Steel for easy-to-open lid and preparation method thereof

Abstract

The invention discloses steel for an easy-to-open lid and a preparation method of the steel, and belongs to the technical field of metallurgy, and the steel for the easy-to-open lid comprises a steel base material and a tin plating layer arranged on at least one side of the steel base material; the steel base material comprises the following chemical components in percentage by mass: 0.046%-0.055% of C, 0.018%-0.028% of Si, 0.46%-0.55% of Mn, less than or equal to 0.015% of P, less than or equal to 0.0030% of S, 0.026%-0.035% of Mo, 0.004%-0.009% of Ln, 0.010%-0.040% of Al, 0.030%-0.040% 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 the adoption of the component system, the product forming performance, surface quality and pressure bearing performance are good.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to steel for easy-open lids and a preparation method thereof. Background Art

[0002] Easy-open end is a metal packaging can cover with a pre-marked deep notch and riveted with a pull ring. When opening the can cover, the cover is torn off along the notch line. This can cover is widely used in metal packaging products such as food cans, beverage cans, and dry powder cans.

[0003] The thickness of steel used for easy-open ends is generally no more than 0.30mm. During riveting, the thickness of the tinplate used for easy-open ends is reduced by more than 50% at the deformation site, and the thickness of the steel plate at the thinning area and the notch is less than 0.10mm. At present, the inclusion control, processing formability and pressure bearing performance of steel used for easy-open ends are poor, and riveting or notch cracking is very likely to occur at the thinning area and the notch. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the prior art in which steel for easy-open ends has poor inclusion control, processing formability and pressure bearing performance, and riveting or notch cracking is very likely to occur in the thinning area and the notch, thereby providing a steel for easy-open ends 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 an easy-open end, comprising a steel substrate and a tin coating disposed on at least one side of the steel substrate;

[0007] The chemical composition of the steel substrate includes, by mass percentage:

[0008] C: 0.046-0.055%, Si: 0.018-0.028%, Mn: 0.46-0.55%, P: ≤0.015%, S: ≤0.0030%, Mo: 0.026-0.035%, Ln: 0.004-0.009%, Al: 0.010-0.040%, Ti: 0.030-0.040%, O: ≤0.0030%, N: ≤0.0040%, the rest are iron and unavoidable impurity elements; modification index M Ln =Ln / [7.8(O)+3.46(S)+0.89(Al)]=0.15~0.55, strengthening index S (Ln+Ti) =[1.23(Ln)+(Ti)] / [3.42(N)+1.5(O)+3.0(S)]=4.0~5.5.

[0009] Calculate M Ln and S (Ln+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.

[0010] Furthermore, the thickness of the steel for the easy-open end is 0.10 to 0.30 mm; preferably, the tin coating amount on one side of the steel substrate is 2.5 to 2.7 g / m 2 .

[0011] Furthermore, the Ln includes: Ce, Pr, Nd, and the mass ratio is 1:(3-4):(2-3).

[0012] 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 0.046-0.055%.

[0013] 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 Mo 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 0.018-0.028%.

[0014] 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 the steel, but also reduce the corrosion resistance of the steel and increase the manufacturing cost. Therefore, the Mn content in the present invention is controlled at 0.46-0.55%.

[0015] 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 to be ≤0.015%.

[0016] 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%.

[0017] Mo can greatly reduce the corrosion rate of steel and improve the corrosion resistance of steel. At the same time, Mo is a ferrite solid solution strengthening element, which can improve the strength of steel, reduce the problem of uneven structure during hot working, and improve the thermal stability of microalloy carbonitride. Therefore, the Mo content of the present invention is controlled at 0.026-0.035%.

[0018] Ln can improve the comprehensive properties of steel by purifying steel, modifying inclusions, and refining grains, and can also significantly improve the corrosion resistance of steel. However, if the Ln content is too high during the heat treatment of steel, 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 0.004-0.009%.

[0019] The Ln includes Ce, Pr, and Nd.

[0020] 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 effective Ti content 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%.

[0021] Ti is a strong carbonitride-forming element, which can play the role of precipitation strengthening and fine grain strengthening, reduce the anisotropy of the strip steel, and increase the formability of the steel for easy-opening caps. However, if the Ti content is too high, the size and quantity of the second phase precipitate TiN will increase, which will affect the formability of the steel plate. Therefore, the present invention controls the Ti content to 0.030-0.040%.

