JPS60258445A - Cobalt base heat resistant alloy - Google Patents

Abstract

PURPOSE:To improve the resistance to compression, corrosion and oxidation at high temp. by adding prescribed percentages of C, Si, Mn, Cr, Fe, Hf, Mo and W to Co. CONSTITUTION:This Co base heat resistant alloy consists of, by weight, 0.2- 0.7% C, 0.1-3% Si, 0.1-2% Mn, 25-35% Cr, 1-30% Fe, 0.001-0.45% Hf and the balance Co or further contains 0.1-10% Mo and/or 0.1-10% W. The alloy has superior resistance to compression, corrosion and oxidation at high temp.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides excellent product temperature compression resistance, high temperature oxidation resistance, high temperature corrosion resistance, and same temperature resistance, especially in high temperature combustion atmospheres such as heavy oil and blast furnace gas. The present invention relates to a CO-based heat-resistant alloy that exhibits wear resistance (hereinafter, these are collectively referred to as high-temperature properties).

[Conventional technology]

In general, for example, heating furnaces, soaking furnaces, or heat treatment furnaces for steelmaking use fuel such as heavy oil or blast furnace gas. The hearth member is 1000 to 1
It is exposed to a high-temperature combustion atmosphere of 200℃ and contains highly corrosion-resistant and oxidizing substances such as nasilum oxidized parts (V oxides) and sulfur oxides (S oxides). Moreover, the conditions under which these furnaces are used are becoming increasingly severe.

Under such circumstances, currently, the manufacturing of structural members for these furnaces mainly requires Fe -30ft=cr -22t
I) Fe-based heat-resistant alloy having a composition of Ni or Co-28
A CO-based heat-resistant alloy with a composition of 1Cr-20%Fe is used.

[Problem that the invention seeks to solve]

However, the former Fe-based heat-resistant alloy does not exhibit satisfactory high-temperature properties when used under particularly harsh conditions, while the latter CO-based heat-resistant alloy exhibits better high-temperature properties than the Fe-based heat-resistant alloy. However, these alloys do not have sufficient hot and humid compression resistance in the above-mentioned high-temperature combustion atmosphere of 1000 to 1200°C, and for this reason, the range of use of these alloys is currently limited.

[Means for Solving the Problems] Therefore, from the above-mentioned viewpoint, the present inventors conducted research to develop a material with excellent high-temperature properties, and as a result, in weight %, C: 0.2 More than 0.7 chi.

Si: 0.1-3%.

Mn: 0.1-2%.

Cr: 25-35%.

Fe: 1-30chi.

Hf:0. OOl~0.45%.

and, if necessary, Mo: 0.1 to 10 and W: 0.1 to 10.
One or two of the following: Ti: 0.1 to 2 Ti.

Nb: 0.1-2%.

A CO-based alloy containing one or more of Ta: 0.1 to 2%9, or both, with the remainder consisting of CO and inevitable ζ impurities, is particularly preferred. In a high-temperature combustion atmosphere of ℃ and containing extremely corrosive and oxidizing V oxides and Se oxides,
Excellent high temperature properties, namely high temperature compression resistance, sieve temperature oxidation resistance, and madder temperature corrosion resistance.

We obtained the knowledge that it exhibits high temperature wear resistance.

This invention was made based on the findings described in -, and the reason why the component composition range was limited as described above will be explained below.

(a) CC The C component includes Cr*W*Hf?, which improves strength (compression resistance) by solid solution in the base material and is an alloy component.
Furthermore, it combines with Mo, Ti, Nb, Ta, etc. to form carbides such as M7C31MC and M23C6 types to improve hardness and wear resistance).
It has the effect of improving weldability and castability, but if the content is less than 0.2%, the desired effect cannot be obtained, and if the content exceeds 0.7%, the carbide Not only will precipitation increase, but the grain size will also become coarser, reducing toughness and lowering the melting point of the substrate, causing a decrease in heat resistance.
It was set at 7%.

fb) 5i Si component, together with Cr, has the effect of improving high-temperature corrosion resistance and high-temperature oxidation resistance in a high-temperature combustion atmosphere, and also has a deoxidizing effect and an effect of improving the fluidity of bath water and improving castability. It has the effect of improving high-temperature compression resistance (high-temperature strength), but if its content is less than 0.1%, the desired effect cannot be obtained, while if it is contained more than 3%, , since toughness and weldability decrease in relation to Cr, the content should be increased from 0.1 to
It was set as 3.

