JP2024020264A - Cr-Ni BASED ALLOY, PRODUCTION METHOD FOR Cr-Ni BASED ALLOY AND RAPIDLY SOLIDIFIED MOLDED BODY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Cr-Ni based alloy which is a metal material suitable for use in harsh environments such as oil wells, has both high erosion resistance and wear resistance that are equal to or more excellent than a conventional one and is low in cost, and to provide a rapidly solidified molded body made of the Cr-Ni based alloy, an alloy powder, a powder metallurgy molded body, a cast molded body, a production method for the Cr-Ni based alloy, and a mechanical facility and piping members using the Cr-Ni based alloy.

SOLUTION: A Cr-Ni based alloy according to the present invention comprises, by mass%: more than 40.0% and 65.0% or less of Cr; 0% or more and 35.0% or less of Fe; 0% or more and less than 2.0% of Mn; and any of (1) to (3) described below, with the remainder being Ni and unavoidable impurities, where the Ni is 15% or more. (1) more than 1.1% and 4.0% or less of C, (2) 0.7% or more and 3.0% or less of B, and (3) 0.5% or more and 2.5% or less of C and more than 0% and 20% or less of Nb.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present disclosure relates to technology for highly corrosion-resistant and high-strength alloys, particularly Cr-Ni alloys, rapidly solidified compacts made of Cr-Ni alloys, alloy powders, powder metallurgy compacts, cast compacts, and Cr-Ni alloys. This invention relates to a method for producing an alloy, and mechanical equipment and piping members using a Cr--Ni alloy.

In equipment used for mining crude oil, natural gas, etc. and transporting fluids, we improve the surface of parts that come into contact with other materials or that slide by overlaying and welding materials with excellent corrosion resistance and wear resistance. Measures may be taken to provide layers to reduce wear and tear on equipment components. Examples of such surface modification materials include cobalt (Co)-based alloys such as STELLITE (STELLITE is a registered trademark) and TRIBALOY (TRIBALOY is a registered trademark), and nickel (Ni)-based alloys such as COLMONOY (COLMONOY is a registered trademark). Alloys are commercially available and widely used. However, Co and Ni, which are the main raw materials for these, are expensive and there is a problem in that the material cost increases.

To deal with this, various Cr-based alloys containing relatively inexpensive chromium (Cr) as a main component have been proposed. Discloses a method for producing a Cr-Ni alloy having a chemical composition of ~6% by mass and the balance being 7.9% by mass or more and subcomponents, and is used to form a coating with corrosion resistance and wear resistance. It is said that it is possible. Furthermore, Japanese Patent Application Laid-open No. 11-285890 discloses a welding rod in which alloy powder containing high concentrations of Cr and C is encapsulated with a sheath material made of a Cr-Ni containing alloy. It is said that rods can be manufactured efficiently. Further, JP-A-11-293377 discloses a heating furnace hearth member containing Cr: 50 to 80% by mass, at least one of Ti, Mn, Mo, and Zr: 2 to 10% by mass, and the balance Ni and subcomponents. Cr-based alloys have been disclosed, and it is said that alloys with excellent creep resistance and oxidation resistance can be provided with good productivity.

Japanese Patent Application Publication No. 10-110206 Japanese Patent Application Publication No. 11-285890 Japanese Patent Application Publication No. 11-293377 International publication 2017/037851 pamphlet International publication 2009/064415 pamphlet Japanese Patent Application Publication No. 2005-314721

The alloy produced by the method described in JP-A-10-110206 has an extremely high Cr content, and the melting point of the alloy is thought to be a high temperature exceeding 1500°C. This leads to an increase in the energy required to manufacture the alloy, resulting in high manufacturing costs. In addition, the welding rod described in JP-A-11-285890 requires alloy powder to be encapsulated in a sheath material, which requires higher manufacturing costs than when the alloy itself is made into a wire rod or powder. Become. Further, in the Cr-based alloy described in JP-A-11-293377, it is stated that it is desirable to add Ti, Mn, etc. in an amount of 2% by mass or more in order to improve compressive strength and creep resistance. However, in the Cr-based alloy described in the International Publication No. 2017/037851 pamphlet studied by the inventors, for example, when Mn exceeds 2% by mass, coarse particles of sulfide (e.g. MnS) are formed, resulting in poor corrosion resistance. This is thought to be a factor in the deterioration of mechanical properties.
For example, in the field of oil well drilling, the environment to which equipment is exposed has become increasingly harsh in recent years due to deeper drilling, and metal materials with high corrosion resistance, mechanical properties, and low cost are becoming more powerful. It has been demanded.

One aspect of the present disclosure is a low-cost Cr-Ni metal material that can be suitably used even in harsh environments such as oil wells, has high corrosion resistance and wear resistance that are equal to or higher than conventional ones, and is low-cost. The objective is to provide alloys.
Other aspects of the present disclosure provide a rapidly solidified compact, an alloy powder, a powder metallurgy compact, a cast compact, a method for producing a Cr-Ni alloy, and a method using the Cr-Ni alloy. Our goal is to provide mechanical equipment and piping components.

Specific means for solving the above problems include the following aspects.
<1> In mass%,
Cr of more than 40.0% and 65.0% or less,
Fe of 0% or more and 35.0% or less,
Mn of 0% or more and less than 2.0%,
Including any of the following (1) to (3),
(1) More than 1.1% and less than 4.0% C
(2) B of 0.7% or more and 3.0% or less
(3) C from 0.5% to 2.5% and Nb from more than 0% to 20%
A Cr--Ni alloy in which the balance is Ni and unavoidable impurities, and the Ni is 15% or more.

<2> In mass%,
Cr of more than 46.0% and 65.0% or less,
Fe of 0.1% or more and 30.0% or less,
More than 0% and less than 2.0% Mn;
Containing more than 1.1% and less than 4.0% C,
The Cr--Ni alloy according to <1>, wherein the remainder consists of Ni and inevitable impurities.
<3> In mass%,
Cr of 45.0% or more and 65.0% or less,
Fe of 0.1% or more and 35.0% or less,
More than 0% and less than 2.0% Mn;
0.7% or more and 3.0% or less of B,
The Cr--Ni alloy according to <1>, wherein the remainder consists of Ni and inevitable impurities.
<4> Cr of more than 40.0% and 65.0% or less,
Fe of 0% or more and 30.0% or less,
Contains 0.5% or more and 2.5% or less C and more than 0% and 20% or less Nb,
The Cr--Ni alloy according to <1>, wherein the remainder consists of Ni and inevitable impurities.
<5> In mass%,
Si of 0.1% or more and 1.0% or less,
Al of 0.005% or more and 0.05% or less,
Sn of 0.02% or more and 0.3% or less,
Cu of 0.1% or more and 5.0% or less,
The Cr--Ni alloy according to any one of <1> to <4>, containing at least one or more of the following.
<6> The Cr-Ni alloy according to any one of <1> to <5>, wherein the Cr-Ni alloy has a ferrite phase and/or an austenite phase formed therein.

<7> A rapidly solidified molded body made of the Cr-Ni alloy according to any one of <1> to <6>.
<8> An alloy powder made of the Cr-Ni alloy according to any one of <1> to <6>.
<9> A powder metallurgy compact made of the Cr-Ni alloy according to any one of <1> to <6>.
<10> A cast molded body made of the Cr-Ni alloy according to any one of <1> to <6>.

<11> A method for producing a Cr-Ni alloy according to any one of <1> to <6>,
a melting step of melting the raw material of the Cr-Ni alloy to form a molten metal;
A method for producing a Cr--Ni alloy, comprising: an atomizing step of producing an alloy powder from the molten metal.
<12> A method for producing a Cr-Ni alloy according to any one of <1> to <6>,
a melting step of melting the raw material of the Cr-Ni alloy to form a molten metal;
a casting step of casting the molten metal to form a cast molded body;
A method for producing a Cr--Ni alloy, comprising the step of mechanically pulverizing the cast compact to produce an alloy powder.

