JPS6254388B2 - - Google Patents

Description

[Detailed description of the invention]

This invention has excellent high-temperature compression resistance, high-temperature oxidation resistance, high-temperature corrosion resistance, and high-temperature wear resistance (hereinafter collectively referred to as high-temperature properties),
Particularly related to Co-based heat-resistant alloys suitable for use in manufacturing structural members in high-temperature combustion furnaces such as heating furnaces, soaking furnaces, or heat treatment furnaces that use fuel such as heavy oil or blast furnace gas, which require these properties. It is. Generally, heavy oil, blast furnace gas, etc. are used as fuel in heating furnaces, soaking furnaces, heat treatment furnaces, etc. for iron manufacturing, and for this reason, skid metal fittings, which are the structural members of these furnaces, and other furnaces are used as fuel. Floor materials must be exposed to a high-temperature combustion atmosphere of 1,200 to 1,350°C and containing highly corrosive and oxidizing vanadium oxides (V oxides) and sulfur oxides (S oxides). Moreover, the conditions under which these furnaces are used are becoming increasingly severe. Under such circumstances, currently Fe-30% Cr-22% is mainly used to manufacture the structural members of these furnaces.
Fe-based heat-resistant alloy with Ni composition, Co-28%Cr
A Co-based heat-resistant alloy with a composition of −20% Fe has been used, but 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 Although these alloys exhibit better high-temperature properties than the Fe-based heat-resistant alloys, they do not have sufficient high-temperature compression resistance in the above-mentioned high-temperature combustion atmosphere of 1,300 to 1,350 degrees Celsius. Currently, the scope of use is limited. Therefore, from the above-mentioned viewpoint, the present inventors conducted research to develop a material with excellent high-temperature properties, and as a result, the results were as follows: C: 0.005-0.2%, Si: 0.1-2%, Contains Mn: 0.1-2%, Cr: 25-35%, Ni: 10-30%, Fe: 1-25%, Mo: 0.1-10%, Hf: 0.001-0.45%, and further contains as necessary. Contains one or more of the following: Ti: 0.1-2%, Nb: 0.1-2%, Ta: 0.1-2%, W: 0.1-10%, and the rest is
Co-based alloys, which have a composition consisting of Co and unavoidable impurities, are exposed to high-temperature combustion furnaces and structural members such as heating furnaces, soaking furnaces, or heat treatment furnaces that use heavy oil or blast furnace gas as fuel. ℃
It has excellent high-temperature properties, namely high-temperature compression resistance, high-temperature oxidation resistance, high-temperature corrosion resistance, and They found that it exhibits high-temperature wear resistance. This invention was made based on the above knowledge, and the reason why the component composition range was limited as described above will be explained below. (a) C The C component includes Cr, which is a solid solution in the base material to improve strength (compression resistance) and is an alloying component.
Mo, Hf, and further combine with W, Ti, Nb, Ta, etc. to form carbides such as M ₇ C ₃ , MC, and M ₂₃ C ₆ types to improve hardness (wear resistance) and improve welding. However, if the content is less than 0.005%, the desired effect cannot be obtained, while if the content exceeds 0.2%, the precipitation of carbides will increase. The content is reduced to 0.005%, and its particle size becomes coarser, reducing toughness and lowering the melting point of the substrate, causing a decrease in heat resistance.
It was set at ~0.2%. (b) Si Along with Cr, the Si component has the effect of improving high-temperature corrosion resistance and high-temperature oxidation resistance in a high-temperature combustion atmosphere, as well as deoxidizing effect and the effect of improving the fluidity of molten metal to improve castability. Cr has the effect of improving high-temperature compression resistance (high-temperature strength), but if the content is less than 0.1%, the desired effect cannot be obtained, while if the content exceeds 2%, Cr As toughness and weldability decrease in relation to
Its content was set at 0.1-2%. As mentioned above, the Si component has a deoxidizing effect, so when it is used as a deoxidizing agent, it may be contained as an unavoidable impurity in a range of less than 0.1%. 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, Mn component has a deoxidizing effect, and also has thermal shock resistance and high-temperature wear resistance (high-temperature hardness).
It has the effect of improving the
If it is less than %, the desired effect cannot be obtained in the above action,
On the other hand, if the content exceeds 2.0%, the high-temperature corrosion resistance and high-temperature oxidation resistance tend to deteriorate, so the content was set at 0.1 to 2.0%. In addition, the Mn component also has a desulfurization effect in addition to the deoxidizing effect as mentioned above, so when it is used as a deoxidizing and desulfurizing agent, it is used as an unavoidable impurity in the range of less than 0.1%. However, in this case as well, the ingredients should be adjusted so that the total content, including the content of unavoidable impurities, is 0.1% or more. (d) Cr A part of the Cr component forms a 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 carbides to improve hardness. , which has the effect of improving high-temperature wear resistance, but its content is 25%.
