JPS60190544A - Heat resistant alloy for hearth member - Google Patents

Abstract

PURPOSE:To obtain a hearth member for a heating furnace having superior oxidation resistance and compressive strength by using a heat-resistant high-alloy Cr-Ni-Co-Mo steel. CONSTITUTION:Hearth rails 4 on skid pipes 3 in a heating furnace 1 for heating a steel slab W or the like to >=1,200 deg.C are made of a heat-resistant high-alloy steel consisting of 0.0.3-0.30% C, 0.2-2.0% Si, 0.3-2.0% Mn, 20-40% Cr, 10-30% Ni, 10-30% Co, 1-10% Mo and the balance Fe. The resulting hearth rails have superior oxidation resistance and compressive strength and react hardly with scale formed on a material to be heated such as a steel slab, so reduction in the surface quality of the material due to a pick-up phenomenon on the material is prevented, and the hearth rails are fit for long period use.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat-resistant alloy used for a hearth member of a heating furnace.

[Conventional technology and interlude]

In a heating furnace used for heating slabs, etc., as shown in Figure 1, a support (2) is installed on the hearth of the heating furnace (1).
Lay the water-cooled skid pipe (3) on the
It is common to have a structure in which a hearth metal (hearth rail) (4) made of a thermal alloy is mounted so that the heated object (W) moves on the hearth metal.

Since this heating furnace is operated at a high temperature of approximately 1200°C, the hearth components must be able to withstand such a high temperature atmosphere.
4) is required to have excellent heat resistance properties, especially oxidation resistance and compressive strength. However, heat-resistant alloys that have conventionally been widely used as hearth metal lv materials, typically 0r-Ni-Fe steel and 0r-Ni-Co-Fe steel, do not have the above-mentioned properties (especially compressive strength). is not sufficient, leading to problems with durability.

As a hearth metal material with particular emphasis on high-temperature properties, high C
o alloy (50%C020%Or -Fe), but
The disadvantage of this product is that it is extremely expensive because it contains a large amount of CO.

[Purpose of the invention]

The present invention solves the problem 1.
To provide a heat-resistant alloy that has improved oxidation resistance and compressive strength while reducing energy consumption, and enables long-term stable use as a hearth metal.

[Structure of the invention]

The heat-resistant alloy for hearth members of the present invention has a C: 0.03 to 0.3.
%, Si: 0.2~2.0%, Mn: 0.3~
2.0%, (Jr: 20.0-40.0%, Ni:
10.0~300%, Co:to, o~30.0%, M
o: 1, Q-1, 0.0%, the remainder substantially consisting of Fe. All percentages indicating component content are by weight.

The reasons for limiting the ingredients of the heat-resistant alloy of the present invention are as follows.

C: o, 03~0.3% C is dissolved in austenite and improves the hardness of the base, and also combines with nitrogen and Mo to form carbides, which is effective in improving strength at high temperatures. do. For this, at least 0.03%
content. However, when the content increases,
0.3% as it will lower the melting point of the alloy and deteriorate the high-temperature strength.
Do not exceed.

Therefore, it is more preferably 0.03 to 0.3%.
．． 05-0.15%.

8i; 0.2 to 2.0% Si is a deoxidizing agent during alloy melting, and the molten metal flow #J
It is a useful element for improving castability and ensuring castability. 0
．． If it is less than 2%, the effect is insufficient, while 2.0%
Exceeding this results in a decrease in high temperature strength and weldability. Therefore, it should be 0.2 to 20%, more preferably 0.4 to 1
．． It is specified in the range of 5%.

Mn: 0.3 to 2.0% Mn has the effect of deoxidizing the molten alloy and improving castability. For this purpose, 0.37% or more is required,
If it exceeds 2.0%, high temperature strength will decrease.

Therefore, it is set at 0.3 to 20%. More preferably 0.
It is 5-1.5%.

Cir: 20.0-40.0% Or increases oxidation resistance at high temperatures. To ensure this effect, at least 20.0% is required. The effect increases as the content increases, but when it exceeds 40.0%, the castability and weldability deteriorate significantly. Therefore, 20.0~
It shall be 40.0%. More preferable content is 25,0-3
It is 5.0%.

