JPWO2017018513A1 - Titanium composite and titanium material for hot rolling - Google Patents

Abstract

An inner layer 5 made of industrial pure titanium or a titanium alloy, a surface layer 3 having a different chemical composition from the inner layer 5 formed on at least one surface of the inner layer 5, and an inner layer formed between the inner layer 5 and the surface layer 3. An intermediate layer having a chemical composition different from 5, the surface layer 3 has a thickness of 2 μm or more, the proportion of the total thickness is 40% or less per side, and the thickness of the intermediate layer is 0 1. Titanium composite 1 which is 5 μm or more. The chemical composition of the surface layer 3 is B: 0.1 to 3.0%, and the balance: titanium and impurities. This titanium composite material has a desired neutron blocking property despite its low cost.

Description

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

  Titanium materials are excellent in properties such as corrosion resistance, oxidation resistance, fatigue resistance, hydrogen embrittlement resistance, and neutron blocking properties. These properties can be achieved by adding various alloying elements to titanium.

In facilities that handle radioactive waste, such as nuclear power generation facilities, neutron beam shielding plates that can shield thermal neutrons are used. The neutron shielding effect is highest for boron 10 ( ¹⁰ B), which is 19.9% of natural B. Stainless steel containing B is generally used as a material for the neutron beam shielding plate.

Japanese Examined Patent Publication No. 58-6704 (Patent Document 1) includes Kuna Copite (2MgO.3B ₂ O ₂ .13H ₂ O), Meyerhot Ferrite (3CaO.3B ₂ O ₂ .7H ₂ O), Colemanite (2CaO.3B). ₂ O ₂ · 5H ₂ O), a cured molded body obtained by kneading and molding a borate aggregate containing crystal water such as hemihydrate gypsum and calcium aluminate cement with water, and containing 5 mass of B A neutron beam blocking material containing at least% is disclosed. However, since the neutron beam shielding material disclosed in Patent Document 1 is made of cement, there is a problem in terms of corrosion resistance, manufacturability, and workability.

  The use of a B-containing titanium alloy, which has better corrosion resistance than stainless steel, as a neutron beam blocking material has also been studied. For example, Japanese Patent Publication No. 1-168833 (Patent Document 2) uses a hot-rolled sheet of boron-containing titanium alloy containing 0.1 to 10% by mass of B and the balance of titanium and inevitable impurities. It is disclosed.

Further, JP-A-5-142392 (Patent Document 3) discloses a boron-containing material (NaB ₄ O ₇ , B ₂ O ₃ , PbO, Fe ₂ O _3, etc.) in a hollow metal casing, A radiation shielding material filled with a metal oxide mixed therein to be solidified is disclosed. According to Patent Document 3, neutron beams are mainly blocked by boron and hydrogen, and gamma rays are blocked by a casing and metal therein.

  The titanium material is usually produced by the method shown below. First, the raw material titanium oxide is chlorinated to titanium tetrachloride by the crawl method, and then reduced with magnesium or sodium to produce a lump-like sponge-like metal titanium (sponge titanium). This sponge titanium is press-molded to form a titanium consumable electrode, and a titanium ingot is manufactured by vacuum arc melting using the titanium consumable electrode as an electrode. At this time, an alloy element is added as necessary to produce a titanium alloy ingot. Thereafter, the titanium alloy ingot is divided, forged and rolled into a titanium slab, and the titanium slab is further subjected to hot rolling, annealing, pickling, cold rolling, and vacuum heat treatment to produce a titanium thin plate.

  In addition, as a method for producing a titanium thin plate, titanium ingot is smashed, hydroground, dehydrogenated, powder crushed, and classified to produce titanium powder, and titanium powder is powder-rolled, sintered, and cold-rolled. The manufacturing method is also known.

  Japanese Patent Laid-Open No. 2011-42828 (Patent Document 4) discloses that a titanium powder is produced directly from sponge titanium instead of a titanium ingot, and a titanium thin plate is produced from the obtained titanium powder. Sintered compacts are manufactured by sintering pre-sintered compacts made of viscous compositions containing agents and solvents into thin sheets, and sintered compacts are manufactured by compacting the sintered compacts. In the method for producing a titanium thin plate for re-sintering, a method is disclosed in which the fracture elongation of the sintered thin plate is 0.4% or more, the density ratio is 80% or more, and the density ratio of the sintered compacted plate is 90% or more. ing.

  Japanese Patent Laid-Open No. 2014-19945 (Patent Document 5) discloses a composite powder obtained by adding an appropriate amount of iron powder, chromium powder or copper powder to titanium alloy powder using titanium alloy scrap or titanium alloy ingot as a raw material. After extruding the carbon steel capsule, the capsule on the surface of the obtained round bar is dissolved and removed, and further solution treatment or solution treatment and aging treatment are performed to produce a titanium alloy with excellent quality by the powder method A method is disclosed.

  In JP 2001-131609 (Patent Document 6), a sponge capsule is filled with a sponge titanium powder and then subjected to warm extrusion at an extrusion ratio of 1.5 or more and an extrusion temperature of 700 ° C. or less. A method for producing a titanium molded body in which 20% or more of the total length of the grain boundary of the molded body is in metal contact is performed by performing outer peripheral processing excluding copper.

  When hot-rolling a hot-rolled material, if the hot-rolled material is a so-called difficult-to-process material with high hot deformation resistance due to insufficient hot ductility, such as pure titanium or titanium alloy, these are thin plates. A pack rolling method is known as a technique for rolling the sheet. The pack rolling method is a method in which a core material such as a titanium alloy having poor workability is covered with a cover material such as inexpensive carbon steel having good workability and hot rolling is performed.

  Specifically, for example, a release agent is applied to the surface of the core material, and at least two upper and lower surfaces thereof are covered with a cover material, or the four peripheral surfaces are covered with a spacer material in addition to the upper and lower surfaces, and the surroundings are welded. Assembled and hot rolled. In pack rolling, a core material, which is a material to be rolled, is covered with a cover material and hot rolled. Therefore, the core material surface does not directly contact a cold medium (atmosphere or roll), and the temperature drop of the core material can be suppressed, so that even a core material with poor workability can be manufactured.

Japanese Laid-Open Patent Publication No. 63-207401 (Patent Document 7) discloses a method of assembling a hermetically sealed box, and Japanese Laid-Open Patent Publication No. 09-136102 (Patent Document 8) discloses a degree of vacuum of 10 ⁻³ torr order or more. A method of manufacturing a hermetically sealed box by sealing a cover material is disclosed, and further, Japanese Patent Application Laid-Open No. 11-057810 (Patent Document 9) covers carbon steel (cover material) and is in the order of 10 ⁻² torr. A method for producing a hermetic coated box by sealing by high energy density welding under the following vacuum is disclosed.

  On the other hand, as a method for manufacturing a highly corrosion-resistant material at a low cost, a method is known in which a titanium material is bonded to the surface of a material serving as a base material.

  In Japanese Patent Application Laid-Open No. 08-141754 (Patent Document 10), steel is used as a base material and titanium or a titanium alloy is used as a base material, and the joint surface between the base material and the base material is evacuated and then assembled by welding. A method for manufacturing a titanium clad steel sheet in which an assembly slab for rolling is joined by hot rolling is disclosed.

  In JP-A-11-170076 (patent document 11), pure nickel, pure iron and a carbon content of 0.01% by mass or less are formed on the surface of a base steel material containing 0.03% by mass or more of carbon. After the titanium foil material is laminated by interposing an insert material made of any one of the above-mentioned low carbon steels with a thickness of 20 μm or more, a laser beam is irradiated from either side of the lamination direction, A method of manufacturing a titanium-coated steel material by melting and joining at least the vicinity of the edge with a base steel material over the entire circumference is disclosed.

  In JP-A-2015-045040 (Patent Document 12), the surface of a porous titanium raw material (sponge titanium) formed into an ingot shape is melted using an electron beam under vacuum, and the surface layer portion is made of dense titanium. The titanium ingot is manufactured and hot rolled and cold rolled to form a porous portion in which the porous titanium raw material is formed into an ingot shape, and the entire surface of the porous portion composed of dense titanium. A method for producing a dense titanium material (titanium ingot) having a dense coating portion for coating with very little energy is exemplified.

  Japanese Patent Application Laid-Open No. Sho 62-270277 (Patent Document 13) describes that surface effect treatment of an engine member for automobiles is performed by thermal spraying.

Japanese Patent Publication No.58-6704 Japanese Patent Publication No. 1-168833 Japanese Patent Laid-Open No. 5-142392 JP 2011-42828 A JP 2014-19945 A JP 2001-131609 A JP-A 63-207401 JP 09-136102 A Japanese Patent Laid-Open No. 11-057810 Japanese Patent Laid-Open No. 08-141754 Japanese Patent Laid-Open No. 11-170076 Japanese Patent Laying-Open No. 2015-045040 JP-A-62-270277

  The hot-rolled sheet disclosed in Patent Document 2 has a high B content, so it cannot be denied that the cost is increased, and the workability is not good, so that it is actually difficult to use as a neutron beam shielding plate.

  Furthermore, the radiation shielding material disclosed by Patent Document 3 is a metal casing material filled with a boron-containing material, and processing after filling the boron-containing material is difficult.

  Conventionally, when manufacturing a titanium material through hot working, sponge titanium is press-molded to form a titanium consumable electrode, and a titanium ingot is manufactured by vacuum arc melting using the titanium consumable electrode as an electrode. The titanium slab was forged and rolled into a titanium slab, and the titanium slab was manufactured by hot rolling, annealing, pickling, and cold rolling.

  In this case, a process of manufacturing titanium ingot by dissolving titanium has been added. A method of producing titanium powder by powder rolling, sintering, and cold rolling is also known, but in the method of producing titanium powder from a titanium ingot, a step of dissolving titanium is also added.

  In the method for producing a titanium material from titanium powder, even if it does not go through a melting step, expensive titanium powder is used as a raw material, so that the obtained titanium material is very expensive. The same applies to the methods disclosed in Patent Documents 7 to 8.

  In pack rolling, the core material covered with the cover material is slab or ingot to the last, and has undergone a melting step or is made of expensive titanium powder, and the manufacturing cost cannot be reduced.

