Slurry-blasted hot-rolled base hot-dip aluminized steel strip

Abstract

Preparation of coated steel comprising the steps of hot or cold rolling, slurry blasting and coating. A hot or cold rolling step in which a steel ingot is rolled to form a steel strip. A slurry blasting step comprising slurry blasting at least one side of the steel strip. A coating step following slurry blasting comprising coating the steel strip with an aluminum based coating.

Description

Technical Field

[0001] This application claims priority to U.S. Provisional Application No. 63 / 329,084, filed Apr. 8, 2022, entitled “Slurry-Blasted Hot-Roll-Based Hot Dip Aluminated Steel Strip,” the disclosure of which is incorporated herein by reference.

Background Art

[0002] The present invention relates to aluminized carbon steel. Aluminization can be performed on steel to coat one or more surfaces of the steel with an aluminum-based coating. Such an aluminum-based coating can be alloyed with other components depending on the situation. For example, in Type 1, aluminum can be alloyed with silicon. Such alloying may be desirable to improve certain mechanical properties of the coating. In other situations, Industrial Pure it can be used without alloying aluminum. Such Industrial Pure an aluminized coating may sometimes be referred to as a Type 2 aluminized coating.

[0003] Depending on the situation, either a Type 1 or Type 2 aluminized coating with high adhesion may be desirable. Many factors can contribute to improving adhesion, but surface treatment of the steel substrate is one factor that can contribute to adhesion. In hot-rolled steel or cold-rolled steel, scale may accumulate on the surface of the steel during hot rolling or cold rolling. The presence of scale on the surface of the steel substrate is generally undesirable because during the aluminum treatment, the scale can introduce contaminants at the steel-aluminum interface, thereby preventing complete adhesion. Therefore, it may be desirable to remove scale from the surface of hot-rolled steel or cold-rolled steel before the aluminum treatment. The following are prior art documents related to the invention of this application (including documents cited in the international phase after the international filing date and documents cited when the application entered the national phase in other countries): (Prior art document) (Patent Document) (Patent Document 1) International Publication No. 2022 / 029033 (Patent Document 2) U.S. Patent Application Publication No. 2008 / 108281 (Patent Document 3) International Publication No. 2014 / 146540 [Overview of the project] [Problems that the invention aims to solve]

[0004] One possible method of scale removal that can be used may include pickling, in which a chemical agent is used to consume scale on the surface of a steel substrate. Depending on the situation, pickling may be combined with other mechanical scale removal processes such as peening, grinding, and / or others. While these processes are relatively efficient at removing scale, they tend to produce non-uniform or uneven surface preparations. Therefore, it may be desirable to eliminate scale removal processes such as pickling and / or mechanical scale removal and employ other processes that have comparable efficiency to pickling and / or mechanical scale removal processes but provide a more uniform and / or uniform surface preparation. [Brief explanation of the drawing]

[0005] [Figure 1] This figure shows the surface appearance of the aluminized coating on the first sample, which is pickled before aluminization. [Figure 2] This figure shows the surface appearance of the aluminized coating on the second sample, which is pickled before aluminization. [Figure 3] This figure shows the surface appearance of the aluminized coating on the third sample, which is slurry blasted before aluminization. [Figure 4] This figure shows the surface appearance of the aluminized coating on the fourth sample, which is slurry blasted before aluminization. [Figure 5] This figure shows the fifth and sixth samples after bending adhesion tests of the aluminized coating, which were slurry blasted before aluminization. [Modes for carrying out the invention]

[0006] This invention relates to aluminized steel. Aluminized steel may be desirable to provide corrosion resistance comparable to stainless steel at a lower cost. Furthermore, aluminized steel may exhibit heat reflectivity. Therefore, aluminized steel may be desirable in operating environments where corrosion and / or high temperatures are possible.

[0007] Aluminum-treated coatings are sometimes referred to as Type 1 and Type 2 aluminum-treated coatings. In Type 1 aluminum-treated coatings, aluminum can be alloyed with silicon to form an aluminum-silicon alloy on one or more surfaces of steel. Such aluminum-silicon alloys in Type 1 aluminum-treated coatings may contain a balance of approximately 5 to 11% silicon and aluminum with impurities. The presence of silicon (Si) can control the formation of an intermetallic compound layer between the steel substrate and the coating during the molten coating process. For example, the presence of silicon may contribute to slowing the growth of the intermetallic compound layer during the molten coating process. Limiting the growth of the intermetallic compound layer in the as-coated state may be desirable to improve the heat resistance of the aluminum-treated coating. Therefore, in situations where heat resistance is desired, a Type 1 aluminum-treated coating may be preferable.

