JP2006095589A - Surface hardening method for titanium material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface hardening method for titanium material which can provide a homogeneous hardened layer in a stable state. <P>SOLUTION: An overlaying is carried out on a surface of a base metal composed of a titanium material using a filler rod composed of a titanium material containing a hardening element which forms a solid solution with the titanium material and hardens the titanium material. The titanium material in the base metal and the titanium material in the filler rod form a fusion zone of the titanium material in overlaying and the hardening element in the filler rod is mixed into the titanium material in a molten state. The hardening element and the titanium material form the solid solution through mixing and compose a hardened layer with the hardening element in the solid solution state on the surface of the base metal. Thus, the surface hardened layer with a stable and homogeneous quality is formed on the surface of the titanium base metal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface hardening method for a titanium material that performs surface hardening on the titanium material very efficiently.

Titanium alloys have high specific strength and excellent corrosion resistance, and are suitable for use in structural materials that require hardness in addition to knives and blades. Here, as a processing method for curing a conventional titanium alloy, for example, there are a gas nitriding method and a plasma nitriding method, and according to this method, a hard layer (from TiN and TiN ₂₎ that exhibits a golden color on the surface of the titanium alloy. And a hard layer can be formed on the base material side by diffusion and solid solution of nitrogen. This method is convenient as a treatment method and has the advantage that the wear resistance can be remarkably improved.

  However, the gas nitriding method and the plasma nitriding method are batch processing, and are performed at a temperature of 850 ° C. or higher for mainly 10 hours or longer. Therefore, there is a problem that a large amount of continuous treatment cannot be performed and the mechanical properties of the base material are deteriorated. Moreover, even if only the sliding part needs to be cured, such as a sliding member, the entire surface of the member may be cured, resulting in inconvenience that subsequent machining becomes difficult.

Therefore, there is a method in which the surface of the titanium metal is arc-melted using nitrogen gas as a shielding gas, and nitrogen is mixed in the molten pool and solidified to solidify the nitrogen in the molten solidified portion and partially strengthen the titanium material. (Patent Documents 1 and 2 below).
JP 11-36083 A JP 2001-207246 A

  However, the methods described in Patent Documents 1 and 2 both arc-melt the surface of the titanium ingot using nitrogen gas as a shielding gas and mix nitrogen in the shielding gas into the molten pool. There is a problem that the mixed state of nitrogen varies depending on the state, that is, the molten state of the metal and the shield state of the shielding gas, and it is difficult to obtain a uniform hardened layer in a stable state.

  This invention is made | formed in view of such a situation, and the objective is to provide the surface hardening method of the titanium material obtained in the stable state of a uniform hardening layer.

  In order to achieve the above object, the surface hardening method of the titanium material of the present invention is formed from a titanium material containing a hardening element that solidifies with the titanium material and hardens the titanium material with respect to the surface of the bare metal made of the titanium material. The gist is to form a hardened layer in which the hardened element is solid-solved on the surface of the bare metal by performing overlay welding using the melted rod.

  The surface hardening method of the titanium material of the present invention uses a filler rod formed from a titanium material containing a hardening element that solidifies with the titanium material and hardens the titanium material with respect to the surface of the bare metal made of the titanium material. By performing overlay welding, the hardening elements contained in the filler bar are mixed into the molten pool of titanium material formed by welding the surface of the metal bar and the filler bar, and also into the metal around the molten pool. Also spread. And by such mixing and diffusion, the hardening element is dissolved in the titanium material, and a hardened layer is formed on the surface of the metal. That is, the phenomenon is that the filler rod directly melts into the base metal, so that the hardened element in the filler rod is surely mixed into the base metal to form a solid solution layer, that is, a hardened layer, and a uniform and stable hardened layer. Can be configured.