[0022] O and N have a strong affinity with titanium. O and Ti in the molten steel combine to form TiO2, and N and Ti combine 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 reduce 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%.

[0023] In order to ensure the modification effect of reducing, refining and spheroidizing inclusions, the chemical composition of the steel of the present invention must satisfy Ln / [7.8(O)+3.46(S)+0.89(Al)] in the range of 0.15 to 0.55, and the modification effect becomes better and better as the value increases.

[0024] In a second aspect, the preparation method of the steel for easy-opening lid of the present invention comprises molten steel smelting→continuous casting→ingot heating→rough rolling→finishing rolling→laminar cooling→acid continuous rolling→continuous annealing→tin plating.

[0025] Furthermore, the continuous casting speed is 1.8-2.3 m / min, the thickness of the ingot is 160-180 mm, the width of the ingot is ≤1000 mm, and the length of the ingot is 8500-10500 mm.

[0026] Furthermore, the heating of the ingot includes hot charging the ingot into a furnace, with the ingot entering the furnace at a temperature ≥800°C, the heating time being controlled at ≥160min, and the out-of-furnace temperature being 1085-1125°C.

[0027] Furthermore, the outlet temperature of the rough rolling is 935-975°C, and the thickness of the intermediate billet obtained by the rough rolling is 30-32 mm; the rough rolling adopts a two-stand R1+R2=1+5 mode, R1 adopts 1 pass rolling, and R2 adopts 5 passes rolling;

[0028] The inlet temperature of the finishing rolling is 855-895°C, the outlet temperature of the finishing rolling is 775-815°C, and the total reduction rate of the finishing rolling is 83.3%-93.8%;

[0029] The outlet temperature of the laminar cooling is 590-630°C.

[0030] The use of low-temperature technology to produce steel for easy-opening covers can reduce the oxidation and burning caused by high-temperature production, improve the yield rate and production efficiency; the low temperature system can reduce the temperature rise of the rolls, reduce fatigue cracking and fracture caused by thermal stress, and reduce roll consumption; the low temperature system can reduce the formation of secondary iron oxide scale, improve the surface quality of hot-rolled products, the pickling effect and efficiency of pickling, and reduce the generation of hole defects during the acid continuous rolling production process; the cold-rolled base material produced by the low-temperature process has a lower strength, which can effectively reduce the cold rolling load, save energy and reduce consumption; and the cold rolling deformation can be appropriately increased to improve production efficiency.

[0031] Furthermore, the acid continuous rolling includes pickling and cold rolling;

[0032] 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 83 to 93°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 73 to 83°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; preferably, the total reduction rate of the cold rolling is 85.0% to 96.0%.

[0033] 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;

[0034] Preferably, the speed of the steel belt is 510-550 m / min;

[0035] Preferably, the annealing section includes a heating section and a soaking section in sequence;

[0036] Preferably, the heating rate of the heating section is 11.67-13.36°C / s, and the soaking temperature is 650-690°C;

[0037] Preferably, the controlled cooling section includes a quick cooling section, a radiation tube cooling section, and a jet cooling section in sequence;

[0038] Rapid cooling rate: 103.21~137.50℃ / s, radiation tube cooling rate: 0.67~0.72℃ / s, jet cooling rate: 1.56~1.68℃ / s;

[0039] The leveling section adopts a two-frame leveling machine for leveling. The working roll surface roughness Ra of the leveling machine is 1.3-2.0 μm, and the peak count Rpc of the roll surface roughness is 140-180 cm -1 ;

[0040] Preferably, the flattening elongation of the flattening section is 1.6% to 2.0%, and the flattening tension is 80 to 85 kN.

[0041] Furthermore, the electro-tinning comprises: electroplating, reflowing and passivating the steel strip obtained by continuous annealing;

[0042] The speed of the steel belt is 350-400 m / min;

[0043] The electroplating solution is an MSA plating solution with a concentration of 80-90 g / L, wherein the free acid concentration is 30-45 mL / L, and the Sn content in the solution is 2+ Ion concentration is 5-15 g / L;

[0044] The reflow temperature of the reflow is 253-257°C;

[0045] The passivation uses a sodium dichromate solution with a concentration of 10-15 g / L as the passivation solution, a pH value of 4.0-4.3, and a passivation temperature of 38-43°C.