<13> A method for producing a Cr-Ni alloy according to any one of <1> to <6>, comprising:
A powder compacting step of forming a powder compact by press molding or injection molding using powder made from the Cr-Ni alloy as a raw material, and sintering the powder compact at a temperature below the solidus temperature of the alloy. A method for producing a Cr--Ni alloy, comprising: a sintering step of performing heat treatment to form a powder metallurgy compact.
<14> A method for producing a Cr-Ni alloy according to any one of <1> to <6>,
a melting step of melting the raw material of the Cr-Ni alloy to form a molten metal;
A method for producing a Cr--Ni alloy, comprising a casting step of casting the molten metal to form a cast molded body.

<15> Mechanical equipment for transporting or processing objects containing solids and/or corrosive components, the member itself constituting the mechanical equipment and with which the object comes into contact, or the object of the member to be transported. Mechanical equipment, at least a part of which is in contact with the Cr--Ni alloy according to any one of <1> to <6>.
<16> A piping member used for a conveyance route of an object to be transported containing solid matter and/or a corrosive component, wherein the piping member itself or at least a part of the surface of the piping member that comes into contact with the object to be transported is < A piping member made of a Cr-Ni alloy according to any one of items 1> to <6>.

According to one aspect of the present disclosure, the metal material is a metal material that has both corrosion resistance and wear resistance that can withstand severe corrosive environments such as direct contact with fuels of various qualities and deteriorated lubricating oil, and is made of a Ni-based alloy. A Cr--Ni alloy is provided as a material that can be manufactured at a lower cost than a Co-based alloy.
According to another aspect of the present disclosure, a rapidly solidified compact, an alloy powder, a powder metallurgy compact, a cast compact made of the Cr-Ni alloy according to one embodiment of the present disclosure, and a Cr-Ni alloy using the Cr-Ni alloy. Mechanical equipment and piping members can have high corrosion resistance and wear resistance equivalent to or higher than conventional materials.

1 is an example of a method for manufacturing a Cr—Ni alloy according to the present disclosure, and is a process diagram showing a method for manufacturing an alloy powder and a rapidly solidified compact. FIG. 7 is another example of the method for manufacturing a Cr—Ni-based alloy according to the present disclosure, and is a process diagram showing a method for manufacturing a powder metallurgy compact. FIG. 7 is another example of a method for manufacturing a Cr—Ni alloy product according to the present disclosure, and is a process diagram showing a method for manufacturing a cast molded body. FIG. 2 is a diagram showing a schematic cross-sectional view of a screw pump, an injection mold, and a crusher, which are application examples of the Cr—Ni alloy according to the present disclosure. FIG. 3 is a diagram showing the relationship between the corrosion rate obtained by a boiling sulfuric acid test and the wear volume obtained by a soil abrasion test in the Cr—Ni alloy according to Example 1. FIG. 2 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr—Ni-based alloy of Comparative Examples (Nos. 1 and 2) of Example 1. FIG. 3 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr—Ni-based alloy of Comparative Examples (Nos. 3 and 4) of Example 1. FIG. 3 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr--Ni alloy according to the present invention examples (Nos. 5 and 6) of Example 1. FIG. 2 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr--Ni alloy according to the present invention examples (Nos. 7 and 8) of Example 1. FIG. 2 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr--Ni alloy according to the present invention examples (Nos. 9, 10, 11) of Example 1. FIG. 2 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr--Ni alloy according to the present invention examples (Nos. 12, 13, and 14) of Example 1. FIG. 3 is a diagram showing the relationship between the corrosion rate obtained by a boiling sulfuric acid test and the wear volume obtained by a soil abrasion test in a Cr—Ni alloy according to Example 2. FIG. 2 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr--Ni--Fe based alloy according to the present invention examples (Nos. 21 and 22) of Example 2. FIG. 3 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr--Ni--Fe based alloy according to the present invention examples (Nos. 23 and 24) of Example 2. FIG. 3 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr--Ni--Fe based alloy according to the present invention examples (Nos. 25 and 26) of Example 2. FIG. 3 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr--Ni--Fe based alloy of a comparative example (No. 27) of Example 2. FIG. 3 is a diagram showing an electron microscope observation image of a cross-sectional polished surface of a cast molded body of a Cr--Ni--Fe based alloy according to the present invention example (No. 28) of Example 2. FIG. 3 is a diagram showing the relationship between the corrosion rate obtained by a boiling sulfuric acid test and the wear volume obtained by a soil abrasion test in a Cr—Ni alloy according to Example 3. FIG. 3 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr--Ni alloy according to the present invention examples (Nos. 31, 32, and 33) of Example 3. FIG. 3 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr--Ni alloy according to the present invention examples (Nos. 34 and 35) of Example 3. FIG. 3 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr--Ni alloy according to the present invention examples (Nos. 36 and 37) of Example 3. FIG. 3 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr--Ni alloy according to the present invention examples (Nos. 38 and 39) of Example 3. FIG. 3 is a diagram showing an image observed by an electron microscope of a cross-sectional polished surface of a cast molded body of a Cr--Ni alloy according to the present invention (Nos. 40 and 41) of Example 3. FIG. 2 is a diagram showing the relationship between the corrosion rate obtained by a boiling sulfuric acid test and the wear volume obtained by a soil abrasion test in a build-up material that is a comparison target with a Cr-Ni-Fe-based alloy according to the present disclosure. .

In this specification, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as lower and upper limits. In the numerical ranges described stepwise in the present disclosure, the upper limit or lower limit described in one numerical range may be replaced with the upper limit or lower limit of another numerical range described stepwise. Furthermore, in the numerical ranges described in this disclosure, the upper limit or lower limit of the numerical range may be replaced with the values shown in the Examples.
In this specification, the term "process" is used not only to refer to an independent process but also to include any process that achieves its intended purpose even if it cannot be clearly distinguished from other processes. .

The present inventors investigated and studied the relationship among chemical composition, metallographic morphology, corrosion resistance, and earth and sand abrasion resistance in Cr--Ni alloys, and completed the present invention.
Embodiments of the present invention will be specifically described below with reference to the drawings. However, states and processes having the same meaning will be given the same reference numerals and redundant explanations will be omitted. Furthermore, the present invention is not limited to the embodiments mentioned here, and can be appropriately combined with known techniques or improved based on known techniques without departing from the technical idea of the invention. It is.

[Chemical composition]
The Cr-Ni alloy of the present disclosure has a mass percentage of
Cr of more than 40.0% and 65.0% or less,
Fe of 0% or more and 35.0% or less,
Mn of 0% or more and less than 2.0%,
Including any of the following (1) to (3),
(1) More than 1.1% and less than 4.0% C
(2) B of 0.7% or more and 3.0% or less
(3) C from 0.5% to 2.5% and Nb from more than 0% to 20%
The balance is a Cr--Ni alloy consisting of Ni and unavoidable impurities, and the Ni is 15% or more.
The Cr-Ni alloy of the present disclosure suppresses the amount of Cr and forms at least one type of compound of Cr-based carbide, Cr-based boride, and Nb-based carbide in the matrix, so that it can be used in harsh environments such as oil wells. It is a low-cost Cr--Ni alloy that has both high corrosion resistance and wear resistance and can be suitably used in the industry.

The composition (each component) of the Cr--Ni alloy according to the present disclosure will be explained below. The content of each element is expressed in mass % unless otherwise specified. The Cr-Ni alloy according to the present disclosure preferably has a total content of the disclosed components of more than 99% by mass, and is free from components other than the disclosed components, such as impurities mixed in during the manufacturing process of the alloy. The total content is preferably less than 1% by mass.

