Manufacturing method of low-cost steel belt for household appliance panel

Abstract

The invention discloses a manufacturing method of a low-cost steel strip for a household appliance panel, and belongs to the technical field of metallurgical steel rolling. According to the method, on the basis of C-Mn steel, a low-carbon and low-silicon smelting process technology is matched with a controlled rolling and controlled cooling process principle of a high initial rolling temperature and a low-temperature curling temperature; the rolling reduction rate of cold rolling is controlled to be 60%-87%, so that the forming performance is guaranteed; a stepped annealing process is adopted, the heat preservation time and the cooling time are reasonably controlled, favorable textures are increased, and the rigidity and the forming performance of the steel plate are guaranteed; a proper pressing process is adopted for leveling, and the elongation is controlled to be not greater than 3%, so that a yield platform is eliminated, and the plate shape is improved.

Description

Technical Field

[0001] This invention relates to the field of metallurgical steel rolling technology, and in particular to a method for manufacturing low-cost steel strips for home appliance panels. Background Technology

[0002] As a pillar industry of national economic growth, the home appliance industry has become a mainstay for my country's sustainable and healthy economic growth. The output of major home appliance products in my country has continued to grow. The basic characteristics of steel used in home appliances are lightweight, aesthetically pleasing, and environmentally friendly. Large home appliances use over 80% of their steel, while sheet metal accounts for 95% of all steel consumption. As home appliances gradually move towards high-end products, higher demands are being placed on the performance of materials such as steel. Metal materials requiring not only good machinability but also high strength and durability will be widely used in high-end home appliances. Cold-rolled steel for home appliances has a broad market potential, and steel mills can increase their R&D and quality improvement efforts in this area to capture a wider market share. Summary of the Invention

[0003] The purpose of this invention is to provide a low-cost manufacturing method for steel strips used in home appliance panels. Based on C-Mn steel, the method employs a low-carbon, low-silicon smelting process combined with a controlled rolling and cooling process using a relatively high initial rolling temperature and a low-temperature coiling temperature. The cold rolling reduction rate is controlled between 60% and 87% to ensure formability. A stepped annealing process is used, with reasonable control of holding and cooling times to increase favorable texture and ensure the steel plate's rigidity and formability. A suitable reduction process is used for leveling, controlling the elongation rate to no more than 3% to eliminate yield plateaus and improve plate shape.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This invention discloses a low-cost method for manufacturing steel strips for home appliance panels.

[0006] Includes the following steps:

[0007] (1) Heat the slab with a thickness of 67-72 mm and meeting the chemical composition requirements to 1050-1070℃ and keep it warm for 40 minutes;

[0008] (2) Hot rolling control: the initial rolling temperature is greater than 1040℃, and the final rolling temperature is 860~890℃; the heating temperature is 1040~1060℃.

[0009] (3) After hot rolling, a dispersed laminar flow cooling mode is used for cooling to control the cooling rate and intensity; the coiling temperature is 550-580℃.

[0010] (4) The cold rolling reduction rate is controlled at 60% to 87%;

[0011] (5) After cold rolling, the temperature is raised to 440-460℃ at a rate of 80-120℃ / hour, and then raised to 670-690℃ at a rate of 30-50℃ / hour. The temperature is held for 8-10 hours. The temperature is then slowly cooled to 60-80℃. The microstructure is ferrite with a small amount of pearlite and the grain size is 10-11.

[0012] (6) The flattening process adopts a suitable pressing process to control the elongation to be no more than 3%;

[0013] The chemical composition of the slab by mass percentage is C: 0.03-0.06%, Si: ≤0.03%, Mn: 0.10-0.30%, P≤0.02%, S≤0.015%, Alt≥0.015%, with the remainder being Fe and unavoidable inclusions.

[0014] Furthermore, the chemical composition of the slab by mass percentage is C: 0.05%, Si: 0.02%, Mn: 0.14%, P: 0.013%, S: 0.008%, Alt: 0.021%, with the remainder being Fe and unavoidable inclusions.

[0015] Furthermore, the chemical composition of the slab by mass percentage is C: 0.04%, Si: 0.018%, Mn: 0.14%, P: 0.012%, S: 0.008%, Alt: 0.027%, with the remainder being Fe and unavoidable inclusions.

