A method for controlling the plating layer cooling rate in the production of an extremely thick plating layer aluminum-zinc-magnesium plate

Abstract

The present application relates to the technical field of production of extremely thick plated aluminum-zinc-magnesium sheet, in particular to a method for controlling the plating cooling rate in the production of extremely thick plated aluminum-zinc-magnesium sheet. 1) Set the condensation line as a parabola opening downward, the condensation line height is the distance from the air knife to the top end of the condensation line, the condensation line height H, mm; 2) Real-time measure the condensation line height through the height scale; 3) Control the condensation line height through the output power of the cold section movable fan; 4) Control the cooling rate through the condensation line height. The present application proposes to judge the plating cooling rate based on the condensation line height when the liquid plating solidifies into solid plating, to realize fine control of the cooling rate, to realize stable, high-quality and efficient production of extremely thick plated aluminum-zinc-magnesium products under the premise of not increasing equipment investment and large-scale modification, to greatly reduce the production cost, and to ensure stable operation of the unit and that the product quality meets the requirements.

Description

Technical Field

[0001] This invention relates to the field of production technology for ultra-thick coated aluminum-zinc-magnesium sheets, specifically a method for controlling the cooling rate of the coating during the production of ultra-thick coated aluminum-zinc-magnesium sheets. Background Technology

[0002] Aluminum-zinc-magnesium (AZM) steel sheet is a highly corrosion-resistant coating product. It combines the excellent corrosion resistance of aluminum with the cathodic corrosion protection of zinc. Furthermore, the addition of a certain amount of magnesium effectively solves the problem of poor edge protection in aluminum-zinc coated products. Therefore, AZM steel sheet has excellent atmospheric corrosion resistance, which is 8 to 10 times that of hot-dip galvanized steel sheet of the same coating thickness. In addition, AZM coatings also exhibit good paintability, processability, and excellent heat reflectivity. Due to its excellent comprehensive performance, AZM products have developed rapidly and are widely used in construction, automotive, agriculture, and household appliance industries.

[0003] The coating thickness of ultra-thick aluminum-zinc-magnesium sheet is 150-300 g / m. 2 During the production process, the phase change process of aluminum-zinc-magnesium-zinc plating solution is relatively complex, and the target coating thickness is relatively thick, so the cooling rate needs to be precisely controlled. At present, real-time temperature is usually used to precisely control the cooling rate.

[0004] However, real-time temperature measurement of the zinc layer during the cooling process requires extensive equipment modifications, which is costly. Therefore, how to achieve precise control of the coating cooling rate without increasing equipment investment, and ensure the stable, high-quality and efficient production of ultra-thick coated aluminum-zinc-magnesium plates, has become a pressing technical challenge in this field. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for controlling the coating cooling rate during the production of ultra-thick coated aluminum-zinc-magnesium sheets. Without increasing equipment investment, this method achieves precise control of the coating cooling rate, ensuring stable, high-quality, and efficient production of ultra-thick coated aluminum-zinc-magnesium sheets.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for controlling the cooling rate of the coating during the production of ultra-thick aluminum-zinc-magnesium alloy sheets, the method specifically includes the following steps:

[0008] 1) Set the condensation line as a downward-opening parabola, and the height of the condensation line is the distance from the air knife to the top of the condensation line, H, mm.

[0009] 2) Measure the height of the condensation line in real time using a height gauge.

[0010] 3) Control the height of the condensate line using a mobile fan in the cold section.

[0011] The strip thickness is D, mm; the unit speed is V, m / min.

[0012] ① D≤0.6mm,

[0013] If 80m / min≤V≤120m / min, then 4.0mm≤H≤4.5mm; if 120m / min<V≤150m / min, then 4.5mm<H≤5.0mm.

[0014] ② 0.6mm < D ≤ 1.0mm,

[0015] If 80m / min≤V≤100m / min, then 4.0mm≤H≤4.5mm; if 100m / min<V≤135m / min, then 4.5mm<H≤5.0mm.

