JPS60257360A - Method for analyzing oxygen in metal of titanium group or alloy thereof - Google Patents

Abstract

PURPOSE:To improve the accuracy of analyzing oxygen by allowing nickel of 7-17 times the weight of a sample for analysis of titanium to coexist in the sample then melting the sample. CONSTITUTION:Nickel of 7-17 times the weight of the sample for analysis of titanium is allowed to coexist in the sample in a method for analyzing quantitatively the oxygen in the titanium by heating and melting the titanium in an inert gaseous atmosphere with a graphite crucible at a prescribed temp. and bringing the oxygen therein into reaction with carbon monoxide. The nickel is made to coexist in the sample in the form of forming the same into a plate shape, enclosing the sample with the plate-shaped nickel and uniting the nickel and the sample. The adequate molten bath is thus formed in an early period and the extraction of gaseous carbon monoxide is accelerated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for analyzing oxygen contained in titanium group metals or alloys thereof, and in particular to a method for analyzing oxygen contained in titanium group metals or their alloys, in particular by melting the metal alloys at high temperature in an inert gas atmosphere to convert the oxygen contained therein into carbon. This invention relates to a method for quantifying oxygen by reacting it and extracting and analyzing it as carbon oxide.

As is well known, for example, oxygen contained as an impurity in titanium, like nitrogen, dissolves between the crystal lattices of titanium and has a significant effect on mechanical properties such as strength, and its content is determined by material standards. This is also clearly stated.

Therefore, while progress is desired in manufacturing technology for adjusting and controlling the oxygen content in titanium, oxygen analysis technology also plays an extremely important role.

Conventionally, oxygen analysis of titanium has generally been carried out by placing an analysis sample (hereinafter referred to as a sample) in a graphite crucible and heating and melting it at high temperature in an inert gas atmosphere such as He.

A method has been adopted in which carbon monoxide produced by the reaction of formula (1) below is extracted and then quantified by an infrared absorption method or a thermal conductivity method.

Note that the underlined symbol of an element in the same formula indicates that the same element is trapped in molten titanium as a solid solution.

c+o-co(-1)・・2・・・・・・・・・・・・
・・・・・・fl、1 By the way, titanium is strong in oxygen and parent wood, and it is difficult to completely extract it as carbon oxide.Furthermore, titanium has good wettability with graphite crucibles, so it is difficult to melt when melted. There is a problem that it penetrates into graphite, and in the end only 1% or less of the actual content can be extracted.

To solve these problems, a method was proposed in which platinum was melted at the same time as the titanium sample (platinum bath method).

It has been implemented.

In this platinum bath method, (1) the solubility of oxygen in molten platinum is low, and the reaction is accelerated during extraction. (2) Since the melting points of titanium and platinum are almost the same (titanium: 1670°C, platinum: 1773°C), it is easy to form a bath, and (
3) Analysis accuracy is high because the solubility of carbon in molten platinum is small and does not corrode the graphite crucible.

This method is currently recommended due to its excellent reproducibility.
Widely adopted.

However, this platinum bath method has the disadvantage of being economically disadvantageous because platinum is extremely expensive.

The present inventors have conducted extensive research and study to establish a new oxygen analysis method in titanium that eliminates the above drawbacks and has the same accuracy and reproducibility as the platinum bath method. Accuracy comparable to platinum bath method even when nickel is used in place of platinum under specific conditions.

It was confirmed that reproducibility could be obtained, and the present invention was completed.

That is, the present invention is a method in which titanium is dissolved in a graphite crucible under an inert gas atmosphere, oxygen in the titanium is extracted by reacting with carbon monoxide, and this is quantitatively analyzed. Hereinafter, the present invention will be explained in detail focusing on experimental results.

First, in the method of dissolving a titanium sample in the coexistence of nickel, nickel itself has low solubility in oxygen and nitrogen, similar to the aforementioned platinum, and is highly efficient in extracting oxygen as carbon monoxide, and there is less corrosion of the crucible. However, since the melting point of nickel (1455°C) is about 200°C lower than the melting point of titanium (1670°C), there is a problem that it is difficult to melt both at the same time using normal methods. The inventors believed that it would be impossible to put this nickel bath method into practical use unless this problem could be overcome, and by repeating various experiments with this point in mind, they were able to achieve the desired analytical precision and reproducibility. It was found that the form of the nickel added and the mixing ratio of the sample and nickel are extremely important factors.

In other words, the shape of nickel is high purity nickel (
An attempt was made to simultaneously introduce three types of graphite (with purity of 99% or higher) into a graphite crucible together with a sample: powder, wire, and plate.

Table 1 shows the standard sample (0; 0.187%) whose oxygen content was determined in advance using the platinum bath method. Nickel powder (20 meshes) and wire (sample wound with a diameter of 1 mm) and a plate (thickness Q, 4 mm wrapped around the sample) were placed in a crucible together with the sample at a mixing ratio of 10 times the weight of the sample and heated to 2700 to 3000°C.
The graph shows the results of quantifying the amount of oxygen in the sample by extracting the dissolved and produced carbon monoxide and using an infrared absorption method.

Note that the same table also shows the case where nickel was not added.

Table 1 Oxygen analysis results by nickel shape (extraction temperature 2700-3000℃) Table 2 Oxygen extraction completion time by nickel shape (extraction temperature 2700-3000℃) In addition, Table 2 is generated during the same dissolution 2 analysis These are the results of measuring the time taken to complete the extraction of carbon monoxide.