[0008] In contrast, Type 2 aluminized coatings do not contain additional alloying elements. Industrial PureIt contains aluminum. In the absence of additional alloying elements, the formation of the intermetallic compound layer is less controllable during the hot-dip plating process compared to type 1 aluminized coatings. However, in the absence of additional alloying elements, aluminized coatings have higher corrosion resistance compared to type 1 aluminized coatings. Therefore, type 2 aluminized coatings are desirable in situations where corrosion resistance takes precedence over heat resistance. It should be understood that aspects of this disclosure relate to either type 1 aluminized coatings or type 2 aluminized coatings. Accordingly, the principles described herein can be applied to both type 1 and type 2 aluminized coatings, even when the aluminizing process is referred to without specifically mentioning type 1 or type 2 aluminized coatings.

[0009] The hot-rolling or cold-rolling process can cause scale buildup on the surface of hot-rolled or cold-rolled steel strips. The presence of scale on the surface of hot-rolled or cold-rolled steel strips before aluminization is generally undesirable because it can lead to contamination of the coating itself and / or the intermetallic layer between the steel substrate and the aluminized coating. As a result of such contaminants, the adhesion strength between the steel substrate and the aluminized coating may decrease, potentially resulting in uneven, mottled, or poor surface quality of the aluminized coating.

[0010] Several processes for removing scale can include pickling or mechanical removal processes. Pickling, in particular, can be desirable because it allows for efficient and continuous in-line processing after hot or cold rolling and before winding of the steel strip. However, due to variations in the operating conditions of the pickling process, the surface of the pickled steel strip may be uneven or inconsistent, even if the scale is effectively removed. Such uneven or inconsistent surface treatment can be observed anywhere on the steel strip after winding, but it is observed to be concentrated at the ends of the coil.

[0011] When steel strips undergo molten aluminum treatment, such uneven or inconsistent conditions on the strip's surface can result in an uneven or mottled aluminum coating. This uneven or mottled aluminum coating may be a result of insufficient wetting properties of the strip's surface during molten aluminum treatment. Therefore, certain processes may be desirable to improve the surface treatment of hot-rolled or cold-rolled steel strips prior to molten aluminum treatment.

[0012] Aspects of this disclosure relate to the use of slurry blasting for preparing one or more surfaces of hot-rolled or cold-rolled steel strips for molten aluminum treatment. Slurry blasting is a process that involves mixing an abrasive with a pressurized fluid (e.g., water) and then directing the mixture toward a surface at high speed. Slurry blasting has not been previously used for molten aluminum treatment due to challenges associated with the cost and time requirements of moving an entire steel coil to perform the test. In this embodiment, slurry blasting can be performed on hot-rolled or cold-rolled steel strips at one or more points in the steel production process. For example, as will be described in more detail below, slurry blasting may be performed immediately after hot-rolling or cold-rolling and before coiling. Alternatively, slurry blasting may be performed independently after coiling and before molten aluminum treatment. In either case, slurry blasting may be performed in connection with either type 1 or type 2 aluminum treatment. Alternatively, in some versions, slurry blasting may be performed in connection with other forms of coating, such as galvanizing or a zinc-based coating.

[0013] In a first aspect of the present disclosure, slurry blasting is performed in a multi-step process. In the multi-step process, a coil of hot-rolled steel strip (or alternatively cold-rolled steel strip) can be unwound from a wound shape into a shape that is not longitudinally wound. Next, the unwound steel strip can be subjected to slurry blasting. During the slurry blasting step, scale can be removed from one or more surfaces of the steel strip. The control of the slurry blasting process can be performed in real time by an operator. Specifically, the operator can adjust operating parameters such as the feed rate and pressure in real time to sufficiently remove scale from one or more surfaces of the steel strip.

[0014] After the slurry blasting step is completed, the steel strip is dried, Wind it up again which is possible. Then, It was re-wound the steel strip is transferred to a molten aluminum coating line, where It was re-wound the steel strip is unwound again and can be subjected to hot-coated molten aluminizing using molten aluminum having type 1 or type 2 characteristics.

[0015] In some versions of the first aspect of the present disclosure, the slurry blasting process can be performed continuously. For example, Rewind can be performed at one end of the line, winding and can be performed at the opposite end of the line. Then, the slurry blasting process can be performed between the Rewind end and the winding end of the line. In this configuration, Rewind and Rewinding of the coil are performed simultaneously, so the steel strip can be continuously slurry blasted.

[0016] In a second aspect of the present disclosure, slurry blasting is performed in an integrated process (or a single process). In the integrated process, the slurry blasting process can be combined with the molten aluminizing process. Specifically, the steel strip can be transferred to the molten aluminizing line after hot rolling (or alternatively cold rolling). Optionally, in some versions, pickling or other scale removal can be performed in relation to hot rolling. In other versions, other forms of scale removal including pickling may be completely omitted.