Cr: More than 40.0% and 65.0% or less Cr is one of the main components of the Cr--Ni alloy of the present disclosure, and is an important component for obtaining good corrosion resistance. It is preferable that the Cr content is more than 40.0%, and the Cr component has the maximum content from the viewpoint of corrosion resistance and material cost. This is because the alloy of the present disclosure has Cr, which is cheaper than Ni, as the largest component, and has the advantage that the material cost can be lower than, for example, a Ni-based alloy that has expensive Ni as the largest component. Moreover, by making Cr the largest component, an oxide film is easily formed and a passive state is formed, so that corrosion resistance is improved. When the Cr content is 40.0% or less, the amount of carbides appearing in the alloy structure decreases, and wear resistance may become insufficient. Alternatively, the corrosion resistance may deteriorate due to a decrease in Cr in the alloy structure. On the other hand, if the Cr content exceeds 65.0%, the melting point of the alloy will increase, and the energy required for producing ingots by melting and powdering by atomization will increase, resulting in poor manufacturability and increased manufacturing costs. The Cr content shall be 65.0% or less.

Further, Cr, together with C, which will be described later, is a component that also contributes to the formation of carbides that are involved in improving wear resistance. That is, when the above-mentioned "(1) more than 1.1% and 4.0% of C" is included, Cr constitutes a Cr-based carbide together with C. In this form, in order to more reliably exhibit the effects of Cr, the content of Cr is preferably more than 46.0%, more preferably 50.0% or more, and more preferably 55.0% or more. is more preferable.

Further, Cr, together with B, which will be described later, is a component that also contributes to the formation of borides, which are involved in improving wear resistance. That is, when the above-mentioned "(2) B of 0.7% or more and 3.0% or less" is included, Cr and B constitute Cr boride. In this form, in order to more reliably exhibit the effects of Cr, it is preferable that Cr be at least 45.0%, more preferably at least 50.0%, even more preferably at least 55.0%.

In addition, Cr, along with C, is a component that also contributes to the formation of carbides related to improvement of wear resistance, but as mentioned above, "(3) 0.5% to 2.5% C and more than 0% C" When containing 20% or less of Nb, Cr constitutes a Cr-based carbide together with C. In order to more reliably exhibit the effects of Cr, the content of Cr is more than 40.0%, preferably 43.0% or more. More preferably, it is 50.0% or more, more preferably 55.0% or more.

Fe: 0% or more and 35.0% or less Fe contributes to the formation of carbides together with Cr and the like. By dissolving Fe in the carbide, the amount of Cr in the carbide is reduced, and a decrease in the Cr concentration in the parent phase around the carbide is suppressed. Further, since a decrease in the Cr concentration in the matrix leads to a decrease in corrosion resistance, the corrosion resistance is improved by adding Fe. On the other hand, if there is too much Fe, ferrite will crystallize as a primary crystal, and the corrosion potential difference in the matrix will increase, making local corrosion more likely to occur. Therefore, the content of Fe contained in the alloy of the present disclosure is set to 35.0% or less.

Moreover, when Fe includes the above-mentioned "(1) C of more than 1.1% and 4.0% or less", it is preferable that Fe is 0.1% or more and 30.0% or less. Here, as described above, Fe contributes to the formation of carbides together with Cr and the like. By dissolving Fe in the carbide, the amount of Cr in the carbide is reduced, and a decrease in the Cr concentration in the parent phase around the carbide is suppressed. Further, since a decrease in the Cr concentration in the matrix leads to a decrease in corrosion resistance, the corrosion resistance is improved by adding Fe. On the other hand, if there is too much Fe, ferrite will crystallize as a primary crystal, and the corrosion potential difference in the matrix will increase, making local corrosion more likely to occur. Therefore, in the case of the above-mentioned form, the content of Fe is preferably 30.0% or less. It is more preferable to keep the content as low as 0.1% or more as long as it does not impair the performance of the material. Considering wear resistance, the upper limit of the Fe content is preferably 15% or less, more preferably 8% or less.

Further, when Fe contains the above-mentioned "(2) B of 0.7% or more and 3.0% or less", it becomes an essential component to ensure good mechanical properties, and 0.1% or more of 35. It is preferably 0% or less. When the Fe content is excessive, a brittle intermetallic compound σ phase tends to form in the temperature range of around 800° C., and the ductility and toughness of the Cr—Ni alloy decrease significantly (so-called σ phase embrittlement). Therefore, the content of Fe should be 35.0% or less, and it is more preferable to keep the content low within the range of 0.1% or more as long as the performance of the material is not impaired. Considering corrosion resistance, the content of Fe is preferably 20% or less, more preferably 15% or less.

In addition, when Fe contains the above-mentioned "(3) 0.5% to 2.5% C and 0% to 20% Nb", Fe is an element that improves corrosion resistance, and Fe addition As a result, the ferrite phase crystallizes and forms two phases with the austenite phase, forming a hard, tough, and high-strength parent phase. On the other hand, when the amount of Fe added is increased, a sigma phase, which is a brittle phase, is generated, which may impair mechanical properties. Therefore, in the case of this embodiment, the Fe content is preferably 30.0% or less. Further, although adding a large amount of Fe tends to increase strength, on the other hand, the amount of Cr decreases, which becomes a factor that deteriorates corrosion resistance or wear resistance. In order to obtain a certain level of wear resistance and corrosion resistance, the range is preferably 20% or less. More preferably it is 16% or less. Furthermore, when this alloy is used as a build-up material for inexpensive steel materials, Fe may be contained in an amount of 0% since Fe may be mixed in from the base steel material.

Mn: 0% or more and less than 2.0% Mn is a component that plays the role of desulfurization and deoxidation, especially in the process of mixing and dissolving raw materials, and contributes to improving mechanical properties and carbon dioxide corrosion resistance. . However, when adding a deoxidizing element in place of Mn, Mn may be left unadded (0%). When containing Mn, the Mn content is less than 2.0%. When the Mn content exceeds 2.0%, coarse particles of sulfide (for example, MnS) are formed, which causes a decrease in corrosion resistance and mechanical properties. In order to more reliably exhibit the effects of Mn, it is preferable to set the lower limit of Mn to 0.05%.
In addition, Mn is in the above-mentioned form containing "(1) more than 1.1% and less than 4.0% C" and "(2) more than 0.7% and not more than 3.0% B". In this case, it is preferably more than 0%.

In the form containing "(1) more than 1.1% and 4.0% or less of C" described above, C is more than 1.1% and 4.0% or less.
C has the effect of hardening the alloy by crystallizing or precipitating as a carbide or solidly dissolving in a matrix other than carbides. In the case of this form, in order to obtain the effect of improving wear resistance, it is preferable that the C content exceeds 1.1% to form massive Cr-based carbide containing Cr as a main component in the matrix. As the C content increases, the number of hard carbide particles increases, which tends to improve wear resistance, but Cr in the matrix is consumed, which becomes a factor that deteriorates corrosion resistance. Considering the balance between wear resistance and corrosion resistance, the C content is set to 4.0% or less. In order to more reliably exhibit the effects of C mentioned above, it is preferable to set the lower limit of C to 1.5% and the upper limit to 3.5%. Incidentally, the term "massive Cr-based carbide" refers to, for example, among the carbides shown in FIG. 8, those having a size such that a circle of 5 μm or more can be drawn in the carbide. In FIG. 8, the portions displayed in dark gray or black are carbides. Note that the composition of the carbide can be confirmed, for example, by quantitative analysis using an energy dispersive X-ray analyzer. The Cr-based carbide refers to the carbide that contains the most Cr in the quantitative analysis results.

In the above-mentioned form containing "(2) B of 0.7% or more and 3.0% or less", B is 0.7% or more and 3.0% or less.
B (boron) has the effect of crystallizing or precipitating hard boride, which is effective for wear resistance, in the matrix. In order to obtain the effect of improving wear resistance, it is preferable that the content of B is 0.7% or more to form a lumpy Cr-based boride containing Cr as a main component in the matrix. As the B content increases, the proportion of hard borides in the structure increases, and wear resistance tends to improve.To ensure the effects of B, B should be 1.0% or more. , more preferably 1.5% or more. On the other hand, when the B content becomes excessively large, Cr in the matrix is consumed as borides are produced, which causes deterioration of corrosion resistance. In addition, coarse borides crystallize and become a starting point for cracking during overlay construction. Furthermore, corrosion resistance also decreases due to the occurrence of corrosion caused by borides. Therefore, in consideration of the balance between wear resistance and corrosion resistance, it is preferable that B be at most 3.0%, more preferably at most 2.5%, even more preferably at most 2.0%. Note that the lumpy Cr-based boride is, for example, black and has an elongated shape as shown in FIG. 13, and has an elongated cross-sectional shape of 3 μm or more in the width direction and 30 μm or more in the longitudinal direction. Note that the composition of the boride can be confirmed, for example, by quantitative analysis using an energy dispersive X-ray analyzer (EDX). The Cr-based boride refers to a boride in which B was detected in the quantitative analysis results by EDX, and which contained the largest amount of Cr among the metal elements other than B.

