A method for integrally manufacturing a barrel body, a cover and a bottom of a food-grade tomato barrel from cold-rolled low-carbon steel

Abstract

The application discloses a kind of food-grade tomato barrel barrel body, lid, bottom cold-rolled low-carbon steel integrated preparation method, comprising: (1) smelting and continuous casting;(2) hot rolling;(3) cold rolling and cleaning;(4) bell annealing;Its chemical composition mass percentage content is: C≤0.08;Si≤0.10;Mn≤0.50;P≤0.035;S≤0.030;Alt≥0.020;Refining internal control: C 0.04~0.06, Si≤0.03, Mn 0.25~0.35, P≤0.020, S≤0.009, Alt 0.025~0.035, Ca 0.0020~0.0030, the rest is Fe and impurities.The purpose of the present application is to provide a kind of food-grade tomato barrel barrel body, lid, bottom cold-rolled low-carbon steel integrated preparation method, the performance of the prepared finished product is excellent: moderate strength, high elongation, barrel body / barrel bottom continuous punching qualified rate 100%.

Description

Technical Field

[0001] This invention belongs to the technical field of metal materials for food packaging, and particularly relates to an integrated method for preparing the body, lid and bottom of a food-grade tomato barrel from cold-rolled low-carbon steel. Background Technology

[0002] COFCO Group (Bayannur) has a unique tomato market, and various industries have emerged around tomato production. This invention discloses a method for preparing food-grade cold-rolled low-carbon steel for tomato barrels and its integrated barrel body, lid, and bottom. Tomato sauce is an acidic food, and the requirements for the deep-drawing formability, corrosion resistance, surface cleanliness, and food safety of the packaging steel are extremely high. Existing barrel-making steel generally suffers from the following problems: (1) large fluctuations in composition, making it easy to crack and wrinkle during stamping; (2) many surface defects, failing to meet food contact grade requirements; (3) poor matching of annealing processes, making it difficult to balance strength and elongation; (4) insufficient stability in batch stamping formability, resulting in a low barrel qualification rate. COFCO Group (Bayannur) has an annual demand of about 5,000 to 6,000 tons of tomato barrels, with a broad and stable market prospect. Baogang is located in Baotou City, 240 kilometers away from Bayannur, and has significant advantages in product delivery time, logistics transportation, technical services, and overall cost. Summary of the Invention

[0003] The purpose of this invention is to provide an integrated manufacturing method for the body, lid, and bottom of a food-grade tomato barrel made of cold-rolled low-carbon steel, achieving the following:

[0004] (1) Provide low-carbon cold-rolled base material specifically for tomato food buckets, with composition and performance highly compatible with stamping and food contact requirements.

[0005] (2) Establish a stable process for the entire process from smelting → hot rolling → cold rolling → annealing → leveling → barrel making, and achieve a 100% pass rate for barrel body, lid and bottom stamping.

[0006] (3) It meets the requirements of corrosion resistance, non-toxicity, odorlessness and surface cleanliness for long-term storage of acidic tomato sauce.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] This invention discloses a method for integrally manufacturing a food-grade tomato barrel using cold-rolled low-carbon steel for the barrel body, lid, and bottom, comprising:

[0009] (1) Smelting and continuous casting

[0010] Molten iron: Si 0.2~1.2%, Mn 0.30~1.00%, P≤0.140%, S≤0.070%;

[0011] Converter: final concentration C 0.04%, P≤0.015%, S≤0.030%, slag basicity 3.2~3.5, tapping temperature 1600~1640℃;

[0012] Refining: The temperature of the first furnace in the casting machine is 1592±3℃, and the temperature of subsequent furnaces is 1577±3℃. The superheat is 20~35℃. Low carbon protective slag is used, and long nozzle argon seal is used for casting protection.

[0013] (2) Hot rolling

[0014] Furnace exit temperature: 2.0~2.5mm thickness > 1120±20℃; 2.5~3.0mm thickness > 1100±20℃; 3.0~4.0mm thickness > 1080±20℃; 4.0~6.0mm thickness > 1070±20℃;

[0015] Final rolling temperature: 880~900±15℃; Coiling temperature: 570~590±20℃; Cooling mode: pre-cooling + dispersion cooling;

[0016] (3) Cold rolling and cleaning

[0017] Finished products with a thickness of 0.6mm are rolled from 2.8mm raw materials; products with a thickness of 0.8~0.9mm are rolled from 3.0mm raw materials.

[0018] Five-stand rolls: S1~S4 smooth rolls Ra 0.5~0.8μm, S5 textured rolls Ra 3.0~4.0μm;

[0019] Cleaning temperature 55~80℃, alkaline solution conductivity 60±5ms / cm, electrolyte conductivity 65±5ms / cm, demineralized water conductivity <20μs / cm;

[0020] (4) Bell-type annealing

[0021] 0.6mm specification: Heating for 10~12 hours, holding at 660±10℃ for 11 hours, slow cooling for 2-4 hours, furnace exit temperature ≤90℃;

[0022] 0.6~0.9mm specifications: heat preservation at 680±10℃ for 9~10h, slow cooling for 1.5-2.5h, furnace exit temperature ≤90℃;

[0023] Hydrogen flow rate: 25-27 m³ / h during the heating phase, 22-24 m³ / h during the continuous phase, with the flow rate not less than 90% of the set value;

[0024] (5) Flattening and re-dividing the roll

[0025] Elongation at break: ≤0.6mm: 0.7±0.1%; >0.6~0.9mm: 0.8±0.1%;

[0026] For leveling, apply 500-700 mg / m² of oil per side; for re-rolled surfaces, apply 300 mg / m² per side in the non-rainy season and 350 mg / m² per side in the rainy season.

