THIN METAL STRIP CONTINUOUS CASTING METHOD USING MOMENTUM FLOW DISTRIBUTION

Abstract

A thin metal strip continuous casting method using momentum flow distribution, comprising the steps of: adjusting the position of a flow distribution device (2), and starting a double-roller thin strip continuous casting apparatus; molten metal (3) forming a uniform sheet-shaped molten metal flow (4) having an initial momentum after the molten metal (3) passes through the flow distribution device; the sheet-shaped molten metal flow entering a molten pool (5) at a superheat degree of 50-100 C. and an initial velocity of 0.5-2 m/s, wherein the flow distribution device is spaced apart from the molten pool; under the action of the initial velocity of the molten metal and in the molten pool, forming a whirlpool, which is adjacent to surfaces of two cooling rollers and has a momentum stirring action; and completing the solidification of the molten metal under the momentum stirring action of the whirlpool along with the rotation of the two cooling rollers. In the method, a whirlpool, which is adjacent to surfaces of cooling rollers and has a momentum stirring action, is formed in a molten pool by means of the kinetic energy of molten metal, such that equiaxed crystals can be prepared when a superheat degree is as high as 50-100 C., and the proportion of equiaxed crystals can be increased to 100%, thereby refining crystal grains and alleviating segregation.

Claims

1. A thin metal strip continuous casting method using momentum flow distribution, comprising the following steps of: (1) adjusting the position of a flow distribution device, and starting a double-roller thin strip continuous casting device; (2) molten metal entering the flow distribution device, and the molten metal forming a sheet-shaped molten metal flow which is uniform in an axial direction and has an initial momentum after the molten metal passes through the flow distribution device; (3) the sheet-shaped molten metal flow entering a molten pool at a superheat degree of 50-100 C. and an initial velocity of 0.5-2 m/s, where the flow distribution device is spaced apart from the molten pool, so that the flow distribution device does not come into contact with the molten pool; (4) under the action of the initial velocity of the molten metal, in the molten pool, forming a whirlpool which is adjacent to surfaces of two cooling rollers and has a momentum stirring action; and (5) completing the solidification of the molten metal under the momentum stirring action of the whirlpool along with the rotation of the two cooling rollers to obtain a thin metal strip, where the solidification structure of the thin metal strip is a uniform and fine equiaxed crystal structure.

2. The thin metal strip continuous casting method according to claim 1, wherein the double-roller thin strip continuous casting device is an inclined double-roller thin strip continuous casting device comprising an upper cooling roller and a lower cooling roller; the upper cooling roller and the lower cooling roller are obliquely arranged, and a roller gap is formed between the upper cooling roller and the lower cooling roller; the flow distribution device is arranged above the lower cooling roller.

3. The thin metal strip continuous casting method according to claim 2, wherein the flow distribution device comprises: an inlet section opened upward, which is configured to receive the molten metal; a vertical outlet section connected to the inlet section, a continuous strip-shaped outlet being formed on the bottom of the vertical outlet section to output the sheet-shaped molten metal flow; and a flow guide plate, which is connected to one side of the vertical outlet section and configured to guide the sheet-shaped molten metal flow to flow out.

4. The thin metal strip continuous casting method according to claim 3, wherein the length of the vertical outlet section is 3-10 times of the thickness of the vertical outlet section, the length of the flow guide plate is 5-10 times of the thickness of the vertical outlet section, and the distance from the intersection of the flow guide plate and the vertical outlet section to the bottom of the vertical outlet section is 1.5-3 times of the thickness of the vertical outlet section.

5. The thin metal strip continuous casting method according to claim 4, wherein the length of the vertical outlet section is 5-7 times of the thickness of the vertical outlet section, the length of the flow guide plate is 7-8 times of the thickness of the vertical outlet section, and the distance from the intersection of the flow guide plate and the vertical outlet section to the bottom of the vertical outlet section is 2-2.5 times of the thickness of the vertical outlet section.

6. The thin metal strip continuous casting method according to claim 4, wherein the angle between the connecting line of the output endpoint of the flow distribution device with the axis of the lower cooling roller and a vertical line is 0-70, the angle between the connecting line of the axes of two cooling rollers and the vertical line is 30-90, and the angle is less than the angle ; the difference between the angle between the plate surface of the flow guide plate and a horizontal line and the angle is 0-5.

7. The thin metal strip continuous casting method according to claim 6, wherein the angle between the connecting line of the output endpoint of the flow distribution device with the axis of the lower cooling roller and the vertical line is 20-60, the angle between the connecting line of the axes of two cooling rollers and the vertical line is 60-80, and the angle is less than the angle ; the difference between the angle between the plate surface of the flow guide plate and the horizontal line and the angle is 0-5.

