JPH04371351A - Horizontal type continuous casting method - Google Patents

Abstract

PURPOSE:To provide the method, by which a high quality cast billet can be stably produced for long time. CONSTITUTION:Stepping degree in drawing mark part formed on surface of the cast billet 1 closely related to the quality of cast billet, is measured with ultrasonic thickness meter 11, etc., and the cast billet is cast while adjusting cooling condition of a cooling mold 12 so that the above stepping degree becomes a prescribed degree obtaining a high quality cast billet 1. As the quality of cast billet is judged by measuring a stepping degree in the drawing mark part, the quality of cast billet can be exactly and quickly decided for long time. Further, as the above stepping degree is controlled by adjusting the cooling condition of cooling mold 12, control of the stepping on the surface of cast billet, i.e., improvement of the quality of cast billet can be easily executed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal continuous casting method capable of stably producing high quality ingots over a long period of time.

0002

2. Description of the Related Art In the horizontal continuous casting method, as shown in FIG. The molten metal 5 supplied from the cooling mold 1
This is a casting method in which the ingot 1 is cooled and solidified in the ingot 2 to form an ingot 1, the ingot 1 is pulled out horizontally by pinch rolls 14, and the pulled out ingot 1 is cooled to room temperature by a secondary cooling device 15. . This horizontal continuous casting method allows equipment to be installed on the floor, so compared to the vertical continuous casting method in which the ingot is pulled out vertically,
It has the advantages of low construction cost and easy work, and is widely used for casting various metal materials. By the way, in such a horizontal continuous casting method, the ingot is drawn out by repeating drawing and stopping alternately.The reason why the ingot is drawn out in this way is that the molten metal 5 is drawn out as shown in the solidification form in FIG. In order to allow the thin initial solidified layer 4 formed by touching the inner surface of the graphite mold 8 to grow while stopping the drawing of the ingot 1, and to prevent defects from occurring in the solidified layer due to friction with the inner surface of the mold during drawing. It is. If this initial solidified layer is thin, it will fall down to the molten metal side during drawing, creating shrinkage cavities, and if it is too thick, the amount of solidification shrinkage will become large, and the solidified layer will be too far away from the mold, making cooling ineffective. As a result, the solidified layer is heated by the molten metal inside, causing sweating of the low melting point metal. Therefore, controlling the initial solidification layer to an appropriate thickness is an important point in producing high-quality ingots.

0003

[Problems to be Solved by the Invention] However, the solidification form in such a horizontal continuous casting method, especially the thickness of the initial solidified layer, is influenced by casting conditions such as the temperature of the molten metal supplied and the cooling capacity of the mold. However, since the above-mentioned casting conditions change from moment to moment, there is a problem in that the quality of the obtained ingot deteriorates over time. Furthermore, defects that occur during the initial stage of solidification are generally so minute that they cannot be detected visually, and they become larger during the subsequent rolling process. Methods of enlarging the defects by bending or etching the ingots are used, but these detection methods take time to produce results, and during that time, a large number of defective ingots are produced. There was a problem in that productivity decreased significantly. or,
A method has been proposed in which the surface temperature of the ingot being produced is continuously measured and the solidification form is estimated based on the temperature pattern to determine the quality of the ingot. However, the solidification form and the surface temperature of the ingot are not necessarily one pair. In addition, when measuring the surface temperature of an ingot using a non-contact method using an infrared thermometer, the emissivity changes depending on the oxidation state of the ingot surface. In both cases, it has been impossible to accurately measure the surface temperature of the ingot over a long period of time because the contact pressure changes depending on the unevenness of the ingot surface. Furthermore, the thickness of the initial solidified layer is as shown in Figure 4.
As shown in Figure 2, it clearly appears in the extracted heat amount pattern of the mold, and when the initial solidification layer is thin, it becomes a gentle curve with a low peak (pattern A), and when the initial solidification layer is thick, it becomes a sharp curve with a high peak (pattern C). In the former case, the solidified shell is thin due to weak cooling, and this thin solidified shell collapses toward the molten metal during withdrawal, creating a shrinkage cavity between the inner surface of the mold and the newly poured molten metal. Or, the thin solidified layer may break and become floating, generating coarse crystals. In the latter case, cooling is strong, and a gap is too large between the initially solidified layer and the mold, making cooling ineffective and causing defects such as sweating of the low melting point metal and remelting of the solidified layer on the surface of the ingot. Because of this, we measured the extracted heat pattern of the mold and found that it was A.
A method was devised in which the cooling conditions were controlled so that the B pattern was obtained, which was between the C pattern and the C pattern. However, in this method, in order to measure the extracted heat amount pattern of the mold, the extracted heat amount Q and the mold temperature are measured at two points in the thickness direction of the mold, and these temperatures Ta and Tb are calculated using the following formula, Q = λ ( Ta-
Tb)/d (in the formula, λ is the thermal conductivity of the mold material, and d is the distance between the temperature measurement points). It was something.