In addition, since the S'l component has a deoxidizing effect as mentioned above, when it is used as a deoxidizing agent, it may be contained in the range of 0.1% as an unavoidable impurity. However, in this case, the total content, including the content of unavoidable impurities, should be 0.1% or more.

(c) Mn In addition to stabilizing austenite by solid solution in the base material, the Mn component has a deoxidizing effect and also has the effect of improving thermal shock resistance and high-temperature wear resistance (high-temperature hardness).
If the content is less than 0.1%, the desired effect cannot be obtained, while if the content exceeds 2.0%, the high-temperature corrosion resistance and high-temperature oxidation resistance tend to deteriorate. , its content was determined to be 0.1 to 2.0 chi.

In addition, the Mn component also has a desulfurization action in addition to the parental action as described above, so when it is used as a deoxidizing and desulfurizing agent, it becomes an unavoidable impurity in the same way as the Si component.
Although it may be contained in a range of less than 1%, in this case as well, the components may be adjusted so that the total content, including the content of unavoidable impurities, is 0.1% or more.

(dl Cr A part of the Cr component dissolves in solid solution in the base material, improving high-temperature corrosion resistance and high-temperature oxidation resistance, especially in a combustion atmosphere, and the remaining part forms carbide to improve hardness. This has the effect of improving high-temperature wear resistance, but if the content is less than 25 inches, the desired effect cannot be obtained,
On the other hand, if the content exceeds 35%, the toughness decreases, so the content was set at 25 to 35%.

(e) Fe When contained in a predetermined amount, the Fe component exhibits the same effect as Co, so it is included as a partial substitute for the expensive Co component for the purpose of cost reduction. If it is less than 1%, the economic effect will not be sufficient, while if it is 30%
If the content exceeds 100%, the high-temperature compression resistance (high-temperature strength) will decrease, so the content was set at 1 to 30%.

(fl Hf' The Hf component mainly dissolves in the austenite base formed of Co and Cr components to improve high temperature strength (high temperature compression resistance) and high temperature oxidation resistance, and also combines with C to form MC. It has the effect of forming type carbide and improving high temperature hardness and high temperature wear resistance, but its content is 0.001
If it is less than 0, the desired effect cannot be obtained;
Even if the content exceeds 45%, it is not foolish to achieve further improvement effects, and since the content yield decreases when dissolved in the atmosphere and is not economical, the content should be set at 0.001 to 0.001%.
It was set at 0.45 chi.

fgl MO and W These components have the effect of forming a solid solution in the base material, strengthening it, and forming carbides to further improve high temperature strength (high temperature compression resistance, high temperature hardness, and high temperature wear resistance). However, if the content is less than 0.1 inch each, the desired effect cannot be obtained; on the other hand, if the content exceeds 10 inch each, If Mo:O is contained, the toughness decreases, so the content is set to Mo:O, i to 10%, respectively.

w: It was set as 0.1-10%.

(hl Ti, Nb, and Ta) These components significantly suppress the growth of crystal grains in the substrate, rather make the crystal grains finer, and form MC type carbides and nitrides, thereby improving high-temperature strength (high-temperature compression). It has the effect of further improving the properties (resistance) and high-temperature hardness and high-temperature wear resistance), so it is included as necessary when these properties are required, but the content is less than 0.1 inch each. In this case, the desired effect of improving the above-mentioned action cannot be obtained, and on the other hand, if the content exceeds 3, the formation of carbides at high temperatures is promoted, and the toughness is reduced.
Since the formation of oxides in the combustion atmosphere becomes noticeable and the high-temperature corrosion resistance and high-temperature oxidation resistance deteriorate, the content is adjusted to 0.1 to 2% for Ti and 0.1 to 2% for Nb, respectively.
Ta: 0.1 to 2%, and Ta: 0.1 to 2%.

In addition, Zrf may be contained as an unavoidable impurity, but if the content exceeds 0.3%, toughness may deteriorate.

The Zr content should not exceed 0.3% so as not to adversely affect castability9 and weldability.

〔Example〕

Next, the Co-based heat-resistant alloy of the present invention will be specifically explained with reference to Examples.

