JPH05163552A - Boiler alloy excellent in erosion resistance - Google Patents

Abstract

PURPOSE:To develop a boiler alloy excellent in erosion resistance by adding specified amts. of Co, Cr, Ni, Mo, W, etc., to a low-carbon steel. CONSTITUTION:The alloy contains, by weight, <=1% C, 0.2-2.5% Si, <=1.0% Mn, <=0.03% P, <=0.005% S, 10-25% Co, 18-28% Cr, one or >=2 kinds among 10-50% Ni, 2-4% Mo and <=8% W and the balance Fe. In this case, one or >=2 kinds between <=0.2% Hf and <=0.2% Zr or one or >=2 kinds among <=0.1% Y, <=0.1% La and <=0.1% Ce are incorporated, as required, singly or compositely to produce the alloy fulfilling inequalities I and II. An alloy material excellent in erosion resistance is obtained in this way as the high-temp. boiler material at >=400 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiler alloy having excellent erosion resistance, and more particularly to an alloy having excellent resistance characteristics against high temperature particle erosion. The alloy of the present invention is
For example, it exhibits excellent performance when used as a tube in a coal-fired boiler.

[0002]

2. Description of the Related Art A high temperature apparatus represented by a fuel combustion boiler, a fluidized bed reactor, a coal gasification or liquefaction apparatus, etc. has been designed to utilize coal in consideration of recent energy circumstances. .. For example, in a fuel-fired boiler, petroleum products have hitherto been mainly used as fuel, but recently, there is an increasing tendency to use coal as fuel because of the need to use alternative energy for oil. However, these high temperature devices are designed according to the design concept when using petroleum products as fuel, and the problems when using coal as fuel have not been sufficiently solved. For example, also in a coal fired boiler, the device is manufactured with the same material configuration as in a conventional oil fired boiler. However, unlike a coal-fired boiler, unlike a petroleum-fired boiler, the solid ash content falls inside the boiler as a clinker and floats as fly ash, so the equipment (boiler, etc.) undergoes significant erosion at high temperatures. ..

Although such problems in high-temperature equipment are well recognized by those skilled in the art, the problem has not yet been sufficiently clarified, and few measures have been taken in terms of materials.
Empirical design measures, such as reducing combustion gas velocity,
Only measures such as mounting a protector are taken. However, even if measures are taken to reduce the flow rate of combustion gas, a drift part with a higher flow velocity than expected can be created,
Even when taking steps to mount the protector, the protector is often damaged quickly, and the essential problem is often not solved.

On the other hand, as a boiler tube, SUS
304 steel, SUS321 steel, SUS347 steel, SUS3
Austenitic stainless steels such as 16 steel, and alloys such as Incoloy 800 and SUS310 steel are known. Further, in general, various austenitic stainless steels are used as high temperature members, but none of these materials considers high temperature resistant particle erosion, and are used based on experience in oil fired boilers and the like. I'm just there.

As described above, in the present situation, almost no measures have been taken in terms of materials for preventing erosion due to high temperature particles. If measures for preventing erosion due to high-temperature particles are established in terms of materials, it is possible to make room for the design of the high-temperature device, downsize the device, and further improve thermal efficiency.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a material having excellent resistance properties to erosion by hot particles, such as in a coal fired boiler.

[0007]

The subject matter of the present invention is as follows. (1) C ≦ 0.1% by weight, Si: 0.2 to 2.5
%, Mn ≦ 1.0%, P ≦ 0.03%, S ≦ 0.005
%, Co: 10 to 25%, Cr: 18 to 28%, Ni:
10 to 50%, and Mo: 2 to 4%, W ≦ 8
%, One or two, and the balance Fe and unavoidable impurities, and 0.5Co + Ni + 1.5Cr ≦ 75 1.2 ≦ (Ni + Cr) / (Co + Mo + 1/2 · W) ≦ 2.8. Boiler alloy with excellent erosion resistance, which is characterized by satisfaction.

(2) C ≦ 0.1% by weight, Si:
0.2-2.5%, Mn ≦ 1.0%, P ≦ 0.03%,
S ≦ 0.005%, Co: 10 to 25%, Cr: 18 to
28%, Ni: 10 to 50%, and Mo: 2
.About.4%, one or two of W.ltoreq.8%, and Hf.ltoreq.0.
2%, 1 or 2 of Zr ≦ 0.2%, balance Fe and unavoidable impurities, and 0.5Co + Ni + 1.5Cr ≦ 75 1.2 ≦ (Ni + Cr) / (Co + Mo + 1/2 · W ) ≦ 2.8, an alloy for boilers having excellent erosion resistance, which is characterized by satisfying the following condition.

