JP2006142331A - Roll production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roll production method by which a core material is preheated so that the whole of the core material has been heated to an almost uniform temperature, and consequently a roll having more excellent quality than before can be produced, and further, the time for producing the roll can be made shorter than before. <P>SOLUTION: The roll production method is provided by which a core material 11 is concentrically, vertically inserted into a combined mold 10 where a cooling mold 19 is arranged beneath a refractory heating mold 18 provided with an electromagnetic induction heating coil 25, and while heating the circumference of the core material 11 to the vicinity of a solidus temperature Ts by a heating coil 26, molten metal 12 is poured into an annular gap part 22 around the core material 11, then, the core material 11 is lowered, and, while welding the molten metal 12 to the outer circumference thereof, a tinkered build-up welded layer 13 is formed, wherein before the core material 11 is heated by the heating coil 26, the core material 11 is preheated in such a manner that the temperature difference between the central part and the surface layer part in the core material 11 is 100°C or lower, and further, the temperature of the surface layer part in the core material 11 falls within the range of 300°C to the solidus temperature Ts or lower. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

For example, it is related with the manufacturing method of the roll which can be used for the roll for rolling in a steel-making rolling facility, and the roll for correction.

Conventionally, in a steelmaking rolling facility, rolling and straightening rolls are used, and rolling and straightening of steel sheets are performed.
As a manufacturing method of this roll, using a combination mold in which a cooling mold is integrally arranged at the bottom of a refractory heating mold provided with an electromagnetic induction heating coil, a steel core material is inserted inside the combination mold, While heating the periphery of the core material with a heating coil, injecting a separately prepared molten metal into the annular gap around the core material, the core material is lowered and the cast overlay layer ( In the following, a method for forming a simply built-up layer) is disclosed. The manufacturing method of this roll is CPC (Continuous Puring process for
It is also called the “Cladding: continuous injection cladding” method (see, for example, Patent Document 1).
As a result, a built-up layer can be formed in a single layer on the outer periphery of the core material, so that the concentration of heat on the core material can be made extremely small, such as a material that has not been possible with the conventional welding overlay method, such as a hypereutectic material. It is possible to form an overlay layer.

JP-A-10-258337

However, the conventional roll manufacturing method still has the following problems to be solved.
Since the core material is heated using the heating coil just before the molten metal is welded, only the surface layer portion of the core material is heated to the target temperature, and the inside of the core material is not sufficiently heated. For this reason, the temperature difference between the center portion and the surface layer portion of the core material becomes large, and a rapid temperature drop occurs in the surface layer portion after the heating by the heating coil is completed.
Here, when the liquidus temperature of the metal to be melted is lower than the solidus temperature of the core material, the molten metal easily adheres to the outer periphery of the core material even if the temperature of the surface layer portion of the core material decreases. It is possible to produce rolls with substantially stable quality.
However, when the liquidus temperature of the metal to be melted is equal to or higher than the solidus temperature of the core material, the heat transfer from the molten metal to the core material becomes more significant than in the above case. At this time, since the temperature of the core material increases as the welding of the molten metal proceeds, the movement of heat to the core material decreases as the temperature of the core material increases, so the melt melts into the core material surface layer. The amount became non-uniform in each part in the longitudinal direction of the core material, and the roll quality was not stable. This phenomenon tended to become more prominent as the descending speed of the core material was made slower than the current state and the time for welding the molten metal to the core material was lengthened.

Also, for example, when the temperature of the molten metal injected from one direction becomes non-uniform in the circumferential direction of the core material, the amount of melt melt into the core material surface layer is non-uniform in each part of the core material in the circumferential direction. Therefore, the components of the built-up layer to be formed vary, and the roll quality is not stable.
In particular, when a metal having a high liquidus temperature as described above is used, the roll quality is not stable because of poor welding of the molten metal to the core material, and the molten metal is accompanied by a decrease in temperature at the time of pouring the molten metal. There is also a problem that the rolls are easily solidified and the roll manufacturing operation cannot be stably performed.
Furthermore, in this roll manufacturing method, since the core material is heated after the core material is arranged in the combination mold, it is difficult to shorten the manufacturing time per roll, and the combination mold is used during the heating of the core material. The production efficiency was poor because it could not be used.