[0027] The elongation rate after tension straightening is 0.05%~0.4%;

[0028] Its chemical composition by mass percentage is as follows: C≤0.08; Si≤0.10; Mn≤0.50; P≤0.035; S≤0.030; Alt≥0.020; Refining internal control: C 0.04~0.06, Si≤0.03, Mn 0.25~0.35, P≤0.020, S≤0.009, Alt 0.025~0.035, Ca 0.0020~0.0030, with the remainder being Fe and impurities.

[0029] Furthermore, the mechanical properties meet the following requirements: yield strength Rp0.2 / Rel≤280MPa; tensile strength≥270MPa; elongation after fracture A50%: for thickness ≤0.6mm, elongation after fracture ≥34%; for thickness >0.6~0.9mm, elongation after fracture ≥36%.

[0030] Furthermore, the hot rolling exit temperature is 1100℃, the final rolling temperature is 890℃, and the coiling temperature is 580℃.

[0031] Furthermore, the 0.6mm specification is: heat preservation at 660℃ for 11 hours, followed by slow cooling for 3 hours.

[0032] Furthermore, the 0.6~0.9mm specification requires: heat preservation at 680℃ for 9~10 hours, followed by slow cooling for 2 hours.

[0033] Furthermore, the hydrogen flow rate is 26 m³ / h during the heating phase and 23 m³ / h during the continuous phase, with the flow rate not less than 90% of the set value.

[0034] Furthermore, the cold-rolled raw material is rolled from 3.0mm to 0.8mm, with S5 texturing roll Ra=3.5μm; the roll is then held at 680℃ for 10h, slowly cooled for 2h, and exited at 75℃; the leveling elongation is 0.8%, and the oil coating amount is 550mg / m².

[0035] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0036] (1) Precise and controllable composition: low P, low S, high Alt, pure steel, no cracking or wrinkling during deep drawing;

[0037] (2) Excellent performance matching: moderate strength, high elongation, and 100% pass rate for continuous stamping of barrel body / bottom;

[0038] (3) Food-grade safety: Surface grade FB, no harmful defects, excellent acid resistance, suitable for long-term storage of acidic tomato sauce;

[0039] (4) Stable and replicable process: More than 3,800 tons have been produced in batches and more than 3,500 tons have been shipped, with controllable costs;

[0040] (5) Replacement of benchmark products: Replacement of products from other steel mills in the same industry, with better forming and surface quality and higher delivery stability.

[0041] (6) The tomato barrels, lids, and bottoms produced have a yield strength of 166~207MPa, a tensile strength of 318~339MPa, and an elongation of 40.0~46.0%. The product performance meets customer requirements, and the stamping qualification rate is 100%. Attached Figure Description

[0042] The present invention will be further described below with reference to the accompanying drawings.

[0043] Figure 1 This is a metallographic image of the present invention;

[0044] Figure 2 Photo of the barrel body being stamped;

[0045] Figure 3 Photos of the stamping process for the bucket lid and bottom. Detailed Implementation

[0046] The present invention will be described in more detail below through specific embodiments. These embodiments are merely descriptions of the best mode of implementation and do not limit the scope of the invention in any way.

[0047] Example 1

[0048] Steel for producing 0.80mm thick tomato barrels (its chemical composition by mass percentage is: C: 0.04; Si: 0.020; Mn: 0.26; P: 0.013; S: 0.004; Alt: 0.034; steelmaking converter → LF refining, C=0.05%, Mn=0.30%, S=0.004%, Alt=0.030%; hot rolling furnace exit temperature 1100℃, final rolling temperature 890℃, coiling temperature 580℃); Cold-rolled raw material 3.0mm is rolled to a finished product of 0.8mm, with S5 texturing roll Ra=3.5μm; annealing at 680℃ for 10h, slow cooling for 2h, and exiting the furnace at 75℃; leveling elongation 0.8%, oil coating 550mg / m²; 523 barrels were stamped, with a 100% pass rate, no cracks, and no deformation. Mechanical properties: yield strength Rp0.2 / Rel: 186MPa; tensile strength: 327MPa; elongation after fracture A50%: 43.5%.

[0049] Example 2

[0050] Steel for producing 0.60mm thick tomato bucket bottoms / lids was manufactured. The steelmaking, hot rolling, and cold rolling processes were the same as in Example 1; the buckets were annealed at 660℃ for 11 hours, then slowly cooled for 3 hours, with a furnace exit temperature ≤90℃; the flattening elongation was 0.7±0.1%; 8695 bucket lids / bottoms were stamped, with a 100% pass rate, showing no cracks or deformation. Mechanical properties: Yield strength Rp0.2 / Rel: 183MPa; Tensile strength: 333MPa; Elongation after fracture A50%: 45.5%.