  In this way, the filler rod is in a molten state together with the base metal, and the hardening element contained in the filler rod is mixed into the molten pool formed by welding to cause a solid solution. The hardened element can be reliably dissolved, and a hardened surface layer having the expected physical properties can be formed. Furthermore, in the manufacturing process of the filler rod, the amount of the hardening element contained in the filler rod can be easily controlled, so that the amount and distribution state of the hardening element mixed in the titanium material from the filler rod is controlled to be optimized. It is easy to form a high-quality cured layer with no unevenness in the cured state. Also, in this case, for example, when overlay welding is performed by arc welding, welding conditions such as arc current, arc voltage, arc length can be accurately set to predetermined values, so that the overlay welding itself is performed in a predetermined overlay state. It is possible to form a high-quality cured layer as intended.

  In the surface hardening method of the titanium material of the present invention, when depositing compound particles of titanium and a hardening element in the hardened layer by the overlay welding, for example, a hard ceramic or an intermetallic compound having a very high hardness. When the compound particles are precipitated in the titanium material, the hardness of the hardened layer is further increased.

  In the surface hardening method of the titanium material of the present invention, titanium and the hardening element are formed in the hardened layer by performing the overlay welding in a state where the compound powder of the hardening element and the metal is present on the surface of the metal. In the state where the compound particles are dispersed in the hardened layer formed by mixing the compound powder of the hardened element and the metal into the molten pool at the time of overlay welding. Precipitates and the hardness of the hardened layer is further increased.

  In the surface hardening method for titanium material of the present invention, the compound powder of the hardening element and metal is present in the filler rod, and the build-up welding is performed with the filler rod, whereby titanium in the hardened layer is obtained. In the case where the compound particles of the hardening element are deposited, since the compound powder exists in the filler rod, the compound powder of the hardening element and the metal is mixed in the molten pool at the time of overlay welding. As a result, the compound particles are precipitated in a dispersed state in the cured layer to be formed, and the hardness of the cured layer is further increased.

  Next, the best mode for carrying out the present invention will be described.

  The surface hardening method of the titanium material of the present invention uses a filler rod formed from a titanium material containing a hardening element that solidifies with the titanium material and hardens the titanium material with respect to the surface of the bare metal made of the titanium material. Perform overlay welding.

  As the titanium material, industrial pure titanium materials, titanium-based corrosion-resistant alloys, α-type titanium alloys, near-α-type titanium alloys, β-type titanium alloys, α + β-type titanium alloys, and the like can be applied. is not. In other words, any of pure industrial titanium materials, titanium-based corrosion resistant alloys, α-type titanium alloys, near α-type titanium alloys, β-type titanium alloys, α + β-type titanium alloys, etc. As the titanium material of the filler rod, any of industrial pure titanium material, titanium-based corrosion resistant alloy, α-type titanium alloy, near α-type titanium alloy, β-type titanium alloy, α + β-type titanium alloy, etc. may be applied. .

  More specifically, examples of the titanium-based corrosion-resistant alloy include Ti-0.15Pd alloy, Ti-0.3Mo alloy, Ti-5Ta alloy, etc., but are not limited thereto. Various things can be used.

  The α-type titanium alloy is not particularly limited as long as the base material exhibits a dense hexagonal α-phase at room temperature, and various types can be applied. For example, Ti-5Al-2.5Sn alloy, Ti-5.5Al-3.5Sn-3Zr-1Nb-0.3Mo-0.3Si alloy, Ti-2.5Cu alloy, etc. can be mentioned.

  Moreover, it does not specifically limit as said near alpha type titanium alloy, Various things can be applied. For example, Ti-8Al-1Mo-1V alloy, Ti-2.25Al-11Sn-5Zr-1Mo-0.2Si alloy, Ti-6Al-2Sn-4Zr-2Mo alloy, Ti-5Al-5Sn-2Zr-2Mo-0 .25Si alloy, Ti-6Al-2Nb-1Ta-0.8Mo alloy, Ti-6Al-2Sn-1.5Zr-1Mo-0.35Bi-0.1Si alloy, Ti-6Al-5Zr-0.5Mo-0. 2Si alloy, Ti-5Al-6Sn-2Zr-1Mo-0.25Si alloy, etc. can be mentioned.

