Low-cost anti-aging tinned steel strip and production method thereof

Abstract

The invention discloses a low-cost anti-aging tin-plated steel strip and a production method thereof. The steel strip comprises the following chemical components in percentage by mass: 0.020-0.040% of C, less than or equal to 0.05% of Si, 020-0.30% of Mn, less than or equal to 0.024% of P, less than or equal to 0.016% of S, 0.025-0.055% of Al, less than or equal to 0.0040% of N, less than or equal to 0.010% of As, 0.0010-0.0080% of B, less than or equal to 0.0035% of T [O] and the balance of iron and inevitable impurities. The production method comprises the working procedures of smelting, RH refining, continuous casting, hot rolling, acid pickling and cold rolling, continuous annealing, leveling and tin plating. The tin-plated steel strip provided by the invention is excellent in performance, aging resistance and punch forming performance, can meet long-term storage and long-range turnover use of downstream customers of tin-plated plates, and reduces the quality problem rate generated in the part machining process due to aging.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical production, and in particular relates to a low-cost anti-aging tin-plated steel strip and a production method thereof. Background Art

[0002] Tin-plated substrates are non-toxic and harmless, making them safe for food packaging. The tin layer itself has excellent corrosion resistance, protecting the substrate from corrosion and meeting the corrosion resistance requirements of different contents. It can be printed with various coatings and inks to enhance its protective properties and manufactured into various sales packaging products. It has good welding performance and can be used for brazing or hot-melt welding to manufacture a variety of containers. It has good ductility, lubricity, and good processing performance, meeting processing requirements and strength requirements after processing.

[0003] Micro-carbon steel is a typical, economical and practical deep-drawing steel currently in use. It is developed on the basis of traditional low-carbon aluminum-killed deep-drawing steel by further reducing carbon and purifying steel. However, for tinplate with micro-carbon steel composition, due to the continuous annealing process of the substrate, a certain amount of solid-solution carbon and nitrogen in the steel body is retained in the annealed finished product. After a long period of storage, the solid-solution carbon and nitrogen atoms in the steel gather around the dislocations, resulting in increased steel strength and increased difficulty in stamping. Slip line defects are easily generated during the stamping process, and defects such as steel body wrinkles and tensile strain marks are also prone to occur, which seriously affect the subsequent processing and forming performance and coating effects, and cause aging phenomena. If the aging index AI is greater than 30MPa, the product is prone to stamping orange peel or cracking defects during subsequent stamping, thereby affecting product quality and making it unusable.

[0004] Patent application with publication number CN 107964633A discloses an aging-resistant tin-plated substrate and a manufacturing method thereof. Its chemical composition is C <0.005%, Si <0.04%, Mn: 0.3%~0.5%, P: 0.05%~0.08%, S <0.02%, Alt: 0.01%~0.06%, N ≤0.005%, Ti: 0.04%~0.08%, and the balance is iron and unavoidable inclusions; it uses ultra-low carbon and adds Ti alloy components, and the production cost is relatively high. Summary of the Invention

[0005] The object of the present invention is to provide a low-cost aging-resistant tin-plated steel strip and a production method thereof.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A low-cost aging-resistant tin-plated steel strip is prepared from the following raw materials in percentage by mass: C: 0.020-0.040%, Si: ≤0.04%, Mn: 0.20-0.30%, P: ≤0.024%, S: ≤0.016%, Al: 0.025-0.055%, N: ≤0.0040%, As≤0.010%, B: 0.0010-0.0080%, T[O]≤0.0035%, and the remainder is iron and unavoidable impurities.

[0007] Furthermore, the thickness of the low-cost aging-resistant tin-plated steel strip of the present invention is 0.15 to 1.20 mm.

[0008] Furthermore, the low-cost anti-aging tinned steel strip of the present invention has a yield strength of 210-260 MPa, a tensile strength of 330-390 MPa, and an elongation of A 50 ≥32%.

[0009] The production method of the low-cost aging-resistant tin-plated steel strip of the present invention comprises smelting, RH refining, continuous casting, hot rolling, pickling and cold rolling, continuous annealing, flattening and tinning processes.

