US20150167121A1 - Titanium alloy material - Google Patents

Titanium alloy material Download PDF

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US20150167121A1
US20150167121A1 US14/418,031 US201314418031A US2015167121A1 US 20150167121 A1 US20150167121 A1 US 20150167121A1 US 201314418031 A US201314418031 A US 201314418031A US 2015167121 A1 US2015167121 A1 US 2015167121A1
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titanium alloy
alloy material
contamination
mass
corrosion
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Inventor
Hideya Kaminaka
Kouichi Takeuchi
Hiroshi Kamio
Satoshi Matsumoto
Norio Inoue
Masaru Abe
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Nippon Steel Corp
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Nippon Steel and Sumitomo Metal Corp
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Assigned to NIPPON STEEL & SUMITOMO METAL CORPORATION reassignment NIPPON STEEL & SUMITOMO METAL CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KAMIO, HIROSHI, ABE, MASARU, INOUE, NORIO, KAMINAKA, HIDEYA, MATSUMOTO, SATOSHI, TAKEUCHI, KOUICHI
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C14/00—Alloys based on titanium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
    • C22F1/18—High-melting or refractory metals or alloys based thereon
    • C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon

Definitions

  • the present invention relates to a titanium alloy material, particularly to a titanium alloy material containing a platinum group metal.
  • Titanium is being actively used in the aircraft field and the like, utilizing its feature of lightness and strength. Further, having high corrosion resistance, titanium is beginning to be used in wide range of fields as a material for chemical industry equipment, a material for thermal and nuclear power generation equipment, and a material for seawater desalination equipment, and the like.
  • titanium can exhibit its high corrosion resistance
  • oxidizing acid nitric acid
  • neutral chloride environment such as seawater
  • titanium does not have sufficient crevice corrosion resistance in a high-temperature chloride environment, nor sufficient corrosion resistance in a non-oxidizing acid solution such as hydrochloric acid (hereinafter, in this section, the crevice corrosion resistance and the corrosion resistance are referred to as “corrosion resistance”).
  • Ti-0.15 Pd alloy (Gr. 7 and Gr. 11 according to the ASTM standard) (hereinafter, “Gr.” (Grade) complies with the ASTM standard).
  • This titanium alloy is produced by using the phenomenon that Pd in the alloy reduces hydrogen overvoltage to maintain the natural potential within a passivation range. That is, in this alloy, Pd eluted from the alloy by corrosion is precipitated again on the surface of the alloy to be deposited, and thereby hydrogen overvoltage is reduced and the natural potential is maintained within the passivation range. Accordingly, this alloy has high corrosion resistance.
  • Gr. 7 having high corrosion resistance contains Pd, which is a very expensive platinum group metal; accordingly, the fields using Gr. 7 have been limiting.
  • Patent Document 1 a titanium alloy (Gr. 17) and the like having high crevice corrosion resistance while having a lower content rate of Pd, which is 0.01 to 0.12% by mass, than Gr. 7, is proposed and put into practical use.
  • a titanium alloy containing a platinum group metal is gaining widespread use, so that the titanium alloy is beginning to be used even in a harsh environment such as a high-temperature chloride environment.
  • the titanium alloy containing a platinum group metal and having high corrosion resistance may cause corrosion that is different from pitting corrosion or so-called crevice corrosion (accompanying whitening and wastage due to the generation of TiO 2 ).
  • the present inventors have closely examined this kind of corrosion.
  • FIG. 1 is a photograph showing the outside appearance of a Gr. 17 titanium alloy material in which corrosion has occurred.
  • a corroded part often has high surface roughness (hereinafter, getting high surface roughness is referred to as “surface roughening”). Further, it is found that black matter has adhered or the titanium alloy has changed its color into black in the vicinity of the corroded part. Then, the present inventors have confirmed the existence of hydride (TiH or TiH 2 ) in the corroded part. Therefore, this corrosion is closely related to hydrogen.
  • hydride TiH or TiH 2
  • FIG. 2 is a photograph showing a cross-sectional structure of the corroded Gr. 17 titanium alloy material. On the surface of the corroded part of the titanium alloy material, a plurality of concave portions are formed (in FIG. 2 , arrows denote the parts where concave portions are formed.). From FIG. 2 , it is found that spotted or pointed substances are formed in the range from the vicinity of the surface to the inside. The present inventors have confirmed that the substances are hydride. Hydride is considered to have been generated from hydrogen that entered from the surface of the material.