If the content is less than 35%, the desired effect cannot be obtained, while if the content exceeds 35%, the toughness will decrease, so the content was set at 25 to 35%. (e) Ni In addition to stabilizing the austenitic structure and increasing its toughness, Ni has the effect of improving high-temperature corrosion resistance and high-temperature oxidation resistance in a combustion atmosphere together with Cr, but if its content is less than 10%, The content was set at 10 to 30% because the desired effect could not be obtained in the above-mentioned action, and on the other hand, even if the content exceeded 30%, no further improvement effect would appear. (f) Fe When Fe component is contained in a specified amount, it 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 the content is less than 1%, the economic effect will not be sufficient, while if the content exceeds 25%, the high temperature compression resistance (high temperature strength) will decrease.
%. (g) Mo The Mo component has the effect of forming a solid solution in the base material, strengthening it, and forming carbides to improve high-temperature strength (high-temperature compression resistance) and high-temperature hardness (high-temperature abrasion resistance). However, if the content is less than 0.1%, the desired effect cannot be obtained;
If the content exceeds 10%, the toughness decreases, so the content was set at 0.1 to 10%. (h) Hf The Hf component improves high-temperature strength (high-temperature compression resistance) and high-temperature oxidation resistance by solidly dissolving in the austenite matrix, which is mainly composed of Co, Cr, and Ni components, and also combines with C. to form MC-type carbide, which has the effect of improving high-temperature hardness (high-temperature wear resistance), but its content is 0.001%.
If the content is less than 0.45%, the desired effect cannot be obtained; on the other hand, if the content exceeds 0.45%, not only will no further improvement effect be obtained, but the content yield will decrease upon dissolution in the atmosphere, making it uneconomical. , its content was determined to be 0.001-0.45%. (i) W The W component coexists with Mo to form a solid solution in the base material and further strengthen it, and also forms carbides to further improve high temperature strength (high temperature compression resistance) and high temperature hardness (high temperature wear resistance). However, if the content is less than 0.1, the desired effect of improving the above-mentioned properties cannot be obtained; If the content exceeds %, the toughness will decrease, so the content should be
It was set at 0.1-10%. (j) Ti, Nb, and Ta These components significantly suppress the growth of crystal grains in the base material, or rather make the crystal grains finer and
It forms MC-type carbides and nitrides to further improve high-temperature strength (high-temperature compression resistance) and high-temperature hardness (high-temperature wear resistance), so it is necessary when these properties are required. However, the content varies depending on the
If the content is less than 0.1%, the desired effect of improving the above action cannot be obtained, while if the content exceeds 2%, not only will the formation of carbides at high temperatures be promoted and the toughness will decrease, but also the toughness will decrease in the combustion atmosphere. Since the formation of Ti oxides becomes noticeable and the high-temperature corrosion resistance and high-temperature oxidation resistance deteriorate, the content is reduced to Ti: 0.1 to 2.
%, Nb: 0.1-2%, and Ta: 0.1-2%. In addition, Zr may be contained as an unavoidable impurity, but if the content exceeds 0.3%,
The content of Zr should not exceed 0.3%, as it will have a negative effect on toughness, castability, and weldability. Next, the Co-based heat-resistant alloy of the present invention will be specifically explained with reference to Examples. Example By melting molten metals having the compositions shown in Table 1 in the atmosphere using an ordinary high-frequency melting furnace, and then casting them into sand molds,
Various test pieces of heat-resistant alloys 1 to 28 of the present invention, comparative heat-resistant alloys, and conventional heat-resistant alloys 1 and 2 were manufactured, and subjected to high-temperature tensile tests and high-temperature compression creep tests for the purpose of evaluating high-temperature compression resistance. Panadium attack resistance test and oxidation resistance test were conducted to evaluate high-temperature corrosion resistance and high-temperature oxidation resistance in the atmosphere, and further to evaluate high-temperature wear resistance.
The Vickers hardness at 1000°C was measured. In addition, in the high temperature tensile test, the tensile temperature at 1000℃ was