[0016] ③ 1.0mm<D≤1.4mm,

[0017] If 60m / min≤V≤90m / min, then 3.0mm≤H≤3.5mm;

[0018] If 90m / min < V ≤ 125m / min, then 3.5mm < H ≤ 4.0mm;

[0019] ④ 1.4mm<D≤1.8mm,

[0020] If 55m / min≤V≤90m / min, then 3.0mm≤H≤3.5mm;

[0021] If 90m / min < V ≤ 110m / min, then 3.5mm < H ≤ 4.0mm;

[0022] ⑤ 1.8mm<D≤2.0mm,

[0023] If 50m / min≤V≤70m / min, then 2.5mm≤H≤3.0mm;

[0024] If 70m / min < V ≤ 100m / min, then 2.0mm < H ≤ 2.5mm;

[0025] ⑥ 2.0mm<D≤2.5mm,

[0026] If 45m / min≤V≤65m / min, then 2.5mm≤H≤3.0mm;

[0027] If 65m / min < V ≤ 85m / min, then 2.0mm < H ≤ 2.5mm; 4) Control the cooling rate by the height of the condensation line:

[0028] Coating cooling rate V C ℃ / s;

[0029] ①D≤0.6mm, if 4.0≤H≤4.5, then 30<V C ≤32;

[0030] If D≤0.6mm and 4.5<H≤5.0, then 28≤V C ≤30;

[0031] ② 0.6mm < D ≤ 1.0mm, if 4.0 ≤ H ≤ 4.5, then 28 < V C ≤30;

[0032] 0.6mm < D ≤ 1.0mm; if 4.5 < H ≤ 5.0, then 25 ≤ V. C ≤28; ③1.0mm<D≤1.4mm, if 3.0≤H≤3.5, then 31<V C ≤33;

[0033] 1.0mm < D ≤ 1.4mm, if 3.5 < H ≤ 4.0, then 27 ≤ V C ≤31; ④1.4mm<D≤1.8mm, if 3.0≤H≤3.5, then 28<V C ≤32;

[0034] 1.4mm < D ≤ 1.8mm; if 3.5 < H ≤ 4.0, then 24 ≤ V. C ≤28; ⑤1.8mm<D≤2.0mm, if 2.0<H≤2.5, then 30<V C ≤34;

[0035] 1.8mm < D ≤ 2.0mm; if 2.5 < H ≤ 3.0, then 25 < V. C ≤30;

[0036] ⑥ 2.0mm < D ≤ 2.5mm; if 2.0 < H ≤ 2.5, then 26 < V C ≤30;

[0037] 2.0mm < D ≤ 2.5mm; if 2.5 < H ≤ 3.0, then 23 < V. C ≤26.

[0038] Furthermore, in step 2, a height scale is installed on the operating side frame of the movable cooling air box above the air knife.

[0039] Furthermore, in step 3, the width of the strip is 1000-1300 mm.

[0040] Furthermore, in step 3, the output power of the mobile fan is 60-120KW.

[0041] Furthermore, in step 4, the coating thickness is 150–300 g / m. 2 .

[0042] Furthermore, in step 4, the coating is a double-sided coating.

[0043] Compared with existing methods, the beneficial effects of the present invention are:

[0044] Currently, real-time temperature is typically used to precisely control the cooling rate. However, real-time temperature measurement of the zinc layer during the cooling process requires extensive equipment modifications, which is costly.

[0045] This invention introduces the concept and theory of zinc coating condensation line height. The condensation line is short for the cooling and solidification line. Because the steel strip dissipates heat quickly at the edges during cooling, while the middle section dissipates heat relatively slowly, the condensation line has a concave parabolic shape. The distance from the air knife to the top of the condensation line is defined as the condensation line height. When the steel strip passes through the air knife, the cooling and solidification process begins, ending at the top of the condensation line. Therefore, the range of the condensation line height precisely corresponds to the process of the coating changing from a liquid state to a solid crystal.

[0046] This invention innovatively proposes to determine the cooling rate of the coating based on the height of the condensation line when the liquid coating solidifies into a solid coating, thereby achieving precise control of the cooling rate.

[0047] This invention achieves high-quality and stable production of ultra-thick coated aluminum-zinc-magnesium sheets by controlling the cooling rate of the strip in the post-cooling section. Without increasing equipment investment or large-scale modifications, this invention enables stable, high-quality, and efficient production of ultra-thick coated aluminum-zinc-magnesium products, greatly reducing production costs and ensuring stable unit operation and product quality that meets requirements. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the condensation line of the coating of the present invention. Detailed Implementation

[0049] This invention discloses a method for controlling the cooling rate of the coating during the production of ultra-thick coated aluminum-zinc-magnesium sheets. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0050] A method for controlling the cooling rate of the coating during the production of ultra-thick aluminum-zinc-magnesium alloy sheets, the method specifically includes the following steps:

[0051] 1. Correlation between cooling rate and condensation line:

[0052] In aluminum-zinc-magnesium (AZM) units, the zinc layer temperature measurement device cannot be installed from the zinc pot to the post-cooling section, especially near the air knife area, due to space constraints. Therefore, zinc layer temperature cannot be used as an indicator of the zinc layer cooling rate. Other effective alternative methods are needed to provide real-time, quantitative characterization of the zinc layer cooling rate.