[0010] Furthermore, in the refining process of the present invention, the outlet temperature of the converter smelting is controlled at 1620-1640°C, the net cycle time of the RH refining is greater than 8 minutes, the composition meets the target requirements of the finished product, and the outlet temperature is controlled at 1585-1600°C.

[0011] Furthermore, the hot rolling process of the present invention is as follows: the continuous casting slab is heated to 1200-1250°C, and the slab is heated in the furnace for 140-220 minutes; the rough rolling temperature is 1030-1090°C; the finishing rolling entrance temperature is 1010-1050°C, and the finishing rolling final temperature is 850-910°C; the coiling temperature is 590-630°C, and the cooling method adopts the post-stage cooling process.

[0012] Furthermore, the cold rolling process of the present invention is as follows: the hot-rolled steel strip is pickled and then rolled in a cold rolling mill, the cold rolling mill adopts a single-stand rolling mill, and the total reduction rate of each pass is 82-90%.

[0013] Furthermore, the continuous annealing process of the present invention is as follows: the cold-rolled steel strip enters a continuous annealing furnace for annealing treatment, the annealing soaking temperature is 650-680°C, the holding time is 40-50s, the annealing slow cooling section temperature is 540-570°C, the annealing fast cooling section temperature is 330-360°C, the artificial aging temperature is 380-410°C, and the holding time is 140-180s.

[0014] Furthermore, in the flattening process of the present invention, the steel strip after continuous annealing is flattened, and the flattening elongation is 0.7-1.7%.

[0015] The inventive principle and beneficial technical effects of the technical solution of the present invention are: The low-cost aging-resistant tin-plated steel strip provided by the present invention adopts a micro-carbon steel composition system in its composition design, adds a trace amount of B element to replace high-value alloy elements such as Nb and Ti, and reduces the N element by controlling and optimizing production processes such as RH refining, ultimately achieving the purpose of low-cost production of aging-resistant tin-plated steel strip.

[0016] The present invention adopts a micro-carbon steel component system. During continuous annealing cooling, dissolved carbon will precipitate within the grains and at the grain boundaries, which will result in a relatively small amount of dissolved carbon. However, when the carbon content is low, dissolved carbon will only precipitate at the grain boundaries during the cooling process, and the unprecipitated dissolved carbon content is much greater than the carbides precipitated at the grain boundaries, resulting in a high final dissolved carbon content in the material, which will precipitate during the aging process. Because the B element can act as a substitutional and interstitial element in steel, it can reduce the presence of dissolved carbon in the material, and the presence of BN also reduces the presence of dissolved nitrogen. Therefore, B plays a major role in the aging resistance of the micro-carbon steel.

[0017] The tin-plated steel strip provided by the present invention has a reasonable matching degree of strength, processing performance and coating performance, a yield strength of 210 to 260 MPa, a tensile strength of 330 to 390 MPa, and an elongation A50 of 32%.

[0018] The tinned steel strip and the production method thereof provided by the present invention have the characteristics of low production cost, good surface quality, excellent product performance, good anti-aging performance, good stamping forming and simple process. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described in detail below through examples.

[0020] A low-cost aging-resistant tin-plated steel strip, the chemical composition and mass percentage of which are shown in Table 1, where the remainder in Table 1 is Fe and other inevitable impurities.

[0021]

[0022] The production method of low-cost aging-resistant tin-plated steel strip includes smelting, RH refining, continuous casting, hot rolling, pickling and cold rolling, continuous annealing, tempering, and tin plating. The specific process control is as follows: (1) RH refining: The outlet temperature of the converter is controlled at 1620-1640°C. The net cycle time of RH refining is >8 min, the composition meets the target requirements of the finished product, and the outlet temperature is controlled at 1585-1600°C. The control parameters of the RH refining process in each embodiment are shown in Table 2.

[0023]

[0024] (2) Hot Rolling: The continuous casting slab was heated to 1200-1250°C for 140-220 min. The rough rolling temperature was 1030-1090°C. The finishing rolling inlet temperature was 1010-1050°C, and the finishing rolling temperature was 850-910°C. The coiling temperature was 590-630°C, and the cooling method used was a post-cooling process. The hot rolling process parameters for each example are shown in Table 3.