  • FIG. 3 is a photograph showing a cross-sectional structure of a non-corroded Gr. 17 titanium alloy material. Surface roughening of the titanium alloy material has not progressed, and in such a titanium alloy material, there is not as much hydride as in the titanium alloy material shown in FIG. 2 , at least.
  • Patent Document 2 discloses a material having improved grain-boundary corrosion resistance by orienting precipitates (Ti 2 Ni) contained in a titanium alloy containing a platinum group along a rolling direction.
  • Patent Document 3 discloses a material in which, in order to prevent embrittlement caused by hydrogen absorption, a hydride layer is formed in advance only in the vicinity of the surface and further hydrogen absorption and hydrogen embrittlement are prevented in the usage environment of the material.
  • the present invention has been made in view of the above circumstance, and aims to provide a titanium alloy material containing a platinum group metal, the titanium alloy material being able to sufficiently suppress corrosion accompanying surface roughening.
  • the present inventors have closely studied to solve the above problems of corrosion, and have made the present invention.
  • the present invention relates to a titanium alloy material as described in the following (1) to (7).
  • an area ratio at which a signal of an Fe characteristic X-ray exceeding the maximum intensity is obtained is 0.1% or less.
  • an area ratio at which a signal of a S characteristic X-ray exceeding the maximum intensity is obtained is 0.1% or less.
  • the area ratio at which the signal of the Fe characteristic X-ray exceeding the maximum intensity is 0.05% or less and the area ratio at which the signal of the S characteristic X-ray exceeding the maximum intensity is 0.05% or less.
  • a content of Fe obtained by point analysis of part in which Fe is present on the surface of the titanium alloy material is 0.5 or less in atomic ratio of Fe with respect to Ti.
  • platinum group metal is contained in 0.01 to 0.25% by mass.
  • Pd is contained in 0.01 to 0.25% by mass as the platinum group metal.
  • the titanium alloy material according to the present invention can be used for applications that need high corrosion resistance (e.g., crevice corrosion resistance and acid resistance), resistance against corrosion progress, processability, and economic efficiency.
  • the titanium alloy material according to the present invention can be used in a harsh environment such as an anode of a brine electrolytic cell and salt processing equipment.
  • FIG. 1 is a photograph showing the outside appearance of a corroded Gr. 17 titanium alloy material.
  • FIG. 2 is a photograph showing a cross-sectional structure of a corroded Gr. 17 titanium alloy material.
  • FIG. 3 is a photograph showing a cross-sectional structure of a non-corroded Gr. 17 titanium alloy material.
  • FIG. 4 shows results of surface mapping analysis with an EPMA surface analysis apparatus for samples according to the present invention.
  • FIG. 5 shows results of surface mapping analysis with an EPMA surface analysis apparatus for samples not according to the present invention.
  • FIG. 6 is a schematic diagram of a sample used for corrosion testing and a schematic diagram of a sample for crevice corrosion testing.
  • the present invention is based on the present inventors' knowledge as follows.
  • Gr. 11, Gr. 13, and Gr. 17 materials having different surface contaminating degrees were commercially obtained and were subjected to surface analysis with an electron probe micro analyzer (EPMA) surface analysis apparatus to find out elements that are present on the surface.
  • EPMA electron probe micro analyzer
  • elements that are present on the surface are as follows.
  • C is considered to be from rolling oil used in a manufacturing process.
  • O is from a passivation film of titanium, so that O is generally observed on the surface of a titanium material.
  • Fe, Zn, and S are elements that are not observed in a general titanium alloy material, and are each defined as “surface contaminating element” in this specification.
  • Fe is in some cases added to a titanium material in order to improve strength, and such a titanium alloy material contains Fe in a base material regardless of contamination by Fe.
  • Such Fe is normally molten in the titanium material and distributed uniformly, so that, when the titanium alloy material is analyzed with the EPMA surface analysis apparatus, signals of Fe are counted as backgrounds.
  • Fe that the present application focuses on is Fe that is brought by Fe contamination and is present in a condensed state on the surface of the titanium material, without being molten therein.
  • the surface analysis detects Ca, Na, and Cl. However, the detected amounts of such elements are minute, and accordingly such elements are excluded from the contaminating elements defined in this specification. Such elements are assumed to have been adhered on the titanium alloy material mainly from humans who handled the titanium alloy material commercially.
