JPH065205B2 - High temperature deformation resistance judgment method - Google Patents

Description

The present invention relates to a high temperature deformation resistance test method.

[Prior Art] In the conventional high-temperature deformation resistance test method, a plate material to be tested is directly placed in a high-temperature environment to test its high-temperature deformation resistance.

[Problems to be Solved by the Invention] However, in the conventional high temperature deformation resistance test method, when testing a plate material having a high melting point temperature such as tungsten or molybdenum, the test equipment becomes complicated and expensive. There are drawbacks.

Therefore, in view of the above-mentioned drawbacks, an object of the present invention is to perform a high temperature deformation resistance test without placing it in a high temperature environment even for a test plate material having a high melting point, which is a simple and novel high temperature deformation resistance test method. Is to provide.

[Means for Solving the Problems] According to the present invention, of the crack surfaces obtained by deforming a plate material to an Erichsen value of the plate material or more, the crack direction of the crack surface is measured, and the crack directionality is measured. Based on the above, there is obtained a high temperature deformation resistance test method characterized by testing the high temperature deformation resistance of the plate material.

Embodiments Embodiments of the present invention will be described with reference to the drawings.

First, as shown in No. 1, three types of molybdenum ingots with different thicknesses (30mm, 20mm, 10mm) obtained by the known powder metallurgy method were repeatedly subjected to hot, warm, cold rolling and intermediate annealing. In addition, when rolling each ingot, only one direction rolling plate material (hereinafter referred to as straight rolls), and a certain intermediate thickness plate material rolled by changing the roll direction at right angles ( (Hereinafter referred to as cross roll), and pressure was applied to the final finished thickness.

Next, as shown in Fig. 1, each rolled sheet material is
Extrude the indenter ball for Erichsen test 3 mm deeper than the Erichsen value of JIS B7729 to obtain a cracked surface 1.

As shown in FIG. 2, the crack direction of the crack surface obtained from each of the plate materials shown in Table 1 is Ab, Bb, Cb
It has four directions, and other plate materials have two or three directions. That is, in the plate materials of Ab, Bb, and Cb that are cross-rolled under a certain condition, the crystal grains of the rolled plate material are uniformly stretched in the vertical and horizontal directions, so that they react uniformly to the strain and the grain boundary This is because the strength is uniform.

As described above, the parameter E in the above Table 1 is obtained by (cross roll start thickness-final plate thickness) / (ingot thickness-final plate thickness).

Generally, the amount of deformation of a plate is called the processing rate, and
The final plate thickness) / ingot thickness × 100 (%).
For example, when a 10 mm thick ingot is rolled to form a 1 mm thick plate, the processing rate is 90%. Here, since the ingot thickness and the final plate thickness change, the ratio between the ingot thickness and the processed thickness is made constant.

The present inventor has adopted the above-described parameter E based on the same concept as the processing rate. That is, since the ingot thickness and the final thickness are different for each plate material of A, B, and C,
In order to make it possible to compare the test results of the A, B, and C plate materials, the total processing thickness and the cross roll are calculated by (cross roll start thickness-final plate thickness) / (ingot thickness-final plate thickness). The ratio with the processing amount was used as the parameter E. Therefore, from the E value, it is possible to know the ratio of the processing amount by the cross roll to the processing amount from the ingot to the final plate thickness for each of the plate materials A, B, and C.

Next, each plate material shown in Table 1 was cut into a piece having a width of 20 mm and a length of 200 mm by the usual high temperature deformation resistance test method shown in FIG.
× 10 ^-6 Torr, heating temperature 1700 ° C, holding time 10Hr
Heating conditions were applied. Then cooled molybdenum plate 2
Take out the maximum deformation, as shown in Fig. 4,
It was measured.

The results are shown in Table 2.

As can be seen from Table 2, the maximum amount of deformation was 0 (mm) in each of the Ab, Bb, and Cb plate materials. Therefore, from the test data, the E value is 0.16 to 0.239.
It is preferable that it is between.