(3) C ≦ 0.1% by weight, Si:
0.2-2.5%, Mn ≦ 1.0%, P ≦ 0.03%,
S ≦ 0.005%, Co: 10 to 25%, Cr: 18 to
28%, Ni: 10 to 50%, and Mo: 2
~ 4%, 1 or 2 with W ≤ 8%, and Y ≤ 0.1
%, La ≦ 0.1%, Ce ≦ 0.1%, or a combination of two or more, balance Fe and unavoidable impurities, and 0.5Co + Ni + 1.5Cr ≦ 75 1.2 ≦ (Ni + Cr) An alloy for boilers having excellent erosion resistance, which satisfies the condition: /(Co+Mo+1/2·W)≦2.8.

(4) C ≦ 0.1% by weight, Si:
0.2-2.5%, Mn ≦ 1.0%, P ≦ 0.03%,
S ≦ 0.005%, Co: 10 to 25%, Cr: 18 to
28%, Ni: 10 to 50%, and Mo: 2
~ 4%, 1 or 2 with W ≤ 8%, Hf ≤ 0.2%,
1 or 2 of Zr ≦ 0.2%, and Y ≦ 0.1
%, La ≦ 0.1%, Ce ≦ 0.1%, or a combination of two or more, balance Fe and unavoidable impurities, and 0.5Co + Ni + 1.5Cr ≦ 75 1.2 ≦ (Ni + Cr) An alloy for boilers having excellent erosion resistance, which satisfies the condition: /(Co+Mo+1/2·W)≦2.8.

The present invention will be described in detail below. First, the reasons for limiting the components in the present invention will be described. C is an element that enhances the strength of the alloy. However, if added in excess of 0.1%, not only the workability of the steel is deteriorated, but also intergranular corrosion cracking easily occurs. Therefore, it is added within the range of 0.1% or less.

Si effectively functions as a deoxidizing element.
Therefore, it is necessary to contain at least 0.2%. However, if its content exceeds 2.5%, the hot workability of steel deteriorates. Like Mn, Mn effectively functions as a deoxidizing element. However, if added in excess of 1.0%, the steel becomes brittle, so addition is made within the range of 1.0% or less.

P is an unavoidable impurity. If the content exceeds 0.03%, the segregation of the grain boundaries of the steel becomes significant.
S is an unavoidable impurity. The content is 0.005
%, The hot workability of steel deteriorates significantly. Co
Improves the erosion resistance of the steel by coexisting with Ni, Cr, Mo and W. If the content is less than 10%, the effect of addition will not be exhibited. Further, the Co content is 10
%, It is necessary to add a large amount of other alloy elements in order to secure the erosion resistance of the steel, which is not economical.
On the other hand, if its content exceeds 25%, the workability of steel deteriorates.

Ni is an element that improves the corrosion resistance of steel, and if its content is less than 10%, the effect of addition is not exhibited. Further, if the Ni content is less than 10%, it is necessary to add a large amount of other alloying elements in order to secure the corrosion resistance of the steel, which is not economical. On the other hand, the effect of addition of Ni is saturated when the addition amount is 50%. Cr improves the corrosion resistance of steel by coexisting with Ni, Mo and W. Its content is 18%
If it is less than the above, the effect of addition is not exhibited. On the other hand, the effect of Cr addition is saturated at 28%.

Mo improves the erosion resistance of steel together with Co. Increase the hardness of steel by adding Mo,
This has the effect of improving erosion resistance. If the content is less than 2%, the effect of addition is not exhibited. On the other hand, the effect of adding Mo is saturated at 4%. W, like Mo, improves the erosion resistance of steel. The addition of W has the effect of increasing the hardness of the steel and thus improving the erosion resistance. However, addition of more than 8% does not improve the effect but also deteriorates the workability of steel.

Among the above alloy elements, Co, Ni, C
r, Mo and W improve the erosion resistance and corrosion resistance of steel, but if each element is added alone,
The effect of addition is not expressed, and the effect of addition is expressed only by combined addition. The present inventors have conducted research to obtain a material that exhibits excellent erosion resistance in a high temperature boiler of 400 ° C. or higher, and as a result, (1) the content of Co, Ni, and Cr is 0. 5Co + Ni + 1.5Cr ≦ 75 (2) Between each content of Ni, Cr, Co, Mo and W, 1.2 ≦ (Ni + Cr) / (Co + Mo + 1/2 · W) ≦
It was newly found that when the relationship of 2.8 is satisfied, excellent characteristics can be exhibited in the above addition amount range.