[0017] When the coiled steel strip is transferred to the molten aluminizing line, the coil can be unwound and fed into the molten aluminizing line. Then, slurry blasting may be performed as part of the pre-cleaning process used in the molten aluminizing line. The slurry blasting step may be performed to remove scale from one or more surfaces of the steel strip. The control of the slurry blasting process may be performed in real time by an operator. Specifically, the operator may adjust operating parameters such as feed rate and pressure in real time to sufficiently remove scale from one or more surfaces of the steel strip.

[0018] After the slurry blasting step, the steel strip may be further fed into a molten aluminum treatment line to reheat the steel strip, and then the steel strip may be immersed in a molten aluminum treatment tank using molten aluminum having type 1 or type 2 characteristics. When the aluminum treatment is completed, the coated steel strip Rewind it up again may be.

[0019] Example 1 Samples of hot-rolled steel strip coils were prepared. The hot-rolled steel strip coils were pickled. After pickling, the steel strips were hot-coated with molten aluminum and then rewound. In this example, the hot-coated molten aluminum treatment refers to an aluminum treatment process in which the steel strip is first heated to approximately the temperature of the molten aluminum bath and then the steel strip is immersed in the molten aluminum bath.

[0020] Figures 1 and 2 show the surface of the aluminum-treated coating obtained after pickling treatment prior to aluminum treatment. Specifically, Figure 1 shows a first sample in which the surface of the aluminum-treated coating is relatively non-uniform, particularly in the left-hand region of the page. Similarly, Figure 2 shows a second sample in which the surface of the aluminum-treated coating is relatively non-uniform, particularly in the right-hand region of the page.

[0021] Example 2 Additional samples of hot-rolled steel strip coils were prepared. The hot-rolled steel strip coils were subjected to slurry blasting. After slurry blasting, the steel strips were subjected to hot molten aluminum coating. In this example, slurry blasting was performed in the aluminization line, before the reheating furnace. After molten aluminum coating, the steel strips were re-wound.

[0022] Figures 3 and 4 show the surface of the aluminized coating obtained after using slurry blasting before aluminization. Specifically, Figure 3 shows a third sample in which the surface of the aluminized coating is substantially uniform, particularly compared to the first and second samples shown in Figures 1 and 2, respectively. Similarly, Figure 4 shows a fourth sample in which the surface of the aluminized coating is also substantially uniform, particularly compared to the first and second samples shown in Figures 1 and 2, respectively. Thus, it is shown that using slurry blasting instead of pickling to descale before molten aluminization substantially improves the uniformity of the coating appearance. The degree of improvement in surface appearance by slurry blasting instead of pickling was unexpected. Furthermore, the performance in removing or otherwise reducing thick scale, such as scale encountered at the ends of coils, was unexpectedly good.

[0023] Example 3 The steel strip coil from Example 2 described above was further tested. Specifically, the coil was unwound, and samples were taken from the head end (5th sample) and the tail end (6th sample). The obtained samples were then subjected to a bending adhesion test. The specific bending adhesion test used included a bending radius that varied with the thickness of the substrate.

[0024] Figure 5 shows the results of the bending adhesion test. The fifth sample is shown in the upper row, and the sixth sample is shown in the lower row. As can be seen from the figure, the slurry-blasted steel strip of Example 2 showed acceptable adhesion at both the head and tail ends of the coil. This demonstrates that acceptable adhesion performance of aluminum-treated coatings can be obtained by using slurry blasting rather than pickling for scale removal before molten aluminum treatment.

[0025] Example 4 The coated steel was prepared according to the following process. a. Hot or cold rolling of steel ingots to form steel strips; b, slurry blasting of at least one surface of the steel strip; and c. After slurry blasting, the steel strip is coated with an aluminum-based coating.

[0026] Example 5 The coated steel is prepared according to the method of Example 4, which further includes winding the steel strip into a coil, unwinding the steel strip before the slurry blasting step, and winding the steel strip before the step of coating the steel strip with an aluminum-based coating.

[0027] Example 6 The coated steel was prepared according to the method of Example 5, and the slurry blasting step was performed on the steel strip. to wrap Rewind, again This was done continuously while reeling in.

[0028] Example 7 Coating steel was prepared according to the method of Example 4, which further includes the steps of winding a steel strip into a coil and transferring the coiled steel strip to an aluminization line, and the slurry blasting step was performed in the aluminization line as part of a pre-cleaning step before coating the steel strip with an aluminum-based coating.

[0029] Example 8 Coated steel was prepared according to one or more of the methods in Examples 4 to 7, which include a step of hot-rolling or cold-rolling a steel ingot, followed by a step of pickling the steel strip after hot-rolling or cold-rolling.

[0030] Example 9 A coated steel prepared according to one or more of the methods in Examples 4 to 7, wherein the step of slurry blasting the steel strip is performed from the steel strip Removed scale Visual observation Based on this, coated steel includes adjusting the feed rate and pressure related to slurry blasting in real time.

