JP3305541B2 - Manufacturing method of composite roll of cemented carbide and cast iron - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a roll used for rolling steel wires, bars and the like.

[0002]

2. Description of the Related Art As a roll used for rolling a wire, a bar, or the like, a composite roll in which a carbide ring formed of a cemented carbide in an annular shape is fitted to a roll body is known. . The composite roll includes a mechanically assembled carbide ring on a roll body and a molded-in carbide ring. In the former case, the number of parts is increased, the assembling is troublesome, and the cost is increased. In the latter case, the cost can be reduced as much as the necessity of assembling is eliminated, but there is a problem that the roll is liable to crack due to the production method. The latter roll is manufactured by first forming a cemented carbide ring on the inner peripheral surface of a mold (1) composed of a sand mold as shown in FIG.
The outer periphery of (2) is embedded (step 1). A molten metal, which is a cast-in metal (30), is poured into a mold (1) (step 2). The molten metal is naturally cooled and solidified in the mold (1), and the solidified part is roll body
(3) (Step 3). The as-cast product taken out of the mold (1) is heat-treated (step 4). The as-cast product is machined into a desired shape and dimensions to expose the outer peripheral portion of the carbide ring (Step 5). Carbide ring that is buried in the mold (1) and does not directly contact the melt when the molten metal is poured into the mold (1) in step 2.
A temperature gradient may occur between the outer peripheral side of (2) and the inner peripheral side of the carbide ring (2) that is in direct contact with the molten metal, and the carbide ring (2) and the roll body (3) may be broken. Because the difference in thermal expansion between the carbide ring (2) and the cast metal is large, that is, the carbide ring
As compared to (2), the cast-in metal (30) is more likely to be thermally shrunk, and in the cooling step (step 3), due to the heat shrinkage of the cast-in metal holding both sides of the carbide ring (2), As a whole, a force acts in the direction of compressing the carbide ring (2), but a tensile stress is partially generated, and cracks are likely to occur. Further, even if cracks are not generated in the cooling stage, cracks may occur when a post-process is performed while the residual stress is high.
As a material for the cast-in metal (30), if high-Ni cast iron or the like close to the difference in thermal expansion of the cemented carbide ring (2) is used, the occurrence of roll cracking can be suppressed. high. Also, in step 4, when performing the heat treatment, since the carbide ring (2) is exposed to the outer periphery of the as-cast product, an antioxidant is applied to the surface of the carbide ring (2). It is necessary to prevent oxidation of the ring.

[0003] An object of the present invention is to clarify a method of manufacturing a roll made of a cast iron and a cemented carbide material which prevents cracking of the roll and oxidation of a cemented carbide ring in a production stage.

[0004]

According to a method of manufacturing a composite roll of the present invention, a cemented carbide ring (2) is molded by a fixing jig (4).
(1) It is arranged apart from the inner peripheral surface, the molten metal is poured into the mold (1), the whole carbide ring (2) is casted with molten metal and solidified, and the solidified part is made into the roll body (3). The cast-in metal covering the outer peripheral portion of the hard ring (2) is removed by machining to expose the outer peripheral portion of the carbide ring (2).

[0005]

[Operation and Effect] The cemented carbide ring (2) is arranged at a distance from the inner peripheral surface of the mold (1) by the fixing jig (4), and the molten metal is poured into the mold (1). 2) is cast in a state where the whole is completely buried in the cast-in metal.

[0006] When the molten metal is cooled naturally and solidified, the whole of the super hard ring (2) is completely buried in the as-cast metal (30). As in the conventional case, the solidified shrinkage of the molten metal causes the carbide ring
The partial difference in the pressure acting on (2) is small, and the cooling rate between the part of the cemented carbide ring (2) buried in the mold (1) and the part in contact with the molten metal as in the past is different. It is possible to eliminate a large difference and prevent a residual stress from being caused in the carbide ring (2) due to these.