  • the surface contamination by Fe is assumed to be from a stainless steel product or steel product produced in the same manufacturing line as the target titanium alloy material, or from a shot piece remaining on the surface of the titanium alloy material, the shot piece being used for shot peening at a time of descaling of a hot rolled sheet (Fe contamination caused by a shot piece will be described later in detail in the section “6) Method of manufacturing titanium alloy material according to the present invention”).
  • a black oxide that is assumed to be Fe 3 O 4 may be generated on the surface thereof in the crevice structure. A part where such an oxide is generated undergoes surface roughening by corrosion, as shown in FIG. 1 , and hydride is generated right below the part. Accordingly, Fe that generates oxide is considered to be related to corrosion of a titanium alloy material accompanying surface roughening.
  • Zn surface contamination by Zn is assumed to be caused by zinc phosphate that is used as a seizure prevention agent in a manufacturing process of the target titanium alloy material, and Zn remaining on the surface after rolling processing.
  • metal-like Zn is present on the surface of the titanium alloy material, heterologous metals are in contact with each other. In such a state, hydrogen absorption is promoted, and a part contaminated by Zn may generate hydride.
  • S is a component that is contained in a part of an extreme pressure additive used for rolling lubricating oil, and accordingly, surface contamination by S is assumed to be from such an additive.
  • S sulfur chloride
  • S 2 Cl 2 sulfur chloride accelerates corrosion of pure titanium, and accordingly may also have a function of progressing corrosion of a titanium alloy.
  • Fe area ratio the area ratio at which a signal of the Fe characteristic X-ray exceeding the maximum intensity
  • the Fe area ratio on the surface of the titanium alloy material needs to be 0.1% or less.
  • the Fe area ratio on the surface of the titanium alloy material in a case of F-only contamination is preferably 0.01% or less.
  • S area ratio the area ratio at which a signal of the S characteristic X-ray exceeding the maximum intensity
  • the above described commercially available material is contaminated by both Fe and S.
  • the Fe content obtained by point analysis on the part where Fe is present on the surface of the titanium alloy material is 0.5 or less in an atomic ratio of Fe to Ti.
  • the content of C (atomic %) varies by remaining fat or the like. Accordingly, the content of Fe (atomic %) also varies by being influenced by the variation of the content of C in the part there Fe is present.
  • the Fe content is regulated by the ratio of the Fe content (atomic %) to the Ti content (atomic %) which is a component of a base material.
  • a process of manufacturing a titanium alloy material is divided into a hot rolling step and a cold rolling step.
  • scale oxide
  • shot peening is performed on the surface of the hot rolled sheet obtained by hot rolling to remove scale, and in addition, a crack is given to the scale generated in the superficial layer part of the hot rolled sheet, and then acid cleaning is performed.
  • acid cleaning since acid for cleaning penetrates the crack, the remaining scale is removed easily.
  • a part of a shot piece remains on the surface of the titanium alloy material and cannot be removed completely by acid cleaning performed later.
  • the titanium alloy material that has been subjected to the hot rolling step is then subjected to cold rolling and annealing plural times until a desired sheet thickness is obtained.
  • annealing treatment bright annealing (BA) is performed in an argon atmosphere. Since descaling is not performed on the annealed titanium alloy material that has been subjected to bright annealing, contamination by Fe and S is not likely to be removed by descaling.
  • the superficial layer part of the titanium alloy material is removed by being dissolved by acid cleaning or being grinded mechanically. Further, it is more preferable to perform, before the acid cleaning, treatment with an alkali molten salt bath (salt bath which contains NaOH as a main component and to which oxidizing agents such as NaNO 3 and KNO 3 are added) (commonly known as “Kolene treatment”).
  • the removal of the superficial layer part is preferably performed every time after annealing is performed; however, the removal after the first and last annealing can efficiently remove S and Fe contamination.
  • the removal amount (thickness) at each time is 1 ⁇ m or more, preferably 5 ⁇ m or more, for a target plane of the titanium alloy material.
  • treatment for removal of the contamination source is not limited to once, but plural times of treatment may be needed to achieve the surface as defined in the present invention.
  • the hot rolled sheet After descaling of the hot rolled sheet, it is also effective to perform both cleaning with the aqueous solution of ferric chloride and brushing of the surface of the hot rolled steel sheet.
  • the aqueous solution of ferric chloride does not hardly dissolve titanium but dissolves Fe faster than a mixed solution of fluonitric acid, so that a shot piece and a titanium base material on the shot piece side are dissolved, and brushing treatment performed concurrently can remove the shot piece efficiently. This step becomes necessary in a case of using a large shot piece.