  In Patent Document 12, a dense titanium material can be produced with very little energy, but the surface of the titanium sponge formed into an ingot shape is dissolved, and the dense titanium surface layer portion and the internal components are the same kind of pure titanium. Or it is prescribed | regulated as a titanium alloy, for example, a manufacturing cost cannot be reduced by forming a titanium alloy layer uniformly only over the surface layer part over a wide range.

  On the other hand, many materials that can manufacture inexpensive corrosion-resistant materials and have titanium or a titanium alloy bonded to the surface of the base material select steel as the base material. Therefore, if the titanium layer on the surface is lost, the corrosion resistance is impaired. Even if a titanium material is adopted as a base material, a drastic cost improvement cannot be expected as long as a titanium material manufactured through a normal manufacturing process is used. Then, the present inventors considered providing an alloy layer containing a specific alloy element on the surface layer of a slab made of industrial pure titanium or a titanium alloy to obtain a titanium material that is inexpensive and excellent in specific performance.

  As in Patent Document 13, thermal spraying is a method in which a film is formed by melting metal, ceramics or the like and spraying it on the surface of a titanium material. When a film is formed by this method, the formation of pores in the film cannot be avoided. Usually, during thermal spraying, thermal spraying is performed while shielding with an inert gas in order to avoid oxidation of the film. These inert gases are entrained in the pores of the coating. Such pores containing the inert gas are not pressed by hot working or the like. Further, in the production of titanium, vacuum heat treatment is generally carried out, but during this treatment, the inert gas in the pores may expand and the film may be peeled off. According to the experience of the present inventors, the abundance ratio (porosity) of pores generated by thermal spraying is several vol. % Or more and 10 vol. % May be exceeded. As described above, a titanium material having a high porosity in the film has a risk of peeling in the manufacturing process, and there is a risk that a defect such as a crack during processing may occur.

  As a method for forming the film, there is a cold spray method. Even when a film is formed on the surface by this method, an inert high-pressure gas is used. In this method, the porosity is 1 vol. However, it is extremely difficult to completely prevent the generation of pores. As in the case of thermal spraying, since the pores contain the inert gas, they do not disappear even by subsequent processing. In addition, when heat treatment is performed in a vacuum, the inert gas in the pores may expand and the film may break.

  In order to suppress surface flaws during hot rolling, there is a melt resolidification process as a process for melting and resolidifying the surface layer of the slab using an electron beam. Usually, the melted and re-solidified surface layer is removed in a pickling step after hot rolling. For this reason, in the conventional melt resolidification treatment, no consideration is given to the segregation of the alloy components in the surface layer portion.

  Therefore, the present inventors specify the material for hot rolling at a low price by attaching a titanium plate containing a specific alloy element to the surface of a slab made of industrial pure titanium or titanium alloy. We considered obtaining a titanium material with excellent performance.

  The present invention reduces the content of alloying elements to be added to improve neutron blocking properties (the amount of specific alloying elements that express target characteristics), and suppresses the production cost of titanium materials, An object is to obtain a titanium composite material having a desired neutron blocking property and a titanium material for hot rolling at low cost.

  This invention is made | formed in order to solve the said subject, and makes a summary the following titanium composite material and the titanium material for hot rolling.

(1) an inner layer made of industrial pure titanium or titanium alloy;
A surface layer having a chemical composition different from that of the inner layer formed on at least one rolling surface of the inner layer;
An intermediate layer formed between the inner layer and the surface layer and having a different chemical composition from the inner layer;
A titanium composite comprising:
The surface layer has a thickness of 2 μm or more, and the proportion of the total thickness is 40% or less per side,
The chemical composition of the surface layer part is mass%,
B: 0.1-3.0% balance: titanium and impurities,
The intermediate layer has a thickness of 0.5 μm or more.
Titanium composite material.

(2) Another surface layer is formed on a surface other than the rolled surface of the inner layer,
The other surface layer has the same chemical composition as the surface layer,
The titanium composite material of (1) above.

(3) a base material made of pure industrial titanium or a titanium alloy;
A surface layer material joined to at least one rolling surface of the base material;
A titanium material for hot rolling comprising a welded portion that joins the periphery of the base material and the surface layer material,
The surface layer material has a chemical composition different from that of the base material, and in mass%,
B: 0.1 to 3.0%
The balance: titanium and impurities
The welded portion shields the interface between the base material and the surface material from outside air;
Titanium material for hot rolling.

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

(5) The base material comprises a direct cast slab.
The titanium material for hot rolling according to the above (3) or (4).

(6) The directly cast slab is obtained by forming a melt-resolidified layer on at least a part of the surface.
The titanium material for hot rolling according to (5) above.

(7) The chemical composition of the melt-resolidified layer is different from the chemical composition of the center portion of the thickness of the direct cast slab,
(6) Titanium material for hot rolling.

  Since the titanium composite material according to the present invention includes an inner layer made of industrial pure titanium or a titanium alloy and a surface layer having a chemical composition different from that of the inner layer, the whole is compared with a titanium material made of the same titanium alloy. Thus, it has the same neutron blocking property, but can be manufactured at low cost.

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 the titanium composite material according to the present invention. FIG. 3 is an explanatory view schematically showing that the titanium rectangular slab and the titanium plate are bonded together by welding in a vacuum. FIG. 4 is an explanatory view schematically showing bonding by welding a titanium plate not only on the surface of the titanium rectangular cast piece but also on the side surface. FIG. 5 is an explanatory view showing a method of melt re-solidification. FIG. 6 is an explanatory view showing a method of melt re-solidification. FIG. 7 is an explanatory view showing a method of melt re-solidification.

  In order to solve the above problems, the present inventors reduced the amount of a specific alloy element that exhibits neutron blocking properties by alloying only the surface layer of the titanium plate of the final product, and the titanium material As a result of diligent investigations to reduce the manufacturing costs of these materials, the interface between the base material made of industrial pure titanium or titanium alloy and the surface layer material having a different chemical composition from the base material is blocked from the outside air. Thus, the titanium material for hot rolling which welded the circumference | surroundings of a base material and surface layer material was discovered. The titanium composite obtained by hot working this titanium material for hot rolling becomes a titanium material having excellent neutron blocking properties at low cost.

  The present invention has been made based on the above findings. Hereinafter, a titanium composite material and a titanium material for hot rolling thereof according to the present invention will be described with reference to the drawings. In the following description, “%” regarding the content of each element means “mass%” unless otherwise specified.

1. 1. Titanium composite 1-1. Overall Configuration As shown in FIGS. 1 and 2, titanium composites 1 and 2 are different in chemical composition from inner layer 5 made of industrial pure titanium or titanium alloy and inner layer 5 formed on at least one rolling surface of inner layer 5. The surface layers 3 and 4 which have a composition, and the intermediate | middle layer (illustration omitted) which is formed between the inner layer 5 and the surface layers 3 and 4 and has a chemical composition different from the inner layer 5 is provided. In the example shown in FIGS. 1 and 2, an example is shown in which a surface layer is formed on one or both rolling surfaces of the inner layer 5, but a surface other than the rolling surface of the inner layer 5 (side surface in the example shown in FIGS. 1 and 2). ) May be provided with another surface layer (not shown). Hereinafter, the surface layer, the inner layer, and the intermediate layer will be described in order.

  If the thickness of the surface layer is too thin, desired characteristics cannot be obtained sufficiently. On the other hand, if it is too thick, the proportion of the titanium alloy in the entire titanium composite increases, so the cost merit decreases. Therefore, the thickness is 2 μm or more, and the proportion of the total thickness is 40% or less per side.

1-2. Surface layer (thickness)
If the thickness of the surface layer in contact with the external environment is too thin, the neutron beam shielding effect cannot be obtained sufficiently. On the other hand, when the surface layer is thick, the neutron beam shielding effect is improved, but the proportion of the titanium alloy in the entire material increases, so that the manufacturing cost increases. The thickness of the surface layer is preferably 5 μm or more, and more preferably 10 μm or more. The ratio of the thickness of the surface layer to the total thickness of the titanium composite is 40% or less per side, and more preferably 30% or less. In particular, it should be 5 to 40%.

(Chemical composition)
In the titanium composite material 1 according to the present invention, an alloy element is contained in order to provide the surface layer with a neutron beam shielding effect. Hereinafter, the reason for selecting the additive element and the reason for limiting the addition amount range will be described in detail.

B: 0.1 to 3.0%
In B, 19.9% of ¹⁰ B exists, but this ¹⁰ B has a large absorption cross section of thermal neutrons and a large shielding effect of neutron beams. If the B content is less than 0.1%, a sufficient neutron beam shielding effect cannot be obtained. If the B content exceeds 3.0%, cracking during hot rolling and deterioration of workability may occur.

Here, the titanium alloy containing B can be produced by adding a boride such as B or TiB _{2 to} titanium. In addition, if a ¹⁰ B enriched boron-containing material ( ¹⁰ B content is approximately 90% or more) such as H ₃ ¹⁰ BO ₃ , ¹⁰ B ₂ O ¹⁰ B ₄ C is used, neutron beams even if the B content is small Since the shielding effect is large, it is extremely effective.

When H ₃ ¹⁰ BO ₃ , ¹⁰ B ₂ O, ¹⁰ B ₄ C is used, H and O are also concentrated in the alloy layer. However, if H is removed from the material during heat treatment such as vacuum annealing, it is a problem. If O and C are 0.4 mass% O or less and 0.1 mass% C or less, which are below the upper limit contained in industrial pure titanium, they can be produced without any problem.

  The remainder other than the above is impurities. Impurities can be contained within a range that does not impair the neutron blocking properties, and other impurities are mainly impurity elements mixed from scrap such as Cr, Ta, Al, V, Cr, Nb, Si, Sn, Mn, Mo. And Cu, etc., together with general impurity elements C, N, Fe, O and H, a total amount of 5% or less is acceptable.

