TWI626093B - Titanium composite and titanium for hot rolling - Google Patents

Abstract

A titanium composite material (1) comprising: an inner layer (5) containing industrial pure titanium or a titanium alloy; and a surface layer (3) formed on a surface of at least one of the inner layers (5) and having an inner layer ( 5) a different chemical composition; and an intermediate layer formed between the inner layer (5) and the surface layer (3), having a chemical composition different from the inner layer (5); and the surface layer (3) having a thickness of 2 μm or more, And the ratio of the total thickness is 40% or less per one-sided layer; the thickness of the intermediate layer is 0.5 μm or more. The chemical composition of the surface layer (3) is one or more selected from the group consisting of Fe, Cr, Ni, Al, and Zr: 0.08 to 1.0%, and the balance: titanium and impurities. Although the titanium composite material is inexpensive, it has the desired fatigue resistance.

Description

Titanium composite and titanium for hot rolling

The present invention relates to a titanium composite material and a titanium material for hot rolling.

Titanium is excellent in properties such as corrosion resistance, oxidation resistance, fatigue resistance, hydrogen embrittlement resistance, and neutron blocking properties. These properties can be achieved by the addition of various alloying elements in the titanium.

Industrial cold-rolled titanium sheets (for example, industrial pure titanium cold-rolled sheets), such as plate heat exchangers and FC separators, are used for forming a sheet into a specific shape, and its use is expanding. Therefore, in addition to the formability, the industrial cold-rolled titanium sheet is required to have a reduced thickness and a high load environment (at a high load) due to an increase in fatigue strength.

On the other hand, as with other metal materials, pure titanium also has an inverse relationship between ductility and strength (fatigue strength) which governs its formability.

In Japanese Laid-Open Patent Publication No. 2008-195994 (Patent Document 1), it is disclosed that a titanium product composed of any one of pure titanium, an α-type titanium alloy, a β-type titanium alloy, or an α + β-type titanium alloy is used as a titanium product. The processing object is subjected to plasma nitriding to form a hardened layer on the surface of the object to be processed, and the object to be treated after the plasma nitriding treatment is one or two. The above-mentioned fine particles colliding with the fine particles collide and remove the compound layer present on the surface of the hardened layer, thereby performing surface modification of the titanium product to improve the fatigue strength.

Japanese Laid-Open Patent Publication No. 2013-76110 (Patent Document 2) discloses a surface treatment method of a substrate composed of a titanium alloy and titanium in the following steps: a surface of a substrate composed of a titanium alloy and titanium a step A of performing a microbeading treatment, a step B of performing a first heat treatment in the temperature zone T1, a step C of performing a second heat treatment in the temperature zone T2, and a step D of performing a third heat treatment in the temperature zone T3; In addition to the relationship of T1>T2>T3, T1 is set to 900~1000°C. Specifically, the surface treatment method is formed by sequentially forming an amorphous layer, a fine particle layer (α phase, particle diameter: about 300 nm), and a submicron layer layer from the surface side due to the vicinity of the surface of the titanium material. (α phase, particle diameter: about 500 nm), microparticle layer (β phase, particle diameter: about 3000 nm), and the fatigue strength was improved.

Titanium is generally produced by the method shown below. First, titanium oxide as a raw material is chlorinated to form titanium tetrachloride by a Kroll method, and then reduced by magnesium or sodium, whereby a sponge-like metal titanium (sponge titanium) is produced in a bulk form. This sponge titanium was press-formed to form a titanium consumable electrode, and the titanium consumable electrode was subjected to vacuum arc melting as an electrode to produce a titanium ingot. At this time, a titanium alloy ingot is produced by adding an alloying element as necessary. Then, the titanium alloy ingot is divided, forged, and rolled to form a titanium flat embryo, and then the titanium flat blank is further subjected to hot rolling, annealing, pickling, cold rolling, and vacuum heat treatment to produce a titanium thin plate.

Further, as a method for producing a titanium thin plate, a titanium ingot is divided into pieces, hydrocrushed, dehydrogenated, powder disintegrated, and classified to produce a titanium powder, and the titanium powder is produced by powder rolling, sintering, and cold rolling. The method is known.

Japanese Laid-Open Patent Publication No. 2011-42828 (Patent Document 3) discloses a method of producing a titanium thin plate directly from a titanium ingot but from a titanium sponge, and producing a titanium thin plate from the obtained titanium powder. The method for producing a thin plate is to form a sintered thin plate by forming a viscous composition containing a titanium metal powder, a binder, a plasticizer, and a solvent into a thin plate-like sintered body, and compacting the sintered sheet to produce a sintered compact. The thin plate is sintered, and the sintered compacted sheet is further sintered, wherein the sintered sheet has a breaking elongation of 0.4% or more, a density ratio of 80% or more, and a density ratio of the sintered compacted board of 90% or more.

Japanese Laid-Open Patent Publication No. 2014-19945 (Patent Document 4) discloses that a titanium alloy powder made of a titanium alloy scrap or a titanium alloy ingot is appropriately added with iron powder, chromium powder or copper powder to form a composite powder. The composite powder is encapsulated and extruded as carbon steel, and the encapsulation of the surface of the obtained round rod is dissolved and removed, and then subjected to a solution treatment or a solution treatment and a aging treatment, and is produced by a powder method. A method of high quality titanium alloy.

In JP-A-2001-131609 (Patent Document 5), it has been disclosed that a titanium sponge powder is filled in a copper-clad form, and then subjected to inter-temperature extrusion processing at an extrusion ratio of 1.5 or more and an extrusion temperature of 700 ° C or lower. Further, the outer peripheral processing for removing the outer copper is performed, and 20% or more of the entire length of the grain boundary of the molded body is a metal contact titanium molded body.

When the hot-rolled material is hot-rolled, when the hot-rolled material is a so-called difficult-to-machine material having a high heat-delay resistance such as pure titanium or a titanium alloy, the roll is rolled into The technology of thin sheets and the method of rolling sheets are well known. The laminating method refers to a method in which a core material such as a titanium alloy having poor workability is coated with a coating material such as carbon steel having good workability and is hot-rolled.

Specifically, for example, a release agent is applied to the surface of the core material, and at least the upper and lower surfaces thereof are coated with the covering material, or the peripheral surfaces thereof are covered with a spacer other than the upper and lower surfaces, and the surrounding portions are welded and combined. Hot rolling. In the lamination rolling, the core material of the rolled material is coated with a covering material and then hot rolled. Therefore, the surface of the core material does not directly contact the cold medium (atmosphere or roll), and the temperature of the core material can be suppressed from being lowered, so that even a core material having poor workability can be manufactured.

Japanese Patent Laid-Open Publication No. 63-207401 (Patent Document 6), a composition has been disclosed a method of coating a sealed box; JP 09-136102 (Patent Document 7), has been disclosed to ^10-3 A A method of producing a sealed coating box by sealing a covering material at a vacuum level of a Torr or higher is disclosed in Japanese Laid-Open Patent Publication No. Hei 11-057810 (Patent Document 8), which is coated with carbon steel (coated material). A method of manufacturing a sealed coated box by sealing with a high energy density welding under a vacuum of 10 ^-2 Torr or less.

On the other hand, as a method of manufacturing a material having high corrosion resistance at a low cost, a method of joining a titanium material to a surface of a material of a base material is known.

Japanese Patent Publication No. 08-141754 (Patent Document 9) discloses that a steel material is used as a base material, and titanium or a titanium alloy is used as a laminate, and the joint surface of the base material and the laminate is vacuum-exhausted and then welded. A method of producing a titanium-clad steel sheet in which a flat blank for rolling is combined and a flat-sheath is joined by hot rolling.