[0031] Example 10 A coated steel prepared according to one or more of the methods in Examples 4 to 9, wherein the aluminum-based coating comprises a type 1 or type 2 aluminized coating.

[0032] Example 11 A coated steel prepared according to one or more of the methods of Examples 4 to 10, wherein the aluminum-based coating contains 5 to 11% silicon.

[0033] Example 12 A coated steel prepared according to one or more of the methods in Examples 4 to 11, wherein the step of slurry blasting a steel strip includes the use of an abrasive medium, and the abrasive medium comprises a mixture of water and abrasive particles.

[0034] Example 13 A coated steel prepared according to one or more of the methods in Examples 4 to 12, wherein the step of slurry blasting the steel strip includes the step of slurry blasting both sides of the steel strip.

[0035] Example 14 The coated steel was prepared using the following coating line system. The coating line system includes an aluminization section containing a molten bath containing molten aluminum. A slurry blast section is configured to direct a high-speed polishing mixture towards one or more surfaces of the steel strip, and the slurry blast section may be operably positioned before the aluminization section and may be configured to act as a pre-cleaning process before the steel strip is aluminized through the aluminization section.

[0036] Example 15 Coated steel was prepared using the coating line system of Example 14. The coating line system further includes a reheating furnace, and a slurry blasting section is operably positioned in front of the reheating furnace.

[0037] Example 16 Coated steel was prepared using the coating line system of Example 14 or 15. The slurry blast section includes feed rate control and pressure control, both of which are configured to allow real-time adjustment to control the removal of scale from one or more surfaces of the steel strip.

[0038] Example 17 Coated steel was prepared using one or more coating line systems from Examples 14 to 16. The aluminization section and the slurry blast section were configured to operate in conjunction with each other in continuous operation.

[0039] Example 18 Coated steel was prepared using one or more coating line systems from Examples 14 to 17. The slurry blast section was configured to remove scale from the first and second surfaces of the steel strip.

Claims

1. A method for manufacturing coated steel, (a) The step of hot-rolling or cold-rolling a steel ingot to form a steel strip, (b) The step of slurry blasting at least one side of the steel strip, (c) After the slurry blasting step, the steel strip is coated with an aluminum-based coating. It has, The step of slurry blasting at least one side of the steel strip includes adjusting the feed rate and pressure associated with slurry blasting in real time based on visual observation of the scale removed from the steel strip, thereby providing a uniform surface treatment to the steel strip. method.

2. The method according to claim 1, further, The steps include winding up the steel strip, The step of unwinding the steel strip before the slurry blasting step, The step of rewinding the unwinded steel strip before the step of coating the steel strip with an aluminum-based coating, A method having.

3. A method according to claim 2, wherein the slurry blasting step is performed continuously between the step of unwinding the steel strip and the step of rewinding the steel strip.

4. The method according to claim 1, further, The steps include winding up the steel strip, The steps include transferring the wound steel strip to an aluminum processing line and It has, The slurry blasting step is performed in the aluminum processing line as part of a pre-cleaning process, prior to the step of coating the steel strip with an aluminum-based coating.

5. A method according to any one of Claims 1 to 4, wherein the step of hot-rolling or cold-rolling the steel ingot comprises the step of pickling the steel strip after hot-rolling or cold-rolling.

6. The method according to Claim 1, wherein the aluminum-based coating comprises a type 1 or type 2 aluminized coating, The aluminized coating of type 1 comprises an alloy of aluminum and silicon. The aluminized coating of type 2 contains industrial pure aluminum, method.

7. The method according to Claim 1, wherein the aluminum-based coating comprises 5 to 11% silicon.

8. A method according to Claim 1, wherein the step of slurry blasting the steel strip comprises using an abrasive medium comprising a mixture of water and abrasive particles.

9. A method according to Claim 1, wherein the step of slurry blasting the steel strip includes the step of slurry blasting both sides of the steel strip.

10. A system for preparing coated steel, (a) an aluminization section including a molten bath containing molten aluminum, (b) A slurry blast section configured to guide a high-speed abrasive mixture toward one or more surfaces of a steel strip, The slurry blast section is operably positioned before the aluminization section and is configured to perform a pre-cleaning treatment before the steel strip is aluminized through the aluminization section. The slurry blasting section includes feed rate control and pressure control, both of which are configured to allow real-time adjustments to control the removal of scale from one or more surfaces of the steel strip. system.

11. The system according to claim 10, further comprising a reheating furnace, wherein the slurry blasting section is operably positioned in front of the reheating furnace.

12. The system according to claim 10, wherein the aluminizing section and the slurry blasting section are configured to operate with respect to each other in continuous operation.

13. The system according to claim 10, wherein the slurry blast section is configured to remove scale from a first surface and a second surface of a steel strip.

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