TWI622434B - Caster and method of producing the same - Google Patents

Abstract

The invention relates to a method for manufacturing a continuous casting embryo and a flat steel embryo. The manufacturing method first provides a molten alloy steel liquid, and the molten alloy steel liquid is subjected to a continuous casting process to produce a flat steel embryo. In the solidification step, the molten alloy steel is gradually solidified from the outer surface to the central portion. When the center solidification rate of the semi-coagulated embryo is greater than or equal to 0.8 and less than 1.0, the semi-coagulated embryo is subjected to a press roll step. Among them, the pressure roller step is performed by a roller roller and a fixed roller. The region between the two trigeminal points of the resulting cast embryo does not have segregation and shrinkage.

Description

Casting embryo and manufacturing method thereof

The invention relates to a casting embryo and a manufacturing method thereof, and in particular to a manufacturing method capable of eliminating segregation and shrinkage of a core portion of a casting.

The conventional continuous casting process can use a plurality of rolls or a plurality of sets of rolls to properly press the incompletely solidified castings to obtain a good quality casting. This is called soft reduction. Process. However, during the solidification process, the dendritic bridge of the embryonic core is semi-coagulated, and the molten steel is not replenished to the core of the semi-coagulated embryo, or the gap between the secondary dendrites is solidified, and the core of the cast embryo is prepared. Shrinkage holes, or smaller diameter microvoids, are formed, and structural defects are formed in the core. Generally, the shrinkage defects are easily polished by the naked eye after being easily ground or corroded on the cross section of the steel. The microvoids are small defects of less than 1 mm in size, and the cross section of the steel embryo cannot be visually discerned even if it is ground and corroded. The traditional soft reduction process is mainly due to the small amount of reduction, which mainly compensates for the shrinkage of the cooling and solidification of the casting. It can only achieve a certain degree of improvement for the traditional shrinkage defects, but it does not improve the smaller and dense microvoids. effect.

When the casting embryo is to be made into a steel material such as a large-sized bar steel or an ultra-thick steel plate, since the thickness of the finished product is large, the rolling ratio is lowered, so that the rolling process cannot heal defects such as shrinkage holes and micro-holes in the core portion of the casting. These defects reduce the fatigue life and tensile strength of the steel core. Even when steel is used in low-temperature environments, these defects can embroil the core structure and reduce the low-temperature impact toughness of the steel, so that it can not meet the specifications of steel and become the bottleneck of the production technology of high-grade large-size bar steel and ultra-thick steel plate. .

In order to eliminate the shrinkage holes and micro-holes in the core of the casting embryo, the semi-condensing embryo is lightly pressed by a plurality of pairs of rollers or a plurality of sets of rollers by a dynamic soft reduction process to eliminate casting. Shrinkage and microvoids in the heart of the embryo. Among them, the dynamic soft reduction system has multiple pairs of rollers or multiple sets of roller sets, and the distance between them (ie, the spacing of the pair of pressure roller rollers) can be dynamically adjusted to meet the dynamic soft pressure of different steel grades and casting speeds. Under the demand. In the light pressure semi-coagulation of the embryo, the dynamic soft reduction system compensates the cooling shrinkage of the steel embryo and the solidification shrinkage of the steel by applying a small pressing force to the casting embryo by multiple pairs of roller or multiple sets of rollers. The amount is to avoid loose tissue after the dendritic bridge, and also avoid the high concentration of molten steel in the front end after solidification and shrinkage, and solidify to form segregation structure. However, the cost of the system and the maintenance cost of the dynamic soft reduction system are relatively high, and better use of the technology is required to achieve an improvement effect.

The other method is to control the bulge in the continuous casting process, and then use the dynamic soft pressing process to extrude the incompletely solidified casting embryo to eliminate most of the shrinkage holes in the core of the casting embryo, but this method cannot Improve the micro-holes. In addition, in the continuous casting process, another method uses a dynamic soft reduction system to perform bulge control, and at the solidification end, the casting embryo is greatly depressed to eliminate The shrinkage hole and the micro-hole of the heart of the casting embryo. However, the casting machine needs to have a dynamic soft reduction system to control the convex belly, and the load of the pressing is extremely large, and the general casting machine needs to be modified.

