JPH0610329B2 - Pure titanium thin plate for building materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a pure titanium thin plate mainly used for building materials such as a roof, an outer wall or an interior panel of a building. The present invention relates to a pure titanium thin plate for building materials which does not cause distortion.

[Prior Art] A pure titanium thin plate is generally manufactured by performing vacuum annealing after a cold rolling step, and a pure titanium thin plate manufactured by such an annealing method (hereinafter sometimes simply referred to as a titanium plate). It has been pointed out that the above-mentioned surface defects called "peco" are likely to occur when the titanium plate is subjected to a forming process when (1) is used for a roof plate or a wall material. When a peco occurs, the appearance of the roof and walls is significantly impaired, and the distinctive features of titanium and colored titanium are lost.

It is considered that the cause of such a peco is caused by the fact that the bent portion shrinks in the longitudinal direction at the time of molding, and the internal stress due to the compression occurs in the flat portion. Compared to the case, the roll forming is more remarkable.

The following various methods have been conventionally used as means for preventing the generation of pesos.

(1) Under the concept of optimizing the pass schedule in roll forming, increase the number of forming rolls and decrease the amount of forming per one stage.

(2) Since the peco is originally caused by the buckling phenomenon of the flat part of the material, the plate thickness of the material is increased to suppress the buckling.

(3) Improving the material quality for the purpose of preventing the occurrence of pesos [Example of studying thin steel sheets: plastic forming and processing Vol 20, No.
225 (1979) P.933], etc., and (3-a) increase the proportional limit of the material to 35 Kg / mm ² or more (3-b) the strain ratio of the material (contraction strain in the direction perpendicular to tension / It has been proposed that (3) the yield elongation (YE) of the material be increased.

[Problems to be Solved by the Invention] However, the above-mentioned conventional techniques have the following problems.

Regarding (1) For applications such as roof construction work that often involves local molding, an increase in the total weight and required space due to an increase in the number of roll stages of the molding machine is a heavy burden in terms of workability. The increase in equipment cost is also remarkable. In addition, since titanium plate is a material that is much more likely to generate pesos than mild steel plate, the above-mentioned means such as changing the pass schedule with a molding machine that has been used for mild steel plate is not enough for titanium plate. It cannot be a fundamental and effective method of preventing pekoe generation.

Regarding (2) Since the titanium plate has a high material cost, it is difficult to adopt the method of thickening the titanium plate in terms of cost reduction.

Regarding (3) It is difficult to adopt the above method for improving the material quality of the thin steel plate to the titanium plate for the following reason.

In the case of (3-a), if the impurity element is increased in titanium, the proportional limit is increased, but
It is necessary to facilitate on-site construction, and since the Young's modulus of titanium is about half that of steel, springback tends to increase during molding and construction, and it is also necessary to prevent this. . For this reason, it is customary to use a soft material having a low content of impurity elements, and since the proportional limit is about 25 kg / mm ² at most, it is impossible to prevent peko.

In the case of (3-B), steel, which is a material that is close to isotropic, can have a small strain ratio, but titanium has a strong anisotropy, and therefore cannot have a strain ratio as small as that of steel.

In the case of (3-c), if the yield elongation is 6 to 8%, it is considered to be advantageous for preventing peko. Since the yield elongation of steel is extremely large, the method (3-c) may be effective, but titanium is not expected to be effective because it does not show the yield elongation of steel.

The present invention has been made in view of such a situation,
It is an object of the present invention to solve all the above problems of the prior art and to provide a pure titanium thin plate for building materials which can suppress the generation of peco during molding as much as possible.

[Means for Solving the Problems] The present invention is a pure titanium thin plate for building materials produced by performing cold rolling and continuous annealing, having an average crystal grain size of 5 to 28 μm, and The gist of the invention is that no deformation exceeding the elastic limit is given from immediately after the work forming to the yielding phenomenon when deformed at least in the direction perpendicular to the rolling direction.

[Operation] The present inventors have studied and examined the cause of the occurrence of peco during the forming of a titanium plate and traced the relationship between the peco generation and the deformation behavior of the material at the initial stage of deformation. As a result, it was found that the presence or absence of the yielding phenomenon of the material is closely related to the occurrence of peko. That is, for example, when the titanium plate 1 is bent at the bent portions 2 and 2'in the directions of arrows P and P'as shown in FIG. 1, if the bent portions 2 and 2'show a yield phenomenon, The internal stress generated by the bending does not propagate further in the central portion Q direction of the titanium plate flat portion 1 ', that is, in the directions of arrows R and R'. Therefore, no compression stress is generated in the flat portion 1'of the titanium plate in the direction of the bending curve, that is, in the direction at right angles to the directions of arrows R and R'in FIG. The yield phenomenon needs to occur in the bending direction of the titanium plate, that is, in the direction of arrow P with respect to the bending portion 2 in FIG. Therefore, when the titanium plate undergoes bending from the rolling direction, the yielding phenomenon from this direction is necessary.However, in roll forming where peco is particularly likely to occur in the forming process of the titanium plate, the bending direction is Generally, the direction is perpendicular to the rolling direction. According to the research conducted by the present inventors, in this case, it was revealed that adjusting the average crystal grain size of the titanium plate to 5 to 28 μm is the first requirement for causing a sharp yield phenomenon. . Even if it is less than 5 μm, the yield phenomenon appears, and although it has the effect of preventing peco, if the average crystal grain size becomes too small, the ductility deteriorates and cracks may occur during bending during construction. Therefore, in the present invention used particularly for building materials, the average crystal grain size must be 5 μm or more in order to avoid cracking during bending.

