Steel for metal packaging tin body and preparation method thereof

Abstract

The invention discloses steel for a metal packaging tin body and a preparation method of the steel, and belongs to the technical field of metallurgy, the steel comprises a steel matrix, and the steel matrix comprises the following chemical components in percentage by mass: 0.056-0.075% of C, 0.036-0.045% of Si, 0.56-0.65% of Mn, 0.051-0.060% of P, less than or equal to 0.0030% of S, 0.36-0.45% of Cu, 0.012-0.015% of Ln, 0.010-0.040% of Al, 0.026-0.035% of V, 0.016-0.025% of Ti, less than or equal to 0.0030% of O, less than or equal to 0.0040% of N and the balance of iron and inevitable impurity elements. By adding rare earth elements, the number and size of inclusions can be remarkably reduced, the mechanical strength of the steel is improved, and the obtained steel for the metal packaging tin body has excellent pressure-bearing performance.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to steel for a metal packaging can body and a preparation method thereof. Background Art

[0002] Metal packaging cans consist of three parts: the top cover, the can body, and the bottom cover, each of which is formed independently. The can body is mainly made of steel. Metal packaging cans are generally used to package products such as gas and liquid, so there are strict requirements on the corrosion resistance and pressure bearing performance of the steel used for the can body.

[0003] However, the inclusion control, corrosion resistance and pressure bearing performance of the steel used for metal packaging cans produced by conventional composition systems are poor. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of the prior art of steel for metal packaging can bodies, such as poor inclusion control, corrosion resistance and pressure bearing performance, thereby providing a steel for metal packaging can bodies and a preparation method thereof.

[0005] To this end, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a steel for a metal packaging can body, comprising a steel matrix, wherein the chemical composition of the steel matrix comprises, by mass percentage: C: 0.056-0.075%, Si: 0.036-0.045%, Mn: 0.56-0.65%, P: 0.051-0.060%, S: ≤0.0030%, Cu: 0.36-0.45%, Ln: 0.012-0.015%, Al: 0.010-0.040%, V: 0.026-0.035%, Ti: 0.016-0.025%, O: ≤0.0030%, N: ≤0.0040%, and the remainder is iron and unavoidable impurity elements;

[0007] Deterioration index M Ln =Ln / [7.8(O)+3.46(S)+0.89(Al)]=0.2~0.6;

[0008] Comprehensive weather resistance index I M =[26.01(Cu)+1.49(Si)+17.28(P)-33.39(Cu) 2 ]+38.73(Ln) 0.317 ≥14;

[0009] Strengthening Index S (Ln+V+Ti) =[1.23(Ln)+1.06(V)+(Ti)] / [3.42(N)+1.5(O)+3.0(S)]=5.50~7.00.

[0010] Calculate M Ln ,I M and S (Ln+V+Ti) When calculating, use the value before the percentage sign. For example, if the content of O is a%, substitute a into the formula for calculation.

[0011] Furthermore, the steel for the metal packaging can body also includes a tin coating on at least one side of the steel substrate; preferably, the amount of tin coating on one side is 0.5 to 0.8 g / m 2 ; Preferably, the thickness of the steel used for the body of the metal packaging can is 0.15 to 0.50 mm.

[0012] The present invention I M =[26.01(Cu)+1.49(Si)+17.28(P)-33.39(Cu) 2 ]+38.73(Ln) 0.317 ≥14. The tin coating can further improve the corrosion resistance. M ≥14, only a small amount of tin plating is required (the tin plating amount on one side is 0.5~0.8g / m 2 ) can achieve higher corrosion resistance and meet the application in non-food packaging field.

[0013] Furthermore, the Ln includes: Ce, Pr, Nd, and the mass ratio is (4-5): (2-3): 1.

[0014] C is an important element for improving the strength of steel, but too high a C content will reduce the plasticity of the steel and affect the formability of the steel. In order to make the product have good performance matching, the C content in the present invention is controlled at 0.056-0.075%.

[0015] Si is a ferrite-forming element, which is beneficial to the hot rolling and low temperature rolling production of steel, can improve the strength of the solid solution in steel, and is more significant in improving the tensile strength of steel. Moreover, when Si is combined with elements such as Cu, P, and Ln, the corrosion resistance of steel can be improved. When the silicon content is relatively high, it is beneficial to refine the corrosion product α-FeOOH, promote the formation of a dense silicon-rich protective rust layer on the surface of the steel, thereby improving the corrosion resistance. However, if the silicon content is too high, strip-shaped aluminum-silicon inclusions will be formed, and the surface oxide scale of the steel will also be aggravated. Therefore, the Si content in the present invention is controlled to be 0.036-0.045%.

[0016] Mn is one of the important solid solution strengthening elements in steel, but too high Mn content will not only reduce the elongation and damage the toughness of steel, but also reduce the corrosion resistance of steel and increase the manufacturing cost. Therefore, the Mn content in the present invention is controlled at 0.56-0.65%.

[0017] P can improve the corrosion resistance of steel and has a strong solid solution strengthening effect, but P is easy to segregate at the grain boundary to reduce the toughness of the steel. Therefore, the P content of the present invention is controlled at 0.051-0.060%.

[0018] S is a harmful element in steel. It is easy to form long strips of sulfide inclusions, which deteriorate the plasticity, toughness and corrosion resistance of steel. It is easy to combine with Ti to form Ti4C2S2, which reduces the Ti content that has a strengthening effect, thereby affecting the strengthening effect of the microalloying element Ti. Therefore, the present invention controls the S content to ≤0.0030%.

