JPS607027B2 - Manufacturing method for cold-rolled titanium or zirconium sheets for warm processing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a high-strength titanium or zirconium rolled plate for warm working.

As is well known, titanium and zirconium have the same crystal structure and therefore have the same problems with their workability. To explain titanium, JISI
There are some differences between soft materials equivalent to JIS Class 2 or 3 hard materials, but generally speaking, in addition to being difficult to process in cold conditions, it is difficult to work in warm conditions at relatively low temperatures of 100 to 400 degrees Celsius. However, it is extremely difficult to perform plastic working under double tensile stress, such as stretching or bending.

For this reason, titanium or zirconium hot-rolled or cold-rolled plates are usually processed at a high temperature of 50,000 or higher, but this naturally causes problems such as deterioration of thermoeconomic efficiency, and thick scales on the surface of the material. There is also the problem that scale is formed, making it difficult to remove scale.

After cold rolling, titanium and zirconium cold-rolled sheets are usually subjected to annealing to eliminate work hardening and improve workability. The reason why titanium cannot be fundamentally improved in workability is that the poor workability of titanium at 100 to 400°C is common not only to hard materials but also to soft materials. It is clear that this is not the case.

The object of the present invention is to provide 100% to
The objective is to eliminate the poor warm workability at 400 mm and also to increase the material strength of this type of rolled plate.

The inventors of the present invention previously discovered that the poor workability of titanium zirconium when processed at temperatures of 100 to 400 oo was due to the small amount of twin crystals generated in the material during processing. We have developed a method to generate twins in the material in advance by applying strain to at least the part of the material that is to be processed, thereby increasing its subsequent workability, and has achieved great results ( Special request 1977
4-1133733).

Figure 1 shows ST-40 titanium (JISI type equivalent material)
The figure shows a (0002) pole figure of , and it can be seen from the figure that when the material is plate-like, the texture tends to have the C axis of the hexagonal system strongly concentrated near the thickness direction of the plate.

For this reason, it becomes difficult for the material to deform in the thickness direction due to slipping, and when deforming in the thickness direction, the orientation of the twin C-axis generated in the material changes, and the number of twins increases, resulting in a change in the thickness direction. It can be considered that this promotes deformation and thereby facilitates plastic working under tensile stress. The titanium or zirconium cold-rolled sheet of the present invention is a further development of this idea, and the above-mentioned "processing that applies strain" performed at the material processing stage is rolled into the manufacturing process of the material, that is, the cold-rolled sheet. The poor warm workability at 100 to 400 qo is removed by directly incorporating it as cold rolling at room temperature with a reduction rate of 1 to 30%, but what is important is that By incorporating cold rolling at room temperature, especially in the final stage of the cold-rolled sheet manufacturing process, and making the rolled sheet into a product as it is without applying sintering, it is preferable in terms of the warm processing obtained by the above-mentioned cold rolling. In addition to greatly improving the warm workability of the cold-rolled sheet by leaving the texture as it is, consideration was given to preserving the work hardening caused by cross-rolling and increasing the material strength.

Therefore, the cold-rolled sheet of the present invention has a major feature of being easy to warm-work despite its high strength, and this expands its range of use, and improves warm-workability by changing the working temperature. It makes it possible to reduce the amount of carbon dioxide, which brings about great results in improving thermoeconomic efficiency and suppressing the occurrence of scale.

Further, hot-rolled or cold-rolled sheets of titanium or zirconium are usually manufactured through the steps shown in A' or A in FIG. 3, respectively, but in the cold-rolled sheet of the present invention,
As shown in Figure B, the reduction rate is 1 to 30% at the end of the manufacturing process.
In addition to cold rolling at room temperature, as shown in Figure 3 B', if the final cold working is performed at a large rolling reduction within the range of 1 to 30%, the cold rolling after hot rolling can be carried out. can be omitted (in other words, conventional cold rolling is finished with a rolling reduction of 1 to 30%).
, Moreover, cold rolling at room temperature with a rolling reduction of 1 to 30%,
As a result of significantly improving the warm workability of cold-rolled sheets, it is possible to omit the scorching anchor (Fig. 3 ■), which was conventionally used to improve workability.
The cooling process of the present invention also makes it possible to omit the pickling treatment (Fig. 3 ■) that accompanies annealing, thereby shortening the manufacturing process and significantly reducing the cost of the product. This is a major feature of rolled sheets.

