JPS603950A - Production of titanium slab - Google Patents

Abstract

PURPOSE:To produce easily a titanium slab having good quality at a low cost without requiring a rough forging stage by melting a square casting ingot of titanium which is tapered in the bottom and subjecting the molten titanium to blooming. CONSTITUTION:A casting mold of a rectangular cross sectional shape which has the side walls curving outward and in which the adjacent side walls are continuous by having a radius is used in the stage of vacuum melting and casting of titanium by a vacuum arc melting method, etc. A casting titanium ingot having roughly a square shape is efficiently produced without distortion of the side walls of the mold. A mold of a desired shape is disposed in the bottom or the bottom and top part of the casting mold to taper the end part of the casting ingot. The workability in rolling is much improved by the above-mentioned method, by which the crop loss of the slab is decreased and the titanium slab is produced at a good yield.

Description

[Detailed Description of the Invention] This invention does not require a rough forging process and is simple! The present invention relates to a method for manufacturing titanium slabs (the term "titanium" is used herein to include titanium alloys as well) at low cost and with good quality.

Conventionally, titanium slabs for producing titanium plate materials have generally been produced in the following manner.

Specifically, a vacuum arc double melting method is used in which briquettes made by compression molding titanium sponge are vacuum arc melted using a primary electrode, and the resulting ingot is vacuum arc melted again using a secondary electrode and 17. A round titanium ingot is made, and in order to minimize crop loss during disassembly and rolling, this round titanium ingot is roughly forged and its top (head) and bottom (bottom) parts are tapered. After forming the steel into a rectangular shape, it was subjected to blooming rolling to form a slab. FIG. 1 shows an outline of the process.

In this case, the reason why the titanium ingot made from titanium sponge is made into a circular cross section is because titanium has a high melting point and is an active material, so its melting and casting is done in a vacuum. Usually, the titanium is melted using an arc or the like in a vacuum chamber integrated with a water-cooled copper mold, but since the mold itself constitutes the vacuum chamber, its shape is, for example, The reason was that if the mold were square, the side walls of the mold would become distorted during high-temperature operation due to the pressure difference, making it impossible to continue the melting UJ manufacturing process.

However, in such conventional titanium slab manufacturing methods, it takes a long time of 10 to 15 hours to heat and maintain the titanium ingot at the forging temperature, and furthermore,
It has been strongly pointed out that the work efficiency is low, as it takes about an hour to forge the ingot into a rectangular shape with a tapered top and bottom.
This was a major cause of the increase in the manufacturing cost of titanium plates.

Furthermore, as mentioned above, if it takes a long time to forge the ingot, the temperature of the ingot will drop during that time, which is particularly noticeable during the final process, which is the teno-e forming of both ends of the ingot. There was also a major problem in that cracks would occur, making it impossible to obtain a sound titanium slab even after blooming. In other words, if such cracks remain in the titanium slab, it is not possible to produce a board with good properties through hot rolling.
In addition to requiring extremely troublesome work to remove the cracks using a grinder, chipping, etc., the yield drop due to cleaning the cracks was also significant, and this was also a major hindrance to reducing the cost of titanium plate products. .

From the above-mentioned viewpoint, the inventors of the present invention aimed to find a method for manufacturing high-quality titanium slabs at low cost using simple processing steps, and in particular, to find the most efficient method for achieving high efficiency in titanium slab manufacturing. As a result of various studies aimed at omitting the rough forging process, which is a hindrance, we found that (a) How many outward curves should be made for the mold when vacuum melting and casting titanium using the vacuum arc melting method, etc. For example, as shown in Fig. 2, □6 shows a case where the side walls are connected and the adjacent side walls are connected with a radius.1. Wow im
Than. ,. (b) With such a titanium ingot,
Normal blooming rolling is possible without any particular hindrance (C
) Placing a mold of the desired shape on the bottom part of the mold or between the tem part and the top part to give a taper to the end of the ingot will further improve the workability of rolling and will greatly reduce the slab crop loss. We have come to the knowledge shown in (a) to (c) above that titanium slabs can be manufactured with a small size and a high yield.

This invention was made based on the knowledge mentioned above, and is a vacuum melt casting method using a mold having a rectangular cross section, which is composed of outwardly curved side walls, and in which adjacent side walls are connected with a radius. By melting a square titanium ingot with a chi in at least one of the top and bottom parts and subjecting it to blooming rolling, a rough forging process is not required. It is characterized by the ability to produce high-quality titanium slabs with high efficiency.

In this invention, there is no particular limit to the degree of mold side wall curvature, the size of the radius between adjacent molds, or the slope of the taper of the top and bottom parts of the titanium ingot, and the size of the ingot and the mold An appropriate value may be selected in consideration of wall thickness, etc.