In the above-mentioned form containing "(3) 0.5% or more and 2.5% or less C and 0% or more and 20% or less Nb", C is 0.5% or more and 2.5% or less, and Nb is , more than 0% and less than 20%.
Here, in the Cr—Ni-based alloy of the present disclosure, C has the effect of hardening the alloy by crystallizing or precipitating as a carbide or solidly dissolving in a matrix other than carbides. In order to obtain the effect of improving wear resistance, it is preferable to set the C content to 0.5% or more to form a massive Nb-based carbide containing Nb as a main component. Furthermore, as the C content increases, the number of hard Nb-based carbide particles increases, which tends to improve wear resistance, but if the C content increases beyond the above ratio, Cr in the matrix (base) is consumed. Although this increases hardness, it becomes a factor that deteriorates corrosion resistance. Considering the balance between wear resistance and corrosion resistance, the C content was set to 2.5% or less. In order to more reliably exhibit the effects of C mentioned above, the lower limit of C is preferably 0.8%, and the upper limit is preferably 1.5%.
Further, in the Cr-Ni alloy of the present disclosure, Nb has the effect of generating an austenite phase by crystallizing or precipitating as a Nb-based carbide, or by solid solution in a matrix other than carbides. . In order to obtain the effect of improving wear resistance, it is preferable to set the Nb content to more than 0% to form a massive Nb-based carbide containing Nb as a main component. In addition, as the Nb content increases, hard Nb-based carbide particles increase and wear resistance tends to improve; however, as the Nb content increases, it combines with Ni forming an austenite phase, improving toughness. , Nb is more expensive than Ni and may deteriorate cost performance. Furthermore, by increasing Nb, Cr, Ni, and Fe that form the matrix are decreased, which increases hardness and wear resistance, but becomes a factor that deteriorates mechanical properties and corrosion resistance. Considering the balance between wear resistance, corrosion resistance, and mechanical properties, the Nb content is set to 20% or less, but the preferable upper limit of Nb is 16%. Further, in order to exhibit wear resistance properties, it is preferable that the lower limit is 4%. Further, in order to more reliably exhibit the effects of the above-mentioned Nb-based carbide, the lower limit of Nb is more preferably set to 6.4%, and the upper limit is preferably set to 12%. Further, it is desirable that the ratio of Nb and C is approximately 8:1 (Nb:C in mass %). Note that the Nb-based carbide refers to, for example, polygonal massive carbide as seen in FIGS. 19 and 20, and an amorphous carbide that appears feather-like, dendritic, or linear. Note that the composition of the carbide can be confirmed, for example, by quantitative analysis using an energy dispersive X-ray analyzer. The Nb-based carbide refers to a carbide in which C was detected in the quantitative analysis results and Nb was contained in the largest amount among the metal elements other than C.

The remainder is Ni and unavoidable impurities:
Elements other than those described above are Ni and inevitable impurities. Among these, Ni is one of the main elements of the coating layer, and most of it is dissolved in solid solution in the matrix other than carbide, and hardly dissolved in carbide. The solid solution of Ni in the matrix has the effect of stabilizing the austenite phase constituting the matrix, suppressing the formation of ferrite in the primary crystal, and improving corrosion resistance. In order to fully exhibit this effect, it is preferable that the Ni content exceeds the above-mentioned Fe content. Further, the Ni content is preferably 15% or more, more preferably 25% or more, and still more preferably 30% or more. On the other hand, if the Ni content increases excessively, the above-mentioned effects of Cr may be impaired, so the upper limit of the Ni content is preferably less than the Cr content.
In addition to the above-mentioned Ni, the remainder also includes impurities that are unavoidable during manufacturing. Among these impurities, the following impurities should be particularly restricted.
Impurities such as P and S tend to segregate at grain boundaries and cause corrosion resistance, so P is limited to 0.02% or less and S to less than 0.005%. Regarding S, it is preferably 0.003% or less, more preferably 0.002% or less. In addition, O, N, etc. combine with Cr to form oxide-based and nitride-based inclusions, reducing cleanliness and deteriorating corrosion resistance and fatigue strength, so they should be kept as low as possible. is preferred. Therefore, O is preferably 0.002% or less, and N is preferably 0.04% or less. Further, although a small amount of Ta may be mixed into Nb as an impurity, Ta has little effect as long as it is within the range of 0.2%, and there is no need to limit it to a particularly low level, and it may be mixed.

Si: 0.1% or more and 1.0% or less Si is one of the optional components of the Cr-Ni alloy of the present disclosure, and is a component that plays the role of deoxidizing and contributes to improving mechanical properties. . When containing Si, the Si content is preferably 0.1% or more and 1.0% or less. If the Si content is less than 0.1%, the effects based on Si tend to be insufficient. Moreover, if Si exceeds 1%, coarse particles of oxide (for example, SiO2) are formed, which becomes a factor in deteriorating mechanical properties.
Al: 0.005% or more and 0.05% or less Al is also one of the optional components of the Cr-Ni alloy of the present disclosure, and is a component that contributes to improving the deoxidizing effect when combined with Mn and Si. . When containing Al, the content of Al is preferably 0.005% or more and 0.05% or less. When the Al content is less than 0.005%, the effects of Al may not be sufficiently obtained. Furthermore, when the Al content exceeds 0.05%, coarse particles of oxides and nitrides (eg, Al2O3 and AlN) are formed, which becomes a factor in deteriorating mechanical properties.

Sn: 0.02% or more and 0.3% or less Sn is an optional component that plays a role in strengthening the passive film in the Cr--Ni alloy of the present disclosure and contributes to improving corrosion resistance and wear resistance. Specifically, improved resistance to chloride ions and acidic corrosive environments can be expected. When containing Sn, the Sn content is preferably 0.02% or more and 0.3% or less. When the Sn content is less than 0.02%, the effects based on Sn cannot be sufficiently obtained. Furthermore, if the Sn content exceeds 0.3%, grain boundary segregation of the Sn component will occur, causing a decrease in the ductility and toughness of the alloy.
Cu: 0.1% or more and 5.0% or less Cu is an optional component that contributes to improving corrosion resistance in the Cr—Ni alloy of the present disclosure. When containing Cu, the content is preferably 0.1% or more and 5.0% or less. When the Cu content is less than 0.1%, the effects based on Cu cannot be sufficiently obtained. Moreover, when the Cu content exceeds 5.0%, Cu precipitates are likely to be formed, which becomes a factor in reducing the ductility and toughness of the alloy.

As described above, the alloy of the present disclosure described above is preferably formed into an alloy powder and used for forming a surface-modified layer by overlay welding. The molten alloy of the present disclosure may be introduced into a high-velocity stream of inert gas and pulverized by gas atomization, and the process may be performed using a PTA (Plasma transfer arc) overlay welding device. In a PTA overlay welding device, the powder is normally transported by flowing the pipe from the tip of the welding torch to the construction area, so the powder needs to move smoothly. On the other hand, powder obtained by gas atomization is preferable because it is spherical and has good fluidity. Further, a powdered alloy of the present disclosure can be sintered into a rod-shaped powder metallurgy molded body by a powder metallurgy method and used as a welding rod.