[0046] The technical solution of the present invention has the following advantages:

[0047] 1. The present invention provides a steel for easy-open end, comprising a steel substrate and a tin coating disposed on at least one side of the steel substrate; the chemical composition of the steel substrate includes, by mass percentage:

[0048] C: 0.046-0.055%, Si: 0.018-0.028%, Mn: 0.46-0.55%, P: ≤0.015%, S: ≤0.0030%, Mo: 0.026-0.035%, Ln: 0.004-0.009%, Al: 0.010-0.040%, Ti: 0.030-0.040%, O: ≤0.0030%, N: ≤0.0040%, the rest are iron and unavoidable impurity elements; modification index M Ln =Ln / [7.8(O)+3.46(S)+0.89(Al)]=0.15~0.55, strengthening index S (Ln+Ti) =[1.23(Ln)+(Ti)] / [3.42(N)+1.5(O)+3.0(S)]=4.0~5.5.

[0049] The steel for easy-open lids of the present invention can reduce the content of harmful elements in the steel and the segregation at the grain boundaries by adding a proper amount of Ln rare earth elements, and has the effect of purifying the steel quality; by adding a proper amount of Ln rare earth elements, the shape, size, distribution, composition, structure and type of inclusions in the steel for easy-open lids can be changed, and the inclusions can be reduced, refined and spheroidized, thereby improving the comprehensive mechanical properties of the steel for easy-open lids, reducing the generation of hole defects in the acid continuous rolling production process and the cracking phenomenon in the riveting or notching process; at the same time, through the comprehensive effect of Ln rare earth elements, Mo, Ti and other elements, the forming performance and pressure bearing performance of the steel for easy-open lids can be significantly improved.

[0050] The steel for the easy-open lid of the present invention adopts a C-Mn component system, and is micro-alloyed with Mo, Ti and Ln, and satisfies the modification index M Ln =(Ln) / [7.8(O)+3.46(S)+0.89(Al)]=0.15~0.55, strengthening index S (Ln+Ti) =[1.23(Ln)+(Ti)] / [3.42(N)+1.5(O)+3.0(S)]=4.0~5.5, which can significantly improve the comprehensive mechanical properties, performance and pressure bearing properties of steel for easy-open covers, reduce the generation of hole defects during acid continuous rolling production, and reduce riveting or notching cracking.

[0051] 2. In the preparation method of steel for easy-opening covers of the present invention, the outlet temperature of rough rolling is 935-975°C, the intermediate billet thickness is 30-32 mm; the inlet temperature of finishing rolling is 855-895°C, the outlet temperature of finishing rolling is 775-815°C, and the total reduction rate of finishing rolling is 83.3%-93.8%.

[0052] The hot rolling process of the steel for easy-opening caps of the present invention adopts a suitable low-temperature process, low-temperature heating + low-temperature rolling, so as to realize the low-temperature and low-load rolling production of rare earth steel for easy-opening caps, which is energy-saving, cost-reducing, and low-carbon, green and environmentally friendly. At the same time, the consumption of heating energy and the oxidation and burning loss of steel are reduced, and the yield rate and production efficiency are improved; low-temperature rolling can reduce fatigue cracking and fracture caused by the 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 formation of secondary iron oxide scale, improve the surface quality of hot-rolled products, and the effect and efficiency of pickling and pickling; 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 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.

[0053] 3. The hot rolling low temperature process of the present invention combines the comprehensive control of process dimensions such as the thickness of the ingot, the width of the ingot, the length of the ingot, the thickness of the intermediate ingot, the total reduction rate of hot rolling and finishing rolling, and the total reduction rate of cold rolling, which can further reduce the hot rolling and cold rolling loads and roll consumption. It can be seen that the low temperature hot rolling process combines the comprehensive control of process dimensions, saves energy, reduces costs and reduces consumption, and belongs to the category of low energy consumption green environmental protection manufacturing process.

