JPS5968599A - Centrifugal impeller of slurry pump - Google Patents

Abstract

PURPOSE:To improve the abrasion-resisting property of an impeller by a method wherein after coating the inside suface of a shroud and an impeller, the body of the impeller and the foreside shroud are connected, and the inside surface of the flowing passage is coated with hardening materials. CONSTITUTION:Surface hardening layers, which have very excellent wear resistance, are formed by flame-sphraying cemented carbide such as tungsten carbide, or hardening materials such as coating agent consisting of ceramic like alumina at the surface of a blade 3c, and on the inside surface of both the backside shroud 3b and the foreside shroud 4. Then after finishing the flame-spraying the body 3 and the foreside shroud 4 are joined together, and the inside of the part 3d of the foreside shroud is joined to the body 3 by welding, and the joint area by welding is further covered by the flame-spraying of hardening materials. As a result of this method, the flow surface inside of the impeller can be protected by the coating of hardening materials, thereby enabling to markedly improve the abrasion-resisting property of the impeller.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a centrifugal pump, and particularly to an impeller used in a centrifugal pump for slurry, etc.

[Prior art]

Conventionally, the impellers of pumps such as slurry pumps that handle highly abrasive fluids have been made of materials with relatively high wear resistance, such as high chromium steel. However, when an impeller is rotated at a high speed to obtain a high head, the impeller wears rapidly, resulting in a short life span and high maintenance costs.

In order to improve the wear resistance of this impeller,
Recently, a method of coating the surface of an oven impeller 1 by thermally spraying a hardening material such as ceramic on the water surface of the oven impeller 1 as shown in the figure, that is, a method of providing a hardened surface layer 2, has been implemented recently. However, this method is limited to open impellers without a front shroud for small impellers due to the space required for thermal spraying work, and it is difficult to apply this method to the flowing water section of a closed impeller. However, in high-pressure slurry pumps that require improved wear resistance, it is necessary to use a closed impeller to reduce leakage loss and prevent chip cavitation, and there is a problem in that the surface cannot be coated with a hardening material.

Recently, there has been an idea to make the entire insert for the impeller used in a centrifugal pump for coal slurry from a material with excellent wear resistance, and to form the base and cover plate from an easy-to-process material such as steel and weld them together. Proposed. (Japanese Patent Application Laid-Open No. 56-66486 "Composite Centrifugal Impeller for Rally Pump") However, in one method, it is not easy to manufacture and process the insert, and it is very expensive. However, although the hard materials used as inserts are generally very hard, they are brittle.
When the blade vibrates due to water pressure pulsation or the like and is subjected to a bending load, there is a problem in that it is easily damaged.

[Purpose of the invention]

The object of the present invention is to solve the above problems and provide a centrifugal impeller for a slurry pump that is inexpensive, has excellent wear resistance, and has excellent mechanical strength.

[Summary of the invention]

That is, in the present invention, as an impeller for a centrifugal pump, an impeller main body consisting of a hub, a rear shroud, a blade, and a part of an annular front shroud, and the remaining front shroud are made separately, and the flow of the impeller is After the inner surface of the shroud forming the passageway and the impeller are surface-coated with a hardened substance, the impeller main body and the front shroud are joined. This makes it possible to coat the internal flow path of the closed impeller with a hardened substance.
A centrifugal impeller that is inexpensive and has excellent wear resistance can be obtained.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the accompanying drawings FIGS. 3 to 6.

FIG. 3 shows one embodiment of the present invention, in which the hub 3a of the impeller,
The impeller body 3 consisting of a rear shroud 3b, blades 3c, and a portion 3d of an annular front shroud and the remaining nine front shrouds 4 are made as separate pieces. The main body 3 and the front shroud are made of a material that is easy to manufacture, can be welded, and has a certain degree of wear resistance, such as cast steel or alloy cast steel.