[0007] The as-cast product is machined into a desired shape and dimensions by machining, and the outer periphery of the carbide ring (2) is rolled into a roll body.
The roll is made to appear from (3). As mentioned above,
The residual stress of the carbide ring (2) is low, and it is possible to prevent the roll from cracking due to the residual stress during machining.

The following heat treatment step can be added to the as-cast product taken out of the mold (1). The heat treatment is a heat treatment in which part of the cast-in metal (30) undergoes pearlite transformation, and the remainder undergoes bainite transformation. Residual stress is generated in the stuffed metal (30) by the pearlite transformation, and the cemented carbide ring (2) and the stuffed metal (30) are transformed by the bainite transformation accompanied by expansion.
To alleviate the residual stress due to the difference in thermal expansion between them. When all of the as-cast metal (30) is transformed into pearlite, the carbide ring
If the residual stress generated in (2) is too high, and if only bainite transformation is used, the cast-in metal (30) may become brittle and the carbide ring (2) may become tensile residual stress. Therefore, it is not preferable for use in rolling. Conventionally, carbide ring
Since (2) was exposed from the roll, it was necessary to apply an antioxidant when performing the heat treatment. However, in the present invention, the carbide ring (2) was made of cast-in metal (30). It is not necessary because it is surrounded by

After heat treatment is applied to the as-cast product, the as-cast product is processed into a desired shape and dimensions by machining, and the outer peripheral portion of the carbide ring (2) is made to come out of the roll body (3). A roll is produced.

[0010] Even if a special component such as high Ni cast iron is not used as the cast-in metal (30), cracks and the like do not occur in the roll in the roll manufacturing process. Relatively inexpensive materials such as ductile cast iron can be used, and the cost can be kept low.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below.
This will be described in detail with reference to the drawings. The method for producing a roll comprising a cemented carbide material and cast iron according to the present invention comprises the steps of: disposing a cemented carbide ring (2) in a mold (1) (step 1); A step of pouring the molten metal at a temperature higher than the temperature at which the surface is melted (step 2), and a step of naturally cooling and solidifying the molten metal (step 3). A step of heat-treating the as-cast product taken out of the mold (1) (step 4), a step of machining the heat-treated as-cast product into a desired shape and dimensions
(Step 5). The feature of the method of the present invention is that
(2) is arranged at a distance from the mold (1), and in the casting stage, the entire cemented carbide ring (2) is surrounded by the as-cast metal (30), and the thermal stress and heat shrinkage force from the as-cast metal (30) Is a carbide ring (2)
This is to prevent the generation of cracks or residual stress which may cause the cracks in the conventional carbide ring (2) by being applied substantially uniformly to the entire surface of the ring. Therefore, carbide ring
The difference in thermal expansion between (2) and the cast-in metal (30) can be neglected, and the range of material selection increases. In addition, there is no need to apply an antioxidant to the carbide ring (2) by heat treatment after casting.

First, the mold (1), the carbide ring (2), the fixing jig (4) and the molten metal will be described. FIG. 1 is a sectional view of the mold (1). The mold (1) is a sand mold formed around an iron frame (not shown), and has an inner surface configured such that the upper and lower parts are reduced in diameter and the lower part is closed. The inner diameter of the enlarged diameter portion of the mold (1) is φ450 mm. The carbide ring (2)
It is made of a cemented carbide and has the following components and is fixed to a fixing jig (4) as shown in FIG. 2 so that the enlarged diameter portion of the mold (1) does not come into contact with the inner peripheral surface of the mold (1). Deployed apart.