Japanese Laid-Open Patent Publication No. Hei 11-170076 (Patent Document 10) discloses that a surface of a base material steel material containing 0.03% by mass or more of carbon is separated by a content of pure nickel, pure iron, and carbon of 0.01% by mass. After the titanium foil is laminated and laminated with a thickness of 20 μm or more, which is formed of any of the following low carbon steels, the laser beam is irradiated from either side of the lamination direction, and at least the edge of the titanium foil is adjacent to the edge. A method of manufacturing a titanium-coated steel material by melting and joining the base material over the entire circumference.

In Japanese Laid-Open Patent Publication No. 2015-045040 (Patent Document 11), a method of forming a dense titanium material (titanium ingot) which is formed into a surface of a porous titanium material (sponge titanium) which is formed into an ingot shape is exemplified. A titanium ingot having a surface layer of dense titanium is produced by electron beam melting under vacuum, and hot rolled and cold rolled, and a dense titanium material (titanium ingot) is produced with very little energy; The titanium material (titanium ingot) has a porous portion in which a porous titanium material is formed into an ingot shape, and a dense coating portion which is made of dense titanium and covers all surfaces of the porous portion.

Japanese Patent Publication No. 62-270277 (Patent Document 12) describes the surface effect treatment of an automobile engine component by spraying.

[prior technical literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2008-195994

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2013-76110

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2011-42828

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2014-19945

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2001-131609

[Patent Document 6] JP-A-63-207401

[Patent Document 7] Japanese Patent Laid-Open No. 09-136102

[Patent Document 8] Japanese Patent Laid-Open No. Hei 11-057810

[Patent Document 9] Japanese Patent Publication No. 08-141754

[Patent Document 10] Japanese Patent Laid-Open No. Hei 11-170076

[Patent Document 11] JP-A-2015-045040

[Patent Document 12] Japanese Laid-Open Patent Publication No. 62-270277

According to the method disclosed in Patent Document 1, since the solid solution strengthening energy is high and C and N are used for the formation of the hardened layer, if it is solid-solved, it becomes hard, and although the fatigue strength can be improved, the sharp ductility is caused. Reduced, poor formability.

Moreover, according to the results of the study by the inventors of the present invention, it is not easy to improve the formability by the surface treatment method disclosed in Patent Document 2.

In addition, the disclosures disclosed in Patent Document 1 and Patent Document 2 It is necessary to carry out special surface treatment of titanium materials, and the increase in manufacturing cost is inevitable.

In the prior art, when a titanium material is produced by hot working, a sponge titanium is press-formed into a titanium consumable electrode, and the titanium consumable electrode is used as an electrode to perform vacuum arc melting to produce a titanium ingot, and then the titanium ingot is further divided, The titanium flat embryo is formed by forging and rolling, and the titanium flat blank is further subjected to hot rolling, annealing, pickling, and cold rolling to complete the production.

In this case, it is necessary to add a step of melting titanium to produce a titanium ingot. Although a method of producing titanium powder by powder rolling, sintering, and cold rolling is also known, a method of producing titanium powder from a titanium ingot is required to add a step of melting titanium.

In the method for producing a titanium material from titanium powder, even if it is not used as a raw material without using a high-priced titanium powder, the obtained titanium material becomes very expensive. The methods disclosed in Patent Document 6 to Patent Document 7 are also the same.

In the lamination rolling, the core material coated with the covering material is in any case a flat embryo or an ingot, and it is not possible to reduce the manufacturing cost by a melting step or a high-priced titanium powder as a raw material.

In Patent Document 11, a dense titanium material can be produced with very little energy. However, it is required to melt the surface of the sponge titanium formed into an ingot shape, and the dense titanium surface layer portion and the inner composition are the same kind of pure titanium or titanium. In the alloy, for example, the titanium alloy layer is formed uniformly and over a wide range only in the surface layer portion, and the manufacturing cost cannot be reduced.

On the other hand, the base material can be manufactured with low-cost corrosion-resistant materials. The surface is bonded to a material made of titanium or a titanium alloy, and most of the base material is steel. Therefore, if the titanium layer on the surface is lost, the corrosion resistance is impaired. It is assumed that the base material is also made of titanium, and as long as the titanium material produced by the general manufacturing steps is used, a fundamental cost improvement cannot be expected. Therefore, the present inventors have considered that an alloy layer containing a specific alloying element is provided on the surface layer of a flat embryo composed of industrial pure titanium or a titanium alloy, and a titanium material excellent in cost and excellent in specific properties is obtained.

As in Patent Document 12, a melting method is a method in which a metal, a ceramic, or the like is melted and sprayed onto a surface of a titanium material to form a film. When the film is formed according to this method, the formation of pores in the film is inevitable. Usually, in order to avoid oxidation of the film during the spraying, the film is sprayed while being shielded with an inert gas. These inert gases are drawn into the pores of the membrane. The pores containing such an inert gas are not pressed by heat processing or the like. Further, in the production of titanium, vacuum heat treatment is generally carried out. However, during the treatment, the inert gas in the pores expands to cause peeling of the film. According to the experience of the inventors of the present invention, the existence ratio (void ratio) of the pores generated by the spray is several vol.% or more, and the molten condition is more than 10 vol.%. As described above, the titanium material having a high void ratio in the film may be peeled off during the production step, and there may be defects such as breakage during processing.

As a method of forming the film, there is a cold spray method. According to this method, it is also the case that a film is formed on the surface, and an inert high pressure gas is used. According to this method, the void ratio can be made less than 1 vol.% depending on the conditions, but it is extremely difficult to completely prevent the occurrence of pores. Moreover, as in the case of the spray, the pores contain an inert gas, so even after Continued processing will not be eliminated. Further, in the case where heat treatment is applied in a vacuum, the inert gas in the pores may swell, so that the film may be broken.

In order to suppress the surface flaw during hot rolling, as a treatment for melting the surface layer of the flat embryo with an electron beam and re-solidifying, there is a melt re-solidification treatment. Usually, the surface layer which is melted and resolidified is removed by a pickling step after hot rolling. Therefore, in the previous melt resolidification treatment, segregation of the alloy component of the surface layer portion was not considered at all.

The present inventors have attached a titanium plate containing a specific alloying element to the surface of a flat embryo made of pure titanium or a titanium alloy for industrial use, and used the resultant as a material for hot rolling. According to the titanium material which is inexpensive and has excellent performance.

An object of the present invention is to provide an inexpensive resistance by reducing the content of an alloying element added to improve fatigue resistance (the amount of a specific alloying element used to express a target characteristic) and suppressing the manufacturing cost of the titanium material. Fatigue titanium composite and titanium for hot rolling.

The present invention has been developed to solve the above problems, and is based on the following titanium composite materials and titanium materials for hot rolling.

(1) A titanium composite material comprising: an inner layer containing industrial pure titanium or a titanium alloy; and a surface layer formed on at least one of the rolled surfaces of the inner layer, having a chemical composition different from the inner layer; and An intermediate layer formed between the inner layer and the surface layer and having a chemical composition different from the inner layer; and the surface layer has a thickness of 2 μm or more, and the ratio of the total thickness is 40% per one-sided layer Hereinafter, the chemical composition of the surface layer portion is selected from one or more selected from the group consisting of Fe, Cr, Ni, Al, and Zr by mass%: 0.08 to 1.0%, and the remainder: titanium and impurities; and the thickness of the intermediate layer is 0.5 μm. the above.

(2) The titanium composite material according to (1) above, wherein the surface layer other than the rolled surface of the inner layer is formed with another surface layer, and the other surface layer has the same chemical composition as the surface layer.