<Method for manufacturing Cr-Ni alloy>
Next, a method for manufacturing a Cr--Ni alloy according to the present disclosure will be described.
FIG. 1 is an example of a method for manufacturing a Cr-Ni alloy product according to the present disclosure, and shows steps for manufacturing an alloy powder (herein, powder and overlay welding material) made of a rapidly solidified cast compact. It is a diagram. As shown in FIG. 1, first, a melting step (step 1: S1) is performed to form a molten metal 10 by melting raw materials of a Cr--Ni alloy to a desired composition. There are no particular limitations on the method of melting the raw materials, and conventional methods for producing highly corrosion-resistant and high-strength alloys can be used. The molten metal 10 may be refined by a predetermined method to form a highly clean molten metal 12 with a reduced content of impurity components (FIG. 3).

Next, by performing an atomization step (step 2: S2) using the molten metal 10 or the cleaned molten metal 12 as a starting material, an alloy powder 20 of a Cr--Ni alloy can be obtained. An example of the atomization method is a method in which a high-pressure medium is sprayed against the flow of molten metal to crush the molten metal to obtain a powder, which is classified into gas atomization and water atomization depending on the type of medium used. Although there is no particular limitation on the atomization method in the present disclosure, for powder applications for overlay, it is preferable to use a gas atomization method that provides higher purity, homogeneous composition, and spherical particles. The obtained alloy powder 20 can be suitably used as, for example, a welding material, a powder metallurgy material, or an additive manufacturing material. Further, the target composition is preferably an alloy that contains carbides and whose parent phase is a two-phase alloy consisting of a ferrite phase and an austenite phase or a single-phase alloy of an austenite phase. In the case of a two-phase alloy, it is preferable that the austenite phase exhibits a volume fraction of 20% or more.
Next, the alloy powder 20 obtained by performing the atomization step S2 may be subjected to a classification step (step 3: S3) for adjusting the particle size to a desired size. Although the classification step S3 is not an essential step, when using the alloy powder 20 as a material for overlay, classification is carried out from the viewpoint of stable powder supply to the welding equipment and stabilization of the overlay construction process. It is preferable to do so. Although there is no particular limitation on the particle size to be classified, for example, a particle size range of 63 μm or more and 250 μm or less may be extracted and used for PTA overlay welding. In addition, when used for powder metallurgy molded bodies, which will be described later, from the viewpoint of dimensional accuracy of the molded body and prevention of remaining voids, the particles may be classified and sorted, for example, in the particle size range of 1 μm to 50 μm.

Next, when an overlay welding process (step 4: S4) is performed on the desired base material 41 using the alloy powder 20, the molten alloy powder 20 is rapidly cooled due to the temperature difference between the base material 41 and the outside air. It is possible to obtain an overlay welding material 40 in which an alloy coating layer 42 is formed, which is a rapidly solidified compact exhibiting a rapidly solidified structure. In the case of the form containing "(2) B of 0.7% or more and 3.0% or less" of the present disclosure, the rapidly solidified structure has a block of Cr that is large enough to draw a circle with a diameter of 3 μm or more inside the structure. A metal structure containing boride is preferable.
Note that in the present disclosure, the overlay welding step S4 includes thermal spraying using metal powder.
The obtained build-up weld material 40 may be used as it is as a member constituting various devices, but there is a shaping process (step 5) in which the dimensions and shape of the build-up weld material 40 are shaped in consideration of connection to other components, etc. :S5) may be further implemented. Examples of shaping methods include cutting with a milling machine and polishing with a grindstone.

In addition, as a rapidly solidified molded product having a rapidly solidified structure, for example, a molten Cr-Ni alloy may be injected onto a roll rotating at high speed to rapidly cool it and be formed into a thin strip-shaped cast molded product. Alternatively, the alloy powder may be thermally sprayed and laminated to form a layered body (rapidly solidified body) having a rapidly solidified structure.
In addition, as a method for obtaining alloy powder different from the above-mentioned method, alloy powder is manufactured by applying a powdering process in which the cast compact obtained in the casting process is mechanically crushed to produce alloy powder. Also good. In this case, for example, a ball mill or the like can be used for the powdering step.

FIG. 2 is an example of a method for manufacturing a Cr—Ni alloy according to the present disclosure, and is a process diagram showing a method for manufacturing a powder metallurgy compact. As shown in FIG. 2, the manufacturing process of the powder metallurgy compact is the same as the manufacturing method of the rapidly solidified compact shown in FIG. The difference is that a process (step 6: S6) and a sintering process (step 7: S7) are performed. Therefore, the powder molding step S6 and the sintering step S7 will be explained.
A desired powder compact 60 can be obtained by performing a powder compacting step S6 using the alloy powder 20 obtained by performing the atomizing step S2 or further obtained through the classification step S3. There are no particular limitations on the powder molding method, but for example, in the case of metal powder injection molding, alloy powder 20 is kneaded with plastic or wax as a binder to give fluidity and moldability, and then molded with an injection molding machine. A powder molding step (step 6a: S6a) of filling and molding the powder compact and a degreasing step (step 6b: S6b) of removing the binder remaining in the obtained powder compact 60 can be performed. The degreasing process is performed, for example, by immersing the powder compact in a solvent or heating it in a predetermined atmosphere.

Next, a sintering step S7 is performed in which the powder compact 60 is subjected to sintering heat treatment at a temperature lower than the solidus temperature of the alloy to form a powder metallurgy compact 70. There are no particular limitations on the sintering heat treatment method, and conventional methods can be used. In addition, when the above-mentioned degreasing step S6b is performed by heating, the degreasing step and the sintering step can be performed by adjusting the temperature and atmosphere before reaching the sintering temperature in this sintering step S7. It can also be done all at once. From the viewpoint of densification of the powder metallurgy compact 70, it is more preferable to include a hot isostatic pressing (HIP) treatment at a temperature lower than the solidus temperature of the alloy and at a pressure of 500 atm or more and 3000 atm or less.
The obtained powder metallurgy compact 70 has a sintered structure and may be used as it is as a member constituting various devices. If the powder metallurgy compact 70 is rod-shaped, it can be applied, for example, as an electrode rod of an arc welding machine and used for overlay welding onto a desired base material.
Further, as in the case of the overlay welded material described above, the shaped body 50 may be obtained by further performing a shaping step S5 of shaping the dimensions and shape of the powder metallurgy compact 70 in consideration of connection to other members, etc. . Examples of shaping methods include cutting using a milling machine and polishing using a grindstone.

FIG. 3 is an example of a method for manufacturing a Cr—Ni alloy according to the present disclosure, and is a process chart showing a method for manufacturing a cast molded body. As shown in FIG. 3, the manufacturing process of the cast molded body is the same as the manufacturing method of the rapidly solidified molded body in FIG. 1 in which the melting step S1 is performed, except that the casting process (step 8: S8) is performed thereafter. The molten metal 10 obtained by performing the melting process S1, or the cleaned molten metal 12 obtained by further performing the electrode manufacturing process S1a and the remelting process S1b, is filled into a desired casting mold in the casting process S8, and then cooled and A cast molded body 80 can be obtained by curing. Note that there are no particular limitations on the casting method.
In addition, in order to further reduce the content of impurity components (O, P, and S) in the alloy (increase the cleanliness of the alloy), the melting step S1 mixes and melts the raw materials of the Cr-Ni alloy to form a molten metal. an electrode manufacturing process (step 1a: S1a) in which the consumable electrode 10 is once solidified by casting to manufacture the consumable electrode 11; and a remelting process (step 1b: S1b) in which the consumable electrode is remelted to prepare the cleaned molten metal 12. ) may be applied. There is no particular limitation on the remelting method as long as the cleanliness of the alloy can be improved, but for example, vacuum arc remelting (VAR) or electroslag remelting (ESR) can be preferably used. When the remelting process is applied, the ingot obtained by the remelting becomes a cast molded body.
The obtained cast molded body 80 has a cast structure, but by using a mold having a cooling mechanism such as a water cooling pipe inside the wall surface, for example, it exhibits a rapidly solidified structure in which the cast molten metal is rapidly cooled and solidified. It can be made into a rapidly solidified molded body. Although the cast molded body 80 may be used as it is as a member constituting various devices, a shaping step S5 is further performed to shape the dimensions and shape of the cast molded body 80 in consideration of connection to other components, etc. It may be set to 50. Examples of shaping methods include cutting using a milling machine, grinding using a whetstone, and polishing.

