JPS61108407A - Hot rolling method of alpha+beta, beta type titanium alloy - Google Patents

Abstract

PURPOSE:To prevent surface cracking, generating in hot rolling, by heating an alpha+beta, beta type titanium alloy in the atmosphere of a specific partial pressure of oxygen, before rolling it into the prescribed dimensions. CONSTITUTION:A slab of alpha+beta, beta type titanium alloy is heated to a specific temperature in the atmosphere of a <=0.02atm partial pressure of oxygen, by using a vacuum furnace or a furnace of Ar or He, etc. atmosphere. Next, the slab is hot rolled into a hot rolled sheet of prescribed thickness. By this method, as the formations of oxidized scales and oxygen-enriched layer are remarkably restricted, the surface cracking, generating in hot rolling, is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for hot rolling α-10β and β-type titanium alloys, and an object thereof is to provide a titanium alloy hot-rolled plate with excellent surface properties. shall be.

[Conventional technology]

In the production of hot-rolled sheets of α+β and β-type titanium alloys,
Improving the uniformity of the structure and improving mechanical properties have long been issues, and various studies have been conducted on thick plate rolling and hot rolling methods.
ing. The inventors have discovered that applying a sufficiently strong reduction in a low temperature range is effective in improving the uniformity of the structure and improving the mechanical properties of hot-rolled sheets of α-10β and β-type titanium alloys. It has been made clear.

However, α+β and β-type titanium alloys have poor hot workability;
When strong reduction in low temperature range is applied, there is a drawback that surface cracks occur in hot rolled sheets.

[Summary of the invention]

The present invention has been made to improve the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide a hot rolling method that does not cause surface cracks.

As a result of investigating the hot workability of α+β and β-type titanium alloys, the inventors found that the hot workability (intrinsic workability) of these materials themselves was sufficiently good, and it was found that the hot workability (intrinsic workability) of these materials themselves was sufficiently good. There is no problem with hot workability when hot rolling, and the surface crack f′L during hot rolling is caused by surface oxidation during rolling heating of the titanium alloy slab. It was discovered that this surface ratio can be controlled by controlling the atmosphere.

That is, α+β during thick plate rolling and hot rolling.

A batch furnace or a continuous furnace is usually used to heat β-type titanium alloy slabs, and the heating atmosphere is an oxidizing atmosphere to prevent hydrogen absorption during slab heating. As a result, oxide scale and an oxygen-enriched layer are formed on the surface of the slab, which increases the susceptibility to surface cracking during hot rolling.

The invention was based on this knowledge, and by controlling the heating atmosphere during rolling heating, the formation of oxide scale and oxygen-enriched layer on the slab surface was suppressed, thereby preventing surface cracking during hot rolling. It is something.

In the present invention, the heating atmosphere for rolling heating is set to an oxygen partial pressure of 0.
Limited to 0.02 Atm or less. This is because in an atmosphere with an oxygen partial pressure exceeding this, it is not possible to suppress the generation of oxide scale on the slab surface, and it is not possible to reduce surface cracking during hot rolling.

The heating temperature and heating time at this time are α+β.

It may be selected appropriately depending on the type of β-type titanium alloy, the capacity of the rolling equipment, the thickness of the slab, etc., and there is no limitation, but excellent mechanical properties can be obtained by applying strong reduction in a low temperature range as described above. I can do it.

In addition, a heating furnace that can control the oxygen partial pressure is used, such as a vacuum furnace or a t! It is carried out in an Ar or He atmosphere furnace.

If hot rolling is performed after heating to a predetermined temperature K under the nine conditions described above, a hot-rolled plate without surface cracks can be obtained.

The pressure conditions for this titanium alloy slater are also α+β.

It can be freely selected depending on the type and material properties of the β alloy, the capacity of the rolling equipment, etc. and is not specified.ρs1 As mentioned above, excellent mechanical properties can be obtained by strong rolling at low temperatures. Select conditions as appropriate depending on the purpose.

〔Example〕

Examples are shown below. As shown in Table 1, Ti-64At-4%V alloy, which is a typical α+β type titanium alloy, and 'ri-13%V-114Cr-, which is a typical β-type titanium alloy. The slab thickness of the rolled material using the uninvented method using 3% A1 alloy is 14
．． The slab was manufactured by forging an ingot with a diameter of 550 m in the β range. In hot rolling, each of the above slabs was rolled at ft950°O (Ti-696At-4
%V alloy), 980°0 (Ti-13%V-11%cr
-: lAA alloy], hot rolled to 32fi
Finished in a thick rolled plate. The rolling reduction rate for one bath was approximately 10 times, and the finishing temperature was varied from 650°0 to 900°0.The surface texture of the rolled plate included the length of surface cracks with a depth of 0.5 m or more in a surface area of 100 crR. The evaluation was made by visually measuring. Table 2 shows the relationship between heating conditions and surface texture. By heating the slab in an atmosphere with an oxygen partial pressure of 0.02 Atm or less using a vacuum furnace or an Ar or He atmosphere furnace, the surface properties of α+β and β type titanium alloy hot-rolled sheets can be significantly improved. [Effects of the Invention] As explained above, according to the method of the present invention, it is possible to obtain an excellent hot-rolled sheet of α+β, β-type titanium alloy with no surface crack n.

It should be noted that the method of the present invention was discovered in the production of hot rolled plates, or even if a round bar or the like is produced by hot forging as a hot working process using bloom or billet as the material, the hot rolling method of the present invention is complied with. 〇Patent applicant Nippon Kokan Co., Ltd. Nippon Kokan Co., Ltd. Nippon Mining Co., Ltd.

Claims (1)

[Claims] Hot rolling of α + β, β type titanium alloy, characterized in that the α + β, β type titanium alloy material is heated in an atmosphere with an oxygen partial pressure of 0.02 atm or less, and then rolled to a predetermined size. Method.