JP2789786B2 - Ni-base alloy powder with excellent corrosion resistance for manufacturing structural members - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to metal powder injection molded products for chemical plant equipment, conductor rolls for continuous electroplating lines, etc.
Ni for manufacturing structural parts where corrosion by acid solution is a problem
It relates to a base alloy powder.

[Conventional technology]

In general, structural parts where corrosion by acid solution is a problem, such as chemical plant plant equipment and conductor rolls in continuous electroplating lines, contain Cr: 25-33%, Mo: 16-23%, and the rest: Ni In addition, a Ni-based alloy powder composed of unavoidable impurities was used as a raw material powder, and this was produced by hot isostatic pressing. It is known that the compacted body manufactured in this way has excellent wear resistance and excellent corrosion resistance.

[Problems to be solved by the invention]

However, equipment used in recent chemical plants and conductor rolls in continuous electroplating lines are required not only to have high abrasion resistance but also to have further corrosion resistance to acid solutions. There is a tendency that it is required to reduce the number of times of replacement and prolong the maintenance cycle so that the operation can be continuously performed for a long time.

In such a situation, the equipment used in the chemical plant made of the conventional Ni-based alloy powder and the conductor roll of the continuous electroplating line, etc., can not sufficiently satisfy the requirement for the corrosion resistance. Did not.

[Means for solving the problem]

Therefore, the present inventors have studied to solve such problems and to manufacture equipment of a chemical plant composed of a compacted Ni-based alloy having more excellent corrosion resistance, conductor rolls of a continuous electroplating line, and the like. As a result, (1) The conventional Ni-based alloy powder contains 400 to 600 ppm of oxygen as an unavoidable impurity, and the conventional Ni-based alloy powder containing this oxygen is subjected to hot isostatic pressing. As a result, oxides precipitate at the old powder grain boundaries, and when this oxide precipitates at the old powder grain boundaries, corrosion occurs due to local battery action. It proceeds easily, and sufficient corrosion resistance cannot be obtained.

(2) In order to obtain a Ni-based alloy powder having excellent corrosion resistance without precipitating the oxide at the old powder grain boundary of the compacted Ni-based alloy, it is necessary to further reduce oxygen contained in the Ni-based alloy powder. Yes, this oxygen needs to be reduced to less than 200 ppm.

(3) Even if the oxygen content of the Ni-based alloy powder is reduced to 200 ppm or less, it is necessary to appropriately adjust the carbon content in order to completely prevent precipitation at the old powder grain boundary. Increasing the carbon content contained than before, C: 50-200p
It can be solved by setting it to pm.

That's the finding.

The present invention has been made based on this finding, and contains Cr: 25 to 33%, Mo: 16 to 23%, and C: 50 to 200 ppm by weight, and the rest: A Ni-based alloy powder comprising Ni and unavoidable impurities, wherein the oxygen contained as the unavoidable impurities is characteristic of the Ni-based alloy powder excellent in corrosion resistance specified to 200 ppm or less.

Next, the reason why the component composition of the Ni-based alloy powder of the present invention is limited as described above will be described.

(A) Cr and Mo Both of these components have the effect of improving the corrosion resistance by forming a solid solution in the base material and improving the wear resistance of the alloy by forming an intermetallic compound that is finely dispersed in the base material. When the content is less than Cr: 25% and Mo: less than 16%, desired effects cannot be obtained in the above-mentioned action. On the other hand, when these contents exceed Cr: 33% and Mo: 23%, The content of the compacted body was determined to be Cr: 25 to 33% and Mo: 16 to 23%, respectively, in order to easily cause cracking during machining.

(B) C The C component has the effect of stabilizing oxygen dissolved in the matrix, preventing oxides at the former powder grain boundaries of the compacted body from precipitating, and improving corrosion resistance. If it is less than 50 ppm, the desired effect cannot be obtained, while if it exceeds 200 ppm, carbides and the like are precipitated at the old grain boundaries, and the corrosion resistance and toughness are not sufficient, which is not preferable. Therefore, the content of C is 50
It was determined to be ~ 200 ppm.