0004

[Means for Solving the Problems] In view of the above situation, the present invention has conducted intensive research and has established a close relationship between the size of the step of the drawing mark formed on the surface of the ingot every drawing period and the quality of the ingot. After discovering that there is, and proceeding with further research, we have completed the present invention. That is, in the present invention, one end of a cooling mold with both ends open is attached to the side wall of a casting furnace storing molten metal so as to communicate with the casting furnace, and the molten metal supplied from the casting furnace is cooled and solidified within the cooling mold. In the horizontal continuous casting method, in which the ingot is drawn horizontally from the other end of the cooling mold by repeating pulling and stopping alternately, the difference in level of the drawing mark part formed on the surface of the ingot every drawing cycle. This method is characterized by measuring the size of the step and adjusting the cooling conditions of the cooling mold so that the size of the step falls within a predetermined range. In the present invention, as shown in FIG. 5, the size of the step 3 of the pull-out mark 2 portion formed on the surface of the ingot 1 at each pull-out cycle is measured, and the size of the step 3 is determined by
By adjusting the cooling conditions of the mold, casting is controlled within a predetermined range to obtain a high quality ingot free of defects such as cracks.

[0005] The mechanism by which a withdrawal mark, that is, a step, is formed on the surface of an ingot every withdrawal cycle will be explained in detail below with reference to the drawings. FIGS. 6A to 6C are partially enlarged explanatory views showing the solidification form immediately before being drawn out, respectively. The solidification form shown in Figure A is a case where the thickness of the tip of the initially solidified layer 4 immediately before being pulled out is thin, and when the ingot 1 is pulled out, the tip of the initially solidified layer 4 collapses inward. The molten metal 5 enters around the solidified layer at the tip and solidifies to form a secondary solidified layer 6, and between this secondary solidified layer 6 and the earlier initial solidified layer (referred to as the old solidified layer 7 after withdrawal). A step 3 is formed. The size of this step 3 is slightly larger because the old solidified layer 7 falls inward, and is 0.2 to 0.3 mm in the case of 8% phosphor bronze alloy.
It will be about the same size. In this case, the cooling of the cooling mold is strengthened to increase the thickness of the initially solidified layer 4. The solidification form shown in Figure B is the case where the tip of the initial solidified layer 4 is formed thickly, and because the amount of solidification shrinkage of the old solidified layer 7 is large, the step 3 between it and the secondary solidified layer 6 is 0. .3mm or more. In addition, in the ingot 1, there is a large gap between the old solidified layer 7 and the inner surface of the mold 8, so cooling from the mold becomes ineffective, and sweating of low melting point metal occurs in the old solidified layer 7, and a re-melted part 9 occurs in the solidified layer. . In this case, cooling of the mold is weakened to reduce the thickness of the initially solidified layer 4. The solidification form shown in Figure C is when the thickness of the tip of the initial solidification layer 4 is formed to an appropriate thickness.
The step 3 is smaller than the one explained in Figures A and B above, and is 0.
．． It will be 2 mm or less. In this case, since the initial solidified layer 4 has an appropriate thickness, the above-mentioned shrinkage cavities and perspiration do not occur, and the ingot is healthy.