Ni: 10.0 to 30.0% Ni is an element that is effective in stabilizing the austenite structure and improving the stability and compactness of the oxide film, and is also effective in increasing the high 77111 strength. 10.0% or more is required to exhibit these effects, but 30.0%
When it exceeds , the effect becomes saturated.

Therefore, it is set to 100 to 300%. More preferably 15
．． It is 0 to 25.0%.

Co:　Ioo~30,0% CO has a remarkable effect on improving oxidation resistance and high temperature strength.

At least 10.0% is required to ensure this effect.

As the content increases, the effect increases, but if it exceeds 30.0%, the increase in effect is small relative to the content, which impairs economic efficiency. Therefore, it is set to 10.0 to 30.0%. More preferably it is 15.0 to 250%.

Mo: 1, Q ~ 10.0% MO contributes to improving high temperature strength. If it is less than 1.0%, the effect will be insufficient. The effect increases as the content increases, but when it exceeds 10.0%, the oxidation resistance decreases significantly. Therefore, it is defined as 1.0 to 10.0%, more preferably 2.0 to 60%.

Although it is desirable that P, S, and other impurity elements be small in terms of ri'JTL, unavoidable mixing of I-IJ due to normal melting technology is allowed. For example, P is 0.04% or less, S is 0.04% or less.
Even if the content is less than 0.04%, the spirit of the present invention is not impaired.

〔Example〕

Examples of chemical composition of the alloy of the present invention and compression resistance at high temperatures,
Table 1 shows the oxidation resistance compared to conventional alloys. Fragrances 1 to 8 are examples of the present invention, and fragrances 101 to 104 are conventional alloys. Compression resistance is measured at a stress of 0.0 at 1200°C.
The compression deformation rate (%/I(r)) at 7 kg/-, and the oxidation resistance are expressed as the oxidation rate (fl/n/-Hr) at 1200°C and 200 hours of storage (atmospheric atmosphere).

As shown in Table 1, the conventional rate of 0r-Ni-Co-
Fe; 14'f$J (fragrance 102.103) and O
Both the compressive strength and oxidation resistance of r -N i, -Fe series steel (Fuka 104) are not as good as those of the inventive example. The high Co--Cr--Fe steel of 101 has a compressive strength comparable to that of the alloy of the present invention, but is inferior to the alloy of the present invention in terms of poor oxidation resistance.

It can be seen that the alloy of the present invention has excellent compressive strength and oxidation resistance, and is suitable as a hearth member.

〔Effect of the invention〕

The alloy of the present invention has excellent high-temperature properties and has compressive strength and oxidation resistance superior to conventional alloys. Moreover, the conventional high C
Since it does not require a large amount of Co unlike the O alloy, it is extremely advantageous in terms of cost.

The alloy of the present invention is suitable as a material for forming the hearth of heating furnaces such as hearth metals, skids, and riders, and has a stable length that cannot be obtained with conventional materials at high temperatures of 1200°C or higher. Guarantees service life. - Also, due to the lack of oxidation resistance in conventional hearth metals made of alloys, scale (oxides) may melt and build up on the contact surface with the heated material placed on top of the hearth metal. A so-called pickup phenomenon occurs, which causes damage to the surface quality of the heated material such as a slab.
The alloy of the present invention has little reactivity with scale, and is therefore effective in improving the surface quality of the heated material.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view showing an example of a hearth structure of a heating furnace. 1: heating furnace, 3: skid pipe, 4: hearth metal. Agent Patent Attorney Miyazaki Shinhachibe

Claims (2)

[Claims] (1) C': 0.08-0. B 0%, 8i:
0.2-2.0%, Mn: 0.3-2.0%, O
r: 20.0-40.0%, Ni: 1o, o
~a o, o%, co:to, o ~30.0%, MO
:l, Q ~ 10.0%, the balance substantially consisting of Fe for a heat-resistant alloy for hearth members. (2) C: 0.05-0.15%, si: 0.4
~1.5%, Mn: 0.5~1.5%, Cr;
25.0-85.0%, Ni:I5.0-25.0%,
C'O: 15.0-25.0%, io to I: 2. Q~6
．． The heat-resistant alloy for a hearth member according to item (1) above, which consists of 0% Fe and the remainder substantially Fe.