In view of the above, it is not necessary to provide a casting embryo and a method of manufacturing the same to improve the defects of the conventional casting embryo and its manufacturing method.

Therefore, an aspect of the present invention provides a method for manufacturing a cast embryo by performing a press roll step on a semi-coagulated embryo to eliminate segregation and shrinkage of the core portion of the cast embryo, thereby improving casting. The density of the heart of the embryo.

Another aspect of the present invention is to provide a casting embryo which is produced by the aforementioned method.

According to an aspect of the present invention, a method of manufacturing a cast embryo is proposed. The manufacturing method first provides an alloy steel liquid, and the alloy steel liquid is subjected to a continuous casting process. Among them, the continuous casting process first performs a solidification step on the alloy steel liquid to form a semi-condensed embryo. When the center solidification rate of the semi-coagulated embryo is greater than or equal to 0.8 and less than 1.0, the semi-coagulated embryo is subjected to a press roll step to obtain a cast embryo. The pressure roller step is carried out using a roll roller and a fixed roller. The aforementioned continuous casting process excludes the bulge step, and the press roll step is excluded using a dynamic soft reduction system.

According to an embodiment of the invention, the pressing roller has an extrusion distance of from 4 mm to 20 mm.

According to another embodiment of the invention, the aforementioned roller roll is an upper roller and the fixed roller is a lower roller.

According to still another embodiment of the present invention, the aforementioned roller roll is a male roll or a flat roll, and the fixed roll is a flat roll.

According to still another embodiment of the present invention, the width of the surface of the pressing roller of the convex roller is larger than the pitch of the two three-pronged points of the casting blank.

According to still another embodiment of the present invention, the difference in width and pitch is greater than 0 mm and less than or equal to 200 mm.

According to another aspect of the invention, a casting embryo is proposed. This casting is produced by the aforementioned method, and the region between the two trigeminal points of the cast embryo does not have segregation and shrinkage.

Applying the casting embryo of the present invention and a manufacturing method thereof, the pressing roller step is performed by a pair of rollers, and the semi-coagulated embryo is pressed by the pressing roller of the pressing roller to extrude the molten steel in the semi-coaged embryo core The liquid, and the upper and lower crusts, which are almost completely contacted, completely heal the shrinkage holes and the microvoids, and produce the steel embryos with no segregation, shrinkage and micropore defects in the core, thereby improving the low temperature impact of the core of the steel plate. toughness.

100‧‧‧ method

110‧‧‧Provide the steps of providing alloy steel

120‧‧‧Continuous casting process

121‧‧‧Steps for the coagulation step

123‧‧‧Steps for the pressure roller step

130‧‧‧Steps for making the embryo

200‧‧‧Pressure roller device

210‧‧‧Pressure roller

211‧‧‧Press roll surface

220‧‧‧Fixed roller

230‧‧‧casting embryo

230a‧‧ Direction

231‧‧‧Three-pronged point

233‧‧‧ semi-condensed embryo

W‧‧‧Width

D‧‧‧ spacing

α ₁ /α ₂ /α ₃ /α ₄ ‧‧‧ angle

For a more complete understanding of the embodiments of the invention and the advantages thereof, reference should be made to the description below and the accompanying drawings. It must be emphasized that the various features are not drawn to scale and are for illustrative purposes only. The relevant schema description is as follows:

FIG. 1 is a flow chart showing a method of manufacturing a cast embryo according to an embodiment of the present invention.

2A is a schematic perspective view of a pressure roller device when a pressure roller step is performed in accordance with an embodiment of the present invention.

2B is a schematic cross-sectional view taken along the axis of the roll of the press roll in accordance with an embodiment of the present invention.

[Fig. 3A] and [Fig. 3B] respectively show radiation detection images of a cast test piece according to an embodiment of the present invention and a comparative example.