[0016] Furthermore, the chemical composition of the slab by mass percentage is C: 0.05%, Si: 0.020%, Mn: 0.17%, P: 0.009%, S: 0.006%, Alt: 0.022%, with the remainder being Fe and unavoidable inclusions.

[0017] Furthermore, the chemical composition of the slab by mass percentage is C: 0.04%, Si: 0.017%, Mn: 0.14%, P: 0.016%, S: 0.006%, Alt: 0.019%, with the remainder being Fe and unavoidable inclusions.

[0018] Furthermore, the chemical composition of the slab by mass percentage is C: 0.05%, Si: 0.024%, Mn: 0.14%, P: 0.009%, S: 0.005%, Alt: 0.027%, with the remainder being Fe and unavoidable inclusions.

[0019] Furthermore, the initial rolling temperature is 1050℃, and the final rolling temperature is 875℃.

[0020] Furthermore, after cold rolling, the temperature is increased to 450°C at a rate of 100°C / hour, and then increased to 680°C at a rate of 40°C / hour, and held for 8-10 hours; then slowly cooled to 70°C.

[0021] Low carbon and silicon content is fundamental to improving the elongation of steel. Carbon and silicon, as interstitial atoms dissolved in steel, increase with their content, leading to a higher yield strength, increased resistance to deformation, and negatively impacting formability. Controlling phosphorus and sulfur levels effectively reduces sulfide nonmetallic inclusions, improving the ductility and toughness of steel and making cast billets less prone to cracking. Aluminum in steel has a grain-refining effect, but excessive levels will increase the formation of aluminum oxide inclusions.

[0022] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0023] 1. In today's fiercely competitive market, low cost and high return have become the guiding principle and goal for all businesses. While meeting product requirements, this product adheres to a low-cost production approach, employing low-carbon and low-silicon processing technology on a C-Mn steel base. Optimized production processes improve the overall performance of the steel plate, providing an excellent and environmentally friendly substrate for galvanizing and color coating production.

[0024] 2. This invention employs low-cost clean steelmaking technology, simplifying the process and reducing energy consumption. Single-slag operation is adopted, and subsequent control measures such as rapid slag formation, control of slag basicity, and slag-blocking during steel tapping are implemented to reduce the phosphorus (P) content in the molten steel, thereby shortening the production cycle and improving economic efficiency. Sulfur removal mainly occurs during refining, achieved through electrode heating and white slag formation. Sulfur makes steel plates brittle, reducing their ductility and deep-drawing properties. During enameling, sulfur combines with oxygen to form SO2, leading to various defects in the enamel layer such as bubbles and pinholes. High sulfur content easily causes segregation, resulting in a banded structure in the metallographic structure, leading to anisotropy in the physical and mechanical properties of the steel plate. This causes different shrinkage in different directions during cooling, resulting in surface cracking and scaling. The molten steel undergoes Ca treatment, which modifies MnS inclusions and eliminates the harmful effects of sulfur in the steel. Calcium treatment is then performed after refining.

[0025] 3. This invention achieves stable production of low-cost 0.60mm thick cold-rolled steel sheets for home appliance panels by controlling the rolling and cooling processes, simplifying the production process. Under the premise of meeting user requirements, it realizes the purpose of using steel with the same chemical composition for multiple functions and uses, reducing costs, simplifying the production process, improving production efficiency, and reducing energy consumption, which is in line with the development direction of developing energy-saving, clean and green steel. Detailed Implementation

[0026] The following is a detailed description of the low-cost steel strip for home appliance panels and its manufacturing method, with examples provided:

[0027] Using steel with the chemical composition listed in Table 1 as raw material, the steel billet underwent smelting processes including low-desulfurization, converter smelting, refining, and calcium treatment. The billet dimensions were 67-72 mm (thickness) × 320 mm (width) × 500 mm (length). The slab was heated in a furnace, homogenized, and hot-rolled with controlled initial and final rolling temperatures. The cooling rate was controlled after rolling. The hot-rolled steel plate was then cold-rolled after pickling. After cold rolling, a double-step annealing process was used, with careful control of holding and cooling times. The finished steel plate thickness was 0.60 mm. Mechanical property tests are shown in Table 2.

[0028] Table 1. Chemical composition of the steel of this invention, wt%.

