JP3563587B2 - Hot width reduction press tool and manufacturing method thereof - Google Patents

Description

【００３３】
【発明の効果】
本発明工具は、スラブ押圧面に上記成分の合金鋼５が肉盛溶接されているので、耐摩耗性に優れ、かつ熱亀裂の発生や拡大が抑制される。このため、金型２の母材４には、上記機械構造用炭素鋼などの比較的安価な材料を採用しても、耐用期間を大幅に延長することができる。そのうえ、スラブ押圧面が摩耗や亀裂により劣化した金型には、再び合金鋼を肉盛溶接して再使用するので、従来金型のような研削による再使用と異なり、金型サイズ一定範囲で繰返し使用でき、廃棄処分がなくなる。
また本発明法により、上記のような優れた工具が安定して確実に製造できる。
したがって、本発明は熱間スラブのプレス作業率向上、工具の保有個数減、研削作業の廃止および使用期間延長による原単位向上で、コスト削減に大きく寄与する。
【図面の簡単な説明】
【図１】本発明金型の使用例を示す平面図である。
【図２】（ａ）および（ｂ）は本発明金型の例を示し、図１のＡ−Ａ矢視断面図である。
【図３】本発明法におけるブロック溶接の例を示す説明図である。
【符号の説明】
１…熱間スラブ
２…金型
３…カリバー
４…母材
５…合金鋼[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is a tool used when a hot slab such as a steel material is width-reduced by a press, specifically, a tool mainly for a press die, and a tool capable of greatly extending a service life. It relates to the manufacturing method.
[0002]
[Prior art]
In the production of steel materials, etc., it is possible to adjust the width of a slab heated for hot rolling or the like (hereinafter referred to as a hot slab) to a width suitable for the product size by reducing the width by pressing. Done. The die for the press includes ductile cast iron (FCD specified in JIS G5502), alloy steel for machine structure (SCM specified in JIS G4105), hot work steel (SKT specified in JIS G4404), and the like. Is manufactured as a unitary material.
[0003]
Regarding the shape of the mold, for example, in Japanese Patent Application Laid-Open No. 60-203305, a mold having an inclined portion with a limited inclined angle on the entering side in the slab traveling direction, and a mold having a parallel portion is continuously used on the surface and inside of the slab. It is disclosed that the width can be continuously reduced to an arbitrary width without generating defects such as cracks.
[0004]
In Japanese Patent Publication No. 4-33521, rolling is performed by providing an inclined caliber groove having a limited size on a slab pressing surface of a mold having an inclined portion at least on an entrance side in a slab advancing direction and subsequently having a parallel portion. It is disclosed that the occurrence of slab surface flaws at the time can be prevented.
[0005]
[Problems to be solved by the invention]
In a width reduction press of a hot slab, there is a problem in that a slab pressing surface of a mold is not only worn but also thermally cracked, and the degree of cracking increases as the number of uses increases. If the slab is reduced in width by a mold having a large thermal crack, defects such as edge cracks occur in the rolled material in the subsequent hot rolling, and the mold must be replaced.
[0006]
For example, when a hot slab of ordinary steel for continuous hot rolling is width-pressed using a mold manufactured as a unitary piece of the ductile cast iron, about 700 slabs are processed per day. In normal use, replacement was required in 9-10 days.
[0007]
At the time of replacement, the continuous pressing operation must be stopped, so that the operation rate including the preceding and following steps is reduced, and productivity is impaired. In addition, a mold with a crack that has been cracked is reused after grinding and removing the crack. However, the cost has increased due to the grinding cost and the increase in the number of spare molds for replacement.
[0008]
Furthermore, if the grinding amount of the mold increases, the change in the distance between the pair of left and right dies increases, which hinders the pressing work. Therefore, a shim plate for correcting the thickness of the mold is inserted to reduce the number of reuses. Although the extension has been attempted, it has been necessary to increase the load of the mold changing work and extend the time.
[0009]
The molds made of the above alloy steels for machine structural use or hot work tool steels have improved wear and thermal cracks as compared with those made of ductile cast iron, but no significant improvement was observed 4 to 5 times. After the grinding and re-use, they had to be disposed of.
Further, all of the techniques described in the above publications relate to the shape of a mold, and an effect of extending the service life of the mold cannot be expected.