<Alloy products>
The Cr--Ni alloy produced as described above can have both corrosion resistance and wear resistance (earth and sand wear resistance).
As a result, the Cr--Ni alloy product of the present disclosure can be suitably used as various members used in severe corrosive and abrasive environments. The applicable parts include automobile parts (for example, fuel injection system parts, roller chain parts, turbocharger parts, engine exhaust system parts, bearing parts), railway-related parts (for example, bearing parts, pantograph parts), and rolling parts. Bearings and plain bearings (e.g. linear bearings, windmill bearings, water turbine bearings, ventilation fan bearings, mixing drum bearings, compressor bearings, elevator bearings, escalator bearings, planetary probe bearings), construction Equipment parts (e.g. track parts, mixing drum parts), ship and submarine parts (e.g. screw parts), environmental equipment parts (e.g. garbage incinerator parts, crushing machines), bicycles, two-wheeled vehicles and Watercraft parts (e.g. roller chain parts, sprocket parts), machining equipment parts (e.g. molds, rolling rolls, cutting tool parts), oil well equipment parts (e.g. rotating machines (compressors, pumps)) (shafts, bearings)), seawater environment equipment parts (e.g. seawater desalination plant equipment parts, umbilical cables), chemical plant equipment parts (e.g. liquefied natural gas vaporization equipment parts), power generation equipment related parts ( Examples include coal gasifier members, heat-resistant piping members, fuel cell separator members, fuel reformer members), and the like. Among the above-mentioned members, application to oil well equipment members, machining equipment, and environmental equipment members is particularly preferable.

FIG. 4(a) is an example of a Cr-Ni alloy product according to the present disclosure and an industrial product using the same. FIG. 2 is a schematic cross-sectional view of a screw pump used for transporting In a screw pump, the Cr of the present disclosure is used as an alloy coating layer, for example, on the screw surface and casing surface that come into contact with the transported object, as well as on the inner surface of piping members connected to the suction port and the discharge port (not shown). - Ni-based alloy products can be suitably used. The alloy coating layer can be produced in the form of a build-up weld material.
FIG. 4(b) is another example of the Cr—Ni alloy product of the present disclosure and an industrial product using the same, and is a schematic cross-sectional view of an injection mold. In an injection mold, for example, an alloy coating layer on the surface of the mold base material that comes into contact with molten plastic or a mixture of metal powder and binder, which fills the space between the upper mold and the lower mold. The Cr--Ni based alloy product of the present disclosure can be suitably used as a material. The alloy coating layer can be produced in the form of a build-up weld material.
FIG. 4(c) shows another example of the Cr-Ni alloy product of the present disclosure and an industrial product using the same, in which objects to be conveyed, such as rocks and concrete waste, are crushed between swinging tooth plates. It is a cross-sectional schematic diagram of a crushing machine called a jaw crusher. In a crushing machine, the Cr--Ni alloy product of the present disclosure can be suitably used as an alloy coating layer on the surfaces of a fixed tooth plate and a movable tooth plate that are in contact with objects to be crushed, such as rocks. The alloy coating layer can be produced in the form of a build-up weld material.
In addition, in the application example to the above-mentioned industrial product, an example was described in which an alloy coating layer is provided on the surface of the target member, but the entire target member may be composed of the Cr--Ni based alloy product of the present disclosure.

Hereinafter, the present disclosure will be explained in more detail using Examples and Comparative Examples. Note that the present disclosure is not limited to these examples.
(Method for evaluating characteristics of test piece)
(1) Evaluation of abrasion resistance (earth and sand abrasion resistance) Equipment for crude oil extraction is subject to wear due to sand and gravel in the crude oil that it comes into contact with. Therefore, a soil abrasion test was conducted to evaluate the wear resistance. The test method was based on ASTM standard G65. After measuring the pre-test weight of the test pieces obtained by cutting and polishing the molded bodies of each composition, a rotating rubber disk was pressed against the test piece with a predetermined load, and silica sand for testing was placed between the contact surfaces of the two. It was continuously fed for 10 minutes. Thereafter, the weight of the test piece was measured to determine the change in mass before and after the test, and the abrasion volume AVL (unit: mm ³ ) was calculated, taking into account the change in diameter due to the wear and tear of the rubber disk accompanying the test.
As for the wear volume measurement results, "AVL<180" was evaluated as A grade, "180≦AVL<360" was evaluated as B grade, and "360≦AVL" was evaluated as C grade. The results of the earth and sand abrasion resistance evaluation are also listed in Tables 1 to 4.

(2) Corrosion resistance evaluation Equipment for crude oil extraction, which is envisioned as the applicable field of this disclosure, is exposed to strong acid corrosion environments due to the effects of hydrogen sulfide contained in crude oil and hydrochloric acid generated by decomposition of inorganic chlorides. be exposed. Therefore, a boiling sulfuric acid immersion test was conducted to evaluate corrosion resistance. The test method was based on JIS standard G0591: Sulfuric acid corrosion test method for stainless steel, and the test solution used was sulfuric acid at pH 1 diluted with pure water to a concentration of 5% by mass. Test pieces obtained by cutting and polishing molded bodies of each composition were weighed before testing, and then immersed in a boiling test solution for 6 hours. Then, measure the mass of the test piece to find the change in mass before and after the test, and divide this by the surface area of the test piece before the test and the test time to calculate the corrosion rate m (unit: g/(m ² h)). did.
Regarding the measurement results of corrosion rate, "m<3×10 ⁰ " was evaluated as A grade, "3×10 ⁰ ≦m<10 ² " as B grade, and "10 ² ≦m" as C grade. The results of the corrosion resistance evaluation are also listed in Tables 1 to 4.
(3) Microstructure Observation In order to investigate the relationship between corrosion resistance and earth and sand abrasion resistance, the cut surfaces of some of the test pieces were mirror polished and observed using a scanning electron microscope (SEM).

[Example 1]
Raw materials were mixed to have the composition shown in Table 1, melted by high frequency melting method (melting temperature 1500° C. or higher, in a reduced pressure Ar atmosphere) to form a molten metal, and then the molten metal was cast to produce a cast molded body. Since the overlay material to which the alloy of the present disclosure is applied has a fast cooling rate during overlay construction, the mold used has an elongated shape with a diameter of about 20 mm, and the structure of the cast molded body is adjusted to the overlay weld bead. This resulted in a similar quenched structure. Each cast molded body was cut and polished into a predetermined test piece shape according to each of the above-mentioned test methods. No. shown in Table 1. Nos. 1 to 4 are comparative examples in which C was fixed at 1.0%; Samples 5 to 8 had compositions of examples of the present invention in which C was increased to 2.0 to 2.9%. No. Samples Nos. 9 to 14 had compositions of examples of the present invention in which Cr was about 55% or about 60%, the composition other than C was generally fixed, and C was changed to 1.5 to 2.5%. Also, No. No. 15 is a comparative example in which C was increased to 4.5%. No. 16 is the composition of the present invention example in which Cr was reduced to 45.0%. In addition, what is shown as "<0.1%" is contained in a very small amount of less than 0.1%.