  • the content of a platinum group metal is preferably 0.01 to 0.25% by mass. Thus, the raw material cost can be suppressed and the corrosion resistance of the titanium alloy material can be obtained.
  • the platinum group metal may be Pd, for example.
  • the titanium alloy material according to the present invention may further contain one or more selected from the group consisting of Ni in 0.05 to 1.0% by mass, Cr in 0.05 to 0.3% by mass, and Mo in 0.05 to 0.5% by mass.
  • the titanium alloy material has higher crevice corrosion resistance. Note that, this effect saturates when Ni in more than 1.0% by mass is contained. Further, processability is reduced by the addition of Ni. Accordingly, in a case of adding Ni, it is preferable to set the content thereof to 1.0% by mass or less. In order to surely obtain the above effect, it is preferable to set the content of Ni to 0.05% by mass or more, more preferably 0.1% by mass or more.
  • the titanium alloy material has higher crevice corrosion resistance. Note that, this effect saturates when Cr in more than 0.3% by mass is contained. Accordingly, in a case of adding Cr, it is preferable to set the content thereof to 0.3% by mass or less. In order to surely obtain the above effect, it is preferable to set the content of Cr to 0.05% by mass or more.
  • the titanium alloy material has higher crevice corrosion resistance and higher resistance against sulfuric acid. Note that, this effect saturates when Mo in more than 0.5% by mass is contained. Further, processability is reduced by the addition of Mo. Accordingly, in a case of adding Mo, it is preferable to set the content thereof to 0.5% by mass or less. In order to surely obtain the above effect, it is preferable to set the content of Mo to 0.05% by mass or more.
  • Base materials used for the samples each have a sheet thickness of 3 mm, are Gr. 11, Gr. 13, Gr. 17, Gr. 33 materials according to the ASTM standard and a laboratory sample material (fabricated by performing vacuum arc remelting (VAR), hot forging, and hot rolling in order), and have compositions shown in Table 1. After defatting and ultrasonic cleaning were performed on these base materials, the following treatment was performed in order to reproduce contamination at the time of manufacture using actual equipment.
  • VAR vacuum arc remelting
  • Table 2 shows conditions for fabrication of samples provided for the corrosion testing and contamination amounts of Fe and S in the samples.
  • the mixing rates of iron powder in a rolling lubricating agent and an extreme-pressure additive to be applied onto the base materials were adjusted in a manner that the contamination amounts of Fe and S became different among the samples (Example 4 to Example 16 and Comparative Example 1 to Comparative Example 12 in Table 2).
  • FEE13PB iron powder (purity: 2 Nup, grain size: 3 to 5 ⁇ m) produced by Kojundo Chemical Laboratory Co., Ltd. was mixed to rolling lubricating oil containing palm oil as a main component in various amounts (% by mass) as shown in Table 2, this rolling lubricating oil was applied onto the base materials with a sheet thickness of 4 mm, and the base materials were rolled so that the sheet thickness became 3 mm. In this manner, remaining shot pieces at the time of shot peening were imitated, and samples having different amounts of Fe contamination (Fe contamination degrees) were obtained.
  • DAILUBE GS-440L olefin metal working oil (preliminary sulfurizing agent containing sulfur in 40%) which is an extreme-pressure additive produced by DIC Corporation was mixed to rolling lubricating oil in % by mass as shown in Table 2, this rolling lubricating oil was applied onto the base materials with a sheet thickness of 4 mm, and the base materials were rolled so that the sheet thickness became 3 mm. In this manner, samples having different amounts of S contamination (S contamination degrees) were obtained.
  • Samples denoted by “(clean material)” (Example 1 to Example 3) in Table 2 were not subjected to contamination treatment of Fe and S. That is, these samples were obtained by applying a rolling lubricating agent, to which neither Fe (iron powder) nor S (extreme-pressure additive containing sulfur) were added, onto base materials with a sheet thickness of 4 mm, and by rolling the base materials so that the sheet thickness became 3 mm.
  • the rolled materials obtained through treatment (i) to (iv) were subjected to annealing treatment in an Ar atmosphere furnace at 750° C. for 30 minutes, and then to fluonitric acid cleaning to be provided for corrosion testing.
  • a sample denoted by “(Kolene treatment) (Example 16) in Table 2 was obtained by performing Kolene treatment after the above described treatment of Fe contamination and before fluonitric acid cleaning.
  • the Kolene treatment or treatment using an aqueous solution of ferric chloride (including brushing treatment) was performed.
