JPH01150460A - Casting method for composite roll - Google Patents

Abstract

PURPOSE:To obtain a roll excellent in wear resistance and rough surface resistance by rotating a mold and core metal by holding freely rotatably the core metal whose eccentric amt. is freely adjustable for the rotary center of a mold and casting the outer shell layer of a roll with varying the eccentric amt. by pouring a molten metal into the mold. CONSTITUTION:The cylindrical mold 1 casting an outer shell layer is rotated by a roller 4, a core metal 2 is arranged inside the mold 1 and rotated by the core metal rotating devices 5, 5a freely changing the eccentric amt. of the rotary shaft of the core metal 2 to the rotary shaft of the mold 1. A molten metal 3 is poured into the gap between the core metal 2 and mold 1 via a pouring pipe. In order to prevent the molten metal of immediately after pouring being spilled out of the mold 1, the direction and speed are allowed to coincide with in the rotation of the mold 1 and core metal 2 and the rotation is executed with zero eccentric amt. The rotary shaft of the core metal 2 is made eccentric according to the molten metal 3 being solidified from the contact face of the mold 1 and core metal 2. A molten metal stream and ununiform pressure distribution are generated at the molten metal inner part and a fine equiaxed crystal is thus formed with the dendrite under solidification being broken. Both hardness and toughness can be equipped with because the structure is refined.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention is directed to manufacturing composite rolls in which the core material and the outer shell layer material have different chemical compositions. The present invention relates to a method for casting a roll in which the materials are completely metallurgically joined and the outer shell layer material is toughened.

BACKGROUND ART In a work roll used for hot rolling of thin steel sheets, the rolling layer is required to have wear resistance and surface roughening resistance.

From the viewpoint of wear resistance, materials with a large amount of carbide, such as nihard cast iron and high chromium cast iron, are used for the outer shell layer of the roll.

Conventionally, wear resistance was emphasized in selecting the material for rolls, but as the quality of rolled plates has become higher, roughening resistance has come to be emphasized.

Abrasion resistance not only improves roll unit consumption, but also requires fi'i abrasion resistance of the roll in order to prevent local wear that impedes roll chance-free formation.

That is, the roll needs to have both abrasion resistance and surface roughness resistance at the same time.

In order to improve rough skin resistance, it is necessary to increase the toughness of the roll material. On the other hand, carbides intended to improve wear resistance reduce toughness. Therefore, it has been extremely difficult to simultaneously satisfy wear resistance and rough skin resistance.

Conventionally, as a method for obtaining a roll outer shell layer that satisfies wear resistance and surface roughness resistance at the same time, the mold is forcibly cooled during roll casting to refine the solidified structure and reduce the size of eutectic carbides. There is a method that satisfies the required characteristics. However, although the refinement of the solidified structure due to mold cooling is satisfactory in a portion close to the mold, the degree of refinement of the solidified structure decreases as the distance from the mold increases. Therefore, it is not possible to satisfy the above-mentioned required characteristics over the entire roll layer.

The present inventor has proposed a method for manufacturing a roll having a strong core material and a toughened outer shell layer in Japanese Patent Application No. 62-14700.
0, we proposed a method in which a core material is first created and an outer shell layer with excellent properties is formed around it by metallurgical bonding.

In this method, a core material is rotatably held concentrically in a rotatable roll mold, and while the mold and core material are rotated, molten metal is poured into the mold to cast the outer shell layer of the roll.

[Problems to be Solved by the Invention] The present invention further develops the above-mentioned proposal, and combines the required amount of carbide and toughness in order to have both wear resistance and roughening resistance in the entire area of the layer used in the roll. An object of the present invention is to provide a method for casting a composite roll having an outer shell layer.

[Means for Solving the Problems 1] The present invention, as a technical means for solving the above-mentioned problems, provides a rotatable core material that can freely adjust the amount of eccentricity from the rotation axis of the mold in a rotatable roll mold. A method for casting a composite roll, comprising: holding the mold at a temperature of 100 mm, rotating the mold and the core material, injecting molten metal into the mold, and casting an outer shell layer of the roll while changing the amount of eccentricity. be.