FIG. 5 shows the test results of corrosion rate m and wear volume AVL for each test piece. The circled numbers written next to each plot indicate the No. of each composition shown in Table 1. It corresponds to
Regarding earth and sand abrasion resistance, Comparative Example No. 1 containing 1.0% by mass of C. Alloys 1 to 4 were judged to be grade C, and had poor earth and sand abrasion resistance. Comparative example No. 6 and FIG. Scanning electron microscopy (SEM) images of alloys No. 1 to 4 are shown below. Alloy No. 1 had a two-phase structure in which island-like phases were present in a phase having a fine eutectic structure. Also, No. All alloys 2 to 4 had a structure in which fine crystallized substances or precipitates, which appeared to be carbides, were dispersed throughout. Here No. 2 alloy and No. Comparing with 4 alloys, No. In Alloy No. 2, gray portions extending linearly are seen in the white matrix, but the length is short, a few μm. On the other hand, No. The structure of the 4 alloy is No. Although it is similar to Alloy No. 2, the gray part that extends linearly is several tens of μm long. This is thought to be due to the growth of carbides compared to alloy No. 2. The reason why such a difference in structure appeared is due to the balance between Ni and Fe, but it is thought that the width of the carbide was thin at 1 μm or less in any composition, and did not contribute to improving the earth and sand abrasion resistance.

On the other hand, No. 1 containing more than 1.1% by mass of C of the present invention example. In the case of alloys 5 to 16, all alloys achieved earth and sand wear resistance of grade A; AVL<180. Here, in FIG. 5 and no. 6 alloy, No. 6 alloy in Figure 9. 7 and no. SEM observation images of No. 8 alloy are shown. In both images, unlike the case of containing 1.0% by mass of C shown in FIGS. 6 and 7, lumpy carbides approximately larger than 20 μm and displayed in dark gray or black are dispersed. I can see that As a result of analyzing this lumpy carbide using an X-ray analyzer, it was found to be a Cr-based carbide containing Cr as a main component. It is thought that these lumpy Cr carbides crystallized and grew in the liquid phase of the molten alloy during overlay construction, and remained dispersed in the structure when it was rapidly cooled and solidified. .
Looking at the relationship between the amount of lumpy carbide occupying the observation area and the earth and sand wear resistance, No. 3 has no lumpy carbide. Alloys No. 1 to 4 have AVL>400, whereas No. 4 has a large amount of carbides. Alloys 5 to 8 have an AVL<180, and it is thought that the increase in blocky carbides in the structure improves the earth and sand wear resistance.
The difference in the color tone of the carbide indicates that the two carbide forms are different; the black region is M ₇ C ₃ type Cr carbide, and the dark gray region is M ₂₃ C ₆ type Cr. I think it's carbide. The Vickers hardness of each form of Cr carbide is thought to exceed 1000, and both contribute to improving earth and sand abrasion resistance.
On the other hand, the present invention example No. No. 16 had a lower Cr content than the other invention examples and was rated as a B blade. 1 to 4 and the comparative example No. 1 to 4 described below. Compared to 51 to 56, they are equivalent or better. In addition, when C is contained in excess of 1.1% by mass, it is preferable that Cr is in excess of 46.0%.

Next, in FIG. SEM observation images of alloys 9 to 11 are shown. Judging from the color tone of the images, all of them are considered to be M ₇ C ₃ type carbides, but No. 1 containing 1.5% by mass of C. While the size of the carbide in Alloy No. 9 is approximately 15 μm, the size of carbides in Alloy No. 9 containing 2.0% by mass of C is approximately 15 μm. The size of carbides in Alloy No. 10 is approximately 20 μm, and alloy No. 10 contains 2.5% by mass of C. The size of carbides in Alloy No. 11 is approximately 30 μm, and the proportion of carbides in the observation area is increasing. Looking at FIG. 5 here, No. 9, No. 10, No. The wear volume AVL decreased in the order of No. 11 alloys, and it is thought that the earth and sand wear resistance improved due to the increase in carbides in the structure.
Next, in FIG. The SEM observation images of alloys 12 to 14 are shown, and based on the color tone of the images, No. 12 and no. 13 alloy carbide is M ₂₃ C ₆ type, No. 14 alloy is considered to be mainly M ₇ C ₃ type. Although there are differences in carbide form and individual size between the two, the higher the carbon content, the greater the proportion of carbides in the structure, which is thought to be the reason for the difference in soil and sand abrasion resistance.
Furthermore, according to studies conducted by the inventors using equilibrium phase diagram calculations, etc., when the alloy of the present disclosure has a relatively small amount of C, the carbides are of the M ₂₃ C ₆ type, and when the amount of C increases, the M ₇ C ₃ type appears. The more Cr there is, the more C tends to be required for M ₇ C ₃ to appear. Comparing FIGS. 10 and 11, the carbide in FIG. 10 with 55% by mass of Cr is of the M ₇ C ₃ type, whereas the carbide in FIG. 11 with 60% by mass of Cr is mostly of the M ₂₃ C ₆ type. This is in good agreement with the above-mentioned trend.

[Example 2]
Raw materials were mixed to have the composition shown in Table 2, and melted by high frequency melting method (melting temperature 1500° C. or higher, in a reduced pressure Ar atmosphere) to form a molten metal, and then the molten metal was cast to produce a cast molded body. Since the overlay material to which the alloy of the present disclosure is applied has a fast cooling rate during overlay construction, the mold used has an elongated shape with a diameter of about 20 mm, and the structure of the cast molded body is adjusted to the overlay weld bead. This resulted in a similar quenched structure. Each cast molded body was cut and polished into a predetermined test piece shape according to each of the above-mentioned test methods. No. shown in Table 2. Nos. 21 to 26 and 28 are compositions of examples of the present invention; No. 27 is a comparative example in which B is outside the upper limit. These abrasion resistance (earth and sand abrasion resistance) evaluations, corrosion resistance evaluations, and microstructural observations were performed in the same manner as in Example 1 above. In addition, what is shown as "<0.1%" is contained in a very small amount of less than 0.1%.

FIG. 12 shows the test results of corrosion rate m and wear volume AVL for each test piece. The numbers in parentheses written next to each plot indicate the No. of each composition shown in Table 2. It corresponds to
Regarding earth and sand abrasion resistance, No. Alloys No. 21 to 26 achieved earth and sand abrasion resistance of grade A; AVL<180. Here, FIGS. 13 to 15 show No. 1 of the present invention example. SEM observation images of each alloy No. 21 to No. 26 are shown. In both images, lump-like borides are dispersed in black color and have an elongated cross-sectional shape of approximately 3 μm in the width direction and more than 30 μm in the longitudinal direction. As a result of analyzing this lumpy boride using an X-ray analyzer, it was found to be a Cr-based boride containing Cr as a main component. It is thought that this lumpy Cr boride crystallizes and grows in the liquid phase of the molten alloy during overlay construction, and remains dispersed in the structure when it is rapidly cooled and solidified. It will be done.
This lumpy Cr boride is considered to be hard with a Vickers hardness exceeding 1000, and it is believed that the increase in this hard Cr boride contributed to the improvement in the earth and sand abrasion resistance.
Next, Comparative Example No. 4.0% by mass of B. Alloy No. 27 achieved A grade in earth and sand abrasion resistance, but had a very poor corrosion resistance of C grade. The SEM observation image is shown in FIG. No. 21-26. No. 27 has the largest amount of Cr boride dispersed. From this, No. It is thought that in No. 27, more Cr was consumed during crystallization of Cr boride, and Cr in other parent phases decreased, resulting in deterioration of corrosion resistance.
Next, the present invention example No. with 42.0% Cr. Alloy No. 28 was grade B in both corrosion resistance and wear resistance. The SEM observation image is shown in FIG. 17. Compared to Nos. 21 to 26, the individual Cr borides were thin and short. This is considered to be because the amount of Cr boride crystallized was reduced due to the small amount of Cr, and also because the amount of Cr originally contained in the matrix was small. This No. Although No. 28 is inferior to other examples of the present invention, No. 28 is a comparative example described below. Compared to 51 to 56, they are equivalent or better. In addition, when constituting Cr boride, it is preferable that the amount of Cr is 45% or more.

