KR101066571B1 - Press anvil apparatus for forging the width of hot slab - Google Patents

Abstract

In the mold apparatus for forging the width of the slab by installing the width press mold on both sides of the hot slab, the present invention reduces the temperature deviation in the width press mold and creates a compressive stress condition on the surface of the mold. It relates to a mold apparatus configured to suppress the propagation of.

Width slab forging press die apparatus of hot slab according to the present invention proposed to achieve the above object is provided on both sides of the hot slab produced by the continuous casting is provided with a width press mold to be advanced back and forth in the width direction of the hot slab A plurality of cooling water passages are formed inside the width press die, and fixed ends protruding on both sides are formed at rear ends of the width press mold to form concave spaces in the center, and the width press mold is a holder surrounding the outside of the mold. It is inserted and fixed in the inside, and a liner for holding the fixed end is inserted between the rear end and the holder of the width press die, the holder is connected to the drive unit for advancing the holder back and forth in the width direction of the hot slab.

Hot Slab, Width Press Mold, Crack Propagation Suppression

Description

Press anvil apparatus for forging the width of hot slab}

1 is a perspective view of a conventional width forging press die apparatus.

Figure 2 is a perspective view of the width forging press mold apparatus according to the present invention.

Figure 3 is a plan sectional view of the width forging press die apparatus according to the present invention.

Figure 4 is a graph showing the crack generation of the press die.

Figure 5 is a state of use of the width forging press mold apparatus according to the present invention.

Fig. 6a shows a measurement position of a width forging press die in accordance with the present invention.

FIG. 6B is a graph showing the temperature change according to the measurement position shown in FIG. 6A.

6C and 6D are graphs showing the change in stress according to the measurement position shown in Fig. 6A.

[Description of Reference Numerals]

1: width press mold 2: center parallel plane

3: entry slope 4: exit slope

5: drive part 10: width press mold

11: center parallel plane 13: entrance slope

15: exit slope 17: coolant passage                 

19: fixed end 21: space part

23: liner 25: holder

27: drive unit 29: cooling pipe

30: hot slab

The present invention relates to a forging press die apparatus for width slabs of hot slabs, and more particularly, in a mold apparatus for forging a slab width by installing width press molds on both sides of a hot slab, At the same time, the present invention relates to a mold apparatus configured to suppress the propagation of cracks due to thermal deformation by creating a compressive stress condition on the surface of the mold.

In the case of manufacturing a slab having a different width in the conventional continuous casting, a variable width mold or a method of exchanging the mold was used. In recent years, instead of fixing the width of the casting slab during continuous casting, forging the hot slab in the width direction by using the width forging press die device in the rough rolling step of the hot rolling process, the width of the slab is changed to the continuous casting process and continuous casting The hot rolling process of the slab is synchronized to improve productivity.

As the width forging method of hot slab, there are a vertical rolling method for performing a width forging using a vertical rolling mill and a width forging press method for performing a width forging using a press die. Among them, the width forging press method is a method of repeatedly contacting (forging) and opening the hot slab by using a pair of width press dies, while moving the hot slab in the longitudinal direction while the press die is in contact with each other. It is a technique for forging to a predetermined width.

Fig. 1 shows a conventional width forging press die apparatus used in the above-described width forging press method. The width forging press die apparatus is comprised by the width press die 1 largely contacted with a hot slab, and the drive part 5 which advances this width press die 1 back and forth in the width direction of a hot slab. The front face of the width press die 1 is formed at its center with a central parallel surface 2 in parallel contact with the hot slab and at both sides with inclined surfaces 3 and 4 inclined contact with the hot slab. The entrance inclined surface 3 must be formed to be inclined because it substantially reduces its width in contact with the hot slab, whereas the exit inclined surface 4 does not necessarily have to be inclined to a surface which is not in contact with the hot slab.