Then, a hardening material is sprayed on the water flowing surfaces of these pieces, that is, the blade surfaces, the inner surfaces of the rear shroud, and the front shroud, in the same manner as in FIG. 1, to coat the surfaces. This hardening material can be a coating agent made of cemented carbide such as tungsten carbide or titanium carbide, or a ceramic such as silicon carbide, silicon nitride, or alumina. can be obtained. The work of thermally spraying the hardening material can be easily carried out in the same manner as in FIG. 1, since the main body 3 and front shroud 4 of the impeller are separate pieces. After the thermal spraying is completed, the main body 3 and the front shroud 4 are assembled as shown in FIG. That is, portion E in FIG. 3 is welded and joined. The weld joint is then further coated by thermal spraying with a hardening material.

As described above, it is possible to obtain a closed impeller in which the flowing water surface inside the impeller is protected by a hardening substance.

Furthermore, if the liquid contact parts other than the flowing water surface inside the impeller, that is, the outer surfaces of both shrouds are also coated with a hardening material, an impeller with excellent wear resistance as a whole can be obtained.

In the present invention, a part 3d of the annular front shroud is manufactured integrally with a part of the impeller body, and this annular part 3d and the front shroud 4 are joined together. This joint surface is processed to be concentric with the inner diameter of the impeller hub 3a. Therefore, the main body 3 and the front shroud 4 can be joined efficiently and accurately.

Figures 5 and 6 show another embodiment, in which the impeller main body 3 and the front shroud 4 are not welded all around, but are screwed together, and spot welded at several points on the circumference of the threaded part. Do the following. According to this method, when the main body 3 and the front shroud 4 are joined together, multiple passes of heat are not applied to the impeller, so it is possible to prevent the coating layer, such as a ceramic coating, from cracking due to heat. After joining, the joint portion and the outer surface of the shroud are further coated with a hardening material in the same manner as in FIGS. 3 and 4.

〔Effect of the invention〕

Since the present invention is constructed as described above, it is possible to significantly improve the abrasion resistance of the flow path within the impeller, and to obtain a centrifugal impeller that is inexpensive and has excellent mechanical strength. It can be effectively used in pumps that require impellers with high wear resistance and durability.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a known impeller, and Figure 2 is A--A in Figure 1.
A' arrow view, FIG. 3 is a sectional view showing implementation ν1 of the present invention,
4 is a sectional view showing a state in which the impellers shown in FIG. 3 are combined; FIG. 5 is a sectional view showing an embodiment of the present invention; and FIG. It is a diagram. DESCRIPTION OF SYMBOLS 1... Open impeller, 2... Surface hardening layer by thermal spraying of a hardening substance, 3... Impeller main body, 3a... Hub,
3b... Rear shroud, 3c... Blade, 3d
...Part of the annular front shroud, 4...
Front shroud. 591 O 1 Eye A' 73 Mouthfulness z1 Power 7 O5171 ;tL Quotient 3 592-

Claims (1)

[Claims] 1. An impeller for a centrifugal pump, which is formed from an impeller main body consisting of a hub, a rear shroud, a blade, and a part of an annular front shroud, and the remaining front shroud. 1. A centrifugal impeller characterized in that the impeller main body and front shroud are joined after the inner surface of the shroud and the impeller surface that form the flow path are coated with a hardened substance. 2. The centrifugal impeller for a slurry pump according to claim 1, wherein the impeller body and front shroud are made of steel or alloy steel. 3. In the centrifugal impeller for a slurry pump according to claim 1, the hardening substance is tungsten.
A centrifugal impeller for a slurry pump characterized by being thermally sprayed with a surface treatment agent made of carbide, titanium carbide, or any cemented carbide. 4. A centrifugal slurry pump centrifugal impeller according to claim 1, characterized in that the hardening material is a ceramic treatment agent such as silicon carbide, silicon nitride, alumina, etc., which is thermally sprayed. impeller. 5. A centrifugal impeller for a slurry pump according to claim 1, wherein the impeller main body and the shroud are joined by welding. 6. The centrifugal impeller for a slurry pump according to claim 1, wherein the impeller body and the front shroud are screwed together and then joined by spot welding. 7. In the impeller for a slurry pump according to claim 1, after the impeller main body and the front shroud are bonded, the bonded portion, the outer surface of the shroud, etc. are further surface coated with a hardening substance, and the impeller is bonded to the impeller. A transparent impeller for slurry bombs whose entire surface is coated with the liquid part.