[Carbide ring] Ingredient: WC 75% by weight + binder metal 25% by weight Binder metal composition: Co 12% by weight, Ni 12% by weight, C
r 1% by weight Dimensions: outer diameter φ400mm, inner diameter φ290mm, width 80mm (thickness 55mm)

As shown in FIG. 2, the fixing jig (4) for fixing the carbide ring (2) to the mold (1) includes an annular portion (41) surrounding the outer peripheral surface of the carbide ring (2). It comprises a plurality of support portions (42) projecting from the annular portion (41) and having ends fixed to the inner peripheral surface of the mold (1). Carbide ring (2) is a fixing jig
It is fitted to the annular portion (41) of (4) and fixed inside the mold (1).

The molten metal is solidified to form the roll body (3), and is a ductile cast iron having the following components. [Molten] Ingredients (unit: wt%) CSiMnPSNiMgFe 3.27 2.05 0.29 0.006 0.010 2.38 0.05 balance

[Manufacturing Method] [Step 1 (Fixing and Preheating of Carbide Ring)] Carbide Ring (2)
Is fixed to the inside of the mold (1) by a fixing jig (4) away from the inner surface of the mold (1), and the cemented carbide ring (2) is fixed at approximately 100 ° C. to approximately 700 ° C.
Preheat at ° C. At this time, the preheating of the carbide ring (2) is
If the temperature is lower than 0 ° C., welding with the molten metal becomes difficult, and the carbide ring (2) may be broken by a thermal shock at the time of casting the molten metal. When preheating to approximately 500 ° C. or higher, the surface of the carbide ring (2) is oxidized, so that it is necessary to perform a surface treatment such as Ni plating.

[Step 2 (Pouring of molten metal)] Carbide ring
After preheating (2), the molten metal heated above the temperature at which the surface of the superhard ring (2) melts is poured, and the entire superhard ring (2) is immersed in the molten metal. By adjusting the temperature of the molten metal as described above, the surface of the carbide ring (2) in contact with the molten metal is melted and welded to the molten metal. Therefore, as-cast metal (3
0) and the carbide ring (2) need not be fixed by other fixing means. In the present invention, since the entire carbide ring (2) is immersed in the molten metal, the entire peripheral surface of the carbide ring (2) is substantially uniformly heated by the molten metal, and a temperature gradient is generated in the carbide ring (2). Absent. Therefore, the carbide ring due to the temperature gradient (2)
Cracks can be prevented. The carbide ring used in this embodiment
In (2), the surface melts at 1350 ° C. or higher. Therefore, casting was performed by heating the temperature of the molten metal to 1540 ° C., which is the temperature at which the surface of the carbide ring (2) melts.

[Step 3 (Cooling)] After the molten metal is poured into the mold (1), the molten metal solidifies, is allowed to cool to room temperature, is slowly cooled, and is taken out of the mold (1). The molten metal expands by causing only pearlite transformation by slow cooling, and applies thermal stress and thermal compressive force to the carbide ring (2). Since these act substantially uniformly on the entire surface of the carbide ring (2), it is possible to suppress the occurrence of local residual stress in the carbide ring (2).
However, an unstable stress state is generated in the entire roll due to the pearlite transformation, and if machining is performed in this state, the roll may be broken. Even if the roll is not broken by machining, it is considered that the product is broken by rolling the product using the roll. Therefore, step 4 described later
The roll body is heat-treated to transform the roll body (3) from an unstable state of only pearlite transformation to a partial pearlite transformation and a remainder bainite transformation.

[Step 4 (heat treatment)] In the above step, the mold (1)
Is subjected to a heat treatment. Conventionally, since the carbide ring (2) came out of the outer periphery of the as-cast product,
Before performing the heat treatment, it was necessary to apply an antioxidant to the exposed surface of the carbide ring (2). However, in the present invention, since the carbide ring (2) is completely surrounded by the cast-in metal (30), it is not necessary to apply an antioxidant. In the heat treatment, an appropriate compressive residual stress is generated in the carbide ring (2) by appropriate quenching and tempering heat treatment in accordance with the components of the cast-in metal (30). Here, the appropriate quenching and tempering heat treatment means that part of the cast-in metal (30) undergoes pearlite transformation and the remainder
(About 300 ° C. to about 450 ° C.). By combining these transformations, the residual stress due to the difference in thermal expansion between the carbide ring (2) and the cast metal (30) is reduced. In the case of the pearlite transformation alone, the residual stress generated in the carbide ring (2) becomes too high. In the case of the bainite transformation only, the cast-in metal (30) becomes brittle and the carbide ring (2) becomes too tensile. It causes residual stress, which is not preferable for rolling use.