[0019] Cu is the most common alloying element for improving the corrosion resistance of steel. During the corrosion process, it is mainly distributed in the outer corrosion product film in the form of CuS, which prevents the corrosion medium from penetrating into the inner layer and passivates the matrix. However, Cu has a low melting point and a high content can easily lead to the "copper brittleness" phenomenon. Therefore, the Cu content of the present invention is controlled at 0.36-0.45%.

[0020] Ln represents three rare earth elements, Ce, Pr and Nd, and can improve the comprehensive performance of steel by purifying steel, modifying inclusions, refining grains, etc., and can also significantly improve the corrosion resistance of steel. However, if the Ln content of steel is too high during heat treatment, solid solution Ln desolvation is likely to occur, making the grain boundaries brittle and deteriorating the performance of the steel. Therefore, the Ln content of the present invention is controlled at 0.012-0.015%.

[0021] In order to ensure the modification effect of reducing, refining and spheroidizing inclusions, the chemical composition of the steel of the present invention must meet the modification index M Ln = Ln / [7.8(O)+3.46(S)+0.89(Al)] = 0.2 to 0.6, and within this range, with M Ln As the inclusion rate increases, the modification effect becomes better and better, reducing the adverse effects of inclusions on steel properties.

[0022] Al is an important deoxidizing element in steel and can form AlN particles with N in steel to refine the grain size. At the same time, Als fixes the free N in the steel and increases the content of effective V and Ti in the steel. However, excessive Al will form a large number of dispersed needle-shaped Al2O3 inclusions in the steel, reducing the toughness and formability of the steel. Therefore, the present invention controls the Al content to 0.010-0.040%.

[0023] V is a strong carbonitride-forming element. The solid solubility of vanadium in austenite is large. The formation temperature of VN is slightly higher than the Ac3 temperature of low carbon steel. It has little effect on the recrystallization process of deformed austenite, so the effect of vanadium on grain refinement is weak. The precipitation temperature of V(C,N) is low. After subsequent rapid cooling, V(C,N) will precipitate in large quantities in the transformed ferrite, resulting in significant precipitation strengthening. It is rare for vanadium to be alloyed alone in microalloyed steel.

[0024] Ti is also a strong carbonitride-forming element. TiN or Ti(C,N) can hinder the growth of austenite grains during heating and hot rolling. The TiC dispersed and precipitated during the subsequent cooling or coiling process can also improve the strength of the steel, play a role in precipitation strengthening and fine grain strengthening, reduce the anisotropy of the strip, and improve the formability. However, if the Ti content is too high, the size and number of the second phase precipitates TiN will increase, which will affect the formability of the steel plate.

[0025] In V-Ti composite microalloyed steel, titanium inhibits grain growth to improve toughness, while vanadium mainly plays a role in precipitation strengthening. It is ideal for V-Ti steel to adopt recrystallization controlled rolling process, because TiN precipitates at very high temperature, thus reducing the nitrogen content in austenite and inhibiting the precipitation of VN. Moreover, VN is not easy to precipitate during low-temperature rolling. Finally, the vanadium remaining in austenite can form a precipitation phase at a lower temperature after the ferrite phase transformation, thereby improving the strength of the finished steel. Therefore, this steel adopts V-Ti composite microalloying, and controls the V content at 0.026-0.035% and the Ti content at 0.016-0.025%.

[0026] Through V-Ti composite microalloying, the precipitation temperature of V and Ti carbonitrides is low, and they are not precipitated before hot rolling, so the material strength is low. In the subsequent hot rolling layer cooling and rapid cooling after annealing, a large amount of precipitation will be produced in the transformed ferrite, and the precipitation strengthening will increase the strength of the steel, and Ln microalloying will be carried out, while satisfying the strengthening index S (Ln+V+Ti) In the range of 5.50 to 7.00, the effective combination of "low load in hot rolling and high strength after rolling" can be achieved, and the interaction between different micro-alloying elements when titanium and vanadium are used in combination can be fully utilized.

[0027] O and N have extremely strong affinity with vanadium and titanium. Oxygen in molten steel combines with vanadium and titanium to form vanadium-titanium oxides, and N combines with Ti to form coarse TiN particles, thereby reducing the titanium content in the molten steel that has a strengthening effect and reducing the strengthening effect of titanium. At the same time, a high O content is prone to form string-like oxide inclusions, which reduces the formability of the steel. Therefore, the O content of the present invention is controlled at ≤0.0030% and the N content is controlled at ≤0.0040%.

[0028] Furthermore, the thickness of the steel used for the body of the metal packaging can is 0.15 to 0.50 mm.

[0029] In a second aspect, the method for preparing the steel for the body of a metal packaging can of the present invention comprises molten steel smelting→continuous casting→heating of ingots→rough rolling→finishing rolling→laminar cooling→acid continuous rolling→continuous annealing→tin plating.

[0030] Furthermore, the continuous casting speed is 2.0-2.5 m / min, the thickness of the ingot is 150-170 mm, the width of the ingot is ≤1200 mm, and the length of the ingot is 9500-11500 mm.

[0031] Furthermore, the heating of the ingot includes hot charging the ingot into a furnace, wherein the ingot entering the furnace is ≥900°C, the heating time is controlled at ≥150min, and the out-of-furnace temperature is 1080-1120°C.