The present invention has been made in view of such circumstances, and by preheating the core material and heating the entire core material to a substantially uniform temperature, it is possible to manufacture a roll of superior quality than before, and It aims at providing the manufacturing method of the roll which can shorten manufacturing time conventionally.

In the roll manufacturing method according to the present invention that meets the above-mentioned object, the core material is concentrically perpendicular to the inside of the combination mold in which the cooling mold is integrally disposed in the lower part of the refractory heating mold provided with the electromagnetic induction heating coil A. Inserting and heating the periphery of the core to the vicinity of the solidus temperature Ts with the heating coil B, the molten metal is injected into the annular gap around the core to lower the core, and the core In the manufacturing method of the roll which solidifies while welding the molten metal on the outer periphery to form a cast overlay layer,
Before heating the core material with the heating coil B, the temperature difference between the center portion and the surface layer portion of the core material is within 100 ° C., and the temperature of the surface layer portion of the core material is not less than 300 ° C. The core material is preheated so as to be equal to or lower than the temperature Ts.

In the method for producing a roll of the present invention, before the core material is heated by the heating coil, the temperature difference between the center portion and the surface layer portion of the core material is within 100 ° C., the temperature of the surface layer portion of the core material is 300 ° C. Since it preheats so that it may become below phase line temperature Ts, it can heat not only the surface layer part of a core material but a center part. Therefore, the temperature drop of the surface layer portion of the core material can be greatly reduced as compared with the conventional case, so that the amount of heat transferred to the core material during pouring of the molten metal can be reduced, and the temperature near the surface layer of the core material during the welding of the molten metal can be reduced. The rate of temperature increase can be made faster than before, and the molten metal can be stably welded to the core material without variation, and a roll having a quality superior to that of the prior art can be produced.
Moreover, since the molten metal can be stably welded to the core material without variation, the lowering speed of the core material can be made faster than before and the productivity of the roll can be improved. Furthermore, since the temperature drop of the molten metal at the time of pouring the molten metal can be reduced, solidification of the molten metal at the time of pouring can be suppressed, and the roll manufacturing operation can be performed with good workability.

Here, when the preheating of the core material is performed in a preheating furnace provided separately from the combination mold or using the induction heating coil C provided separately from the heating coil B, the combination mold is applied to the core material. Can be used only for welding molten metal. Therefore, the operation rate of the combination mold can be increased from the current level, and the roll can be manufactured efficiently.

Further, when a metal having a liquidus temperature equal to or higher than the solidus temperature Ts of the core material is selected as the metal to be melted, it has conventionally been difficult to weld it to the core material using the CPC method. The metal can be stably welded to the outer periphery of the core material. Therefore, the types of rolls that can be produced by the CPC method can be greatly expanded as compared with the conventional one.

Furthermore, when pre-heating the core material after forming an antioxidant film having a melting point higher than the pre-heating temperature of the core material and lower than the solidus temperature Ts of the core material on the outer periphery of the core material, It is possible to prevent peeling of the antioxidant film at the time, and to form a cast overlay layer while suppressing oxidation of the surface layer portion of the core material.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is explanatory drawing of the manufacturing method of the roll based on one embodiment of this invention.

As shown in FIG. 1, the roll manufacturing method according to an embodiment of the present invention includes a core material (also referred to as a base material) inside a combination mold 10 having an electromagnetic induction heating coil (electromagnetic induction heating coil A) 25. 11, and the surroundings of the core material 11 are heated to the vicinity of the solidus temperature Ts by the heating coil (heating coil B) 26, and the molten metal 12 is welded and solidified on the outer periphery of the core material 11 to cast the overlaying layer ( Hereinafter, in the roll manufacturing method for forming 13 (also simply referred to as a build-up layer) (that is, by the CPC method), the core material 11 is preheated before the core material 11 is heated by the heating coil 26. This will be described in detail below.

