JPH0465896B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a highly corrosion-resistant amorphous amorphous alloy suitable as a corrosion-resistant material in a strongly alkaline and harsh corrosive environment such as high-temperature concentrated sodium hydroxide. [Prior Art] Low carbon steel, nickel alloy, etc. are used in caustic alkali, but they do not have sufficient corrosion resistance because they suffer from brittle fracture or increase the corrosion rate at high temperatures. On the other hand, the present inventors have previously developed pitting corrosion resistance, intercalation corrosion resistance,
A highly corrosion-resistant amorphous nickel-based alloy with general corrosion resistance was discovered, and patent application No. 132290 (1983) was published.
No. 57120). This consists of the following four inventions. (1) A highly corrosion-resistant amorphous material containing 5 to 40 atomic percent Cr and 15 to 35 atomic percent P, with the remainder essentially Ni, and is resistant to pitting, interlocking, and general corrosion, and is resistant to harsh corrosive environments. Asnickel-based alloy. (2) Contains 5 to 40 atom% of Cr and 15 to 35 atom% of P, and contains one or more of the following: 3 atom% or less of Al, 10 atom% or less of Mo, and less than 40 atom% of Fe. The total content of Cr, P, Al, Mo, and Fe is less than 60 atomic percent, and the remainder is essentially Ni. Highly corrosion-resistant amorphous for pitting, interlocking, and general corrosion resistance that can withstand harsh corrosive environments. Asnickel-based alloy. (3) Contains 5 to 40 atom% of Cr and 5 to 35 atom% of P, and further contains C, Si, and B of up to 20 atom% each.
Contains one or more of P, C, Si, and B in a total of 15 to 35 atomic percent, and the remainder is essentially Ni, making it resistant to pitting, intercalation, and corrosion that can withstand harsh corrosive environments. Highly corrosion-resistant amorphous nickel-based alloy for general corrosion. (4) Contains 5 to 40 atom% of Cr and 5 to 35 atom% of P, and further contains C, Si, and B of up to 20 atom% each.
Al containing one or more of the following in a total of 15 to 35 atomic % of P, C, Si, and B, and 3 atomic % or less,
Contains one or more of Mo at 10 atomic % or less and Fe at less than 40 atomic %, Cr, P, C, Si, B,
A highly corrosion-resistant amorphous nickel-based alloy with a total content of less than 60 atomic percent of Al, Mo, and Fe, with the remainder essentially Ni, and is resistant to pitting, interlocking, and general corrosion, and is resistant to harsh corrosive environments. However, these materials were expected to be corrosion-resistant materials in strong acids, and were not intended as corrosion-resistant materials in high-temperature alkalis. [Problems to be Solved by the Invention] High-temperature concentrated caustic alkali is highly corrosive, and there is no metal material that can be used safely. Therefore, there has been a strong desire for a new metal material that can withstand use in such a corrosive environment where it is extremely difficult to use normal metal materials. [Means for Solving the Problems] An object of the present invention is to provide an alloy that is difficult to passivate metals, such as high-temperature concentrated caustic alkali, and that can withstand extremely harsh corrosive environments. Normally, alloys are crystallized in the solid state, but if we apply a method that prevents the formation of superperiodic regularity in the atomic arrangement during the solid formation process, such as by limiting the alloy composition and solidifying it by ultra-rapid cooling from the molten state, the crystal structure An amorphous structure similar to that of a liquid is obtained, and such an alloy is called an amorphous alloy.
Most amorphous alloys are homogeneous single-phase alloys of supersaturated solid solutions, and have significantly higher strength than conventional practical metals, and exhibit various properties, including unusually high corrosion resistance, depending on the composition. The present inventors conducted research to utilize the characteristics of such amorphous amorphous alloys, and as a result, they were able to prevent pitting corrosion, intermittent corrosion, and general corrosion even in highly corrosive aqueous solutions such as strong acids or aqueous solutions containing high concentrations of chlorine ions. We discovered a highly corrosion-resistant amorphous nickel-based alloy that was not susceptible to corrosion, and filed an application earlier as Japanese Patent Application No. 132290/1983. As mentioned above, high-temperature concentrated caustic alkali is particularly corrosive and produces few stable corrosion products, and corrosion resistance cannot be obtained unless the alloy itself has the ability to form a stable corrosion product protective film. As a result of further research while considering various properties of amorphous alloys, the present inventors found that among the alloys described in the above-mentioned Japanese Patent Application No. 132290/1984, an alloy with a particularly stable corrosion product film in high-temperature alkalis was found. Alternatively, by adding elements that have a greater ability to form corrosion product films to similar alloys or elements that chemically stabilize the alloy, stable protection can be achieved even in harsh corrosive environments such as high-temperature concentrated caustic alkalis. The present invention was accomplished by discovering that an amorphous amorphous alloy with high corrosion resistance can be obtained by forming a film. The present invention consists of the first and second inventions shown in claims 1 and 2,
The following Table 1 shows the constituent elements and content rates of these first and second inventions.

