JPS5819219B2 - corrosion test equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION An example of a conventional rotary bending corrosion fatigue testing apparatus is shown in FIG. 1, and examples of a corrosive liquid tank are shown in FIGS. 2 and 3.

In FIG. 1, a corrosive liquid 2 stored in an upper tank 1 is led to a corrosive liquid bath 4 through a pipe 3, and a test piece 5 is immersed in the corrosive liquid.

The corrosive liquid discharged from the corrosive liquid tank 4 is stored in the lower tank 6,
Thereafter, it is sent to the upper tank 1 by a pump 7 and circulated.

2 and 3 show the detailed structure of one example of the corrosive liquid tank 4 shown in FIG. 1, with reference numeral 8 indicating a cylindrical corrosive liquid tank body, 9 an inlet for the corrosive liquid provided at its lower part, Reference numeral 10 denotes an outlet for the corrosive liquid provided at the upper part thereof; 11 denotes a seal fixing plate fixed to both sides of the test tank body 80 by screws 12; 13 denotes a seal mounting part provided on both sides of the corrosive liquid tank main body 80; 14 is a sealing member attached to the corrosive liquid tank body 8 by the seal fixing plate 11 and the seal attachment part 13; 15 is a buffer spring for supporting the corrosive liquid tank main body 8 on the testing machine 16; Seal the piece 17 between the fixing plate 11 and the corrosive liquid tank body 8
After inserting the sealing member 14 into the hole provided in the test piece 17 and bringing it into contact with the test piece 17, the test piece 17 is rotated to apply a load, while the corrosive liquid is passed through the inlet 9 → inside the corrosive liquid tank main body 8 → the outlet 10 It is designed to circulate.

However, in the above-mentioned corrosion fatigue testing apparatus, the Q tank 1 and the lower tank 6 are open to the atmosphere, and the sealing member 14 of the corrosive liquid tank 4 also completely prevents corrosive sludge from leaking from the inside of the corrosive liquid tank main body 8 to the outside. Therefore, it was impossible to conduct a fatigue test with a reduced amount of dissolved oxygen in the corrosive solution.

Generally, one of the items to consider when designing a turbine is the issue of fatigue design for blade vibration.

Previously, the fatigue strength in the atmosphere was used as the fatigue strength of different materials used in fatigue design, but the environment of the actual machine was salt, salt, etc.
It may be in a wet steam state containing impurities such as caustic soda, and it is considered necessary to perform fatigue design based on the fatigue strength in salt water, caustic soda solution, etc.

In the actual turbine environment, the dissolved oxygen concentration, which has a large effect on corrosion fatigue behavior, is close to zero, but in normal fatigue tests, the corrosive atmosphere is in direct contact with the atmosphere, so dissolved oxygen is reduced. Since it is impossible to determine the corrosion fatigue strength in a solution with reduced dissolved oxygen using a conventional fatigue test device, there is a need for a corrosion test device that can easily obtain the fatigue strength in a solution with reduced dissolved oxygen. Ta.

The present invention was proposed in response to the above-mentioned needs, and includes a corrosive liquid tank in which a test piece is exposed to a corrosive liquid, a liquid tank that supplies the corrosive liquid to the corrosive liquid tank, and a space between the liquid tank and the corrosive liquid tank. In a corrosion testing apparatus having a circulation mechanism for circulating a corrosive liquid, the liquid tank is made of an airtight structure, and nitrogen gas is added to the corrosive liquid in the pre-liquid raising tank in order to reduce the amount of dissolved oxygen in the corrosive liquid. a bubbling mechanism for bubbling the corrosive liquid, an isolation chamber filled with nitrogen gas to isolate the corrosive liquid tank from the atmosphere, and an isolation chamber installed in the corrosive liquid circulation piping system to collect the corrosive liquid in order to detect the dissolved oxygen concentration. By installing a collection bottle, there is no need for a large amount of corrosive liquid as in the case of conventional methods in which the corrosive liquid collection bottle is placed outside the piping system, and the amount of liquid required for concentration measurement can be reduced, and the amount of dissolved liquid can be reduced. It is an object of the present invention to provide a corrosion testing device capable of obtaining a corrosive solution with an oxygen concentration and determining fatigue strength in a state where the dissolved oxygen concentration is reduced.

Embodiments of the drawings will be described below. FIG. 4 shows an embodiment of the corrosion testing apparatus of the present invention, and FIG. 5 shows an example of a nitrogen gas-filled container used in the apparatus.

In FIG. 4, reference numeral 18 denotes a liquid storage tank having an airtight structure for storing a corrosive liquid 19, and nitrogen gas sent from a nitrogen gas cylinder 20 is bubbled through a diffuser pipe 21 inserted into the liquid storage tank 18. It is supposed to be done.