The core material 11 used for manufacturing the roll is, for example, a solid having a diameter of 50 mm or more and 650 mm or less and a length of about 8000 mm at the longest, and having solid shaft portions 14 and 15 provided on both sides of the core material 11. Is. In addition, as a core material, the solid thing by which the axial part was provided only in the one side of the core material, and the hollow thing made into the cylindrical shape can also be used. Examples of the material of the core material 11 include chrome-molybdenum steel (SCM material), general structural rolled steel (SS material), 0.35% carbon steel (S35C), and 0.45% carbon steel (S45C). is there.

Before the core material 11 is preheated, first, an antioxidant film 16 having a melting point higher than the preheat temperature of the core material 11 and lower than the solidus temperature Ts of the core material 11 is formed on the outer periphery of the core material 11.
As the antioxidant film 16 formed on the outer periphery of the core material 11, for example, a nickel-based self-fluxing alloy (for example, a liquidus temperature of 1100 ° C. or less and a solidus temperature of 950 ° C. or less) or a cobalt-based self-fluxing alloy ( For example, a liquidus temperature of 1150 ° C. or lower and a solidus temperature of 1050 ° C. or lower can be used.
When the core material 11 is preheated in an inert atmosphere (for example, argon gas and nitrogen gas), the core material 11 is preheated without forming an antioxidant film on the outer periphery of the core material 11. Also good.

Thus, the core material 11 on which the antioxidant film 16 is formed is inserted into a preheating furnace (not shown) provided separately from the combination mold 10, and the size, shape, and material of the core material 11 are adjusted. Accordingly, it is allowed to stand for 5 hours to 10 hours, for example, and preheating is performed until the temperature of the core material 11 reaches 300 ° C. or more and the solidus temperature Ts (for example, 1400 ° C. or less).
Here, the preheating of the core material 11 is a temperature at which a rapid temperature drop in the surface layer portion of the core material 11 can be suppressed, that is, the temperature difference between the central portion and the surface layer portion of the core material 11 is within 100 ° C., preferably 70 ° C. However, it is preferable that the heating is performed until the entire core material 11 has a substantially uniform temperature.
In addition, the core material 11 is installed above the combination mold 10 without using a preheating furnace, for example, using the induction heating coil C (not shown) provided separately from the combination mold 10, the above-described conditions The core material 11 can also be preheated so that

When the preheating of the core material is less than 300 ° C., even if the entire core material can be preheated substantially uniformly, the preheating temperature of the core material itself becomes too low and the molten metal cannot be satisfactorily welded to the core material. . On the other hand, when the solidus temperature Ts is exceeded, a solid-liquid coexisting phase is generated. For example, the core material itself begins to partially melt, the crystal structure of the core material changes, or the shape of the core material collapses. There is a risk that a roll of stable quality cannot be produced.
Therefore, in order to produce a roll of stable quality, the lower limit of preheating is set to 300 ° C., preferably 400 ° C., more preferably 500 ° C. (800 ° C. as the best condition).
A roll is manufactured by forming the cast overlaying layer 13 on the outer periphery of the core material 11 thus preheated as described below, for example, using the method disclosed in Patent Document 1 described above.

As a roll manufacturing apparatus, as shown in FIG. 1, a fireproof heating mold 18 having a hollow annular fireproof frame 17 in which an electromagnetic induction heating coil 25 is disposed, and a lower part of the fireproof heating mold 18, A combination mold 10 in which a cooling mold 19 having an inner hole coaxial with this is integrally arranged is used. In addition, the lower part of the combination mold 10 is provided with an elevating device 20 that can be moved up and down by an elevating means (not shown) such as a hydraulic cylinder and that gradually lowers the core material 11 disposed on the upper part.