  • fluonitric cleaning was performed twice, which is before and after annealing.
  • the samples before corrosion treatment were subjected to surface analysis with the EPMA surface analysis apparatus.
  • Apparatus JXA-8530F produced by JEOL Ltd.
  • LIFH for Fe K ⁇ -ray
  • PETH for S K ⁇ -ray
  • LIF for Ti K ⁇ -ray
  • LIFH for Zn K ⁇ -ray
  • High-purity Ti of standards (UHV STANDARDS) for electron spectroscopy for chemical analysis (ESCA), auger electron spectroscopy (AES), and EPMA was analyzed under the above described conditions, background count intensity of Fe, S, and Zn was measured at 500 ⁇ 500 points arranged in a lattice, and average values N(Fe), N(S), and N(Zn) of background counts (intensity) of the respective elements were calculated.
  • Non-Patent Document 1 when the average value of a plurality of measured values N is set to N 0 , the ratio of the measured value N being beyond the range of N 0 ⁇ 3N 0 1/2 is 0.3%. Accordingly, by substituting the average value of background intensity to N 0 in this equation, the obtained value can be set as the threshold to distinct a signal whose intensity is raised by an existing element from the background signal.
  • the threshold intensity for Fe, S, and Zn is as follows.
  • threshold intensity for Fe is 25 counts (cnt), 15 cnt, and 50 cnt, respectively.
  • the rate of points at which the intensity higher than the threshold intensity is counted is defined as contamination area ratio.
  • the contamination area ratio is as follows.
  • FIG. 4 and FIG. 5 shows results of the surface mapping analysis with an EPMA surface analysis apparatus for the samples according to the present invention and the samples not according to the present invention.
  • points are binarized depending on whether or not the value is higher than the threshold intensity; a point having intensity less than or equal to the threshold intensity is shown in black, and a point having intensity over the threshold intensity is shown in white.
  • FIG. 4 shows results of analysis of the sample of “Example 3 (clean material)” in Table 2. In this sample, it is found that, for each of Fe, S, and Zn, there are almost no points having intensity over the threshold intensity.
  • FIG. 5 shows results of analysis of the sample of “Comparative Example 6” in Table 2. This sample was obtained by performing contamination treatment of both Fe and S. From the analysis results in FIG. 5 , it is found that, for both Fe and S, there are points having intensity over the threshold intensity throughout the analyzed region.
  • Quantitative concentration of contaminants can be measured by using general analyzing means such as EPMA or AES.
  • general analyzing means such as EPMA or AES.
  • FE-AES field emission-auger electron spectroscopy
  • Model 680 produced by ULVAC-PHI Incorporated.
  • Detection depth Several nanometers (for Ti and Fe, 3 to 5 nm)
  • FIG. 6 is a schematic diagram of a sample used for corrosion testing and a schematic diagram of a sample for crevice corrosion testing.
  • a sample 1 provided for corrosion testing has a thickness of 3 mm and a plane shape of a 30-mm square, in which, in a central portion, a hole with a diameter of 7 mm is formed.
  • Two samples 1 formed under the same conditions were disposed on opposite sides of a crevice formation film (crevice formation material) 2 as shown in FIG. 6( c ).
  • a bolt of a CP Ti bolt-nut 4 was made to penetrate the hole of the sample 1 , and the CP Ti bolt-nut 4 was tightened between the samples 1 via a PTFE bush 3 . In this manner, a sample for crevice corrosion testing 5 was obtained.
  • the surface skin of the samples 1 was made to maintain the state at the time when the treatment described in the section “1. Method of fabricating sample used for corrosion resistance testing” above was completed.
  • a NEOFLON (trademark) PCTFE film (thickness: 50 ⁇ m) produced by DAIKIN INDUSTRIES, LTD. was used as the crevice formation film 2 .
  • a CP Ti bolt-nut 4 a bolt-nut that was heated by a gas burner, the surface of which was oxidized sufficiently, was used.
  • the tightening torque of the CP Ti bolt-nut 4 was 40 kgf ⁇ cm (1 kgf is approximately 9.8 N).
  • the sample was subjected to treatment using an autoclave (autoclave treatment).
  • autoclave treatment Prior to the autoclave treatment, as a pre-measurement of testing, the weight of the samples 1 was measured by a precision balance. The weight of the samples 1 was in a range from 11 to 11.5 g. After that, the sample for crevice corrosion testing 5 was subjected to treatment using the autoclave. Conditions for the autoclave treatment are shown in Table 3.