[Fig. 4A] and [Fig. 4B] respectively show etched tissue images of a cast test piece according to an embodiment of the present invention and a comparative example.

The making and using of the embodiments of the invention are discussed in detail below. However, it will be appreciated that the embodiments provide many applicable inventive concepts that can be implemented in a wide variety of specific content. The specific embodiments discussed are illustrative only and are not intended to limit the scope of the invention.

Please refer to FIG. 1 , which is a flow chart showing a method of manufacturing a cast embryo according to an embodiment of the present invention. Method 100 provides alloy steel liquid first, as shown in step 110. Then, the alloy steel liquid is subjected to a continuous casting process 120. In the continuous casting process 120, the alloy steel liquid is first subjected to a solidification step to form a semi-coagulated embryo, as shown in step 121. Among them, the semi-coagulated embryo refers to the surface solidified to form a crust, but the alloy steel liquid of the semi-coagulated embryonic core is still in a molten state and has not yet solidified.

As the roller of the continuous casting process is conveyed, and the temperature of the semi-condensed embryo is lowered, when the central solid fraction of the semi-condensed embryo is greater than or equal to 0.8 and less than 1.0, the semi-condensed embryo is pressed. In the step, the cast embryo of the present invention can be obtained, as shown in steps 123 and 130. In a real In the embodiment, the step of pressing the rolls is preferably carried out at a central solidification rate of 0.8 to 0.95, and more preferably at a central solidification rate of 0.8 to 0.9.

In one embodiment, the step of pressing is performed by a pair of rollers, and the pair of rollers includes a roller and a fixed roller. Wherein, the pressure roller can be a convex roller or a flat roller, and the fixed roller is a flat roller. Furthermore, the roller of the roller can be moved up and down, but the fixed roller is fixed. In other words, when the pressure roller step is performed, the semi-coagulated embryo is pressed by the roller. In an embodiment, the roller of the pressing roller may be a roller on the semi-coagulated embryo (that is, the roller of the pressing roller is the upper roller, and the fixed roller is the lower roller), so the roller of the roller is directed toward In the following way, the pressure roller semi-condenses the shell on the top of the embryo. In some embodiments, the roll of the roll is preferably disposed above the semi-coagulated embryo and presses the roll onto the roll in a downward direction so that the upper crust can be more tightly bonded to the lower crust. In some embodiments, the pressing distance of the pressing roller (according to the relative relationship between the pressing roller and the semi-coagulated embryo, the pressing distance refers to the pressing distance of the pressing roller) may be 4 mm to 20 mm. In some embodiments, the nip of the nip rolls may preferably range from 4 mm to 12 mm, and more preferably from 6 mm to 10 mm.

In the present invention, if the roller on the semi-coagulated embryo (ie, the upper roller) and the roller under the semi-coagulated embryo (ie, the lower roller) simultaneously press the semi-coagulated embryo, although the semi-coagulated embryo The upper crust and the lower crust are easily contacted and combined, but the solidification interface between the upper crust and the lower crust is liable to cause excessive strain and cause internal cracking. If the above-mentioned upper roller is a fixed roller and the lower roller is a squeeze roller, it is affected by gravity, and the casting machine needs to use a relatively large force to lift the pressing roller and make the upper casing and the lower casing The shell contacts the bond.

If the pressure roller is disposed on the semi-coagulated embryo, when the pressure roller step is performed, the pressed roller roller can be applied to the upper casing of the semi-coagulated embryo, and the upper crust and the lower coagulation The shell is solidified and combined, wherein the molten molten steel of the semi-coagulated embryo core is extruded in the opposite direction of the continuous casting direction, thereby eliminating the segregation and microvoiding of the prepared embryo. Accordingly, if the pressing distance of the pressing roller is less than 4 mm, the excessively small pressing distance cannot provide sufficient micropore healing effect, and the subsequent molded embryo core has micropore defects. If the pressing distance of the aforementioned roller is greater than 20 mm, the molten molten steel in the core of the semi-coagulated embryo can be completely extruded and heal the shrinkage cavity and the microvoid. When the extrusion distance is more than 20 mm, the thickness of the embryo is too thin, and at the same time, the load is increased, and the casting machine equipment is enlarged to increase the equipment cost.