(Use)
A polyethylene material having a B content of 3.0 to 4.0 mass% and a plate thickness of 10 to 100 mm is used in a radiation therapy facility such as particle beam therapy or BNCT (boron neutron capture therapy). Moreover, in the nuclear power related equipment, a stainless steel plate having a B content of 0.5 to 1.5 mass% and a plate thickness of 4.0 to 6.0 mm is used for the nuclear fuel storage rack. By using the titanium composite material 1 in which the B content and thickness (B-concentrated layer thickness) of the surface layer are adjusted, it is possible to exhibit characteristics equal to or higher than those of the above materials.

1-3. Inner layer The inner layer 5 is made of industrial pure titanium or a titanium alloy. For example, when industrial pure titanium is used for the inner layer 5, the processability at room temperature is excellent as compared with a titanium material made entirely of the same titanium alloy.

  In addition, the industrial pure titanium here is an industry defined by JIS standards 1 to 4 and ASTM standards Grades 1 to 4 and DIN standards 3, 7025, 3, 7035, and 37055. Contains pure titanium. That is, the industrial pure titanium targeted in the present invention is, for example, C: 0.1% or less, H: 0.015% or less, O: 0.4% or less, N: 0.07% or less, Fe: It consists of 0.5% or less and the balance Ti.

  In addition to the specific performance, a titanium alloy may be used for the inner layer 5 when the strength is also required. By increasing the B content of the surface layer and forming the inner layer 5 from a titanium alloy, the alloy cost can be significantly reduced and high strength can be obtained.

  As the titanium alloy forming the inner layer 5, any of an α-type titanium alloy, an α + β-type titanium alloy, and a β-type titanium alloy can be used according to a required application.

  Here, as the α-type titanium alloy, for example, a high corrosion resistance alloy (ASTM Grade 7, 11, 16, 26, 13, 30, 33 or a titanium material containing a small amount of JIS species corresponding to these or various elements). 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 or the like can be used.

  Examples of the α + β type titanium alloy include Ti-6Al-4V, Ti-6Al-6V-2Sn, Ti-6Al-7V, Ti-3Al-5V, Ti-5Al-2Sn-2Zr-4Mo-4Cr, and Ti-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, or the like can be used.

  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 Ti-15V-3Al-3Cr-3Sn, Ti-6.8Mo-4.5Fe-1.5Al, Ti-20V-4Al-1Sn, Ti-22V-4Al, etc. can be used.

  However, if the 0.2% proof stress of the inner layer 5 exceeds 1000 MPa, the workability deteriorates, and for example, there is a risk of cracking during bending. Therefore, the titanium and titanium alloy used for the inner layer 5 desirably have a 0.2% proof stress of 1000 MPa or less.

1-4. Intermediate Layer The titanium composite material of the present invention includes an intermediate layer between the inner layer and the surface layer. That is, a titanium material for hot rolling, which will be described later, is a material in which a surface layer material is attached to a base material and the periphery thereof is welded. During the subsequent hot rolling and heat treatment processes after cold rolling, the base material and the surface layer When diffusion occurs at the interface with the material and the titanium composite material is finally finished, an intermediate layer is formed between the inner layer derived from the base material and the surface layer derived from the surface material. This intermediate layer has a chemical composition different from the chemical composition of the base material. This intermediate layer bonds the inner layer and the surface layer to each other and bonds them firmly. Further, since a continuous element gradient is generated in the intermediate layer, the difference in strength between the inner layer and the surface layer can be reduced, and cracks during processing can be suppressed.

The thickness of the intermediate layer can be measured using EPMA or GDS. If GDS is used, more detailed measurement is possible. In the case of GDS, after removing the surface layer to some extent by polishing, the thickness of the intermediate layer can be measured by performing GDS analysis in the depth direction from the surface. The intermediate layer is the increased content from the base material (in the case of an element not included in the base material, its content, in the case of an element also included in the base material, the increase in content from the base material) ) _Is C _MID, and the average of the increased content in the surface layer portion is C _AVE , it means a region of 0 <C _MID ≦ 0.8 × C _AVE .

  The thickness of this intermediate layer is 0.5 μm or more. On the other hand, if the thickness of the intermediate layer becomes too large, the surface alloy layer may become thin by that amount, and the effect may not be exhibited. Therefore, the upper limit is preferably 15 μm.

2. Titanium material for hot rolling The titanium material for hot rolling of the present invention is a material (slab of slab, bloom, billet, etc.) used for hot working, and after hot working, it can be cooled if necessary. It is processed into a titanium composite material by performing inter-processing, heat treatment, etc. Hereinafter, the titanium material for hot rolling according to the present invention will be described with reference to the drawings. In the following description, “%” regarding the content of each element means “mass%”.

2-1. Overall Configuration FIG. 3 is an explanatory view schematically showing that the base material (titanium rectangular cast, slab) 6 and the surface layer material (titanium plate) 7 are bonded together in a vacuum, and FIG. It is typical to bond the surface materials (titanium plates) 7 and 8 not only to the surface (rolled surface) of the base material (titanium rectangular cast slab, slab) but also to the side surfaces (surfaces other than the rolled surface). It is explanatory drawing shown in.

  In the present invention, as shown in FIGS. 3 and 4, titanium plates 7 and 8 containing an alloy element that exhibits neutron blocking properties are bonded to the surface of a slab 6 that is a base material, and then bonded by hot rolling cladding. As a result, the surface layers of the titanium composite materials 1 and 2 are alloyed.

  When the titanium composite material 1 shown in FIG. 1 is manufactured, a titanium plate 7 may be bonded to only one side of the slab 6 in a vacuum as shown in FIG. 3, and the titanium plate 7 is attached to the other side of the slab 6. You may hot-roll without sticking.

  As shown in FIG. 4, a titanium plate 7 may be bonded to one side of the slab 6 as well as the other side. Thereby, generation | occurrence | production of the hot rolling in a hot rolling process can be suppressed as mentioned above.

  Furthermore, when the titanium composite material 2 shown in FIG. 2 is manufactured, a plate containing an alloy element may be bonded to both rolling surfaces of the slab 6 as shown in FIG.

  Furthermore, as shown in FIG. 4, the same standard titanium plate 8 may be bonded in a vacuum and welded to the side surface of the slab 6 that becomes the edge side during hot rolling as well as the rolled surface.

  That is, in hot rolling, usually, when the slab 6 is subjected to reduction, at least a part of the side surface of the slab 6 wraps around the surface side of the hot-rolled sheet. Therefore, if the structure of the surface layer on the side surface of the slab 6 is coarse or a large number of defects exist, surface flaws may occur on the surface near both ends in the width direction of the hot-rolled sheet. For this reason, generation | occurrence | production of the surface flaw in the surface near the both ends of the width direction of a hot-rolled sheet can be effectively prevented by bonding the titanium plate 8 to the side surface of the slab 6 and welding it.

  In addition, although the quantity which the side surface of the slab 6 wraps around at the time of hot rolling changes with manufacturing methods, since it is usually about 20-30 mm, it is not necessary to stick the titanium plate 8 on the whole side surface of the slab 6, and it is a manufacturing method. It is only necessary to attach the titanium plate 8 only to the portion corresponding to the sneak amount.

2-2. Surface layer material When manufacturing the titanium composite materials 1 and 2, in order to remove the oxide layer formed by hot rolling, it is manufactured through a shot-pickling process after hot rolling. However, if the surface layer formed by the hot-rolled cladding is removed during this step, the neutron blocking characteristics cannot be expressed.

  Moreover, when the thickness of the surface layer of the titanium composites 1 and 2 becomes too thin, the target neutron blocking characteristic is not expressed. On the other hand, if the thickness of the surface layer is too thick, the manufacturing cost increases accordingly. Since the titanium composite materials 1 and 2 only have to have a surface layer thickness suitable 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 slab 6 It is preferable to be in the range of 5 to 40%.

  As the surface layer material (titanium plate), a titanium plate having a predetermined chemical composition described in the section of the surface layer of the titanium composite material is used. In particular, it is desirable to adjust the chemical composition of the titanium plate to a component containing a predetermined element in the same component as the base material in order to suppress the plate breakage during hot rolling. . In particular, the following points should be noted.

  As the surface layer material, a titanium alloy plate containing 0.1% or more and 3% or less of B is used. In other words, the chemical composition of the surface layer material is based on the same components as the above-mentioned base material in order to suppress plate breakage during hot rolling, and the component contains B in the range of 0.1% to 3%. It is desirable to adjust to. Moreover, in order to maintain favorable workability in hot and cold, it is good also as a Ti-0.1-3% B alloy.

This B-containing titanium alloy plate can be produced by adding a boride such as B or TiB _{2 to} titanium. In _addition, the use of ^{_{H 3 10 BO 3, 10 B}} 2 O, 10 B 4 C 10B concentrated boron-containing material, such as ⁽¹⁰ B content of about 90% or more), B addition amount of the surface layer 3 and 4 At least the titanium composites 1 and 2 are extremely effective because they have a large neutron shielding effect.

When H ₃ ¹⁰ BO ₃ , ¹⁰ B ₂ O, ¹⁰ B ₄ C is used, H, O, and C will also be concentrated in the alloy layer, but H is a problem because it escapes from the material during heat treatment such as vacuum annealing. However, O and C can be produced without problems as long as they are 0.4% O or less and 0.1% C or less, which are below the upper limit contained in industrial pure titanium.

2-3. Base material (slab)
As the base material, the industrial pure titanium or titanium alloy described in the section of the inner layer of the titanium composite is used. In particular, it is preferable to use a direct casting slab as a base material. The direct cast slab may be one in which a melt resolidified layer is formed on at least a part of the surface. In addition, a predetermined element was added to the surface of the direct casting slab when the melt resolidification process was performed, and a melt resolidification layer having a chemical composition different from that of the center portion of the direct casting slab was formed. May be.

2-4. After the titanium plate 7 containing an alloy element is bonded to the surface corresponding to the rolling surface of the welded portion slab 6, the slab 6 and the titanium plates 7 and 8 are welded at least around the welded portion 9 in a vacuum vessel. The slab 6 and the titanium plates 7 and 8 are bonded together by sealing with a vacuum, blocking the outside air, and rolling. For example, as shown in FIGS. 3 and 4, the welded portion to be joined after the titanium plates 7 and 8 are bonded to the slab 6 is shielded from the atmosphere at the interface between the slab 6 and the titanium plates 7 and 8. Weld.

