Manufacturing method of aluminum alloy pre-plating layer steel strip

Abstract

The invention discloses a manufacturing method of an aluminum alloy pre-plating steel strip, which comprises the following steps: (1) plating an aluminum-silicon layer on the surface of a strip steel substrate to obtain an aluminum-silicon plating steel strip; (2) carrying out alloying treatment on the aluminum-silicon coating steel strip in a cover type annealing furnace in a full-hydrogen protective atmosphere to obtain an aluminum alloy pre-coating steel strip; wherein the alloying treatment temperature ranges from 400 DEG C to 730 DEG C, and the alloying treatment time ranges from 0.5 h to 6 h. The high temperature resistance of the steel strip is further improved, and the steel strip can be used in the fields of automobile exhaust pipes, smoke exhaust pipelines and the like with high working temperature.

Description

Technical Field

[0001] The invention belongs to the field of cold rolling and is suitable for the production of aluminum-silicon coated steel plates. Background Art

[0002] Aluminum-silicon coating products are new high-corrosion-resistant coating products developed by Anshan Iron and Steel Co., Ltd. in 2023. They combine the excellent corrosion resistance and oxidation resistance of aluminum with the high strength of the substrate. Therefore, aluminum-silicon coated hot-formed steel plates have excellent atmospheric corrosion resistance, and their corrosion resistance is 8 to 10 times that of hot-dip galvanized steel plates with the same coating thickness. In addition, aluminum-silicon coated hot-formed steel also exhibits good high-temperature oxidation resistance, hot working formability, and excellent high-strength finished mechanical properties. Precisely because of its good comprehensive performance, the development of aluminum-silicon coated hot-formed steel products has been very rapid and is widely used in the automotive, construction, household appliances and other industries. However, automobile exhaust pipes and smoke exhaust ducts place higher requirements on the heat resistance of steel strips. Summary of the invention

[0003] To solve the problems of the prior art, the present invention provides a novel method for manufacturing an aluminum alloy pre-plated steel strip, including a process from steelmaking to the final product. The most critical control point is the temperature and time of the bell-type furnace heat treatment to improve the heat resistance of the steel strip.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A method for manufacturing an aluminum alloy pre-plated steel strip comprises the following steps:

[0006] (1) coating an aluminum-silicon layer on the surface of a strip steel substrate to obtain an aluminum-silicon coated steel strip;

[0007] The chemical composition of the strip steel substrate is calculated by mass percentage as follows: C: 0.001% to 0.80%, Si: 0.001% to 2.2%, Mn: 0.06% to 10.50%, P≤0.04%, S≤0.04%, Al: 0.02% to 3.00%, Ti≤0.20%, B≤0.005%, Cr: 0.03% to 0.70%, Mo: 0.01% to 1.60%, Cu≤0.70%, Ni: 0.15% to 1.2%, Nb≤0.08%, and the balance is Fe and unavoidable impurities;

[0008] The chemical composition of the aluminum silicon coating is calculated by mass percentage as follows: Al: 85% to 90%, Si: 0.5% to 15%, Ti: 0.03% to 0.50%, Re: 0.01% to 0.20%, Li: 0.05% to 3%, Cu: 0.1% to 5.0%, Fe: 0.03% to 1.0%, Mn: 0.5% to 3.0%, Ni: 0.5% to 4.0%, V: 0.01% to 0.5%, Zr: 0.5% to 1.0%, Cr: 0.1% to 1.0%, and the remainder is unavoidable impurities.

[0009] (2) The aluminum-silicon coated steel strip is alloyed in a hood annealing furnace in a full hydrogen protective atmosphere to obtain an aluminum alloy pre-coated steel strip; wherein the alloying treatment temperature is 400-730°C, preferably 500-680°C; and the time is 0.5-6h, preferably 2-4h.