In this embodiment, the quenching temperature was 890 ° C., the air was cooled, and the tempering temperature was 540 ° C. The difference in thermal expansion between the cemented carbide ring (2) and the as-cast metal (30) during the quenching and tempering heat treatment is as shown in FIG. 3, and the as-cast metal (30) has a pearlite transformation (see FIG. 3). By causing section A) and bainite transformation (section B in FIG. 3), cast-in metal (30) and carbide ring (2)
And the thermal expansion difference between them can be reduced. Also, carbide ring
Since (2) is surrounded by the cast-in metal (30), it undergoes isotropic expansion and / or compressive force, so that during the quenching and tempering heat treatment, the cemented carbide ring (2) and the cast-in metal ( Three
0) does not crack.

[Step 5 (machining)] The heat-treated product prepared in the above step is machined to form a carbide ring.
The surface of (2) is exposed, and the as-cast metal (30) and the carbide ring (2) are processed into a desired roll shape and size to produce a roll. The mechanical processing may include a step of cutting a desired groove according to the processing shape, diameter, and the like of the material to be rolled on the outer peripheral surface of the carbide ring (2).

The description of the above embodiments is for the purpose of illustrating the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope thereof. Further, the configuration of each part of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made within the technical scope described in the claims.

For example, as the cemented carbide ring (2), a cemented carbide containing WC as a main component is used. However, the composition and shape are not limited to those in the above embodiment, and cermet, ceramics, or the like may be used. Similarly, as the cast-in metal (30), bainite and high chromium cast iron which undergo pearlite transformation during heat treatment can be used.

[Brief description of the drawings]

FIG. 1 is a sectional view of a mold of the present invention.

FIG. 2 is a perspective view of a carbide ring and a fixing jig.

FIG. 3 is a graph showing a difference in thermal expansion between a carbide ring and a cast-in metal.

FIG. 4 is a sectional view of a conventional mold.

[Explanation of symbols]

 (1) Mold (2) Carbide ring (3) Cast-in metal (4) Fixing jig

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C21D 9/38 C21D 9/38 A (72) Inventor Yutaka Nakai 64 Nishimukaijima-cho, Amagasaki City, Hyogo Prefecture Inside Kubota Amagasaki Plant (56 References JP-A-4-319059 (JP, A) JP-A-61-199567 (JP, A) JP-A-4-344808 (JP, A) JP-A-59-24564 (JP, A) 58-138551 (JP, A) JP-A-47-14019 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 19/16 B21B 27/00 B21B 27/02

Claims (2)

(57) [Claims] 1. A cemented carbide ring (2) made of a cemented carbide, cermet, ceramics or other such cemented carbide material is formed into a mold (1).
In a method of manufacturing a composite roll of a cemented carbide and a cast iron in which a molten metal is poured into the mold (1) and solidified to form a solidified portion with the roll body (3), the cemented carbide ring (2) The jig (4) is set apart from the inner peripheral surface of the casting mold (1), and the molten metal is poured into the casting mold (1). A composite of cast iron and a cemented carbide material that has a main body (3), removes the cast-in metal covering the outer peripheral portion of the carbide ring (2) by machining, and exposes the outer periphery of the carbide ring (2). Roll manufacturing method. 2. The roll body (3) is partially transformed into pearlite, heat-treated to transform the remainder into bainite, and then machined to expose the outer peripheral surface of the carbide ring (2). The method for producing a composite roll of a cemented carbide material and cast iron according to claim 1.