JPS6233004A - Manufacture of titanium slab - Google Patents

Abstract

PURPOSE:To increase both elongation at the central part and a yield of a titanium slab by limiting rolling draft of the slab for one or more passes for bloom rolling. CONSTITUTION:A prescribed length from an end of a slab is rolled at a rolling draft and the slab is released from the draft at an intermediate point. Then, the prescribed length from another end of the slab is rolled at the same rolling draft, so that the slab end becomes only a pushed end whose central part in the thickness direction is elongated to form a bulgy shape and to eliminate folds. In that state, the slab is rolled at a heavy draft of DELTAh/H>=30% for one or more passes (where, DELTAh is a draft and H is a slab thickness before drafting). By that method, the slab end is shaped properly, so that the slab has a small crop loss L2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Separation) The present invention relates to a method for manufacturing titanium slabs with high yield.

(Prior art) The general method for manufacturing titanium slabs is to first melt titanium in a vacuum melting furnace to form a titanium ingot with a round cross section, then forge it to form it into a slab, and then separate it. A method is known in which the finished slab is formed into a slab of a predetermined size by lump rolling and then supplied to a rolling mill for thick plates and hot rolling. (Unexamined Japanese Patent Publication No. 57
By the way, titanium products are expensive, and hot working that minimizes clog loss after rolling is difficult. Manufacturing at high yields is of great economic importance.

Conventionally, as a yield countermeasure method during the production of titanium material slabs, for example, in the case of the method described in Japanese Patent Application Laid-Open No. 57-145944, titanium ingots are heated to a temperature of 700 to 980 degrees Celsius and then forged. By making the ingot into a flat ingot whose edges are 4 walls narrower than the center, the slab is rolled into a slab with relatively straight edges, which improves the shape of the slab edges, that is, the fishy tail. This can be said to be one of the effective ways to do so. There is also a proposal to use a special mold to obtain such a special shaped ingot at the casting stage without forging. (T￥f Publication No. 60-3950) However, these methods require sufficient time for the forging process, and due to the relationship between the size of the lump and the slab size to be obtained, each glofil It is necessary to forge an ingot and prepare a mold for six glazes.

(Problems to be Solved by the Invention) The present invention differs from these methods in that the titanium material is reduced by /1'!
By taking advantage of the characteristics and organically combining it with the rolling method,
The purpose is to obtain titanium material slabs with low crop loss, that is, high yield.

(Means for Solving the Problems) The feature of the present invention is to introduce a heated titanium ingot into a blooming process and to reduce the rate of at least -92 or more to Δh/H.
Applying a high rolling reduction of ≧30 degrees, and in addition to this method, applying a rolling reduction from the ends of the rolled material toward the center, releasing the rolling completely from the middle, or gradually reducing the rolling strip, and rolling from the other end. By using unidirectional rolling in a similar manner, a slab with shaped edges is obtained, resulting in a titanium material slab with less clog loss. (However, Δh is the rolling reduction amount, and H is the thickness of the slab before rolling.) In other words, in the case of conventionally rolling the entire titanium ingot,
In the method described in Publication No. 6-163001, etc., the rolling reduction amount is 1 to 25 inches/arm, and the rolling reduction f'z of 7'C against the gas added to the material to be rolled is relative. It is customary to reduce the size and form it into a predetermined size and shape by reciprocating rolling.

Further, a rolling method is adopted in which both ends of the material to be rolled are alternately pushed ends and pulled ends. For this reason, both crop ends of the slab are irregularly shaped and overlap occurs. Here, the push-in end is the tip portion that is bitten by the rolling mill. Further, the drawn end is the last part that comes out from the rolling roll, and as mentioned above, the end is irregular and curling occurs.

As a result of studies on the hot workability of titanium materials, the present invention has found that it has good hot workability, especially in the β-phase temperature range (usually 883°C or higher), and that it can be used under high pressure, which is not conventionally used in the rolling pass of the blooming process. By applying this to the entire upper, lower, and/or side surfaces, the stretching of the central part in the rolling direction is extremely large, and the central part is pushed out. It was discovered that the

The present invention will be specifically described below based on an embodiment shown in the drawings.

FIG. 1 shows the overall manufacturing process of the present invention, in which a titanium ingot A obtained by arc vacuum melting or the like is led to a forging process B to obtain a predetermined primary slab.

Next, it is reheated and supplied to the blooming rolling process C, where an etching pass is performed in the entire width direction of the slab S1. Next, a predetermined rolling reduction is applied in the thickness direction to obtain a titanium material slab Sst-shaped with a predetermined size and shape, and the titanium material slab is supplied to a thick plate rolling process or a thin plate rolling process. To explain each step, a titanium ingot is heated to 930 to 1000°C, and forged in a β-phase temperature range of 883°C or higher. In the rolling process, it is preferable to perform rolling under the same temperature conditions as in the forging process, and to perform an etching pass to improve the shape of the end corners by taking advantage of the hot working properties in this temperature range, especially the stretching properties of the material.