  Titanium is an active metal and forms a strong passive film on the surface when left in the atmosphere. It is impossible to remove the oxidized layer on the surface. However, unlike stainless steel, etc., oxygen easily dissolves in titanium. Therefore, when heated in a vacuum and sealed without external oxygen supply, oxygen on the surface diffuses into the solid solution. Therefore, the passive film formed on the surface disappears. Therefore, the slab 6 and the titanium plates 7 and 8 on the surface thereof can be completely adhered by the hot rolling cladding method without generating any inclusions between them.

  Furthermore, when a slab as cast is used as the slab 6, surface defects will occur in the subsequent hot rolling process due to coarse crystal grains generated during solidification. On the other hand, when the titanium plates 7 and 8 are bonded to the rolled surface of the slab 6 as in the present invention, the bonded titanium plate 7 has a fine structure, so that surface defects in the hot rolling process can be suppressed. .

3. 3. Method for producing titanium material for hot rolling 3-1. Manufacturing method of base material A base material of a titanium material for hot rolling is usually manufactured by cutting and refining an ingot after making it into a slab or billet shape by breakdown. In recent years, rectangular slabs that can be hot-rolled directly at the time of ingot production are sometimes produced and used for hot-rolling. When manufactured by breakdown, since the surface is relatively flat by breakdown, it is easy to disperse the material containing the alloy element relatively uniformly, and it is easy to make the element distribution of the alloy phase uniform.

  On the other hand, when using the ingot (direct casting slab) directly manufactured to the shape of the material for hot rolling at the time of casting as a base material, since a cutting and refining process can be omitted, it can manufacture more cheaply. In addition, if the ingot is manufactured and then used after the surface is cut and refined, the same effect can be expected when it is manufactured through breakdown. In the present invention, an alloy layer may be stably formed on the surface layer, and an appropriate material may be selected according to the situation.

  For example, after assembling the slab and welding the surroundings, it is heated to 700 to 850 ° C. and bonded and rolled at 10 to 30%, and then heated at the β region temperature for 3 to 10 hours to diffuse the base material component to the surface layer portion. It is preferable to perform hot rolling later. This is because by performing hot rolling at a β-region temperature, the deformation resistance becomes low and rolling becomes easy.

  The direct casting slab used as the base material may be one in which a melt resolidification layer is formed on at least a part of the surface. In addition, a predetermined element was added to the surface of the direct casting slab when the melt resolidification process was performed, and a melt resolidification layer having a chemical composition different from that of the center portion of the direct casting slab was formed. May be. Hereinafter, the melt resolidification process will be described in detail.

  5-7 is explanatory drawing which shows the method of melt re-solidification all. As a method for melting and resolidifying the surface of the base material of the titanium material for hot rolling, there are laser heating, plasma heating, induction heating, electron beam heating, etc., and any method may be used. In particular, especially in the case of electron beam heating, since it is performed in a high vacuum, even if a void or the like is formed in this layer during the melt resolidification treatment, it can be made harmless by pressure bonding in subsequent rolling because it is a vacuum.

Furthermore, since it is high in energy efficiency, it can be melted deeply even if a large area is processed, and is particularly suitable for the production of titanium composite materials. The degree of vacuum in the case of melting in vacuum is desirably a higher degree of vacuum of 3 × 10 ⁻³ Torr or less. Moreover, there is no restriction | limiting in particular about the frequency | count of melt-solidifying the surface layer of the titanium material for hot rolling. However, as the number of times increases, the processing time becomes longer and the cost increases.

  In the case of a rectangular slab, the melt resolidification method of the surface layer is performed as shown in FIG. That is, among the outer surfaces of the rectangular slab 10, at least two wide surfaces 10A and 10B that become the rolling surfaces (surfaces in contact with the hot rolling roll) in the hot rolling process are irradiated with an electron beam, and the surfaces on the surfaces are irradiated. Only melt the layer. Here, it is assumed that the surface 10A is one of the two surfaces 10A and 10B.

  Here, as shown in FIG. 5, the area of the electron beam irradiation region 14 by the single electron beam irradiation gun 12 on the surface 10A of the rectangular slab 10 is compared with the total area of the surface 10A to be irradiated. The electron beam irradiation is actually performed while continuously moving the electron beam irradiation gun 12 or continuously moving the rectangular slab 10. It is normal. The shape and area of this irradiation area can be adjusted by adjusting the focus of the electron beam or by using an electromagnetic lens to oscillate a small beam at a high frequency (oscillation oscillation) to form a beam bundle. can do.

  Then, as indicated by an arrow A in FIG. 5, the following explanation will be made on the assumption that the electron beam irradiation gun 12 is continuously moved. Although the moving direction of the electron beam irradiation gun is not particularly limited, it is generally continuous along the length direction (usually the casting direction D) or the width direction (usually the direction perpendicular to the casting direction D) of the rectangular slab 10. Then, the irradiation region 14 is continuously irradiated in a band shape with a width W (in the case of a circular beam or beam bundle, a diameter W). Further, the electron beam irradiation is performed in a belt shape while continuously moving the irradiation gun 12 in the reverse direction (or the same direction) in the adjacent unirradiated belt region. In some cases, a plurality of irradiation guns may be used to simultaneously perform electron beam irradiation on a plurality of regions. In FIG. 5, the case where a rectangular beam is continuously moved along the length direction (usually casting direction D) of the rectangular slab 10 is shown.

  If the surface (surface 10A) of the rectangular titanium cast piece 10 is irradiated with an electron beam by such a surface heat treatment step and heated to melt the surface, the rectangular titanium as shown in the left side of the center of FIG. The surface layer of the surface 10A of the slab 10 is melted at the maximum by a depth corresponding to the heat input. However, the depth from the direction perpendicular to the irradiation direction of the electron beam is not constant as shown in FIG. 7, and the depth becomes the largest at the central part of the electron beam irradiation, and the thickness increases toward the strip-shaped end part. Decreases, resulting in a downwardly convex curved shape.

  The region inside the slab from the molten layer 16 also rises in temperature due to the heat effect of electron beam irradiation, and the portion where the temperature is higher than the β transformation point of pure titanium (heat affected layer = HAZ layer) is the β phase. To metamorphosis. In this way, the region transformed into the β phase by the heat effect of the electron beam irradiation in the surface heat treatment step also has a downwardly curved shape similar to the shape of the molten layer 16.

  By performing re-solidification of the surface layer together with the material composed of the target alloy element, the material layer for hot rolling can be alloyed to form an alloy layer having a chemical composition different from that of the base material. As a material used in this case, one or more of powder, chip, wire, thin film, cutting powder, and mesh may be used. The component and amount of the material to be arranged before melting are determined so that the component in the element concentration region after melting and solidifying together with the material surface becomes the target component.

  However, if the material to be added is too large, it causes segregation of alloy components. And when the segregation of an alloy component exists, desired performance cannot fully be exhibited, or deterioration will be accelerated. For this reason, it is important to make the size of the alloy material completely melted while the heated portion on the surface of the titanium base material is in a molten state. In addition, it is important that the alloy material is evenly arranged on the surface of the titanium base material in consideration of the shape and size of the melted part at a specific time. However, when the irradiation position is continuously moved using the electron beam, the molten part is stirred while moving continuously with the molten titanium and the alloy, so that the alloy material is always arranged continuously. There is no need. In addition, it is natural that the use of an alloy material having a melting point extremely higher than that of titanium must be avoided.

  After the melt resolidification treatment, it is preferable to hold at a temperature of 100 ° C. or higher and lower than 500 ° C. for 1 hour or longer. If it is cooled rapidly after melting and resolidification, fine cracks may occur in the surface layer due to strain during solidification. In the subsequent hot rolling process and cold rolling process, this fine crack may be the starting point, causing surface layer peeling, or a part where the alloy layer is partially thin, which may deteriorate the neutron blocking performance. . Further, if the inside is oxidized due to fine cracks, it is necessary to remove in the pickling process, and the thickness of the alloy layer is further reduced. By maintaining at the above temperature, fine cracks on the surface can be suppressed. At this temperature, atmospheric oxidation hardly occurs even if the temperature is maintained.

A titanium material for hot rolling can be manufactured by attaching a titanium plate containing a predetermined alloy component to the surface of a base material provided with a surface layer portion formed by melt resolidification treatment.
3-2. Hot Rolled Clad Method The titanium material for hot rolling is preferably bonded to the slab 6 and the titanium plates 7 and 8 which are welded in advance by the hot rolled clad method.

  As shown in FIGS. 3 and 4, after the titanium plates 7 and 8 containing the alloy element exhibiting neutron blocking properties are bonded to the surface layer of the slab 6, the surface layer of the titanium composite material is bonded by hot rolling cladding. Is alloyed. That is, after the titanium plate 7 containing the alloy element is bonded to the surface corresponding to the rolling surface of the slab 6, the slab 6 and the titanium plate 7 are preferably welded at least around the welded portion 9 in a vacuum vessel. The space between the slab 6 and the titanium plate 7 is bonded together by vacuum sealing and rolling. In welding for bonding the titanium plate 7 to the slab 6, for example, as shown in FIGS. 3 and 4, the entire circumference is welded so that air does not enter between the slab 6 and the titanium plate 7.

  Titanium is an active metal and forms a strong passive film on the surface when left in the atmosphere. It is impossible to remove the oxidized layer on the surface. However, unlike stainless steel, etc., oxygen easily dissolves in titanium. Therefore, when heated in a vacuum and sealed without external oxygen supply, oxygen on the surface diffuses into the solid solution. Therefore, the passive film formed on the surface disappears. For this reason, the slab 6 and the titanium plate 7 on the surface thereof can be completely adhered by the hot rolling cladding method without generating any inclusions between them.

  Furthermore, when a slab as cast is used as the slab 6, surface defects will occur in the subsequent hot rolling process due to coarse crystal grains generated during solidification. On the other hand, when the titanium plate 7 is bonded to the rolled surface of the slab 6 as in the present invention, the bonded titanium plate 7 has a fine structure, so that surface defects in the hot rolling process can be suppressed.