【table】

[Table] [Function] Amorphous amorphous alloys obtained by various methods for producing amorphous alloys, such as ultra-rapid solidification of molten alloys having the above composition or sputter deposition, are monomers in which the above-mentioned elements are uniformly dissolved. It is a phase alloy. Therefore, a protective film is formed on the amorphous alloy of the present invention that is extremely uniform and guarantees high corrosion resistance. Metal materials easily dissolve in high-temperature concentrated caustic solutions, so in order to use metal materials in such an environment, it is necessary to provide the metal materials with the ability to form a stable protective film.
This is achieved by creating an alloy containing the required amount of effective elements. However, in the case of crystalline metals, when a large number of various alloying elements are added, a multiphase structure with different chemical properties is often formed, and a desired corrosion resistance may not be achieved. Moreover, the occurrence of chemical non-uniformity is rather detrimental to corrosion resistance. On the other hand, the amorphous amorphous alloy of the present invention is a homogeneous solid solution, and furthermore, the amorphous amorphous alloy of the present invention uniformly contains the necessary amount of effective elements that can form a stable protective film. forms a uniform protective film and exhibits sufficiently high corrosion resistance. That is, a metal material that can withstand high temperature and concentrated alkali must have a high ability to form a protective film that is stable in a non-oxidizing environment and uniformly forms a corrosion product film on the material. This is achieved with the alloy composition of the present invention, and the alloy's amorphous structure allows alloys of complex composition to be created as single-phase solid solutions, ensuring uniform protective coating formation. Next, the reason for limiting the composition of each component in the present invention will be described. Ni is the basic element of the alloy of the present invention,
It is an element that coexists with metalloids such as P, C, B, and Si to form an amorphous structure, and is also an element that helps the action of Cr, which is responsible for corrosion resistance. Cr is an element responsible for corrosion resistance by forming a corrosion product film on the alloy of the present invention immersed in high-temperature concentrated alkali. Too little Cr will not provide sufficient corrosion resistance, and too much will make it difficult to form an amorphous structure. Therefore, it is set at 10 to 40 atom%. Mo is an element that promotes the formation of a protective film by Cr, but adding a large amount is actually harmful. Cu is an element that increases the chemical stability of the alloy, but when added in large amounts, it becomes difficult to obtain an amorphous structure. Pb is an element that forms a protective film, but adding a large amount makes it difficult to form an amorphous structure. Therefore, in the first and second inventions of the present invention, Pb is 7 at%
Hereinafter, Mo and/or Cu will each be 7 atomic % or less. As mentioned above, P is not only effective in coexisting with Ni to form an amorphous structure, but also in forming an amorphous structure with Cr.
It is an element that promotes the formation of a protective film whose main component is However, in highly corrosive environments such as hot water and concentrated alkali, alloys containing a large amount of P may develop a phosphate film with low protective properties due to oxidation of P. Therefore, in the first and third aspects of the present invention, P is in the range of 15 to 23 at %. B, C, and Si are also elements that are effective in coexisting with Ni to form an amorphous structure and can substitute for P. However, in order not to reduce the effect of P that promotes the formation of a protective film, it is necessary to
It is not preferable to substitute P by more than 7 atomic % in total of any one or two of them. Therefore, in the second and fourth aspects of the present invention, B, C and Si
The total amount of any one or two of these must be 7 atomic % or less, and the total amount with P must be 15 to 23 atomic %. The amorphous amorphous alloy of the present invention can be produced by various methods that are already widely used, namely, methods of ultra-rapidly solidifying a liquid alloy, various methods of forming an amorphous amorphous alloy through a gas phase, and methods of solidifying by ion implantation. Any method for producing an amorphous alloy, such as a method for destroying the long-period structure of , may be used. As an example, an apparatus for producing the amorphous alloy of the present invention is shown in FIG. The area surrounded by dotted lines is evacuated and then filled with inert gas. In the figure, 2 is a quartz tube with a vertical nozzle 3 at its lower tip.
Through the inlet 1 provided at the upper end of the quartz tube 2, the raw material 4 and an inert gas for preventing oxidation of the raw material can be introduced. A heating furnace 5 is installed around the quartz tube 2 to heat the sample 4. A high speed rotating roll 7 is placed vertically below the nozzle 3 and is rotated by a motor 6. To produce an amorphous amorphous alloy, a raw material 4 having a predetermined composition is put into a quartz tube 2, the apparatus is first evacuated to about 10 ^-5 Torr, and then filled with inert gas. Then,
The raw material 4 is heated and melted in a heating furnace 5, and this molten metal is injected by a motor 6 onto the outer peripheral surface of a roll 7 which is rotating at a high speed of 1000 to 10000 rpm using pressurized inert gas. It is done by certain things.
By this method, for example, thickness 0.1 mm, width 10 mm,
The amorphous alloy of the present invention can be obtained as a long thin plate of several meters in length. Example Raw material metals were mixed to have the compositions shown in Table 2, and raw material alloys were produced in an argon arc melting furnace. By remelting these alloys in an argon atmosphere and ultra-rapidly solidifying them using the single roll method shown in Fig. 1, the alloys are made into 0.01 to 0.05 mm thick and 1 to 1 mm wide.
An amorphous alloy thin plate of 3 mm and a length of 3 to 20 mm was obtained. The formation of an amorphous structure was confirmed by X-ray diffraction. The surfaces of these alloy samples were polished in cyclohexane to 1000 grit silicon carbide paper. Next, a predetermined length of the alloy sample was cut out, and the polarization curve was measured in a boiling 50% NaOH solution. The results obtained are shown in Table 3.