[0006] The step of the above-mentioned pull-out mark part is 0.2 mm.
For those exceeding 0.3 mm and less than 0.3 mm (Figure 6 A), pattern A of the extracted heat amount pattern shown in Figure 4 is used, for those 0.3 mm or more (Figure 6 B), use pattern C, and for those 0.2 mm or less. (FIG. 6C) shows the B pattern. In the method of the present invention, for each alloy to be cast, the range of the size of the step at the pull-out mark part that will yield an ingot of good quality is determined, and the size of the step of the ingot to be produced is measured online. The cooling conditions of the mold are adjusted so that this measurement value falls within the range of the size of the step, and the cooling conditions of the mold are adjusted based on the measurement of the size of the step and this measurement result. The adjustment can be automatically controlled by programming a series of processes into a computer according to a flowchart as shown in FIG. The flowchart is designed so that judgments at step value boundaries are made in a fuzzy manner. In the method of the present invention, when casting a wide plate-shaped ingot, the solidification form may differ in the width direction. In this case, the cooling mold is divided into a plurality of zones in the width direction, and each zone is Casting is carried out by measuring the step size of the ingot, dividing the cooling channel of the cooling mold according to the zones, and adjusting the cooling conditions such as the amount of cooling water for each zone. It is best to measure the level difference and adjust the cooling conditions of the mold separately for the front and back sides of the ingot. In addition, a non-contact thickness meter using ultrasonic waves is suitable for measuring the level difference in the pull-out mark portion.

[0007]

[Operation] In the method of the present invention, the quality of the produced ingot is determined by measuring the size of the step of the withdrawal mark formed on the surface of the ingot at each withdrawal cycle, so the quality of the ingot can be judged. done quickly and accurately. Furthermore, since the size of the step is controlled by adjusting the cooling conditions of the mold, the step on the surface of the ingot can be easily controlled, that is, the quality of the ingot can be easily improved.

[0008]

[Examples] The present invention will be explained in detail below using examples. Example 1 A plate-shaped ingot of an 8% phosphor bronze alloy was continuously cast by the horizontal continuous casting method illustrated in FIG. The casting conditions are casting temperature 1
The temperature was 135° C., and the casting speed was 160 mm/min (drawing 0.5 seconds, stopping 2.0 seconds, one drawing distance 6.7 mm, number of drawing cycles 24 times/minute). The cross-sectional dimensions of the ingot 1 were 15 mm thick and varied in width. The cooling mold 12 used was a graphite mold 8 having a height of 50 mm and a length of 300 mm, with copper coolers 10 each having a height of 50 mm and a length of 250 mm arranged above and below. The width of the mold 12 was varied depending on the width of the ingot to be cast. The cooling water flowing into the cooler 10 was piped so that it could be adjusted separately for the upper and lower parts. When casting a wide ingot, the cooling water passage of the cooler 10 is divided into a plurality of zones in the width direction, and the piping is arranged so that the water amount can be adjusted individually in each zone. An ultrasonic thickness gauge 11 was placed at a distance of 1 m from the mold outlet to measure the difference in level between the upper and lower surfaces of the ingot 1. When a plurality of cooling zones were provided in the width direction, the level difference was measured on the ingot surface corresponding to the central portion of each cooling zone. The measurement of the step size of the ingot and the adjustment of the cooling conditions based on the results were carried out using a computer according to the flowchart shown in FIG. That is, the step thickness of the upper and lower surfaces of the ingot is input into a computer as the 2nth and 2n+1st data, respectively, and this is pooled for 10 minutes to calculate the average value. If this average value is 0.2 mm or less, Casting continued under the same conditions. When the average value exceeds 0.2 mm and is less than 0.3 mm, increase the amount of cooling water to increase the thickness of the coagulated layer 4, and when the average value exceeds 0.3 mm, reduce the amount of cooling water to increase the thickness of the coagulated layer 4. Check the effect of the above operation every 2 minutes, and if the size of the step is 0.2 mm or less after 10 minutes, continue casting under those conditions and check the effect of the above operation every 2 minutes. If it exceeded 0.2 mm, the above operation was repeated again. Casting was continued in this manner for 100 hours. The amount of cooling water was determined using the relationship diagram between the level difference and the amount of extracted heat shown in FIG. 8 and the amount of cooling water. Comparative Example 1 The temperature of the upper and lower surfaces of the ingot was continuously measured using an infrared thermometer, and the amount of water in the cooler was adjusted so that each temperature fell within a predetermined temperature range that would yield a healthy ingot. Casting was performed in the same manner as in Example 1, except for casting. Samples were cut out from each ingot thus obtained and subjected to a bending test. After every 20 hours of casting, a total of 30 samples were taken, 5 samples each from the front and back of the center of each of the three equal parts in the width direction. The results are shown in Table 1.

