JPH0584570A - Production of hot conveying roller - Google Patents

Abstract

PURPOSE:To provide a manufacturing method of a roller used for conveying hot rolled material. CONSTITUTION:After cladding by welding is performed by using heat resistant material 2 formed by adding 30-50vol.% NbC to 3Cr-1Ni base on the surface of base metal 1 worked into a roller shape, this is finished and afterward, heat-treated in an acid atmosphere containing <5% CO gas, by which solid oxidized scales excellent in wear resistance and burning resistance mainly composed of Fe3O4 and FeO are generated on the roller surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a hot-rolling roller suitable for transporting hot-rolled material such as seamless steel pipe.

[0002]

2. Description of the Related Art For example, a hot-rolling roller (hereinafter simply referred to as a roller) used for transporting a hot-rolled material (hereinafter simply referred to as a hot-rolled material) such as a seamless steel pipe slips between the hot-rolled material and the like. When this occurs, sticking such as seizure occurs on both surfaces, and this sticking damages both surfaces. That is, when the contact pressure and contact heat on both contact surfaces are large, plastic deformation occurs, the atoms of each other form a solid solution and adhere, and the shearing force acts due to relative motion, causing shearing in a weak cross section. It sticks to one side and it hurt the other side.

As a measure to prevent the adhesion between the two surfaces, a conventional method of preventing direct contact with a lubricating film or a method of using ductile cast iron such as FCD45 having good seizure resistance, such as S45C, etc. There is a method of overlay welding 13Cr stainless steel to the base metal of. However, in the case of, the lubricating film lowers the coefficient of friction, slipping is likely to occur, and conveyance failure may occur, or it is necessary to uniformly apply the lubricating film to the roller surface. However, there is a drawback that the cost will increase due to equipment cost and lubricating oil cost. In addition, in the case of 1, since the wear of the ductile cast iron is severe, a step is generated at a portion of the roller surface which is always used, and the hot material is damaged.
Further, when 13Cr-based stainless steel is built up, the wear resistance is good, but when the stainless steel material is rolled, the seizure resistance is slightly inferior.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems of the roller for conveying the hot material, and wear resistance in which no adhesion occurs between the two surfaces. An object of the present invention is to provide a method for manufacturing a hot transport roller having excellent heat resistance and seizure resistance.

[0005]

According to the present invention, 30 to 50 vo of 3Cr-1Ni system NbC is formed on the surface of a base material processed into a roller shape.
This is a method for manufacturing a hot conveying roller, characterized in that overlay welding is performed using a heat-resistant material added with 1%, finishing processing is performed, and then heat treatment is performed in an acidic atmosphere containing less than 5% CO gas.

[0006]

[Working] As a result of repeated intensive research experiments to solve the above-mentioned problem of adhesion of a conventional roller, the present inventor has conducted overlay welding on the surface of the roller and then provided a strong oxide scale. Was found to be an effective anti-seizure measure. That is, as a material for overlay welding, 3Cr-1Ni
System (mainly C; 0.30wt%, Cr; 3.0wt%, Ni; 1.1w
A heat-resistant material with t% and balance Fe) to which NbC (ceramics) is added in an amount of 30 to 50 vol% is suitable for further enhancing wear resistance and seizure resistance. Further, as a heat treatment technique for forming an oxide scale, for example, a heat treatment method disclosed in Japanese Examined Patent Publication No. 59-9628 is used, and the heat treated member is less than 5%.
It is suitable to produce a strong oxide scale such as Fe ₃ O ₄ or FeO having excellent wear resistance and seizure resistance on the surface of the heat-treated member by heat treatment in an oxidizing furnace atmosphere containing CO gas. is there.

The reason for limiting the NbC added here will be described with reference to FIG. This figure shows that the amount of NbC added is 0 vol when overlay welding is performed using 3Cr-1Ni system as the base material of S45C.
Performance when changing from 60% to 60 vol%, that is, scale thickness (μm) (○ mark), scale hardness (Hmv)
(□ mark), overlay hardness (Hv) (Δ mark), hammer impact frequency (adhesion test; N number) (x mark). In the figure. As is clear from this figure, the NbC range in which it is judged that the two performances of scale hardness and adhesion test, which are the most important factors in oxidative scaling, are good and other performances are not significantly impaired is 30. It turns out that it is ~ 50 vol%.

