JP2014522452A - Production of metal or alloy objects - Google Patents

Abstract

  A method of producing an object is disclosed, wherein the object is made of metal or alloy, has a desired shape, and is non-porous. The method provides some metal or alloy having a first average solute level and performs a net shape or near net shape manufacturing process using the provided metal or alloy to produce an intermediate object. The intermediate object has a desired shape, is non-porous, and has a second average solute level. The second average solute level is greater than or equal to the first average solute level. The method further performs a solute level changing step on the intermediate object to change the at least bulk solute level of the intermediate object to provide a third average solute level in the intermediate object, thereby providing the object. The third average solute level is different from the second average solute level.

Description

  The present invention relates to the production of objects, in particular objects made of metals or alloys.

  Titanium alloys are used in many market sectors, including the aerospace, medical, sports, and leisure sectors.

  In general, the manufacture of titanium alloy parts or members is performed by a machining process or a combination of forging and machining processes. Some parts are also made using casting and powder metallurgy routes.

  Generally, a titanium alloy contains oxygen in a solid solution. Oxygen tends to strengthen and harden the alloy. However, if the oxygen level in the alloy is too high, the toughness and ductility can be reduced.

  Titanium has a relatively strong affinity for absorbing oxygen. Many processing operations performed in producing titanium alloy members, including forging and heat treatment, tend to introduce oxygen into the alloy. However, this introduction of oxygen is usually limited to a thin region near the surface of the member. This layer can be machined or removed in some other manner if desired.

  Powder metallurgy manufacturing tends to provide a number of advantages over alternative routes. For example, near net shape members can be produced with very little waste. Also, relatively complex shapes that can be prohibitively expensive to machine can be made relatively easily.

  However, high quality titanium alloy powders tend to be relatively expensive. The cost of the powder tends to be a very large part of the total manufacturing cost.

  Cheaper alloy powders are available. They are not suitable for the production of structural parts due to their relatively high oxygen content.

  In addition, when titanium alloy powders are used, for example, in the production of powders, in the processing of powders, and in the formation of solid materials by hot compaction or partial melting of the powders, oxygen due to the relatively large surface area of the titanium alloy powders. Absorption tends to be a particularly big problem.

  The titanium alloy powder may be chemically treated at high temperatures to reduce the oxygen content. Similar methods have been used for titanium alloy members to remove oxygen contamination on or just below the surfaces of those members.

  However, for titanium powders such high temperature chemical treatments tend not to be applicable to fine powder sizes (eg those used in metal injection molding) due to the strong tendency of the powder particles to sinter.

  US Patent Application Publication No. 2005/139483 discloses a method for purifying metal salts. The method comprises contacting a metal salt formed by melting an alkali metal salt, an alkaline earth metal salt, or a mixture thereof with one or more of titanium, a titanium alloy, zirconium, and a zirconium alloy. including. The metal salt is melted in a container made of titanium or a titanium alloy, or a container lined with titanium or a titanium alloy.

  GB 797934 discloses a method for removing oxygen from oxygen-containing titanium metal. The method includes bringing together alkali metal fluoritanates.

  British Patent No. 718211 discloses treating titanium sheets in a calcium bath at a temperature of 1000 ° C.

  GB 698753 discloses a process for the purification of oxygen-containing titanium comprising treating titanium with calcium or calcium hydroxide in a fluid medium at a temperature of 900 ° C. or higher.

  GB 1450039 discloses a method for removing oxygen from a metal powder consolidated into a shape. Carbon contained in the metal powder is used to remove oxygen. However, this step must be performed while the object has open porosity so that carbon oxide (gas) can be removed from the object. This deoxygenation process tends not to be useful for full density or near full density objects. Furthermore, the disclosed method tends to be ineffective for titanium or titanium alloy objects.

  In a first aspect, the present invention provides a method of producing an object, wherein the object is made of a metal or alloy, the object has a desired shape, and the object is a non-porous object The method provides some metal or alloy (the provided metal or alloy has a first average solute level) and uses the provided metal or alloy to form a net shape or near net shape. A manufacturing process is performed to produce an intermediate object (where the intermediate object has a desired shape, the intermediate object is a non-porous object, and the intermediate object has a second average solute level. The second average solute level is greater than or equal to the first average solute level) and performing a solute level changing step on the intermediate object to at least a bulk of the intermediate object (ie, a majority of the body of the intermediate object) ) Solute level, the third average solute level Change to provide between the object, by which includes providing an object, wherein the third average solute level is different from the second average solute level.

  The third average solute level may be lower than the first average solute level.

  The solute level reduction process may be performed such that the intermediate object substantially retains its shape and solid density.

  In a further aspect, the present invention provides an object produced by performing the method according to the first aspect.

