JPS60159117A - Method for restoring embrittled member by ultrasonic wave - Google Patents

Abstract

PURPOSE:To restore an embrittled member of a thermoelectric power plant, a chemical plant or a nuclear power plant to the initial function without requiring dismantlement by applying ultrasonic waves to the member embrittled by carbides or impurities precipitated and coagulated during heat treatment or use. CONSTITUTION:Ultrasonic waves of 5-500kHz are applied at room temp. - 600 deg.C to a low- or high-alloy material or a welded joint of the material embrittled by carbides or impurities precipitated and coagulated during heat treatment or use. The carbides or impurities on the grain boundaries are easily infiltrated and dispersed in the grains, so the embrittled metal can be restored to the initial function.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is applicable to thermal power, chemical and atomic couplants,
Suitable for restoring low-alloy steel, high-alloy steel and welded joints thereof that have been damaged by precipitated, agglomerated carbides and impurities due to long-term use, and their welded joints to their original functionality.Related to embrittlement recovery method using ultrasonic waves. .

[Background of the invention]

Firepower, chemical and atomic couplant components such as Gay 2
Chive, chemical plant reformer tube.

Thermal turbine parts and the like become damaged when used for a long period of time, so after a certain period of time, materials are replaced for each structural part or a new plant is constructed.

On the other hand, some parts for thermal power, chemical, and nuclear couplants are generally heat treated in factories or on-site to repair damaged parts.

However, conventional repair methods have the problem of requiring the entire plant or a portion of the plant to be cut and heat treated, making it difficult to apply in practice.

[Purpose of the invention]

The purpose of the present invention is to restore the original functions of low-alloy steel, high-alloy steel, and welded joints of these components damaged by use in thermal power, chemical, and nuclear power plants without dismantling them from the plant. The purpose of the present invention is to provide a method for recovering from embrittlement using ultrasonic waves.

[Summary of the invention]

The embrittlement recovery method using ultrasonic waves according to the present invention can embrittle low-alloy steel, high-alloy materials, and welded joints thereof that have become brittle (damaged) due to precipitated or agglomerated carbides or impurities during heat treatment and use. In the method for recovering the low alloy,
It is characterized by applying ultrasonic waves of 5 to 500 KHz to high alloy steel and welded joints thereof at a temperature range from room temperature to 600 C, thereby dispersing precipitated carbides and impurities and recovering damage.

The present invention is directed to the use of low-alloy steels, high-alloy steels, and welded joints thereof, which are used in particular for thermal power, chemical, and nuclear couplant components, due to long-term use. This is an innovative embrittlement recovery method that allows you to easily restore the original function on-site in the event of damage or embrittlement.

The technical idea underlying the present invention is to convert 100 volt alternating current electrical energy into high frequency waves, convert them into mechanical vibrations using an ultrasonic transducer, and then transmit the vibrations either directly or through a vibration medium such as a liquid. This causes the metal to propagate inside the embrittled metal, creating a tiny veneer inside the metal.

The minute cavities generated by the propagation of ultrasonic waves serve as dispersion paths for carbides, impurities, etc. precipitated at grain boundaries. Therefore, grain boundary carbides and impurities are easily penetrated into the grains and dispersed, so that the embrittled metal is restored to its original functionality.

In other words, the greatest feature of the present invention is that ultrasonic vibration energy causes local plastic deformation and elastic deformation inside the metal, which works to diffuse and disperse carbides at grain boundaries within the grains. , to disperse carbides and impurities at grain boundaries into the matrix.

In order to diffuse and disperse carbides, impurities, etc., it is necessary to apply ultrasonic waves that generate minute slips inside the metal. The frequency of ultrasonic waves necessary to recover from such embrittlement is preferably 5 to 500 KHz. At frequencies below 5 KHz, even if the metal is forced to vibrate, the vibrational energy is small, so the movement of atoms is small, and carbides and impurities are only slightly diffused and dispersed within the matrix.

On the other hand, if the frequency of the ultrasonic wave exceeds 1000 KHz, the vibration energy is too large to effectively diffuse and disperse carbides and impurities. Therefore, in order to diffuse and disperse carbides and impurities, 1. At least the ultrasonic frequency is 5-1000K
It needs to be in the Hz range.

In order to restore the damaged and brittle metal to its initial properties, it is preferable to limit the frequency of the ultrasonic waves to a range of 5 to 500 KHz.

Further, when applying ultrasonic waves to the material to be treated in the method of the present invention, it is desirable to maintain the temperature of the material to be treated within a range from room temperature to 6,000 ℃.

It is easy to use high temperatures to cause plastic deformation or elastic deformation in metals by ultrasonic waves to generate minute beads, and the higher the temperature, the more effective the movement of atoms.

However, if the temperature of the material to be treated exceeds 600C, there is a risk that the initial characteristics of the material to be treated may deteriorate.

In particular, since there is a risk of tempering embrittlement, it is necessary to suppress the tempering temperature to a temperature lower than the tempering temperature of each material to be treated. On the other hand, when setting an ultrasonic transducer in a material to be treated or a liquid medium, high temperatures may reduce the reliability of the ultrasonic device and may lead to failure.
The processing temperature must be at least 700C or lower.

Furthermore, if the processing temperature is below room temperature, the movement of atoms in the metal becomes inactive, and there is no necessity to suppress it below room temperature.