[0029]

[0030]

[0031] Controlled rolling and controlled cooling mainly involves strictly controlling the rolling and cooling process parameters according to specifications, including: (1) the initial rolling temperature in the austenite recrystallization zone is 1050℃, (2) the total rolling reduction rate is ≥87%, and the final rolling temperature is 875℃. (3) Cooling is carried out using a dispersed laminar flow cooling mode. After cold rolling, the temperature is raised to 450℃ at a rate of 100℃ / hour, and then raised to 680℃ at a rate of 40℃ / hour, and held for 8 to 10 hours; then slowly cooled to 70℃. Ferrite + a small amount of pearlite is achieved, with a grain size of 10 to 11.

[0032] The experimental results of the low-cost steel strip for home appliance panels and the manufacturing method of the present invention are listed in Table 2. It can be seen from the table that the yield strength of the steel strip is less than 225 MPa, the tensile strength is greater than 323 MPa, and the elongation is ≥39.5%. This meets the standards and customer technical requirements.

[0033] Table 2 Experimental results of the steel of the present invention

[0034]

[0035] 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 manufacturing a low-cost steel strip for home appliance panels, characterized in that: Includes the following steps: (1) Heat the slab with a thickness of 67-72 mm and meeting the chemical composition requirements to 1050-1070℃ and keep it warm for 40 minutes; (2) Hot rolling control: the initial rolling temperature is greater than 1040℃, and the final rolling temperature is 860~890℃; the heating temperature is 1040~1060℃. (3) After hot rolling, a dispersed laminar flow cooling mode is used for cooling to control the cooling rate and intensity; the coiling temperature is 550-580℃. (4) The cold rolling reduction rate is controlled at 60% to 87%; (5) After cold rolling, the temperature is raised to 440-460℃ at a rate of 80-120℃ / hour, and then raised to 670-690℃ at a rate of 30-50℃ / hour. The temperature is held for 8-10 hours. The temperature is then slowly cooled to 60-80℃. The microstructure is ferrite with a small amount of pearlite and the grain size is 10-11. (6) The flattening process adopts a suitable pressing process to control the elongation to be no more than 3%; The chemical composition of the slab by mass percentage is C: 0.03-0.06%, Si: ≤0.03%, Mn: 0.10-0.30%, P≤0.02%, S≤0.015%, Alt≥0.015%, with the remainder being Fe and unavoidable inclusions.

2. The method for manufacturing low-cost steel strip for home appliance panels according to claim 1, characterized in that: The chemical composition of the slab by mass percentage is C: 0.05%, Si: 0.02%, Mn: 0.14%, P: 0.013%, S: 0.008%, Alt: 0.021%, with the remainder being Fe and unavoidable inclusions.

3. The method for manufacturing low-cost steel strip for home appliance panels according to claim 1, characterized in that: The chemical composition of the slab by mass percentage is C: 0.04%, Si: 0.018%, Mn: 0.14%, P: 0.012%, S: 0.008%, Alt: 0.027%, with the remainder being Fe and unavoidable inclusions.

4. The method for manufacturing low-cost steel strip for home appliance panels according to claim 1, characterized in that: The chemical composition of the slab by mass percentage is C: 0.05%, Si: 0.020%, Mn: 0.17%, P: 0.009%, S: 0.006%, Alt: 0.022%, with the remainder being Fe and unavoidable inclusions.

5. The method for manufacturing low-cost steel strip for home appliance panels according to claim 1, characterized in that: The chemical composition of the slab by mass percentage is C: 0.04%, Si: 0.017%, Mn: 0.14%, P: 0.016%, S: 0.006%, Alt: 0.019%, with the remainder being Fe and unavoidable inclusions.

6. The method for manufacturing low-cost steel strip for home appliance panels according to claim 1, characterized in that: The chemical composition of the slab by mass percentage is C: 0.05%, Si: 0.024%, Mn: 0.14%, P: 0.009%, S: 0.005%, Alt: 0.027%, with the remainder being Fe and unavoidable inclusions.

7. The method for manufacturing low-cost steel strip for home appliance panels according to claim 1, characterized in that: The initial rolling temperature is 1050℃, and the final rolling temperature is 875℃.

8. The method for manufacturing low-cost steel strip for home appliance panels according to claim 1, characterized in that: After cold rolling, the temperature is increased to 450℃ at a rate of 100℃ / hour, and then increased to 680℃ at a rate of 40℃ / hour, and held for 8 to 10 hours. Slowly cool to 70°C.

Images