  In a further aspect, the present invention provides a method of treating an object, wherein the object is made of a metal or alloy, the object has a first average solute level, the method comprising: Performing a solute level changing step to add or remove solute from the surface of the object, thereby producing an object having a second average solute level and an increased gradient of solute level; Performing a homogenization process on the object having the average solute level to reduce a gradient of the solute level in the object having the second average solute level.

  In a further aspect, the present invention provides a method of producing an object having a second average solute level, wherein the second average solute level is equal to or desired range. The object is made of a metal or alloy, and the method forms an object from a raw material having a first average solute level to produce the formed object; A solute level changing step is performed on the surface of the formed object to add or remove solute, thereby changing the average solute level of the formed object to the second average solute level; Performing a homogenization step on the object having an average solute level of diffusing the solute in the object having the second average solute level.

  The solute level changing step may be performed to reduce the average solute level in the object.

  The solute level changing step may include performing a solute level decreasing step and performing a solute level increasing step, wherein the solute level decreasing step and the solute level increasing step are performed on the object, Performed before the homogenization step is performed, the solute level reduction step is performed to remove the solute from the surface of the object, thereby reducing the average solute level of the object, and the solute increase step is performed on the object. The amount of solute added to the surface, thereby increasing the average solute level of the object, and the average solute level being reduced during the solute level reduction process is the average solute level of the solute increase process. It is different from the amount increased in between.

  The metal or alloy may include one or more of the following metals. Titanium, tantalum, vanadium, zirconium, molybdenum, niobium.

  The metal or alloy may be a titanium alloy.

  The alloy may be Ti-6Al-4V.

  The solute may be one of the following: Oxygen, carbon, hydrogen, or nitrogen.

  The solute may be oxygen.

  The second average solute level may be between 1000 parts per million and 2300 parts per million.

  The second average solute level may be between 1300 parts per million and 1800 parts per million.

  The second average solute level may be between 1700 and 1800 parts per million.

  The second average solute level may be less than 2000 weight parts per million.

  The second average solute level may be less than 1300 weight parts per million.

  The first average solute level may be between 2300 parts per million and 10,000 parts per million.

  The first average solute level may be between 5000 weight parts per million and 10,000 weight parts per million.

  The first average solute level may be higher than 10,000 weight parts per million.

  The step of performing the homogenization process may be performed such that the solute level within the object is substantially uniform throughout the object having the second average solute level.

  The object may be made from an alloy in powder form using a metal injection molding process.

  Performing the solute level changing process may include exposing at least a portion of the object to a fluid, where the fluid includes a chemical reactant, which reacts to a different level of solute than the alloy. Have sex.

  The chemical reactant may be an alkaline earth metal (eg, calcium).

  The fluid may further include a flux material, which facilitates removal of reaction products between the chemical reactant and the alloy from the surface of the object.

  The flux material may be calcium chloride.

  The fluid may be a vapor.

  Performing the solute level changing process may include heating the object to between 1000 ° C and 1200 ° C.

  Performing the homogenization process may include heating the object to between 1000 ° C and 1300 ° C.

  Heating the object to between 1000 ° C. and 1300 ° C. may be performed for between 0.5 and 100 hours.

  In a further aspect, the present invention provides an apparatus for processing an object, wherein the object is made of a metal or alloy, the object has a first average solute level, the apparatus being Performing a solute level changing step to add or remove solute from the surface of the object, thereby producing an object having a second average solute level and an increased gradient of solute level; Means for performing a homogenization step on an object having an average solute level of 2 to reduce a gradient of solute levels in the object having a second average solute level.

  In a further aspect, the present invention provides an apparatus for producing an object having a second average solute level, wherein the second average solute level is equal to or desired range. The object is made of a metal or alloy, and the apparatus forms a body from a raw material having a first average solute level to produce the formed body; Means for performing a solute level changing step on the formed object to add or remove solute from the surface of the formed object, thereby changing the average solute level of the object to a second average solute level; Means for performing a homogenization step on the object having the second average solute level to diffuse the solute in the object having the second average solute level.

  In a further aspect, the present invention provides a method for altering the concentration of a solute in an object, wherein the object is made of a metal or alloy, the method comprising exposing at least a portion of the object to steam. Where the vapor includes chemical reactants (the chemical reactants have a different level of reactivity with the solute than the metal or alloy) and a flux material, wherein the flux material is a chemical in the vapor This is to facilitate the removal of the reaction product between the reactant and the alloy from the surface of the object.

  The reaction product between the chemical reactant in the vapor and the alloy may be soluble in the flux material.

  The metal or alloy may include one or more of the following metals. Titanium, tantalum, vanadium, zirconium, molybdenum, niobium.