  As shown in FIG. 3, a titanium plate 7 may be bonded to both sides of the slab 6 instead of just one side. Thereby, generation | occurrence | production of the hot rolling in a hot rolling process can be suppressed as mentioned above. In hot rolling, at least a part of the side surface of the slab 6 usually wraps around the surface side of the hot-rolled sheet by being rolled down by the slab 6. Therefore, if the structure of the surface layer on the side surface of the slab 6 is coarse or a large number of defects exist, surface flaws may occur on the surface near both ends in the width direction of the hot-rolled sheet. For this reason, as shown in FIG. 4, the same standard titanium plate 8 is preferably bonded and welded to the side surface of the slab 6 on the edge side during hot rolling as well as the rolled surface. Thereby, generation | occurrence | production of the surface flaw in the surface near the both ends of the width direction of a hot rolled sheet can be prevented effectively. This welding is preferably performed in a vacuum.

  In addition, although the quantity which the side surface of the slab 6 wraps around at the time of hot rolling changes with manufacturing methods, since it is usually about 20-30 mm, it is not necessary to stick the titanium plate 8 on the whole side surface of the slab 6, and it is a manufacturing method. It is only necessary to attach the titanium plate 8 only to the portion corresponding to the sneak amount. By performing high-temperature long-time annealing after hot rolling, the base material-derived component can be contained in the titanium composite material. For example, a heat treatment at 700 to 900 ° C. for 30 hours is exemplified.

Methods for welding the slab 6 and the titanium plates 7 and 8 in vacuum include electron beam welding and plasma welding. In particular, since the electron beam welding can be performed under a high vacuum, the space between the slab 6 and the titanium plates 7 and 8 can be made a high vacuum, which is desirable. The degree of vacuum when the titanium plates 7 and 8 are welded in a vacuum is desirably a higher degree of vacuum of 3 × 10 ⁻³ Torr or less.

  The slab 6 and the titanium plate 7 are not necessarily welded in a vacuum vessel. For example, a vacuum suction hole is provided in the titanium plate 7 and the titanium plate 7 is overlapped with the slab 6. Later, the slab 6 and the titanium plate 7 may be welded while evacuating the slab 6 and the titanium plate 7 using a vacuum suction hole, and the vacuum suction hole may be sealed after welding.

  When titanium plates 7 and 8 having a target alloy element are used as the clad on the surface of the slab 6 and an alloy layer is formed on the surface of the titanium composites 1 and 2 by hot rolling clad, the thickness and chemical composition of the surface layer are as follows: It depends on the thickness of the titanium plates 7 and 8 before bonding and the distribution of alloy elements. Of course, when the titanium plates 7 and 8 are manufactured, the annealing treatment is performed in a vacuum atmosphere or the like in order to obtain the finally required strength and ductility. A concentration gradient is generated in the depth direction.

  However, the diffusion distance of the element generated in the final annealing process is about several μm, and the entire thickness of the alloy layer is not diffused. In particular, it affects the concentration of the alloy element in the vicinity of the surface layer, which is important for neutron blocking performance. do not do.

  For this reason, the uniformity of the alloy components in the entire titanium plates 7 and 8 leads to stable expression of the characteristics. In the case of hot-rolled clad, it is possible to use titanium plates 7 and 8 manufactured as products, so it is easy to control the segregation of alloy components as well as the plate thickness accuracy, and have a uniform thickness and chemical properties after manufacturing. Titanium composite materials 1 and 2 having a surface layer having components can be produced, and stable characteristics can be expressed.

  Further, as described above, since no inclusion is generated between the surface layer of the titanium composites 1 and 2 and the inner layer 5, in addition to adhesion, there is no starting point such as cracking or fatigue.

3. Manufacturing method of titanium composite It is important to leave the alloy layer formed by sticking a titanium plate on the slab surface as the final product, and it is necessary to suppress the removal of the surface layer due to scale loss and surface flaws as much as possible. is there. Specifically, this is achieved by optimizing and appropriately adopting the following devices in the hot rolling process in consideration of the characteristics and capabilities of the equipment used for production.

4-1. Heating process When heating the raw material for hot rolling, scale loss can be suppressed by heating at low temperature for a short time, but the titanium material has low heat conduction, and if the inside of the slab is hot rolled at a low temperature, There is also a drawback that cracks are likely to occur, and optimization is performed to minimize the generation of scales according to the performance and characteristics of the heating furnace used.

4-2. Hot rolling process Also in the hot rolling process, if the surface temperature is too high, a large amount of scale is generated during sheet passing, and the scale loss increases. On the other hand, if it is too low, the scale loss is reduced, but surface flaws are likely to occur. Therefore, it is necessary to remove by surface pickling, and it is desirable to perform hot rolling in a temperature range in which surface flaws can be suppressed. . Therefore, it is desirable to perform rolling in the optimum temperature range. In addition, since the surface temperature of the titanium material decreases during rolling, it is desirable to minimize roll cooling during rolling and suppress the decrease in the surface temperature of the titanium material.

4-3. Pickling process Since the hot-rolled plate has an oxide layer on its surface, there is a descaling process for removing the oxide layer in the subsequent process. In titanium, after shot blasting, the oxide layer is generally removed by pickling with a nitric hydrofluoric acid solution. In some cases, the surface may be ground by grinding with a grindstone after pickling. After descaling, a two-layer or three-layer structure including an inner layer and a surface layer derived from the base material and the surface layer portion of the titanium material for hot rolling may be used.

  Since the scale generated in the hot rolling process is thick, usually a shot blasting process is performed as a pretreatment for the pickling process to remove a part of the scale on the surface, and at the same time, cracks are formed on the surface, and in the subsequent pickling process The liquid penetrates into the cracks and removes part of the base material. At this time, it is important to perform weak blasting without causing cracks on the surface of the base material, and it is necessary to select optimum blasting conditions according to the chemical components on the surface of the titanium material. Specifically, for example, by selecting an appropriate projecting material and optimizing the projecting speed (adjustable by the rotation speed of the emperor), a condition that does not cause a crack in the base material is selected. Since optimization of these conditions differs depending on the characteristics of the titanium plate attached to the slab surface, the optimum conditions may be determined in advance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to these Examples.

Hereinafter, the present invention will be described more specifically with reference to examples.
The neutron beam shielding plates shown in FIGS. 1 and 2 and Table 1 were manufactured by the hot rolling cladding shown below using the slab 6 and the titanium plates 7 and 8 shown in FIGS.

  First, a titanium ingot 6 as a material was manufactured using a rectangular mold by electron beam melting (EB melting) or plasma arc melting (plasma melting), or using a cylindrical mold by VAR melting. The size of the ingot 6 is a cylindrical ingot 6 having a diameter of 1200 mm × a length of 2500 mm, and a rectangular ingot 6 having a thickness of 100 mm × a width of 1000 mm × a length of 4500 mm. -0.35O, Ti-0.5Cu, Ti-1Cu, Ti-1Cu-0.5Nb, Ti-5Al-1Fe, Ti-3Al-2.5V, Ti-3Al-5V.

  Most of the cast ingot 6 was bonded to the titanium plate 7 as it was or after the cast skin on the surface of the ingot 6 was cut. The other ingot 6 was cut after the block rolling, and the titanium plate 7 was bonded.

The titanium plate 7 is bonded by overlapping (covering) Ti-B alloy plates having various sizes and thicknesses equivalent to the rolling surface of the ingot or slab 6, and electron beam welding (about 3 ×). Welding was performed at a vacuum degree of 10 ⁻³ Torr or less, and the space between the titanium plate 7 and the ingot (or slab) 6 was sealed in a vacuum state.

Bonding of the alloy plate was mainly performed on the rolled surface, and two types of a two-layer structure in which only one side surface was performed and a three-layer structure in which both side surfaces were performed were produced. For the surface layers (B-concentrated layers) 3 and 4, the ratio per one side of the total thickness in the final product is shown in Table 1, and in the three-layer structure, the B-concentrated layers on both surfaces have the same thickness. It was adjusted to become. Ti-B alloy plate is used for the titanium plate 7 used for bonding the plates, and B is added in advance by TiB ₂ or ¹⁰ B enriched boron (H ₃ ¹⁰ BO ₃ , ¹⁰ B ₂ O ¹⁰ B ₄ C). The ingot melted in this manner was produced by hot rolling. The Ti-B alloy plate is descaled by passing a continuous pickling line made of nitric hydrofluoric acid after hot rolling.

  Using steel equipment, the slab 6 was heated at 800 ° C. for 240 minutes and then hot-rolled to manufacture strip coils (titanium composite materials) 1 and 2 having a thickness of about 4 mm. By this hot rolling, the surface layers of the titanium composites 1 and 2 were made Ti-0.1 to 3.8% B alloy.

  In this embodiment, a titanium alloy may be used for the slab 6, but in this case as well, the titanium plate 7 to be bonded was a Ti-0.1 to 3.8% B alloy containing only Ti and B.

  The strip coils 1 and 2 after hot rolling were passed through a continuous pickling line made of nitric hydrofluoric acid, descaled, and then visually observed for the occurrence of cracks. In addition, the measuring method of the depth of the surface layers 3 and 4 (B concentrating layer) is a part of the hot-rolled sheet (collected from the central part in the width direction at three points of the front end, the center and the rear end in the longitudinal direction). The cut and polished material was subjected to SEM / EDS analysis, and the ratio of the B-concentrated layer to the plate thickness and the B concentration of the B-concentrated layer were determined (the average value in the observed portion was adopted).

  In addition, a total of 20 bending specimens in the L direction were sampled from the central part in the width direction at three locations, the front end, the center, and the rear end in the longitudinal direction, and bent according to JIS Z 2248 (metal material bending test method). A test was conducted. The test temperature was room temperature, a three-point bending test was performed at a bending angle up to 120 degrees, the presence or absence of cracks was evaluated, and the crack generation rate was determined.

  Moreover, the evaluation of the neutron beam shielding effect used Am-Be (4.5 MeV) as a radiation source, and fixed a test piece of 500 mm × 500 mm × 4 mm thickness at a position 200 mm from the radiation source. The detector is installed at a position of 300 mm from the radiation source, and the peak value of the target energy is measured for each of the radiation equivalents of the industrial test pure titanium JIS type 1 and the test piece of the control test piece. The shielding effect was evaluated (industrial pure titanium JIS type 1 neutron beam shielding effect is 1, and the value of each test piece is described).