When manufacturing a roll using this, the core material 11 is inserted concentrically perpendicularly into the inner center of the combination mold 10 using the centering device 21. And the molten metal 12 which becomes the cast overlay layer 13 separately prepared in the melting furnace is injected into the annular gap portion 22 between the core material 11 and the combination mold 10 while flowing current through the electromagnetic induction heating coil 25, and the core material 11 is lowered intermittently.
In addition, since the antioxidant film | membrane 16 comprised with an alloy is formed in the outer periphery of the core material 11, after this antioxidant film fuse | melts, the molten metal 12 is welded to the surface layer part of the core material 11. FIG. Here, 23 in FIG. 1 indicates a melting portion, and 24 indicates a melting flux.

As the metal to be melted (hereinafter also referred to as molten metal), it is preferable to select and use a metal whose liquidus temperature is higher than the solidus temperature Ts of the core material. Of course, it is possible to use a conventionally used metal whose temperature is lower than the solidus temperature Ts of the core material.
Here, as the molten metal having a liquidus temperature equal to or higher than the solidus temperature Ts of the core material, for example, an Fe—Cr alloy or Ni—Cr alloy having a liquidus temperature of 1400 ° C. to 1500 ° C. is there. Note that the difference between the liquidus temperature and the solidus temperature of these molten metals is, for example, 150 ° C. or more and 300 ° C. or less.
In addition, as the molten metal having a liquidus temperature lower than the solidus temperature Ts of the core material, for example, an Fe—Cr alloy having a liquidus temperature of 1250 ° C. or higher and 1350 ° C. or lower, high-speed steel (for example, High-speed steel-based multi-alloy white cast iron) and Ni-Cr-based alloys. The difference between the liquidus temperature and the solidus temperature of these metals is about 50 ° C. or more and 140 ° C. or less, which is smaller than the above-described metals.

By heating the periphery of the core material 11 to the vicinity of the solidus temperature Ts (for example, about 1400 ° C. ± 50 ° C.) by the heating coil 26 arranged on the combination mold 10, by further contacting the molten metal 12, Part or all of the antioxidant film 16 is in a softened state, and further in a molten state. As a result, the molten metal 12 is sequentially cooled and solidified by the cooling die 19 while the molten metal 12 is welded to the surface of the core material 11 as it is or through the antioxidant film 16 to form the cast overlay layer 13.
The core material 11 on which the cast overlay layer 13 is formed is roughly processed to a state close to the finished state using a processing apparatus, and further subjected to a tempering process, that is, a predetermined quenching and tempering heat treatment. The intermediate product roll thus tempered is machined into a product shape that can be used for a rolling roll or a straightening roll to produce a roll to be a product.

Next, examples carried out for confirming the effects of the present invention will be described. Here, FIG. 2 is a graph showing the relationship between the average penetration amount of the molten metal into the core material and the cladding speed, and FIG. 3 is a graph showing the relationship between the output required for heating the core material and the cladding speed. 2 and 3, in the embodiment, a cast overlay layer is formed on the core material preheated for 8 hours in a preheating furnace set at a temperature of 500 ° C. (□ in FIG. 2, × and ■ in FIG. 3). In the comparative example, a cast overlay layer is formed without preheating the core material (cold material) at room temperature (X in FIG. 2, ▲ and ● in FIG. 3).

As shown in FIG. 2, in both the example and the comparative example, the average amount of penetration into the core material decreases as the cladding speed increases.
Here, the average penetration amount (mm) means that the roll manufactured using the CPC method described above is cut in a plane perpendicular to the axis of the roll, and the penetration at each position in the circumferential direction of each cut portion. The amount (depth of penetration) is obtained and averaged. Note that this work is performed by cutting the roll from 4 to 5 in the longitudinal direction and measuring the cross-sectional field of view, so the difference between the maximum value and the minimum value in FIG. Show.
Further, the clad speed was examined within a speed range of 4 × 10 ⁴ (mm ³ / sec) to 1 × 10 ⁵ (mm ³ / sec) where the conventional clad is performed.