In addition, in order to improve rolling workability and minimize slab crop loss, it is ideal to have a tapered ingot at both the top and the ram. Even if one of them is provided with a taper only at the bottom part, especially considering the ease of manufacturing the ingot, a sufficient yield improvement effect can be obtained compared to the conventional round ingot. The cross-sectional shape of the ingot is rectangular with an oblateness of 1.5 or more than 1.5 (of course, the corners and sides are given a radius or 9 curves), which is easier to roll. - is preferable, but there is no problem even if it is a square with a flat side of one side.

3(A), (C) and (D) are schematic perspective views of the square titanium ingot according to the present invention, respectively.
It is preferable that the size of the chi/e in the width and thickness direction be in the range of 15 to 30% of the main body dimension (h) depending on the size of the ingot, and the taper in the width direction should be adjusted depending on the size of the ingot. Depending on the size of the ingot, it is best to taper within a range of 5 to 20% of the body size (b), and the taper in the thickness direction should be 3 to 20% of the body size (a) depending on the size of the ingot.
It is best to narrow it down within the range of 0 to 50%.

Next, the present invention will be explained using Examples and comparing with Comparative Examples.

Example First, the following chemical components corresponding to JIS TP-35:
Two types of titanium ingots (1) and (2) were produced by vacuum arc melting and casting.

■ An ingot having the shape shown in Fig. 4, t2:650mm.

W: 1000mm+W2: 85(h+m,
+l, : 2000 order, 12:300 am.

R: The long side is 2000 mm and the short side is 1500 mm.

r:200IIW.

Of things.

■ Diameter: 980 m111 + length: 20001
m round ingot.

Next, as a method of the present invention, the ingot of above (①) was used, and this was
After heating to 00℃, it is bloomed and rolled to a thickness of 20020.
A slab with a length of 0.975 mm and a length of 7900 mm was manufactured.

In addition, as a comparative method (conventional method), using the ingot of (■) above,
After heating this to 900℃, it is press-forged to make it square in cross section, and the top and bottom of the ingot are made of chi.
Then, by blooming and rolling, the thickness was 200200 mm and the length was 975 mm.

Manufactured a dragon slab.

When both slabs produced in this way were cooled to room temperature and examined for surface flaws, no major surface flaws were observed in the titanium slab produced by the method of the present invention, whereas in the titanium slab produced by the comparative method, no major surface flaws were observed. The titanium slab had a lot of side flow, sagging defects, and fold-in defects, and the surface quality was extremely poor.

Therefore, titanium slabs made by the method of the present invention were heated to 900°C after crop removal, and the titanium slabs made by the comparative method were heated to 900°C after removal of crops to remove surface defects using a planer, grinder, or chipping. After heating, each was hot-rolled, and the plate thickness was 4.5. ,
A hot rolled sheet was manufactured.

As a result of observing the surface condition of the hot-rolled titanium sheets obtained, it was found that the hot-rolled titanium sheets produced by the method of the present invention were in good condition with no flow generation at all, whereas the hot-rolled titanium sheets produced by the comparative method were not cleaned at the slab stage. Even though surface flaws were removed, underflow was observed, especially on the top and bottom parts.

Historically, when we investigated the yield of hot-rolled sheet products when the method of the present invention and the comparative method were applied, we found that the method of the present invention! 19
．． 7. The comparative method showed a value of 99.1.

In this example, as the method of the present invention, chi i? is applied only to the bottom part. We have only shown an example in which a --treated ingot is directly bloomed and rolled, but if the top part of such an ingot is also subjected to cino or - by short-time forging,
Since only 1/2 is applied, the temperature drop during forging is very small), there is little clog loss, and it goes without saying that a good rolling operation can be ensured.

As described above, according to the present invention, titanium slabs with no surface flaws can be manufactured with good workability without requiring a rough forging process, and hot-rolled titanium sheets with good properties can be produced at low cost. It brings about two useful effects, such as "industrial".

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram illustrating the conventional titanium slab manufacturing process, Fig. 2 is a schematic horizontal sectional view showing an example of a mold for vacuum melting and casting used in the method of the present invention, and Figs. FIG. 3 is a schematic perspective view of a rectangular titanium ingot to be manufactured;
Figure (A), Figure 3 (B), Figure 3 (C), Figure 3 (D)
4 shows the shape of a titanium ingot produced in an example of the present invention, and FIG.
i,) is its plan view, and No. 41 JCB) is its side view. Applicant Sumitomo Metal Industries Co., Ltd. Agent Kazuo Tomita and one other person Figure 3 (A) (B) Figure 4 (A) (B)

Claims (1)

[Claims] Cheeks are applied to at least the bottom part of the top and bottom parts using the vacuum melting M casting method, which uses a casting with a rectangular cross section that is composed of outwardly curved side walls and adjacent side walls are connected with a radius. A method for producing a titanium slab, characterized by melting a square J titanium ingot with - and subjecting it to blooming.