[0054] By adopting the component system and preparation method of the present invention, steel for easy-open lids with a thickness of 0.10 to 0.30 mm can be stably produced. The product has good forming performance, surface quality and pressure bearing performance, and realizes low-temperature and low-load rolling production of steel for easy-open lids, which saves energy, reduces costs and reduces consumption as a whole, has considerable social and economic benefits, and belongs to the category of low-energy consumption green manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] 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.

[0056] Figure 1 1 is a metallographic structure morphology diagram of the steel for easy-open end in Example 1 of the present invention. DETAILED DESCRIPTION

[0057] 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.

[0058] 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.

[0059] Example 1

[0060] The present embodiment provides a steel for an easy-open end, whose chemical composition and mass percentage are C: 0.051%, Si: 0.025%, Mn: 0.48%, P: 0.014%, S: 0.0010%, Mo: 0.031%, Ln=Ce+Pr+Nd: 0.008% (the mass ratio of Ce:Pr:Nd is 1:3:2), Al: 0.035%, Ti: 0.033%, O: 0.0012%, N: 0.0013%, and the remainder is Fe and unavoidable impurities, as shown in Table 1.

[0061] The deterioration index and strengthening index are shown in Table 2.

[0062] The preparation method of the above-mentioned steel for easy-open end comprises molten steel smelting → continuous casting → heating of ingot → rough rolling → finishing rolling → laminar cooling → acid continuous rolling → continuous annealing → tinning, and specifically comprises the following steps:

[0063] 1. Molten steel smelting: smelting raw materials into molten steel with the above composition.

[0064] 2. Continuous casting: continuous casting speed 2.2m / min, ingot thickness 160mm, ingot width 1000mm, ingot length 10000mm.

[0065] 3. Billet heating → rough rolling → finishing rolling → laminar cooling: the billet is hot loaded into the furnace, the furnace entry temperature is 813°C, the heating time is 165min, the furnace exit temperature is 1120°C, the rough rolling adopts two-stand R1+R2=1+5 mode, R1 adopts 1 pass rolling, R2 adopts 5 passes rolling, the outlet temperature of R2 for rough rolling is 955°C, the thickness of the intermediate billet obtained by rough rolling is 30mm, the inlet temperature of finishing rolling is 885°C, the outlet temperature of finishing rolling is 794°C, the total reduction rate of finishing rolling is 93.3%, and the laminar cooling outlet temperature is 615°C.

[0066] 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 88°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 75°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 reduction rate of cold rolling is 92.5%.

[0067] 5. Continuous annealing: The steel strip obtained by acid continuous rolling is sent to the continuous annealing furnace (steel strip speed 532m / min), and is processed through the annealing section, controlled cooling section and flattening section.

[0068] The continuous annealing furnace has a heating section length of 470m, a soaking 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.

[0069] In the annealing stage, the heating rate of the heating section is 12.68°C / s, and the soaking temperature is 677°C.

[0070] During controlled cooling, the rapid cooling rate was 124.77°C / s, the radiation tube cooling rate was 0.70°C / s, and the jet cooling rate was 1.63°C / s.

[0071] The leveling section adopts two-frame leveling, the surface roughness Ra of the leveling machine working roll is 1.3~2.0μm, and the peak count Rpc of the roll surface roughness is 140~180cm -1 , flattening elongation 1.9%, flattening tension 83kN.

[0072] 6. Tin plating: The steel strip obtained by continuous annealing (steel strip speed 385m / min) is electroplated, soft-melted and passivated.

[0073] During electroplating, the electroplating solution is an MSA plating solution with a concentration of 89 g / L, wherein the free acid concentration is 44 mL / L, and the Sn content in the solution is 2+ The ion concentration is 15g / L, and the single-sided tin coating amount is 2.6g / m 2 ;

[0074] The reflow temperature of the reflow is 255°C, and the passivation solution is a 15g / L sodium dichromate solution with a pH value of 4.1 and a passivation temperature of 40°C.

[0075] The thickness of the obtained steel product for easy-open ends is 0.15 mm. The inclusion conditions, mechanical properties and surface conditions are shown in Tables 3 and 4.

[0076] The steel for easy-open end obtained in this embodiment was observed under a 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.