  In addition, the α + β type titanium alloy is not particularly limited, and various types can be applied. For example, Ti-8Mn alloy, Ti-3Al-2.5V alloy, Ti-6Al-4V alloy, Ti-6Al-6V-2Sn alloy, Ti-7Al-4Mo alloy, Ti-6Al-2Sn-4Zr-6Mo alloy, Ti-6Al-2Sn-2Zr-2Mo-2Cr-0.25Si alloy, Ti-10V-2Fe-3Al alloy, Ti-4Al-2Sn-4Mo-0.5Si alloy, Ti-4Al-4Sn-4Mo-0.5Si Alloy, Ti-2.25Al-11Sn-4Mo-0.2Si alloy, Ti-5Al-2Zr-4Mo-4Cr alloy, Ti-4.5Al-5Mo-1.5Cr alloy, Ti-6Al-5Zr-4Mo-1Cu -0.2Si alloy etc. can be mention | raise | lifted.

  The β-type titanium alloy is not particularly limited as long as the base material exhibits a body-centered cubic β-phase at room temperature, and various types can be applied. For example, Ti-13V-11Cr-3Al alloy, Ti-8Mo-8V-2Fe-3Al alloy, Ti-3Al-8V-6Cr-4Mo-4Zr alloy, Ti-11.5Mo-6Zr-4.5Sn alloy, Ti- 11V-11Zr-2Al-2Sn alloy, Ti-15Mo-5Zr alloy, Ti-15Mo-5Zr-3Al alloy, Ti-15V-3Cr-3Al-3Sn alloy, Ti-20V-4Al-1Sn alloy, Ti-22V-4Al An alloy etc. can be mention | raise | lifted.

  The combination of the titanium material used for the bare metal and the titanium material used for the filler rod is a combination of the same type of titanium material from the viewpoint of material stability of the weld metal part by welding between the bare metal and the filler rod. Is preferably used. That is, when α-type titanium alloy is used for the metal, the filler rod is also α-type titanium alloy, and when β-type titanium alloy is used for the metal, the filler bar is also β-type titanium alloy and α + β is used for the metal. When a type titanium alloy is used, it is preferable to use an α + β type titanium alloy for the filler rod. Moreover, when a pure titanium material is used for the filler rod, any type of titanium material may be used for the base metal.

  The base metal made of the titanium material and the target material for the surface hardening treatment can be a flat plate or a block-shaped one. If necessary, a predetermined product shape (including a net shape) may be formed by performing plastic working such as cold working or hot working, cutting work, or the like in advance. In addition, the titanium material as a bullion includes not only a melted material but also a material obtained by a powder metallurgy method such as HIP sintering.

  Examples of the above-mentioned hardening element are elements that penetrate and dissolve in the lattice of the metal crystal to harden the material, and examples thereof include carbon, nitrogen, boron, oxygen, and the like. These hardening elements are contained in the titanium material forming the filler rod.

  A filler rod containing such a hardening element can be produced, for example, as follows. For example, a titanium material rod or wire is subjected to gas nitriding, plasma nitriding, or salt bath nitriding immersed in a nitriding salt bath for a predetermined time in an atmosphere of a nitriding gas. A filler rod containing nitrogen can be formed. Similarly, a carbon-containing filler rod can be formed by carburizing titanium rods or wires, and carbon-nitrogen-containing filler rods can be formed by carbonitriding. it can. In addition, a boron-containing filler rod can be formed by performing a boriding process (boronizing) on the rod or wire of the material.

  When the hardening element is contained by such a surface treatment method, for example, two or more kinds of hardening elements can be contained by performing nitriding treatment and carburizing treatment simultaneously or sequentially.

  As another method, when titanium material is heated and melted, nitrogen gas is blown into the molten titanium material, or powdered carbon is mixed into the molten titanium material and solidified to solidify the titanium ingot containing nitrogen or carbon. Can be processed into a rod or wire to form a filler rod containing nitrogen and carbon.

  In addition, as a method of causing the compound powder to exist in the filler rod, the compound powder is mixed in a binder solution and applied to the surface of the filler rod, or the filler rod is hollowed and contained therein. It can also be filled with compound powder.

  In the present invention, by performing overlay welding on a bare metal made of a titanium material using the filler rod obtained as described above, a hardened layer in which the hardening element is dissolved in the surface of the bare metal is formed. To do.