The heat-resistant alloys 1 to 2 of the present invention were melted in the atmosphere using a conventional high-frequency melting furnace, each having the composition shown in Table 1, and then cast into a sand mold.
8 and various test pieces of conventional heat-resistant alloys were manufactured, respectively.
A high-temperature tensile test and a high-temperature compression creep test were conducted to evaluate high-temperature compression resistance, and a II+ vanadium attack test and oxidation resistance test were conducted to evaluate high-temperature corrosion resistance and high-temperature oxidation resistance in a combustion atmosphere. Vickers hardness at 900°C was measured for the purpose of evaluating wear resistance.

In addition, in the high temperature tensile test, the tensile strength at 800℃, 0
．． The 2-inch yield strength and elongation were measured.

The high-temperature compression creep test was conducted using a restrained welding thermal cycle reproducing device, and the compression deformation resistance at 1100° C. was determined by the stress value at the time when the amount of compression deformation was 0.05%/hf.

In addition, the vanadium attack resistance test is based on the JSPS Act.
Corrosion ash (85% V2O5 + 15% Na25o4
) was applied to the test piece at a rate of 20 mV/ctl,
The test was carried out in a vertical electric furnace heated to 800° C. and maintained under heating conditions for 20 hours, and the corrosion weight loss of the test bag was measured.

Furthermore, the oxidation resistance test was conducted under the condition that the test piece was heated continuously for 200 hours in a vertical electric furnace heated to 1200° C., and the oxidation loss after the test was measured. The results of these measurements are shown in Table 2.

〔Effect of the invention〕

From the results shown in Table 2, heat-resistant alloys 1 to 28 of the present invention all have excellent high-temperature strength (high-temperature compression resistance) and high-temperature It is clear that this material has excellent high-temperature corrosion resistance and high-temperature oxidation resistance.

As mentioned above, the CO-based heat-resistant alloy of the present invention has excellent high-temperature compression resistance, high-temperature corrosion resistance, high-temperature anti-oxidation property, and high-temperature wear resistance, and is particularly resistant to high-temperature corrosivity and extremely strong oxidation. It exhibits excellent high-temperature corrosion resistance against metals, so it is particularly useful for structural members such as heating furnaces and soaking furnaces for steelmaking that use heavy oil or blast furnace gas as fuel, as well as heat treatment furnaces, such as skid hardware and other furnaces. It has industrially useful properties such as a significantly long service life when used as flooring materials.

Applicant: Mitsubishi Metals Corporation Agent Tomi 1) Kazuo and 1 other person

Claims (4)

[Claims] (1) C: More than 0.2 inches to 0.7 inches. Si: 0.1 to 3 inches. 0.1 to 2 chi to IvIr. Cr: 25-35%. Fe: 1-30chi. Hf: 0.001-0.45%. 1. A Co-based heat-resistant alloy exhibiting excellent high-temperature properties in a high-temperature combustion atmosphere, characterized by having a composition c or higher type 1ts) with the remainder consisting of Co and unavoidable impurities. (2) C: More than 0.2 inches to 0.7 inches. St: o, 1-3 chi. Mn: 0.1 to 2 inches. Cr: 25-351 Fe: 1-30 Chi. Hf: 0.0 0 1 to 0.45 h. Contains Sara K. One or two of Mo: 0.1 to 10 inches and W: 0.1 to 10 inches. A CO-based heat-resistant alloy exhibiting excellent high-temperature properties in a substance-temperature combustion atmosphere, characterized by having a composition containing CO and inevitable impurities. (3) C: More than 0.2 inches to 0.7 inches. st: o, 1-3 chi. Mn: 0.1 to 2 inches. Cr: 25-35%. Fe: 1-30chi. Hf:O, OO1-0.45qb. Further, Ti: 0.1 to 2 Ti. Nb: 0.1-2ch. Ta: 0.1 to 2 inches. A CO-based heat-resistant alloy exhibiting excellent high-temperature properties in a high-temperature combustion atmosphere, characterized in that it contains one or more of the above, with the remainder consisting of CO and unavoidable impurities. (4) C: More than 0.2 inches to 0.7%. Si: Q, 1-3%. Mn: O11-2ch. Cr: 25-35%. Fe: 1-30 section. Hf: 0. OO1~045chi. Further, Mo: 0.1 to 10% and one or two of w:o, i to 10 Ti, and Ti: 0.1 to 2%. Nb: 0.1-2%. Ta: 0.1 to 2 inches. Containing one or more of the following, the remaining crab Co
A CO-based heat-resistant alloy exhibiting excellent high-temperature properties in a high-temperature combustion atmosphere, characterized by having a composition consisting of unavoidable impurities.