In other words, the ratio of the amount processed by the cross roll to the amount processed from the ingot to the final plate thickness is about 16
It can be seen that the plate material with the percentage of 24% to 24% is the most excellent in high temperature deformation resistance.

By the way, the plate members of Ab, Bb, and Cb have four cracking directions, as is clear from FIG. That is, all of these plate materials having E values of 0.16 to 0.239 had cracks running in four directions, and the high temperature deformation amount thereof was 0 (mm).

As described above, the main object of the present invention is to perform the complicated calculation of whether or not the E value is within the predetermined range described above,
The purpose is to easily determine the high-temperature deformation resistance from the crack form by the Erichsen test.

In addition, from the above-mentioned test results, for example, even if there is a small number of cracks in one of the four crack directions as in the Ab plate material, the high temperature deformation amount was 0 (mm). That is, it was confirmed that even if the number of cracks in one direction was small, if the cracks exhibited in four directions, excellent high temperature deformation resistance was obtained.

The reason for this is not clear, but it is considered as follows.

Molybdenum recrystallizes at a high temperature of about 1700 ° C. as in the above embodiment, that is, a rolled sheet material generally has a fibrous structure, but at such a high temperature, it recrystallizes to form crystals. Becomes granular. When this recrystallization occurs, the plate material that has not been cross-rolled has more structure elongated in the rolling direction, and it is considered that there is a large difference in strain amount from the structure orthogonal to the rolling direction. Therefore, at the time of recrystallization, it is considered that deformation occurs due to the difference in the release energy of the strain amount between the structure parallel to the rolling direction and the structure perpendicular to the rolling direction.

In the present invention, if a certain amount of cross roll processing is performed, the amount of strain between the structure parallel to the rolling direction and the structure perpendicular to the rolling direction can be made uniform, and this uniformity can be easily obtained from the cracking form by the Erichsen test. The focus is on being able to judge.

As a result, regardless of the rolling direction such as a straight roll or a cross roll, it is recognized that when the plate material has four crack directions, the deformation at high temperature hardly occurs.

That is, there is a certain correlation between the crack direction of the crack surface of the plate material and the high temperature deformation resistance. In the above examples, the No. 2 test piece (size is 90 ± 2 mm square) was measured by the A method of the Erichsen test according to JIS.

Generally, the Erichsen test represents the moving distance of the tip of the punch when a crack reaching the back surface is formed in at least one place of the test piece. It is difficult to easily visually identify the cracking form as shown in the figure. Therefore, in order to easily distinguish the cracked form visually, for example, it is desirable to move (protrude) the tip of the punch by 0.5 mm or more from the Erichsen value according to JIS to open the cracked part largely. . Where 0.5m
In the above-mentioned JIS A method, it is set to 0.m or more.
This is because the amount of protrusion is sufficiently secured in consideration of the fact that there is a gap (play) of 05 mm.

[Effects of the Invention] According to the present invention, it is possible to test the high temperature deformation resistance of a plate material based on only the crack directionality of the crack surface of the plate material without directly performing the actual measurement test in a high temperature environment. it can.

[Brief description of drawings]

FIG. 1 is a perspective view of a crack surface of a plate material according to an embodiment of the present invention, FIG. 2 is a schematic view showing a crack direction of the crack surface according to an embodiment of the present invention, and FIG. 3 is a conventional high temperature resistance. FIG. 4 is a schematic diagram of a deformability test method, and FIG. 4 is a schematic diagram of a method of measuring the maximum deformation amount. 1 ... Cracked surface, 2 ... Molybdenum plate, 3 ... Vacuum furnace.

Claims (2)

[Claims] 1. A crack surface obtained by deforming a plate material to an Erichsen value or more of the plate material, the crack direction of the crack surface is measured, and the high temperature deformation resistance of the plate material is based on the crack direction. A method for judging high temperature deformation resistance, which is characterized by judging the property. 2. The high temperature deformation resistance judging method according to claim 1, wherein the cracked surface is obtained by pushing the punch tip by 0.5 mm or more from the Erichsen value of the plate material. Judgment method.