  • Corrosion weight loss D (mg) Weight after corrosion treatment (mg) ⁇ Weight before corrosion treatment (mg)
  • the weight of each of the two samples 1 (on the bolt side and on the nut side) of the sample for crevice corrosion testing 5 was measured, and the average value of the corrosion weight losses of these two samples was set as the corrosion weight loss D of the sample for crevice corrosion testing 5 .
  • Table 4 shows base materials of the samples 1 provided for the corrosion testing, the Fe area ratios, the S area ratios, and results of the corrosion testing.
  • non-complex contamination sample The Fe area ratios of the samples of “Example 1 (clean material)” to “Example 3 (clean material)”, “Example 4” to “Example 7”, “Example 9” to “Example 11”, and “Example 14” (hereinafter these samples are each referred to as “non-complex contamination sample”) were each 0.1% or less, and accordingly, the Fe contamination degree on the surface was low. In the same manner, the S area ratios of the non-complex contamination samples were each 0.1% or less, and accordingly, the S contamination degree on the surface was low.
  • non-complex contamination samples corrosion weight loss due to corrosion treatment was not recognized, and it is obvious that the non-complex contamination samples have high corrosion resistance. Furthermore, the increased amount of hydrogen H due to corrosion treatment on the non-complex contamination samples was 20 ppm or less.
  • the non-complex contamination samples on samples whose Fe area ratio is 0.01% or less (Examples 1 to 3, 6,7,11, and 16), surface roughening was not recognized on the plane that became a crevice. Accordingly, the samples have extremely high corrosion resistance, and the absorbed amount of hydrogen is less than 10 ppm, which is extremely small.
  • Example 16 As described in the section “(v) Treatment after rolling”, the sample of Example 16 was obtained by performing Kolene treatment after Fe contamination treatment (in which rolling lubricating oil mixed with iron powder was applied and rolling was performed) and before fluonitric acid cleaning. Although the sample of Example 16 was subjected to Fe contamination treatment, it showed almost as low Fe contamination area ratio as a clean material, so that it is found that Kolene treatment is effective to obtain a titanium alloy material having a clean surface.
  • corrosion resistance (crevice corrosion resistance: resistance against corrosion accompanying surface roughening) that is much higher than before can be secured by suppressing the contamination amounts of Fe and S that are present on the surface of the titanium alloy material.
  • Table 5 shows conditions for fabricating samples provided for testing and evaluation results.
  • Samples of Examples 17, 19, and 21 were each obtained by rolling a base material with a thickness of approximately 4 mm through two-time passes in a manner that the thickness of each sample was reduced to 3.5 mm through the first pass and was again reduced to 3.0 mm through the second pass. Meanwhile, samples of Examples 18 and 20 were each obtained by rolling a base material with a thickness of approximately 4 mm through one-time pass in a manner that the thickness thereof became 3.0 mm. Further, samples of Comparative Examples 13, 14, and 15 were each obtained by rolling a base material with a thickness of approximately 4 mm through one-time pass in a manner that the thickness thereof became 3.0 mm.
  • the Fe area ratio and the S area ratio were measured, quantitative analysis was performed in a part of each region in which maximum Fe intensity was obtained, and the ratio of the Fe content (atomic %) to the Ti content (atomic %) was calculated.
  • the average values of the five regions are shown in Table 5 as Fe/Ti (atomic ratio) representing each sample.
  • Example 17 to 21 and the samples of Comparative Examples 13 to 15 were subjected to the autoclave treatment (corrosion treatment) under the conditions shown in Table 3, and hydrogen content rates before and after the treatment were analyzed.
  • Example 3 samples whose Fe/Ti (atomic ratio) exceeded 0.5 (Examples 18, 20, and 21) are also within the scope of the present invention. However, considering a case of being used in an environment in which hydrogen embrittlement might occur (high-temperature environment), it is preferable that Fe/Ti (atomic ratio) is 0.5 or less.

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US11814703B2 (en) 2015-07-29 2023-11-14 Nippon Steel Corporation Titanium material for hot working

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ES2675167T3 (es) * 2012-07-13 2018-07-09 X-Chem, Inc. Bibliotecas codificadas por ADN que tienen enlaces oligonucleotídicos codificantes no legibles por polimerasas
JP6536076B2 (ja) * 2015-02-24 2019-07-03 日本製鉄株式会社 チタン板とその製造方法
CN113260734B (zh) * 2019-01-23 2024-01-05 日本制铁株式会社 钛材和涂装钛材

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