JPH07108369A - Manufacture of composite material - Google Patents

Abstract

PURPOSE:To provide a composite material with wear resistance, resistance to rough surface, and toughness by combining a material with wear resistance, having a fine and uniform metallic structure and a strong material, including a composite roll to be applied for purposes of rolling of a steel. CONSTITUTION:Molten metal with a chemical composition of 0.8 to 4.3wt.% C, is poured around a core material, and a >=50mm build-up layer with carbide, is allowed to form between the core material and a fixed casting mold while the core material and the molten metal are allowed to intermittently descend downward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various composite materials including composite rolls applied for steel rolling, and a combination of a hard facing material having fine and uniform wear resistance such as a liner and a tough core material. The present invention relates to a manufacturing method of.

[0002]

2. Description of the Related Art A typical example of the composite material is a composite roll. Conventionally, as a method of manufacturing a composite roll,
Centrifugal casting method (Refer to Chapter 24 of "Foundry Handbook" edited by Japan Foundry Association)
Has been generally used, but in recent years, as a new method for producing this type of roll, for example, Japanese Patent Laid-Open No. 3-28570.
The build-up method disclosed in Japanese Patent No. 3 was adopted.

[0003]

The most important properties required for a rolling roll are wear resistance, surface roughening resistance and toughness. Among them, a composite roll composed of an outer layer having abrasion resistance and a core material having toughness is widely used for the purpose of having both abrasion resistance and toughness which are contradictory to each other. As a method of manufacturing this composite roll, the centrifugal casting method has been generally adopted as described above. Further, recently, the build-up method disclosed in Japanese Patent Laid-Open No. 3-285703 has been adopted, which is capable of improving the above-mentioned both characteristics. According to this method, a gap between a core material and a cooling die that coaxially surrounds the core material is filled with a molten metal for forming an outer layer, and this is welded and solidified to produce a composite material. According to this method, it is possible to select a stronger steel-based material for the core material,
As for the outer layer material, it is not necessary to consider the effect on the inner layer material, and since the wear resistant material can be selected independently, it is possible to improve both wear resistance and toughness.

However, in this method, the solidification of the outer layer progresses in the axial direction, so that the non-uniformity of the structure in the axial direction is likely to occur, and particularly in the case of a rolling roll having a thick buildup layer and a small solidification rate, continuous solidification occurs. The organization grows and becomes coarse,
When it is used as a rolling roll, it causes rough skin and there is a problem that the roll quality cannot be stabilized.

Therefore, according to the present invention, when a composite material such as a composite roll is manufactured by a build-up method, an outer layer material having a fine and uniform metal structure and excellent in wear resistance is stably manufactured, It is intended to provide quality composite materials.

[0006]

In order to solve the above-mentioned problems, the composite material of the present invention comprises a core material made of a tough material, which is placed inside a stationary mold, and is surrounded by a weight ratio of chemical components. C: In a method for producing a composite material in which a molten metal composed of 0.8 to 4.3% is injected and the core material and the molten metal are welded and integrated, a build-up layer of 50 mm or more is formed around the core material. After injecting the molten metal, the core material is intermittently lowered downward.

[0007]

[Function] As described above, the reason for limiting the composite material in which the molten metal is injected around the tough core material to form the buildup layer with the fixed mold is to have both abrasion resistance and toughness. Is. That is, when manufacturing a composite material composed of an outer layer having wear resistance and a core material having toughness, according to this method, the core material can be selected as a tougher steel-based material. With regard to the material, it is possible to improve both wear resistance and toughness because the wear resistant material can be selected independently.

The reason for limiting the C content of the hardfacing material to 0.8 to 4.3% is as follows. If C is less than the lower limit value of 0.8%, C is solid-dissolved in the matrix structure and hard carbide does not crystallize or precipitate, so that it does not have a function as a wear resistant material. Further, as described above, since C solid-dissolves in the matrix structure, the carbide crystallized at the crystal grain boundaries disappears and the cast structure does not remain as the final product, and the aim is to make the cast structure fine and uniform. The purpose is different from the invention. On the other hand, if C exceeds 4.3%, which is the upper limit value, coarse Fe ₃ C carbide crystallizes as a primary crystal during solidification, and the amount of carbide increases, making it extremely fragile and ensuring toughness even by compounding. Can not. That is, in the present invention, it is indispensable that austenite has the effect in the case of performing dendrite solidification as the primary crystal, and that the final product also has the carbide.