[0010] Furthermore, in step (1), the strip steel substrate is a cold-rolled strip steel substrate, and the surface quality requirements are: no visually visible color difference, width and narrowness mark, roller mark, rust, emulsion residue and other quality defects. The surface roughness of the strip steel substrate Ra ≥ 2.0 μm.

[0011] Furthermore, in step (1), the plate shape inspection criteria of the raw material of the strip steel substrate after rolling are:

[0012] I. Requirements for the I value of the plate shape meter after rolling are shown in Table 1.

[0013] Table 1 Requirements for the mean value of I for each steel grade

[0014] Steel grade Mean I value S0-S4 thickness ≤1.0mm material 2.5 (S7\S8) 780 and above 15.0 S5\S6 5.0

[0015] II. Inspection and control standards for the physical plate shape of finished products after rolling are shown in Table 2.

[0016] Table 2 Inspection standards for physical plate shape after rolling

[0017]

[0018] Furthermore, in step (1), the thickness of the strip steel substrate is less than 2.30 mm and the width is less than 1550 mm.

[0019] Furthermore, in step (1), the thickness of the aluminum silicon coating is 40-200 g / m 2 .

[0020] Furthermore, in step (1), the process control of the aluminum silicon coating is as follows: the temperature of the steel strip entering the pot, the temperature of the plating solution and the process speed are controlled to coat the substrate, and then the plated substrate is controlled to cool; wherein the temperature of the steel strip entering the pot is 620-660°C, the temperature of the plating solution is 632-655°C, the speed of the unit is controlled to be not less than 60m / min, preferably 70-130m / min; the cooling rate is 21-32°C / s, and the temperature of the substrate after cooling is 265-290°C; the thickness range of the aluminum silicon coating (on both sides) is 40-200g / m 2 .

[0021] Furthermore, in order to ensure the adhesion of the coating, ensure that the coating weight meets the requirements and the surface quality of the coating, the strip entering the pot temperature, the plating solution temperature and the process speed shall comply with the provisions of Table 3.

[0022] Table 3 Strip steel feeding temperature, plating solution temperature and process speed requirements

[0023]

[0024] Furthermore, in step (1), during the process control of the aluminum-silicon coating, the air knife needs to be controlled; wherein the opening is 1.2-1.35 mm, the air knife medium is compressed air, and the flow rate is not less than 2600 m 3 / h; In order to effectively avoid aluminum flow corrugation defects, when specifying such products, the air knife height is between 650-1000mm; the air knife pressure is between 40-500mbar.

[0025] In order to effectively improve the toughness and formability of the coating, it is necessary to reasonably control the cooling rate after plating, which plays a decisive role in controlling the thickness of the alloy intermediate layer, controlling the adhesion of the coating and improving the toughness of the coating. According to the thickness change of the alloy layer between the coating and the substrate of the material analyzed in the experiment, the post-cooling process with a moderate thickness (2-4μm) of the alloy layer between the coating and the substrate is selected as the most optimized coating cooling rate control process scheme, taking into account the adhesion and formability of the coating.

[0026] Further, the unit speed is 80-135m / min, the strip running time is 11-19s, the strip temperature out of the plating solution is 650-660℃, the strip temperature after cooling is 265-290℃, and the cooling rate is 21-32℃ / s. The specific post-plating cooling process is shown in Table 5. The strip temperature out of the plating solution is the plating solution temperature.

[0027] Table 4 Post-plating cooling process parameters

[0028]

[0029] Furthermore, the opening degree of the middle part of the air knife width direction is 1.2±0.1, and the opening degree is gradually expanded towards both ends, each time expanding by 0.025±0.1. Specifically, in the air knife width direction, 0 represents the edge of one side of the air knife width direction, and 17 represents the edge of the other side of the air knife width direction, and then it is divided into 0-17 at equal intervals, and the air knife lip opening degree curve is optimized. The specific opening degree curve is shown in Table 4.