Hf improves the high temperature strength of steel by adding a trace amount of 0.2% or less. Zr functions as a deoxidizing element when added in an amount of 0.2% or less. Y, La and Ce exhibit the effect of further improving the hot workability of steel. Therefore, when hot working of steel is performed under severe conditions, it is added as necessary. The effect of addition of any of the above elements is saturated when the addition amount is 0.1%.

[0018]

EXAMPLES 1 ton of each of the alloys having the composition shown in Tables 1 to 4 was melted using a vacuum induction heating furnace, and further E
It was subjected to SR treatment for cleaning and cast into an ingot having a cross-sectional dimension of 500 mm × 250 mm. This ingot was hot rolled into a plate material having a thickness of 7 mm, and then 1050
It was kept at a temperature of 30 ° C. for 30 minutes and cooled with water (heat treatment). From the plate material thus obtained, the thickness is 2 m at right angles to the rolling direction.
A test piece of m, width: 15 mm, length: 20 mm was cut out.

An erosion test was carried out by placing this test piece in an apparatus maintained at 400 ° C. and injecting coal sized to a diameter of 2 mm for 500 hours. The degree of erosion of the test piece before and after this erosion test was observed. The results are shown in Tables 2 and 4. Table 2,
In 4, the ○ mark has no dent on the surface of the test piece, ×
The mark indicates that a clear depression was recognized on the surface of the test piece.

An alloy satisfying the component conditions specified in the present invention exhibits excellent erosion resistance.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[Table 4]

[0025]

According to the present invention, it is possible to provide an alloy having excellent properties that can be used in an environment that is subjected to severe erosion, such as a coal-fired boiler.

Claims (4)

[Claims] 1. By weight, C ≦ 0.1%, Si: 0.2-
2.5%, Mn ≦ 1.0%, P ≦ 0.03%, S ≦ 0.
005%, Co: 10 to 25%, Cr: 18 to 28%,
Ni: 10 to 50% contained, and Mo: 2 to 4%,
W ≦ 8% of 1 type or 2 types, balance Fe and unavoidable impurities, and 0.5Co + Ni + 1.5Cr ≦ 75 1.2 ≦ (Ni + Cr) / (Co + Mo + 1/2 · W) ≦ 2.8. Boiler alloy with excellent erosion resistance, which satisfies the following conditions. 2. By weight, C ≦ 0.1%, Si: 0.2 to
2.5%, Mn ≦ 1.0%, P ≦ 0.03%, S ≦ 0.
005%, Co: 10 to 25%, Cr: 18 to 28%,
Ni: 10 to 50% contained, and Mo: 2 to 4%,
1 or 2 with W ≦ 8%, and Hf ≦ 0.2%, Z
Contains 1 or 2 of r ≦ 0.2%, balance Fe and unavoidable impurities, and 0.5Co + Ni + 1.5Cr ≦ 75 1.2 ≦ (Ni + Cr) / (Co + Mo + 1/2 · W) ≦ 2 An alloy for boilers having excellent erosion resistance, which is characterized by satisfying the following condition. 3. C ≦ 0.1% by weight, Si: 0.2 to
2.5%, Mn ≦ 1.0%, P ≦ 0.03%, S ≦ 0.
005%, Co: 10 to 25%, Cr: 18 to 28%,
Ni: 10 to 50% contained, and Mo: 2 to 4%,
One or two of W ≦ 8%, and Y ≦ 0.1%, La
≦ 0.1%, Ce ≦ 0.1%, one or more kinds, and the balance Fe and unavoidable impurities, and 0.5Co + Ni + 1.5Cr ≦ 75 1.2 ≦ (Ni + Cr) / (Co + Mo + 1) / 2 · W) ≦ 2.8 A boiler alloy with excellent erosion resistance, characterized by satisfying the following condition. 4. C ≦ 0.1% by weight, Si: 0.2 to
2.5%, Mn ≦ 1.0%, P ≦ 0.03%, S ≦ 0.
005%, Co: 10 to 25%, Cr: 18 to 28%,
Ni: 10 to 50% contained, and Mo: 2 to 4%,
One or two of W ≦ 8%, Hf ≦ 0.2%, Zr ≦
0.2% 1 or 2 and Y ≦ 0.1%, La
≦ 0.1%, Ce ≦ 0.1%, one or more kinds, and the balance Fe and unavoidable impurities, and 0.5Co + Ni + 1.5Cr ≦ 75 1.2 ≦ (Ni + Cr) / (Co + Mo + 1) / 2 · W) ≦ 2.8 A boiler alloy with excellent erosion resistance, characterized by satisfying the following condition.