JPH0693328A - Hearth roll using oxide dispersion strengthend alloy - Google Patents

Abstract

PURPOSE:To obtain a hearth roll high in heat resistance and oxidation resistance and having a service life longer than that of a conventional roll. CONSTITUTION:The hearth roll of a heating furnace heating a slab and wire rod for hot rolling is produced by fitting a hearth roll member produced by an oxide dispersion strengthened alloy to a stub shaft made of heat resistant stainless steel. The oxide dispersion strengthened alloy is a one obtd. by dispersing, by weight, 0.1 to 2% high m.p. metallic oxides such as Y2O3 into an austenitic matrix of an alloy contg. 24 to 40% Cr, <=5% Fe, <=5% Al and <=5% Ti, and the balance substantial Ni, particularly, that produced by a mechanical alloying method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a hearth roll used in a heating furnace for heating a steel slab or a wire in preparation for rolling in the steel industry, for example.

[0002]

2. Description of the Related Art Up to now, heat-resistant casting alloys, typically Ni-base superalloys, have been used as materials for hearth rolls. However, since the temperature reaches 1100 to 1350 ° C. in the soaking zone of the heating furnace, the hearth roll is severely deformed and worn, and has a short life.

As a countermeasure against this, at present, the roll is water-cooled to extend the life. However, the water-cooling complicates the structure of the heating furnace, increases the equipment cost, increases the fuel cost, and causes uneven heating. Causes the problem of becoming.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to utilize the technology of dispersing and strengthening an oxide in a heat-resistant superalloy to add heat distortion resistance, wear resistance, impact resistance and oxidation resistance. It is to provide a hearth roll of a heating furnace having excellent properties.

[0005]

A hearth roll for a heating furnace of the present invention is a hearth roll for a heating furnace in which a heat-resistant stainless steel stub shaft is attached to a hearth roll member. ~ 4
0% Cr, 5% or less Fe, 5% or less Al and 5
% Of Ti and the balance is substantially Ni, and an oxide dispersion strengthened alloy in which 0.1 to 2% of fine refractory metal oxide is dispersed in an austenite matrix of the alloy is used. Characterize.

As the refractory metal oxide, Y ₂ O ₃ , Zr
It is recommended to use one or more selected from O ₂ , Al ₂ O ₃ , Ce ₂ O ₃ , Gd ₂ O ₃ , Sc ₂ O ₃ and Eu ₂ O ₃ . In order to manufacture the above hearth roll member, yttria Y _{2 is} added to the metal or alloy giving the above alloy composition.
A high melting point metal oxide such as O ₃ may be mixed, the mixture may be treated by a mechanical alloying method, and the resulting alloy powder may be hot worked to give a desired roll member shape.

In the mechanical alloying method, pure metal or alloy particles as an alloy component and fine crystals of a refractory metal oxide are put in a ball mill, for example, a high kinetic energy type ball mill, and crushing and welding associated therewith are repeated. This is a technique for obtaining a granular product consisting of an intimate and uniform mixture of fine powders of the respective components. As subsequent hot working techniques, there are HIP (hot isostatic pressing), hot extrusion, vacuum hot pressing, and a method combining these with forging.

[0008]

In the hearth roll of the present invention, the reason why the alloy composition of the hearth roll member is determined as described above is as follows.

Cr: 20-40% At least 20% for improving the oxidation resistance at high temperature.
Must be included. If it is too large, the austenite structure becomes unstable, resulting in a decrease in toughness.

Al: 5% or less, Ti: 5% or less These metals are added to enhance the oxidation resistance of the alloy. Addition of a large amount lowers the melting point, so the content should be within the above limits.

Refractory metal oxide: 0.1 to 2% Needless to say, it is dispersed in a Ni base to enhance its high temperature strength. This effect is obtained by adding 0.1% or more, and
%, And then becomes saturated at 2%.

[0012]

[Example] "INCONEL Alloy MA75
Various refractory metal oxides are dispersed in a heat-resistant alloy having a composition based on "8", and the composition shown in Table 1 (% by weight, balance Ni)
An oxide dispersion strengthened alloy having the above was prepared into particles by a mechanical alloying method.

[0013]

[Table 1]

The above alloy particles were hot extruded and machined to obtain test pieces. For comparison, "DCH27" alloy (0.36C-33Cr-30Ni-5W-0.3Ti) that has been used as a material for hearth rolls has been used.
-Fe) was taken up and a similar test piece was prepared.

Each material was first subjected to a compression test at an ultrahigh temperature to compare the durability as a hearth roll material. The amount of deformation under each test condition is as shown in Table 2.

[0016]

[Table 2]

No. Focusing on 1 alloy at 1300 ° C. and a stress of 0.4 kgf / mm2 for 3 hours, the amount of deformation of the conventional product reached 5.9%.
Good results could be confirmed with only 28%.

Next, a test of heating at 1200 ° C. for a long time in the atmosphere was conducted to measure the increase in oxidation. The results are shown in Table 3, and it can be seen that according to the present invention, the amount of increase in oxidation is 1/10 or less of the conventional material.

[0019]

[Table 3]

[0020]

EFFECTS OF THE INVENTION According to the present invention, when an oxide dispersion strengthened alloy is used for a hearth roll member to form a hearth roll, it can withstand a high temperature in a heating furnace and has a long life. In the example in which the present invention is applied to the hearth roll used in the soaking zone of the actual wire rod heating furnace, the life is more than 10 times that of the conventional product.

Claims (2)

[Claims] 1. In a hearth roll of a heating furnace in which a heat-resistant stainless steel stub shaft is attached to a hearth roll member, the weight of the hearth roll member is 20% by weight.
.About.40% Cr, 5% or less Fe, 5% or less Al and 5% or less Ti, with the balance being substantially Ni, with a fine refractory metal oxide in the austenite matrix being 0. A hearth roll characterized by using an oxide dispersion strengthened alloy in which 1 to 2% is dispersed. 2. Y ₂ O ₃ , Zr as the refractory metal oxide
The hearth roll according to claim 1 or 2, wherein one or more selected from O ₂ , Al ₂ O ₃ , Ce ₂ O ₃ , Gd ₂ O ₃ , Sc ₂ O ₃ and Eu ₂ O ₃ is used.