[0077] Example 2

[0078] The present embodiment provides a steel for an easy-open end, whose chemical composition and mass percentage are C: 0.049%, Si: 0.027%, Mn: 0.47%, P: 0.015%, S: 0.0013%, Mo: 0.033%, Ln=Ce+Pr+Nd: 0.009% (the mass ratio of Ce:Pr:Nd is 1:3:3), Al: 0.019%, Ti: 0.035%, O: 0.0011%, N: 0.0010%, and the remainder is Fe and unavoidable impurities, as shown in Table 1.

[0079] The deterioration index and strengthening index are shown in Table 2.

[0080] The preparation method of the above-mentioned steel for easy-open end comprises molten steel smelting → continuous casting → heating of ingot → rough rolling → finishing rolling → laminar cooling → acid continuous rolling → continuous annealing → tinning, and specifically comprises the following steps:

[0081] 1. Molten steel smelting: smelting raw materials into molten steel with the above composition.

[0082] 2. Continuous casting: continuous casting speed 2.2m / min, ingot thickness 160mm, ingot width 1000mm, ingot length 9500mm.

[0083] 3. Billet heating → rough rolling → finishing rolling → laminar cooling: the billet is hot loaded into the furnace, the furnace entry temperature is 825°C, the heating time is 170min, the furnace exit temperature is 1123°C, the rough rolling adopts two-stand R1+R2=1+5 mode, R1 adopts 1 pass rolling, R2 adopts 5 passes rolling, the outlet temperature of R2 for rough rolling is 967°C, the thickness of the intermediate billet obtained by rough rolling is 31mm, the inlet temperature of finishing rolling is 891°C, the outlet temperature of finishing rolling is 799°C, the total reduction rate of finishing rolling is 93.5%, and the laminar cooling outlet temperature is 614°C.

[0084] 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 86°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 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 reduction rate of cold rolling is 91.0%.

[0085] 5. Continuous annealing: The steel strip obtained by acid continuous rolling is sent to the continuous annealing furnace (steel strip speed 537m / min), and is processed through the annealing section, controlled cooling section and flattening section.

[0086] The continuous annealing furnace has a heating section length of 470m, a soaking 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.

[0087] In the annealing stage, the heating rate of the heating section is 12.95°C / s, and the soaking temperature is 685°C.

[0088] During controlled cooling, the rapid cooling rate was 131.05°C / s, the radiation tube cooling rate was 0.70°C / s, and the jet cooling rate was 1.64°C / s.

[0089] The leveling section adopts two-frame leveling, the surface roughness Ra of the leveling machine working roll is 1.3~2.0μm, and the peak count Rpc of the roll surface roughness is 140~180cm -1 , flattening elongation 1.8%, flattening tension 81kN.

[0090] 6. Tin plating: The steel strip obtained by continuous annealing (steel strip speed 388m / min) is electroplated, soft-melted and passivated.

[0091] During electroplating, the electroplating solution is an MSA plating solution with a concentration of 83 g / L, in which the free acid concentration is 38 mL / L and the Sn content in the solution is 2+ The ion concentration is 10g / L, and the single-sided tin coating amount is 2.6g / m 2 ;

[0092] The reflow temperature of the reflow is 257°C, and the passivation solution is a sodium dichromate solution with a concentration of 13g / L, a pH value of 4.1, and a passivation temperature of 39°C. The thickness of the obtained steel product for easy-opening caps is 0.18mm, and the mechanical properties, surface and inclusions are shown in Tables 3 and 4.

[0093] Example 3

[0094] The present embodiment provides a steel for an easy-open end, whose chemical composition and mass percentage are C: 0.053%, Si: 0.023%, Mn: 0.51%, P: 0.012%, S: 0.0011%, Mo: 0.029%, Ln=Ce+Pr+Nd: 0.008% (the mass ratio of Ce:Pr:Nd is 1:4:2), Al: 0.027%, Ti: 0.032%, O: 0.0015%, N: 0.0011%, and the remainder is Fe and unavoidable impurities, as shown in Table 1.

[0095] The deterioration index and strengthening index are shown in Table 2.