[0010]
Accordingly, the present invention provides a tool such as a press die used for reducing the width of a hot slab such as a steel material, by suppressing the occurrence of thermal cracks on the slab pressing surface, extending the service life, and changing the tool. The purpose is to reduce the frequency.
[0011]
[Means for Solving the Problems]
The tool of the present invention for achieving the above object is a tool for reducing the width of a hot slab by pressing, and C: 0.05 to 0. 5%, Si: 0.2-0.9%, Mn: 0.15-1.2%, Cr: 3.0-8.0%, Mo: 1.5-3.5%, A hot width reduction press tool characterized in that an alloy steel consisting of Fe and inevitable impurities is weld-welded in the remainder.
And the said alloy steel further contains V: 0.1-0.5%, Ni: 1.5-3.0%, W: 0.1-0.5% by weight%. It is further preferable that the alloy steel is build-up welded to a thickness of 15 to 35 mm. Further, a method of the present invention for achieving the above object is to provide a tool for reducing the width of a hot slab by pressing, wherein the alloy steel in the tool of the present invention is build-up welded to a pressing surface against the hot slab, Hot width reduction characterized in that the entire material and the overlay welding portion are cooled at a temperature of 500 ° C. to 550 ° C. after holding for not less than t / 25 hours in accordance with the thickness t (mm) of the tool. This is a method for manufacturing a press tool.
Preferably, the overlay welding is performed by block welding, and then the overlay welding portion is subjected to a peening process.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
The tool of the present invention will be described with reference to an example of a mold shown in FIGS. FIG. 1 is a plan view showing a state in which the hot slab 1 is being moved in the direction of the arrow and a pair of dies 2 and 2 is performing width reduction pressing in the width direction. FIG. 2 is an enlarged cross-sectional view of the mold 2 of FIG. The slab pressing surface of the mold 2 may be flat as in (a), or the caliber 3 may be formed as in (b).
[0013]
As the base material 4 of the mold 2, similarly to the above-described conventional material, ductile cast iron (FCD specified in JIS G5502), alloy steel for machine structure (SCM specified in JIS G4105), and hot die steel (JIS G4404) In addition to the above, it is possible to use SKT specified in JIS G4051, and inexpensive carbon steel for machine structures (such as S35C and S45C specified in JIS G4051), and similar steel materials (such as SF590 specified in JIS G3201). Can also be adopted.
[0014]
The alloy steel 5 is overlay-welded to the slab pressing surface of the mold 2, and the components of the alloy steel 5 are, in terms of% by weight, C: 0.05-0.5% and Si: 0.2- 0.9%, Mn: 0.15 to 1.2%, Cr: 3.0 to 8.0%, Mo: 1.5 to 3.5%, with the balance being Fe and unavoidable impurities. . Overlay welding can be performed by MIG welding using, for example, a flux-cored wire having the above component composition.
[0015]
The reasons for limiting each component range will be described below.
C forms a solid solution in the weld metal steel to improve its hardness and strength, and also has an effect of forming carbides by being combined with Cr, Mo, V or W to improve wear resistance. If the content is less than 0.05%, the desired effect cannot be obtained, and if it exceeds 0.5%, the toughness decreases and the heat crack resistance decreases. Therefore, the C content is set to 0.05% or more and 0.5% or less.
[0016]
Si has the effect of improving the strength of the weld metal and improving the flowability of the molten weld metal to prevent the occurrence of defects. However, if the content is less than 0.2%, the desired effect cannot be obtained. If it exceeds 0.9%, the toughness decreases and the heat crack resistance decreases. Therefore, the Si content is set to 0.2% or more and 0.9% or less.
[0017]
Mn has the effect of deoxidizing the weld metal during welding and improving the toughness. However, if it is less than 0.15%, the desired effect cannot be obtained. Saturates. Therefore, the Mn content is set to 0.15% or more and 1.2% or less.
[0018]
Cr is added to provide oxidation resistance and combine with C to increase the high-temperature strength. If it is less than 3.0%, its effect is not exhibited, and if it exceeds 8.0%, toughness decreases and heat cracking occurs. Is reduced. Therefore, the Cr content is set to 0.3% or more and 8.0% or less.