【table】

【table】

【table】

[Table] Strength, 0.2% proof stress, and elongation were measured. The high-temperature compression creep test was conducted using a restrained welding thermal cycle reproduction device, and the compressive deformation resistance at 1200°C was determined by the stress value at the time when the amount of compressive deformation was 0.05% hr. In addition, for the vanadium attack resistance test, corrosive ash (85% V ₂ O ₅ + 15% Na ₂ SO ₄ ) was applied to the test piece at a rate of 20 mg/cm ² and heated to 800°C, based on the Jakushin Law. The test was carried out in a vertical electric furnace under conditions of heating and holding for 20 hours, and the corrosion loss after the test was measured. Furthermore, the oxidation resistance test was conducted under the condition that the test piece was continuously heated for 200 hours in a vertical electric furnace heated to 1300°C, and the oxidation loss after the test was measured. The results of these measurements are shown in Table 2. From the results shown in Table 2, the heat-resistant alloy 1 of the present invention
-28 have superior high-temperature strength (high-temperature compression resistance) and high-temperature hardness compared to conventional heat-resistant alloys 1 and 2, which have compositions corresponding to the conventional Fe-based heat-resistant alloys and conventional Co-based heat-resistant alloys. It is clear that the material has excellent properties such as high-temperature wear resistance, high-temperature corrosion resistance, and high-temperature oxidation resistance. On the other hand, as seen in Comparative Heat Resistant Alloys 1 to 10, the content of any of the constituent components (marked with * in Table 1)
It can be seen that when deviates from the scope of the present invention, at least one of the above characteristics becomes inferior. As mentioned above, the Co-based heat-resistant alloy of the present invention is
It has excellent high-temperature compression resistance, high-temperature corrosion resistance, high-temperature oxidation resistance, and high-temperature abrasion resistance, and it exhibits excellent high-temperature corrosion resistance, especially against highly corrosive and oxidizing oxides at high temperatures. It has an industrial advantage, as it has an extremely long service life when used as a structural member of steelmaking heating furnaces that use heavy oil or blast furnace gas as fuel, as well as heat treatment furnaces, such as skid metal fittings and other hearth parts. It has useful properties.

Claims (1)

[Claims] 1 C: 0.005-0.2%, Si: 0.1-2%, Mn: 0.1-2%, Cr: 25-35%, Ni: 10-30%, Fe: 1-25%, Mo A Co-based heat-resistant alloy for structural members of high-temperature combustion furnaces, characterized in that it contains: 0.1 to 10% Hf, 0.001 to 0.45% Hf, and the remainder consists of Co and inevitable impurities (weight %). 2 C: 0.005-0.2%, Si: 0.1-2%, Mn: 0.1-2%, Cr: 25-35%, Ni: 10-30%, Fe: 1-25%, Mo: 0.1-10%, A structure of a high-temperature combustion furnace characterized by containing Hf: 0.001 to 0.45%, and further containing W: 0.1 to 10%, with the remainder consisting of Co and non-wall impurities (weight %). Co-based heat-resistant alloy for parts. 3 C: 0.005-0.2%, Si: 0.1-2%, Mn: 0.1-2%, Cr: 25-35%, Ni: 10-30%, Fe: 1-25%, Mo: 0.1-10%, Contains Hf: 0.001-0.45%, and further contains one or more of the following: Ti: 0.1-2%, Nb: 0.1-2%, Ta: 0.1-2%, and the rest is
Composition consisting of Co and non-wall impurities (more than % by weight)
A Co-based heat-resistant alloy for structural members of high-temperature combustion furnaces, characterized by having: 4 C: 0.005-0.2%, Si: 0.1-2%, Mn: 0.1-2%, Cr: 25-35%, Ni: 10-30%, Fe: 1-25%, Mo: 0.1-10%, Contains Hf: 0.001-0.45%, Ti: 0.1-2%, Nb: 0.1-2%, Ta: 0.1-2
%, and W: 0.1 to 10%, with the remainder consisting of Co and unavoidable impurities (weight %). Co-based heat-resistant alloy for parts.