In the cold-rolled sheet of the present invention, the rolling reduction ratio of the cold rolling performed at room temperature at the end of the manufacturing process may be appropriately selected within the range of 1 to 30% depending on the product sheet thickness.

In addition, when the rolling reduction ratio is kept constant, the product plate thickness may be adjusted by the finished plate thickness of hot rolling performed before cold rolling. The reason why the reduction ratio was set in the range of 1 to 30% is because it is difficult to generate enough twins in the material under a reduction of less than 1%, and when the reduction exceeds 30%, work hardening of the material becomes large. This is because warm workability deteriorates again if the temperature is too high.

Further, the reason why rolling is performed cold at room temperature is because twins are more likely to occur at low temperatures.

Examples will be described below.

Example 1 A hard pure titanium plate was ant-blunted for 1 hour at 700 oo of 4 yanagi thickness corresponding to JIS Mineko, and the reduction rate was 07 to 40.
．． Cold rolling at room temperature was performed with varying amounts within a range of 5%.

20,000 and 40,000 for the plates that were not cold rolled (reduction ratio 0%) and the plates that were subjected to cross-rolling at room temperature, respectively.
U-bending shown in Fig. 2 at 0qo (JISZ22
48) and a tensile strength test according to JIS Z2241. The bending conditions are r=2 and 1.5t (
However, r: bending radius, t: material thickness). Results first
The table shows ○ (no cracking), × (cracking occurred) and tensile strength (
k9′ fence). Table 1 As is clear from Table 1, plates that were not cold rolled and plates with a reduction rate outside the range of the present invention have r=
Although the relatively gentle U-bending of × was impossible, the plate cold-rolled at room temperature with a rolling reduction within the range of the present invention (1 to 30%) could not only be bent with r = normal bending. , it was able to sufficiently withstand bending work of r=1.5t.

Furthermore, when comparing the tensile strength, it can be seen that, for example, a plate with a rolling reduction of 28.3% has approximately twice the strength compared to a plate that was not subjected to cross-rolling.

Example 2 The same cold rolling as in Example 1 was carried out on a soft pure titanium plate which had been subjected to sintering at 680 qo for 1 hour and had a thickness of 4 willows corresponding to the JISI type.

The results are shown in Table 2. In this experiment, as in Example 1, the rolled board of the present invention had high material strength.
It was confirmed that the material had a high degree of workability at relatively low temperatures of 0.000 to 400.00. Table 2 The above examples show examples for pure titanium plates, but the present invention is equally effective for pure zirconium plates. It is also highly effective in increasing the material strength and improving the warm workability of titanium-based alloy sheets and zirconium-based alloy sheets.

The titanium or zirconium cold-rolled sheet of the present invention also includes cold-rolled sheets of these alloys.

Example 3 After cold rolling with 4 ribs corresponding to JISI type,
Table 3 shows the results of cold rolling a European pure titanium plate annealed at 68,000°C for 1 hour at various rolling reductions shown in Table 3. It can also be seen that by performing cold working before warm working, it has excellent workability in warm working.

Table 3

[Brief explanation of the drawing]

Fig. 1 is a (0002) pole figure of pure titanium, Fig. 2 is an explanatory diagram of the U-bending method carried out to investigate the effect of implementing the present invention, and Fig. 3 A, A', B, and B' are conventional It is a flowchart showing the difference in the manufacturing process of the board and the board of the present invention. Figure 1 Figure 2” Figure 3

Claims (1)

[Claims] 1. A method for producing a high-strength titanium or zirconium cold-rolled plate for warm working, which comprises annealing a titanium or zirconium hot-rolled plate or cold-rolled plate and then cold-rolling it at room temperature with a reduction ratio of 1 to 30%.