rolling reduction rate can be 85%, 86%, 87%, 88%, 89%, 90%, etc.

[0066] The positive effect of controlling the reduction ratio of the second cold rolling is 8% to 12%. The main purpose of the second cold rolling is to further reduce the thickness of the thin strip steel, and further improve the strength of the material and the shape of the thin strip steel. If the reduction ratio of the second cold rolling is less than 8%, the thickness of the finished product cannot be reduced, and the strength of the finished product cannot reach the target value. If the reduction ratio of the second cold rolling is higher than 12%, the work hardening is serious, which leads to the decrease of the elongation of the finished product and the increase of the anisotropy. The reduction ratio of the second cold rolling can be 8%, 9%, 10%, 11%, 12%, etc.

[0067] In a third aspect, the present application provides a packaging steel, which comprises a steel substrate and a functional layer attached to at least part of the surface of the steel substrate.

[0068] The steel substrate is the steel material according to any one of the embodiments of the first aspect.

[0069] The functional layer comprises at least one of a tin plating layer and a chromium plating layer.

[0070] In some embodiments, the packaging steel satisfies at least one of the following properties: thickness ≤0.18mm, tempering degree DR-9, hardness HR30T 71-81, yield strength Rp 0.2 ≥620MPa, earing rate <5%, RD, 45° and TD direction elongation >5%.

[0071] The packaging steel in the present application has excellent forming performance, further reduces the metal material for metal cans, and effectively improves the cracking, edge wrinkle and earing defects in the canning process. The thickness can be 0.12mm, 0.14mm, 0.16mm, 0.18mm, etc.; the hardness HR30T can be 71, 73, 76, 79, 81, etc.; the yield strength Rp 0.2 can be 620MPa, 630MPa, 650MPa, 700MPa, etc.; the earing rate can be 1%, 2%, 3%, 4%, etc.; the RD, 45° and TD direction elongation can be 5%, 8%, 10%, etc.

[0072] In a fourth aspect, the present application provides a metal can, which comprises a metal structural component made of the packaging steel according to any one of the embodiments of the third aspect, and the metal structural component comprises at least one of a can cover, a can body and a can bottom.

[0073] The preparation method of the steel material is based on the chemical composition of the above-mentioned steel material. The chemical composition of the steel material can refer to the above-mentioned embodiments. Since the preparation method of the steel material adopts part or all of the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0074] The present application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and not used to limit the scope of the present application. The experimental methods in the following examples, if no specific conditions are noted, are generally determined according to national standards. If there is no corresponding national standard, the general international standards, conventional conditions, or the conditions suggested by the manufacturer are used.

[0075] The raw materials in Examples 1-7 and Comparative Examples 1-7 of the present application are smelted to obtain the chemical compositions of the steel materials in Table 1.

[0076] The chemical compositions (wt%) of the steel materials in Table 1, with the rest being unavoidable impurities

[0077]

[0078] Based on the chemical compositions of the steel materials described above, the present application provides a method for preparing a packaging steel, which comprises:

[0079] S11, smelting and continuous casting using any one of the chemical compositions of the steel materials described above to obtain a to-be-rolled casting blank. It should be noted that RH refining is used during smelting;

[0080] S21, sequentially heating, hot rolling, coiling, pickling, cold rolling, continuous annealing, secondary cold rolling, and electroplating and post-processing of the casting blank to obtain a steel material;

[0081] S31, electroplating tin or chromium on the steel material to obtain a packaging steel, and the main process parameters are shown in Table 2.

[0082] Table 2 Main process parameters for preparing a packaging steel

[0083]

[0084] The finished product performance of the packaging steels obtained in Examples 1-7 and Comparative Examples 1-7 is tested, as shown in Table 3.

[0085] Table 3 Finished product performance of the packaging steel

[0086]

[0087]

[0088] Detailed description of Tables 1-3:

[0089] As can be seen from Comparative Example 1 and Examples 1-7, when the content of the main element C exceeds the upper limit range of 0.15% given by the present application, the surface hardness and strength level of the finished product are improved, but the elongation after fracture decreases significantly, especially the elongation in the TD direction decreases to less than 5%.