(3) A titanium material for hot rolling, comprising: a base material containing industrial pure titanium or a titanium alloy; a surface layer joined to at least one of the rolled surfaces of the base material; and a welded portion joining the mother a material and a periphery of the surface layer; and the surface layer material has a chemical composition different from the base material, and is selected from the group consisting of one or more selected from the group consisting of Fe, Cr, Ni, Al, and Zr: 0.08 to 1.0%, and the rest Part: titanium and impurities;

(4) The titanium material for hot rolling according to (3) above, wherein the surface layer other than the rolled surface of the base material is joined to another surface layer material; and the other surface layer material has the same chemical composition as the surface layer material.

(5) The titanium material for hot rolling according to (3) or (4) above, wherein the base material comprises a directly cast flat embryo.

(6) The titanium material for hot rolling according to (5) above, wherein the directly cast flat embryo has at least a part of a surface thereof formed with a molten resolidified layer.

(7) The titanium material for hot rolling according to (6) above, wherein the chemical composition of the molten resolidified layer is different from the chemical composition of the center portion of the thickness of the directly cast flat embryo.

The titanium composite material according to the present invention has an inner layer containing industrial pure titanium or a titanium alloy and a surface layer having a chemical composition different from that of the inner layer, and therefore has the same degree as a titanium material composed of the same titanium alloy as a whole. It is fatigue-resistant, but it can be manufactured inexpensively.

1, 2‧‧‧ Titanium composite

3, 4‧‧‧ surface

5‧‧‧ inner layer

6‧‧‧ parent material (flat embryo)

7,8‧‧‧Materials (titanium plate)

9‧‧‧welding department

Fig. 1 is an explanatory view showing an example of the configuration of a titanium composite material according to the present invention.

Fig. 2 is an explanatory view showing an example of the configuration of a titanium composite material according to the present invention.

Fig. 3 is an explanatory view schematically showing a state in which a titanium rectangular cast piece and a titanium plate are welded in a vacuum.

Fig. 4 is an explanatory view schematically showing a state in which not only the surface of the titanium rectangular cast piece but also the side surface thereof is welded to the titanium plate.

Fig. 5 is an explanatory view showing a method of melting and resolidifying.

Fig. 6 is an explanatory view showing a method of melting and resolidifying.

Fig. 7 is an explanatory view showing a method of melting and resolidifying.

Fig. 8 is an explanatory view showing a plane bending fatigue test material.

Fig. 9 (a) to (d) are photographs of a structure which is an example of a case where it is produced by a melt resolidification method.

In order to solve the above problems, the inventors of the present invention have reduced the use amount of a specific alloying element which exhibits fatigue resistance by alloying only the surface layer of the titanium plate of the final product, and have been developed to suppress the production cost of the titanium material. As a result of intensive research, it was discovered that a base material containing industrial pure titanium or titanium alloy and a surface material having a chemical composition different from that of the base material were used to block the interface of the material from the outside air. A titanium material for hot rolling in which the base material and the surface layer are welded together. The hot-rolled titanium material is thermally processed The titanium composite material can be a titanium material which is excellent in fatigue resistance at an inexpensive price.

The present invention has been completed based on the above knowledge and insights. Hereinafter, the titanium composite material according to the present invention and the titanium material for hot rolling thereof will be described with reference to the drawings. In addition, in the following description, "%" of the content of each element means "% by mass" if it is not particularly dissatisfied.

Titanium composite 1-1. Overall composition

As shown in the first and second figures, the titanium composite materials 1 and 2 include an inner layer 5 containing industrial pure titanium or a titanium alloy, and a rolled surface formed on at least one of the inner layers 5 and having a different surface from the inner layer 5. The chemical composition of the surface layers 3, 4, and an intermediate layer (not shown) formed between the inner layer 5 and the surface layers 3, 4 and having a chemical composition different from that of the inner layer 5. Further, in the examples shown in Figs. 1 and 2, an example in which the surface layer is formed on one or both of the rolling faces of the inner layer 5 may be used, and the surface of the inner layer 5 may be other than the rolling surface ( In the examples shown in Figs. 1 and 2, other surface layers are provided on the side surface (not shown). Hereinafter, the surface layer, the inner layer, and the middle layer will be described in order.

If the thickness of the surface layer is too thin, the desired characteristics cannot be sufficiently obtained. On the other hand, if it is too thick, the ratio of the titanium alloy in the entire titanium composite material will increase, and the cost advantage will be reduced. Therefore, the thickness is set to 2 μm or more, and the ratio of the total thickness is set to 40% or less for each single-sided layer.

1-2. Surface layer (thickness)

In the surface layer, if the thickness of the surface layer that is in contact with the external environment is too thin, fatigue resistance cannot be sufficiently obtained. The thickness of the surface layer varies depending on the thickness of the material used for the production or the processing ratio after the film is produced. However, if it is 2 μm or more, a sufficient effect can be exhibited. Therefore, the thickness of the surface layer is preferably 2 μm or more, more preferably 5 μm or more, and particularly preferably 10 μm or more. Further, the thickness of the surface layer with respect to the total thickness of the titanium composite material is satisfactorily 1% or more.

On the other hand, in the case where the surface layer is thick, the fatigue resistance is not problematic, but the formability is deteriorated. Moreover, the ratio of the titanium alloy in the titanium composite as a whole is increased, and the cost advantage is reduced. Therefore, the thickness of the surface layer is preferably 100 μm or less, and more preferably 50 μm or less. Further, the thickness of the surface layer with respect to the total thickness of the titanium composite material 1 is 40% or less per layer, and more desirably 30% or less. Particularly preferred is 20% or less, and particularly satisfactory is 10% or less.

(chemical composition)

In the titanium composite material 1 according to the present invention, in order to improve the fatigue resistance of at least one of the surface layers (at least the surface layer in contact with the external environment), various alloying elements disclosed below may be contained.

One or more selected from the group consisting of Fe, Cr, Ni, Al, and Zr: 0.08 to 1.0%

The starting point of fatigue failure is the surface of the sheet. Therefore, in order to obtain high fatigue resistance under the maintenance of formability, the crystal grain size of the α phase is preferably 15 μm. under. The crystal grain size of the α phase is more preferably 10 μm or less, still more preferably 5 μm or less.

The crystal grain size of the α phase is set to 15 μm or less, and the total content of Fe, Cr, Ni, Al, and Zr is set to 0.08% or more in order to obtain high fatigue resistance. On the other hand, when the total content of these elements is more than 1.0%, the ductility such as elongation or formability may be greatly lowered. Therefore, the total content of one or more selected from the group consisting of Fe, Cr, Ni, Al, and Zr is set to 0.08 to 1.0%.

The remainder other than the above is an impurity. As an impurity, it may be contained in a range that does not impair the target characteristics, and other impurities mainly include Sn, Mo, V, Mn, Nb, Si, Cu, Co, Pd, Ru, Ta, Y, La as an impurity element mixed from the scrap. And Ce, etc., together with the general impurity elements, C, N, O, and H, the total amount of which is 5% or less is acceptable.

(mechanical characteristics)

The titanium composite material 1 has high fatigue strength while maintaining excellent formability, and the fatigue strength ratio (10 ⁷ fatigue strength/tensile strength) is 0.65 or more. The higher the fatigue strength ratio, the more excellent the fatigue characteristics. The titanium material generally has a value of 0.5 to 0.6. If it is 0.65 or more, the fatigue property is superior to that of a general titanium material. If it is 0.70 or more, It is excellent.

Further, the titanium composite material 1 has a breaking elongation in a direction perpendicular to the rolling direction of 25% or more. Regarding the forming process, the elongation amount has a significant influence, and the larger the elongation, the more excellent the formability.

1-3. Inner layer

The inner layer 5 contains industrial pure titanium or a titanium alloy. For example, when industrial pure titanium is used for the inner layer 5, it is excellent in workability at room temperature as compared with a titanium material containing the same titanium alloy as a whole.