As is apparent from FIG. 2, the difference between the maximum value and the minimum value of the average penetration amount at each cladding speed is the same as that of the comparative example except that the cladding speed is 9.1 × 10 ⁴ (mm ³ / sec). Is smaller than The difference between the maximum value and the minimum value of the average penetration amount at the cladding speed of 9.1 × 10 ⁴ (mm ³ / sec) is that the example is larger than the comparative example because the increase in the cladding speed As a result, the amount of penetration becomes smaller.
From this, it was confirmed that by forming a cast overlay layer on the outer periphery of the preheated core material, it was possible to improve the variation in the amount of melt melted into the cold material.

In addition, when comparing the average value of the average penetration amount at each cladding speed, the roll manufactured using the preheated core material has a larger numerical value than the roll manufactured using the core material without preheating. It was also confirmed that the efficiency of welding the molten metal to the core material was increased by preheating the core material.
From the above, after heating the core material to a red-hot state in the preheating furnace, the output of the heating coil and the refractory heating type electromagnetic induction heating coil is brought to a state close to full power, and the lowering speed of the core material is made faster than before. Even if the roll was manufactured, it was confirmed that a roll of good quality could be manufactured.

Next, the result of examining the weldability of the molten metal to the core material will be described. It should be noted that whether or not the welding is performed satisfactorily is determined by a penetrant flaw detection test (in which a penetrant is infiltrated into a wound opened on the surface of the specimen, and then the wound is observed as an instruction pattern of an enlarged image) (Destructive testing method). In FIG. 3, the heating output is the total output of the heating coil and the refractory heating type electromagnetic induction heating coil.
As shown in FIG. 3, the heating output in the CPC method can be significantly reduced by using a preheated core material, which is economical compared to using a core material that has not been preheated. Further, by using the preheated core material, the cladding speed can be increased as compared with the core material not preheated.
From the above, roll productivity can be improved more economically than before by preheating the core material.

Here, the result of examining the composition of the metal to be melted will be described.
As a molten metal, a conventionally used molten metal whose liquidus temperature is lower than the solidus temperature Ts of the core material, that is, an Fe—Cr alloy having liquidus temperatures of 1333 ° C. and 1350 ° C., 1310 ° C. High speed steel and 1273 ° C Ni-Cr alloy were used. The difference between the liquidus temperature and the solidus temperature of these molten metals is as follows: the Fe-Cr alloy with a liquidus temperature of 1333 ° C is 98 ° C, and the Fe-Cr system with a liquidus temperature of 1350 ° C. It is 140 ° C for the alloy, 60 ° C for the high-speed steel, and 73 ° C for the Ni-Cr alloy.
When these molten metals were used, rolls with more stable quality could be produced by preheating the core material than when using a core material that was not preheated.

Further, as a molten metal, a metal whose liquidus temperature is equal to or higher than the solidus temperature Ts of the core, that is, an Fe—Cr alloy having a liquidus temperature of 1440 ° C., and the liquidus temperature of 1273 ° C. described above. A Ni—Cr alloy having a liquidus temperature of 1420 ° C. improved from the Ni—Cr alloy was used.
Note that the difference between the liquidus temperature and the solidus temperature of these molten metals is 240 ° C. for the Fe—Cr alloy and 220 ° C. for the Ni—Cr alloy.