As is clear from these results, a sample with no nickel added (sample alone) is out of the question, but when the nickel used is in powder form, it is significantly lower than the standard value, the variation is quite large, and the linear Compared to powdered powder, the value is closer to the standard value and there is less variation, but it is still not completely satisfactory.

Furthermore, it can be seen that the extraction time is long and unstable in the case of powder and linear products.

In contrast, it has been found that the plate-shaped one has significantly higher precision than the powder or linear ones, has extremely small variations, and is stable with a short extraction time.

Therefore, when melting nickel together with the sample, use a plate-shaped plate and wrap the sample in one piece.The most preferable form is to quickly form an appropriate molten bath and promote the extraction of CO gas. it is conceivable that. When wrapping the sample with the nickel plate, there is a concern that air may enter if the sample is completely sealed, so a semi-sealed state with adequate ventilation holes is preferable. Specifically, it is recommended to use the pipe-shaped capsule shown in FIG. 1 in consideration of the simplicity of the analysis work. That is, the diameter of the rod-shaped sample (1),
Sample (1) is placed on a nickel pipe (2) made to match the length.
), insert the pipe a) and crimp both ends of the pipe to integrate the two. During this caulking, the ends of the tubes are not brought into close contact with each other, leaving vent holes (3) as shown in the diagram for venting gas.

Using such a capsule type allows for sample preparation,
It is easy to handle and has excellent workability, and at the same time, the sample (1
) Length e,) Length of the nickel pipe (2) e 2) ? eThere is an advantage that the blending ratio of both can be adjusted to an arbitrary value by changing it appropriately.

Next, using the characteristics of the capsule mentioned above regarding the mixing ratio of the sample and nickel, 0.17 samples were inserted into nickel pipes of various lengths, and the weight ratio of the sample and nickel was changed to conduct oxygen analysis of the same sample. The results obtained using the platinum bath method (○
) is shown in Figure 2. Note that the standard value of oxygen in the same sample is 760 ppm (dashed line in the figure). Also, the melting at this time.

The extraction temperature was 2700-3000°C.

From the same figure, it is clear that when nickel is added or coexisted, if the weight ratio of nickel to the sample is too small or too large, the accuracy decreases significantly compared to the platinum bath method.
Therefore, in order to ensure analytical accuracy comparable to that of the platinum bath method, it is important to maintain the blending ratio of nickel within an appropriate range. In particular, when the weight ratio of nickel to the sample is less than 7 or more than 17, it is clearly recognized that the weight ratio tends to be much lower than the standard value, and it is judged to be difficult in practice. In other words, the essential condition was to adjust the blending ratio of nickel to be within the range of 7 to 17 times the weight of the sample.

Table 3 summarizes the analysis results obtained using the method of the present invention and the results obtained using the platinum bath method for samples containing various values of oxygen that meet the mixing conditions of nickel, but the results of both are very different. It is found that the method of the present invention has analytical accuracy equivalent to that of the platinum bath method.

Furthermore, Table 4 analyzes and compares the blank values of nickel and platinum, and it can be seen that the oxygen value of nickel is equal to or lower than that of platinum, and that the influence of the blank is extremely small.

As mentioned above, when implementing the present invention in which nickel coexists and is dissolved, the form and blending ratio of the nickel are important, but furthermore, sufficient attention must be paid to the melting and extraction temperatures. need to pay. That is, a molten bath of nickel and titanium is quickly formed, and CO
Analytical accuracy, such as efficiently promoting gas extraction,
In consideration of rapidity, it is advantageous to set the temperature to 2000°C or higher, and it is particularly preferable to maintain the temperature in the range of 2400 to 3000°C.゛In other words, Figure 3 shows a titanium standard sample containing 1870 ppm oxygen inserted into a nickel pipe, dissolved at various temperatures, extracted and then analyzed for oxygen, and summarized the relationship between the dissolution and extraction temperature and the oxygen extraction rate. However, even at 2000°C, the extraction rate was found to be relatively high at 75% for practical use, and furthermore, at 2400°C, an extraction rate of 100% was obtained.

However, if the temperature exceeds 3000° C., the crucible becomes severely eroded and extraction becomes unstable, which is not practical.

Table 4 Blank values for nickel and platinum As detailed above, according to the present invention, the method is economically more advantageous than the conventional platinum bath method and has excellent accuracy and reproducibility comparable to that method. It is an invention with high industrial value as it allows the analysis and quantification of oxygen absorbed into titanium, etc.

[Brief explanation of drawings]

Figure 1 is a schematic diagram explaining the morphology of the titanium sample and nickel applied to the present invention, and Figure 2 is the oxygen analysis value and the weight of the same sample and platinum when the weight ratio of the titanium sample and nickel is changed. Figure 3 shows the oxygen analysis values when the ratio is changed, and the relationship between the dissolution and extraction temperatures and the oxygen extraction rate. Patent applicant: Kobe Steel, Ltd. Yoshiyuki Kaji, Patent Attorney

Claims (1)

[Claims] In this method, a titanium group metal or alloy is dissolved in a graphite crucible under a cine-activated atmosphere, and oxygen in the titanium is reacted with carbon to extract carbon monoxide, which is then quantitatively analyzed. A method for oxygen analysis of titanium group metals or alloys thereof, characterized by dissolving nickel in the presence of 7 to 17 times the weight of the sample.