CN-116710582-B - Alpha+beta titanium alloy cast ingot for hot working

Abstract

The alpha+beta titanium alloy ingot for hot working has a chemical composition comprising, in mass%, 2.5-8.0% of Al, 0.5-3.0% of Fe, and an amount of O satisfying 0.02%. Ltoreq.O ] ([ Al ] - [ Mo ] - [ 0.5X [ Nb ] +1.0)/100 ([ X ] represents the content of element X in the unit of mass%, the balance being Ti and impurities, wherein the ratio L/S of the perimeter L (mm) of a cross section, which is a section perpendicular to the length direction, to the area S (mm 2 ) of the cross section is 0.010 or more, and the average grain diameter D of the structure at a position 10mm from the surface toward the central axis of the length direction of the alpha+beta titanium alloy ingot satisfies D10 mm and D+L/100 in a portion of 20-80% of the total length from one end face of the 2 end faces the other end faces of the alpha+beta titanium alloy ingot, and the thickness of the alpha+beta titanium alloy ingot is 80mm or less.

Inventors

• SEN JIANYI
• OKUI TOSHIYUKI
• NISHIYAMA SHINYA
• Yomoto Shotaro

Assignees

• 日本制铁株式会社

Dates

Publication Date

20260512

Application Date

20210302

Claims (2)

1. 1. An alpha + beta titanium alloy cast ingot for hot working is characterized in that, It has the following chemical composition: Contains, in mass percent Al:2.5~8.0%、 Fe:0.5~3.0%、 Sn:0~3.0%、 Zr:0~3.0%、 Mo:0~3.0%、 Si:0~3.00%、 Cu:0~3.0%、 0 To 3.0% of Nb, and An amount of O satisfying the following formula (1), the balance being Ti and impurities, The ratio L/S of the perimeter L (mm) of the cross section of the alpha+beta titanium alloy ingot which is vertical to the length direction relative to the area S (mm 2 ) of the cross section is more than 0.010, In a portion having a total length of 20 to 80% in the longitudinal direction of the alpha + beta titanium alloy ingot from one of the 2 end surfaces in the longitudinal direction of the alpha + beta titanium alloy ingot toward the other end surface, an average crystal grain diameter D of a casting structure at a position having a central axis of 10mm in the longitudinal direction of the alpha + beta titanium alloy ingot from the surface of the alpha + beta titanium alloy ingot satisfies D≤10 mm and D≤L/100, The thickness of the alpha + beta titanium alloy cast ingot is more than 80mm, 0.02% Or less of [ O ] < 0.5 x [ Mo ] -0.5 x [ Nb ] +1.0)/100. (1) Wherein [ X ] represents the content of element X when the unit is set to mass%.
2. 2. The α+β titanium alloy ingot for hot working according to claim 1, which contains 3.0% or less of each of Sn, zr, mo, cu and Nb in place of a part of Ti and 3.00% or less of Si.

Description

Alpha+beta titanium alloy cast ingot for hot working Technical Field The present invention relates to an α+β titanium alloy ingot for hot working. Background The process for producing an α+β titanium alloy rod generally includes a process for producing a titanium alloy ingot by melting and casting a sponge titanium, a master alloy, a titanium scrap, etc. as a melting raw material, a cogging process for forging or rolling a titanium alloy ingot by heating to the β domain, and a rolling process for producing a rod by heating to the β domain or the α+β domain. On the other hand, in order to reduce the cost, it is conceivable to omit the cogging step and directly roll the titanium alloy ingot to manufacture a bar. For example, patent document 1 discloses a method for producing a titanium ingot, which comprises a compression molding step of compression molding 1 or more selected from sponge titanium and titanium scraps with a secondary raw material containing an element necessary for adjusting the chemical composition to obtain a titanium briquette, and a melting step of irradiating the surface of the titanium briquette with an electron beam under reduced pressure of 1Pa or less to melt all of the titanium briquette to produce a titanium ingot. In the method for producing a titanium ingot described in patent document 1, the melting step includes a step of irradiating an arbitrary surface of the titanium briquette with an electron beam to melt a part of the surface in the thickness direction, and a step of irradiating an arbitrary other surface with an electron beam to melt at least an unmelted titanium briquette. In the method for producing a titanium ingot described in patent document 1, a titanium ingot having a plate shape with a thickness of 7 to 80mm, or a cylindrical shape having a circular cross section perpendicular to the longitudinal direction with a diameter of 10 to 80mm, or a polygonal cylindrical shape with a pentagon or more with an equivalent circle diameter of 10 to 80mm is produced. In addition, titanium alloy powder made of titanium alloy bar is used for manufacturing the material of the molding using a 3D printer. Patent document 2 discloses a technique of molding a metal powder as a material by a 3D printer. Prior art literature Patent literature Patent document 1 International publication No. 2019/26151 Patent document 2 Japanese patent application laid-open No. 2017-222899 Disclosure of Invention Problems to be solved by the invention However, patent document 1 discloses a preferred method for producing a thin titanium ingot having a thickness of 80mm or less, and the technique described in patent document 1 is a technique for producing a titanium ingot by irradiating the surface of a titanium compact with an electron beam to melt the titanium compact and then solidifying the melted titanium compact. When a large titanium ingot is produced by irradiating the surface of a titanium compact with an electron beam, it is necessary to increase the melting depth of the titanium compact by the electron beam. However, when the melting depth of the titanium briquette by the electron beam is increased, the cooling rate after melting is reduced, and the crystal grains become coarse. When the crystal grains are coarse, cracks or voids may be generated when the titanium alloy ingot is rolled into a bar, and deep defects may be formed on the surface of the bar. Thus, the technique described in patent document 1 has room for improvement. When a bar is produced by directly hot-rolling an ingot without a cogging step, there is a problem in that the surface properties of the bar are deteriorated due to a coarse cast structure, and the yield is lowered. Among the α+β type titanium alloys, particularly an alloy containing Al and O as α -stabilizing elements and Fe as β -stabilizing elements, since Fe diffuses rapidly and the solid solubility limit of Fe in the α phase is small, a film-like α phase may be precipitated in β grain boundaries during the phase transition from the β phase to the α+β phase. The film-like α phase precipitated at the β grain boundary may become a starting point of a crack in the α+β titanium alloy rod, and the yield may be reduced. Therefore, in order to omit the cogging step, it is necessary to manufacture an ingot having a reduced depth of surface defects similar to those of a bar obtained by rolling an ingot of a titanium alloy. Hereinafter, film-like α precipitated at β grain boundaries may be referred to as grain boundary α phase. In addition, when a titanium alloy rod has a deep defect, there is a case where the chemical composition of the powder of the titanium alloy produced from the titanium alloy rod having the defect left therein may be deviated, in addition to the fact that the yield is lowered to remove the defect and the production cost is increased. The raw material of the titanium alloy powder for the 3D printer may be produced by, for example, melting a bar of titanium