Further, the corrosive liquid 19 exits from the outlet 22 at the bottom of the liquid storage tank 18, passes through the pipe 23, and is sent to the corrosive liquid tank 25 by the pump 24, so that the test piece 26 is immersed in the corrosive liquid.

The corrosive liquid tank 25 is covered with a container 2T filled with nitrogen gas to prevent the corrosive liquid from coming into contact with the atmosphere.

The corrosive liquid discharged from the corrosive liquid tank 25 passes through a collection bottle 28 at 28 b used to measure the dissolved oxygen concentration, and is returned to the liquid storage tank 18 through an inlet 29 at the top of the liquid storage tank 18 via a pipe 30. .

Also, the nitrogen gas used here is the nitrogen gas cylinder 20.
The nitrogen gas is then supplied to each device via a nitrogen gas pipe 31, and is discharged into the atmosphere through an air intrusion prevention container 33 filled with drained water 32.

34 is piping when the corrosive liquid tank 25 is not passed through, 35a, 3
5b.

35c t 35a, 35e t 35f are cocks used to cut off the flow of the corrosive liquid.

In addition, in this device, in order to completely prevent the corrosive liquid in the system from coming into contact with the atmosphere, a liquid storage tank 18, a cock 35a,
35b, 35c, 35a, 35e.

35f, the corrosive liquid collection bottles 28a and 28b are made of glass,
The piping 23, 30, 31, 34 uses vacuum rubber tubes, the pump 24 uses a diaphragm type, and the corrosive liquid tank 2
5. The nitrogen glass enclosure 27 and the like are made of acrylic.

FIG. 5 shows the details of the nitrogen gas filled container 27 attached to the cantilever rotary bending fatigue tester.
is a corrosive liquid bath, and the test piece 26 is immersed in the corrosive liquid 36.

Further, the sealing member 37 prevents significant leakage of the corrosive liquid 36 from the inside to the outside, and the container 27 seals nitrogen gas around the corrosive liquid tank 25 to prevent the corrosive liquid 36 from coming into contact with the atmosphere. I'm here.

The nitrogen gas-filled container 27 is divided into two parts to allow the test piece to be attached to and removed from the test machine, and is sealed with a screw 38.

The test piece 26 is attached to a test piece rotating shaft 39, and the test piece rotating shaft 39 is attached to a fixture 41 via a bearing 40.

Also, inside and outside of the nitrogen gas filled container 27, an oil seal 4 is installed between the fixing jig 41 and the test piece rotating shaft 39.
2.

43 is a weight for applying a load to the test piece 26;
The highly flexible bellows 44 (made of rubber, for example) prevents contact between the nitrogen gas and the outside atmosphere, and also allows the weight mount 45 to move without any hindrance when a load is applied.

Next, an explanation will be given of the operation of each apparatus when a fatigue test is carried out in a state where the dissolved oxygen concentration in the corrosive liquid is reduced using the corrosion test apparatus according to the embodiment of the present invention described above.

. First, in FIG. 4, before putting the corrosive liquid 19 into the liquid storage tank 18, the air in the corrosive liquid tank 25 and nitrogen gas enclosure 27 is replaced with nitrogen gas in the nitrogen cylinder 20.
The cocks 35at35b are closed to prevent air from entering the corrosive liquid tank 25.

This is because the test piece 26 is completely immersed in a corrosive solution with a low oxygen concentration from the beginning.

Next, the corrosive liquid is transferred to the liquid storage tank 18, the pipes 23, 30, 34,
The pump 24, corrosive liquid collection bottles 28a, 28b, etc. are filled, and the liquid storage tank 18 is circulated by the pump 24.
Nitrogen gas is bubbled through the diffuser tube 21 inserted into the corrosive solution to reduce the dissolved oxygen concentration in the corrosive solution.

In this way, all the corrosive liquid in the piping system can be made to have the same dissolved oxygen concentration.

After reducing the dissolved oxygen concentration, the cocks 35a and 35b
The test piece 26 is immersed in a corrosive solution with a low dissolved oxygen concentration, and the fatigue test is started.

When measuring the dissolved oxygen concentration, the cocks 35c and 35d are closed, the collection bottle 28a is taken out, and the dissolved oxygen concentration is measured by a colorimetric method such as the Insu-Carmine method.

Furthermore, the dissolved oxygen concentration can be similarly measured using another collection bottle 28b, and the number of measurements can be increased by increasing the number of collection bottles installed.

The corrosive liquid in the liquid storage tank 18 is always in contact with nitrogen gas, and the corrosive liquid tank 25 is also equipped with a nitrogen gas-filled container 27 having the structure shown in FIG. Since these nitrogen gases are in contact with each other and are completely blocked from the atmosphere by the atmosphere intrusion prevention container 33, it is possible to perform a fatigue test in a corrosive liquid with a reduced concentration of dissolved oxygen.