[0051] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for integrally manufacturing a food-grade tomato barrel using cold-rolled low-carbon steel for the barrel body, lid, and bottom, characterized in that: include: (1) Smelting and continuous casting Molten iron: Si 0.2~1.2%, Mn 0.30~1.00%, P≤0.140%, S≤0.070%; Converter: final concentration C 0.04%, P≤0.015%, S≤0.030%, slag basicity 3.2~3.5, tapping temperature 1600~1640℃; Refining: The temperature of the first furnace in the casting machine is 1592±3℃, and the temperature of subsequent furnaces is 1577±3℃. The superheat is 20~35℃. Low carbon protective slag is used, and long nozzle argon seal is used for casting protection. (2) Hot rolling Furnace exit temperature: 2.0~2.5mm thickness > 1120±20℃; 2.5~3.0mm thickness > 1100±20℃; 3.0~4.0mm thickness > 1080±20℃; 4.0~6.0mm thickness > 1070±20℃; Final rolling temperature: 880~900±15℃; Coiling temperature: 570~590±20℃; Cooling mode: pre-cooling + dispersion cooling; (3) Cold rolling and cleaning Finished products with a thickness of 0.6mm are rolled from 2.8mm raw materials; products with a thickness of 0.8~0.9mm are rolled from 3.0mm raw materials. Five-stand rolls: S1~S4 smooth rolls Ra 0.5~0.8μm, S5 textured rolls Ra 3.0~4.0μm; Cleaning temperature 55~80℃, alkaline solution conductivity 60±5ms / cm, electrolyte conductivity 65±5ms / cm, demineralized water conductivity <20μs / cm; (4) Bell-type annealing 0.6mm specification: Heating for 10~12 hours, holding at 660±10℃ for 11 hours, slow cooling for 2-4 hours, furnace exit temperature ≤90℃; 0.6~0.9mm specifications: heat preservation at 680±10℃ for 9~10h, slow cooling for 1.5-2.5h, furnace exit temperature ≤90℃; Hydrogen flow rate: 25-27 m³ / h during the heating phase, 22-24 m³ / h during the continuous phase, with the flow rate not less than 90% of the set value; (5) Flattening and re-dividing the roll Elongation at break: ≤0.6mm: 0.7±0.1%; >0.6~0.9mm: 0.8±0.1%; For leveling, apply 500-700 mg / m² of oil per side; for re-rolled surfaces, apply 300 mg / m² per side in the non-rainy season and 350 mg / m² per side in the rainy season. The elongation rate after tension straightening is 0.05%~0.4%; Its chemical composition by mass percentage is as follows: C≤0.08; Si≤0.10; Mn≤0.50; P≤0.035; S≤0.030; Alt≥0.020; Refining internal control: C 0.04~0.06, Si≤0.03, Mn 0.25~0.35, P≤0.020, S≤0.009, Alt0.025~0.035, Ca 0.0020~0.0030, with the remainder being Fe and impurities.

2. The method for integrally manufacturing the body, lid, and bottom of a food-grade tomato barrel using cold-rolled low-carbon steel according to claim 1, characterized in that: Mechanical properties must meet the following requirements: yield strength Rp0.2 / Rel≤280MPa; tensile strength≥270MPa; elongation after fracture A50%: for thickness ≤0.6mm, elongation after fracture ≥34%; >0.6~0.9mm Elongation after fracture ≥36%.

3. The method for integrally manufacturing the body, lid, and bottom of a food-grade tomato barrel using cold-rolled low-carbon steel according to claim 1, characterized in that: The hot rolling exit temperature is 1100℃, the final rolling temperature is 890℃, and the coiling temperature is 580℃.

4. The method for integrally manufacturing the body, lid, and bottom of a food-grade tomato barrel using cold-rolled low-carbon steel according to claim 1, characterized in that: The 0.6mm specification: heat preservation at 660℃ for 11 hours, followed by slow cooling for 3 hours.

5. The method for integrally manufacturing the body, lid, and bottom of a food-grade tomato barrel using cold-rolled low-carbon steel according to claim 1, characterized in that: For the 0.6~0.9mm specification: keep warm at 680℃ for 9~10 hours, then cool slowly for 2 hours.

6. The method for integrally manufacturing the body, lid, and bottom of a food-grade tomato barrel using cold-rolled low-carbon steel according to claim 1, characterized in that: Hydrogen flow rate: 26 m³ / h during the heating phase and 23 m³ / h during the continuous phase, with the flow rate not less than 90% of the set value.

7. The method for integrally manufacturing the body, lid, and bottom of a food-grade tomato barrel using cold-rolled low-carbon steel according to claim 3, characterized in that: The cold-rolled raw material is rolled from 3.0mm to 0.8mm, with S5 texturing roll Ra=3.5μm; the roll is then held at 680℃ for 10h, slowly cooled for 2h, and exited at 75℃; the leveling elongation is 0.8%, and the oil coating amount is 550mg / m².

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