8. The thin metal strip continuous casting method according to claim 1, wherein the double-roller thin strip continuous casting device is a vertical double-roller thin strip continuous casting device comprising a first cooling roller and a second cooling roller which are arranged horizontally; the flow distribution device is arranged above the position where the first cooling roller and the second cooling roller are symmetrical, and a roller gap is formed therebetween.

9. The thin metal strip continuous casting method according to claim 8, wherein the flow distribution device comprises: an inlet section opened upward, which is configured to receive the molten metal; and a vertical outlet section connected to the inlet section, a continuous strip-shaped outlet being formed on the bottom of the vertical outlet section to output the sheet-shaped molten metal flow.

10. The thin metal strip continuous casting method according to claim 9, wherein the length of the vertical outlet section is 3-10 times, preferably 5-7 times, of the thickness of the vertical outlet section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a schematic diagram of the thin metal strip continuous casting device in Embodiment 1;

[0021] FIG. 2 is a stereoscopic diagram of the flow distribution device in Embodiment 1;

[0022] FIG. 3 is a sectional view of the flow distribution device in Embodiment 1;

[0023] FIG. 4 is a sectional view of FIG. 3 along A-A;

[0024] FIG. 5 is a schematic diagram of the momentum distribution and the whirlpool in the molten pool in Embodiment 1;

[0025] FIG. 6 is a schematic diagram of the thin metal strip continuous casting device in Embodiment 2;

[0026] FIG. 7 is a stereoscopic diagram of the flow distribution device in Embodiment 2;

[0027] FIG. 8 is a sectional view of the flow distribution device in Embodiment 2;

[0028] FIG. 9 is a sectional view of FIG. 8 along B-B; and

[0029] FIG. 10 is a schematic diagram of the momentum distribution and the whirlpool in the molten pool in Embodiment 2.

DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions and advantages of the present application clearer, the embodiments of the present application will be described below in detail with reference to the accompanying drawings. It is to be noted that the embodiments in the present application and the features in the embodiments can be arbitrarily combined with each other if not conflicted.

[0031] The present application relates to a thin metal strip continuous casting method using momentum flow distribution, including the following steps of: [0032] (1) adjusting the position of a flow distribution device, and starting a double-roller thin strip continuous casting device; [0033] (2) molten metal entering the flow distribution device, and the molten metal forming a sheet-shaped molten metal flow which is uniform in an axial direction and has an initial momentum after the molten metal passes through the flow distribution device, where the axial direction refers to the axial direction of double rollers; [0034] (3) the sheet-shaped molten metal flow entering a molten pool at a superheat degree of 50-100 C. and an initial velocity of 0.5-2 m/s, where the flow distribution device is spaced apart from the molten pool, so that the flow distribution device does not come into contact with the molten pool; [0035] (4) under the action of the initial velocity of the molten metal, in the molten pool, forming a whirlpool which is adjacent to surfaces of two cooling rollers and has a momentum stirring action; and [0036] (5) completing the solidification of the molten metal under the momentum stirring action of the whirlpool along with the rotation of the two cooling rollers to obtain a thin metal strip, where the solidification structure of the thin metal strip is a uniform and fine equiaxed crystal structure.

[0037] The momentum flow distribution in the present application requires the molten metal to have a high initial velocity, thereby ensuring that the momentum entering the molten pool is high and the momentum stirring effect in the molten pool is obvious, and, the formation of the equiaxed crystal structure is promoted by the strong momentum stirring effect of the whirlpool in the molten pool. The momentum stirring effect of the whirlpool is beneficial to strengthen the heat exchange between the molten metal and the cooling rollers, improve the temperature uniformity of all parts of the molten pool, reduce the temperature gradient and increase the supercool degree and the nucleation rate. The momentum stirring of the whirlpool can break the dendritic crystals, thereby suppressing the formation and growth of columnar crystals and refining crystal grains. Moreover, the momentum stirring of the whirlpool can also make components more uniform, thus alleviating segregation. The whirlpool is developed more fully, the effects of refining the solidification structure, increasing the proportion of equiaxed crystals and alleviating segregation is better. The momentum stirring effect can realize the formation of equiaxed crystals at a superheat degree of 50-100 C. and can effectively avoid the blockage at the tundish and the water port. Moreover, since the sheet-shaped molten metal flow entering the molten pool is uniform and continuous, the whirlpool formed in the molten pool is kept uniform along the axis of the cooling rollers, thereby realizing uniform solidification and improving the surface quality.