Now, as shown in FIG. 4, it is essential to form the build-up layer 1 while intermittently lowering the molten metal 1 ′ injected around the core material 2 between the fixed mold 3 and the molten metal 1 ′. The most important thing of the invention. That is, when the core material and the molten metal are continuously lowered to form the build-up layer as shown in the conventional example, as shown in FIG. 3, in the material for performing the dendrite solidification, the dendrite 6 is upward in the axial direction. And grows into a coarse organization. In addition, it is generally considered that a uniform structure can be obtained because the casting conditions are constant, but when casting is performed in the axial direction as in this method and the overlay thickness increases, the overlay material is solidified and the core is solidified. It is necessary to cast for a long time in order to completely weld it to the material, and it is substantially difficult to maintain uniform solidification conditions. An excessive load of other alloys results in a non-uniform structure. Therefore, as in the present invention, by intermittently descending, that is, by repeating descending / stopping, the growth of dendrites is limited and new coagulation nuclei are generated, so that a large number of dendrites 6 are generated as shown in FIG. Has been miniaturized.

Although there are some cases where intermittent casting is carried out in continuous casting of cast iron by a fixed mold, it is limited to those which crystallize or precipitate graphite, and those having brittle carbides have been put to practical use. Absent. Further, in the thin buildup layer, the solidification rate is fast and basically the solidification structure is fine and the segregation of the alloy into the residual molten metal is small in terms of chemical composition, so that the effect of the present invention is practically recognized as a range. As compared with the continuous casting shown in FIG. 1, the intermittent casting is limited to a build-up thickness of 50 mm or more in which the crystal grain size is clearly smaller.

[0011]

EXAMPLES As an example of the present invention, a product body diameter of 800 mm,
A work roll for a hot strip finishing mill having a built-up thickness of 100 mm and a unit weight of 11 tons was manufactured. Casting was basically performed by the continuous casting method disclosed in Japanese Patent Laid-Open No. 3-285703, and forged steel was used as the core material to form a composite roll. As the heat treatment, after casting, the usual heat treatment such as annealing, quenching and tempering, which is considered as the material to be used, was performed. The drawing conditions in the method of the present invention, the dimensions of the product, the material of the overlay material and the core material,
Although appropriately set from the temperature of the molten metal, the build-up thickness, etc., at a drawing speed of 10 mm / min to 30 mm / min which is usually performed at a build-up thickness of 50 mm or more in the method of the present invention,
The withdrawal interval is preferably 30 seconds to 2 minutes. If the time is 30 seconds or less, solidification is not stable and a uniform structure cannot be obtained, and if the time is 2 minutes or more, the effect of making the structure fine is small.

Table 1 shows specific chemical components and casting conditions, and Table 2 shows manufacturing quality and results of actual use in comparison with conventional examples. As is clear from Table 2, according to the intermittent drawing method of the present invention, the crystal grain size is remarkably reduced with the same chemical composition as the conventional method, and as a result, the surface roughness of the roll actually subjected to rolling is small. , I was able to suppress the rough skin significantly.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

As described above, according to the present invention, it is possible to produce an outer layer material having carbides and having excellent wear resistance with a fine and uniform metal structure, and by combining it with a tough core material, a rolling roll is used. It has become possible to supply high-performance rolls that have the most important required properties, such as wear resistance, surface roughening resistance, and toughness. As a result, it is possible to manufacture a high-quality rolled product, which has industrial value, and the effect is extremely large.

Although this embodiment is applied to a rolling roll, the present invention is not limited to this, and it is highly required to have a combination of abrasion resistance, surface roughening resistance and toughness. Even if it is applied to a composite material such as a liner, the same action and effect can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing the crystal grain size of rolls manufactured according to the present invention and a conventional example in relation to a casting speed.

FIG. 2 is a schematic diagram showing a solidification form of the present invention.

FIG. 3 is a schematic view showing a conventional solidification form.

FIG. 4 is a diagram showing an outline of manufacturing equipment for a composite roll according to the present invention.

[Explanation of symbols]

 1 Build-up material 1'Melted material of build-up material 2 Core material 3 Fixed mold 4 Fireproof frame 5 Core material preheating heat induction coil 5'Melting metal heating induction coil 6 Dendrite structure 7 Eutectic structure

Claims (1)

[Claims] 1. A C: 0.8 by weight chemical composition is provided around a core material made of a tough material, which is disposed inside a stationary mold.
In a method for producing a composite material, in which a molten metal composed of ˜4.3% is poured and the core material and the molten metal are welded and integrated, after pouring a molten metal that forms a built-up layer of 50 mm or more around the core material, A method for producing a composite material, characterized in that the core material is intermittently lowered downward.