[0032] Furthermore, the outlet temperature of the rough rolling is 925-965°C, and the thickness of the intermediate billet obtained by the rough rolling is 30-33 mm; the rough rolling adopts a two-stand R1+R2=3+3 mode, R1 adopts 3 passes of rolling, and R2 adopts 3 passes of rolling;

[0033] The inlet temperature of the finishing rolling is 845-885°C, the outlet temperature of the finishing rolling is 760-800°C, and the total reduction rate of the finishing rolling is 85.5%-93.9%;

[0034] The outlet temperature of the laminar cooling is 560-600°C.

[0035] In hot rolling and low temperature rolling, the rolling load of the rolling mill decreases as the temperature decreases within a certain temperature range, but the hot rolling temperature cannot be too low. If it is too low, the rolling load will increase, and the energy and roll consumption will also increase synchronously, and it is very easy to cause production accidents such as rolling load overload. The cold-rolled base material produced by the low-temperature process has a low strength, which can effectively reduce the cold rolling load, save energy and reduce consumption, and appropriately increase the cold rolling deformation to improve production efficiency; the cold-rolled annealed products produced by the low-temperature process have good anisotropy and excellent forming performance.

[0036] Furthermore, the pickling continuous rolling includes pickling and cold rolling:

[0037] Preferably, the temperature of the steel before pickling is less than 45°C, the pickling medium is a hydrochloric acid solution with a concentration of 30 to 200 g / L, and the temperature of the hydrochloric acid solution is 85 to 95°C; after pickling, a rinsing liquid is used to remove the hydrochloric acid solution on the surface of the steel, the temperature of the rinsing liquid is 75 to 85°C, the pH value of the outlet tank rinsing liquid is greater than 6.0, and the conductivity of the outlet tank rinsing liquid is ≤30 μS / cm;

[0038] Preferably, the total reduction ratio of the cold rolling is 75.0% to 94.4%.

[0039] Furthermore, the continuous annealing includes: processing the steel strip obtained by cold rolling through an annealing section, a controlled cooling section and a flattening section;

[0040] Preferably, the strip speed of the steel strip is 560-600 m / min;

[0041] Preferably, the annealing section includes a heating section and a heat preservation section in sequence;

[0042] Preferably, the heating rate of the heating section is 12.02-13.73°C / s, and the soaking temperature of the insulation section is 610-650°C;

[0043] Preferably, the controlled cooling section includes a quick cooling section, a radiation tube cooling section, and a jet cooling section in sequence;

[0044] Preferably, the rapid cooling rate is 86.67-121.43°C / s, the radiation cooling rate is 0.73-0.79°C / s, and the jet cooling rate is 1.71-1.83°C / s;

[0045] The leveling section adopts a two-frame leveling machine for leveling. The working roll surface roughness Ra of the leveling machine is 1.1-1.8 μm, and the peak count Rpc of the roll surface roughness is 130-170 cm -1 ;

[0046] Preferably, the flattening elongation of the flattening section is 1.7% to 2.1%, and the flattening tension is 85 to 90 kN.

[0047] Furthermore, the tinning comprises: electroplating, reflowing and passivating the steel strip obtained by continuous annealing;

[0048] Preferably, the speed of the steel belt is 320-380 m / min;

[0049] Preferably, the electroplating solution is a MSA plating solution with a concentration of 125 to 135 g / L, wherein the free acid concentration is 30 to 45 mL / L, and the Sn content in the solution is 2+ Ion concentration is 10-40 g / L;

[0050] Preferably, the reflow temperature of the reflow is 258-263°C;

[0051] Preferably, the passivation uses a sodium dichromate solution with a concentration of 13 to 18 g / L as the passivation solution, a pH value of 4.0 to 4.3, and a passivation temperature of 40 to 45°C.

[0052] The technical solution of the present invention has the following advantages:

[0053] 1. The present invention provides a steel for a metal packaging can body, comprising a steel matrix, wherein the chemical composition of the steel matrix comprises, by mass percentage, C: 0.056-0.075%, Si: 0.036-0.045%, Mn: 0.56-0.65%, P: 0.051-0.060%, S: ≤0.0030%, Cu: 0.36-0.45%, Ln: 0.012-0.015%, Al: 0.010-0.040%, V: 0.026-0.035%, Ti: 0.016-0.025%, O: ≤0.0030%, N: ≤0.0040%, and the rest are iron elements and unavoidable impurity elements;

[0054] Deterioration index M Ln =Ln / [7.8(O)+3.46(S)+0.89(Al)]=0.2~0.6;

[0055] Comprehensive weather resistance index I M =[26.01(Cu)+1.49(Si)+17.28(P)-33.39(Cu) 2 ]++38.73(Ln) 0.317 ≥14;

[0056] Strengthening Index S (Ln+V+Ti) =[1.23(Ln)+1.06(V)+(Ti)] / [3.42(N)+1.5(O)+3.0(S)]=5.50~7.00.

[0057] The invention can reduce the content of harmful elements in steel and segregation at grain boundaries by adding an appropriate amount of Ln rare earth element, and has the effect of purifying steel quality; by adding an appropriate amount of Ln rare earth element, the shape, size, distribution, composition, structure and type of inclusions in the steel for the body of a metal packaging can can be changed, and inclusions can be reduced, refined and spheroidized, thereby improving the comprehensive mechanical properties of the steel for the body of the metal packaging can, avoiding defects such as holes and pinholes generated during acid continuous rolling and welding, and improving the air tightness of the metal packaging can; at the same time, through the comprehensive effects of Ln rare earth element, Cu, P, V, Ti and other elements, the corrosion resistance and pressure bearing performance of the steel for the body of the metal packaging can can be significantly improved.

