JPS5853864B2 - Local gas analysis method in metals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for local gas analysis in metals.

Hydrogen present in metals has a significant negative effect on material properties such as hydrogen embrittlement.

Therefore, knowing the behavior of hydrogen in metals is extremely important for preventing destruction, and for this purpose, it is necessary to know the distribution of hydrogen not only near the metal surface but also inside the metal, that is, the local amount of hydrogen present.

Ion microanalyzers have been conventionally used for local elemental analysis in metals, but they have the following drawbacks.

The irradiated ion beam usually has an accelerating voltage of several to several tens of kilovolts.
The power of the ion current is small, ranging from several 101 LA, and in the case of hydrogen, since hydrogen ions generated as secondary ions are used for detection, the amount of signal obtained is small compared to the background, resulting in poor measurement accuracy.

Furthermore, because the power is low, only the area near the surface of the sample can be analyzed.

In recent years, a method has been proposed in which a laser is used to remelt a hole in the steel and the hydrogen contained therein is quantified using a mass spectrometer.

CV, D., Tarlinskii et al., Autom
atic Weld-ing 6, ppl 6
~18 (1974), or V, I, Yav
Oiski i, and other symposium reports.

(Metalurgiyas (1970)) However, since this method uses extremely short laser pulses, the melting time is short and the hydrogen contained in the melted zone cannot be completely extracted. It has the disadvantage that it can only be analyzed for about 1 hour at most.

In view of the current situation, the present inventors conducted various studies and found that by irradiating a target part of a metal sample with an electron beam as an irradiation beam in a high vacuum, the part can be irradiated for a short time. The gas diffusion rate in the molten metal is extremely fast compared to the gas diffusion rate in the solid metal, and the molten metal is vigorously stirred by boiling, so that the molten metal is rapidly stirred. It is possible to quickly extract the gas that is extracted into a vacuum container as neutral atoms and molecules, and because the amount of gas extracted is large, it is possible to quantify the gas with a gas analyzer with very high accuracy. On the other hand, it is possible to separate the gas extracted due to the temperature rise around the molten part by utilizing the difference in gas diffusion rate between the molten metal part and the solid metal part, and that it is possible to separate the gas extracted from the molten metal part by using the difference in gas diffusion rate between the molten metal part and the solid metal part. We found that it is possible to perform analysis using

The present invention was made based on these findings,
The present invention provides a method for analyzing gases locally present inside metals.

That is, the gist of the present invention is to irradiate a metal with a narrowly focused electron beam in a high vacuum, melt and stir the irradiated part over a depth of 17 nm or more, and remove the gas contained in the molten part. A local gas analysis method in metals, which is characterized by extracting them as neutral atoms) and molecules, analyzing them with a gas analyzer, and determining the gas content from predetermined electron beam irradiation conditions and the amount of molten metal. In this way, the locally existing gas at any depth 1 inside the metal can be extracted by changing the irradiation energy.

This enables highly accurate analysis without being influenced by background.

Gases to which the present invention applies refer to hydrogen, nitrogen, and oxygen.

The present invention will be explained in detail below based on the drawings.

FIG. 1 is an example of an apparatus for carrying out the invention for local gas analysis in metals.

After installing the metal sample 1 on the sample installation plate 4 through the sample entry/exit door 3 provided on the side of the vacuum container 2, the inside of the vacuum container 2 is evacuated by the vacuum pump 5, and the vacuum container 2 is evacuated to a high vacuum (1 to 5 x 10'
Torr).

At this time, in order to desorb gas such as water vapor adsorbed on the inner wall of the vacuum container and quickly obtain a high vacuum, the container is preferably heated for about 2 to 3 hours while being evacuated using a heater (not shown).

Even during cooling after heating is complete, the exhaust continues to reach a predetermined degree of vacuum.

When the temperature rise of the sample during heating or the dissipation of gas from the sample during evacuation is a problem, the sample entrance/exit door 3 is replaced by the vacuum container 2, which is not shown in the figure, and the inside of the preliminary evacuation chamber and the airtight sample entrance/exit door 3 are used. The mechanism may be configured such that after the vacuum container reaches a predetermined pressure, the sample in the preliminary evacuation chamber is placed on the sample placement plate by an airtight sample loading/unloading mechanism without breaking the vacuum.

Next, move the sample while observing the sample through a peephole (not shown).7. It is moved in the X and Y directions using γ to align the target analysis position with the optical axis of the electron beam.

Although not shown, the shaft 6 of the sample transfer handle 7.7'
．． It goes without saying that the portion where 6' penetrates the vacuum container 2 is constructed so that the vacuum cannot be broken.