The heat pattern of the heat treatment used at this time was, as shown in FIG. 3, heated and held at 950 ° C. for 4 hours, cooled at 30 ° C./h, and reached 500 ° C. and then air cooled. In addition, the above-mentioned hammer impact frequency is for the purpose of judging the degree of adhesion, and it is an oxidation scale when a hammer with a weight of 0.6 kg is used to freely fall on a test piece from a height of 50 mm with impact energy of 0.59 J. The number of impacts until peeling occurs is expressed as N number.

[0009]

EXAMPLES Examples of the present invention will be described below.
FIG. 1 is a cross-sectional view showing the outline of the hot transport roller of the present invention, in which S45C as the base material 1 has an outer diameter D of the flange portion of 340 mm.
After being processed into a U-shaped roller of φ with a center diameter d of 260 mm φ and a length L of 200 mm, 3Cr-1Ni system + 40vol% NbC as the overlay material 2 was applied to the surface of the roller. Welded to a thickness of 3 mm and finished to a thickness of 1.5 to 2 mm.
_{Then, CO 2; 10%, CO} ; 2~3%, O 2; 0%, H 2 O;
In a heat treatment furnace (not shown) in an atmosphere with a slight amount of balance N ₂ , heat and hold at 950 ° C for 4 hours, then cool at 30 ° C / h, then 500
When it reached ℃, it was cooled by air.

FIG. 4 is a micrograph (magnification: 100) of the cross-sectional microstructure of the oxide scale layer after heat treatment. Also,
Table 1 shows the measured hardness values of the oxide scale layers I and II and the overlay layer shown in the figure. As you can see from these characteristics,
The oxide scale layer I contains porous and brittle Fe ₂ O ₃ as a main component and a small amount of Fe ₃ O ₄ mixed therein, whereas the oxide scale layer II contains hard Fe ₃ O ₄ and FeO as main components and meat. Excellent adhesion to the layer.

[0011]

[Table 1]

Using the U-shaped conveying roller of the present invention in which the oxide scale layer I is removed and only the oxide scale layer II is used, finish rolling of 13Cr having an outer diameter of 120 mmφ and a temperature of 1000 to 1050 ° C. is carried out. Although 250 pieces of stainless seamless steel pipe were conveyed, there was no seizure phenomenon that confirmed the occurrence.

[0013]

As described above, according to the present invention, 3C
R-1Ni-based heat-resistant material with 30 to 50 vol% NbC added is used for overlay welding, and then heat treatment is performed in an acidic atmosphere containing less than 5% CO gas, so wear resistance and seizure resistance are improved. It is possible to manufacture excellent and strong hot transfer rollers,
As a result, not only the quality and yield of products can be improved, but also the cost can be reduced due to the extension of the life of the transport roller.

[Brief description of drawings]

FIG. 1 is a sectional view showing an outline of a hot transport roller of the present invention.

FIG. 2 is a characteristic diagram showing various performances when the amount of NbC added to a 3Cr-1Ni-based build-up material is changed.

FIG. 3 is a characteristic diagram showing an example of a heat treatment pattern used for oxide scale attachment.

FIG. 4 is a micrograph of an oxide scale layer.

[Explanation of symbols]

 1 base material 2 overlay material

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[Procedure amendment]

[Submission date] July 30, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

FIG. 4 is a micrograph showing a metal structure of an oxide scale layer.

Claims (1)

[Claims] 1. A surface of a base material processed into a roller shape is overlay-welded with a heat-resistant material in which 30 to 50 vol% of NbC is added to a 3Cr-1Ni system, and then finish processing is performed, and then CO of less than 5% is used. A method for manufacturing a hot carrier roller, comprising heat treatment in an acidic atmosphere containing gas.