JPS63103043A - Ti or ti-alloy sheet - Google Patents

Abstract

PURPOSE:To obtain a Ti or Ti-alloy sheet minimal in occurrence of oil canning and having superior formability, by repeating cold rolling and annealing so as to finish into a proper sheet thickness and also by specifying respective contents of Fe, O, N, and H. CONSTITUTION:The Ti or Ti-alloy sheet which is finished into 0.2-2.0mm thickness by the repetition of cold rolling and annealing has a composition in which >=300ppm Fe is contained and (Fe+O+N+H) is regulated to <=1,500ppm and further, preferably, Fe/(Fe+O+N+H) is regulated to >=about 0.5. In this way, the Ti or Ti-alloy material free from the occurrence of wavy surface discontinuity called oil canning at the time of forming, having superior formability, and applicable to building materials can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to Ti or Ti alloy plate materials used mainly for construction materials such as roofs, external walls, and interior panels of buildings, and in particular, the present invention relates to Ti or Ti alloy plate materials used for construction materials such as roofs, external walls, and interior panels of buildings. This invention relates to a Ti or Ti alloy plate material (hereinafter simply referred to as a Ti plate material) that does not have surface defects such as the following.

[Prior art] There are three types of JIS standard products for industrial pure Ti classified by strength level (JIS H4600: 1 to 1).
Type 3), these strength levels are determined by adjusting the content of impurity elements such as Fe and 0. Note that impurity elements other than Fe and 0 include N, H, although the quantity is small.
, C, etc. are included.

The biggest use of the above-mentioned industrial pure Ti so far has been in thin-walled titanium tubes for heat exchangers, and JIS Class 2 pure Ti has been used for this. However, recently, new uses for Ti have been developed, and pure Ti is increasingly being used as a building material.
IS1 type pure Ti is used. Pure Ti is generally supplied in the form of a coil.

[Problems to be Solved by the Invention] By the way, when a JISI type Ti coil is used for building materials such as roofs and wall materials, the Ti thin plate pulled out from the coil must be formed into a shape according to the application area. It has been pointed out that at this time, the aforementioned surface defects called beko occur in the originally flat paneled doors, which often seriously impairs the appearance of roofs and walls. In particular, in the case of colored Ti, the long-awaited feature of excellent aesthetics is lost, and the product value drops all at once. The cause of the bulge is thought to be that the bent portion shrinks in the longitudinal direction during molding and applies compressive internal stress to the flat portion.

Such bending occurs more noticeably when roll forming is performed than when press bending is performed.

・Various methods have been tried or proposed as a means to prevent the occurrence of bulges, so I will explain them below. First, based on the idea of optimizing the pass schedule in roll forming, Many tests have been attempted. As a specific improvement measure, there is a method of increasing the number of stages of forming rolls and reducing the amount of molding per stage. However, in applications where molding is often performed on-site, such as roof construction work, increasing the number of molding machines increases the total weight and required space, which is a big burden on workability and, of course, increases equipment costs. There are also some notable ones. Furthermore, since Ti plates originally have high anisotropy, they shrink in the longitudinal direction at bends, making them more prone to warping than mild steel plates or stainless steel plates, and have traditionally been used for mild steel plates. The above-mentioned method alone, such as changing the bus schedule in the molding machine, could not be a natural and effective method for preventing the occurrence of sagging on titanium plates.

On the other hand, it is also possible to consider a method (2) of increasing the thickness of the material to suppress the occurrence of bulges. However, the material cost of the Ti plate is high, and in the current situation where it is desired to make the plate as thin as possible, this method cannot be said to be suitable for the actual situation.

Therefore, the inventors of the present invention have conducted repeated research with the idea of suppressing the occurrence of bulges by improving the material of the Ti thin plate. The present invention was completed as a result of such research, and is made of Ti, which is an excellent material that does not cause bulges.
The purpose is to provide plate materials.

[Means for Solving the Problems] The Ti plate material of the present invention that achieves the above object is a T'i or Ti alloy finished to a thickness of 0.2 to 2.0 mm by arbitrarily repeating cold rolling and annealing. A plate material with an Fe content of 3
00 ppm or more and [Fe+O+N+H3 amount is 15
The gist lies in the fact that it is less than 0099111.