  The results are summarized in Table 1.

  No. 1-No. The comparative example and Example shown in 8 are the cases where the EB melt | dissolution ingot (slab 6) as cast is used.

  No. The comparative example 1 is a case where the same kind of pure titanium JIS as the slab 6 is used as the titanium plate 7. No cracks occurred in the hot-rolled sheet, and no cracks occurred in the bending test.

  No. The comparative example 2 is a case where the intermediate layer is thin. The hot-rolled sheet was partially cracked, and the crack generation rate was high even in the bending test.

  No. 3 is a case where the thickness ratio of the surface layers 3 and 4 exceeds 40%. The hot-rolled sheet was partially cracked, and the crack generation rate was high even in the bending test.

  No. The examples of 4 to 7 are cases in which the evaluation was made by changing the type of the interior 5, the layer structure, the thickness ratio of the surface layers 3 and 4, and the B content. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. Example 8 is a case where the alloy plate is bonded not only to the rolling surface but also to the side surface in the longitudinal direction. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test. In addition, since the alloy plate is bonded to the side surface in the longitudinal direction, surface wrinkles at the end in the width direction due to the wraparound of the side surface are reduced.

  No. Examples 9 to 11 are cases in which the as-cast plasma melted ingot was used, and the varieties of the inner part 5, the layer structure, the thickness ratio of the surface layers 3 and 4 and the B content were changed and evaluated. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In Examples 12 to 14, when the cast skin surface of an EB melting ingot is cut and used, evaluation is made by changing the type of the inner 5, the layer structure, the thickness ratio of the surface layers 3 and 4, and the B content. It is. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In Examples 15 to 17, when the casting surface of the plasma melting ingot is cut and used, evaluation is made by changing the type of the interior 5, the layer structure, the thickness ratio of the surface layers 3 and 4, and the B content. It is. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In Examples 18-20, various ingots were used after ingot rolling, and the surface was cut and used, and the inner 5 varieties, the layer structure, the thickness ratio of the surface layers 3 and 4 and the B content were changed and evaluated. This is the case. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In Examples 21 to 23, after forging various ingots, the surface is cut and used. When the inner 5 varieties, the layer structure, the thickness ratio of the surface layers 3 and 4 and the B content are changed, they are evaluated. It is. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In Examples shown in 24-37, the surface is cut and used after the VAR ingot is ingot-rolled, and various titanium alloys are used as the internal 5 types, and the layer structure, the thickness ratio of the surface layers 3 and 4, It is a case where B content is changed and evaluated. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  In addition, the alloy used for the inner part 5 in the example of the present invention was subjected to a tensile test with a JIS 13B specimen having a thickness of 1.5 mm in advance, and the 0.2% proof stress was 1000 MPa or less.

  Furthermore, as a result of evaluation by the above-described method, In Comparative Example 1, the neutron beam shielding effect could not be confirmed. In all of Examples 4 to 37, the neutron shielding effect was 1 or more, and the neutron beam shielding effect could be confirmed.

  Note that the stainless steel plate (4 mm thickness) having a B content of 0.5% used in the nuclear fuel storage rack has a neutron shielding effect of 23.7. In Examples 11, 13 and 17, a higher neutron beam shielding effect was obtained than this stainless steel plate.

The neutron shielding plate shown in Table 2 as each example (example of the present invention) was manufactured by the following method.
The slab 6 subjected to plate bonding in the same procedure as in Example 1 was heated at 800 ° C. for 240 minutes using a steel facility, and then hot-rolled to form a strip coil (titanium composite) 1 having a thickness of about 20 mm. , 2 were produced. By this hot rolling, the surface layers of the titanium composites 1 and 2 were made Ti-0.1 to 3.8% B alloy. The strip coils 1 and 2 after hot rolling were passed through a continuous pickling line made of nitric hydrofluoric acid, descaled, and then visually observed for the occurrence of cracks. In addition, the measuring method of the depth of the surface layers 3 and 4 (B concentrating layer) is a part of the hot-rolled sheet (collected from the central part in the width direction at three points of the front end, the center, and the rear end in the longitudinal direction). The cut and polished material was subjected to SEM / EDS analysis, and the ratio of the B-concentrated layer to the plate thickness and the B concentration of the B-concentrated layer were determined (the average value in the observed portion was adopted).

  In addition, a total of 20 bending specimens in the L direction were sampled from the central part in the width direction at three locations, the front end, the center, and the rear end in the longitudinal direction, and bent according to JIS Z 2248 (metal material bending test method). A test was conducted. The test temperature was room temperature, a three-point bending test was performed at a bending angle up to 120 degrees, the presence or absence of cracks was evaluated, and the crack generation rate was determined.

  Moreover, evaluation of the neutron beam shielding effect used Am-Be (4.5 MeV) as a radiation source, and fixed a test piece having a thickness of 500 mm × 500 mm × 20 mm at a position 200 mm from the radiation source. The detector is installed at a position of 300 mm from the radiation source, and the peak value of the target energy is measured for each of the radiation equivalents of the industrial test pure titanium JIS type 1 and the test piece of the control test piece. The shielding effect was evaluated (industrial pure titanium JIS type 1 neutron beam shielding effect is 1, and the value of each test piece is described).

  The results are summarized in Table 2.

  No. 38-No. The comparative example of 42 and an Example are the cases where the EB melt | dissolution ingot (slab 6) as cast is used.

  No. The comparative example of 38 is a case where the same kind of pure titanium JIS type 1 as the slab 6 is used as the titanium plate 7. No cracks occurred in the hot-rolled sheet, and no cracks occurred in the bending test.

  No. In the comparative example 39, the intermediate layer is thin. The hot-rolled sheet was partially cracked, and the crack generation rate was high even in the bending test.

  No. Examples of 40 to 42 are cases in which the evaluation was made by changing the type of the interior 5, the layer structure, the thickness ratio of the surface layers 3 and 4, and the B content. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. Examples 43 to 45 are cases in which an as-cast plasma melted ingot is used, and evaluation is performed by changing the type of the inner part 5, the layer structure, the thickness ratio of the surface layers 3 and 4, and the B content. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In Examples 46 to 48, the cast skin surface of the EB melted ingot is cut and used, and evaluation is made by changing the type of the inner 5, the layer structure, the thickness ratio of the surface layers 3 and 4, and the B content. It is. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In Examples 49 to 51, the surface of the cast surface of the plasma melting ingot is cut and used. When the inner 5 type, layer structure, thickness ratio of the surface layers 3 and 4 and the B content are changed, the evaluation is performed. It is. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In Examples 52 to 54, various ingots were subjected to ingot rolling, and the surface was cut and used. Evaluation was made by changing the type of the inner 5 layer, the layer structure, the thickness ratio of the surface layers 3 and 4 and the B content. This is the case. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In Examples 55 to 57, various ingots are forged and then used after cutting the surface. When the inner 5 varieties, the layer structure, the thickness ratio of the surface layers 3 and 4 and the B content are changed, the evaluation is performed. It is. Since the thickness ratio of the surface layers 3 and 4 is within the range of 5 to 40% and the B content of the surface layers 3 and 4 is within the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In each of Examples 40 to 57, the neutron shielding effect was 1 or more, and the neutron beam shielding effect could be confirmed.

The neutron shielding plate shown in Table 3 as each example (example of the present invention) was manufactured by the following method.
The slab 6 bonded to the plate in the same procedure as in Example 1 was heated at 800 ° C. for 240 minutes using a steel facility and then hot-rolled to obtain a strip coil (titanium composite) 1 having a thickness of about 5 mm. , 2 were produced. Further, cold rolling was performed to obtain a titanium plate having a thickness of 1 mm, and as an annealing treatment, heat treatment was performed by heating to 600 to 750 ° C. in a vacuum or an inert gas atmosphere and holding for 240 minutes. The cold-rolled sheet was visually observed for cracking in the surface inspection process after annealing. In addition, the measuring method of the depth of the surface layers 3 and 4 (B concentrating layer) is a part of the cold-rolled plate (collected from the central portion in the width direction at three locations, the front end, the center, and the rear end in the longitudinal direction). The cut and polished material was subjected to SEM / EDS analysis, and the ratio of the B-concentrated layer to the plate thickness and the B concentration of the B-concentrated layer were determined (the average value in the observed portion was adopted).

  In addition, a total of 20 bending specimens in the L direction were sampled from the central part in the width direction at three locations, the front end, the center, and the rear end in the longitudinal direction, and bent according to JIS Z 2248 (metal material bending test method). A test was conducted. The test temperature was room temperature, a three-point bending test was performed at a bending angle up to 120 degrees, the presence or absence of cracks was evaluated, and the crack generation rate was determined.

  Moreover, the evaluation of the neutron beam shielding effect used Am-Be (4.5 MeV) as a radiation source, and fixed a test piece having a thickness of 500 mm × 500 mm × 1 mm at a position 200 mm from the radiation source. The detector is installed at a position of 300 mm from the radiation source, and the peak value of the target energy is measured for each of the radiation equivalents of the industrial test pure titanium JIS type 1 and the test piece of the control test piece. The shielding effect was evaluated (industrial pure titanium JIS type 1 neutron beam shielding effect is 1, and the value of each test piece is described).

  The results are summarized in Table 3.

  No. 58-No. The comparative example of 63 and an Example are the cases where the EB melt | dissolution ingot (slab 6) as cast is used.

  No. The comparative example of 58 is a case where the same kind of pure titanium JIS as the slab 6 is used as the titanium plate 7. No cracks occurred in the cold-rolled sheet, and no cracks occurred in the bending test.

  No. 59 is a case where the B content of the surface layers 3 and 4 exceeds 3.0%. The cold-rolled sheet was partially cracked, and the rate of cracking was high in the bending test.

  No. The comparative example of 60 is a case where the thickness ratio of the surface layers 3 and 4 exceeds 40%. The cold-rolled sheet was partially cracked, and the rate of cracking was high in the bending test.