Accordingly, when the center solidification rate of the semi-coagulated embryo is less than 0.8, since the thickness of the core which is not completely solidified is rapidly increased, the extrusion distance must be increased to allow the upper crust and the lower crust to be in contact with each other. At the same time, the excessive extrusion distance tends to cause excessive strain at the solidification interface, which may easily cause internal cracks or cause segregation to deteriorate. If the solidification rate of the semi-coagulated embryo is not less than 1.0, the molten steel in the core of the semi-coagulated embryo is nearly solidified, and the segregation can not be improved, so that the pressing roller must apply a larger pressing force. Heal the shrinkage and micropore defects. However, the greater the squeezing force requires a larger casting machine to be implemented, which significantly increases the equipment cost of the casting machine.

According to the foregoing description, the method for manufacturing the cast brist of the present invention is to press the shell of the semi-coagulated embryo by a press roll to extrude the molten steel of the semi-coaged embryo at a specific central solidification rate. Liquid, and solidified combined with the shell And the lower shell. Accordingly, the semi-coagulated embryo of the present invention does not need to be convexly controlled, so the continuous casting process of the present invention excludes the step of performing the convex step.

2A and FIG. 2B, wherein FIG. 2A is a perspective view showing a pressure roller device when a pressure roller step is performed according to an embodiment of the present invention, and FIG. 2B is a view along an embodiment of the present invention. Schematic diagram of the axial cutting of the roller of the pressure roller. In FIG. 2A, the direction 230a is the continuous casting direction of the casting blank 230. The press roll device 200 may include a press roll 210 and a fixed roll 220, wherein the roll roll 210 is a male roll and the fixed roll 220 is a flat roll. The roll roller 210 has a raised press roll surface 211, and the width W of the press roll surface 211 is greater than the distance D between the two three-pronged points 231 of the cast. The term "trigeminal point" as used herein refers to cutting the casting blank 230 in a vertical direction 230a. The two corners of one of the narrow sides of the casting blank 230 respectively depict a virtual line, and the intersection of the two virtual lines is a trigeminal Point 231. Similarly, on the other narrow side of the slab 230, another three-pronged point 231 can be obtained by the intersection of the imaginary lines depicted by the two corners. Wherein, the angles α ₁ and α ₂ (or α ₃ and α ₄ ) of the imaginary line and the narrow side of the casting 230 are both about 45 degrees. The formation of the trigeminal point 231 is the macroscopic tissue boundary generated by the outer surface to the inner surface of the narrow surface and the narrow surface molten steel in the solidification step described above, and it can be visualized by a suitable etching method.

In general, the position of the trigeminal point 231 of the casting blank 230 is the same as the position of the trigeminal point of the semi-coagulated embryo 233 due to the gradual cooling of the resulting giant grain boundary generated by the trigeminal point 231 alloy steel. When the semi-coagulated embryo 233 passes through the pressing roller 210, the pressing of the pressing roller 210 causes the molten molten steel of the core of the semi-condensed embryo 233 to be extruded in the opposite direction of the direction 230a, thereby making the upper shell It is combined with the lower crust and forms a casting 230. According to this, if the aforementioned pressure roller table The width W of the surface 211 is smaller than the distance D between the three-pronged points 231. Since the partially molten molten steel is not extruded, the area between the two three-pronged points 231 is excessively molten molten steel, which is liable to cause segregation and/or shrinkage. hole. In one embodiment, the difference between the width W and the spacing D is greater than 0 mm and less than or equal to 200 mm, preferably greater than 0 mm and less than or equal to 160 mm, and more preferably 20 mm. From PCT to 60 mm. In one embodiment, in order to provide uniform properties to the interior of the resulting preform 230, the aforementioned differences are preferably equally divided at the ends of the roll roller 210. In other words, along the axial direction of the roll roller 210, the distance between the one side of the roll roller 210 beyond the trigeminal point 231 is half of the aforementioned difference.