[Operation 1] In the present invention, the core material is prepared in advance and then cast with the molten metal of the outer shell layer.In order to make the casting structure of the outer shell layer fine, eccentric movement is performed between the core material and the mold. By the action of forging the outer shell layer with molten metal, it is possible to manufacture a composite roll having an outer shell layer with a fine cast structure.

The structure and operation of the present invention will be explained in more detail with reference to FIG.

A cylindrical mold l for casting an outer shell layer is rotated by a roller 4 having a drive system.

The core material 2 is arranged inside the mold 1, and the core material 2 is rotated by a core material rotation device 5.5a having a function of freely changing the eccentricity of the rotation axis of the core material 2 with respect to the rotation axis of the mold l. let

When casting the outer shell layer, in the gap between the core material 2 and the mold l,
A required amount of the outer shell layer molten metal 3 is injected through an injection pipe (not shown). In order to prevent the molten metal immediately after pouring from spilling out of the mold l, it is desirable that the core material 2 and the mold 1 be rotated in the same direction and speed, with zero eccentricity, that is, in a concentric circle.

Immediately after pouring, the outer shell layer molten metal 3 starts solidifying from the contact surface with the mold 1 and the core material 2. When solidification progresses in this state, it becomes a solidified structure obtained by normal centrifugal casting, but the core material 2
By making the rotational axis of the mold eccentric from the rotational axis of the mold (1), a vortex flow and non-uniform pressure distribution are generated inside the outer shell layer molten metal 3. As a result, the solidifying dendrites break,
It floats in the molten metal and becomes the source of forming fine equiaxed products.

At the final stage of solidification, due to the forging effect in the semi-molten state, huge eutectic carbides are destroyed, resulting in a finer structure6. It has hardness and toughness due to its hardness. Therefore, it is excellent in both abrasion resistance and surface roughness resistance required for a roll.

Sufficient feeders are required to move the molten metal during molten metal forging and to replenish the molten metal due to solidification shrinkage. In the present invention, in order to keep the feeder portion warm, a heat insulating material 6 is installed at the contact portion of the mold 1 and the core material 2 with the feeder portion.

[Example] As a specific example of the present invention, the results of applying the present invention to a composite roll using nickel grain cast iron for the outer shell layer and spheroidal graphite cast iron for the core material will be described.

Table 1 shows the chemical compositions of the outer shell layer and core material of the examples.

The size of the roll is body diameter φ780mm, body length 210mm.
0 mm, total length 4900 mm, and target outer shell layer thickness 80 mrn.

A core material of spheroidal graphite cast iron cast in advance was processed to have a body diameter of 630 mm and set at a predetermined position in a mold.

3.7 tons of molten metal in the outer shell layer was cast into a rotating mold at a temperature of 1350°C.

The rotation speed of the mold and core material during casting is 650 rpm (approximately 1
30G), and the eccentricity of the core material was Omm. The direction of rotation of the mold and core material is the same. Immediately after completion of casting, the core material was rotated eccentrically by 1 mm with respect to the center of rotation of the mold.

As the solidification progresses, the torque of the core material increases, so the amount of eccentricity was controlled to be small so that the core material torque did not exceed 50 kgfm.

The roll obtained in the example to which the present invention was applied had a hardness of
s is 79, tensile strength 42 kgf/mm', elongation 1.4%
Met. The comparative roll cast by the conventional method had a hardness of H
s80, tensile strength 40kgf/mrn', elongation 0.
It was 5%. Therefore, in the examples to which the present invention is applied, toughness is improved without reducing hardness.

〔Effect of the invention〕

As described above, the composite roll casting method of the present invention has the following effects.

l) Toughness can be improved without impairing the hardness of the outer shell layer, and rolls with excellent wear resistance and rough skin resistance can be easily manufactured.

2) The core material and the outer shell layer can be metallurgically bonded.

3) A strong material can be used for the core material.

4) The coagulation structure of the outer shell layer can be changed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an apparatus for preferably implementing the present invention. ■...Mold 2...Core material 3...Outer shell layer molten metal 4...Roller 5...Core material rotation device 6...Heat insulation material

Claims (1)

[Claims] 1. A core material whose eccentricity can be adjusted with respect to the rotation center of the mold is rotatably held in a rotatable roll mold, and the mold and the core material are rotated to inject molten metal into the mold. A method for casting a composite roll, characterized in that the outer shell layer of the roll is cast while changing the amount of eccentricity.