[0030] Table 5 Air knife lip opening curve

[0031]

[0032] Furthermore, in step (2), the aluminum-silicon coated steel strip is not subjected to passivation and oiling treatment, that is, the surface post-treatment state of the product off the production line of the aluminum-silicon coating unit should be non-passivation + non-oiling.

[0033] Furthermore, in step (2), the aluminum-silicon coated steel strip is coiled, and the steel coil is offline in a coiled state, and the coil weight is controlled at 7-28 tons.

[0034] Furthermore, in step (2), the aluminum-silicon coated steel strip is first cleaned and then alloyed. The cleaning operation is: the steel coils off the aluminum-silicon coating unit are transported to the cold rolling cleaning unit, and then welded by a narrow lap welder and then conventionally degreased and cleaned in the cleaning unit to remove the grease and impurities remaining on the surface. The cleaned or uncleaned steel coils can be alloyed by bell furnace heating.

[0035] Furthermore, in step (2), the aluminum alloy pre-coated steel strip taken out of the hood furnace after being heated is cleaned. Specifically, the aluminum alloy pre-coated steel strip taken out of the hood furnace after being heated is transported to a cleaning unit for cleaning to eliminate surface residues generated during the heating process. The degreasing agent of the cleaning unit is conventional degreasing cleaning.

[0036] Furthermore, in step (2), the cleaned aluminum alloy pre-plated steel strip is transported to a single-frame leveling unit for leveling to improve the strip shape. The rolling force is required to be 300 to 400 tons, and the strip elongation is controlled at 0.2-0.5%. At the same time, the surface roughness of the leveling work roll is controlled between 2-3 μm.

[0037] Furthermore, in step (2), the flattened aluminum alloy pre-plated steel strip is transported to a cold rolling and re-coiling unit for slitting, and is trimmed, oiled, and other processes are performed according to customer requirements.

[0038] Furthermore, the aluminum alloy pre-plating layer is a three-layer structure, including from bottom to top an inner alloy layer, a middle aluminum silicon layer, and an outer alloy layer, wherein the inner alloy layer is close to the substrate.

[0039] Furthermore, for the final product, the thickness of the outer alloy layer (starting from the steel plate surface and measured from the steel plate surface to the inside of the steel plate) is required to be not less than 4 μm, preferably 4.5-6.0 μm. At the same time, the mass percentage of Fe element in the outer alloy layer is not less than 50%, preferably 55-70%.

[0040] Beneficial effects of the present invention:

[0041] The present invention develops a new type of aluminum alloy pre-plated steel strip. The surface of the aluminum alloy plated steel strip is iron-aluminum alloy, and the coating is a three-layer structure. See the microstructure photo for details. The high temperature resistance of the steel strip is further improved, and it can be used in fields with high working temperatures such as automobile exhaust pipes and smoke exhaust pipes.

[0042] The heat-resistant temperature of the aluminum alloy pre-plated steel strip developed by the present invention is 1000-1100°C, while the heat-resistant temperature of ordinary aluminum-plated steel plates is generally 800-900°C, so it is more than 200°C higher than that of ordinary aluminum-plated steel plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the three-layer structure of the aluminum-silicon coated steel strip coating prepared in Example 3. DETAILED DESCRIPTION

[0044] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0045] Examples 1-6

[0046] A method for manufacturing an aluminum alloy pre-plated steel strip comprises the following steps:

[0047] (1) An aluminum-silicon layer is plated on the surface of a steel strip substrate, and an aluminum-silicon plated steel strip is obtained by controlling the temperature of the steel strip substrate entering a pot, the temperature of the plating solution and the process speed, the air knife control and the post-plating cooling process control; the steel strip substrate is a cold-rolled substrate, and the surface roughness of the substrate Ra is ≥ 2.0 μm.

[0048] (2) The aluminum-silicon coated steel strip is subjected to alloying treatment in a bell-type annealing furnace in a full hydrogen protective atmosphere to obtain an aluminum alloy pre-coated steel strip; wherein:

[0049] 1) The aluminum-silicon coated steel strip is not passivated or oiled, that is, the surface post-treatment status of the products off the aluminum-silicon plating unit should be non-passivated + non-oiled.