[0058] The present invention uses V-Ti composite microalloying and Ln microalloying, and at the same time, the strengthening index S (Ln+V+Ti) [1.23(Ln)+1.06(V)+(Ti)] / [3.42(N)+1.5(O)+3.0(S)]=5.50~7.00 to give full play to the interaction between different microalloying elements when titanium and vanadium are used in combination.

[0059] The present invention adopts a C-Mn component system and performs Cu, P, V, Ti and Ln microalloying to meet the modification index M Ln =Ln / [7.8(O)+3.46(S)+0.89(Al)]=0.2~0.6; Comprehensive weather resistance index I M =[26.01(Cu)+1.49(Si)+17.28(P)-33.39(Cu) 2 ]+38.73(Ln) 0.317 ≥14; Strengthening index S (Ln+V+Ti) =[1.23(Ln)+1.06(V)+(Ti)] / [3.42(N)+1.5(O)+3.0(S)]=5.50~7.00, which can improve the comprehensive mechanical properties, performance, corrosion resistance and pressure bearing performance of the steel used for the metal packaging can body, avoid defects such as holes and pinholes during acid continuous rolling and welding, and improve the airtightness of the metal packaging can.

[0060] 2. In the method for preparing the steel for the metal packaging can body of the present invention, the outlet temperature of rough rolling is 925-965°C, and the thickness of the intermediate billet obtained by rough rolling is 30-33 mm; the inlet temperature of finishing rolling is 845-885°C, the outlet temperature of finishing rolling is 760-800°C, and the total reduction rate of finishing rolling is 85.5%-93.9%.

[0061] The steel for the body of the metal packaging can of the present invention adopts a suitable low-temperature process, low-temperature heating + low-temperature rolling, which reduces the consumption of heating energy and the oxidation and burning of steel, and improves the yield rate and production efficiency; low-temperature rolling can reduce fatigue cracking and fracture caused by thermal stress of the temperature rise of the rolling roller, and reduce the consumption of the rolling roller; the low-temperature temperature system can reduce the generation of secondary iron oxide scale, improve the surface quality of hot-rolled products, and the pickling effect and efficiency in acid continuous rolling; the cold-rolled base material produced by the low-temperature process has low strength, which can effectively reduce the cold-rolling load, save energy and reduce consumption, and can appropriately increase the cold-rolling deformation to improve production efficiency; the cold-rolled annealed products produced by the low-temperature process have good anisotropy and excellent forming performance.

[0062] 3. The hot rolling low temperature process of the present invention combines the comprehensive control of process dimensions such as ingot thickness, ingot width, ingot length, intermediate ingot thickness, total reduction rate of hot rolling and finishing rolling, and total reduction rate of cold rolling, which can further reduce the hot rolling and cold rolling loads and roll consumption.

[0063] By adopting the component system and preparation method of the present invention, the steel for the body of metal packaging cans with a thickness of 0.15 to 0.50 mm can be stably produced. The product has good forming performance and pressure bearing performance, and the surface quality meets customer requirements. The low-temperature and low-load rolling production of the steel for the body of metal packaging cans is realized, and the overall energy saving, cost reduction and consumption reduction are achieved, which has considerable social and economic benefits and belongs to the category of low-energy consumption green manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0065] Figure 1 This is a metallographic structure morphology diagram of the steel used for the metal packaging can body in Example 1 of the present invention. DETAILED DESCRIPTION

[0066] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0067] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0068] Example 1

[0069] The present embodiment provides a steel for a metal packaging can body, wherein the chemical composition and mass percentage of the steel matrix are C: 0.064%, Si: 0.040%, Mn: 0.59%, P: 0.055%, S: 0.0009%, Cu: 0.37%, Ln=Ce+Pr+Nd: 0.013% (the mass ratio of Ce, Pr, and Nd is 5:3:1), Al: 0.028%, V: 0.027%, Ti: 0.019%, O: 0.0014%, N: 0.0013%, and the remainder is Fe and unavoidable impurities, as shown in Table 1.

[0070] The values ​​of the deterioration index, comprehensive weathering index and strengthening index are shown in Table 2.

[0071] The preparation method of the above-mentioned steel for the body of the metal packaging can comprises molten steel smelting → continuous casting → heating of the ingot → rough rolling → finishing rolling → laminar cooling → acid continuous rolling → continuous annealing → tinning, and specifically comprises the following steps:

[0072] 1. Molten steel smelting: smelting raw materials into molten steel with the above composition.

[0073] 2. Continuous casting: continuous casting speed 2.5m / min, ingot thickness 150mm, ingot width 1100mm, ingot length 11500mm.

[0074] 3. Billet heating → rough rolling → finishing rolling → laminar cooling: the billet is hot charged into the furnace, the furnace entry temperature is 971°C, the heating time is 169min, the furnace exit temperature is 1117°C, the hot rolling and rough rolling adopts two-stand R1+R2=3+3 mode, R1 adopts 3 rolling passes, R2 adopts 3 rolling passes, the outlet temperature of R2 rough rolling is 956°C, the thickness of the intermediate billet obtained by rough rolling is 30mm, the finishing rolling inlet temperature is 869°C, the finishing rolling outlet temperature is 799°C, the total finishing reduction rate is 93.3%, and the laminar cooling outlet temperature is 583°C.

