JPS591661A - Manufacture of pure titanium plate with little anisotropy in yield strength - Google Patents

Abstract

PURPOSE:To manufacture simply and easily a pure Ti plate with little anisotropy in the yield strength, by cold-rolling a hot-or cold-rolled and annealed pure Ti plate at a low draft and by optionally annealing it under specified conditions. CONSTITUTION:A hot-or cold-rolled and annealed pure Ti plate is cold-rolled at a low draft. When the Ti plate is made of pure Ti, the draft is adjusted to >=about 5%, and when the Ti plate contains a reinforcing element such as Fe or O, the draft is adjusted to <=about 2.5%. The cold rolled plate is optionally annealed at <=500 deg.C for <=30min.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a pure titanium plate with low strength anisotropy and which exhibits approximately the same strength in the longitudinal direction and the width direction.

In recent years, the demand for titanium as a construction material for aircraft components, chemical plants, seawater desalination plants, etc. has been increasing.At the same time, there has been an increase in demand for the various properties of pure titanium sheets used as various structural components. is becoming even more difficult.

By the way, titanium plates are usually produced by unidirectional rolling in the process of "hot rolling - annealing - pickling - cold rolling - annealing". In order to undergo strong processing, the titanium plate manufactured by K in this way has a proof stress ratio [σ0.2('r)/σ0 .2
(L): l was as high as 1.2 to 3, indicating remarkable proof stress anisotropy. The degree of proof stress anisotropy of a titanium plate, expressed as a proof stress ratio, is normally a value as shown in 2. In high-strength pure titanium plates with a high amount of steel, the absolute value of the difference in yield strength between the L direction and the T direction could reach as much as 15 kgf/yl.

Conventionally, when the strength anisotropy in the L direction and the T direction is a problem,
For example, for titanium plates that exhibit a higher proof stress value in the T direction than in the L direction, measures have been taken to reduce the proof stress anisotropy by further rolling (cross rolling) in the T direction. Loss rolling is only effective for sheet-shaped products (however, the rolling width of the product is less than or equal to the roll effective width), and is only effective for long products where the rolling width of the product exceeds the roll effective width. However, there is a problem in that it cannot be applied to products such as coils, for example.

From the above-mentioned viewpoint, the inventors of the present invention have proposed that even if the product is a long product such as a coil and has dimensions that cannot be cross-rolled, it is possible to do so without changing the equipment currently installed in the factory. , ■, As a result of research to find a method for producing pure titanium plates with less yield strength anisotropy in the L and T directions, we found that (a) hot rolling or For a pure titanium plate that has been cold rolled and then annealed,
If light reduction rolling is performed in the L direction, the proof stress ratio in the I and T directions [
σ0.2 (T) / σ0.2 (L)] is reduced, and by further annealing a pure titanium plate that has been subjected to light reduction rolling as shown in (b), L. We have come to the knowledge shown in (a) and (b) above that ductility can be improved to some extent without significantly changing the yield strength ratio in the T direction.

Therefore, the present invention has been made based on the above findings, and the gist thereof is to further cold-roll a pure titanium plate that has been hot-rolled or cold-rolled and then annealed at a light reduction rate. , a method for manufacturing a pure titanium plate with low proof stress anisotropy, characterized by annealing at a temperature of 500° C. or less for 30 minutes or less, if necessary.

Here, pure titanium plate means Fe: 01 to 0 as a reinforcing element.
5% (hereinafter, the section indicating the amount of the composition component is referred to as the section by weight), O
: Contains approximately 0.06 to 0.04%, and also includes titanium plates containing unavoidable impurities such as C, H, and N, and it goes without saying that it also includes not only sheet shapes but also coils. be.

In addition, in the case of pure titanium sheets containing reinforcing elements such as Fe and 0, the rolling reduction ratio of cold rolling under light rolling is determined by the ASTM B-265
r, 4 and A, there is a possibility that the elongation of 15% or more specified in the MS4901 standard cannot be obtained, so as can be seen from the examples below, the rolling reduction ratio is preferably 2.5% or less.

However, in the case of a pure titanium plate containing no reinforcing elements and having good ductility, a sufficient elongation rate can be obtained even if the rolling reduction is 5% or more.

Of course, it is possible to use a titanium plate that has been subjected to such light reduction and cold rolling as a product as is, but in this case, the titanium plate is slightly work-hardened, so When this cold-rolled sheet is to be formed and used, it is easier to form the sheet by further annealing it.

If the annealing temperature exceeds 500°C or the annealing time exceeds 30 minutes, the proof stress ratio in the L-T direction, which was reduced by light reduction cold rolling, will return to its value before rolling. Therefore, the annealing temperature and the annealing time are preferably 500° C. or less and 30 minutes or less, respectively.

Next, the present invention will be specifically explained using examples and comparisons with comparative examples.

Examples First, a plate having the chemical composition shown in Table 1, manufactured by a normal manufacturing process (hot rolling - annealing, one acid wash, one cold rolling, one annealing, one pickle), is a unidirectionally rolled material. Thickness::1. , 2 'i'
A mH pure titanium plate was prepared.

When the mechanical properties of this pure titanium plate were measured, the values shown in Table 2 were obtained.