Therefore, the processing temperature when applying ultrasonic waves ranges from room temperature to 70°C.
0 G, preferably within the range from room temperature to 600C.

FIG. 1 is a diagram showing the relationship between the frequency of ultrasonic waves and the embrittlement recovery rate of 2-Cr-IMo steel.

Here, the embrittlement recovery rate (ψ) is the absorbed energy 11i (Eo) after heat embrittlement treatment for 500 hours at a temperature of 500t:'' for 2-Cr-IMO steel,
After heat embrittlement treatment for 500 hours at a temperature of 100C
The ratio of Et go to EO is expressed as a percentage as the absorbed energy value (Et) of a test piece subjected to 20 KHz ultrasonic waves for 100 hours in oil. That is, the embrittlement recovery rate (ψ) is expressed by the following equation.

Et　E.

ψ= −X 100 (匈 ・・・・・・・・・(1)
O Judging from this figure, the frequency for effectively recovering from embrittlement is 5 to 500 KHz.

In other words, if structural materials used in thermal power, chemical, or atomic couplants are damaged after being used for a long time, applying any vibrational energy within the ultrasonic frequency range of 5 to 500 KHz will make them brittle. recovery.

[Embodiments of the invention]

<Example 1> First, austenitic stainless steel <5 shown in Table 2
US304) was subjected to heat embrittlement treatment at 650 CX a, oooh r to precipitate carbides at ultra-high grain boundaries. Next, an embrittlement recovery method using ultrasound according to the present invention was carried out.

Table 1 Ultrasonic recovery treatment
The sample was immersed in 1:' oil, an ultrasonic transducer was inserted into the oil, and 45 KHz ultrasonic vibration was applied for 100 hours.

The result is the diagram shown in FIG.

FIGS. 2(A), 2(B), and 2(C) are micrographs of specimens of 5US304 before embrittlement treatment, after embrittlement treatment, and after ultrasonic treatment.

As is clear from the figure, the sample material before embrittlement treatment (Figure A) exhibits a normal austenite structure, and carbides and the like are not precipitated or aggregated at the austenite grain boundaries. 650
In the sample material (Figure B) that was heat-embrittled at t;X 3,000 h, austenite crystals were coarsened and
Carbides are precipitated and aggregated at grain boundaries. on the other hand,(
Figure 0) is a photomicrograph of the test material (Figure B) subjected to the present invention after heating and embrittlement, and it can be seen that the carbides at the austenite grain boundaries have disappeared.

<Example 2> Fig. 3 shows the effect of the present invention investigated using the low alloy steel (2-Or-1MO) shown in Table 2.

Table 2 Absorbed energy 1 after 500 hours of embrittlement treatment at 500C
! After embrittlement treatment for 500 hours with B and 5000, the test piece was immersed in 100C oil and subjected to ultrasonic vibration at 45KHz.
It shows the absorbed energy 1 direct C for 00 hours of addition.

As is clear from this figure, by applying ultrasonic vibration to the embrittled material, it has been revealed that it can be restored to a state close to that as received.

<Modifications/Applications of the Invention> The embrittlement recovery method using the ultrasonic vibration method of the present invention recovers embrittlement by applying mechanical vibration energy to the embrittled portion of the structure. It is also effective to attach the transducer to a structure and process it. Furthermore, it has been clarified that the present invention is useful not only for the dispersion effect of charcoal, compounds, etc., but also for the dispersion and disappearance of impurities, recovery from damage caused by fatigue creep, etc., and performance improvement.

It is effective for both ferrous and non-ferrous materials, although the effect may vary.

〔Effect of the invention〕

As is clear from the above explanation, the embrittlement recovery method using ultrasonic waves according to the present invention can be applied to materials such as low alloy steel and high alloy plane used in thermal power, chemical and atomic couplants, etc. It has the remarkable effect of dispersing carbides and impurities precipitated at grain boundaries that occur during welding, heat treatment, and use of welded joints, and recovering properties close to their initial properties.

[Brief explanation of the drawing]

This is a diagram showing the absorbed energy of stainless steel (SUS304) before and after embrittlement treatment using the method of the present invention and after implementing the method of the present invention. Agent Patent attorney Tatsuyuki Unuma No. 10 H2 Happy 20 Continuation of page 1 @ Inventor Mitsuo Kuriyama Hitachi City - In-house @ Inventor Utilization Masayuki Hitachi City! In-house [phase] Inventor Hiroyuki Doi In Hitachi City Koda Office 0Inventor Matsuyama Kei Hitachi City - In-house @ Inventor Ken Usami - Hitachi City Koda Office

Claims (1)

[Claims] 1. A method for recovering embrittlement of low-alloy and high-alloy materials and welded joints thereof, which have become embrittled due to carbides or impurities precipitated and agglomerated during heat treatment and use. Alloy materials and their welded joints from room temperature to 6
An embrittlement recovery method using ultrasonic waves, characterized in that precipitated carbides and impurities are dispersed and damage is recovered by applying ultrasonic waves of 5 to 500 KHz in a temperature range of 00C. 2. Regarding claim 1, an embrittlement recovery method using non-ultrasonic waves, characterized in that the ultrasonic waves are applied through a liquid. 3. In claim 1, low-alloy and high-alloy materials and welded joints thereof are used in thermal power generation, chemical plants,
Another example is an embrittlement recovery method that uses ultrasonic waves to detect damage during use as a structural material for atomic couplants.