[0075] 4. Acid continuous rolling: the temperature of the hot-rolled raw material before pickling is less than 45°C, the pickling medium is a hydrochloric acid solution with a concentration of 30-200g / L, the temperature of the hydrochloric acid solution is 85°C, and after pickling, a rinsing liquid is used to remove the hydrochloric acid solution on the surface of the steel. The rinsing liquid temperature is 79°C, the pH value of the outlet tank rinsing water is greater than 6.0, the conductivity of the outlet tank rinsing water is ≤30μS / cm, and the total cold rolling reduction is 92.5%.

[0076] 5. Continuous annealing: The steel strip obtained by acid continuous rolling is sent to the continuous annealing furnace (steel strip speed 577m / min), and is processed through the annealing section, controlled cooling section and flattening section.

[0077] The continuous annealing furnace has a heating section length of 470m, a heat preservation section length of 300m, a rapid cooling section length of 14m, a radiation tube cooling section length of 635m, and a jet cooling section length of 164m.

[0078] In the annealing stage, the heating rate of the heating stage is 12.86°C / s, and the uniform heating temperature of the holding stage is 633°C.

[0079] During controlled cooling, the rapid cooling rate was 105.10°C / s, the radiation cooling rate was 0.76°C / s, and the jet cooling rate was 1.76°C / s.

[0080] The leveling section adopts two-frame leveling, the surface roughness Ra of the leveling machine working roll is 1.1~1.8μm, and the peak count Rpc of the roll surface roughness is 130~170cm -1 , flattening elongation 2.0%, flattening tension 88kN.

[0081] Tin plating: The steel strip obtained by continuous annealing (steel strip speed 375m / min) is electroplated, soft-melted and passivated.

[0082] In the electroplating process, the electroplating solution is a 130 g / L MSA plating solution, wherein the free acid concentration is 44 mL / L, and the Sn content in the solution is 2+ The ion concentration is 23g / L, and the tin coating amount on one side is 0.7g / m2 ;

[0083] The reflow temperature of the reflow is 260°C, and the passivation solution is a 16g / L sodium dichromate solution with a pH value of 4.1 and a passivation temperature of 44°C.

[0084] The thickness of the obtained steel product for the metal packaging can body is 0.15 mm. The inclusions, mechanical properties and surface conditions are shown in Tables 3 and 4.

[0085] The metal packaging can body obtained in this embodiment was observed by metallographic microscope. Figure 1 As shown. Figure 1 It can be seen that the metallographic structure of the steel for the easy-open end provided in this embodiment is ferrite+cementite.

[0086] Example 2

[0087] The present embodiment provides a steel for a metal packaging can body, wherein the chemical composition and mass percentage of the steel matrix are C: 0.057%, Si: 0.037%, Mn: 0.63%, P: 0.057%, S: 0.0015%, Cu: 0.44%, Ln=Ce+Pr+Nd: 0.015% (the mass ratio of Ce, Pr, and Nd is 5:2:1), Al: 0.033%, V: 0.031%, Ti: 0.023%, O: 0.0013%, N: 0.0015%, and the remainder is Fe and unavoidable impurities, as shown in Table 1.

[0088] The values ​​of the deterioration index, comprehensive weathering index and strengthening index are shown in Table 2.

[0089] The preparation method of the above-mentioned steel for the body of the metal packaging can comprises molten steel smelting → continuous casting → heating of the ingot → rough rolling → finishing rolling → laminar cooling → acid continuous rolling → continuous annealing → tinning, and specifically comprises the following steps:

[0090] 1. Molten steel smelting: smelting raw materials into molten steel with the above composition.

[0091] 2. Continuous casting: continuous casting speed 2.5m / min, ingot thickness 160mm, ingot width 1100mm, ingot length 11000mm.

[0092] 3. Billet heating → rough rolling → finishing rolling → laminar cooling: the billet is hot charged into the furnace, the furnace entry temperature is 935°C, the heating time is 173min, the furnace exit temperature is 1118°C, the hot rolling and rough rolling adopts two-stand R1+R2=3+3 mode, R1 adopts 3 rolling passes, R2 adopts 3 rolling passes, the outlet temperature of R2 rough rolling is 946°C, the thickness of the intermediate billet obtained by rough rolling is 32mm, the finishing rolling inlet temperature is 885°C, the finishing rolling outlet temperature is 797°C, the total finishing reduction rate is 92.2%, and the laminar cooling outlet temperature is 596°C.

[0093] 4. Acid continuous rolling: the temperature of the hot-rolled raw material before pickling is less than 45°C, the pickling medium is a hydrochloric acid solution with a concentration of 30-200g / L, the temperature of the hydrochloric acid solution is 89°C, and after pickling, a rinsing liquid is used to remove the hydrochloric acid solution on the surface of the steel. The rinsing liquid temperature is 77°C, the pH value of the outlet tank rinsing water is greater than 6.0, the conductivity of the outlet tank rinsing water is ≤30μS / cm, and the total cold rolling reduction is 90.0%.

[0094] 5. Continuous annealing: The steel strip obtained by acid continuous rolling is sent to the continuous annealing furnace (steel strip speed 583m / min), and is processed through the annealing section, controlled cooling section and flattening section.