When the width forging press method is performed using the above-mentioned width forging press die apparatus, the temperature is raised to about 500 to 900 ° C while the width press mold 1 is in contact with the hot slab heated to 1100 to 1300 ° C. In particular, when the mold is in contact with the slab, a very large temperature deviation occurs between the surface and the inside of the mold. If the surface temperature of the mold is higher than the inside, the surface is exposed to high tensile stress conditions by thermal stress. In this state, when the surface of the width press die 1 is cooled with cooling water, the temperature of the surface portion is drastically lowered than inside, and the tensile stress of the surface portion is drastically reduced. As a result, the surface portion of the width press die 1 is exposed to thermal fatigue conditions while repeatedly undergoing a series of processes in which the tensile stress is rapidly changed to generate fatigue cracks. The crack generated in this way is further grown by the tensile stress as described above and eventually destroyed when the critical value is reached.

In order to solve the problem of shortening the life of the mold due to the temperature difference between the surface portion and the inside of the mold as described above, the mold is forcibly cooled by the coolant when the mold is opened from the slab during the width forging press operation. However, even in the open phase, the gap between the slab and the mold is small, so if too much coolant is used, the corner of the side of the hot slab is overcooled, resulting in quality defects. On the contrary, when the amount of cooling water is reduced to prevent the quality defect, there is a problem that the life of the mold is shortened while the thermal stress is increased by the temperature rise.

In order to solve the problems caused by the temperature deviation between the mold and the slab as described above, a method of heating the mold itself by installing an induction heating device inside the mold, inserting an insulating material between the divided surfaces using the mold as a split structure, A method of providing a passage for allowing a high temperature fluid to pass between the divided surfaces has been proposed.

However, the method of induction heating the mold has a problem in that the structure of the mold is not only complicated, but the cost is increased while the induction heating apparatus is installed in the mold used as a consumable. In this case, the ceramic thermal spray coating or the insulating fiber is broken at high temperatures and high loads, and the performance cannot be exerted. When the high temperature fluid is used, the mold structure is complicated and the cost is increased while maintaining a special high temperature fluid.

The present invention has been proposed to solve the above problems, and it cools the inside of the width press mold to reduce the temperature deviation between the surface portion and the inside caused by repeated contact and opening with the hot slab and at the same time the surface portion of the mold It is an object of the present invention to provide a press mold apparatus configured to apply a compressive stress to a surface portion by using the deformation stress resulting from the difference in thermal expansion between the rear ends.

Width slab forging press die apparatus of hot slab according to the present invention proposed to achieve the above object is provided on both sides of the hot slab produced by the continuous casting is provided with a width press mold to be advanced back and forth in the width direction of the hot slab A plurality of cooling water passages are formed inside the width press die, and fixed ends protruding on both sides are formed at rear ends of the width press mold to form concave spaces in the center, and the width press mold is a holder surrounding the outside of the mold. It is inserted and fixed in the inside, and a liner for holding the fixed end is inserted between the rear end and the holder of the width press die, the holder is connected to the drive unit for advancing the holder back and forth in the width direction of the hot slab.

In addition, the front surface of the width press die is formed with a central parallel surface in parallel with the hot slab in the front center, the side of the front side is formed with an inclined side surface inclined contact with the hot slab.

Hereinafter, the configuration of the width forging press die apparatus according to the present invention with reference to the accompanying drawings will be described in more detail. Figure 2 is a perspective view of the width forging press die apparatus according to the present invention, Figure 3 is a cross-sectional view taken along the line AA 'of FIG.

The present invention is largely installed on both sides of the hot slab produced by continuous casting is fixed to the width press mold 10 and the width press mold 10 forging the width of the slab while advancing forward and backward in the width direction of the hot slab. The holder 25 which supports, and the drive part 27 which advances the said width press die 10 back and forth in the width direction of a slab by moving this holder 25 are comprised.

The width press mold 10 is forging the slab to a predetermined width while repeatedly contacting and opening with the hot slab, the front surface in contact with the hot slab is formed as follows. First, the central parallel surface 11 is formed in the center of the front surface in parallel contact with the hot slab, the side inclined surface 12 inclined contact with the hot slab is formed on one side, the exit inclined surface 13 is formed on the other side This exit slope 13 is not in direct contact with the hot slab (see Fig. 6A).