The above-mentioned etching pass may be performed using a vertical roll that can be driven, but in practice, upper and lower horizontal rolls that perform normal thickness reduction are sufficient, and especially when performing high-reduction rolling as described later, it is more difficult in terms of equipment. The latter is preferred.

On the other hand, the primary slab is rolled by the upper and lower horizontal rolls, as shown in FIG. 2, which compares the unidirectional high-reduction rolling method of the present invention with the normal rolling method. (■), release the rolling from the middle (■), and then perform the same rolling from the other end (■). As a result of this unidirectional rolling, the end of the slab becomes only a push-in end, and the central part in the thickness direction of the end face is elongated and has a swollen shape, and the entrainment disappears. At this stage and/or after that, the slab is rolled at least one pass or more, depending on the combination, with a high reduction of Δh/H≧30 (actually 30 to 40 inches) for each pass. As a result, the edges are shaped and are not accompanied by a large lonogloss as shown in Fig. 3-■.
Slabs with extremely low crop loss are manufactured.

As mentioned above, in JP-A-56-163001, etc., the amount of reduction (11 to 25 times/pass) is applied to the rolled material. However, in the present invention, by utilizing the hot working characteristics of titanium material in the β phase temperature range, it is possible to limit the reduction to a relatively small amount, but rather to apply a high pressure of 30 inches or more. By reducing the amount, there will be no problem with surface flaws, and the crop loss at the end of the slab will be reduced, resulting in a yield improvement effect.

The relationship between the amount of reduction/pass and the crop loss rate in rolling generally tends to be as shown in Figure 4, and the amount of reduction has a limit to the rolling ability, but a higher amount of reduction will cause more damage to the inside of the rolled slab. Due to the propagation of the rolling blade, the wrap-up (overlap) at the end of the slab is reduced and the shape is shaped. Particularly, when high pressure is applied in the β phase temperature range, hot workability (width expansion characteristics, stretching characteristics) improves. One reason is that the rolling temperature is high, which lowers the surface temperature and reduces width expansion. Even though
The central layer has a sufficiently high temperature and a wide width expansion, which is facilitated by high pressure.The average temperature is high, so the deformation resistance is small.Furthermore, due to the crystal structure, the β phase temperature range is body-centered cubic. Reasons include that there are many slip systems that contribute to plastic deformation.

Next, examples of the present invention are listed.

Example (1) ■-Next slab size Sl) 23×1300bX
2730 threat.

■Target slab size (St) 90tX1200b
X7300 4 □■ Pressure jt 80~
100 rpy'm/ノ枳 ■Unidirectional rolling (no) Example (2) ■-Next slab size C3t 230tX1300b
X2740L 94゜■Target slab size (82)
90tX1200bX740 Mel name■Reduction amount
80 to 100 islands/pass ■Unidirectional rolling (with) Table 1 (Comparison) (Effects of the invention) As explained above, titanium slabs can be produced at a high yield by applying the entire reduction amount in blooming according to the present invention. It can be manufactured with. The rolling according to the present invention takes advantage of the hot working characteristics of the titanium material especially in the β-phase temperature range, and is extremely effective when unidirectional rolling under high pressure is applied.

Although the shape of the material to be rolled is not specified, the effect is particularly great in the case of dog-shaped ingots or rolling conditions with a large reduction ratio.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the overall manufacturing process of the present invention, Fig. 2 is a diagram showing an example of unidirectional and high pressure rolling of the present invention in comparison with the all normal rolling method, and Fig. 3 is a diagram showing the unidirectional and high pressure rolling method of the present invention. FIG. 4 is a diagram showing the Crozzo shape in the case of high reduction rolling and normal rolling, and FIG. 4 is a diagram showing the relationship between the rolling reduction amount/pass and the Kronpross ratio. Figure 1 Low Rumor -9-(L Figure 3 ■--■ Reduction amount/) V

Claims (2)

[Claims] (1) Leading the heated titanium material slab to the blooming rolling process,
Titanium characterized by increasing the stretching of the central part in the rolling direction by applying a high pressure of Δh/H≧30% (Δh is the amount of reduction, H is the thickness of the slab before rolling) for at least one pass. Method of manufacturing slab materials. (2) Leading the heated titanium material slab to a blooming rolling process,
A high reduction of Δh/H≧30% (Δh is the amount of reduction, H is the thickness of the slab before rolling) is applied for at least one pass, and the reduction is applied from the edge of the rolled material toward the center, and the reduction is released midway. 1. A method for producing a titanium slab material, which comprises rolling the same material from the other end.