(C) O ₂ oxygen is contained as an unavoidable impurity in the Ni-based alloy powder, but if its content exceeds 200 ppm, an oxide precipitates at the old powder grain boundary of the compacted body, and this oxide becomes the old powder grain. If it precipitates in the field, corrosion tends to proceed due to the action of the local battery, and sufficient corrosion resistance cannot be obtained. Therefore, in order to improve the corrosion resistance, the content of oxygen contained as an inevitable impurity in the Ni-based alloy powder is specified to be 200 ppm or less.

The Ni-based alloy powder of the present invention has a predetermined component composition
It is manufactured by a gas atomization method in which a Ni-based alloy ingot is melted using a high-frequency melting furnace, the carbon content is adjusted by adding artificial graphite particles, and the obtained molten metal is sprayed using a non-oxidizing gas. The structure of the consolidated body obtained by hot isostatic pressing the Ni-based alloy powder is a two-phase structure composed of a σ phase and a γ phase in which the old powder grain boundaries have disappeared.

〔Example〕

Next, the present invention will be specifically described based on examples.

Using a normal vacuum high-frequency heating furnace, degree of vacuum: 1 × 10 ^-4 torr
In a vacuum atmosphere, it is melted together with artificial graphite particles with a diameter of about 20 mm to adjust the carbon component composition of the molten alloy.
The base alloy melt was adjusted. The temperature of this Ni-base alloy melt is 1500
° C, poured into a preheated tundish, dropped it from the nozzle provided at the bottom, and sprayed nitrogen gas from a dedicated spray nozzle under the conditions of pressure: 25 kg / cm ² , flow rate: 12 Nm ³ / min The powder was spouted and powdered to produce Ni-based alloy powders 1 to 10 of the present invention and comparative Ni-based alloy powders 1 to 3 having the component compositions shown in Table 1. The Ni-based alloy powder thus obtained was filled in a stainless steel capsule, and the heating temperature was 400.
° C, degree of vacuum: maintained in a vacuum atmosphere of 10 ^-5 torr for 12 hours,
The gas adsorbed on the powder surface was subjected to a vacuum degassing treatment and sealed to produce a vacuum sealed structure.

Temperature of the above vacuum sealed structure: 1150 ° C, pressure: 1000kg / c
The hot isostatic press and the Ni-based alloy powder were compacted under the condition of holding at m ² for 2 hours. After observing the metal structure of the compacted body obtained in this way, for the purpose of evaluating corrosion resistance, 50
_{% H 2 SO 4 + 42glFe 2} (SO 4) ₃ of boiling solution were tested in ASTM-G28A soaking for 24 hours, showed these measurement results in Table 1, respectively.

From the results shown in Table 1, the Ni-based alloy powders of the present invention 1 to
The metallographic structure of the compacted body prepared in Step 10 is composed of a σ phase and a γ phase, whereas the metallographic structure of the compacted body made of a conventional Ni-based alloy powder is different from the σ phase and the γ phase. Oxide precipitates, and accordingly, the corrosion rate of the compacted body made of the Ni-based alloy powders 1 to 10 of the present invention is smaller than the corrosion rate of the compacted body made of the conventional Ni-based alloy powder. It turns out that it is very small.

Comparative Ni having a composition outside the scope of the present invention
Base alloy powders 1 to 3 (in Table 1, compositions out of the scope of the present invention are indicated by asterisks). It can be seen that in the metal structure of the manufactured compact, oxides or carbides are precipitated in addition to the σ phase and the γ phase, and accordingly, the corrosion resistance is inferior.

[Effects of the Invention] As described above, when using the Ni-based alloy powder of the present invention to manufacture equipment for a chemical plant and a conductor roll of a continuous electroplating line, etc., it shows extremely excellent corrosion resistance and has an excellent industrial effect. To demonstrate.

Continuation of front page (72) Inventor Tsutomu Oka 1230 Kamijiya, Okegawa-shi, Saitama Mitsubishi Metal Corporation Okegawa Daiichi Mfg. Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) B22F 1/00 C22C 19/05

Claims (1)

(57) [Claims] 1. A Ni-based alloy powder containing 25 to 33% by weight of Cr, 16 to 23% of Mo: 50 to 200 ppm by weight, and the balance of: Ni and unavoidable impurities. O ₂ contained as inevitable impurities, O _2: structural member for producing Ni-based alloy powder having excellent corrosion resistance, characterized in that defined in 200ppm or less.