[0050] 2) The aluminum-silicon coated strip steel is coiled and the steel coil is offline in a coiled state with the coil weight controlled at 7-28 tons.

[0051] 3) The aluminum-silicon coated steel strip is alloyed in a bell-type annealing furnace in a full hydrogen protective atmosphere, and the heating temperature and time are controlled.

[0052] 3) The aluminum alloy pre-plated steel strip taken out of the bell-type furnace after heating is transported to the cleaning unit for cleaning to eliminate the surface residues generated during the heating process. The degreasing agent of the cleaning unit is conventional degreasing cleaning.

[0053] 4) The cleaned aluminum alloy pre-plated steel strip is transported to the single-stand leveling unit for leveling, the rolling force and strip elongation are controlled, and the strip shape is improved. At the same time, the surface roughness of the leveling work roll is controlled between 2-3μm.

[0054] 5) The flattened aluminum alloy pre-coated steel strip is transported to the cold rolling re-coiling unit.

[0055] Among them, the chemical composition of the strip steel substrate, calculated by mass percentage, is shown in Table 6, and the balance is Fe and unavoidable impurities; the chemical composition of the aluminum silicon coating is shown in Table 7, and the balance is unavoidable impurities; the specific process parameters and results in the manufacturing method are shown in Table 8.

[0056] Figure 1 The three-layer structure of the coating in the aluminum-silicon coated steel strip prepared in Example 3 includes an inner alloy layer, a middle aluminum-silicon layer, and an outer alloy layer from bottom to top, and the inner alloy layer is close to the strip steel substrate.

[0057] Table 6 Chemical composition of the steel substrate in Examples 1-6

[0058] Example C / ％ Si / % Mn / % P / ％ S / ％ Al / ％ Ti / % B / ％ Cr / ％ Mo / % Cu / % Ni / % Nb / % 1 0.035 0.004 0.214 0.006 0.008 0.028 0.000 0.001 0.039 0.012 0.011 0.152 0.001 2 0.046 0.003 0.213 0.010 0.009 0.029 0.000 0.001 0.037 0.011 0.013 0.155 0.001 3 0.002 0.004 0.222 0.007 0.007 0.029 0.000 0.001 0.035 0.013 0.016 0.157 0.002 4 0.065 0.003 0.221 0.010 0.011 0.023 0.000 0.001 0.035 0.011 0.012 0.154 0.002 5 0.052 0.006 0.229 0.010 0.011 0.023 0.000 0.001 0.032 0.012 0.010 0.155 0.002

[0059] Table 7 Chemical composition of aluminum silicon coating in Examples 1-6

[0060] Example Al / ％ Si / % Ti / % Re / % Li / % Cu / % Fe / % Mn / % Ni / % V / ％ Zr / ％ Cr / ％ 1 88.192 9.113 0.219 0.065 0.069 0.248 0.069 0.514 0.611 0.021 0.721 0.125 2 88.083 9.105 0.217 0.063 0.078 0.365 0.071 0.526 0.671 0.019 0.654 0.133 3 88.065 9.032 0.236 0.071 0.075 0.351 0.082 0.572 0.712 0.017 0.643 0.127 4 88.223 9.003 0.231 0.074 0.067 0.422 0.074 0.523 0.623 0.021 0.594 0.126 5 88.107 9.107 0.229 0.077 0.085 0.415 0.072 0.541 0.652 0.015 0.565 0.124

[0061] Table 8 Process parameters and results of the preparation method in Examples 1-6

[0062]

[0063]