  By doing so, the hardening elements contained in the filler rod are mixed into the molten pool of titanium material formed by welding the surface of the metal rod and the filler rod, and also diffused into the metal around the molten pool. To do. And by such mixing and diffusion, the hardening element is dissolved in the titanium material, and a hardened layer is formed on the surface of the metal. That is, the phenomenon is that the filler rod directly melts into the base metal, so that the hardened element in the filler rod is surely mixed into the base metal to form a solid solution layer, that is, a hardened layer, and a uniform and stable hardened layer. Can be configured.

  In this way, the filler rod is in a molten state together with the base metal, and the hardening element contained in the filler rod is mixed into the molten pool formed by welding to cause a solid solution. The hardened element can be reliably dissolved, and a hardened surface layer having the expected physical properties can be formed. Furthermore, in the manufacturing process of the filler rod, the amount of the hardening element contained in the filler rod can be easily controlled, so that the amount and distribution state of the hardening element mixed in the titanium material from the filler rod is controlled to be optimized. It is easy to form a high-quality cured layer with no unevenness in the cured state.

  For the overlay welding as described above, for example, MIG welding can be adopted. The base metal is supported by a predetermined welding jig and arc welding is performed using the filler bar as a consumable electrode, thereby generating an arc between the filler bar and the base metal, melting the base metal and melting the base metal. It is performed while melting the bar and moving it to the melting basin. In this way, the weld metal portion formed by solidification of the molten pool forms a hardened layer in which the hardened element of the filler rod is transferred to form a solid solution. Further, the hardening element of the filler rod moves to the molten pool and then diffuses and penetrates into the surrounding metal around the molten pool to harden the diffusion region. Such a hardened layer is provided on a sliding portion of the product. Thus, a hardened layer can be formed only in a required part by the welding operation of arc welding. In addition, since overlay welding is performed by arc welding, welding conditions such as arc current, arc voltage, and arc length can be accurately set to predetermined values, so that overlay welding itself can be put into a predetermined overlay state. And a high-quality cured layer can be formed as intended.

  The diameter of the filler rod at this time is set to about 0.8 to 5 mm, and the length of the arc column between the tip of the filler rod and the product is set to about 1 to 5 mm. The arc current is set within a range of 20 to 500 A, and the arc voltage is set within a range of 20 to 40V.

  In addition, if necessary, surface hardening may be performed over a wide area of a predetermined part of the product by operating the MIG welding apparatus and performing a weaving operation in which the filler rod moves in a meandering or zigzag manner. This is effective for improving productivity.

  After that, in order to smooth the sliding portion of the product and to obtain a normal operation of the product, the place of the overlay welding is polished to form a flat operation surface. Since the molten part of the titanium material reaches the depth region of the product ingot, the hardened elements are uniformly distributed on the surface even after polishing, ensuring the wear resistance of the product. can do.

  The welding technique for performing the build-up welding is not limited to the above-described MIG welding, and various gas shield welding methods such as TIG welding, MIG welding, various arc welding such as covering arc welding, etc. are adopted. can do.

  At this time, for the purpose of adjusting the hardness, precipitation heat treatment can be performed at 600 ° C. or less × 1 to 40 hours after welding. Further, when the build-up material is a β alloy, the aging treatment is performed at 350 to 600 ° C. for 1 to 40 hours.

  Here, in the build-up welding as described above, the hardened layer is formed by solid solution hardening of the hardened element as described above, but further, compound particles of titanium and the hardened element are contained in the hardened layer. It can be deposited to promote the surface hardening of the product. By doing so, compound welding having extremely high hardness is precipitated and dispersed in the titanium material as hard ceramics, intermetallic compounds or the like by the build-up welding, and the hardness of the hardened layer is further increased.

  Specifically, the build-up welding is performed in a state where the compound powder of the hardened element and the metal is present on the surface of the metal, thereby depositing compound particles of titanium and the hardened element in the hardened layer. Can be made. By doing so, the above compound powder is mixed in the molten titanium material at the time of overlay welding, and titanium and nitrogen or titanium and carbon are precipitated and dispersed as titanium nitride or titanium carbide compound particles, and the hardened layer The hardness of this is further increased.