[Effect] The mechanism of the occurrence of bulge is thought to be that, as mentioned above, the bent portion shrinks in the longitudinal direction during molding, and compressive residual stress is applied to the flat portion. Taking into account the mechanism of the formation of bulges, we investigated what kind of mechanical properties of materials are effective in preventing the formation of bulges, and as a result, we obtained the following knowledge.

In other words, when comparing materials A with 82 types of stress-strain characteristics as shown in Figure 1, material A (conventional material) begins to undergo plastic deformation at a relatively low stress, and gradually softens and reduces stress. However, material B (an improved material exhibiting the targeted properties) has a relatively high elastic limit and the degree of strain softening at the initial stage of plastic deformation is smaller than that of material A. Therefore, when forming a material with low strain softening like material B, the deformation will not concentrate on the bent part and affect the flat part, and the occurrence of bulge in the flat part can be suppressed. It was thought that it might be.

Therefore, in the present invention, in order to obtain a material having stress-strain characteristics like the above-mentioned material B, we focused on impurity elements in the material, particularly Fe. In other words, Fe has the most remarkable effect on the crystal grain size among the impurity elements of pure Tt, and is an element that increases the strength at a lower rate than N and O, making it an effective element in obtaining materials with the above characteristics. It is considered to be an element that can be used as a means. Therefore, in order to confirm the validity of the above guideline, various Ti plates with different amounts of Fe were made and forming tests were conducted, and as a result, the Ti plate material of the present invention as shown in the above structure was completed.

In other words, Figure 2 shows the relationship between the Fe content in the Ti plate and the height Hp.
: Experimental result graph showing the relationship (defined in Figure 7), and
Figure 2 is a graph showing the relationship between Fe content and average grain size.As shown in Figure 2, the Fe content is 300 ppp.
m or more, the occurrence of becos is suppressed. Furthermore, as shown in Figure 3, when the Fe content is 300 ppm or more, the average crystal grain size of the material is approximately 40 μm or less, and the distribution of crystal grain size is relatively uniform, and the shape of the sample after molding is There was almost no evidence of twinning deformation in the microstructure.

On the other hand, when the Fe content was less than 300 ppm, the average crystal grain size was large and the degree of mixed grains became significant, and in particular, many twins generated during molding were observed in the large crystal grains. It is thought that the occurrence of such twins at the initial stage of deformation lowers the elastic limit of the stress-strain curve, giving the stress-strain curve as shown in the conventional material (material A) in FIG. For the above reasons, in the present invention, the Fe content in the Ti plate is set to 300 p.
l) Must be 111 or more.

On the other hand, from the viewpoint of preventing the occurrence of bulges during forming, it is desirable to have a large amount of Fe, but when using Ti plates as building materials, if the strength is too high, the formability will deteriorate, making on-site construction difficult, and roofing This may cause rain leaks during construction. We have achieved the formability required for Ti plate materials for building materials.
When examining the example of a tile stick roof with a wall thickness of 0.4 mm and a single roof with a wall thickness of 3 mm, the 0.2% yield strength was 35.
It was found that it was necessary to keep the weight below 100 kg/mm.

Therefore, we investigated the relationship between the total amount of impurity elements including Fe, O, N, and H and 0.2% yield strength, and obtained the results shown in Figure 4. Ta. As understood from Fig. 4 (Fe+O+
When the amount of N+H) exceeds 1500 ppm, the 0.2% yield strength exceeds 35 kg/mm2, and from this result, in the present invention, the amount of (Fe+O+N+H) needs to be 1500 ppm or less. There is no particular restriction on the proportion of Fe in the impurities (Fe, O, N, H), but since it is more desirable to add Fe than 0 in order to satisfy the required properties, conventional materials [0/(F e + O+ N + H) is 0.5 or more, unlike [Fe amount (Fe+O+N+H
) is recommended to be 0.5 or more.