In addition, 0 minutes, 0 minutes ν and F of the test materials shown in Table 1
As shown in Table 2, the C material with a high content of e has an elongation of only 12 to 3, which does not satisfy the elongation values specified in ASTM B-265 Or, 4 and AMS 4901, and cannot be used as a structural member. It was reconfirmed that it did not have appropriate properties.

Next, material A and material B shown in Table 1 were subjected to cold rolling and annealing after cold rolling under the conditions shown below, and the resulting pure titanium plate was made with one bow in the T direction. Tests were conducted to determine its mechanical properties.

L direction cold rolling ratio (%): 0.23', 0.5, 1, 2
．． 5°5, 10° Annealing temperature E): O (as cold rolled), 4.00°500, 600. 700° annealing time: 30 minutes (furnace time after raising the furnace temperature).

Tables 3 and 4 show the results of the tensile tests for the A and B 41 products obtained in this way, and the effects of cold rolling reduction on mechanical properties are shown in Figures 1 and 3. The influence of the cold rolling rate on the T- and L-direction yield strength ratios of the cold-rolled material is shown in diagrams in FIGS. 2 and 4, respectively.

From the results for A paulownia shown in Table 3 and Figure 1, it is clear that the titanium plate Ar was cold rolled and not annealed
At t, the L direction yield strength increases as the rolling ratio increases, but the T direction yield strength decreases as the rolling ratio increases up to 0.5 rolling ratio, and reaches a minimum value at a rolling ratio of 0.5 to 1%. It is clear that if the rolling rate is further increased, the value will turn to increase. Furthermore, it is clear from the results for material B shown in Table 4 and FIG. 3 that the same tendency is shown even when the material is cold rolled.

In addition, from the results of A-rate shown in Table 3 and Figure 2, for example, when looking at the yield strength ratio in the L and T directions of a titanium plate as cold rolled, it decreases as the rolling ratio increases. The minimum value is 1.11 inches at a rolling ratio of 2.5%, but it can be seen that as the rolling ratio is further increased, the proof stress ratio tends to increase slightly. However, even if the rolling reduction is ]0%, the yield strength ratio in the LT direction is 1.13, and the effect of reducing the yield strength anisotropy in the LT direction can be recognized. The results for material B shown in Table 4 and FIG. 4%
Suddenly, a phenomenon appears in which the ductility decreases significantly. Therefore, as mentioned above, ASTM B-265Gr
ade 4 or AMS 4901 standard with elongation of 15
% or more, it can be seen that these conditions are satisfied, work hardening is not significant, and the rolling ratio is 5 or more.

On the other hand, when material A and material B are annealed after cold rolling, the proof stress ratio in the L-T direction [σO,'2 (T)/σ0.2 ( L)
) increases compared to the as-cold-rolled material, and as the annealing flow rate increases, the yield strength ratio approaches the yield strength ratio before light reduction cold rolling. However, when looking at the change in proof stress ratio under the same heating conditions, it still shows a minimum value at a rolling reduction of 2.5% when the annealing flow rate is below 500t, and it is clear that an anisotropy reduction effect is still observed. It is.

From this, it can be seen that for materials such as material B, where sufficient elongation cannot be obtained by cold working, annealing at 500° C. or lower is effective for improving ductility. In fact, as shown in FIG. 5, it was confirmed that when material B was subjected to cold working at rolling ratios of 25 and 5 inches and then annealed, the elongation recovered.

Also from the results shown above, the proof stress anisotropy of the pure titanium plate in the L-T direction can be reduced by cold rolling in the L direction at a cold rolling rate of 5% or less. It is clear that this effect remains even if annealing is performed at 500° C. or lower after cold rolling to improve ductility. Also, if we consider the results shown in Table 3 and Figure 2,
- It can be seen that it is most desirable to set the rolling rate to about 2 to 3%.

Although the explanation has so far focused on pure titanium rolled plates, the same effect of reducing proof stress anisotropy will be exhibited even if the method of this invention is applied to titanium alloy plates other than pure titanium plates. It was confirmed that

As described above, according to the present invention, even if a long rolled pure titanium plate such as a coil is subjected to light reduction rolling in the same direction as the rolling direction of the rolled plate, its yield strength anisotropy can be improved. Industrially useful effects can be brought about, such as the ability to reliably reduce the stress, and the ability to simply and easily produce pure titanium plates with low yield anisotropy using existing equipment.

[Brief explanation of drawings]

Figures 1 and 3 are diagrams showing the influence of cold rolling reduction on the mechanical properties of cold-rolled materials, and Figures 2 and 4 are diagrams showing the T, T, and directional strength ratios of cold-rolled materials. Fig. 5 is a diagram showing the effects of cold rolling rate and annealing temperature on the elongation recovery of material B in an example of the present invention subjected to cold working at rolling rates of 2.5 and 5. FIG. 3 is a diagram showing the influence of annealing temperature. Applicant Sumitomo Metal Industries Co., Ltd. Agent Tomi 1) Kazuo and 1 other person 1st factor μg half c%) Figure 2 + I'ia /liE SL-, 56,
2(T)/of, 2(L)

Claims (1)

[Claims] A pure titanium plate that has been hot rolled or cold rolled and then annealed,
A method for producing a pure titanium plate with low yield strength anisotropy, characterized by further cold rolling at a light reduction rate and, if necessary, annealing at a temperature of 500° C. or less for 30 minutes or less.