JPS63130753A - Manufacture of pure titanium plate reduced in anisotropy of 0.2% yield strength - Google Patents

Abstract

PURPOSE:To manufacture the titled plate by counteracting, by means of the subsequent hot rolling, material anisotropy generated by the slabbing of pure Ti and also by controlling anisotropy generated by hot rolling so as to carry out rolling by a simple process and then annealing. CONSTITUTION:An ingot of pure Ti or a dummy slab (thickness t0), prepared by forging, of pure Ti is heated to a beta-phase region of <=970 deg.C in a slabbing stage, which is rolled at >=30% draft to be formed into a cold slab (thickness t1). Subsequently, this cold slab is reheated to a temp. of beta-transformation or below and then is rolled (thickness t2) so that final-rolling direction in hot rolling is perpendicular to the rolling direction in slabbing and a reduction cross ratio (t1/t2:t0/t1) is regulated to a range of 0.5-3.0. Successively, this rolled plate is cooled and then annealed.

Description

[Detailed Description of the Invention] (Field of Application in Pressure Pressure) The present invention relates to a method for producing a pure titanium hot-rolled plate with less anisotropy in 0°2% proof stress. .

(Prior Art) Pure titanium hot-rolled sheets have excellent corrosion resistance in the atmosphere or seawater, so their use as structural materials in pipe-type environments is increasing. Due to the strong anisotropy of the 2% yield strength, the material is often not used effectively.

The cause of material anisotropy in pure titanium is said to be due to the aggregate fibers formed during its manufacturing process, and measures are being taken to reduce the anisotropy by controlling heating and rolling conditions.

For example, as in JP-A-59-1661, a pure titanium plate that has been hot- or cold-rolled and then annealed is cold-rolled at a light reduction ratio, or the lightly-reduced plate is further annealed to a mild degree. There is a method for producing pure titanium hot-rolled sheets with less anisotropy. There is also a method of reducing the anisotropy of titanium alloys by cross rolling, as disclosed in Japanese Patent Publication No. 60-230968.

However, these methods do not sufficiently consider the manufacturing history before hot rolling, and attempt to control only the post-process, and are not efficient manufacturing methods.

(Problems to be Solved by the Invention) The present invention applies annealing after rolling to a pure titanium hot-rolled sheet in a simple process to produce a pure titanium hot-rolled sheet with less anisotropy of 0.2% i + M force. The purpose is the development of law.

(Means for Solving the Problems) The present invention was discovered as a result of numerous experiments in order to solve the above problems, and the material obtained under hot rolling conditions is This is based on the fact that the heating and rolling conditions at this stage are carried over to subsequent processes.

In other words, by canceling out the material anisotropy caused by blooming in the subsequent hot rolling, and at the same time controlling the anisotropy caused by hot rolling, the anisotropy of the 0.2% proof stress is reduced. This invention is based on the knowledge that pure titanium can be obtained, and the present invention involves heating a rope titanium section or a slab manufactured by forging to a β phase region of 970°C or less with a blooming mill, and then rolling it at a reduction rate of 30% or more. After applying a reduction of , it is made into a cold piece, then reheated to a temperature below β transformation, and rolled in a hot rolling process so that the final rolling direction of hot rolling is perpendicular to the rolling direction of blooming rolling, and is characterized in that it is rolled with a rolling cross ratio in the range of 0.5 to 3.0, then cooled, and then annealed.
2% This is a method for producing a pure titanium plate with little power anisotropy.

The present invention will be explained in detail below.

The present invention uses rough slabs made by melting cast slabs in a vacuum or by forging, and then performs blooming and hot rolling to achieve a low anisotropy of 0.2% proof stress. This was obtained by examining the manufacturing efficiency of obtaining pure titanium plates.

The first feature of the present invention is to heat the slab or slab in the β first region during the blooming of pure titanium, and to apply a rolling reduction of 30% or more. This reduction in blooming is necessary in order to carry over the texture generated by rolling to subsequent hot rolling.

The texture generated when heating to the β phase region and blooming rolling is such that the C side of the α phase close-packed hexagonal crystal is strongly concentrated in the crushing angle direction (as a result of accumulation in an inclined direction, the material anisotropy is This can be effectively used in combination with the next hot rolling process to reduce anisotropy.The reduction rate in this blooming rolling must be at least 30%. If it is less than 30%, a sufficient texture cannot be formed during rolling.

In addition, if the heating temperature exceeds 970°C, the crystal grains will become coarse, so it is desirable to set the heating temperature to 970°C or less, and when the heating temperature is in the α phase region, the material anisotropy due to the condensation region generated by blooming. This makes it difficult to create an isotropic material in combination with the next process.