[0090] As can be seen from Comparative Example 2 and Examples 1-7, when the content of the main element Mn exceeds the lower limit range 0.5% given in the present application, the surface hardness and strength level of the finished product are both reduced, wherein the three-direction yield strengths Rp0.2 in the RD, 45° and TD directions are all reduced to below 620 MPa. 0.2 The surface hardness and strength of the finished product are both reduced, wherein the three-direction yield strengths Rp0.2 in the RD, 45° and TD directions are all reduced to below 620 MPa.

[0091] As can be seen from Comparative Example 3 and Examples 1-7, when the heating rate of the heating section of the key annealing process parameter is lower than the lower limit range 20℃ / s given in the present application, the surface hardness, strength and elongation after fracture of the finished product are all reduced, wherein the three-direction yield strengths Rp0.2 in the RD, 45° and TD directions are all reduced to below 620 MPa, and the elongations after fracture in the RD, 45° and TD directions are all reduced to below 5%. 0.2 The surface hardness and strength of the finished product are both reduced, wherein the three-direction yield strengths Rp0.2 in the RD, 45° and TD directions are all reduced to below 620 MPa, and the elongations after fracture in the RD, 45° and TD directions are all reduced to below 5%.

[0092] As can be seen from Comparative Example 4 and Examples 1-7, when the soaking temperature of the soaking section of the key annealing process parameter exceeds the upper limit range 750℃ given in the present application, the surface hardness, strength and elongation after fracture of the finished product are all reduced, wherein the three-direction yield strengths Rp0.2 in the RD, 45° and TD directions are all reduced to below 620 MPa, and the elongations after fracture in the 45° and TD directions are both reduced to below 5%. 0.2 The surface hardness and strength of the finished product are both reduced, wherein the three-direction yield strengths Rp0.2 in the RD, 45° and TD directions are all reduced to below 620 MPa, and the elongations after fracture in the 45° and TD directions are both reduced to below 5%.

[0093] As can be seen from Comparative Example 5 and Examples 1-7, when the cooling rate after soaking of the key annealing process parameter exceeds the upper limit range 60℃ / s given in the present application, the surface hardness and strength of the finished product are both improved, but the elongations after fracture in the RD, 45° and TD directions are all reduced to below 5%.

[0094] As can be seen from Comparative Example 6 and Examples 1-7, when the final cooling temperature of the fast cooling section after soaking of the key annealing process parameter exceeds the lower limit range 200℃ / s given in the present application, the surface hardness and strength of the finished product are both improved, but the elongations after fracture in the RD, 45° and TD directions are all reduced to below 5%.

[0095] As can be seen from Comparative Example 7 and Examples 1-7, when the secondary cold rolling reduction after annealing of the key cold rolling process parameter exceeds the upper limit range 12% given in the present application, the surface hardness and strength of the finished product are both greatly improved, but the earing rate of the finished product exceeds 5%, and the elongations after fracture in the RD, 45° and TD directions are all reduced to below 5%.

[0096] The detailed description of the steel material prepared in Example 1 is shown in Table 1. Figure 2 and 3 The detailed description of the steel material prepared in Example 1 is shown in Table 1.

[0097] As Figure 2 shown in Table 1, the microstructure of the steel material prepared in Example 1 is shown in Figure 1, from which it can be seen that the average grain size of the ferrite of the material is 5.0μm, and the grain size reaches 12.0 grade, and the actual grain size is controlled in the range of 11.5 grade to 12.5 grade.

[0098] As Figure 3 shown, the pearlite structure of the steel material prepared in Example 1 is a transmission electron microscope morphology diagram, and it can be seen from the diagram that the ferrite and cementite lamellar spacing in the structure is controlled in the range of 120-150 nm.

[0099] One or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0100] (1) The DR material for DRD thin-wall cans provided by the embodiments of the present application has a thickness controlled at ≤0.18 mm, a quenching and tempering degree reaching the DR-9 level, a surface hardness value HR30T of 76±5, a yield strength Rp 0.2 ≥620 MPa, an earing rate <5%, and a post-break elongation rate >5% in RD, 45° and TD directions, good comprehensive forming performance, improved cracking, wrinkling and earing defects in the processing of the can body, and the ability to meet the processing and manufacturing technical requirements of metal containers such as DRD thin-wall cans.