[0053] The condensation line, short for cooling-solidification line, is the boundary line where the steel strip solidifies from the liquid zinc bath after hot-dip galvanizing. After exiting the zinc bath, excess zinc is blown away by an air knife, forming a uniform liquid coating. As the strip rises in the cooling tower, its temperature decreases, and the coating solidifies from liquid to solid. Below the condensation line, the coating is liquid with high reflectivity and a distinct mirror-like luster; above the condensation line, the coating is solid with reduced reflectivity, exhibiting the silvery-white color of solid zinc and virtually no mirror-like luster. Because the steel strip dissipates heat quickly at the edges and relatively slowly in the center during cooling, the condensation line is a concave parabola. In the production of aluminum-zinc-magnesium products, especially when the coating is thick and the zinc bloom is prominent, the distance from the air knife to the top of the condensation line is defined as the condensation line height. The cooling and solidification process begins after the steel strip passes through the air knife and ends at the top of the condensation line. Therefore, the range of the condensation line height precisely represents the process of the coating changing from a liquid to a solid crystal. See the diagram for a specific zinc layer condensation line. Figure 1 .

[0054] The condensation curve is defined as a downward-opening parabola, and its height is the distance from the air knife to the top of the condensation curve, H, mm.

[0055] 2. Install a height gauge on the operating side frame of the movable cooling air box above the air knife to measure the height of the condensation line in real time.

[0056] 3. Control the condensate line height using a mobile fan in the cold section. The condensate line height is controlled by adjusting the fan's output power, as detailed below:

[0057] The strip thickness is D, mm; the output power of the mobile fan is P, KW; the unit speed is V, m / min.

[0058] (1) Strip thickness: D≤0.6mm

[0059] Depending on the unit speed, when 80m / min≤V≤120m / min, the output power of the mobile fan should be controlled to be 80KW≤P≤90KW, ensuring that the condenser wire height is 4.0mm≤H≤4.5mm.

[0060] Depending on the unit speed, when 120m / min < V ≤ 150m / min, the output power of the mobile fan should be controlled to be 90KW < P ≤ 100KW, ensuring that the condenser wire height is 4.5mm < H ≤ 5.0mm.

[0061] (2) Strip thickness: 0.6mm < D ≤ 1.0mm

[0062] Depending on the unit speed, when the speed is 80m / min≤V≤100m / min, the output power of the mobile fan should be controlled to be 70KW≤P≤80KW, and the height of the condenser line should be 4.0mm≤H≤4.5mm.

[0063] Depending on the unit speed, when 100m / min < V ≤ 135m / min, the output power of the mobile fan should be controlled to be 80KW < P ≤ 95KW, ensuring that the condenser wire height is 4.5mm < H ≤ 5.0mm.

[0064] (3) Strip thickness: 1.0mm < D ≤ 1.4mm

[0065] Depending on the unit speed, when the speed is 60m / min≤V≤90m / min, the output power of the mobile fan should be controlled to be 65KW≤P≤75KW, and the height of the condenser line should be 3.0mm≤H≤3.5mm.

[0066] Depending on the unit speed, when 90m / min < V ≤ 125m / min, the output power of the mobile fan should be controlled to be 75KW < P ≤ 90KW, ensuring that the condenser wire height is 3.5mm < H ≤ 4.0mm.

[0067] (4) Strip thickness: 1.4mm < D ≤ 1.8mm

[0068] Depending on the unit speed, when the speed is 55m / min≤V≤90m / min, the output power of the mobile fan should be controlled to be 70KW≤P≤85KW, and the height of the condenser line should be 3.0mm≤H≤3.5mm.

[0069] Depending on the unit speed, when 90m / min < V ≤ 110m / min, the output power of the mobile fan should be controlled to be 85KW < P ≤ 98KW, ensuring that the condenser wire height is 3.5mm < H ≤ 4.0mm.

[0070] (5) Strip thickness: 1.8mm < D ≤ 2.0mm

[0071] Depending on the unit speed, when the speed is 50m / min≤V≤70m / min, the output power of the mobile fan should be controlled to be 85KW≤P≤95KW, and the height of the condenser line should be 2.5mm≤H≤3.0mm.

[0072] Depending on the unit speed, when 70m / min < V ≤ 100m / min, the output power of the mobile fan should be controlled to be 95KW < P ≤ 110KW, ensuring that the condenser wire height is 2.0mm < H ≤ 2.5mm.