Further, the industrial pure titanium referred to herein includes one to four kinds of JIS standards, and the industrial pure titanium specified in Grades 1 to 4 of ASTM specifications and 3.7025, 3.7035, and 3.7055 of DIN specifications. In other words, the pure titanium for industrial use in the present invention contains, for example, C: 0.1% or less, H: 0.015% or less, O: 0.4% or less, N: 0.07% or less, Fe: 0.5% or less, and the rest. Ti.

Further, in addition to the specific properties, the titanium alloy may be used for the inner layer 5 when it is used for applications where strength is also required. By increasing the content of Fe or the like in the surface layer and forming the inner layer 5 as a titanium alloy, the alloy cost can be greatly reduced and high strength can be obtained.

The titanium alloy forming the inner layer 5 may be any one of an α type titanium alloy, an α + β type titanium alloy, and a β type titanium alloy, depending on the intended use.

Here, as the α-type titanium alloy, for example, a highly corrosion-resistant alloy (ASTM Grade 7, 11, 16, 26, 13, 30, 33 or a JIS species corresponding thereto or a small amount of a titanium material containing various elements) may be used. , Ti-0.5Cu, Ti-1.0Cu, Ti-1.0Cu-0.5Nb, Ti-1.0Cu-1.0Sn-0.3Si-0.25Nb, Ti-0.5Al-0.45Si, Ti-0.9Al-0.35Si, Ti -3Al-2.5V, Ti-5Al-2.5Sn, Ti-6Al-2Sn-4Zr-2Mo, Ti-6Al-2.75Sn-4Zr-0.4Mo-0.45Si, and the like.

As the α + β type titanium alloy, for example, Ti-6Al-4V, Ti-6Al-6V-2Sn, Ti-6Al-7V, Ti-3Al-5V, Ti-5Al-2Sn-2Zr-4Mo-4Cr, Ti can be used. -6Al-2Sn-4Zr-6Mo, Ti-1Fe-0.35O, Ti-1.5Fe-0.5O, Ti-5Al-1Fe, Ti-5Al-1Fe-0.3Si, Ti-5Al-2Fe, Ti-5Al-2Fe -0.3Si, Ti-5Al-2Fe-3Mo, Ti-4.5Al-2Fe-2V-3Mo, and the like.

Further, as the β-type titanium alloy, for example, Ti-11.5Mo-6Zr-4.5Sn, Ti-8V-3Al-6Cr-4Mo-4Zr, Ti-10V-2Fe-3Mo, Ti-13V-11Cr-3Al, or the like can be used. Ti-15V-3Al-3Cr-3Sn, Ti-6.8Mo-4.5Fe-1.5Al, Ti-20V-4Al-1Sn, Ti-22V-4Al, and the like.

However, if the 0.2% proof endurance of the inner layer 5 is more than 1000 MPa, the workability is deteriorated, for example, cracking occurs during bending. Therefore, it is more desirable to use the titanium of the inner layer 5 and the titanium alloy with a 0.2% proof force of 1000 MPa or less.

1-4. Middle layer

The titanium composite of the present invention has an intermediate layer between the inner layer and the surface layer. In other words, the titanium material for hot rolling described later is formed by attaching a base material to a base material and welding the periphery thereof, but in the subsequent hot rolling heating and heat treatment steps after cold rolling, the base material and the surface layer material are used. At the interface, diffusion occurs, and when finally processed into a titanium composite, an intermediate layer is formed between the inner layer from the base material and the surface layer from the surface layer. This intermediate layer has a chemical composition different from the chemical composition of the base material. The intermediate layer is strongly bonded to the inner layer and the surface layer metal. Also, due to the production in the middle layer A continuous elemental gradient is produced, so that the difference in strength between the inner layer and the surface layer can be alleviated, and cracking during processing can be suppressed.

Further, the thickness of the intermediate layer can be measured by EPMA or GDS. More detailed measurements can be made if GDS is used. In the case of GDS, after the surface layer is removed by some degree of polishing, the thickness of the intermediate layer can be measured by performing GDS analysis from the surface in the depth direction. The intermediate layer is defined as C _MID , which is an increase in the content of the base material (in the case where the element is not contained in the base material, and the content of the element contained in the base material is increased from the content of the base material). When the average of the increased content of the surface layer portion is C _AVE , it is in the region of 0 < C _MID ≦ 0.8 × C _AVE .

The thickness of this intermediate layer is set to 0.5 μm or more. On the other hand, if the thickness of the intermediate layer is too large, the alloy layer of the surface layer corresponding thereto becomes thin, and there is a case where the effect cannot be expressed. Therefore, the upper limit should be set to 15 μm.

2. Titanium for hot rolling

The titanium material for hot rolling of the present invention is supplied with a material for hot intercalation processing (a cast piece of a flat embryo, a medium embryo, a small embryo, etc.), and is processed into a cold process, a heat treatment, etc. Titanium composite. Hereinafter, the titanium material for hot rolling of the present invention will be described with reference to the drawings. In the following description, the "%" of the content of each element means "% by mass".

2-1. Overall composition

Figure 3 shows the base metal (titanium rectangular cast, flat embryo) 6 and the surface layer (Titanium plate) 7 is schematically illustrated by welding in a vacuum and bonded together. Fig. 4 is a view showing not only the surface of the base material (titanium rectangular cast piece, flat embryo) 6 (rolled surface) but also the side (roller). The surface material (titanium plate) 7 and 8 are also welded and bonded to each other to be schematically shown.

In the present invention, as shown in Figs. 3 and 4, titanium plates 7 and 8 containing alloying elements having characteristics can be bonded to the surface of the flat metal 6 as a base material, and then titanium composites can be joined by hot rolling cladding. The surface layers of the materials 1, 2 are alloyed.

In the case of manufacturing the titanium composite material 1 shown in Fig. 1, as shown in Fig. 3, the titanium plate 7 can be bonded to the single side of the flat embryo 6 in a vacuum, and the other is the flat embryo 6 The titanium plate 7 is not attached to one side and hot rolled.

As shown in Fig. 4, in addition to the single side of the flat blank 6, the titanium plate 7 can be attached to the other side. Thereby, the occurrence of hot rolling defects in the hot rolling step can be suppressed as described above.

Further, in the case of producing the titanium composite material 2 shown in Fig. 2, as shown in Fig. 4, a plate containing an alloy element may be bonded to the two rolled surfaces of the flat blank 6.

Further, as shown in Fig. 4, the side surface of the flat blank 6 which is the edge side during hot rolling can be welded to the titanium plate 8 which is the same as the rolled surface in the vacuum.

That is, in the hot rolling, usually, the flat embryo 6 is subjected to rolling, and at least a part of the side surface of the flat blank 6 is drawn back to the surface side of the hot rolled sheet. Therefore, if the surface layer of the side surface of the flat blank 6 is coarse or has a large number of defects, the surface of the hot rolled sheet in the width direction may have a near surface. The possibility of surface imperfections. Therefore, since the titanium plate 8 is bonded and welded in a vacuum in the side surface of the flat blank 6, it is possible to effectively prevent surface flaws on the surface near the both ends in the width direction of the hot rolled sheet.

Moreover, the amount of twist of the side surface of the flat blank 6 during hot rolling varies depending on the manufacturing method, but is usually about 20 to 30 mm, so that it is not necessary to completely attach the titanium plate 8 to the side of the flat blank 6, and according to the manufacturing method. The titanium plate 8 can be attached to the portion where the amount of the twist is equivalent.