[0096] The preparation method of the above-mentioned steel for easy-open end comprises molten steel smelting → continuous casting → heating of ingot → rough rolling → finishing rolling → laminar cooling → acid continuous rolling → continuous annealing → tinning, and specifically comprises the following steps:

[0097] 1. Molten steel smelting: smelting raw materials into molten steel with the above composition.

[0098] 2. Continuous casting: continuous casting speed 2.2m / min, ingot thickness 170mm, ingot width 1000mm, ingot length 9000mm.

[0099] 3. Billet heating → rough rolling → finishing rolling → laminar cooling: the billet is hot charged into the furnace, the furnace entry temperature is 873°C, the heating time is 163min, the furnace exit temperature is 1125°C, the rough rolling adopts two-stand R1+R2=1+5 mode, R1 adopts 1 pass rolling, R2 adopts 5 passes rolling, the outlet temperature of R2 for rough rolling is 958°C, the thickness of the intermediate billet obtained by rough rolling is 32mm, the inlet temperature of finishing rolling is 875°C, the outlet temperature of finishing rolling is 803°C, the total reduction rate of finishing rolling is 93.8%, and the laminar cooling outlet temperature is 619°C.

[0100] 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 90°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 73°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 reduction rate of cold rolling is 90.0%.

[0101] 5. Continuous annealing: The steel strip obtained by acid continuous rolling is sent to the continuous annealing furnace (steel strip speed 539m / min), and is processed through the annealing section, controlled cooling section and flattening section.

[0102] The continuous annealing furnace has a heating section length of 470m, a soaking 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.

[0103] In the annealing stage, the heating rate of the heating section is 12.88°C / s, and the soaking temperature is 679°C.

[0104] During controlled cooling, the rapid cooling rate was 127.69°C / s, the radiation tube cooling rate was 0.71°C / s, and the jet cooling rate was 1.65°C / s.

[0105] The leveling section adopts two-frame leveling, the surface roughness Ra of the leveling machine working roll is 1.3~2.0μm, and the peak count Rpc of the roll surface roughness is 140~180cm -1 , flattening elongation 2.0%, flattening tension 84kN.

[0106] 6. Tin plating: The steel strip obtained by continuous annealing (steel strip speed 373m / min) is electroplated, soft-melted and passivated.

[0107] In the electroplating process, the electroplating solution is an MSA plating solution with a concentration of 85 g / L, wherein the free acid concentration is 40 mL / L, and the Sn content in the solution is 2+ The ion concentration is 13g / L, and the single-sided tin coating amount is 2.6g / m 2 ;

[0108] The reflow temperature of the reflow is 253°C, and the passivation solution is a sodium dichromate solution with a concentration of 14g / L, a pH value of 4.1, and a passivation temperature of 41°C. The thickness of the obtained steel product for easy-opening lids is 0.20mm, and the inclusions, mechanical properties, and surface conditions are shown in Tables 3 and 4.

[0109] Example 4

[0110] The present embodiment provides a steel for an easy-open end, whose chemical composition and mass percentage are C: 0.050%, Si: 0.023%, Mn: 0.49%, P: 0.013%, S: 0.0013%, Mo: 0.030%, Ln=Ce+Pr+Nd: 0.008% (the mass ratio of Ce:Pr:Nd is 1:4:3), Al: 0.028%, Ti: 0.035%, O: 0.0013%, N: 0.0010%, and the remainder is Fe and unavoidable impurities, as shown in Table 1.

[0111] The deterioration index and strengthening index are shown in Table 2.

[0112] The preparation method of the above-mentioned steel for easy-open end is the same as that in Example 1.

[0113] The inclusion conditions, mechanical properties and surface conditions are shown in Tables 3 and 4.

[0114] Comparative Example 1

[0115] This comparative example provides a steel for an easy-open lid, without adding Ln element, and its chemical composition and mass percentage are C: 0.048%, Si: 0.020%, Mn: 0.49%, P: 0.013%, S: 0.0015%, Mo: 0.028%, Al: 0.033%, Ti: 0.031%, O: 0.0027%, N: 0.0035%, and the balance is Fe and unavoidable impurities, as shown in Table 1.

[0116] The deterioration index and strengthening index are shown in Table 2.

[0117] The preparation method of the above-mentioned steel for easy-open ends is the same as that in Example 1, and the thickness of the obtained steel product for easy-open ends is 0.15 mm.