Claims

1. A method for manufacturing an aluminum alloy pre-plated steel strip, characterized in that: The steps include: (1) coating an aluminum-silicon layer on the surface of a strip steel substrate to obtain an aluminum-silicon coated steel strip; The chemical composition of the strip steel substrate is calculated by mass percentage as follows: C: 0.001% to 0.80%, Si: 0.001% to 2.2%, Mn: 0.06% to 10.50%, P≤0.04%, S≤0.04%, Al: 0.02% to 3.00%, Ti≤0.20%, B≤0.005%, Cr: 0.03% to 0.70%, Mo: 0.01% to 1.60%, Cu≤0.70%, Ni: 0.15% to 1.2%, Nb≤0.08%, and the balance is Fe and unavoidable impurities; The chemical composition of the aluminum silicon coating is calculated by mass percentage as follows: Al: 85% to 90%, Si: 0.5% to 15%; Ti: 0.03% ~ 0.50%, Re: 0.01% ~ 0.20%, Li: 0.05% ~ 3%, Cu: 0.1% ~ 5.0%, Fe: 0.03% ~ 1.0%, Mn: 0.5% ~ 3.0%, Ni: 0.5% ~ 4.0%, V: 0.01% ~ 0.5%, Zr: 0.5% ~ 1.0%, Cr: 0.1% ~ 1.0%, the balance is unavoidable impurities; (2) The aluminum-silicon coated steel strip is alloyed in a bell-type annealing furnace in a full hydrogen protective atmosphere to obtain an aluminum alloy pre-coated steel strip; wherein the alloying treatment temperature is 400-730° C. and the time is 0.5-6 h.

2. The manufacturing method according to claim 1, characterized in that: In step (1), the process control of the aluminum silicon coating is as follows: the temperature of the steel substrate entering the pot is 620-660°C, the plating solution temperature is 632-655°C, the unit speed is not less than 60m / min, the cooling rate is 21-32°C / s, and the temperature of the substrate after cooling is 265-290°C; the thickness of the aluminum silicon coating is 40-200g / m 2 .

3. The manufacturing method according to claim 2, characterized in that: In step (1), during the process control of the aluminum-silicon coating, the air knife needs to be controlled, the air knife opening is 1.2-1.35 mm, the air knife medium is compressed air, and the flow rate is not less than 2600m 3 / h; air knife height is 650-1000mm; air knife wind pressure is 40-500mbar.

4. The manufacturing method according to claim 1, characterized in that: In step (1), the strip steel substrate is a cold-rolled strip steel substrate, and the surface roughness of the strip steel substrate Ra is ≥ 2.0 μm.

5. The manufacturing method according to claim 1, characterized in that: In step (1), the thickness of the strip steel substrate is less than 2.30 mm and the width is less than 1550 mm.

6. The manufacturing method according to claim 1, characterized in that: In step (2), the aluminum-silicon coated steel strip is not subjected to passivation and oiling treatment; the aluminum-silicon coated steel strip is coiled, and the coil weight is controlled at 7-28 tons.

7. The manufacturing method according to claim 1, characterized in that: In step (2), the aluminum-silicon coated steel strip is first cleaned and then alloyed.

8. The manufacturing method according to claim 1, characterized in that: In step (2), the aluminum alloy pre-plated steel strip obtained by alloying treatment is cleaned; the cleaned aluminum alloy pre-plated steel strip is leveled, and the elongation is controlled at 0.2-0.5%; the surface roughness of the leveling work roll is controlled between 2-3μm; and the leveled aluminum alloy pre-plated steel strip is re-rolled.

9. The manufacturing method according to claim 1, characterized in that: The aluminum alloy pre-plating layer is a three-layer structure, including from bottom to top an inner alloy layer, a middle aluminum silicon layer, and an outer alloy layer, wherein the inner alloy layer is close to the strip steel substrate.

10. The manufacturing method according to claim 9, characterized in that: The thickness of the inner alloy layer is 2-4 μm, and the thickness of the outer alloy layer is not less than 4 μm; the mass percentage of Fe element in the outer alloy layer is not less than 50%.

Images