2-2. Surface material

When the titanium composite materials 1 and 2 are produced, in order to remove the oxide layer formed by hot rolling, the hot rolling is performed by a sandblasting-pickling step. However, at this step, if the surface layer formed by the hot-rolled cladding is removed, the fatigue resistance cannot be exhibited.

Further, if the thickness of the surface layers of the titanium composite materials 1 and 2 is too thin, the intended fatigue resistance cannot be exhibited. On the other hand, if the thickness of the surface layer is too thick, the manufacturing cost will increase accordingly. Since the titanium composite materials 1 and 2 have a thickness of the surface layer to be used for the purpose of use, the thickness of the titanium plates 7 and 8 used as the material is not particularly limited, but the thickness of the flat embryo 6 is 5 to 40%. The scope is appropriate.

As the surface layer (titanium plate), a titanium plate having a specific chemical composition described in the section of the surface layer of the aforementioned titanium composite material is used. It is particularly preferable that the chemical composition of the titanium plate is adjusted to a component containing a specific element in order to suppress breakage of the sheet due to hot rolling, in the same manner as the above-mentioned base material.

2-3. Base metal (flat embryo)

As the base material, industrial pure titanium or a titanium alloy described in the section of the inner layer of the above-mentioned titanium composite material is used. In particular, the base material should be directly cast flat embryos. A direct cast flat embryo can be formed by melting a resolidified layer on at least a portion of the surface. Further, in the case where the surface of the directly cast flat embryo is subjected to a melt re-solidification treatment, a specific element is added to form a molten re-solidified layer having a different thickness from the center portion of the directly cast flat embryo. chemical components.

2-4. Welding joint

On the surface of the flattened blank 6 as a rolled surface, after bonding the titanium plate 7 containing the alloying element, at least the surrounding portion is welded by the welded portion 9 in the vacuum container, whereby the flat blank 6 and the titanium plate 7 are The vacuum is sealed between the 8 and the outside air, and the flat embryo 6 is bonded to the titanium plates 7, 8 by rolling. The welded portion joined to the flat blank 6 after bonding the titanium plates 7 and 8 is formed by blocking the interface between the flat blank 6 and the titanium plates 7 and 8 from the atmosphere, for example, as shown in FIGS. 3 and 4. The whole week will be welded.

Titanium is an active metal, so if placed in the atmosphere, the surface will form a strong passive film. It is impossible to remove the oxidized concentrated layer on the surface portion. However, unlike stainless steel or the like, oxygen is easily dissolved in titanium. Therefore, if it is sealed in a vacuum and heated without supplying oxygen from the outside, oxygen on the surface diffuses to the inside and solidifies, so the surface is blunt. The membrane will be destroyed. Therefore, the flat embryo 6 and its surface titanium plates 7, 8 can be in between In the case where no inclusions or the like are generated, the hot-rolled cladding method is completely adhered.

Further, when the flat embryo 6 is used as the original embryo after casting, it is caused by coarse crystal grains generated during solidification, and surface flaws occur in the subsequent hot rolling step. On the other hand, if the titanium plates 7 and 8 are bonded to the rolled surface of the flat blank 6 as in the present invention, since the bonded titanium plate 7 has a fine structure, the surface flaw of the hot rolling step can be suppressed.

3. Method for manufacturing titanium material for hot rolling 3-1. Manufacturing method of base material

The base material of the titanium material for hot rolling is usually produced by decomposing the ingot into a flat embryo or a small embryo shape, and then cutting and finishing. Further, in recent years, there has been a case where a rectangular flat embryo which can be directly hot rolled is produced for hot rolling in the production of an ingot. In the case of manufacturing by decomposition, the surface is formed to be relatively flat due to decomposition, and it is easy to uniformly distribute the material containing the alloying elements, and it is easy to make the elemental distribution of the alloy phase uniform.

On the other hand, in the case where an ingot (direct cast flat blank) which is directly formed into a shape of a material for hot rolling is used as a base material at the time of casting, since the cutting finishing step can be omitted, it can be manufactured more inexpensively. . Moreover, after the ingot is manufactured and the surface is cut and finished, it is expected to have the same effect in the case of production by decomposition. In the present invention, if an alloy layer is formed in the surface layer stably, an appropriate material can be selected in accordance with the condition.

Preferably, for example, after the flat embryos are combined and welded around, the heating rolls are heated at 700 to 850 ° C for 10 to 30% of the bonding rolls. After rolling, the base material is heated for 3 to 10 hours to diffuse the base material component to the surface layer portion, and then hot rolling is performed. This is because, by hot rolling at the temperature of the β domain, the deformation resistance is lowered and it is easy to roll.

A direct-cast flat embryo used as a base material may be formed by melting and re-solidifying a layer on at least a part of the surface. Further, in the case where the surface of the directly cast flat embryo is subjected to a melt re-solidification treatment, a specific element is added to form a molten re-solidified layer having a different thickness from the center portion of the directly cast flat embryo. chemical components. Hereinafter, the melt resolidification treatment will be described in detail.

Figs. 5 to 7 are explanatory views each showing a method of melting and resolidifying. As a method of melting and resolidifying the surface of the base material of the titanium material for hot rolling, including laser heating, plasma heating, induction heating, electron beam heating, etc., any method is feasible. In particular, in the case of electron beam heating, since it is carried out in a high vacuum, even if pores or the like are formed in the layer during the melt resolidification treatment, since it is a vacuum, it can be pressed by the subsequent rolling and is harmless. Chemical.

Further, since the energy efficiency is high, it can be deeply melted even if it is treated in a large area, and therefore it is particularly suitable for the production of a titanium composite material. The degree of vacuum in the case of melting in a vacuum is more satisfactory to a higher degree of vacuum of 3 × 10 ^-3 Torr or less. Moreover, the number of times of melting and resolidifying the surface layer of the titanium material for hot rolling is not particularly limited. However, the more the number of times, the longer the processing time leads to an increase in cost, and therefore it is more satisfactory one to two times.

Melting and resolidification of the surface layer, in the case of a rectangular embryo In the form, it is implemented as shown in Fig. 5. Specifically, for the outer surface of the rectangular flat blank 10, at least the wide sides 10A, 10B which are the rolling surfaces of the hot rolling step (the surface in contact with the hot rolling rolls) are irradiated with electron beams, and only the The surface layer of the surface is melted. Here, first, the surface 10A of one of the two faces 10A and 10B is implemented.

Here, as shown in Fig. 5, the area of the irradiation region 14 of the electron beam which is directed to the electron beam irradiation gun 12 of the face 10A of the rectangular cast piece 10 is usually additionally larger than the entire area of the face 10A to be irradiated. Since the electron beam irradiation gun 12 is continuously moved or the rectangular casting piece 10 is continuously moved, the electron beam irradiation is performed. In this illumination region, the beam current is formed by adjusting the focus of the electron beam or by using an electromagnetic lens to make a small beam of Oscillation, whereby the shape or area can be adjusted.

Further, as shown by an arrow A in Fig. 5, the following description will be made for the case where the electron beam irradiation gun 12 is continuously moved. Further, the moving direction of the electron beam irradiation gun is not particularly limited, and generally moves continuously along the longitudinal direction of the rectangular cast piece 10 (usually in the casting direction D) or in the width direction (usually in the direction perpendicular to the casting direction D). The width W of the aforementioned irradiation region 14 (in the case of a circular beam or a beam current, the diameter W) is continuously irradiated in a strip shape. Further, the irradiated gun 12 is continuously moved in the opposite direction (or the same direction) with respect to the adjacent unilluminated strip-shaped region, and the electron beam irradiation is performed in a strip shape. Depending on the situation, a plurality of illuminating guns may be used, and electron beam irradiation may be simultaneously performed on a plurality of regions. Figure 5 shows the length along the rectangular slab 10 (usually the casting direction D) The case where the rectangular beam is continuously moved.