[0095] The continuous annealing furnace has a heating section length of 470m, a heat preservation section length of 300m, a rapid cooling section length of 14m, a radiation tube cooling section length of 635m, and a jet cooling section length of 164m.

[0096] In the annealing stage, the heating rate of the heating stage is 13.11°C / s, and the uniform heating temperature of the holding stage is 639°C.

[0097] During controlled cooling, the rapid cooling rate was 110.35°C / s, the radiation cooling rate was 0.76°C / s, and the jet cooling rate was 1.78°C / s.

[0098] The leveling section adopts two-frame leveling, the surface roughness Ra of the leveling machine working roll is 1.1~1.8μm, and the peak count Rpc of the roll surface roughness is 130~170cm -1 , flattening elongation 2.1%, flattening tension 89kN.

[0099] Tin plating: The steel strip obtained by continuous annealing (steel strip speed 380m / min) is electroplated, soft-melted and passivated.

[0100] In the electroplating process, the electroplating solution is a MSA plating solution with a concentration of 128 g / L, wherein the free acid concentration is 39 mL / L, and the Sn content in the solution is 2+ The ion concentration is 30g / L, and the tin coating amount on one side is 0.6g / m 2 ;

[0101] The reflow temperature of the reflow is 259°C, and the passivation solution is a 15g / L sodium dichromate solution with a pH value of 4.0 and a passivation temperature of 45°C.

[0102] The thickness of the obtained steel product for the metal packaging can body is 0.25 mm. The inclusions, mechanical properties and surface conditions are shown in Tables 3 and 4.

[0103] Example 3

[0104] The present embodiment provides a steel for a metal packaging can body, wherein the chemical composition and mass percentage of the steel matrix are C: 0.061%, Si: 0.041%, Mn: 0.58%, P: 0.053%, S: 0.0013%, Cu: 0.38%, Ln=Ce+Pr+Nd: 0.012% (the mass ratio of Ce, Pr, Nd is 4:3:1), Al: 0.035%, V: 0.028%, Ti: 0.021%, O: 0.0011%, N: 0.0017%, and the remainder is Fe and unavoidable impurities, as shown in Table 1.

[0105] The values ​​of the deterioration index, comprehensive weathering index and strengthening index are shown in Table 2.

[0106] The preparation method of the above-mentioned steel for the body of the metal packaging can comprises molten steel smelting → continuous casting → heating of the ingot → rough rolling → finishing rolling → laminar cooling → acid continuous rolling → continuous annealing → tinning, and specifically comprises the following steps:

[0107] 1. Molten steel smelting: smelting raw materials into molten steel with the above composition.

[0108] 2. Continuous casting: continuous casting speed 2.5m / min, ingot thickness 170mm, ingot width 1100mm, ingot length 9500mm.

[0109] 3. Billet heating → rough rolling → finishing rolling → laminar cooling: the billet is hot charged into the furnace, the furnace entry temperature is 957°C, the heating time is 177min, the furnace exit temperature is 1120°C, the hot rolling and rough rolling adopts two-stand R1+R2=3+3 mode, R1 adopts 3 rolling passes, R2 adopts 3 rolling passes, the outlet temperature of R2 rough rolling is 954°C, the thickness of the intermediate billet obtained by rough rolling is 32mm, the finishing rolling inlet temperature is 875°C, the finishing rolling outlet temperature is 800°C, the total finishing reduction rate is 91.6%, and the laminar cooling outlet temperature is 588°C.

[0110] 4. Acid continuous rolling: the temperature of the hot-rolled raw material before pickling is less than 45°C, the pickling medium is a hydrochloric acid solution with a concentration of 30-200g / L, the temperature of the hydrochloric acid solution is 85°C, and after pickling, a rinsing liquid is used to remove the hydrochloric acid solution on the surface of the steel. The temperature of the rinsing liquid is 83°C, the pH value of the outlet tank rinsing water is greater than 6.0, the conductivity of the outlet tank rinsing water is ≤30μS / cm, and the total cold rolling reduction is 87.0%.

[0111] 5. Continuous annealing: The steel strip obtained by acid continuous rolling is sent to the continuous annealing furnace (steel strip speed 589m / min), and is processed through the annealing section, controlled cooling section and flattening section.

[0112] The continuous annealing furnace has a heating section length of 470m, a heat preservation section length of 300m, a rapid cooling section length of 14m, a radiation tube cooling section length of 635m, and a jet cooling section length of 164m.

[0113] In the annealing stage, the heating rate of the heating stage is 13.35°C / s, and the uniform heating temperature of the holding stage is 644°C.

[0114] During controlled cooling, the rapid cooling rate was 115.00°C / s, the radiation cooling rate was 0.77°C / s, and the jet cooling rate was 1.80°C / s.

[0115] The leveling section adopts two-frame leveling, the surface roughness Ra of the leveling machine working roll is 1.1~1.8μm, and the peak count Rpc of the roll surface roughness is 130~170cm -1 , flattening elongation 2.0%, flattening tension 87kN.

[0116] Tin plating: The steel strip obtained by continuous annealing (steel strip speed 370m / min) is electroplated, soft-melted and passivated.

[0117] In the electroplating process, the electroplating solution is a 135 g / L MSA plating solution, wherein the free acid concentration is 40 mL / L, and the Sn content in the solution is 2+ The ion concentration is 28g / L, and the tin coating amount on one side is 0.8g / m 2 The soft melting temperature is 263℃, and the passivation solution is 17g / L sodium dichromate solution, pH value is 4.3, and the passivation temperature is 40℃.