  That is, before performing overlay welding on the product surface, a compound powder of a hardening element and a metal, for example, a compound powder formed from chromium nitride, chromium carbide, iron carbide, etc., is applied to the surface of a predetermined part of the product at a predetermined thickness. Now arrange them in layers. In this state, when overlay welding is performed on the region where the carbide powder is disposed with the filler rod, chromium nitride, chromium carbide, iron carbide, etc. are dissolved in the molten titanium material. At this time, chromium nitride, chromium carbide Also, nitrogen and carbon separated from iron carbide and the like precipitate and disperse extremely hard compound particles such as titanium nitride and titanium carbide with titanium. Titanium has the property of easily precipitating a compound between nitrogen and carbon, so that precipitation and dispersion of titanium nitride and titanium carbide are ensured. As described above, the hardness of the product surface can be further increased and the product performance can be improved by supplementarily interposing chromium nitride, chromium carbide and iron carbide in the build-up welding process. .

  Also, the compound powder of titanium and the hardening element is precipitated in the hardened layer by causing the powder of the hardening element and metal to exist in the filler bar and performing the build-up welding with the filler bar. Can be made. By doing so, the above compound powder is mixed in the molten titanium material at the time of overlay welding, and titanium and nitrogen or titanium and carbon are precipitated and dispersed as titanium nitride or titanium carbide compound particles, and the hardened layer The hardness of this is further increased.

  That is, as described in the above method of making the filler rod, when overlay welding is performed in a state where powders such as chromium nitride, chromium carbide and iron carbide are integrated in the filler rod in the filler rod. In this case, chromium nitride, chromium carbide, iron carbide, etc. are dissolved in the molten titanium material. At this time, nitrogen and carbon separated from chromium nitride, chromium carbide, iron carbide, etc. Such extremely hard compound particles are deposited and dispersed. As described above, the hardness of the product surface can be further increased and the product performance can be improved by supplementarily interposing chromium nitride, chromium carbide and iron carbide in the build-up welding process. .

  Next, examples will be described.

Overlay welding with nitriding welding rod
i. Production of MIG welding rod or TIG welding rod MIG welding rod or TIG welding rod was produced under the conditions shown in Table 1 below.

ii. Build-up welding Next, build-up welding was performed only on the blade portion that requires the wear resistance of the product after the annealing and aging treatment of the build-up material after molding. The welding conditions for overlay welding were a current value of 70 A, a voltage value of 20 V, and an arc column length of 2.5 mm. For the purpose of adjusting the hardness, precipitation heat treatment was performed at 600 ° C. or lower for about 1 to 40 hours after welding.

iii. Table 2 below shows the results of measuring the nitrogen content and hardness of the built-up part of the built-up welded product obtained as described above.

  Thus, the thing of Hv500-600 was able to be obtained as the hardness of a welding part. On the other hand, the hardness of the core part was Hv 400 or less (about 350).

The present invention can be applied to titanium materials and titanium products used for spike fittings, sliding materials, wear-resistant members, chemical plants, petroleum refining plants, nuclear power plants, seawater desalination devices, and the like.

Claims (4)

  By performing build-up welding on the surface of the bare metal made of titanium material using a filler rod formed of a titanium material containing a hardening element that is solid-solved with the titanium material and hardens the titanium material, A method for hardening a surface of a titanium material, comprising forming a hardened layer in which the hardened element is dissolved in a gold surface.   The surface hardening method of the titanium material of Claim 1 which deposits the compound particle | grains of titanium and a hardening element in the said hardened layer by the said build-up welding.   The compound particles of titanium and a hardening element are deposited in the hardened layer by performing the build-up welding in a state where the compound powder of the hardening element and a metal is present on the surface of the metal. 3. A method for hardening a surface of a titanium material according to 2.   Claims for precipitating compound particles of titanium and a hardening element in the hardened layer by causing the powder of the hardening element and metal to exist in the filler bar and performing the build-up welding with the filler rod. Item 3. A method for surface hardening a titanium material according to Item 1 or 2.