When the surface (face 10A) of the rectangular titanium slab 10 is irradiated with an electron beam by such a surface heat treatment step, and the surface thereof is heated to be molten, as shown in the center of the sixth figure, the rectangular titanium slab is shown. The surface layer of 10A of 10 is most melted in response to the depth of heat input. However, the depth from the vertical direction of the irradiation direction of the electron beam is not constant as shown in Fig. 7, and the central portion of the electron beam irradiation is the maximum depth, and the thickness of the end portion of the strip is reduced to become the lower convex portion. The curved shape.

Further, the region of the inner side of the cast piece is larger than the molten layer 16, and the temperature rises due to the influence of the heat of the electron beam irradiation, and becomes a portion of the temperature above the β-deformation point of pure titanium (heat-affected layer = The HAZ layer is metamorphosed into a beta phase. In the same manner, the region which is transformed into the β phase due to the thermal influence by the electron beam irradiation in the surface heating treatment step is the same as the shape of the molten layer 16 and has a curved shape which is convex downward.

By melting and resolidifying the surface layer together with the material containing the intended alloying element, the surface layer for hot rolling can be alloyed to form an alloy layer having a chemical composition different from that of the base material. As the material used at this time, one or more of a powder, a small piece, a wire, a film, a chip, and a mesh can be used. The component and the amount of the material disposed before the melting are defined as a component of the element-concentrated region which is melt-solidified together with the surface of the material as a target component.

However, if the material added is too large, it will cause segregation of the alloy composition. Moreover, if the segregation of the alloy composition is present, The expected performance will not be fully utilized or the degradation will occur early. Therefore, it is important that the heated portion of the surface of the titanium base material is in a molten state, and the alloy material becomes the size of the melting end. Further, it is important to arrange the alloy material in advance on the surface of the titanium base material in consideration of the shape and the width of the molten portion at a specific time. However, in the case where the irradiation position is continuously moved by using the electron beam, since the molten portion is stirred while continuously moving together with the molten titanium and the alloy, the alloy material does not necessarily have to be continuously arranged in advance. In addition, it is of course necessary to avoid the use of alloy materials having an extremely high melting point than the melting point of titanium.

After the melt resolidification treatment, it is preferably maintained at a temperature of 100 ° C or more and less than 500 ° C for 1 hour or more. After melting and re-solidification, if it is rapidly cooled, the surface layer portion is slightly broken due to the strain at the time of solidification. In the subsequent hot rolling step or cold rolling step, the fine crack is used as a starting point, and the characteristics such as peeling of the surface layer and occurrence of a thinned portion of the local alloy layer occur. Further, when the internal cracking occurs due to fine cracking, it is necessary to remove it by the pickling step, and the thickness of the alloy layer is further reduced. By holding at the above temperature, fine cracking of the surface can be suppressed. Moreover, at this temperature, atmospheric oxidation hardly occurs even if it is maintained in the atmosphere.

The titanium material for hot rolling can be produced by attaching a titanium plate containing a specific alloy component to the surface of the base material having the surface layer portion formed by the melt resolidification treatment.

3-2. Hot rolled cladding method

The titanium material for hot rolling is preferably joined to the titanium plates 7, 8 by a hot-rolled cladding method.

As shown in Figs. 3 and 4, the titanium plates 7 and 8 containing the alloying elements exhibiting fatigue resistance are attached to the surface layer of the flat embryo 6, and then joined by a hot-rolled cladding method, whereby the surface layer of the titanium composite material is bonded. Alloying. That is, the titanium plate 7 containing the alloying elements is attached to the surface of the flat surface of the flat blank 6 as a rolled surface, preferably in a vacuum container, at least the surrounding portion is welded by the welded portion 9, thereby the flat embryo 6 and the titanium plate 7 are vacuum-sealed, and the flat blank 6 is bonded to the titanium plate 7 by rolling. The titanium plate 7 is welded to the slab 6 so that the atmosphere between the squash 6 and the titanium plate 7 is not intruded, for example, as shown in Figs. 3 and 4, the whole circumference is welded.

Titanium is an active metal, so if placed in the atmosphere, the surface will form a strong passive film. It is impossible to remove the oxidized concentrated layer on the surface portion. However, unlike stainless steel and the like, oxygen is easily dissolved in titanium, and if it is sealed in a vacuum and heated without supplying oxygen from the outside, oxygen on the surface diffuses to the inside and solidifies, so that the surface is formed into a passive state. The film will be destroyed. Therefore, the flat blank 6 and the titanium plate 7 on the surface thereof can be completely adhered by the hot rolling cladding method without causing inclusions or the like therebetween.

Further, if the flat embryo 6 is used as a raw embryo after casting, it is caused by coarse crystal grains which are formed during solidification, and surface flaws occur in the subsequent hot rolling step. On the other hand, when the titanium plate 7 is bonded to the rolled surface of the flat blank 6 as in the present invention, since the bonded titanium plate 7 has a fine structure, the surface flaw in the hot rolling step can be suppressed.

As shown in Figure 3, not only on one side of the flat embryo 6, but also The titanium plate 7 is attached to both sides thereof. Thereby, the occurrence of hot rolling in the hot rolling step can be suppressed as described above. In the hot rolling, usually, the flat embryo 6 is rolled, and at least a part of the side surface of the flat blank 6 is drawn back to the surface side of the hot rolled sheet. Therefore, if the surface layer of the side surface of the flat blank 6 is coarse or has many defects, the surface near the both ends in the width direction of the hot rolled sheet may have a surface flaw. Therefore, as shown in Fig. 4, it is preferable to form the side surface of the flat blank 6 on the edge side at the time of hot rolling, and also to splicing the titanium plate 8 of a contract type similarly to the rolled surface. Thereby, it is possible to effectively prevent surface flaws on the surface near both ends in the width direction of the hot rolled sheet. This fusion is preferably carried out in a vacuum.

Further, the amount of the side back of the flat embryo 6 during hot rolling differs depending on the manufacturing method, and is usually about 20 to 30 mm. Therefore, it is not necessary to completely attach the titanium plate 8 to the side of the flat embryo 6, and it is only equivalent. The titanium plate 8 may be attached to the portion of the manufacturing method. By hot rolling, the composition from the base material can be contained in the interior of the titanium composite by performing high-temperature annealing for a long time. For example, a heat treatment for 30 hours at 700 to 900 ° C can be exemplified.

A method of welding the flat blank 6 and the titanium plates 7, 8 in a vacuum, including electron beam welding or plasma welding, and the like. It is particularly desirable to carry out the electron beam welding under high vacuum, whereby a high vacuum can be set between the flat blank 6 and the titanium plates 7, 8. It is desirable that the degree of vacuum in the case where the titanium sheets 7, 8 are welded in a vacuum is set to a higher degree of vacuum of 3 × 10 ^-3 Torr or less.

Moreover, the welding of the flat embryo 6 and the titanium plate 7 does not necessarily have to be In the vacuum vessel, for example, a vacuum suction hole may be provided in advance in the inside of the titanium plate 7, and after the titanium plate 7 and the flat blank 6 are overlapped, the vacuum between the flat blank 6 and the titanium plate 7 may be evacuated by a vacuum suction hole. The flat embryo 6 is welded to the titanium plate 7 on one side, and the vacuum suction hole is closed after welding.

As the cladding, the titanium plates 7 and 8 having the intended alloying elements are used on the surface of the flat blank 6, and the thickness or chemical composition of the surface layer is formed by hot-rolling cladding to form an alloy layer on the surface layers of the titanium composites 1 and 2. It depends on the thickness of the titanium plates 7, 8 before the bonding or the distribution of the alloying elements. Of course, in the production of the titanium plates 7, 8, in order to obtain the final necessary strength and ductility, annealing treatment is performed in a vacuum atmosphere or the like, thereby causing diffusion at the interface, and a concentration gradient is generated in the vicinity of the interface in the depth direction.