The inclined inclined surface 12 serves to directly reduce the width of the slab to the surface that is in contact with the hot slab first, and the central parallel surface 11 is made to be in contact with the side of the slab in which the unevenness is formed during the pressing process to make it even. Play a role. Since the central parallel surface 11 is in frequent contact with the slab, if it is formed to be too long, the side parallel inclined surface 13 is formed to adjust the length of the central parallel surface 11 so that the slab can be unevenly cooled according to the prolonged contact. . Therefore, in order to press the slab width, the inclined surface must be formed on the entrance side of the mold, but the inclined surface is not necessarily formed on the exit side.                     

A plurality of cooling water passages 17 are formed to penetrate up and down inside the width press mold 10, which is connected to the cooling pipe 29 and the width press mold 10 is formed from the hot slab. When opened, the coolant flows into the coolant passage 17 to cool the mold. If the coolant is introduced when the width press mold 10 is in contact with the hot slab, the coolant is cooled to the side surface of the hot slab in contact with the mold, causing uneven cooling of the slab. Therefore, the mold is cooled when the width press mold 10 is opened. It is preferable to make it. The coolant passage 17 reduces the thermal deformation by reducing the temperature deviation of the mold due to contact and opening.

The width press mold 10 is fixed to the rear end is inserted downward in the holder 25 surrounding it. A stepped portion is formed at the tip of the holder 25 to prevent the width press die 10 from moving forward. The rear end of the width press die 10 is provided with fixed ends 19 at both sides thereof, and a concave space 21 is formed at the center thereof. A liner 23 holding the fixed end 19 is inserted between the rear end of the width press mold 10 and the holder 10. The liner 23 together with the space 21 serves to restrain the thermal deformation of the width press mold 10 according to the thermal stress to suppress the propagation of cracks formed on the surface of the mold. Details thereof will be described later.

The operation of the width forging press die apparatus according to the present invention configured as described above will be described in more detail with reference to FIGS.

As shown in FIG. 4, propagation of fatigue cracks generated on the surface of the mold during the width press process depends on the crack initiation time and the crack growth time. The mold life is determined below the threshold because the mold breaks when the depth of cracks generated reaches a threshold. According to the mold apparatus of the present invention, the crack initiation time can be delayed by rapidly cooling the mold through the coolant passage 17, and the crack growth time is a stress condition caused by constraining the thermal deformation of the mold to the liner 2. Can be delayed by

The crack initiation time is determined by the thermal stress load applied repeatedly. The severity of the thermal stress load is determined by the temperature deviation of the mold and the period of change. Therefore, in order to delay the time that cracks are generated due to thermal stress, the temperature deviation for each position of the mold must be basically reduced. In the present invention, the mold is rapidly cooled by the cooling water passage 17 formed in the mold. Minimize the temperature deviation.

On the other hand, crack growth time is governed not only by thermal stress load but also by stress condition of crack tip. When tensile stress is applied to crack tip, crack growth is accelerated and crack growth is suppressed when compressive stress is applied. Therefore, in order to delay the crack growth time, the cracked mold surface must be exposed to as low tensile stress or compressive stress as possible. As shown in Fig. 5, when the width press mold 10 is in contact with the hot slab 30, the thermal expansion of the surface portion is larger than the rear portion because the temperature of the mold surface portion is higher than the temperature of the rear portion. If the mold is not restrained due to the difference in thermal expansion, thermal deformation occurs in the form indicated by the dotted line in FIG. 5. However, when the liner 23 restraining the fixed end 19 formed on the rear side of the mold is installed as in the present invention, since the thermal deformation such as a dotted line cannot be performed, the restraint stress is generated and the tensile stress is generated on the rear side of the mold. In this case, compressive stress is generated in the surface portion, especially in the central parallel surface 11. Moreover, the space portion 21 formed at the center of the rear side of the mold reduces the tensile stress that resists the restraint stress, so that the compressive stress that suppresses the growth of the cracks acts more effectively on the central parallel surface 11 where the cracks frequently occur.