[0118] The inclusion conditions, mechanical properties and surface conditions are shown in Tables 3 and 4.

[0119] Comparative Example 2

[0120] The present comparative example provides a steel for an easy-open lid, whose chemical composition and mass percentage are C: 0.049%, Si: 0.019%, Mn: 0.50%, P: 0.015%, S: 0.0025%, Mo: 0.033%, Ln=Ce+Pr+Nd: 0.009% (the mass ratio of Ce:Pr:Nd is 1:3:2), Al: 0.039%, Ti: 0.030%, O: 0.0028%, N: 0.0037%, and the remainder is Fe and unavoidable impurities, as shown in Table 1.

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

[0122] The preparation method of the above-mentioned steel for easy-open ends is the same as that in Example 1, and the thickness of the obtained steel product for easy-open ends is 0.15 mm.

[0123] The inclusion conditions, mechanical properties and surface conditions are shown in Tables 3 and 4.

[0124] Table 1 Chemical composition of steel for easy-open end in embodiments and comparative examples

[0125]

[0126] Table 2 Deterioration index and strengthening index of examples and comparative examples

[0127] <![CDATA[M Ln ]]> <![CDATA[S (LnTi) ]]> Example 1 0.18 4.63 Example 2 0.30 5.14 Example 3 0.20 4.49 Example 4 0.20 4.84 Comparative Example 1 0.00 1.51 Comparative Example 2 0.14 1.69

[0128] Table 3 Inclusions in steel for easy-open lids of examples and comparative examples

[0129]

[0130]

[0131] From the data of Comparative Example 1, it can be seen that without adding rare earth elements, the deterioration index M Ln = 0, without the modification effect of Ln element, the size and number of inclusions in the steel for easy-opening cover increased significantly. The average size of inclusions was 2.50 μm, and the density of inclusions with a size of ≥ 5.0 μm was 0.5 / mm 2 , the density of inclusions with a size of ≥1.0μm is 21 / mm 2 , inclusion control is more difficult. From the data of comparative example 2, it can be seen that when the metamorphic index M Ln When it is not in the range of 0.15-0.55, the modification effect is poor and it is difficult to control the inclusion situation in the steel.

[0132] The yield strength, tensile strength and elongation A50 are tested according to GB / T 228.1, the tensile strain hardening index (n value) is tested according to GB / T 5028, the anisotropy |Δr| is tested according to GB / T 5027, the hardness HR30T is tested according to GB / T230.1, and the surface roughness and peak number are tested according to GB / T 2523.

[0133] Table 4 Mechanical properties and surface conditions of steel for easy-open lids in embodiments and comparative examples

[0134]

[0135] It can be seen from Table 4 that when the deterioration index M is satisfied Ln =0.15~0.55; Strengthening index S (Ln+Ti)=4.0~5.5, the mechanical properties and surface condition of the steel for easy-open lid are excellent: |Δr|≤0.15, the formability of the steel in all directions is relatively good, and the elongation A50 is high, the formability r is high, the processing performance of the steel of the present invention is good, and the processing formability and pressure bearing performance of the steel for easy-open lid are poor, and the thinning area and the notch are very prone to riveting or notch cracking. It can be seen from the data of comparative example 2 that when the strengthening index S (Ln+Ti) When it is not in the range of 4.0 to 5.5, the yield strength, elongation A50, n value, r value, HR30T and surface roughness of the steel for easy-open ends do not meet the use standards of steel materials, its strengthening effect is poor, and it does not have excellent formability and resistance to notch cracking.

[0136] The component system and production process of embodiments 1 to 4 of the present invention can stably produce steel for easy-opening lids with a thickness of 0.10 to 0.30 mm, and the product performance meets the following requirements: yield strength Rp0.2: 320 to 390 MPa, tensile strength Rm: 400 to 470 MPa, elongation A50: ≥38%, work hardening index n: ≥0.195, plastic strain ratio r: ≥1.95, anisotropy |Δr|: ≤0.15, hardness HR30T: 65 to 70, surface roughness Ra: 0.4 to 0.9 μm, plate surface roughness peak count Rpc: 120 to 160 cm -1 , average inclusion size: ≤1.0μm, size ≥5.0μm inclusion density: ≤0.01 / mm 2 , size ≥ 1.0μm inclusion density: ≤ 10 / mm 2 , the metallographic structure is ferrite + cementite (such as Figure 1 The product has good forming performance and pressure-bearing performance, and the surface quality meets customer needs. It realizes low-temperature and low-load rolling production of steel for easy-open covers, 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.