The nitrogen gas filled container 27 shown in FIG. 5 is installed in a cantilever type rotating bending fatigue tester, but by installing bearings 40, oil seals 42, etc. on both sides of the test piece, a four-point supported rotating The corrosion testing device of the present invention can also be attached to a bending fatigue tester or a tension-compression fatigue tester.

FIG. 6 shows the results of a fatigue test on 13 chrome stainless steel, which is commonly used as a material for turbine blades.

In Figure 6, X is the result of a fatigue test in the atmosphere that is not affected by a corrosive atmosphere, Y is the result of a fatigue test in 3% saline at room temperature with a conventional test device open to the atmosphere, and 2 is the result of this test. Low dissolved oxygen concentration state (30
Fatigue test results in 3% saline at room temperature at >ppb.

In the environment of an actual turbine, the dissolved oxygen concentration is close to zero, but in a saline water fatigue test that is open to the atmosphere, the amount of dissolved oxygen was 6 ppm, so it is difficult to say that it reproduces the environment of an actual turbine.

According to the hexagonal corrosion test apparatus of the present invention, the amount of dissolved oxygen can be reduced to 30
It has become possible to reduce the corrosion stress to ppb (0.03 ppm), and it has become possible to conduct corrosion fatigue tests close to the actual machine environment.

Also, the fatigue strength X of 13 chrome stainless steel in the atmosphere is 4.
1 kg/-, and in a 3% saline solution (room temperature) exposed to the atmosphere, it becomes 29 ky/-, which shows a decrease in strength of about 30%.

On the other hand, in a 3% saline solution with a low dissolved oxygen concentration close to the actual environment, the fatigue strength is 34 kg/ma, which is 17% higher than the fatigue strength in the atmosphere.
The results showed that the fatigue strength was slightly improved compared to the case where it was exposed to the atmosphere, but it was not comparable to the fatigue strength in the atmosphere.

By using the corrosion testing apparatus of the present invention, it is possible to accurately determine the fatigue strength required when designing the fatigue strength of turbine blades in consideration of environmental conditions.
This makes it possible to contribute to improving the reliability of turbine blade design.

As explained in detail above, the present invention uses a bubbling mechanism to bubble nitrogen gas into the corrosive liquid in the liquid tank with an airtight structure, thereby reducing the amount of dissolved oxygen in the corrosive liquid. Corrosive liquid is easily obtained.

In addition, in order to isolate the corrosive liquid tank from the atmosphere, we have installed an isolation chamber filled with nitrogen gas, which completely prevents contact between the corrosive liquid and the atmosphere, and improves fatigue strength even when the dissolved oxygen concentration is reduced. can be easily determined.

The present invention also includes a collection bottle installed in the corrosive liquid circulation piping system to collect the corrosive liquid in order to detect the dissolved oxygen concentration, so the amount of corrosive liquid required for concentration measurement is much smaller than in the past. In addition, it is possible to take measurements several times during the test, and
It is possible to measure the dissolved oxygen concentration in the corrosive liquid under the same conditions as those around the test piece.

Note that the present invention can be applied to corrosion fatigue testing equipment and various environmental testing equipment.

[Brief explanation of the drawing]

Fig. 1 is a flow sheet showing an example of a conventional corrosion test device, Fig. 2 is a detailed side sectional view of the corrosive liquid tank in Fig. 1, Fig. 3 is a sectional view taken along line A-A in Fig. 2, and Fig. The figure is a flow sheet of a corrosion test device showing an embodiment of the present invention, Figure 5 is a detailed sectional view of the nitrogen gas-filled container in Figure 4, and Figure 6 is a line showing fatigue test results for 13 chrome stainless steel. It is a diagram. Explanation of main parts of the figure, 18...Liquid storage tank, 1
9...Corrosion liquid, 20...Nitrogen gas cylinder, 21...Diffuser pipe, 25...Corrosion liquid tank, 26...Test piece , 27... Nitrogen gas sealed container, 28a, 28b... Collection bottle, 23
, 30, 34... Piping, 31... Nitrogen gas piping.

Claims (1)

[Claims] 1. Corrosion testing equipment that has a corrosive liquid tank in which a test piece is exposed to a corrosive liquid, a liquid tank that supplies corrosive liquid to the corrosive liquid tank, and a circulation mechanism that circulates the corrosive liquid between the liquid tank and the corrosive liquid tank. The liquid tank has an airtight structure, a bubbling mechanism for bubbling nitrogen gas into the corrosive liquid in the liquid tank to reduce the amount of dissolved oxygen in the corrosive liquid, and a bubbling mechanism for isolating the corrosive liquid tank from the atmosphere. 1. A corrosion testing device comprising: an isolation chamber in which nitrogen gas is sealed; and a collection bottle installed in the corrosive liquid circulation piping system to collect the corrosive liquid in order to detect dissolved oxygen concentration.