In a specific example, when the embryo width of the semi-coagulated embryo is 1880 mm, and the reduction of the roller of the press roll is 10 mm, the press roll of the flat roll for the semi-coagulated embryo core Both the roller and the pressing roller of the convex roller have similar pressing effects on the core of the casting. In other words, the pressing roller of the flat roller and the pressing roller of the convex roller can produce similar compression effects on the semi-coagulated embryo. However, the pressing force of the roller of the male roller is only 88% compared to the pressing force of the roller of the flat roller. Accordingly, when the pressure roller of the present invention uses the convex roller, the roller roller can more effectively press the roller to semi-coagulate the embryo, thereby reducing the energy cost of the pressure roller step. The reason for this is that the convex roller has a smaller pressing width than the flat roller, and the flat roller is pressed to a narrower edge having a lower temperature and higher strength, so that the load of the convex roller is lower than the load of the flat roller.

In an application, the pressure roller step of the present invention is carried out by a pair of rollers, and when the semi-coagulated embryo is completely solidified, the crucible of the semi-coagulated embryo is pressed by the roller of the pressure roller to force the half. The molten molten steel of the embossed core is extruded in the opposite direction of the continuous casting direction, and the segregation and shrinkage of the core of the casting embryo can be eliminated, and the suitable Used in castings of various specifications. Although the dynamic soft reduction system has multiple pairs of rollers with adjustable pitches, the pressure roller step of the present invention does not need to be combined with a dynamic light reduction system, so the device is relatively simple, and the complexity of the device can be greatly reduced and reduced. Maintenance costs of the press roll unit.

Furthermore, the semi-coagulated embryo and the cast embryo formed by the continuous casting process of the present invention are all casts in the shape of a plate, and the shell is pressed by a press roll to extrude the melting of the core of the semi-coagulated embryo. The molten steel is solidified and combined with the upper shell and the lower shell. Accordingly, the semi-coagulated embryo of the present invention does not need to form a convex belly structure, so the continuous casting process of the present invention eliminates the step of performing the convex belly, so that the continuous casting process can be applied to various types of casting embryos, and the device can be greatly reduced. Maintenance costs.

The following examples are used to illustrate the application of the present invention, and are not intended to limit the present invention, and various modifications and refinements can be made without departing from the spirit and scope of the invention.

Preparation of cast embryo Example

First, an alloy steel liquid is provided, and the alloy steel liquid is subjected to a solidification step of a continuous casting process to form a semi-condensed embryo. Then, when the semi-coagulated embryo is completely solidified (that is, the center solidification rate of the semi-condensed embryo is greater than or equal to 0.8 and less than 1.0), the semi-coagulated embryo is subjected to a press roll step, and the cast embryo of the embodiment can be obtained. . The prepared embryos were each tested in the following evaluation manner, and the results obtained are as described later.

Comparative example

First, the same alloy steel liquid as in the embodiment is provided, and the alloy steel liquid is subjected to a solidification step of a continuous casting process to form a semi-condensed embryo. The semi-coagulated embryos were lightly pressed to prepare a cast embryo of the comparative example. The prepared embryos were each tested in the following evaluation manner, and the results obtained are as described later.

Evaluation method and its results Radiation detection

The cast test pieces of the examples and the comparative examples were sampled in the regions between the trigeminal points of the cast test pieces prepared in the examples and the comparative examples, respectively. Wherein, in the width direction of the casting embryo, the size of the casting embryo test piece is 300 mm, and in the thickness direction of the casting embryo, the size of the casting embryo test piece is 100 mm, and the size of the casting embryo test piece in the direction of continuous casting of the casting embryo It is 20 mm to 40 mm.