[0019]
Mo is added in order to improve the hardness and strength by forming a solid solution in the weld metal steel and to combine with C to increase the high-temperature strength and to provide temper softening resistance. If it is less than 1.5%, the effect is not exhibited, and if it exceeds 3.5%, toughness is reduced and heat crack resistance and the like are reduced. Therefore, the Mo content is set to 1.5% or more and 3.5% or less.
[0020]
The slab pressing surface of the mold 2 made of the tool of the present invention is excellent in abrasion resistance, and the occurrence and expansion of thermal cracks are suppressed because such an alloy steel 5 is overlay-welded. For this reason, even if a relatively inexpensive material such as the above-mentioned carbon steel for machine structure is used as the base material 4 of the mold 2, the service life can be greatly extended. The alloy steel whose slab pressing surface has been deteriorated due to wear or cracks can be reused by overlay welding of the alloy steel.
[0021]
Further, in the tool of the present invention, the alloy steel 5 further contains V: 0.1 to 0.5%, Ni: 1.5 to 3.0%, and W: 0.1 to 0.5% by weight. It is preferable that it is contained.
V is added as necessary to further increase the high-temperature strength and temper softening resistance. If it is less than 0.1%, no further effect is exhibited, and if it exceeds 0.5%, toughness is reduced and heat crack resistance and the like are reduced. Therefore, the V content is set to 0.1% or more and 0.5% or less.
[0022]
Ni is added to further improve the toughness of the weld metal. If it is less than 1.5%, no further effect is exhibited, and if it exceeds 3.0%, the hardness is reduced and the wear resistance is reduced. Therefore, the Ni content is set to 1.5% or more and 3.0% or less.
W is added to further improve the high-temperature strength. If it is less than 0.1%, no further effect is exhibited, and if it exceeds 0.5%, toughness is reduced and heat crack resistance is reduced. Therefore, the W content is set to 0.1% or more and 0.5% or less.
Due to the effects of these additional elements, the generation and expansion of thermal cracks in the alloy steel 5 are further suppressed, and the service life of the mold 2 can be further extended.
[0023]
Further, in the tool of the present invention, it is preferable that the alloy steel 5 is overlay-welded in a thickness a range of 15 to 35 mm. When the thickness a is less than 15 mm, the effect of extending the service life is not sufficiently exhibited, and when the thickness a is up to about 35 mm, the efficiency of the overlay welding operation is high and it is suitable from the viewpoint of cost.
[0024]
Next, the method of the present invention will be described with reference to the mold 2. After the overlay welding of the alloy steel 5 of the tool of the present invention on the slab pressing surface of the mold 2, the entire base metal 4 and the alloy steel 5 of the overlay welding portion are combined at a temperature of 500 ° C. to 550 ° C. After the heat treatment, the holding time at the temperature in this range is set to t / 25 hours or more according to the thickness t (mm) of the mold. It is desirable to preheat the mold to 400 to 500 ° C. as a pre-process of overlay welding in order to reduce residual stress after welding.
[0025]
As described above, overlay welding can be performed by MIG welding using, for example, a flux-cored wire having the above-described composition. However, while removing residual stress in the welded portion, the structure is densified and ductility is improved. Heat treatment under the above conditions is performed for this purpose. If the heat treatment temperature is lower than 500 ° C., it is difficult to achieve these effects within a practical time. If the temperature exceeds 550 ° C., the hardness of the weld metal is reduced, the wear resistance is reduced, and the base material is softened to lower the strength. If the holding time in this temperature range is less than t / 25 hours, it is difficult to obtain a heat treatment effect over the entire slab pressing surface.
[0026]
Further, in the method of the present invention, it is preferable that the overlay welding is performed by block welding, and then the overlay welding portion is subjected to a peening treatment. Here, the block welding means that the surface to be overlaid is divided into blocks, each block is welded intermittently, and finally the entire surface is overlaid. For example, in the example of FIG. 3, 12 sections are welded in the order of (1), (2), (3),. After overlay welding, peening is performed on the weld to reduce residual stress and strengthen the deposited metal. By performing the heat treatment after the peening, the residual stress is removed, and the deposited metal is further strengthened.
[0027]
In the above-described tool of the present invention and the method of manufacturing the same, as the tool, in addition to the mold, a portion that comes into contact with a hot material of a side guide that corrects the front and rear movement during width reduction pressing, and a forging floor plate material of an up-down forging machine And other high temperature tools.
