JPH01138379A - Plunger of high pressure water generating pump - Google Patents

Abstract

PURPOSE:To drastically improve the erosionproofness and abrasion resistance by forming the core member of a plunger from carbon steel and forming a solid phase diffusion joint layer from the alloy powder containing one or the both of Ni and Co having a specific linear expansion coefficient as main constituent on the surface of the core member. CONSTITUTION:A pump for generating high pressure water pressurizes the water sucked into a pump chamber to a high pressure by reciprocating a plunger 1 fitted in slidable ways into a cylinder 12 through a packing 13 and discharges said high pressure water through a connecting rod 15 by the revolution of a crankshaft 16. In this case, the plunger 11 is made by using carbon steel as core member, and a solid phase diffusion joint layer 4 consisting of the alloy powder containing one or the both of Ni and Co having a linear expansion coefficient of 12-15X10<-6>/ deg.C in a temperature range of 20-600 deg.C as main constituent is formed on the surface. The solid phase diffusion joint layer is formed, for example, through the hot hydrostatic pressurizing method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a plunger for a high-pressure water generating pump, and particularly relates to improvements in its corrosion resistance and wear resistance.

[Conventional technology]

High-pressure water generation pumps are used in various industrial fields including the steel industry and mining industry, as well as in the field of fire fighting. The following will explain the case of the steel manufacturing industry, which operates continuously, has a high operating rate, and is used under severe operating conditions.

One example of the use of a high-pressure water generating pump in the steel industry is a pump for generating high-pressure water for a descaler for removing oxidized scale on the surface of rolled material in a rolling mill. The role of the pump in this case is to forcefully transport industrial water, and the pressure is generally 200 to 400 kg.
/ cs”, and the reciprocating speed of the plunger in the cylinder of the pump is on average 1.5-2 m/sec.
e and high speed.

FIG. 3 is a schematic diagram of such a high-pressure water generating pump, in which a plunger 11 is slidably disposed within a cylinder 12 via a packing 13.

A cross rod 14 is connected to the plunger 11, which is connected to the crankshaft 16 via a connecting rod 15.
It is driven back and forth. In this way, the plunger 11 has the role of receiving force from the outside and transmitting it to the water, and is the most important part that generates pressure.

In this way, high-pressure water generation pumps generate water at high pressure.

The plunger, gasket, and spacer mentioned above are especially important for generating high pressure because they are used for high-speed pressure feeding. Materials are being developed one after another to improve pump performance.

On the other hand, despite the development of such high-performance pump materials, the development of plungers has lagged behind, and surface treatments such as plating and thermal spraying have been used to cope with the aforementioned high wear-resistant packing containing carbon. The current situation is that it is tied to In other words, since the plunger cannot withstand water and comes into contact with water, its material is stainless steel (SO3304) for rust prevention.
etc.), and in order to further impart corrosion and wear resistance, the surface is generally plated with hard chrome or thermally sprayed with various materials.

[Problem that the invention seeks to solve]

However, the thickness of the film is essentially several tens to hundreds of microns.
Since it is as thin as 1.5 ft (m), it is corrosion resistant by plating on the plunger of conventional high-pressure water generation pumps.

This plating film is used when trying to impart wear resistance.

There is a problem in that when it comes into contact with hard packing, it immediately peels off, and its effectiveness is small.

On the other hand, when thermal spraying is used, depending on the material, it is easy to apply thick layers, and the thickness of the surface coating can be reduced to about 0.5 to 1 mm.Also, Ni-based materials have excellent corrosion resistance. has also been developed. However, since the sprayed film inherently contains micropores, when applied to the plunger of a high-pressure water generation pump, water passes through the pores and micropores in the sprayed film under high pressure and connects to the sprayed film. Reaching the boundary with the base material,
Due to the high osmotic pressure here, there is also the problem that the sprayed film peels off during use. Furthermore, a major problem with thermal sprayed coatings is that because the thermal sprayed material is melted and coated on the component, the structure takes a form similar to that of a cast structure, which is particularly weak in impact resistance, and the coating is prone to cracking during use. .

In view of these conventional problems, this invention has excellent corrosion and abrasion resistance that does not easily peel off due to contact with highly hard packing or high osmotic pressure of water, or crack due to impact. The purpose of the present invention is to provide a plunger for a pump for generating high-pressure water.

[Means for solving problems]

Therefore, the present invention provides a plunger for a high-pressure water generation pump in which the core material of the plunger is made of carbon steel, and the surface of the core material has a linear expansion coefficient of 12
Ni, C which is ~15 × 10−&/°C.

A solid phase diffusion bonding layer is formed using an alloy powder containing one or both of these as main components.

Here, the solid phase diffusion bonding layer in the present invention can be realized by, for example, hot isostatic pressing (HrP).

[Effect]

In this invention, since the bonding layer is formed on the surface of the plunger core material by solid-phase diffusion bonding, a 100% bonding layer without micropores can be formed with any thickness, and it is almost the same as the core material. Since the bonding layer was formed using Ni and Co alloy powders with the same coefficient of linear expansion, no cracks or the like occur during solid-phase diffusion bonding, and a sound corrosion-resistant and wear-resistant bonding layer is formed.