[0118] The thickness of the obtained steel product for the metal packaging can body is 0.35 mm. The inclusions, mechanical properties and surface conditions are shown in Tables 3 and 4.

[0119] Example 4

[0120] The present embodiment provides a steel for a metal packaging can body, wherein the chemical composition and mass percentage of the steel matrix are C: 0.059%, Si: 0.038%, Mn: 0.57%, P: 0.058%, S: 0.0011%, Cu: 0.41%, Ln=Ce+Pr+Nd (the mass ratio of Ce, Pr, Nd is 4:2:1): 0.013%, Al: 0.032%, V: 0.026%, Ti: 0.018%, O: 0.0012%, N: 0.0011%, and the remainder is Fe and unavoidable impurities, as shown in Table 1.

[0121] The deterioration index, comprehensive weathering index and strengthening index are shown in Table 2.

[0122] The preparation method of the steel for the metal packaging can body in this embodiment is the same as that in Example 1.

[0123] Among them, inclusions, mechanical properties and surface conditions are shown in Tables 3 and 4.

[0124] Comparative Example 1

[0125] This comparative example provides a steel for a metal packaging can body, without adding Ln element, and its chemical composition and mass percentage are C: 0.058%, Si: 0.037%, Mn: 0.58%, P: 0.051%, S: 0.0023%, Cu: 0.37%, Al: 0.039%, V: 0.027%, Ti: 0.018%, O: 0.0028%, N: 0.0037%, and the balance is Fe and unavoidable impurities, as shown in Table 1.

[0126] The values ​​of the deterioration index, comprehensive weathering index and strengthening index are shown in Table 2.

[0127] The preparation method of the above-mentioned steel for the metal packaging can body is the same as that in Example 1.

[0128] Among them, inclusions, mechanical properties and surface conditions are shown in Tables 3 and 4.

[0129] Comparative Example 2

[0130] The present comparative example provides a steel for a metal packaging can body, the chemical composition and mass percentage of which are C: 0.060%, Si: 0.039%, Mn: 0.57%, P: 0.052%, S: 0.0028%, Cu: 0.36%, Ln=Ce+Pr+Nd: 0.011% (the mass ratio of Ce, Pr, Nd is 5:3:1), Al: 0.018%, V: 0.028%, Ti: 0.017%, O: 0.0029%, N: 0.0039%, and the remainder is Fe and unavoidable impurities, as shown in Table 1.

[0131] The values ​​of the deterioration index, comprehensive weathering index and strengthening index are shown in Table 2.

[0132] The preparation method of the above-mentioned steel for the metal packaging can body is the same as that in Example 1.

[0133] Among them, inclusions, mechanical properties and surface conditions are shown in Tables 3 and 4.

[0134] Table 1 Chemical composition of steel used for metal packaging cans in embodiments and comparative examples

[0135]

[0136] Table 2 Deterioration index, comprehensive weathering index and strengthening index of the embodiments and comparative examples

[0137] <![CDATA[M Ln ]]> <![CDATA[I M ]]> <![CDATA[S (Ln+V+Ti) ]]> Example 1 0.33 15.84 6.88 Example 2 0.34 16.25 6.42 Example 3 0.27 15.57 5.76 Example 4 0.31 15.89 6.94 Comparative Example 1 0.00 5.99 1.96 Comparative Example 2 0.23 15.26 2.31

[0138] It can be seen from Table 2 that the comprehensive weathering index I in Comparative Example 1 is M It is 5.99, which is much lower than the value in the embodiment, and its corrosion resistance is poor.

[0139] Table 3: Inclusions in steel used for metal packaging cans in examples and comparative examples

[0140]

[0141] From the data of comparative example 1, it can be seen that when no rare earth element is added, that is, the modification index is 0, and there is no modification effect of Ln element, the size and number of inclusions in the steel used for the body of the metal packaging can increase significantly, with an average size of 2.3μm and a density of inclusions ≥5.0μm of 0.446 / mm 2 , the density of inclusions with a size of ≥1.0μm is 19 / mm 2 , inclusion control is difficult.

[0142] The mechanical properties and surface conditions of the steels obtained in the embodiments and comparative examples were tested:

[0143] The yield strength, tensile strength and elongation A50 were tested according to GB / T 228.1, the hardness HR30T was tested according to GB / T230.1, and the surface Ra and Rpc were tested according to GB / T 2523. The test results are shown in Table 4.

[0144] Table 4 Mechanical properties and surface conditions of steel used for metal packaging cans in examples and comparative examples

[0145]

[0146] From the data of Comparative Examples 1 and 2, it can be seen that the strengthening index S (Ln+V+Ti) When the value is lower than 5.50-7.00, the mechanical properties and surface condition thereof are poorer than those of the embodiment, and the strengthening effect is poorer. The mechanical properties do not meet the steel material use standard.

[0147] The component system and production process of Examples 1 to 4 of the present invention can stably produce steel for metal packaging can bodies with a thickness of 0.15 to 0.50 mm, and the product performance meets the yield strength Rp 0.2 : 410~510MPa, tensile strength Rm: 450~530MPa, elongation A50: ≥28%, hardness HR30T: 68~73, board surface roughness Ra: 0.3~0.8μm, board surface roughness peak count Rpc: 110~150cm -1 , average inclusion size: ≤1.3μm, size ≥5.0μm inclusion density: ≤0.03 pieces / mm 2 , size ≥ 1.0μm inclusion density: ≤ 15 pieces / mm 2 , the metallographic structure is ferrite + cementite (the metallographic structure of Example 1 is as follows Figure 1 The product has good pressure resistance and comprehensive weather resistance index I M>14, good corrosion resistance, surface quality meets customer needs, realizes low-temperature and low-load rolling production of steel for metal packaging can bodies, saves energy and reduces costs as a whole, has considerable social and economic benefits, and belongs to the category of low-energy green manufacturing process.