Further, the second requirement for causing the yield phenomenon is that the deformation exceeding the elastic limit is not given to the titanium plate immediately after annealing to the work forming, and the reason will be described later, but in any case, In the present invention, by satisfying the first and second requirements at the same time, it is possible to obtain a titanium plate exhibiting a sharp yielding phenomenon.

Examination of such a method of increasing the titanium plate showed that after the titanium plate is continuously annealed, it may be further pickled. In this case, it is effective to heat and cool while keeping the plate surface flat. I understood. The annealing temperature is preferably 600 ° C. or higher for the average crystal grain size of 5 μm or more, and 750 ° C. or lower for the average crystal grain size of 28 μm or less, and the annealing time is preferably (2 to 6) minutes. I also found that it was a condition. Since the final pickling in the continuous annealing is performed at the same speed by continuously running the thin plate, the time required is 6
If the transportation speed is slower than the minute, the subsequent pickling time becomes long and the pickling becomes excessive, resulting in a decrease in yield and surface roughness. It should be noted that the one having an average crystallized grain diameter of 5 to 25 μm can also be obtained by the conventional vacuum annealing. However, in vacuum annealing, since heating and cooling are performed in a state of being wound on a large coil, it is difficult to form uniform fine crystal grains on the entire coil. In addition, since the coil has a habit of winding after annealing, it is common to perform skin pass and leveling for the purpose of increasing the flatness, and if deformation exceeding the elastic limit is applied in this process, sharp bending is given and sharp yielding phenomenon occurs. It disappears, and it becomes impossible to obtain a titanium plate that serves the purpose of the present invention. One of the reasons for defining continuous annealing as an essential requirement in the present invention is to avoid such problems,
In continuous annealing, winding does not occur, and therefore skin pass, leveling, etc. are not required, so that deformation beyond the elastic limit is not applied after annealing. Furthermore, as a result of continuous annealing + pickling, the gloss is suppressed, so the peko is not noticeable,
Those that have been vacuum annealed are glossy and peko are easily noticeable.

Examples will be described below, but the present invention is not limited to the following examples, and it is within the technical scope of the present invention to appropriately change the design in view of the gist of the preceding and the following.

[Example] A tensile test was carried out in the direction perpendicular to the rolling direction (roll forming direction) using titanium coils with various manufacturing conditions changed as a test material, and the presence or absence of a yield phenomenon and the occurrence of peko after roll forming I investigated the relationship between the situations. In this case, the manufacturing conditions were changed as follows.

(B) Final annealing method: vacuum annealing (VA) or continuous annealing + pickling (AP) (b) Annealing temperature: 650 to 830 ° C (c) Skin pass after annealing: Yes or no Heating and cooling in AP process The plate was kept horizontal in the zone, and the cooling zone was made sufficiently long to prevent deformation beyond the elastic limit when contacting the transport roll. Heating with a salt bath was performed before the pickling step, but in this case as well, deformation exceeding the elastic limit was not given. First
The manufacturing conditions and test results are shown in the table.

As is clear from Table 1, all of the test materials (1) to (5) of the present invention exhibited a yield phenomenon during molding and almost no peko occurred. On the other hand, the test materials of Comparative Examples (6) to (8) and (11) to (15)
Since the average grain size exceeds 25 μm, the yield phenomenon does not occur at the time of deformation, and as a result, peko is generated in both cases, and particularly in the cases of vacuum annealing and skin pass (11) to (15), the peco is remarkably generated. It was Comparative Example (9) was manufactured by the AP process and had an average crystal grain size of 25 μm or less, but the skin pass process did not cause the yield phenomenon, and as a result, the occurrence of peko was remarkable. In Comparative Example (10), the average crystal grain size was less than 25 μm, but the sample was vacuum annealed, and a skin pass process was required. In addition, as an example of the presence or absence of the yield phenomenon in the tensile test, among the test materials in Table 1, (2), (4), (6) and (12)
The stress-strain curves of the above are shown in FIGS. 2 to 5, respectively.
The stress-internal curve is measured by JI
The strain gauge was attached to the front and back of the SZ2201 No. 13B test piece for measurement.

From Fig. 2 and Fig. 3, the yield phenomenon (indicated by C in the figure) occurs for the specimens (2) and (4), while the specimens (6) from Fig. 4 and 5 It is understood that) and (12) do not cause the yield phenomenon.

[Advantages of the Invention] Since the titanium thin plate for building materials of the present invention is configured as described above, it is possible to almost completely suppress the generation of peko during the molding process.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a relationship between a bending direction and a compressive stress propagation direction when bending a pure titanium thin plate, and FIGS. 2 to 5 are test materials of Examples and Comparative Examples of the present invention (2 ),(Four),
It is a stress-strain curve figure about (6) and (12). 1 ... Titanium plate, 1 '... Titanium plate flat part 2, 2' ... Bent part, P, P '... Bend direction R, R' ... Compressive stress propagation direction

Continuation of the front page (56) Bibliography Summary of lectures at the Japan Institute of Metals Chugoku-Shikoku Branch, Japan Iron and Steel Association Chugoku-Shikoku Branch Lecture Meeting "Page 16 (published on July 16, 1986)

Claims (1)

[Claims] 1. A pure titanium thin plate for forming, produced by cold rolling and continuous annealing, having an average crystal grain size of 5 to 28 μm and between immediately after the annealing and before forming. A pure titanium thin plate for building material, which is not subjected to deformation exceeding the elastic limit and exhibits a yielding phenomenon when deformed at least in a direction perpendicular to the rolling direction.