〔Example〕

Hereinafter, the present invention will be explained based on Examples.

Table 1 shows an example of the chemical composition of the alloy powder of the solid-phase diffusion bonding layer in the plunger of the high-pressure water generating pump of the present invention. Here, the chemical component ranges in Table 1 take into consideration corrosion resistance and wear resistance, but the reason for limiting the respective component ranges is as follows.

C: O, t~2%. C forms a carbide with Cr and W,
It is an indispensable element for improving wear resistance, and its effect is not effectively exhibited if it is less than 0.1%. On the other hand, if there is too much C, corrosion resistance and toughness will be poor.
Considering these points, a more preferable content of C, which must be suppressed to 0.5 to 1.5%, is 0.5 to 1.5%.

st: o, s~3%. The plunger according to the present invention is manufactured by obtaining an alloy powder from a molten alloy having a predetermined chemical composition by an atomization method, as described later, and then using a hot isostatic pressing method (HI).
Si is an essential element to improve the fluidity of the molten alloy during atomization and to make the powder particle size uniform, and Si is an essential element for making the powder particle size uniform. If the amount is less than that, these effects will not be effectively exhibited. However, if too much Si is present, it will have a significant negative effect on toughness, so it must be kept at 3% or less. Considering these points, a more preferable range of Si is 1 to 2%.

S: O, S ~ 3%. B forms boride with Cr and W, contributing to improvement of corrosion resistance and wear resistance, and also contributes to improving corrosion resistance and wear resistance.
It has the effect of increasing the hardness of the O matrix, and in order to effectively exhibit these effects, it must be contained in an amount of 0.5% or more. However, if it exceeds 3%, not only the toughness of the alloy decreases, but also the melting point of the alloy decreases excessively, making atomization and HIP operations difficult. Considering these points, a more preferable content of B is 1 to 2%.

Cr: 10-40%, Cr forms borides and carbides with B and C, and is also dissolved in the Ni or Co matrix, and is an essential element for improving corrosion resistance and wear resistance, less than 10%. In this case, these effects are not effectively exhibited, and the nitric acid corrosion resistance is particularly poor. However, if it is too large, the toughness of the alloy will decrease, so it must be kept below 40%.

W: 10-30%, W forms borides and carbides with B and C and has the effect of increasing corrosion resistance and wear resistance, but 1
If it is less than 0%, these effects will not be fully exhibited. However, if it exceeds 30%, the alloy becomes excessively hard and its toughness deteriorates.

Cu: 0.5 to 3%, Cu is dissolved in the Ni or Co matrix and contributes to improving corrosion resistance.

If it is less than 0.5%, the effect will not be exhibited effectively, and - method 3
%, the toughness of the alloy deteriorates.

Remaining components: Either or both of Ni and Co. As a matrix component, the remaining components are Ni and C to ensure minimum corrosion resistance and wear resistance.

Either or both. In addition, unavoidable impurities accompanying the blending of Ni, Co and the above essential alloy components include P, S, and Fe.
, Mn, Aj+, etc. may be mixed in in trace amounts, but none of these will have any particular adverse effect as long as they are contained in impurity amounts (approximately 1% or less).

The inventor of the present invention conducted the following experiment in order to confirm the bonding state of the bonding layer of the alloy powder.

C: 0.95%, Si: 2.35%, B:
2.70%, W: 11.5%, Ni: 15.8%, Cr
:23.7%, and the balance was CO. Alloy powder A was produced by an Ar gas atomization method. This powder was classified into powders of 100 meshes (147 μm) or less.

On the other hand, as shown in Fig. 1, a mild steel capsule (thickness: 3 mm) 2 is placed around the base material (materials are of the following two types, ■ and ■) 1 with a gap of 9.5 m + a. The powder filling port 3 is provided on the upper surface side, and the base material l is provided on the lower surface side.
It was attached by welding.

Base material ■: Stainless steel 5US304 (This is a comparative example,
(same material as before). As mentioned above, thermal spray coatings are porous and allow industrial water to penetrate into the base material, so conventionally it was necessary to use materials that do not rust. In order to investigate the bonding state of the solid phase diffusion bonding layer when such a material is used, the same material as the conventional one was used.

Base material ■: Carbon [5S41 (this example).

In the present invention, the film can be expected to have 100% density, and there is no problem of industrial water penetration, so although materials such as 5S41 are low grade, it is possible to use a material that is easy to process as the base material. This material was used for confirmation.

Then, while maintaining the inside of the capsule 2 at 10-' Torr, the alloy powder A mentioned above is completely filled into the gap of the capsule 2 from the powder filling port 3 under the same vacuum of <10-5 Torr, and then the powder filling port 3 is filled with the alloy powder A. was hermetically sealed. This assembly was loaded into a HIP device and heated at 950°C and 1000 kg/
After the HIP treatment, the plunger 11 shown in FIG. 2 was finished by machining.

When this product was subjected to ultrasonic flaw detection, it was found that the plunger using SUS 304 as the base material
A crack was discovered at the interface between the coating layer 4 and the coating layer 4.