[Example 3]
Raw materials were mixed to have the composition shown in Table 3, melted by high frequency melting method (melting temperature 1500° C. or higher, in a reduced pressure Ar atmosphere) to form a molten metal, and then the molten metal was cast to produce a cast molded body. Since the overlay material to which the alloy of the present disclosure is applied has a fast cooling rate during overlay construction, the mold used has an elongated shape with a diameter of about 20 mm, and the structure of the cast molded body is adjusted to the overlay weld bead. This resulted in a similar quenched structure. Each cast molded body was cut and polished into a predetermined test piece shape according to each of the above-mentioned test methods. No. shown in Table 3. Nos. 31 to 35 are examples of the present invention in which C was fixed at 1.0%; No. 36 and 37 contain more than 1.0% C. Nos. 38 and 39 are examples of the present invention in which C was less than 1.0%. No. No. 40 is an example of the present invention in which 2.2% of C was added to increase the ratio of C to Nb. No. 41 is No. This is an example of the present invention having a composition similar to No. 34, but with the ratio of Nb and C kept at 8:1 and both increased. These abrasion resistance (earth and sand abrasion resistance) evaluations, corrosion resistance evaluations, and microstructural observations were performed in the same manner as in Example 1 above.

FIG. 18 shows the test results of corrosion rate m and wear volume AVL for each test piece. The numbers in parentheses written next to each plot indicate the No. of each composition shown in Table 3. It corresponds to
All alloys were judged to be grade A in both earth and sand abrasion resistance and corrosion resistance, and had good properties. 19 to 23 show scanning electron microscopy (SEM) images of each alloy of the invention examples. For example, No. 1 in FIG. Alloy 31 has lump-like, rod-like, and dot-like crystallization or precipitates that are visible in white contrast, and the parent phase includes a ferrite phase that is visible in dark gray contrast, and an island-like austenite phase that is visible in light gray contrast. It was a two-phase structure.
No. Similarly, Alloy No. 32 had a structure in which crystals or precipitates of 20 μm or less in size, visible in white contrast, spread out in the form of lumps, rods, dots, feathers, and branches, dispersed throughout. EDX and X-ray analyzes of these white contrast areas revealed that they were Nb-based carbides containing Nb as a main component. In addition, among the two-phase structures, there is a eutectic structure visible in black contrast in a part of the island-like austenite phase, and as a result of EDX and X-ray analysis, it was found that it is a Cr-based carbide with Cr as the main component. there were.
On the other hand, No. Alloy No. 33 also has Nb-based carbides that are visible in white contrast, but No. No lumpy Nb-based carbides of about 10 μm as seen in Alloys 1 and 2 were observed, and the structure was a dispersion of crystallized or precipitated substances of 20 μm or less that spread out in rod-like, dot-like, feather-like, and dendritic shapes.

Similarly, FIGS. 20 to 23 show No. 2 of the invention example. SEM observation images of the structures of alloys 34 to 41 are shown, and all alloys are similar to the aforementioned No. Similar to Nos. 31 to 33, the structure had crystallized or precipitated substances dispersed throughout in the form of lumps, rods, dots, feathers, and dendritic shapes. All of these alloys were judged to be grade A in both earth and sand abrasion resistance and corrosion resistance, and had good properties.
By the way, when suppressing wear by dispersing hard particles (Nb-based carbide) in the structure, the effect will be smaller if the strength of the hard particles themselves is low, so it is desirable that the hard particles be in the form of a block of a certain size. I think that the. However, for example, alloy No. of the present invention example. In No. 33, most of the eutectic Nb-based carbides are present, and no lumpy Nb-based carbides are observed, but good earth and sand abrasion resistance is obtained compared to other alloys of the present disclosure. This is because in the alloy of the present disclosure, Nb-based carbide exists in the hard ferrite phase of the two-phase structure that constitutes the matrix, so the ferrite phase supplements the strength of the Nb-based carbide, and this eutectic It is thought that the region acts as a virtual hard particle.
Therefore, it is considered that the wear resistance of the alloy of the present disclosure is influenced not only by the number and size of lumpy Nb-based carbides, but also by the total area, distribution state, shape, etc. of the Nb-based carbide phase. For the SEM photographs of each alloy taken in multiple fields of view, including the SEM photographs in Figures 19 to 23, the Nb-based carbide part visible in white contrast and the other parts were binarized using image analysis software. When the area ratio occupied by the whole visual field was calculated, it was approximately in the range of 6 to 20%.

According to studies conducted by the inventors using equilibrium phase diagram calculations, Cr-based carbides appear in the alloy of the present disclosure not only when there is a large amount of Cr, but also when C is added in excess of Nb. The Cr-based carbide at this time is mainly of the M ₂₃ C ₆ type. No. In No. 32, No. 33, and No. 36 alloys, eutectic Cr-based carbides appear inside the austenite phase, and No. 32, No. 33, and No. 36 alloys have eutectic Cr-based carbides inside the austenite phase. At No. 40, elongated lumpy Cr-based carbides appear. These Cr-based carbides are hard and contribute to wear resistance like Nb-based carbides, but on the other hand, there is a concern that Cr in the matrix is consumed in the production of Cr-based carbides, which may deteriorate corrosion resistance. There is. Therefore, care must be taken not to increase the amount of C added excessively.

[Comparative example]
In order to compare the levels of corrosion resistance and abrasion resistance (earth and sand abrasion resistance) in the Cr-Ni alloy of the present disclosure, four types of powders with compositions corresponding to commercially available overlay materials for surface modification shown in Table 4, Powders of two types of Cr-based alloys (50Cr and 63Cr) without the addition of C, B, or Nb were applied to the SUS304 base metal using a PTA overlay welding device, and the weld beads formed were cut and polished to prepare test pieces. , boiling sulfuric acid immersion test and earth and sand abrasion test were conducted. The test conditions for each test were the same as those shown in the method for evaluating the characteristics of the test piece described above. Table 4 shows the composition, corrosion resistance, and earth and sand abrasion resistance of commercially available overlay materials and comparative Cr-based alloys, and FIG. 24 shows the test results of the corrosion rate and earth and sand abrasion volume of each overlay material.
Among the overlay materials compared this time, none achieved A grade in both corrosion resistance and earth and sand abrasion resistance. Commercially available No. It can be seen that the alloy of the present disclosure achieves both corrosion resistance and earth and sand abrasion resistance as well as or better than those of Nos. 51 to 54.

The above-described embodiments and examples have been described to aid understanding of the present invention, and the present invention is not limited to the specific configurations described. For example, it is possible to replace a part of the configuration of the embodiment with a configuration that is common technical knowledge of a person skilled in the art, or it is also possible to add a configuration that is common technical knowledge of a person skilled in the art to the configuration of the embodiment. In other words, the present invention allows deletion, replacement with other configurations, and addition of other configurations to some of the configurations of the embodiments and examples of this specification without departing from the technical idea of the invention. It is possible.

10... Molten metal 11... Consumable electrode 12... Cleaned molten metal 20... Alloy powder 40... Overlay welding material 41... Base material 42... Alloy coating layer 50... Shaped body 60... Powder compact 70... Powder metallurgy compact 80... Casting molding body

Claims (5)

In mass%,
Cr of more than 40.0% and 65.0% or less,
Fe of 4.0% or more and 30.0% or less,
C of 0.5% or more and 2.5% or less,
Contains 6.4% or more and 20% or less Nb,
The remainder consists of Ni and unavoidable impurities,
The Ni is 15% or more,
A Cr--Ni alloy that has a structure in which crystallized or precipitated Nb-based carbides are dispersed and is used for producing rapidly solidified compacts. The Cr-Ni alloy according to claim 1, wherein the Cr-Ni alloy is an alloy powder. A method for producing a Cr-Ni alloy according to claim 2, comprising:
a melting step of melting the raw material of the Cr-Ni alloy to form a molten metal;
A method for producing a Cr--Ni alloy, comprising: an atomizing step of producing an alloy powder from the molten metal. A method for producing a Cr-Ni alloy according to claim 2, comprising:
a melting step of melting the raw material of the Cr-Ni alloy to form a molten metal;
a casting step of casting the molten metal to form a cast molded body;
A method for producing a Cr--Ni alloy, comprising the step of mechanically pulverizing the cast compact to produce an alloy powder. A rapidly solidified molded body obtained using the Cr-Ni alloy according to claim 1 or 2.

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