Next, an electron beam emitted from an electron gun 9 controlled by a control system 8 is focused by an electromagnetic lens system 10 and irradiated onto the metal sample 1, melting and stirring the irradiated part in a short time to cause the molten part to melt. Extract the gases present as neutral atoms and molecules.

Thereafter, the extracted gas is analyzed by a gas analyzer 11 and recorded by a recorder 12.

As the gas analyzer 11, for example, a mass spectrometer or the like can be used.

Furthermore, after the gas has been extracted, a carrier gas may be introduced into the vacuum container to purge the interior of the vacuum container, and analysis may be performed using a gas chromatograph or the like.

(b) Electron beam irradiation) and analysis, the valve 13 between the vacuum container 2 and the vacuum pump 5 is opened and closed as necessary.

When local gas analysis is performed on one sample at two or more analysis positions, the sample is moved using the sample movement knob 7° γ and repeated analysis is performed.

Since the method of the present invention uses an electron beam, 1 to
A large output of IOK, W, can be selected, and therefore, the area of the analysis sample is 10-2 to 1 rtta, and the depth is 1 to 30 degrees.

Since stirring can be performed and there is no need to cut out a local part, it is possible to conduct analysis with almost no influence from cutting, processing, temperature rise, etc., and the local part can be
Since it is melted at high temperatures reaching over 0°C, it is possible to simultaneously extract not only the hydrogen contained in it, but also nitrogen and oxygen, which are present in the form of nitrides and oxides. It can be separated and quantified using a gas analyzer such as a mass spectrometer.

In the method of the present invention, it is possible to keep the amount of molten metal constant by keeping the electron beam irradiation conditions constant. It is possible to determine the gas content of .

In addition, as an analytical application, it can be applied to measuring the local gas amount in a metal material, the width of the sample surface, the distribution of gas amount in the length direction, and the distribution in the depth direction.

Hereinafter, the effects of the present invention will be explained in more detail with reference to Examples.

Example 1 In order to measure the gas distribution in the vicinity of the welded area using a low-hydrogen coated arc welding rod of steel type HT60 steel, a steel piece including the welded area was cut between Ioo x 100 mm x 4 Q, and the cut plane perpendicular to the welding direction was cut. Target analysis position (weld metal part/
After marking the 3 positions (heat affected zone and base metal part),
Using the apparatus shown in the figure and the procedure described above, it was installed on the sample installation plate 4 in the vacuum container 2, and the gas was extracted and analyzed.

The electron beam irradiation conditions used were acceleration voltage 60KV, beam current 50 mA, irradiation time 1 second.

The beam diameter was 1rnrIL, and the melting depth of the irradiated area was 21 degrees.

A mass spectrometer was used as the gas analyzer 11.

The amount of extracted gas was determined using a calibration curve determined in advance from the volume of the vacuum chamber, the pressure change in the vacuum chamber before and after beam irradiation, and the change in the mass spectrum obtained from the mass spectrometer.

Further, as a result of conversion using a calibration curve between the irradiation conditions and the amount of molten metal, it became clear that the local gas amount in each part was as shown in Table 1.

As shown in Table 1, according to the method of the present invention, information about the local gas content and its distribution in the vicinity of the weld can be obtained.

Example 2 To measure the gas distribution in the thickness direction of a thick plate, 10 steel pieces were
After cutting into 0 mm x 100 mm x 20 mm and marking appropriate analysis positions (2 locations A and B) on the rolled surface, place it on the sample installation plate 3 in the vacuum container 2, and perform the electronic test according to the procedure shown in Figure 1. The beam was irradiated with different melting depths in the thickness direction between A and B, and the gas was extracted and analyzed.

The irradiation conditions of the electron beam used were as shown in Table 2.

The results of gas extraction and analysis in the same manner as in Example 1 are shown in Table 3, and it was found that the amount of gas varied depending on the depth in the thickness direction.

By controlling the electron beam irradiation conditions in this manner, it is possible to analyze the gas contained in a portion of the sample at an arbitrary depth 1.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of an embodiment of an apparatus for carrying out the method of the present invention. DESCRIPTION OF SYMBOLS 1... Metal sample, 2... Vacuum container, 3... Sample entrance/exit door, 4... Sample installation plate, 5... Vacuum pump,
7, 7'... Sample movement bundle 8... Control system, 9-mount electron gun. 10... Electromagnetic lens system, 11... Gas analyzer, 12
...Recorder, 13...Valve.

Claims (1)

[Claims] 1. Irradiate the metal with a finely focused electron beam in a high vacuum, melt and stir the irradiated part over a depth of 1 inch or more, and extract the gas contained in the molten part as neutral atoms) and molecules. A local gas analysis method in a metal, which is characterized in that the gas content is determined using a predetermined electron beam irradiation condition and the amount of molten metal.