[0009]

[Table 1]

As is clear from Table 1, the method of the present invention (
Nos. 1 to 7) all have large bending angles and are of excellent quality.
Moreover, there was extremely little change over time. NO1~
Regarding No. 4, as the ingot width increases, the bending angle of the samples taken from the left and right ends of the ingot decreases slightly compared to the center sample; This is because the cooling conditions for the entire mold were adjusted at once by measuring only the thickness of the step in the center part, although there was a slight difference in the solidification form between the two molds.As seen in Nos. 5 to 7, This can be improved by dividing the cooling water passage of the cooler into a plurality of zones in the width direction and adjusting each zone individually. On the other hand, in the comparative example (NO8), the bending angle initially showed a high value, but gradually decreased. This is because the surface of the ingot changed color and the emissivity changed, causing errors in the measured temperature. Although the example of casting an 8% phosphor bronze alloy has been described above, it goes without saying that the method of the present invention can also be applied to casting other copper alloys and aluminum alloys.

[0011]

[Effect] As described above, in the method of the present invention, the quality of the ingot can be determined quickly and accurately by measuring the size of the step formed on the surface of the ingot, and based on this determination result, the quality of the ingot can be determined quickly and accurately. Since the quality can be easily improved by adjusting the amount of cooling water, the production yield is improved, which has a significant industrial effect.

[Brief explanation of drawings]

FIG. 1 is a process explanatory diagram showing an embodiment of the method of the present invention.

FIG. 2 is a process explanatory diagram of a conventional horizontal continuous casting method.

FIG. 3 is an explanatory diagram of a solidification form in a horizontal continuous casting method.

FIG. 4 is an explanatory diagram of an extracted heat amount pattern of a graphite mold.

FIG. 5 is an explanatory diagram of pull-out marks formed on the surface of the ingot.

FIG. 6 is a partially enlarged explanatory diagram of the solidification form in the horizontal continuous casting method.

FIG. 7 is an example of a flowchart when the method of the present invention is implemented using a computer.

FIG. 8 is a diagram showing the relationship between the level difference, the amount of extracted heat, and the amount of cooling water.

[Explanation of symbols]

1 Ingot 2 Drawer mark 3 Steps 4 Initial solidification layer 5 Molten metal 6 Secondary solidified layer 7 Old solidified layer 8 Graphite mold 9 Remelting section 10 Copper cooler 11 Ultrasonic thickness gauge 12 Cooling mold 13 Casting furnace 14 Pinch roll 15 Secondary cooling device

Claims (2)

[Claims] Claim 1: One end of a cooling mold with both ends open is attached to the side wall of a casting furnace storing molten metal so as to communicate with the casting furnace, and the molten metal supplied from the casting furnace is cooled and solidified within the cooling mold. In the horizontal continuous casting method, in which the ingot is drawn out horizontally from the other end of the cooling mold by repeating pulling and stopping alternately, the difference in level of the drawing mark part formed on the surface of the ingot at each drawing cycle is A horizontal continuous casting method characterized by measuring the size of the step and adjusting the cooling conditions of the cooling mold so that the size of the step falls within a predetermined range. 2. The cooling mold is divided into a plurality of zones in the width direction, and the size of the level difference in the drawer mark portion of the ingot produced in each zone is measured, and the cooling channel of the cooling mold is divided into a plurality of zones. Claim 1 characterized in that the cooling condition of the cooling mold is adjusted for each zone by dividing the cooling mold according to the zone.
The horizontal continuous casting method described.