[0137] 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 easy-open end, characterized in that: It comprises a steel substrate and a tin coating disposed on at least one side of the steel substrate; The chemical composition of the steel substrate includes, by mass percentage: C: 0.046-0.055%, Si: 0.018-0.028%, Mn: 0.46-0.55%, P: ≤0.015%, S: ≤0.0030%, Mo: 0.026-0.035%, Ln: 0.004-0.009%, Al: 0.010-0.040%, Ti: 0.030-0.040%, O: ≤0.0030%, N: ≤0.0040%, the rest are iron and unavoidable impurity elements; Deterioration index M Ln =Ln / [7.8(O)+3.46(S)+0.89(Al)]=0.15~0.55; Strengthening Index S (Ln+Ti) =[1.23(Ln)+(Ti)] / [3.42(N)+1.5(O)+3.0(S)]=4.0~5.

5.

2. The steel for easy-open ends according to claim 1, characterized in that: The thickness of the steel for the easy-open end is 0.10 to 0.30 mm; Preferably, the tin coating amount on one side of the steel substrate is 2.5 to 2.7 g / m 2 .

3. The steel for easy-open ends according to claim 1, characterized in that: The Ln includes: Ce, Pr, Nd, and the mass ratio is 1: (3-4): (2-3).

4. A method for preparing the steel for easy-open end 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 easy-open ends according to claim 4, characterized in that: The continuous casting pulling speed is 1.8-2.3 m / min, the casting billet thickness is 160-180 mm, the casting billet width is ≤1000 mm, and the casting billet length is 8500-10500 mm.

6. The method for preparing steel for easy-open ends according to claim 4, characterized in that: The heating of the ingot includes hot charging the ingot into a furnace, wherein the ingot entering the furnace is ≥800°C, the heating time is controlled at ≥160min, and the out-of-furnace temperature is 1085-1125°C.

7. The method for preparing steel for easy-open ends according to claim 4, characterized in that: The outlet temperature of the rough rolling is 935-975°C, and the thickness of the intermediate billet obtained by the rough rolling is 30-32 mm; and / or The inlet temperature of the finishing rolling is 855-895°C, the outlet temperature of the finishing rolling is 775-815°C, and the total reduction rate of the finishing rolling is 83.3%-93.8%; and / or The outlet temperature of the laminar cooling is 590-630°C.

8. The method for preparing steel for easy-open ends 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 83 to 93°C; Preferably, the total reduction ratio of the cold rolling is 85.0% to 96.0%.

9. The method for preparing steel for easy-open ends according to claim 8, characterized in that: The continuous annealing comprises: processing the steel strip obtained by cold rolling through an annealing section, a controlled cooling section and a flattening section; Preferably, the speed of the steel belt is 510-550 m / min; Preferably, the annealing section includes a heating section and a soaking section in sequence; Preferably, the heating rate of the heating section is 11.67-13.36°C / s, and the soaking temperature is 650-690°C; Preferably, the controlled cooling section includes a quick cooling section, a radiation tube cooling section, and a jet cooling section in sequence; Rapid cooling rate: 103.21~137.50℃ / s, radiation tube cooling rate: 0.67~0.72℃ / s, jet cooling rate: 1.56~1.68℃ / s; Preferably, the flattening elongation of the flattening section is 1.6% to 2.0%, and the flattening tension is 80 to 85 kN.

10. The method for preparing steel for easy-open ends 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 350-400 m / min; Preferably, the electroplating solution is a MSA plating solution with a concentration of 80 to 90 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 5-15 g / L; Preferably, the reflow temperature of the reflow is 253-257°C; Preferably, the passivation uses a sodium dichromate solution with a concentration of 10 to 15 g / L as the passivation solution, a pH value of 4.0 to 4.3, and a passivation temperature of 38 to 43°C.

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