JPS60184902A - Manufacturing method for turbine rotor - Google Patents

Abstract

PURPOSE:To simply improve durability by providing a thrust collar on the outer periphery of a rotor shaft made of high chrome alloy steel and welding, through explosion, a facing collar made of low chrome alloy steel to faces of contact between the thrust collar and a thrust bearing. CONSTITUTION:A thrust collar 5 supporting a thrust bearing is provided on the outer periphery of a rotor shaft 2, made of high chrome alloy steel, by cutting it in one body with said shaft. Then facing collars 8, 8' made of low chrome alloy steel with high thermal conductivity are fixed on both faces of contact between the thrust collar 5 and the thrust bearing through a lubricating oil film, and gun powder is laid outside said collars to join them by means of an explosion welding method. Subsequently, the face of contact between the facing collars 8, 8' and the thrust bearing through the oil film is formed by means of mechanical processing, and a turbine rotor with a thrust collar made of low chrome alloy steel is completed. The turbine rotor with excellent durability can be simply manufactured by this method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of manufacturing a turbine rotor that is easy to manufacture and has a long life.

[Technical background of the invention and its problems]

Conventionally, high chromium alloy steel containing 3 to 15% by weight of chromium has been used as a material constituting the rotor of a turbine such as a steam turbine.

However, in such a turbine rotor,
Although it has excellent mechanical strength at high temperatures, it has the disadvantage that the thrust collar, which is in contact with the thrust bearing through a lubricating oil film, is susceptible to scratches in the form of many sharp grooves running in the circumferential direction called galling. Generally, the above-mentioned galling is thought to occur due to the following reasons.

In other words, if the oil film is broken by a foreign object such as welding spatter present in the lubricating oil and localized frictional heat is generated due to direct contact, if the thermal conductivity of the rotor material is low, the heat will accumulate internally and cause a local emergency. It is thought that this causes galling damage due to foreign matter biting into the metal of the thrust bearing and peeling off the portion of the thrust collar.

The pieces of the thrust collar that have been removed become wedged in the bearing metal and become a source of galling, causing further damage and damage to the bearing and journal in a short period of time.

However, the degree of occurrence of such galling damage and the degree of damage are proportional to the average surface pressure of the thrust bearing (the load acting on the thrust bearing divided by the thrust area).
Since it is inversely proportional to the thermal conductivity of the rotor material, damage to the thrust collar is likely to occur in a rotor made of high chromium alloy steel with a low chromium content and low heat conductivity.

In order to solve this problem, as shown in Fig. 1, the thrust collar 1 is formed from a low chromium alloy steel containing 1 to 2% by weight of chromium, which is a material that is unlikely to cause galling. A method has been adopted in which a turbine rotor is manufactured by shrink-fitting this onto a rotor shaft 2 made of high chromium alloy steel.

However, in this method, the large-diameter flange portion 8 of the coupling at the end of the rotor shaft 2 becomes an obstacle during shrink-fitting, so this seven-rank portion 8 must also have a shrink-fit structure.

When shrink-fitting the flange portion 8, since this portion is subject to a large centrifugal force during rotation, it is necessary to provide a large shrink-fitting allowance from the viewpoint of preventing slippage.
Furthermore, in addition to increasing the tensile stress in the tangential direction, it is necessary to drive the axial key 4 in order to increase the frictional force of the shrink-fitted surfaces and transmit a large torque.

Therefore, this method not only increases the number of man-hours required for manufacturing, but also tends to cause cracks due to the fretting phenomenon of the flange shrink-fitting part and stress concentration on a part of the keyway corner, and in the worst case, This had the disadvantage that it led to cracks occurring in the shaft portion of the turbine rotor.

Fretting is caused by the repeated application of bending and torsional forces to areas of the shrink-fitted part with relatively low surface pressure, such as near both ends of the coupling, causing friction between the coupling and journal on the shrink-fitted surfaces. This is a phenomenon that overcomes the force and causes relative movement, resulting in fatigue cracks in the surface layer.

Another example of the conventional method will be explained using FIG. 2. A thrust collar 5 is integrally machined on the outer periphery of the turbine rotor shaft 2 made of high chromium alloy steel, and a single collar 6.6' made of low chromium alloy steel is fixed to the surface in contact with the thrust bearing with fixing bolts 7°7'. This is the way to do it.

However, according to this method, since only the bolts are fixed, the fixing force is very weak, and a gap is created between the thrust collar 5 and the facing collar 6, so that it cannot withstand long-term use.

[Purpose of the invention]

The present invention has been made in order to eliminate such drawbacks, and an object of the present invention is to provide a method for manufacturing a turbine rotor that requires fewer man-hours for manufacturing and that can be used for a long time.

[Summary of the invention]

The present invention provides a rotor shaft outer periphery made of high chromium alloy steel;
This method of manufacturing a turbine rotor is characterized in that a thrust collar that supports a thrust bearing is machined integrally, a bulge is provided, and the thrust collar is prefabricated.

[Embodiments of the invention]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to an embodiment shown in the drawings.

As shown in FIG. 3, the turbine rotor of the present invention has a substantially cylindrical thrust collar 5 formed integrally with the outer periphery of a rotor shaft 2 made of mechanically strong cylindrical chromium alloy steel.
Facing collars 8 and 8' made of low chromium alloy steel with high thermal conductivity are fixed to both sides of the thrust collar 5 which are in contact with the thrust bearing through a lubricating oil film.

In order to provide the facing collars 8 and 8', first, a nearly cylindrical thrust collar 5 is cut out from the high chromium alloy rotor shaft 2 and finished, and then both sides of the thrust collar 5 are machined. Facing color 8 on the surface,
8' is fixed, explosive is placed on the outside, and p-joint is made by explosive welding. After joining, the surfaces of facing collars 8 and 8' that contact the thrust bearings via an oil film are formed by machining.
Complete the turbine rotor with a thrust collar made of low chromium alloy steel. Explosive welding produces diffusion over the entire surface of the joint and has an extremely strong bonding force, making it an extremely excellent method for fixing low chromium alloy steel thrust collars.

Explosion welding is a method of joining that utilizes the powerful energy generated when gunpowder explodes. That is, the explosive force of the gunpowder brings them into close contact, and at the same time, the metal jet that opens at that time causes diffusion to occur at the bonding interface between the two.

〔Effect of the invention〕

In the turbine rotor of the present invention constructed as described above, the part of the thrust collar that contacts the thrust bearing is made of low chromium alloy steel with high thermal conductivity and is damaged, and the part made of high chromium alloy steel is used as the thrust bearing. Because there is no direct contact with the thrust surface, there is little chance of galling damage to the thrust surface.

In addition, compared to conventional thrust collars and couplings that have a shrink-fit structure, they are not only easier to fabricate, but are also highly reliable and can withstand long-term use.

In addition, compared to the conventional method of fixing 7 Acing collars by bolting, since the Facing collars are joined by explosive welding, diffusion occurs over the entire joint surface, and the adhesion is extremely strong, making it durable for long-term use. .

It has the following effects.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a conventional turbine rotor, and FIG. 2 is a diagram of another conventional turbine rotor from that shown in FIG. FIG. 3 is an enlarged longitudinal cross-sectional view of a portion of the thrust collar in the turbine rotor of the present invention.

Claims (1)

[Claims] A thrust collar that supports the thrust bearing is machined integrally on the outer circumference of the rotor shaft made of high chromium alloy steel.
A method for manufacturing a turbine rotor characterized by the thrust color of the thrust color.