[0148] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A steel for a metal packaging can body, characterized in that: The invention comprises a steel matrix, wherein the chemical composition of the steel matrix comprises, by mass percentage, C: 0.056-0.075%, Si: 0.036-0.045%, Mn: 0.56-0.65%, P: 0.051-0.060%, S: ≤0.0030%, Cu: 0.36-0.45%, Ln: 0.012-0.015%, Al: 0.010-0.040%, V: 0.026-0.035%, Ti: 0.016-0.025%, O: ≤0.0030%, N: ≤0.0040%, and the rest are iron elements and unavoidable impurity elements; Deterioration index M Ln =Ln / [7.8(O)+3.46(S)+0.89(Al)]=0.2~0.6; Comprehensive weather resistance index I M =[26.01(Cu)+1.49(Si)+17.28(P)-33.39(Cu) 2 ]+38.73(Ln) 0.317 ≥14; Strengthening Index S (Ln+V+Ti) =[1.23(Ln)+1.06(V)+(Ti)] / [3.42(N)+1.5(O)+3.0(S)]=5.50~7.

00.

2. The steel for metal packaging can body according to claim 1, characterized in that: Also included is a tin coating on at least one side of the steel substrate; Preferably, the single-sided tin coating amount is 0.5 to 0.8 g / m 2 ; Preferably, the thickness of the steel used for the body of the metal packaging can is 0.15-0.50 mm.

3. The steel for metal packaging can body according to claim 1, characterized in that: The Ln includes: Ce, Pr, Nd, and the mass ratio is (4-5): (2-3):

1.

4. A method for preparing the steel for the metal packaging can body according to any one of claims 1 to 3, characterized in that: It includes molten steel smelting → continuous casting → ingot heating → rough rolling → finishing rolling → laminar cooling → acid continuous rolling → continuous annealing → tinning.

5. The method for preparing steel for metal packaging can body according to claim 4, characterized in that: The continuous casting pulling speed is 2.0-2.5 m / min, the thickness of the ingot is 150-170 mm, the width of the ingot is ≤1200 mm, and the length of the ingot is 9500-11500 mm.

6. The method for preparing the steel for the metal packaging can body according to claim 4, characterized in that: The heating of the ingot includes hot charging the ingot into a furnace, wherein the ingot temperature is ≥900°C, the heating time is ≥150min, and the out-of-furnace temperature is 1080-1120°C.

7. The method for preparing steel for metal packaging can body according to claim 4, characterized in that: The outlet temperature of the rough rolling is 925-965°C, and the thickness of the intermediate billet obtained by the rough rolling is 30-33 mm; and / or The inlet temperature of the finishing rolling is 845-885°C, the outlet temperature of the finishing rolling is 760-800°C, and the total reduction rate of the finishing rolling is 85.5%-93.9%; and / or The outlet temperature of the laminar cooling is 560-600°C.

8. The method for preparing steel for metal packaging can body according to claim 4, characterized in that: The pickling continuous rolling includes pickling and cold rolling: Preferably, the temperature of the steel before pickling is less than 45°C, the pickling medium is a hydrochloric acid solution with a concentration of 30 to 200 g / L, and the temperature of the hydrochloric acid solution is 85 to 95°C; Preferably, the total reduction ratio of the cold rolling is 75.0% to 94.4%.

9. The method for preparing steel for metal packaging can body according to claim 8, characterized in that: The continuous annealing comprises: processing the cold-rolled steel strip through an annealing section, a controlled cooling section and a flattening section; Preferably, the speed of the steel belt is 560-600 m / min; Preferably, the annealing section includes a heating section and a heat preservation section in sequence; Preferably, the heating rate of the heating section is 12.02-13.73°C / s, and the soaking temperature of the insulation section is 610-650°C; Preferably, the controlled cooling section includes a quick cooling section, a radiation tube cooling section, and a jet cooling section in sequence; Preferably, the rapid cooling rate is 86.67-121.43°C / s, the radiation cooling rate is 0.73-0.79°C / s, and the jet cooling rate is 1.71-1.83°C / s; Preferably, the flattening elongation of the flattening section is 1.7% to 2.1%, and the flattening tension is 85 to 90 kN.

10. The method for preparing steel for metal packaging can body according to claim 4, characterized in that: The tinning comprises: electroplating, reflowing and passivating the steel strip obtained by continuous annealing; Preferably, the speed of the steel belt is 320-380 m / min; Preferably, the electroplating solution is a MSA plating solution with a concentration of 125 to 135 g / L, wherein the free acid concentration is 30 to 45 mL / L, and the Sn content in the solution is 2+ Ion concentration is 10-40 g / L; Preferably, the reflow temperature of the reflow is 258-263°C; Preferably, the passivation uses a sodium dichromate solution with a concentration of 13 to 18 g / L as the passivation solution, a pH value of 4.0 to 4.3, and a passivation temperature of 40 to 45°C.

Images