Embodiment 1

[0038] As shown in FIGS. 1-5, the thin metal strip continuous casting method using momentum flow distribution in the present application may be implemented by an inclined double-roller thin strip continuous casting device. The method includes the following steps. [0039] (1) The position of a flow distribution device is adjusted, and a double-roller thin strip continuous casting device is started. [0040] (2) Molten metal enters the flow distribution device, and the molten metal forms a sheet-shaped molten metal flow which is uniform in an axial direction and has an initial momentum after the molten metal passes through the flow distribution device. [0041] (3) The molten metal flow enters a molten pool formed by two cooling rollers and two side seals, at a superheat degree of 50-100 C. and an initial velocity of 0.5-2 m/s along the surface of the lower roller, where the flow distribution device is spaced apart from the molten pool and the flow distribution device does not come into contact with the molten pool. [0042] (4) Under the action of the initial velocity of the molten metal, in the molten pool, a whirlpool which is adjacent to surfaces of two cooling rollers and has a momentum stirring action is formed. [0043] (5) The solidification of the molten metal is completed under the momentum stirring action of the whirlpool along with the rotation of the two cooling rollers to obtain a thin metal strip, where the solidification structure of the thin metal strip is a uniform and fine equiaxed crystal structure.

[0044] As shown in FIGS. 1-4, the inclined double-roller thin strip continuous casting device includes a first cooling roller 1 located on the lower side and a second cooling roller 6 located on the upper side. The first cooling roller 1 and the second cooling roller 6 are obliquely arranged, and a roller gap is formed between the first cooling roller 1 and the second cooling roller 6. The flow distribution device 2 is arranged above the first cooling roller 1, and the molten metal 3 flows out of the flow distribution device 2 to form a sheet-shaped molten metal flow 4 which is uniform in the axial direction and has an initial momentum. The angle between the connecting line of the output endpoint of the flow distribution device 2 with the axis of the lower cooling roller and a vertical line is 0-70, preferably 20-60, for example 40; the angle between the connecting line of the axes of two cooling rollers and the vertical line is 30-90, preferably 60-80, for example 70; and, the angle is less than the angle . The initial momentum may be adjusted by the height between the liquid level of the tundish or flow groove and the flow distribution device. In order to ensure the full development of the whirlpool, the flow distribution device does not come into contact with the molten pool. The sheet-shaped molten metal flow enters the roller gap between the first cooling roller 1 and the second cooling roller 6 at an initial velocity of 0.5-2 m/s along the surface of the first cooling roller to form a molten pool 5, and the subsequent sheet-shaped molten metal flow forms whirlpool momentum in the molten pool 5. The first cooling roller 1 and the second cooling roller 6 rotate synchronously in opposite directions, and the roller velocity may be 0.1-3 m/s. The solidification of the molten metal is completed under the momentum stirring action of the whirlpool. The prepared thin metal strip 7 is extracted from the roller gap between the first cooling roller 1 and the second cooling roller 6, and the solidification structure of the thin metal strip 7 is a uniform and fine equiaxed crystal structure.

[0045] The flow distribution device 2 includes an inlet section 8 opened upward, which is configured to receive the molten metal from the tundish; a vertical outlet section 9 connected to the inlet section 8, a continuous strip-shaped outlet being formed on the bottom of the vertical outlet section 9 to output the sheet-shaped molten metal flow; and, a flow guide plate 10, which is connected to one side of the vertical outlet section 9 and configured to guide the sheet-shaped molten metal flow to flow out. The length l.sub.1 of the vertical outlet section 9 is 3-10 times, preferably 5-7 times of the thickness t.sub.1 of the vertical outlet section 9, the length l.sub.2 of the flow guide plate 10 is 5-10 times, preferably 7-8 times of the thickness t.sub.1 of the vertical outlet section 9, and the distance b from the intersection of the flow guide plate 10 and the vertical outlet section 9 to the bottom of the vertical outlet section 9 is 1.5-3 times, preferably 2-2.5 times of the thickness t.sub.1 of the vertical outlet section 9. The angle between the surface of the flow guide plate 10 and the horizontal line is =+, where is the angle deviation between and and may be 0-5. By the combination of the size relationship and the angle relationship, the sheet-shaped molten metal flow flowing into the roller surface along the flow guide plate can form a good momentum stirring effect in the molten pool, and the whirlpool stirring required for preparing 100% equiaxed crystals is realized.

