JPH0771681B2 - Method for manufacturing titanium slab - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a titanium slab, and more specifically, when directly slab-rolling a cylindrical titanium ingot without forging, the diameter of the ingot is suppressed while suppressing the occurrence of wrinkle defects as much as possible. The present invention relates to a method of manufacturing a wider titanium slab.

[0002]

2. Description of the Related Art Since titanium has a high reactivity with oxygen and nitrogen in the atmosphere, it is generally cast into a cylindrical ingot by a vacuum arc melting method or the like. As a method of forming a cylindrical titanium ingot into a slab, a method by forging or a method of forging to some extent and then performing slab rolling is known. However, the forging work has a problem that productivity is low and cost is high, and the forging material has many surface defects.

Therefore, a method of directly forming the cylindrical titanium ingot into a slab by slab rolling without forging has been studied. However, slab rolling has a problem that it is very difficult to form a slab wider than the diameter of the ingot, because the cylindrical titanium ingot is mainly rolled in the axial direction. .

Further, the slab directly formed by slab rolling has a problem that streaky wrinkles having a depth of about 5 to 10 mm are likely to occur on the side surfaces of the corners, and the work for removing the wrinkles is required.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and directly suppresses the occurrence of wrinkle defects while directly separating a slab wider than the diameter from a cylindrical titanium ingot. It is intended to provide a method for producing a titanium slab that can be obtained by ingot rolling.

[0006]

The present invention which has achieved the above object is a method for directly slab-rolling a cylindrical titanium ingot to produce a titanium slab having a width wider than the diameter of the ingot. At a temperature above the transformation point and at a temperature that is as low as possible, and at a temperature that does not cut the transformation point, reduce the thickness by strong reduction while applying a certain proportion of width reduction to create a rectangular shape early The purpose is to perform thickness reduction while gradually widening the width.

[0007]

FUNCTION AND EXAMPLE When the cylindrical titanium ingot is slab-rolled without forging, the surface in contact with the H roll or the V roll is deformed so as to be elongated in the length direction. A portion of the V roll that does not contact any of the rolls remains in an arc shape, and such an arc portion is crushed in the free direction. That is, in the circumferential surface of the cylindrical titanium ingot, the contact portion with the roll is mainly rolled in the axial direction, while the non-contact portion is mainly rolled in the circumferential direction, such that the rolling direction is biased. It is considered to be the cause of wrinkle defects.

[0008] Therefore, the inventors of the present invention, for the purpose of minimizing the non-contact portion with the roll in the initial stage of slabbing and rolling, after soaking, first apply a certain proportion of width reduction and strongly reduce in the thickness direction. A method for producing a slab wider than the diameter of the cylindrical ingot by making the cross-section into a rectangular shape at an early stage, then gradually reducing the width while gradually widening the width, and finally performing finish rolling was investigated.

Tests carried out to set various conditions in the manufacturing method according to the present invention will be specifically described below.

The cylindrical titanium ingot has a diameter of 840 mm,
A slab having a length of 2500 mm and various rolling conditions, soaking temperature, and soaking time were manufactured by the rolling mill shown in Table 1, and the width expansion amount and the state of wrinkle defects were examined.

[0011]

[Table 1] Next, Tables 2 and 3 show the relationship between rolling conditions and the occurrence of wrinkle defects.

[0012]

[Table 2]

[0013]

[Table 3]

Performing a certain width reduction in the initial stage of the slabbing is effective in suppressing the occurrence of wrinkles and, while performing a width reduction of 7 to 17% per pass before widening the width. It can be seen that performing a reduction of about 50% in total has a great effect on the suppression of wrinkle defects.

<Example 1> Diameter 840 mm, length 2500
A slab having a thickness of 150 mm and a width of 870 mm was finished with the rolling mill shown in Table 1 using a cylindrical titanium ingot of mm. The pass schedule is shown in Table 4.

[0016]

[Table 4] The slab thus obtained has a wrinkle flaw of 4 mm or less and an area ratio of 50% or less.

The transformation point of pure titanium is 883 ° C.,
Below the transformation point, it is a dense hexagonal crystal with few slip planes,
Since it is a body-centered cubic crystal with many slip planes above the transformation point,
It is effective to suppress the generation of wrinkles and flaws by soaking the material above the transformation point and rolling at a temperature that does not cut the transformation point. However, if the soaking temperature is too high or the soaking time is too long, the crystal grains may be coarsened and wrinkles may increase. Figure 1
4 is a graph showing the state of wrinkle defects when slabs are manufactured under No. 4 rolling conditions shown in Table 2 after soaking under various conditions.

From the result of FIG. 1, the soaking temperature is 900 to 100.
0 degreeC is preferable, More preferably, it is 920-980 degreeC, and soaking | uniform-heating time is 6 hours or more, More preferably, it is 10-14 hours.

In the present invention, the cylindrical titanium ingot means
The cross-sectional shape is not necessarily limited to a perfect circle, and includes those having an elliptical shape, an oval shape, an oval shape, a substantially circular shape, and the like, and includes various titanium alloys other than pure titanium.

As described above, the characteristic feature of this embodiment is that the soaking is carried out at a temperature as low as possible, which is higher than the transformation point of titanium, and at a temperature which does not cut the transformation point, it is 50 mm in the width direction in the initial stage.
(59%) reduction at the same time, 1 pass 6 in the thickness direction
0 to 100 mm (7 to 17%) of strong reduction is applied, for a total of 41
A 0 mm (49%) reduction is applied to form a rectangular slab at an early stage, and the rectangular slab is gradually expanded in width from the middle stage and thereafter, and finished by performing a thickness reduction.

[0021]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, it is possible to obtain a slab having a width wider than the diameter directly from a cylindrical titanium ingot by directly agglomerating while suppressing the occurrence of wrinkle defects as much as possible. A manufacturing method can now be provided.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the soaking temperature and the occurrence of wrinkle defects.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Koyama 1 Kanazawa-machi, Kakogawa City, Hyogo Prefecture Kamido Steel Works, Ltd. Kakogawa Steel Works (72) Masato Fukuda 1 Kanazawa-machi, Kakogawa City, Hyogo Prefecture Kamido Co., Ltd. Steel Works Kakogawa Steel Works (72) Inventor Haruhiro Inaba 1 Kanazawa-cho, Kakogawa City, Hyogo Prefecture Kado Steel Works Kakogawa Steel Works (56) Reference JP-A 63-215303 (JP, A) JP Sho 62 -227506 (JP, A)

Claims (1)

[Claims] 1. A method for directly slabbing a cylindrical titanium ingot to produce a titanium slab having a width wider than the diameter of the ingot, which is soaked at a temperature as low as possible above the transformation point of titanium. Manufacture of a titanium slab characterized by performing a thickness reduction by applying a width reduction while applying a width reduction at a temperature that does not cut the transformation point to form a rectangular columnar cross section, and then gradually widening the width while performing a thickness reduction. Method.