【table】

【table】

[Table] The maximum current density of the active state of the amorphous amorphous alloy of the present invention is smaller than that of the comparative example, which proves that the alloy of the present invention has high corrosion resistance. [Effects of the Invention] As detailed above, the amorphous alloy of the present invention is a highly corrosion-resistant alloy that forms a stable protective film and is not corroded even in a highly corrosive environment such as high-temperature caustic alkali. Furthermore, since any of the already widely used amorphous alloy production techniques can be applied to the production of the alloy of the present invention, there is no need for special equipment, and the alloy of the present invention has excellent practicality. .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus for producing the amorphous alloy of the present invention. DESCRIPTION OF SYMBOLS 1... Raw material inlet, 2... Quartz tube, 3... Nozzle part, 4... Raw material, 5... Heating furnace, 6... Motor, 7... High speed rotating roll.

Claims (1)

[Claims] 1 10 to 40 at% Cr, 15 to 23 at% P, and Pb
A highly corrosion-resistant amorphous amorphous alloy containing 7 at% or less of Mo and/or 7 at% or less of Cu, the remainder being substantially Ni, and having corrosion resistance in a strongly alkaline corrosive environment. 2 Contains 10 to 40 at% Cr and 7 at% or less Pb,
and contains up to 7 atom % of Mo and/or up to 7 atom % of Cu, and further contains one or more selected from the group consisting of B, C, and Si, in total of up to 7 atom %, and P for a total of 15 Contains ~23 atomic%, the remainder substantially
A highly corrosion-resistant amorphous amorphous alloy made of Ni that has corrosion resistance in strongly alkaline corrosive environments.