[0073] (6) Strip thickness: 2.0mm < D ≤ 2.3mm

[0074] Depending on the unit speed, when 45m / min≤V≤65m / min, the output power of the mobile fan should be controlled to be 90KW≤P≤100KW, ensuring that the condenser wire height is 2.5mm≤H≤3.0mm.

[0075] Depending on the unit speed, when 65m / min < V ≤ 85m / min, the output power of the mobile fan should be controlled to be 100KW < P ≤ 110KW, ensuring that the condenser wire height is 2.0mm < H ≤ 2.5mm.

[0076] 4. Control the cooling rate by adjusting the height of the condensation line:

[0077] Coating cooling rate V C ℃ / s;

[0078] (1) Strip thickness: D≤0.6mm

[0079] If 4.0 ≤ H ≤ 4.5, then 28 ≤ V C ≤30;

[0080] (2) Strip thickness: 0.6mm < D ≤ 1.0mm

[0081] If 4.0 ≤ H ≤ 4.5, then 25 ≤ V C ≤28;

[0082] (3) Strip thickness: 1.0mm < D ≤ 1.4mm

[0083] If 3.0 ≤ H ≤ 4.0, then 27 ≤ V C ≤31;

[0084] (4) Strip thickness: 1.4mm < D ≤ 1.8mm

[0085] If 3.0 ≤ H ≤ 4.0, then 24 ≤ V C ≤28;

[0086] (5) Strip thickness: 1.8mm < D ≤ 2.0mm

[0087] If H ≤ 3.0, then 25 ≤ V C ≤30;

[0088] (6) Strip thickness: 2.0mm < D ≤ 2.3mm

[0089] If H ≤ 3.0, then 23 ≤ V C ≤26.

[0090]

Example

[0091] All embodiments of the present invention follow the above method to control the coating cooling rate during the production of ultra-thick coated aluminum-zinc-magnesium plates.

[0092] Example 1

[0093] (1) Strip specifications: 0.55×1250mm; Coating thickness (double-sided): 180g / m 2 .

[0094] (2) Unit speed: 130m / min; Mobile fan output power: 93KW.

[0095] (3) Coating condensation line height: 4.6m; Coating cooling rate: 28℃ / s.

[0096] (4) Coating pass rate: 100%; scrap rate: 0%.

[0097] Example 2

[0098] (1) Strip steel specifications: 0.75×1180mm; Coating thickness (double-sided): 200g / m 2 .

[0099] (2) Unit speed: 100m / min; Mobile fan output power: 88KW.

[0100] (3) Coating condensation line height: 4.7m; Coating cooling rate: 27℃ / s.

[0101] (4) Coating pass rate: 100%; scrap rate: 0%.

[0102] Example 3

[0103] (1) Strip steel specifications: 1.15×1000mm; Coating thickness (double-sided): 220g / m 2 .

[0104] (2) Unit speed: 95m / min; Mobile fan output power: 83KW.

[0105] (3) Coating condensation line height: 3.8m; Coating cooling rate: 28℃ / s.

[0106] (4) Coating pass rate: 100%; scrap rate: 0%.

[0107] Example 4

[0108] (1) Strip specifications: 1.85×1150mm; Coating thickness (double-sided): 180g / m 2 .

[0109] (2) Unit speed: 75m / min; Mobile fan output power: 100KW.

[0110] (3) Coating condensation line height: 2.5m; Coating cooling rate: 26℃ / s.

[0111] (4) Coating pass rate: 100%; scrap rate: 0%

[0112] Example 5

[0113] (1) Strip steel specifications: 2.2×1100mm; Coating thickness (double-sided): 180g / m 2 .

[0114] (2) Unit speed: 67m / min; Mobile fan output power: 105KW.

[0115] (3) Coating condensation line height: 2.5m; Coating cooling rate: 25℃ / s.

[0116] (4) Coating pass rate: 100%; scrap rate: 0%.

[0117] This invention has been applied to actual production, and the scrap rate of a certain steel product caused by poor coating adhesion and unqualified surface quality has been reduced from 0.66% to 0.13% annually.

[0118] This invention innovatively proposes to determine the cooling rate of the coating based on the height of the condensation line when the liquid coating solidifies into a solid coating, thereby achieving precise control of the cooling rate.

[0119] This invention achieves high-quality and stable production of ultra-thick coated aluminum-zinc-magnesium sheets by controlling the cooling rate of the strip in the post-cooling section. Without increasing equipment investment or large-scale modifications, this invention enables stable, high-quality, and efficient production of ultra-thick coated aluminum-zinc-magnesium products, greatly reducing production costs and ensuring stable unit operation and product quality that meets requirements.