  No. The examples of 61 to 63 are cases in which evaluation was made by changing the type of the inner 5 and the layer structure, the thickness ratio of the surface layers 3 and 4 and the B content. Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B content in the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are cold-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. Examples 64 to 66 are cases where evaluation was performed by using as-cast plasma melted ingots and changing the type of inner 5 and the layer structure, the thickness ratio of the surface layers 3 and 4 and the B content. Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B content in the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are cold-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In Examples 67 and 68, the cast skin surface of the EB melting ingot or the plasma melting ingot is cut and used, and the type of the inner five, the layer structure, the thickness ratio of the surface layers 3 and 4, and the B content are changed. It is a case where it evaluates. Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B content in the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are cold-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In Examples 69 to 71, various ingots were used after being ingot-rolled, and the surface was cut and used. Evaluation was made by changing the type of the inner 5 layer, the layer structure, the thickness ratio of the surface layers 3 and 4, and the B content. This is the case. Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B content in the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are cold-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In Examples 72 to 74, various ingots are forged and used after cutting the surface. When the inner 5 varieties, the layer structure, the thickness ratio of the surface layers 3 and 4 and the B content are changed, the evaluation is performed. It is. Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B content in the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are cold-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In all of the examples 61 to 74, the neutron shielding effect was 1 or more, and the neutron beam shielding effect could be confirmed.

  The neutron beam shielding plate 1 which is a titanium composite material having a two-layer structure according to the present invention shown in FIG. 1 is subjected to hot rolling after melting and re-solidifying one side surface of the base material, whereby the surface layer 3 and the inner 5 Formed. Moreover, the neutron beam shielding plate 2 having a three-layer structure according to the present invention shown in FIG. 2 is obtained by hot rolling after melting and re-solidifying the both side surfaces of the base material, so that the surface layers 3 and 4 and the inside 5 are formed. It is formed. The manufacturing method of the neutron beam shielding plates 1 and 2 will be specifically described.

  The neutron beam shielding plates 1 and 2 shown as examples (examples of the present invention) in Table 4 are manufactured by the following method.

なお、表層部には、スラブ（母材）に由来する元素が含まれるが、表には、スラブには含まれない元素の含有量のみを示している。

In addition, although the element derived from a slab (base material) is contained in a surface layer part, only content of the element which is not contained in a slab is shown in the table.

  First, a titanium ingot as a raw material was manufactured using a rectangular mold by electron beam melting (EB melting) or plasma arc melting (plasma melting) or using a cylindrical mold by VAR melting.

  As for the size of the ingot, the cylindrical ingot was 1200 mm in diameter x 2500 mm in length, and the rectangular ingot was 100 mm in thickness x 1000 mm in width x 4500 mm in length.

  Most of the cast ingots were melted and re-solidified as they were or after the cast surface on the surface of the ingot was cut. The other ingots were cut and subjected to melt re-solidification after partial rolling.

The melt resolidification treatment was performed on at least one of the rolling surfaces, and was also performed on the side surface in the longitudinal direction as necessary. This treatment is performed by electron beam welding in a vacuum atmosphere of about 3 × 10 ⁻³ Torr, and TiB ₂ powder (100 μm or less), Ti—B alloy tip (2 mm square, 1 mm thickness), Ti—B alloy at the time of melting. Any of a wire (φ5 mm or less), a Ti—B alloy thin film (20 μm or less), or a Ti—B alloy mesh (φ1 mm combined in a lattice shape) is added, and the molten resolidified layer is Ti—0.1-3 By using a 5% B alloy, a titanium slab having a two-layer structure or a three-layer structure was obtained. For the surface layers 3 and 4 (B-concentrated layer), the ratio per one side of the total thickness of the titanium composite materials 1 and 2 is shown in Table 4, and in the three-layer structure, B-concentration on both surfaces The layers were adjusted to have the same thickness.

  When various materials were added, the material containing B was uniformly dispersed over the entire rolled surface of the titanium slab so as to be uniformly added to the entire slab, and melt resolidification treatment was performed. In addition, it hold | maintained at 100 degreeC or more and less than 500 degreeC for 1 hour or more after a melt re-solidification process.

  The melted and re-solidified titanium slab was heated at 800 ° C. for 240 minutes using a steel facility, and then hot-rolled to produce a strip coil having a thickness of about 4 mm. The strip-like coil after hot rolling was passed through a continuous pickling line made of nitric hydrofluoric acid, descaled, and then visually observed for the occurrence of cracks.

  In addition, the measuring method of the depth of the surface layers 3 and 4 (B concentrating layer) is a part of the hot-rolled sheet after pickling (from the center in the width direction for three portions of the front end, center, and rear end in the longitudinal direction). Each sampled) was cut out and polished, and subjected to SEM / EDS analysis to determine the ratio of the surface layers 3 and 4 (B concentrated layer) to the plate thickness and the B concentration of the surface layers 3 and 4 (B concentrated layer) ( The average value among the observation points was adopted).

  In addition, a total of 20 bending specimens in the L direction were sampled from the central part in the width direction at three locations, the front end, the center, and the rear end in the longitudinal direction, and bent according to JIS Z 2248 (metal material bending test method). A test was conducted. The test temperature was room temperature, a three-point bending test was performed at a bending angle up to 120 degrees, the presence or absence of cracks was evaluated, and the crack generation rate was determined.

  Moreover, the evaluation of the neutron beam shielding effect used Am-Be (4.5 MeV) as a radiation source, and fixed a test piece of 500 mm × 500 mm × 4 mm thickness at a position 200 mm from the radiation source. The detector is installed at a position of 300 mm from the radiation source, and the peak value of the target energy is measured for each of the radiation equivalents of the industrial test pure titanium JIS type 1 and the test piece of the control test piece. The shielding effect was evaluated (industrial pure titanium JIS type 1 neutron beam shielding effect is 1, and the value of each test piece is described).

The results are summarized in Table 4 together with the test conditions.
No. in Table 4 Comparative examples and examples (examples of the present invention) shown in 75 to 83 are cases where an as-cast EB melting ingot is used.

  No. The comparative example of 75 is a case where the raw material containing B was not added at the time of melt re-solidification. No cracks occurred in the hot-rolled sheet, and no cracks occurred in the bending test.

  No. A comparative example of 76 is a case where the B concentration of the surface layers 3 and 4 exceeds 3.0%. The hot-rolled sheet was partially cracked, and the crack generation rate was high even in the bending test.

  No. The comparative example of 77 is a case where the thickness ratio of the surface layers 3 and 4 exceeds 40%. The hot-rolled sheet was partially cracked, and the crack generation rate was high even in the bending test.

No. In Examples 78-83 (examples of the present invention), the B-containing material was changed to TiB ₂ powder, Ti-B alloy chip, Ti-B alloy wire, Ti-B alloy thin film, and Ti-B alloy mesh, respectively. This is the case. In any case, the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40%, and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%. No cracks occurred in the plate, and no cracks occurred in the bending test.

No. Examples 84-88 (examples of the present invention) use an as-cast plasma melting ingot, and the B-containing material is TiB ₂ powder, Ti-B alloy tip, Ti-B alloy wire, Ti-B alloy thin film, It is a case where it changes and each evaluates with a Ti-B alloy mesh. In any case, the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40%, and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%. No cracks occurred in the plate, and no cracks occurred in the bending test.

No. Examples 89 to 93 (examples of the present invention) are obtained by cutting the cast skin surface of an EB melting ingot, and using B-containing materials as TiB ₂ powder, Ti-B alloy chips, Ti-B alloy wires, It is a case where it changes and evaluates with a Ti-B alloy thin film and a Ti-B alloy mesh, respectively. In the present embodiment, the melt re-solidification treatment is performed on the side surface in the longitudinal direction as well as the rolled surface. Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

No. Examples 94-98 (examples of the present invention) are obtained by cutting the cast skin surface of a plasma melting ingot and using a B-containing material as TiB ₂ powder, Ti-B alloy tip, Ti-B alloy wire, It is a case where it changes and evaluates with a Ti-B alloy thin film and a Ti-B alloy mesh, respectively. In the present embodiment, the melt re-solidification treatment is performed on the side surface in the longitudinal direction as well as the rolled surface. Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

No. Examples 99 to 101 (examples of the present invention) are the cases where various ingots are subjected to ingot rolling and the surface is cut and used, and TiB ₂ powder is used as a B-containing material during melt resolidification. . Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

No. Examples 102-104 (examples of the present invention) are obtained by forging various ingots and then cutting and using the surface. At the time of melting and re-solidification, TiB ₂ powder is used as the B-containing material. Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  In addition, the alloy used for the inner part 5 in the example of the present invention was subjected to a tensile test with a JIS 13B specimen having a thickness of 1.5 mm in advance, and the 0.2% proof stress was 1000 MPa or less.

  No. In Examples 78-104 (examples of the present invention), the neutron shielding effect was 1 or more, and the neutron beam shielding effect could be confirmed. Note that the stainless steel plate (4 mm thickness) to which 0.5% by mass of B used in the nuclear fuel storage rack is added has a neutron shielding effect of 23.7. In Examples 86, 93, 106, and 108, a higher neutron beam shielding effect was obtained than this stainless steel plate.

  The neutron beam shielding plates 1 and 2 shown in Table 5 as examples (examples of the present invention) are manufactured by the following method.

なお、表層部には、スラブ（母材）に由来する元素が含まれるが、表には、スラブには含まれない元素の含有量のみを示している。

In addition, although the element derived from a slab (base material) is contained in a surface layer part, only content of the element which is not contained in a slab is shown in the table.

  A titanium slab melted and re-solidified in the same procedure as in Example 4 was heated at 800 ° C. for 240 minutes using a steel facility, and then hot-rolled to produce a strip coil having a thickness of about 20 mm. The strip-like coil after hot rolling was passed through a continuous pickling line made of nitric hydrofluoric acid, descaled, and then visually observed for the occurrence of cracks.

  In addition, the measuring method of the depth of the surface layers 3 and 4 (B concentrating layer) is a part of the hot-rolled sheet after pickling (from the center in the width direction for three portions of the front end, center, and rear end in the longitudinal direction). Each sampled) was cut out and polished, and subjected to SEM / EDS analysis to determine the ratio of the surface layers 3 and 4 (B concentrated layer) to the plate thickness and the B concentration of the surface layers 3 and 4 (B concentrated layer) ( The average value among the observation points was adopted).

