JPS60184443A - Forming method of journal part of shaft made of high chromium steel - Google Patents

Abstract

PURPOSE:To form a journal part which is scarcely damaged, by winding and attaching a heated low Cr steel member to the outside periphery of a journal corresponding part and forging and forming it from the outside, when forging a high Cr steel shaft. CONSTITUTION:A plate-shaped low Cr steel plate 3 heated to a forging temperature is made to adhere tightly and wound to the whole periphery of a journal corresponding part 2 of a shaft 1 for a high Cr steel turbine rotor, etc. This journal part 4 forming part is forged from the outside, the shaft 1 and the low Cr steel plate 3 are welded by pressure, and in this forging stage, it is formed so as to obtain a necessary journal diameter. According to this method, the low Cr steel plate 3 is coupled firmly to the shaft 1, and a shaft which is excellent in bearing characteristic is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for forming a journal portion of a shaft made of high chromium steel, particularly a method for forming a journal portion having improved bearing characteristics.

[Technical background of the invention and its key points]

Traditionally, materials for parts such as steam turbine rotor shafts that require both heat resistance and control strength (=
High chromium steel containing 3 to 15% by weight of chromium is used. However, when such high chromium steel is used as a shaft material for a turbine rotor, it has the disadvantage that it is susceptible to a large number of sharp groove-like scratches running in the circumferential direction called gallings on the rotor journal surface 1.

Such galling damage occurs when the oil film is broken by a foreign object such as welding spatter present in the lubricating oil, and frictional heat is generated locally due to direct contact.The frictional heat accumulates inside the shaft, causing a locally extremely high temperature. This softened part becomes a lump that is caused by the foreign matter being bitten (twisted) and torn off. Therefore, the degree of occurrence of such Goring damage and the degree of damage are based on the average of the bearing. The thermal conductivity of the shaft material is proportional to the surface pressure (and inversely proportional), so the journal damage described above is unlikely to occur in high chromium steel shafts, which have low thermal conductivity due to a high chromium content. be.

For these reasons, when high chromium steel is used as the shaft material for a turbine rotor, it is common practice to provide special treatment to the journal portion as described below. The diameter is smaller than the required journal diameter (= machined in advance,
The part is covered with a material that is difficult to generate, such as 1
1" coated with low chromium steel containing ~2% by weight of chromium (to give the desired journal diameter. Thus,
Even though the shaft itself is made of chromium steel, the bearing part has the properties of low chromium steel? Obtainable. The following methods are known as methods for keying with the above-mentioned low chromium steel.

(b) Apply fg welding using low chromium steel as a welding rod (
ol A cylindrical sleeve made of low chromium steel can be fired H The above sleeve? All of these methods of attaching the divided parts to the bath are convenient for construction; The problem is that it is difficult to adjust the coupling force between the shaft material and the shaft material. It is better to make the bond between the coating layers as strong as possible, but with the method described above, increasing the bond strength will increase the residual stress in the coating layer, which will lead to cracking and other abrasive defects. It is.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned points, and the present invention has been made by forming a coating layer provided on the shaft and the journal part of this shaft integrally (2). 4. [Summary of the Invention] The present invention provides a method for forming a journal portion of a high chromium steel shaft when a shaft is forged. This is a method of forming a journal portion of a shaft made of high chromium steel, which is characterized by wrapping a member made of low chromium 1Iliω and further forming the low chromium steel member from the outside.

[Embodiments of the invention]

Next, 42 embodiments of the present invention will be described.

FIG. 1 shows a four side view of a 12% chromium steel turbine rotor shaft in a drum state during a forging process. Large forged products such as turbine rotor shafts are usually
After going through the steps of adding 11% alloy components, making ingots, and forging, the general shape of the rotor shape (which can be called the rotor shape body) is formed.After that, heat treatment and cutting are performed to complete the turbine rotor, but the forging described here The process is the one after the above-mentioned ingot making. In this forging process, the steel ingot is sufficiently forged to destroy the sweet and weak casting structure (: porous defects are crimped). Then, when forging has progressed to a certain extent, a plate-shaped low-chromium steel plate 3 heated at % forging temperature (2) is placed around the entire circumference of the journal-corresponding part 2 of the shaft l, as shown in Figure 1. Wrap it around while making it overlap.In this way, the journal part 4 is formed, and after that,
Furthermore, (2) adding the journal part 4 from the outside (
Second, the shaft 1 and the low chromium steel plate 3 are crimped together and formed to have the journal diameter required in this forging step.

This figure shows how the chrome steel plate 3 is wrapped.

In this example, a single plate is used as the low chromium steel plate 3, but it is also possible to use a plate divided into multiple pieces, or a plate that is bent into a cylindrical shape from the beginning without being wrapped. May be used.

After the forming by forging is completed, heat treatment is performed to complete the shirt I as shown in FIG. 3 (two-machined shirt).

〔Effect of the invention〕

As described above, the present invention is effective when forging a shaft made of high chromium steel.
Since the journal part is formed by continuous forging, this method is suitable for large-sized forged products such as turbine rotor shafts.According to the present invention, the low chromium steel plate is Because it is double-pressured, it has the effect of being strong (two-coupled, making it possible to obtain shafts with improved bearing characteristics).

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a shaft for a 12% chromium ALU turbine rotor in a drum state during forging according to the present invention, FIG. Figure 3 shows the shirt tracker after machining to create a journal part according to the present invention (new note 1).
Figure 1. Agent: Patent attorney Noriyuki Chika (and 1 other person) Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] When forging a high chromium steel shaft, a plate-shaped low chromium steel member heated to the forging temperature of the shaft is wrapped around the outer periphery of the journal-equivalent part of the shaft (2), and a plate-shaped low chromium steel member heated to the forging temperature of the shaft is wrapped around the outside of the low chromium steel member (2). A method for forming a journal portion of a high chromium steel shaft, which is characterized by forging.