[0028]
【Example】
As an example of the present invention, two sets each of a mold 2 having a shape as shown in FIG. 1 and having a flat slab pressing surface as shown in FIG. 2 (a) and a mold having a caliber as shown in FIG. 2 (b). Each was manufactured from carbon steel S45C for machine structural use. The thickness t of each mold 2 is 400 mm. In both molds, alloy steel 5 composed of two types of components A and B shown in Table 1 was overlay-welded by MIG welding. The thickness a of each of the alloy steels 5 was 20 to 30 mm. As a comparative example, a mold of the same shape made of ductile cast iron was manufactured.
[0029]
Each of the four molds of the present invention was preheated to 400 to 500 ° C. in an electric furnace, and then subjected to block welding as shown in FIG. 3 using a flux-cored wire composed of each component shown in Table 1. After the welding of each block, a peening process was performed in a red-hot state, and overlay welding was performed on the entire surface of the slab pressing surface. Next, heat treatment was performed in an electric furnace at 500 to 550 ° C. for 16 hours, and after cooling to room temperature, it was finished to a predetermined size by mechanical grinding or the like.
[0030]
Using the molds of the four sets of the present invention and the two sets of the comparative example, a width reduction press of a hot slab for a thin steel plate was performed. The size of the slab was 5000 to 12000 mm in length, 240 mm in thickness, and the difference in width between before and after pressing was about 300 mm. About 700 hot slabs were pressed a day.
[0031]
Regarding the molds of the comparative examples, both flat molds and molds with calipers required replacement in 10 days due to expansion of thermal cracks. In contrast, the molds of the present invention were flat and caliber-attached, and in all cases, the alloy steels of Table 1 could be used for 60 to 80 days for component A, 80 to 100 days for component B, and can be used without rearrangement. Was.
[0032]
[Table 1]

[0033]
【The invention's effect】
Since the alloy steel 5 of the above-described component is overlay-welded to the slab pressing surface, the tool of the present invention has excellent wear resistance and suppresses the occurrence and expansion of thermal cracks. For this reason, even if a relatively inexpensive material such as the above-mentioned carbon steel for mechanical structure is used as the base material 4 of the mold 2, the service life can be greatly extended. In addition, in the mold where the slab pressing surface has deteriorated due to wear or cracks, the alloy steel is overlaid and reused again. Can be used repeatedly, eliminating waste.
Further, according to the method of the present invention, the above-mentioned excellent tool can be stably and reliably manufactured.
Therefore, the present invention greatly contributes to cost reduction by improving the pressing operation rate of the hot slab, reducing the number of tools held, eliminating the grinding operation and improving the basic unit by extending the use period.
[Brief description of the drawings]
FIG. 1 is a plan view showing an example of using a mold of the present invention.
FIGS. 2 (a) and (b) show an example of the mold of the present invention, and are sectional views taken along the line AA of FIG.
FIG. 3 is an explanatory view showing an example of block welding in the method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Hot slab 2 ... Mold 3 ... Caliber 4 ... Base material 5 ... Alloy steel

Claims (5)

A tool for reducing the width of a hot slab by pressing, the weight of the pressing surface against the hot slab being
C: 0.05-0.5%,
Si: 0.2-0.9%,
Mn: 0.15 to 1.2%,
Cr: 3.0 to 8.0%,
Mo: 1.5 to 3.5%
And a balance width welded alloy steel comprising Fe and inevitable impurities. The alloy steel further comprises, by weight:
V: 0.1 to 0.5%,
Ni: 1.5 to 3.0%,
W: 0.1 to 0.5%
The hot width reduction press tool according to claim 1, further comprising: The hot-width reduction press tool according to claim 1 or 2, wherein the alloy steel is overlay-welded to a thickness of 15 to 35 mm. In a tool for reducing the width of a hot slab by pressing, the alloy steel according to claim 1, 2 or 3 is overlay-welded to a pressing surface against the hot slab, and the entire base metal and overlay weld are formed. A method for manufacturing a hot width rolling press tool, comprising: holding at a temperature of 500 ° C. to 550 ° C. for at least t / 25 hours according to the thickness t (mm) of the tool and then cooling. The method for producing a hot width reduction press tool according to claim 4, wherein the overlay welding is performed by block welding, and then the overlay welding portion is subjected to a peening process.

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