Figure 6 shows the change in temperature and stress according to the measurement position when using the width forging press die apparatus according to the present invention. 6A shows a state in which the width press mold 10 is in contact with the hot slab 30, the temperature and the stress of the width press mold 10 are measured from the surface portion to the rear portion of the mold along the X-axis direction, respectively. In particular, e denotes a position where the coolant passage 17 is installed in the inside of the mold, f denotes a position where the space portion 21 starts, and g denotes a rear end position of the mold where the space portion 21 ends.

FIG. 6B is a graph showing the temperature distribution inside the mold when using the conventional width press mold 1 shown in FIG. 1 and when using the width press mold 10 according to the present invention. When the mold is in contact with the hot slab, the temperature of the surface portion rises and the temperature decreases toward the rear portion, while when the mold is opened, the temperature rises toward the rear portion because the surface portion is cooled by the coolant. Therefore, the temperature distribution curves at the time of contact and opening have the same temperature at a predetermined position, but the same point becomes near f according to the conventional mold, while according to the mold of the present invention, the temperature is lower because it is cooled by the cooling water. In addition, the temperature equality becomes e 'closer than the cooling water passage position e. In this graph, it can be seen that the conventional mold has thermal deformation due to the temperature deviation from the surface portion to the point f, while the mold of the present invention exhibits thermal deformation only due to the temperature deviation from the surface portion to the point e '. Moreover, because of exposure to small temperature deviations, the magnitude of thermal strain is also reduced. As a result, since the mold according to the present invention is rapidly cooled by the coolant passage 17, the probability of cracking due to thermal deformation is also lowered.

FIG. 6C is a graph showing the change of thermal stress occurring therein when the mold follows the temperature distribution of FIG. 6B. As shown in the drawing, in the case of a conventional mold, since a temperature deviation occurs up to a point f, a tensile stress occurs from the surface portion to a point f as a thermal stress caused by the temperature deviation. On the other hand, in the case of the mold according to the present invention, the tensile stress occurs only up to the point e 'at the surface portion. Therefore, since the width | variety which tensile stress generate | occur | produces inside a metal mold | die is narrow, it becomes difficult to grow a crack by that much.

Furthermore, in the case where the space portion 21 is formed in the center of the rear side of the mold as shown in the present invention, as shown in FIG. 6D, the compressive stress is applied to the surface portion of the mold, in particular, the center parallel plane 11, by the restraining stress by the liner 23. This will work. The tensile stress is generated between the points e and f by the restraint stress generated in response to the thermal strain stress by the action of the space 21 and the liner 23. This stress condition makes cracks on the mold surface more difficult to grow.

According to the press die apparatus for forging the width of the hot slab according to the present invention configured as described above, the tensile stress applied to the surface of the mold is small or rather the compressive stress is generated to bring about the effect of further reducing the growth rate of cracks and depth of cracking The time to reach the threshold is delayed, consequently extending the life of the mold.

Claims (2)

A width press mold 10 is provided on both sides of the hot slab 30 produced by continuous casting, and is rolled back and forth in the width direction of the hot slab 30. A plurality of width press molds 10 are provided in the width press mold 10. A cooling water passage 17 is formed, and at the rear end of the width press mold 10, fixed ends 19 protruding from both sides are provided to form concave spaces 21 in the center, and the width press mold 10 is formed. Inserted and fixed in the holder 25 surrounding the outside of the mold, a liner 23 for holding the fixing end 19 is inserted between the rear end of the width press mold 10 and the holder 25, the holder ( 25 is a hot forging press die apparatus for hot slab, characterized in that the holder 25 is connected to the drive unit 27 for advancing forward and backward in the width direction of the hot slab (30). According to claim 1, wherein the front side of the width press mold 10 is formed in the center of the front surface parallel to the center parallel plane 11 in parallel with the hot slab 30, the one side of the front surface with the hot slab 30 and Width slab forging press die apparatus of the hot slab, characterized in that the side inclined surface 13 is inclined contact.

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