In the present invention, by adjusting the component composition as described above, it is possible to obtain a Ti plate material that has good moldability and is free from bulges. As mentioned before, Ti plates have high material costs and it is desirable to make the plate thickness as thin as possible.
On the other hand, from the perspective of ensuring the necessary rigidity as a building material, it is not possible to make the plate thickness too thin. For these reasons, there is naturally a desirable thickness range for the thickness of Ti plates for building materials, and specifically, the thickness can be increased from 0.2 to 2 by repeating cold rolling and annealing.
, a Ti plate adjusted to 0 mm is used. The present invention is particularly useful for Ti plates having such thicknesses. Furthermore, although the description has been made above mainly regarding pure Ti plate materials, the present invention can be implemented in the same manner with respect to Ti alloy plates to which alloying elements are appropriately added as necessary.

[Example] Example I A pure Ti plate material was obtained by repeating cold rolling and annealing using a material with a modified content of Fe and other impurity elements in accordance with the normal manufacturing process for industrial pure Ti coils. Ta. Next, the pure Ti plate material was roll-formed to produce a groove plate for a tile rod roof as shown in FIG. The forming machine used was a commercially available machine for forming colored iron plates into tile rod roofing material. The profile of the obtained groove plate in the longitudinal direction of the flat part was measured using a non-contact displacement meter according to the method shown in FIG. 6, and the profile height (Hp) was determined according to the definition shown in FIG. The relationship between Hp and Fe content obtained in this way is graphed as shown in Figure 2, and as mentioned above, the Fe content is 300 p.
Above pm, Hp decreases as the amount of Fe increases, and 300
It was found that the addition of Fe in an amount of ppm or more has the effect of suppressing the occurrence of bulge. Visual observation of the molded product shows that when Hp is 4 mm/m or less, the beak becomes less noticeable, and when p is 2 mm/m or less, the beak is almost invisible in appearance.Therefore, Hp is 2 mm/m or less. It is desirable that the Fe content be 400 ppm or more.Also, when the relationship between the average crystal grain size after molding and the Fe content for the above sample material was graphed, it was found that
The result is as shown in the figure. It was found that the Fe content has a close relationship with the average crystal grain size, and when the Fe content is 300 ppm or more, the average crystal grain size becomes 40 μm or less. And when the amount of Fe is 300 ppm or more, the average grain size is 40
It was found that the shape of the stress-strain curve in the tensile test for the test materials of μm or less had the tendency shown in material B (improved material) in FIG.

Example 2 In a conventional pure Ti plate, the 0 content is higher than the Fe content. It is said that this is not only because 0 has a greater strength adjustment effect than Fe, but also because adding too much Fe promotes deterioration of corrosion resistance and hydrogen absorption at high temperatures. However, since there is no need to worry about such problems regarding Ti plates for building materials considering the environment in which they are used, a sample material with a specially increased amount of Fe (sample material IL in Table 1) was prepared. The results of a molding test for this sample material were that Hp was Omm/m and 0.4 mu/m, and Fe
It was confirmed that increasing the amount is extremely effective in preventing beko. In this experiment, we confirmed the effect of preventing bulges in roll forming, where bulges are particularly likely to occur, but bulges can also occur depending on the conditions in press bending and press forming, so the Ti plate of the present invention was also used in such forming. It is effective to use

[Effects of the Invention] The present invention is configured as described above, and has been able to provide a thin Ti plate for building materials with less occurrence of bulge and good moldability.

[Brief explanation of the drawing]

Figure 1 is a graph showing the stress-strain characteristics of conventional material and improved material, Figure 2 is a graph showing the relationship between Hp and Fe content, and Figure 3 is a graph showing the relationship between average grain size and Fe content. graph,
Figure 4 is a graph showing the relationship between 0.2% yield strength and (Fe+O+N+H) content, Figures 5 (a) and (b) are side and front views showing the groove plate shape of a tile rod roof, and Figure 6. 7 is an explanatory perspective view showing the investigation status of the profile on the flat surface of the molded product, and FIG. 7 is an explanatory diagram schematically showing the profile on the flat surface of the molded product.

Claims (1)

[Claims] Repeat cold rolling and annealing to a thickness of 0.2 to 2.0
Ti or Ti alloy plate material finished in mm, Fe
The content is 300 ppm or more and [Fe+0+N+H]
A Ti or Ti alloy plate material having an amount of 1500 ppm or less.