This Fe—Cr alloy having a liquidus temperature of 1440 ° C. is an alloy that cannot achieve satisfactory welding (cladding) unless the core is preheated. Here, in order to obtain satisfactory welding, a method of increasing the amount of carbon in the alloy and adjusting the melting point can be considered, but in this alloy, since the carbon component affects sigma brittleness, this effect is eliminated. It is desirable to reduce the amount of carbon as much as possible. That is, an alloy with an increased amount of carbon cannot exhibit its original performance and is not necessary. Therefore, an Fe—Cr alloy having a liquidus temperature of 1440 ° C. with a reduced amount of carbon is a core material. In the conventional CPC method in which no preheating is performed, the alloy component cannot be welded to the core material.

The Ni—Cr alloy having a liquidus temperature of 1420 ° C. is an alloy obtained by improving the Ni—Cr alloy having a liquidus temperature of 1273 ° C. The Ni—Cr alloy having a liquidus temperature of 1273 ° C. contains 0.9% by mass of a carbon component in order to obtain sound welding to the core material, but is a coarse compound of CB—Cr. In this case, the wear resistance is obtained, but the impact resistance is poor, and cracking may occur to peeling. Therefore, in order to improve impact resistance, the carbon component of the Ni—Cr alloy having a liquidus temperature of 1273 ° C. was lowered (0.1% by mass).
When these metals were used for welding to the core material, the molten metal could not be deposited with a core material that was not preheated, but by preheating the core material, stable quality rolls could be produced.
From the above, it becomes possible to weld the high melting point alloy to the core material by preheating the core material, so that the carbon component of the molten metal can be designed low as in the embodiment, for example, the problem of peeling can be solved. It was confirmed that stable quality rolls could be manufactured.

As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, a case where the roll manufacturing method of the present invention is configured by combining a part or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention.
Moreover, in the said embodiment, although the specific material was demonstrated about the core material and the molten metal, this invention is not limited to these materials, The range of the matter described in the claim It also includes other materials that can be considered within.

It is explanatory drawing of the manufacturing method of the roll which concerns on one embodiment of this invention. It is a graph which shows the relationship between the average penetration amount of the molten metal with respect to a core material, and a clad speed. It is a graph which shows the relationship between the output required for the heating of a core material, and a clad speed.

Explanation of symbols

10: combination mold, 11: core material, 12: molten metal, 13: cast overlay, 14, 15: shank, 16: antioxidant film, 17: fireproof frame, 18: fireproof heating mold, 19: cooling mold 20: lifting device, 21: centering device, 22: annular gap, 23: melting part, 24: melting flux, 25: electromagnetic induction heating coil, 26: heating coil

Claims (4)

A core material is inserted concentrically and vertically into a combination mold in which a cooling mold is integrally disposed at the bottom of a refractory heating mold provided with an electromagnetic induction heating coil A, and the periphery of the core material is fixed by a heating coil B. While heating to the vicinity of the phase wire temperature Ts, molten metal is poured into an annular gap around the core material to lower the core material, and the molten metal is solidified while being welded to the outer periphery of the core material. In the manufacturing method of the roll forming the layer,
Before heating the core material with the heating coil B, the temperature difference between the center portion and the surface layer portion of the core material is within 100 ° C., and the temperature of the surface layer portion of the core material is not less than 300 ° C. A method for producing a roll, characterized in that the core material is preheated so as to have a temperature Ts or lower. 2. The roll manufacturing method according to claim 1, wherein the core material is preheated in a preheating furnace provided separately from the combination mold or using an induction heating coil C provided separately from the heating coil B. 3. A method for producing a roll, characterized in that In the manufacturing method of the roll of any one of Claim 1 and 2, The metal used as the said molten metal selects that whose liquidus temperature is more than the solidus temperature Ts of the said core material, It is characterized by the above-mentioned. Roll manufacturing method. In the manufacturing method of the roll of any one of Claims 1-3, the preheating of the said core material is higher than the preheating temperature of this core material on the outer periphery of this core material, The solidus temperature Ts of this core material A method for producing a roll, which is performed after forming an antioxidant film having a lower melting point.

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