[0025]

[0026] (3) Cold rolling: The hot-rolled steel strip is pickled and then rolled in a cold rolling mill. The cold rolling mill adopts a single-stand rolling mill with a total reduction rate of 82% to 90%.

[0027] (4) Continuous annealing process: The cold-rolled steel strip enters the continuous annealing furnace for annealing treatment. The annealing temperature is 650-680℃, the holding time is 40-50s, the annealing slow cooling section temperature is 540-570℃, the annealing process fast cooling section temperature is 330-360℃, the artificial aging temperature is 380-410℃, and the holding time is 140-180s.

[0028] (5) Flatness: The steel strip after continuous annealing is flattened, and the flattening elongation is 0.7-1.7%.

[0029] The control parameters of cold rolling, annealing and leveling processes of each example steel are shown in Table 4.

[0030]

[0031] The yield strength, tensile strength and elongation of the tin-plated steel strips of each embodiment were tested after production and after standing for 6 months. The results are shown in Table 5.

[0032]

[0033] As can be seen from Table 5, after the tin-plated substrate provided by the present invention has been left for 6 months, the yield strength, tensile strength, and elongation are slightly different from those after production, which meets the design of the expected aging index ≤30 MPa; at the same time, all test results meet the yield strength of 210-260 MPa, tensile strength of 330-390 MPa, elongation A50 ≥32%, and aging index ≤30 MPa, proving that the tin-plated substrate provided by the present invention has good aging resistance.

[0034] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A low-cost anti-aging tin-plated steel strip, characterized by: The chemical composition and mass percentage of the steel strip are: C: 0.020-0.040%, Si: ≤0.04%, Mn: 0.20-0.30%, P: ≤0.024%, S: ≤0.016%, Al: 0.025-0.055%, N: ≤0.0040%, As≤0.010%, B: 0.0010-0.0080%, T[O]≤0.0035%, and the rest are iron and unavoidable impurities.

2. A low-cost anti-aging tin-plated steel strip according to claim 1, characterized in that: The thickness of the steel strip is 0.15-1.20 mm.

3. The low-cost anti-aging tin-plated steel strip according to claim 1, characterized in that: The yield strength of the steel strip is 210-260 MPa, the tensile strength is 330-390 MPa, and the elongation A 50 ≥32%.

4. A method for producing low-cost anti-aging tin-plated steel strip according to claim 1, characterized in that: It includes smelting, RH refining, continuous casting, hot rolling, pickling and cold rolling, continuous annealing, leveling and tinning processes.

5. The method for producing a low-cost anti-aging tin-plated steel strip according to claim 4, characterized in that: The refining process: the converter smelting outlet temperature is controlled at 1620-1640°C: the RH refining net cycle time is >8min, the composition meets the target requirements of the finished product, and the outlet temperature is controlled at 1585-1600°C.

6. The method for producing a low-cost anti-aging tin-plated steel strip according to claim 4, characterized in that: The hot rolling process comprises heating the continuous casting slab to 1200-1250° C., heating the slab in the furnace for 140-220 min; the rough rolling temperature is 1030-1090° C.; the finishing rolling entrance temperature is 1010-1050° C., the finishing rolling final rolling temperature is 850-910° C.; the coiling temperature is 590-630° C., and the cooling method adopts the rear-stage cooling process.

7. The method for producing a low-cost anti-aging tin-plated steel strip according to claim 4, characterized in that: The cold rolling process is as follows: the hot-rolled steel strip is pickled and then put into a cold rolling mill for rolling. The cold rolling mill adopts a single-stand rolling mill, and the total reduction rate of each pass is 82-90%.

8. The method for producing a low-cost anti-aging tin-plated steel strip according to claim 4, characterized in that: The continuous annealing process: the cold-rolled steel strip enters a continuous annealing furnace for annealing treatment, the annealing soaking temperature is 650-680°C, the holding time is 40-50s, the annealing slow cooling section temperature is 540-570°C, the annealing fast cooling section temperature is 330-360°C, the artificial aging temperature is 380-410°C, and the holding time is 140-180s.

9. The method for producing a low-cost anti-aging tin-plated steel strip according to claim 4, characterized in that: The leveling process: the leveling elongation is 0.7-1.7%.

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