[0046] In a comparative example, the molten metal enters the molten pool space along the surface of the lower roller at a superheat degree of 70 C. and an initial velocity of 1 m/s, and a whirlpool which is adjacent to the surfaces of two cooling rollers and has a momentum stirring action is formed in the molten pool. Under the action of the momentum stirring of the whirlpool, the solidification of the molten metal is completed, and a thin metal strip is prepared. The solidification structure is a uniform and fine 100% equiaxed crystal structure, and the size of crystal grains is 80 m.

Embodiment 2

[0047] As shown in FIGS. 6-10, the thin metal strip continuous casting method using momentum flow distribution in the present application may be implemented by a vertical double-roller thin strip continuous casting device. This method includes the following steps. [0048] (1) The position of a flow distribution device is adjusted, and a double-roller thin strip continuous casting device is started. [0049] (2) Molten metal enters the flow distribution device through a tundish or flow groove, and the molten metal forms a sheet-shaped molten metal flow which is uniform in an axial direction and has an initial momentum after the molten metal passes through the flow distribution device. [0050] (3) The molten metal flow enters a molten pool formed by two cooling rollers and two side seals, at a superheat degree of 50-100 C. and an initial velocity of 0.5-2 m/s along the symmetrical plane of adjacent surfaces of the two cooling rollers, where the flow distribution device is spaced apart from the molten pool. [0051] (4) Under the action of the initial velocity of the molten metal, in the molten pool, a whirlpool which is adjacent to surfaces of two cooling rollers and has a momentum stirring action is formed. [0052] (5) The solidification of the molten metal is completed under the momentum stirring action of the whirlpool along with the rotation of the two cooling rollers to obtain a thin metal strip, where the solidification structure of the thin metal strip is a uniform and fine equiaxed crystal structure.

[0053] As shown in FIGS. 7-9, the vertical double-roller thin strip continuous casting device includes a first cooling roller 11 and a second cooling roller 16 which are arranged horizontally, and a roller gap is formed between the first cooling roller 11 and the second cooling roller 16. The flow distribution device 12 is arranged above the position where the first cooling roller 11 and the second cooling roller 16 are symmetrical, and the molten metal 13 flows out of the flow distribution device 12 to form a sheet-shaped molten metal flow 14 which is uniform in the axial direction and has an initial momentum. The flow distribution device 12 includes an inlet section 18 opened upward, which is configured to receive the molten metal from the tundish or flow groove; and, a vertical outlet section 19 connected to the inlet section 18, a continuous strip-shaped outlet being formed on the bottom of the vertical outlet section 19 to output the sheet-shaped molten metal flow 14. The length l.sub.3 of the vertical outlet section 19 is 3-10 times, preferably 5-7 times of the thickness t.sub.2 of the vertical outlet section 19. The sheet-shaped molten metal flow 14 enters the roller gap between the first cooling roller 11 and the second cooling roller 16 at an initial velocity of 0.5-2 m/s to form a molten pool 15, and the subsequent sheet-shaped molten metal flow 14 forms whirlpool momentum in the molten pool 15. The first cooling roller 11 and the second cooling roller 16 synchronously rotate in opposite directions, and the roller velocity may be 0.1-3 m/s. Under the action of the momentum stirring of the whirlpool, the solidification of the molten metal is completed. The prepared thin metal strip 17 is extracted from the roller gap between the first cooling roller 11 and the second cooling roller 16, and the solidification structure of the thin metal strip 17 is a uniform and fine equiaxed crystal structure.

[0054] In a comparative example, the molten metal enters the molten pool space along the intermediate position above the two cooling rollers at a superheat degree of 60 C. and an initial velocity of 0.8 m/s, and a whirlpool which is adjacent to the surfaces of the two cooling rollers and has a momentum stirring action is formed in the molten pool. Under the action of the momentum stirring of the whirlpool, the solidification of the molten metal is completed, and a thin metal strip is prepared. The solidification structure is a uniform and fine 100% equiaxed crystal structure, and the size of crystal grains is 100 m.

[0055] The thin metal strip continuous casting method provided by the present application is simple and convenient to operate, and can increase the proportion of equiaxed crystals of the thin metal strip solidification structure without changing the original material components and reducing the superheat heat. The proportion of equiaxed crystals can be as high as 100%. Thus, the crystal grains can be refined, and segregation can be alleviated. The present application can be applied to near-net-shape continuous casting of various thin metal strips such as steel and nonferrous metal.

[0056] Although the implementations of the present application are described above, the contents descried are only implementations used to understand the present application and not intended to limit the present application. Without departing from the spirit and scope disclosed by the present application, any person skilled in the art to which the application belongs can make any modifications and alterations to the forms and details of implementation. However, the protection scope of the present application shall still be subject to the scope defined by the appended claims.