However, the diffusion distance of the element caused by the final annealing step is about several μm, which is not the overall diffusion of the thickness of the alloy layer, and has no effect on the concentration of the alloying element in the vicinity of the surface layer which is particularly important for the characteristic performance.

Therefore, the uniformity of the alloy composition of the titanium plates 7 and 8 as a whole is closely related to the performance of the stability of the characteristics. In the case of the hot-rolled cladding, since the titanium plates 7 and 8 manufactured by the products can be used, the thickness accuracy of the alloy is not easily controlled, and the segregation of the alloy components can be easily controlled, and the titanium composite materials 1 and 2 having the surface layer can be manufactured. This surface layer has a uniform thickness and chemical composition after manufacture, and can exhibit stable properties.

Further, as described above, since no inclusions are formed between the surface layers of the titanium composite materials 1 and 2 and the inner layer 5, they do not become a starting point of cracking or fatigue, etc., in addition to the adhesion.

3. Method for manufacturing titanium composite material

It is important that the alloy layer formed by attaching the titanium plate to the surface of the flat embryo is left as a final product residue, and it is therefore necessary to suppress the loss of the oxide film or the surface layer caused by the surface flaw as much as possible. Specifically, after considering the characteristics or capabilities of the equipment used in the production, the technical solutions on the hot rolling step described below are optimized and appropriately employed.

4-1. Heating step

When the material for hot rolling is heated, the loss of the oxide film can be suppressed to be low by heating at a low temperature for a short period of time. However, since the heat conduction of the titanium material is small, if the inside of the flat embryo is hot-rolled at a low temperature, the inside is liable to occur. The disadvantage of cracking is therefore optimized in accordance with the performance or characteristics of the furnace to be used to minimize the occurrence of the film.

4-2. Hot rolling step

Also in the hot rolling step, if the surface temperature is too high, a large amount of film is formed during the passage, and the oxide film loss is increased. On the other hand, if the oxide film loss is too low, the surface enthalpy becomes easy to occur, so it is necessary to remove it by pickling in a subsequent step, and it is desirable to carry out heat treatment by suppressing the temperature range of the surface enthalpy. Rolling. Therefore, it is desirable to perform rolling at an optimum temperature range. Further, since the surface temperature of the titanium material is lowered during the rolling, it is satisfactory that the cooling of the rolls during the rolling is minimized, and the decrease in the surface temperature of the titanium material is suppressed.

4-3. Pickling step

The hot rolled sheet has an oxide layer on its surface and thus has a step of removing the oxide layer in a subsequent step. Titanium is generally mainly used after sand blasting to remove the oxide layer by acid washing with a solution of nitric acid. Further, depending on the situation, there is a case where the surface is ground by grinding with a grindstone after pickling. After the release film, it may be a two-layer or three-layer structure composed of the inner layer and the surface layer of the base material and the surface layer portion of the titanium material for hot rolling.

Since the film formed by the hot rolling step is thick, it is usually treated as a pickling treatment to remove a part of the surface film before the pickling treatment, and a crack is formed on the surface, and the liquid is soaked to the crack in the subsequent pickling step. So that one part of the base material is also removed. At this time, it is important to perform a weak blasting treatment which does not cause cracks on the surface of the base material, and it is necessary to select an optimum blasting condition in accordance with the chemical composition of the surface of the titanium material. Specifically, for example, by selecting an appropriate projection material or a projection speed (adjustable by the rotation speed of the impeller), a condition in which cracks are not generated on the base material can be selected. The optimization of these conditions differs depending on the characteristics of the titanium plate to which the surface of the flat embryo is attached. Therefore, the optimum conditions may be determined in advance.

Hereinafter, the present invention will be more specifically described based on the examples, but the present invention is not limited by the examples.

[Example 1]

Hereinafter, a procedure for producing a test material will be described as an embodiment of the present invention. As a material for hot rolling, the melting and the points shown below are used. The condition of solution and surface conditioning is used to make a flat embryo. These are indicated by symbols S1, S2, S3, S4, S5, and S6.

S1; a flat embryo cast by electron beam melting, the surface is mechanically cut

S2; a flat embryo cast by electron beam melting, the surface is as cast

S3; the rectangular ingot cast by electron beam melting is decomposed into a flat embryo shape, and the surface is mechanically cut.

S4; the cylindrical ingot cast by vacuum arc melting is decomposed into a flat embryo shape, and the surface is mechanically cut.

S5; flat embryo cast by plasma arc melting method, the surface is mechanically cut

S6; for the S2 flat embryo, the surface is melted and solidified by electron beam

Further, Example 1 is an example of using a material for hot rolling containing industrial pure titanium, and its chemical composition is O: 0.030 to 0.33%, Fe: 0.027 to 0.090%, C: 0.01% or less, and H: 0.003 or less. , N: 0.006% or less.

The flat embryo 6 is used by the method in which the pure titanium plate 7 having a high concentration of Fe, Cr, Ni, Al, and Zr is bonded to the surface of the flat embryo 6 by fusion in a vacuum. Specifically, on the surface of the flat embryo 6, a pure titanium plate containing various thicknesses such as Fe is superposed, and the periphery thereof is welded by electron beam fusion bonding. A part of the pure titanium plate 8 having a higher concentration than the flat embryo 6, Fe or the like is joined by electron beam fusion on the side of the flat embryo.

Further, the thickness of the standard flat embryo was set to 125 mm. one of In part, in order to adjust the ratio of the thickness of the surface layer to the total thickness, the thickness of the flat embryo is also 75 mm, 40 mm, or the like.

The titanium flat embryo is heated to 850 ° C, and hot rolled to a thickness of 5 mm, and then the surface of the front and back are subjected to a peeling treatment by sand blasting and nitric acid, and then cold rolling is performed to form a titanium plate having a thickness of 0.5 to 1.0 mm. Then, it was annealed in a vacuum or an inert gas atmosphere to prepare a test piece of the present invention.

In addition to the present invention, the titanium slab which is not bonded to the titanium plate 7 is subjected to the same steps as the cold rolling, and is heated to 580 to 780 ° C in a vacuum or an inert gas atmosphere, and heat-treated for 240 minutes. Comparative test piece.

For each test piece, the α-phase crystal grain size, tensile strength, elongation, fatigue strength, and formability at each position were evaluated according to the conditions shown below.

With respect to each of the test materials as the titanium composite material 2, the α-phase crystal grain size, tensile strength, elongation, fatigue strength, and moldability at each position were evaluated according to the conditions shown below.

(α phase crystal grain size)

The added element concentration region of the surface layer was measured by EPMA. In the photograph of the photograph taken by the optical microscope, the average crystal grain size of the α phase was calculated by the cutting method according to JIS G 0551 (2005) in the thickness of the central portion of the thickness and the thickness of the added element in the surface layer.

(tensile strength, elongation)

A tensile test material (one-half the size of one-half of JIS13-B tensile test material) having a parallel portion of 6.25 × 32 mm, a punctuation of 25 mm, a 10 mm wide head and a total length of 80 mm was produced, and 0.5% of the punctuation was measured until 0.2% of the endurance was measured. The tensile speed of min and the endurance were measured by a tensile test at a tensile speed of 30%/min. Here, the tensile strength and the total elongation amount in the direction perpendicular to the rolling direction were evaluated.