Next, the second configuration of the present invention is that the rolling direction of the final rolling during hot rolling after blooming is rolled in a direction perpendicular to the rolling direction of blooming, and the rolling gong cross ratio at that time is However, from 0.5
The purpose is to roll it so that it becomes 3.0.

Here, the rolling direction of hot rolling is defined as follows: O L direction rolling: The final rolling direction of hot rolling is the same as the blooming root - T direction rolling: The final rolling direction of hot rolling is Block rolling direction and orthogonal rolling cross ratio: Reduction ratio in the final rolling direction of hot rolling/reduction ratio at the time of offer The above rolling direction is shown in FIG. 1.

Figure 1 shows cross rolling in the case of L direction rolling, and (B) shows T.
It shows cross rolling of directional rolling.

In this case, the rolling cross ratios of L direction rolling and T direction rolling are as shown in equations (1) and (2), respectively.

If the rolling direction in hot rolling is perpendicular to the blooming direction, the texture of the blooming rolling will be canceled out, but if only the T-direction rolling is performed without widening, the final Due to the strong reduction of the sashimi due to rolling at this stage, the anisogata becomes thicker.

Therefore, in the hot rolling after blooming, it is necessary to perform cross rolling in order to cancel out the texture of the blooming and at the same time make the texture produced in the hot rolling uniform.

In this case, the anisotropy of 0.2% proof stress is calculated as [value in the direction perpendicular to the final rolling direction (T direction value)/value parallel to the final rolling direction (L
direction value)], and aiming for the tolerance range to be 1.05 or less, perform rolling in the T direction and set the rolling cross ratio to 0.5.
A value of ~3.0 is appropriate.

In this case, the reason why the T-direction value/L-direction value is set at 1805 or less is to make full use of the material properties in designing the package.

On the other hand, in the case of L direction rolling, the T direction value of 02% proof stress/
Although it is possible to obtain an L direction value of 1.05 or less by setting the cross ratio to 0.4 or less, such rolling is inefficient on a seedling seat.

Figure 2 shows the relationship between the rolling direction, cross rolling ratio, and anisotropy of 0.2% proof stress. 0.5-3.
By rolling within the range of 0.0%, it is possible to obtain a pure titanium hot-rolled sheet with less resistance by 0.2%.

Suitable for manufacturing pure titanium hot-rolled sheets with little force anisotropy.

As described above, in the present invention, a pure titanium slab or a slab manufactured by forging is subjected to β phase region hot blooming rolling, and then α
Heating in phase region and rolling in T direction, and cross ratio 0.5~
By rolling at 3.0, it is possible to produce a pure titanium plate with a 0.2% yield strength and less anisotropy.

(Example) Table 1 shows the composition of a pure titanium hot-rolled plate that was melted in a vacuum arter melting furnace, forged, then bloomed, and then hot-rolled. , shows the mechanical properties of the pure titanium plate after hot rolling and annealing.

As is clear from these experimental results, in the blooming rolling process, the β phase region is heated and then reduced by a reduction rate of 30% or more to form a cold piece, and then in the hot rolling process, the temperature is lowered to below the β transformation point. After heating, rolling is performed in the T direction, and the cross ratio is 0.5 to 3.
0.2% proof stress anisotropy (effect of the invention) By rolling the slab in the β range in a blooming process and then cooling it, and then annealing it, The titanium powder is cooled and heated to below the β transformation point in a hot rolling process so that the final rolling direction crosses the blooming direction, producing pure titanium with a 0.2% yield strength and low anisotropy. It is possible to do so, and its industrial effects are great.

[Brief explanation of the drawing]

Figure 1 (B) is a schematic diagram showing the definition of the rolling method, Figure 2
The figure is a chart showing the relationship between the rolling direction, cross rolling, and the anisotropy of 0.2% proof stress.

Claims (1)

[Claims] Pure titanium slab or rough piece manufactured by forging (thickness: t
_0) is heated to the β phase region of 970°C or less with a blooming mill root, and then rolled at a reduction rate of 30% or more to obtain a cold piece (thickness: t_1).
After that, it is reheated to a temperature below the β transformation point, and rolled in a hot rolling process so that the final rolling direction of hot rolling is perpendicular to the rolling direction of blooming rolling (thickness: t_2), and , the rolling cross ratio at that time (t_1/t_2:t_0/t_1)
A method for producing a pure titanium plate having a 0.2% proof stress and low anisotropy, which comprises rolling the plate to a range of 0.5 to 3.0, cooling it, and then annealing it.