On the other hand, in the plunger using 3341 as the base material, no defects such as cracks were found in the flaw detection test, and the alloy powder layer 4 was 10
It had solidified with a density of 0% and was completely diffusion bonded to the base material.

To investigate the cause of this cracking, we repeated the test by changing the type of base material and found the following.

That is, when the base materials ■ to ■ consisting of the five types of materials shown in Table 2 and the above-mentioned alloy powder A as a coating layer were HIP-joined in the same manner as described above, the results were as follows: ■-8, ■-A, ■
In all combinations of -A, cracks occurred in the coating layer. On the other hand, ■-A.

In combination ①-A, sound bonding was obtained in both cases. As can be seen from Table 2, the reason for this is the difference in the average coefficient of linear expansion. Even if the bond is sufficiently bonded during high-temperature HTP, a large internal stress is generated during the cooling process after treatment due to the difference in the coefficient of expansion. It was found that the coating layer cracked. Therefore, in order to obtain a sound bond, it is necessary that the average expansion coefficients of the base material and the coating layer be as similar as possible.

Therefore, in order to determine to what extent the linear expansion coefficients of the two should be approximated, the following experiment was further conducted.

First, as shown in Table 3, alloy powders A to F having compositions within the above range were prepared. These are manufactured by adjusting the amount of each element within the above composition range so that the linear expansion coefficient can be changed intentionally.For example, the linear expansion coefficient can be easily reduced by reducing the amount of additive elements B and W. . To increase this, conversely, l of B and W may be increased.

These alloy powders A-F were bonded to the base material carbon steel (0.42% C) using HTP using the same method as described above, and when the bonded state was inspected after treatment, cracks were found in the C and H coating layers. was recognized. As mentioned above, the reason is that the difference between the coefficient of linear expansion (14, OX 10-"/'C) of the base material carbon steel was too large. From this result, it was found that in order to bond well with carbon steel, The coefficient of linear expansion of the powder alloy is 12~15X
It has been found that a range of 10-''/°C is necessary.

The inventor of the present invention also manufactured a plunger in order to actually incorporate it into a descaler in a rolling mill at a steel mill and conduct a durability test.

The manufacturing method is exactly the same as the first example, and the base material is carbon steel 5S.
41, and the final processed product shown in FIG. 2 was obtained. On the other hand, as a comparative example, the base material was 5US304, and the surface was coated with C:Q, 5%, B:
4%, Cr: 16%, Mo: 3%, Cu: 3%, Fe
: 2.5%, the balance being Ni, was coated by thermal spraying to a layer thickness of 1IIN, and after surface polishing, the outer diameter was finished to be the same as that shown in Fig. 2. Each of these plungers is loaded into a plunger pump, and the factory circulating water is brought to a pressure of 200
Kg/d, and the plunger speed was 1.5 tg/sec.

When continuous operation was continued in an actual rolling mill, the diameter of the plunger in the comparative example decreased to zero after 5 months.
It wore out by 6 mm and reached the end of its lifespan, so I had to replace it with a new one.

On the other hand, the plunger of the present invention, which is made by bonding corrosion-resistant and wear-resistant alloy powder to carbon steel by HIP, has an extremely long life, reaching 0.6 vw of wear after 24 months of continuous use. became.

Although the present invention is highly effective as a plunger for a pump for generating high-pressure water, it can be fully assumed that the concept of the present invention can be applied to other sliding parts as corrosion-resistant and wear-resistant products.

〔Effect of the invention〕

As described above, according to the plunger of the high-pressure water generation pump according to the present invention, the plunger core material is made of carbon steel,
The surface of this core material has a linear expansion coefficient of 12 at 20 to 600°C.
~15×10−b/′c for Ni,C.

By forming a solid phase diffusion bonding layer of alloy powder mainly composed of one or both of The benefits are extremely significant when considering replacement work, and whereas conventionally it was necessary to use stainless steel, which is an expensive and difficult-to-cut material, the present invention uses carbon steel, which is inexpensive and has good workability. This has the effect of making it possible to significantly reduce costs.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining the first embodiment of the present invention, and FIG. 1 is a sectional view for explaining the HIP operation,
FIG. 2 is a sectional view showing the final processed product, and FIG. 3 is a schematic diagram of a general high pressure generation pump. In the figure, l is the base material (core material), 4 is the solid phase diffusion bonding layer,
11 is a plunger, 12 is a cylinder, and 13 is a packing. Patent applicant: Kobe Steel, Ltd. Representative: Patent attorney: Tsutomu Shimofu Figure 2: Figure 3

Claims (1)

[Claims] (1) In the plunger of a high-pressure water generation pump that slides while contacting a high-hardness packing placed on the inner circumference of the cylinder, the core material of the plunger is made of carbon steel, and the surface of the core material has linear expansion. The coefficient is 12 in the temperature range of 20-600℃
A plunger for a pump for high-pressure water generation, characterized in that a solid phase diffusion bonding layer of alloy powder containing one or both of Ni and Co as a main component is formed with a temperature of ~15×10^-^6/°C.