[0120] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling the cooling rate of the coating during the production of ultra-thick coated aluminum-zinc-magnesium plates, characterized in that, This method specifically includes the following steps: 1) Set the condensation line as a downward-opening parabola, and the height of the condensation line is the distance from the air knife to the top of the condensation line, H, mm; 2) Measure the height of the condensation line in real time using a height gauge; 3) Control the height of the condenser wire by controlling the output power of the mobile fan in the cold section: The strip thickness is D, mm; the unit speed is V, m / min; ①D≤0.6mm, When 80m / min≤V≤120m / min, 4.0mm≤H≤4.5mm; When 120m / min < V ≤ 150m / min, 4.5 mm < H ≤ 5.0 mm; ② 0.6mm < D ≤ 1.0mm, When 80m / min≤V≤100m / min, 4.0mm≤H≤4.5mm; When 100m / min < V ≤ 135m / min, 4.5 mm < H ≤ 5.0 mm; ③ 1.0mm < D ≤ 1.4mm, When 60m / min≤V≤90m / min, 3.0mm≤H≤3.5mm; When 90 m / min < V ≤ 125 m / min, 3.5 mm < H ≤ 4.0 mm; ④ 1.4mm < D ≤ 1.8mm, When 55m / min≤V≤90m / min, 3.0mm≤H≤3.5mm; When 90 m / min < V ≤ 110 m / min, 3.5 mm < H ≤ 4.0 mm; ⑤ 1.8mm < D ≤ 2.0mm, When 50m / min≤V≤70m / min, 2.5mm≤H≤3.0mm; When 70m / min < V ≤ 100m / min, 2.0mm < H ≤ 2.5mm; ⑥2.0mm<D≤2.5mm, When 45m / min≤V≤65m / min, 2.5mm≤H≤3.0mm; When 65m / min < V ≤ 85m / min, 2.0mm < H ≤ 2.5mm; 4) Controlling the cooling rate by adjusting the height of the condensation line: Coating cooling rate V C ℃ / s; ① When D≤0.6mm, and 4.0≤H≤4.5, 30<V C ≤32; For D≤0.6mm, when 4.5<H≤5.0, 28≤V C ≤30; ② 0.6mm < D ≤ 1.0mm, when 4.0 ≤ H ≤ 4.5, 28 < V C ≤30; 0.6mm < D ≤ 1.0mm, when 4.5 < H ≤ 5.0, 25 ≤ V C ≤28; ③ When 1.0mm < D ≤ 1.4mm, and 3.0 ≤ H ≤ 3.5, 31 < V C ≤33; 1.0mm < D ≤ 1.4mm, when 3.5 < H ≤ 4.0, 27 ≤ V C ≤31; ④ When 1.4mm < D ≤ 1.8mm, and 3.0 ≤ H ≤ 3.5, 28 < V C ≤32; 1.4mm < D ≤ 1.8mm, when 3.5 < H ≤ 4.0, 24 ≤ V C ≤28; ⑤ 1.8mm < D ≤ 2.0mm, when 2.0 < H ≤ 2.5, 30 < V C ≤34; 1.8mm < D ≤ 2.0mm, when 2.5 < H ≤ 3.0, 25 < V C ≤30; ⑥ When 2.0mm < D ≤ 2.5mm, and 2.0 < H ≤ 2.5, 26 < V C ≤30; 2.0mm < D ≤ 2.5mm, when 2.5 < H ≤ 3.0, 23 < V C ≤26.

2. The method for controlling the cooling rate of the coating during the production of ultra-thick coated aluminum-zinc-magnesium plates according to claim 1, characterized in that, In step 2, a height scale is installed on the operating side frame of the movable cooling air box above the air knife.

3. The method for controlling the coating cooling rate in the production of ultra-thick coated aluminum-zinc-magnesium plates according to claim 1, characterized in that, In step 3, the width of the strip is 1000~1300mm.

4. The method for controlling the coating cooling rate in the production of ultra-thick coated aluminum-zinc-magnesium plates according to claim 1, characterized in that, In step 3, the output power of the mobile fan is 60~120KW.

5. The method for controlling the coating cooling rate in the production of ultra-thick coated aluminum-zinc-magnesium plates according to claim 1, characterized in that, In step 4, the coating thickness is 150~300 g / m. 2 .

6. The method for controlling the coating cooling rate in the production of ultra-thick coated aluminum-zinc-magnesium plates according to claim 5, characterized in that, The coating is a double-sided coating.

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