  In addition, a total of 20 bending specimens in the L direction were sampled from the central part in the width direction at three locations, the front end, the center, and the rear end in the longitudinal direction, and bent according to JIS Z 2248 (metal material bending test method). A test was conducted. The test temperature was room temperature, a three-point bending test was performed at a bending angle up to 120 degrees, the presence or absence of cracks was evaluated, and the crack generation rate was determined.

  Moreover, evaluation of the neutron beam shielding effect used Am-Be (4.5 MeV) as a radiation source, and fixed a test piece having a thickness of 500 mm × 500 mm × 20 mm at a position 200 mm from the radiation source. The detector is installed at a position of 300 mm from the radiation source, and the peak value of the target energy is measured for each of the radiation equivalents of the industrial test pure titanium JIS type 1 and the test piece of the control test piece. The shielding effect was evaluated (industrial pure titanium JIS type 1 neutron beam shielding effect is 1, and the value of each test piece is described).

The results are summarized in Table 5 together with the test conditions.
No. in Table 5 The comparative examples and examples (examples of the present invention) shown in 105 to 112 are cases where an as-cast EB melting ingot is used.

  No. The comparative example of 105 is a case where the raw material containing B was not added at the time of melt re-solidification. No cracks occurred in the hot-rolled sheet, and no cracks occurred in the bending test.

  No. 106 is a case where the B concentration of the surface layers 3 and 4 exceeds 3.0%. The hot-rolled sheet was partially cracked, and the crack generation rate was high even in the bending test.

  No. A comparative example 107 is a case where the thickness ratio of the surface layers 3 and 4 exceeds 40%. The hot-rolled sheet was partially cracked, and the crack generation rate was high even in the bending test.

No. In Examples 108-112 (examples of the present invention), the B-containing material was changed to TiB ₂ powder, Ti-B alloy tip, Ti-B alloy wire, Ti-B alloy thin film, and Ti-B alloy mesh, respectively. This is the case. In any case, the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40%, and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%. No cracks occurred in the plate, and no cracks occurred in the bending test.

No. Examples 113-117 (examples of the present invention) use an as-cast plasma melting ingot, and the B-containing material is TiB ₂ powder, Ti-B alloy tip, Ti-B alloy wire, Ti-B alloy thin film, It is a case where it changes and evaluates with each Ti-B alloy mesh. In any case, the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40%, and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%. No cracks occurred in the plate, and no cracks occurred in the bending test.

No. In Examples 118 and 119 (examples of the present invention), the cast skin surface of an EB melting ingot or a plasma melting ingot is cut and used, and TiB ₂ powder is used as a B-containing material at the time of melt resolidification. It is. Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

No. Examples 120-122 (examples of the present invention) are obtained by cutting various surfaces of ingots and then cutting the surface and using TiB ₂ powder as the B-containing material at the time of melt resolidification. . Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

No. Examples 123 to 125 (examples of the present invention) are obtained by forging various ingots and then cutting and using the surface. At the time of melt resolidification, TiB ₂ powder is used as the B-containing material. Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are hot-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In each of Examples 108 to 125 (examples of the present invention), the neutron shielding effect was 1 or more, and the neutron beam shielding effect could be confirmed.

  The neutron beam shielding plates 1 and 2 shown as examples (invention examples) in Table 6 are manufactured by the following method.

なお、表層部には、スラブ（母材）に由来する元素が含まれるが、表には、スラブには含まれない元素の含有量のみを示している。

In addition, although the element derived from a slab (base material) is contained in a surface layer part, only content of the element which is not contained in a slab is shown in the table.

  The titanium slab melted and re-solidified in the same procedure as in Example 4 was heated at 800 ° C. for 240 minutes using a steel facility, and then hot-rolled to produce a strip coil having a thickness of about 5 mm. The strip coil after hot rolling was descaled through a continuous pickling line made of nitric hydrofluoric acid. Further, cold rolling was performed to obtain a titanium plate having a thickness of 1 mm, and as an annealing treatment, heat treatment was performed by heating to 600 to 750 ° C. in a vacuum or an inert gas atmosphere and holding for 240 minutes. The cold-rolled sheet was visually observed for cracking in the surface inspection process after annealing. In addition, the measuring method of the depth of the surface layers 3 and 4 (B concentrating layer) is a part of the cold-rolled plate (collected from the central portion in the width direction at three locations, the front end, the center and the rear end in the longitudinal direction) The SEM / EDS analysis was performed on the cut and polished material, and the ratio of the surface layers 3 and 4 (B concentrated layer) to the plate thickness and the B concentration of the surface layers 3 and 4 (B concentrated layer) were obtained (in the observed portion). Was used).

  In addition, a total of 20 bending specimens in the L direction were sampled from the central part in the width direction at three locations, the front end, the center, and the rear end in the longitudinal direction, and bent according to JIS Z 2248 (metal material bending test method). A test was conducted. The test temperature was room temperature, a three-point bending test was performed at a bending angle up to 120 degrees, the presence or absence of cracks was evaluated, and the crack generation rate was determined.

  Moreover, the evaluation of the neutron beam shielding effect used Am-Be (4.5 MeV) as a radiation source, and fixed a test piece having a thickness of 500 mm × 500 mm × 1 mm at a position 200 mm from the radiation source. The detector is installed at a position 300 mm from the radiation source, and the peak value of the target energy is measured for each of the radiation equivalents of the industrial test pure titanium JIS type 1 (1 mm thickness) and the test piece (1 mm thickness). From the ratio of the values, the neutron beam shielding effect was evaluated (the value of each test piece was described with the neutron beam shielding effect of 1 type of industrial pure titanium JIS being 1).

The results are summarized in Table 6 together with the test conditions.
No. in Table 6 The comparative examples and examples (examples of the present invention) shown in 126 to 131 are cases where EB melting ingots as cast were used.

  No. The comparative example of 126 is a case where the raw material containing B was not added at the time of melt re-solidification. No cracks occurred in the cold-rolled sheet, and no cracks occurred in the bending test.

  No. In the comparative example of 127, the B concentration of the surface layers 3 and 4 exceeds 3.0%. The cold-rolled sheet was partially cracked, and the rate of cracking was high in the bending test.

  No. A comparative example of 128 is a case where the thickness ratio of the surface layers 3 and 4 exceeds 40%. The cold-rolled sheet was partially cracked, and the rate of cracking was high in the bending test.

No. Examples 129 to 131 (examples of the present invention) are cases in which the B-containing material is evaluated by changing to a TiB ₂ powder, a Ti—B alloy chip, and a Ti—B alloy wire, respectively. In any case, the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40%, and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%, so both are cold-rolled. No cracks occurred in the plate, and no cracks occurred in the bending test.

No. In Examples 132-134 (examples of the present invention), as-cast plasma melting ingots were used, and the B-containing material was evaluated by changing to TiB ₂ powder, Ti-B alloy thin film, and Ti-B alloy mesh, respectively. It is. In any case, the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40%, and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%, so both are cold-rolled. No cracks occurred in the plate, and no cracks occurred in the bending test.

No. In Examples 135 and 136 (examples of the present invention), the cast skin surface of an EB melting ingot or a plasma melting ingot is cut and used, and TiB ₂ powder is used as a B-containing material at the time of melting and resolidification. It is. Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are cold-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

No. In Examples 137 to 139 (examples of the present invention), various ingots are subjected to ingot rolling and then the surface is cut and used, and TiB ₂ powder is used as a B-containing material during re-solidification. . Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are cold-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

No. Examples 140 to 142 (examples of the present invention) are obtained by forging various ingots and then cutting and using the surface, and TiB ₂ powder is used as a B-containing material at the time of melt resolidification. Since the thickness ratio of the surface layers 3 and 4 is in the range of 5 to 40% and the B concentration of the surface layers 3 and 4 is in the range of 0.1 to 3.0%, both are cold-rolled sheets. No cracks occurred, and no cracks occurred in the bending test.

  No. In each of Examples 129 to 142 (examples of the present invention), the neutron shielding effect was 1 or more, and the neutron beam shielding effect could be confirmed.

1, 2 Titanium composites 3, 4 according to the present invention Surface layer 5 Inner layer 6 Base material (slab)
7,8 Surface material (titanium plate)
9 Welded part

Claims (7)

An inner layer made of pure titanium or titanium alloy for industrial use;
A surface layer having a chemical composition different from that of the inner layer formed on at least one rolling surface of the inner layer;
An intermediate layer formed between the inner layer and the surface layer and having a different chemical composition from the inner layer;
A titanium composite comprising:
The surface layer has a thickness of 2 μm or more, and the proportion of the total thickness is 40% or less per side,
The chemical composition of the surface layer part is mass%,
B: 0.1 to 3.0%
The balance: titanium and impurities
The intermediate layer has a thickness of 0.5 μm or more.
Titanium composite material. Other surfaces are formed on the surface other than the rolling surface of the inner layer,
The other surface layer has the same chemical composition as the surface layer,
The titanium composite according to claim 1. A base material made of pure titanium or titanium alloy for industrial use;
A surface layer material joined to at least one rolling surface of the base material;
A titanium material for hot rolling comprising a welded portion that joins the periphery of the base material and the surface layer material,
The surface layer material has a chemical composition different from that of the base material, and in mass%,
B: 0.1 to 3.0%
The balance: titanium and impurities
The welded portion shields the interface between the base material and the surface material from outside air;
Titanium material for hot rolling. Other surface layer materials are joined to a surface other than the rolling surface of the base material,
The other surface layer material has the same chemical composition as the surface layer material,
The titanium material for hot rolling according to claim 3. The base material consists of a direct cast slab,
The titanium material for hot rolling according to claim 3 or 4. The direct cast slab is obtained by forming a melt resolidified layer on at least a part of the surface.
The titanium material for hot rolling according to claim 5. The chemical composition of the melt-resolidified layer is different from the chemical composition of the center thickness of the direct cast slab,
The titanium material for hot rolling according to claim 6.

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