(fatigue strength)

The fatigue test was carried out under the conditions of a stress ratio R = -1 and a frequency of 25 Hz using the plane bending fatigue test material shown in Fig. 8 and a plane bending tester manufactured by Tokyo Denso Co., Ltd. Here, the number of repetitions until the break of each stress amplitude was determined as a stress fatigue curve, and the fatigue limit (fatigue strength) which was not broken even if the bending was repeated for 10 ⁷ times was evaluated.

(formability)

Using a deep-drawing tester made by Tokyo Testing Machinery Co., Ltd., model SAS-350D, A 40 mm ball head punching head was subjected to a ball head protrusion test for a titanium plate processed into a shape of 90 mm × 90 m × 0.5 mm. The high-viscosity oil (# 660) made by Japan Labor Oil Co., Ltd. was applied to the test, and the polyethylene sheet was placed on the test board so that the punch head and the titanium plate were not in direct contact with each other. The height of the time is highlighted and used for evaluation. The protrusion height under the ball-end protrusion test is strongly affected by the oxygen concentration. Therefore, the JIS type is 21.0 mm or more, the JIS type is 19.0 mm or more, and the JIS type 3 is 13.0 mm or more.

Fig. 9 shows an example of a photograph of a tissue in a case where it is produced by a hot rolling cladding method. Fig. 9 (a) is a photograph of the structure of the test material No. A1, Fig. 9 (b) is a photograph of the structure of the test material No. A14, and Fig. 9 (c) is a photograph of the structure of the test material No. A15, the ninth Figure (d) is a photograph of the structure of the test material No. A16. Further, Fig. 9(a) is a comparative example and is a general titanium material, and Figs. 9(b) to 9(d) are examples of the present invention.

The test results are summarized in Tables 1 and 2. Table 1 is a case of using a material for hot rolling containing pure titanium for industrial use equivalent to JIS, and Table 2 is a case of using a material for hot rolling containing JIS 2 and three kinds of industrial pure titanium.

In the test materials No. A8, 9, and 38 in Table 1, an example in which a titanium plate 7 having a high concentration of Fe or the like was bonded to the side surface of the flat embryo 6 was welded.

The test materials No. A1 to 3 were the prior examples in which the surface layers 3 and 4 were not present, and the fatigue strength ratios were 0.63, 0.63, and 0.55, respectively, and the titanium material was a general value.

The examples of the present invention are excellent in terms of both formability and fatigue strength.

On the other hand, in the test material No. A4 of the comparative example, the content of the alloying elements (Fe) of the surface layers 3 and 4 was lower than the range of the present invention, and therefore the fatigue strength ratio was a general value.

In the test material No. A5 of the comparative example, the thickness of the intermediate layer was lower than the range of the present invention, so that peeling of the surface layer occurred and the elongation was poor.

In the test material No. A18 of the comparative example, the thickness of the surface layers 3 and 4 was lower than the range of the present invention, and the fatigue strength ratio was a general value in terms of titanium material.

In the test material No. A29 of the comparative example, the content of the alloying elements (Al) of the surface layers 3 and 4 was higher than the range of the present invention, and the fatigue strength was a general value as compared with the titanium material.

Further, in the test material No. A30 of the comparative example, the content of the alloying elements (Al) of the surface layers 3 and 4 was higher than the range of the present invention, and thus the amount of elongation was not good.

The test materials No. B1 and 2 were the prior examples without the surface layers 3 and 4, and the fatigue strength ratio was 0.58 or 0.59, which is a general value in terms of titanium material.

The examples of the present invention are excellent in terms of both formability and fatigue strength.

In the test material No. B13 of the comparative example, the Fe content of the surface layers 3 and 4 was higher than the range of the present invention, and the elongation was poor.

[Example 2]

In the second embodiment, the following examples of the titanium alloy of M1 to M10 are used for the flat embryo 6.

M1; ASTM Grade 7

M2; ASTM Grade 11

M3; ASTM Grade 16

M4; ASTM Grade 26

M5; ASTM Grade 30

M6; 0.02% Pd-0.022% Mm-Ti (O: 0.050%, Fe: 0.041%). Here, Mm refers to a mixed rare earth element (mixed rare earth metal) before separation and purification, and has a composition of 55% Ce, 51% La, 10% Nd, and 4% Pr.

M7; 0.03% Pd-0.002% Y-Ti (O: 0.049%, Fe: 0.033%)

M8; 0.5% Cu-Ti (O: 0.048%, Fe: 0.038%)

M9; 1.0% Cu-Ti (O: 0.048%, Fe: 0.033%)

M10; 1.0Cu-0.5% Nb-Ti (O: 0.044%, Fe: 0.040%)

The titanium plate 7 containing the same titanium alloy as the flat embryo 6 having a higher concentration of Fe, Cr, Ni, Al, and Zr than the flat embryo 6 is used on the surface of the flat embryo 6 containing the above titanium alloy. a method of welding and bonding in a vacuum, specifically, a titanium alloy plate 7 of various thicknesses containing 0.1 to 0.5% of Fe, Cr, Ni, Al, and Zr is superposed on the surface of the flat embryo 6 and The periphery is welded by an electron beam. Further, in the comparative example, the total concentration of Fe, Cr, Ni, Al, and Zr of the titanium alloy sheet 7 is in the range of 0.03 to 1.1%. Further, other manufacturing methods and evaluation methods are the same as in the first embodiment.

The results are summarized in Table 3.

The test materials No. C11 to 30 in Table 3 are examples of the present invention which completely satisfy the requirements of the present invention, and the test materials No. C1 to 10 are comparative examples which do not conform to the provisions of the present invention.

The test materials No. C1 to 10 are the prior examples without the surface layers 3 and 4, and the fatigue strength ratio was 0.61 or 0.62, which is a general value for the titanium material.

The test materials No. C11 to 30 of the examples of the present invention are excellent in terms of both formability and fatigue strength.

Claims (7)

A titanium composite material comprising: an inner layer containing industrial pure titanium or a titanium alloy; and a surface layer formed on a rolled surface of at least one of the inner layers, having a chemical composition different from the inner layer; and an intermediate layer Forming between the inner layer and the surface layer, having an elemental gradient continuous with the inner layer and the surface layer, and having a chemical composition different from the inner layer; and the surface layer having a thickness of 2 μm or more and accounting for The ratio of the thickness is 40% or less per one-sided layer; the chemical composition of the surface layer is one or more selected from the group consisting of Fe, Cr, Ni, Al, and Zr by mass%: 0.08 to 1.0%, and the balance: titanium And impurities; the thickness of the intermediate layer is 0.5 μm or more. The titanium composite material according to claim 1, wherein the surface layer other than the rolled surface of the inner layer is formed with another surface layer, and the other surface layer has the same chemical composition as the surface layer. A titanium material for hot rolling, comprising: a base material containing industrial pure titanium or a titanium alloy; a surface layer joined to at least one of the rolled surfaces of the base material; and a welded portion joining the base material and the foregoing The periphery of the topsheet; and the foregoing surface layer has a chemical composition different from the above-mentioned base material, and is expressed by mass% It is selected from one or more of Fe, Cr, Ni, Al, and Zr: 0.08 to 1.0%, and the remainder: titanium and impurities; and the welded portion blocks the interface between the base material and the surface layer from the outside air. The titanium material for hot rolling according to the third aspect of the invention, wherein the surface layer other than the rolled surface of the base material is joined to another surface layer; and the other surface layer material has the same chemical composition as the surface layer. A titanium material for hot rolling according to claim 3 or 4, wherein the base material comprises a direct cast flat embryo. The titanium material for hot rolling according to claim 5, wherein the directly cast flat embryo has at least a part of a surface thereof formed with a molten resolidified layer. The titanium material for hot rolling according to claim 6, wherein the chemical composition of the molten resolidified layer is different from the chemical composition of the central portion of the thickness of the directly cast flat embryo.