Then, the cast test piece of the example was observed by a conventional radiation detecting method in which the radiation system irradiated the aforementioned cast embryo test piece in the continuous casting direction of the cast embryo. The results obtained are shown in Figures 3A and 3B, respectively. Fig. 3A is a view showing a radiation detecting image of a casting test piece according to an embodiment of the present invention, and Fig. 3B is a view showing a radiation detecting image of a casting test piece according to a comparative example of the present invention.

According to the radiographic image shown in FIG. 3A and FIG. 3B, the core portion of the cast embryo test piece of the embodiment of the present invention does not have a shrinkage cavity, but the core portion of the cast test piece of the comparative example has a significant shrinkage hole.

Eclipse detection

The cast embryos obtained in the examples and the comparative examples were sampled in the same manner as the sampling method and the sampling size of the above-described radiation detection to obtain the cast test pieces of the examples and the comparative examples, respectively.

Then, the cast test pieces of the examples and the comparative examples were etched by a conventional etch test method, and etched images of the examples and the comparative examples were obtained, and the results obtained are shown in Figs. 4A and 4B. Fig. 4A is a view showing an etched tissue image of a cast test piece according to an embodiment of the present invention, and Fig. 4B is a view showing an etched tissue image of a cast test piece according to a comparative example of the present invention.

According to the etched tissue image shown in FIG. 4A and FIG. 4B, the core portion of the cast embryo test piece of the example has no segregation, but the core portion of the cast test piece of the comparative example has significant segregation.

According to the foregoing description and the evaluation results, the method for producing the cast bristles of the present invention is a step of pressing a semi-coagulated embryo by a pair of rolls to obtain a cast bristles. Wherein, the present invention presses the semi-coagulated embryo under the weight of the roller to extrude the molten steel of the semi-coagulated embryo, thereby effectively eliminating the core of the casting (ie, the area between the trigeminal points) Segregation and shrinkage, and solidification combined with the shell and the lower shell, which can meet the specifications of ultra-thick steel and large-size steel rods.

Secondly, the manufacturing method of the invention does not need to perform the convex step, and does not need to use the dynamic soft reduction system to perform the convex belly control, but can meet the processing requirements of various specifications of the casting embryo, and greatly reduce the maintenance cost of the continuous casting device.

The present invention has been disclosed in the above embodiments, and is not intended to limit the present invention. Any one of ordinary skill in the art to which the present invention pertains can make various changes without departing from the spirit and scope of the invention. And the scope of the present invention is defined by the scope of the appended claims.

Claims (7)

A method for manufacturing a cast embryo, comprising: providing an alloy steel liquid; and performing a continuous casting process on the alloy steel liquid, wherein the continuous casting process comprises: performing a solidification step on the alloy steel liquid to form a half-condensed embryo And when a center solidification rate of the semi-coagulated embryo is greater than or equal to 0.8 and less than 1.0, the semi-coagulated embryo is subjected to a press roll step to obtain the cast embryo, wherein the press roll step utilizes a Carrying out the roller, and the pair of rollers is composed of a pressing roller and a fixed roller, and wherein the continuous casting process excludes a bulge step when the center solidification rate is less than 0.8 The continuous casting process excludes the step of performing the press roll, and the press roll step is excluded by using a dynamic soft reduction system. The method for producing a cast bristles according to claim 1, wherein one of the press rolls has an extrusion distance of 4 mm to 20 mm. The method for manufacturing a casting blank according to claim 1, wherein the pressing roller is an upper roller, and the fixed roller is a lower roller. The method for manufacturing a cast bristles according to claim 1, wherein the press roll is a convex roll or a flat roll, and the fixed roll is a flat roll. The method for manufacturing a casting blank according to claim 4, wherein one of the surfaces of one of the pressing rolls has a width greater than a pitch of one of the three points of the casting. The method for producing a cast broth according to claim 5, wherein the difference between the width and the pitch is greater than 0 mm and less than or equal to 200 mm. A splicing embryo, which is produced by the method of any one of claims 1 to 6, wherein a region between the trigeminal points of the casting embryo does not have a segregation and a crater.