[0101] (2) The DR material for DRD thin-wall cans provided by the embodiments of the present application has the following advantages in production process. The present application adopts a low-carbon composition design and a two-phase zone low-temperature annealing + rapid cooling process, realizes high strength and high plasticity of the material through refined ferrite grains and fine pearlite structure with small lamellar spacing, does not need to add other alloy elements, has a low annealing soaking temperature, a moderate cooling speed, low requirements for production line process equipment, strong process implementability, and helps to control the stability of product organization and performance in batch production. Small secondary cold rolling reduction is adopted, the rolling load of the rolling mill is small in actual production, the energy consumption is low, the production efficiency is high, and the elongation and anisotropy of the finished product are significantly improved.

[0102] The above is merely a specific embodiment of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied herein.

Claims

1. Steel material, characterized in that, The chemical composition of the steel material comprises C, Si, Mn, Alt, P, S, N, and the balance of Fe, wherein the mass fraction of C is 0.12% to 0.15%, the mass fraction of Si is ≤0.03%, the mass fraction of Mn is 0.50% to 0.80%, the mass fraction of Alt is 0.030% to 0.060%, the mass fraction of P is <0.012%, the mass fraction of S is <0.010%, and the mass fraction of N is ≤0.003%. The content of C is 0.12% to 0.15%, the content of Si is ≤0.03%, the content of Mn is 0.50% to 0.80%, the content of Alt is 0.030% to 0.060%, the content of P is <0.012%, the content of S is <0.010%, and the content of N is ≤0.003%. The microstructure of the steel material comprises ferrite, pearlite, and tertiary cementite, wherein the volume fraction of the ferrite is 80% to 88%, the volume fraction of the pearlite is 10% to 15%, and the volume fraction of the tertiary cementite is 2% to 5%. The content of the ferrite is 80% to 88%, the content of the pearlite is 10% to 15%, and the content of the tertiary cementite is 2% to 5%. The preparation method of the steel material comprises the following steps: obtaining a casting blank; sequentially performing heating, hot rolling, coiling, pickling, cold rolling, continuous annealing, and secondary cold rolling on the casting blank to obtain a steel material, The continuous annealing comprises a preheating section, a heating section, a soaking section, and a rapid cooling section, the outlet temperature of the preheating section is 150°C to 180°C, the heating speed of the heating section is 20°C / s to 30°C / s, the outlet temperature of the heating section is 730°C to 750°C, the soaking temperature of the soaking section is 730°C to 750°C, the soaking time of the soaking section is 50s to 80s, and the cooling speed of the rapid cooling section is 40°C / s to 60°C / s, and the final cooling temperature of the rapid cooling section is 200°C to 250°C.

2. The steel material according to claim 1, characterized by The ferrite grain size is 11.5 to 12.5, and the pearlite lamellar spacing is 120nm to 150nm.

3. The steel material according to claim 1, characterized by The ferrite grains are equiaxial polygonal, the pearlite is island-shaped distributed at the grain boundary position of the ferrite grains, and the tertiary cementite is granular and dispersedly distributed in the ferrite grains.

4. A method of producing the steel material according to any one of claims 1 to 3, characterized by, The method comprises the following steps: obtaining a casting blank; sequentially performing heating, hot rolling, coiling, pickling, cold rolling, continuous annealing, and secondary cold rolling on the casting blank to obtain a steel material.

5. The method of claim 4, wherein, The total reduction rate of the cold rolling is 85% to 90%, and the total reduction rate of the secondary cold rolling is 8% to 12%.

6. The method of claim 4, wherein, The heating temperature is 1180°C to 1220°C, the final rolling temperature of the hot rolling is 850°C to 890°C, and the coiling temperature is 600°C to 640°C.

7. A steel for packaging, characterized in that, The packaging steel comprises a steel material substrate and a functional layer attached to at least part of the surface of the steel material substrate; The steel material substrate is the steel material according to any one of claims 1 to 3; The functional layer comprises at least one of a tin plating layer and a chromium plating layer.

8. A steel for packaging according to claim 7, characterized in that, The steel for packaging satisfies at least one of the following properties: thickness ≤ 0.18 mm, quenching and tempering degree DR-9, hardness HR30T 71-81, yield strength Rp 0.2 ≥ 620 MPa, earing rate < 5%, RD, 45° and TD direction elongation > 5%.

9. A metal can characterized by, The metal can comprises a metal structural part made of the packaging steel according to claim 7 or 8, and the metal structural part comprises at least one of a can lid, a can body, and a can bottom.

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