  The metal or alloy may be a titanium alloy.

  The metal or alloy may be Ti-6Al-4V.

  The solute may be one of the following: Oxygen, carbon, hydrogen, or nitrogen.

  The solute may be oxygen.

  The concentration of the solute in the object may be varied to be in the range of 1000 parts per million and 2300 parts per million.

  The concentration of the solute in the object may be varied because it is in the range of 5000 parts per million and 10,000 parts per million.

  The chemical reactant may have a higher level of reactivity to the solute than the alloy.

  The chemical reactant may be calcium.

  The chemical reactant may have a lower level of reactivity to the solute than the alloy.

  The chemical reactant may be calcium oxide.

  The flux material may be calcium chloride.

  The method may include heating the object to between 1000 ° C and 1200 ° C.

  The object may be made from an alloy in powder form using a metal injection molding process.

  The method may further include performing a homogenization step on the object to reduce a solute level gradient in at least a portion of the object.

  In a further aspect, the present invention provides an apparatus for altering the concentration of a solute in an object, wherein the object is made of a metal or alloy such that at least a portion of the object is exposed to steam. And includes means for generating steam, wherein the steam includes a chemical reactant (the chemical reactant has a different level of reactivity with the solute than the metal or alloy), and a flux material; The flux material is for facilitating the removal of reaction products between chemical reactants in the vapor and the alloy from the surface of the object.

  In a further aspect, the present invention provides a method of producing an object having a second average solute level, wherein the second average solute level is equal to or desired for a desired solute level. The object is made of a metal or alloy and the method forms an object from a raw material having a first average solute level to produce the formed object (formed object Have an initial porosity and the formed object has an open porosity), perform a solute level changing step on the formed object to add or remove solutes from the formed object This changes the average solute level of the object to the second average solute level and performs a solidification process on the object having the second average solute level to reduce the porosity of the object to the desired level. Equal to or within the desired range Including reducing the so that.

  The solute level changing step may be performed to reduce the average solute level in the formed object.

  The solidification step may include sintering the object having the second average solute level.

  The formed object may have a solid density in the range of 60% to 92%.

  The formed object may have a solid density in the range of 70% to 80%.

  After performing the solidification process, the object may have a solid density in the range of 92% to 100%.

  The method may further include performing a homogenization step on the object having the second average solute level to diffuse the solute in the object having the second average solute level.

  The step of performing the homogenization process may be performed such that the solute level throughout the object having the second average solute level is substantially uniform.

  The solute level changing process may include performing a solute level decreasing process and performing a solute level increasing process, wherein the solute level decreasing process and the solute level increasing process are performed on the formed object. On the other hand, the solute level reduction step is performed before the solidification step is performed, and the solute level reduction step is performed to remove the solute from the surface of the formed object, thereby reducing the average solute level of the formed object. The solute increase step is performed to add solute to the surface of the formed object, thereby increasing the average solute level of the formed object, and the average solute level is reduced during the solute level decrease step The amount that is made is different from the amount that the average solute level is increased during the solute augmentation process.

  The alloy may include one or more of the following metals. Titanium, tantalum, vanadium, zirconium, molybdenum, niobium.

  The alloy may be a titanium alloy.

  The alloy may be Ti-6Al-4V.

  The solute may be one of the following: Oxygen, carbon, hydrogen, or nitrogen.

  The solute may be oxygen.

  The second average solute level may be between 1000 parts per million and 2300 parts per million.

  The second average solute level may be between 1300 parts per million and 1800 parts per million.

  The second average solute level may be between 1700 and 1800 parts per million.

  The second average solute level may be less than 2000 weight parts per million.

  The second average solute level may be less than 1300 weight parts per million.

  The first average solute level may be between 2300 parts per million and 10,000 parts per million.

  The first average solute level may be between 5000 weight parts per million and 10,000 weight parts per million.

  The first average solute level may be higher than 10,000 weight parts per million.

  Forming the object may include forming the object using an alloy in powder form and a metal injection molding process.

  Performing the solute level changing process may include exposing at least a portion of the formed object to a fluid, where the fluid includes a chemical reactant, which is different from a metal or alloy. Reactive to level solutes.

  The chemical reactant may be calcium.

  The fluid may further include a flux material, which facilitates removal of reaction products between the chemical reactant and the metal or alloy from the surface of the formed object.

  The flux material may be calcium chloride.

  The fluid may be a vapor.

  Performing the solute level changing process may include heating the formed object to between 1000 ° C and 1200 ° C.

  In a further aspect, the present invention provides an apparatus for producing an object having a second average solute level, wherein the second average solute level is equal to or desired for a desired solute level. The object is made of a metal or alloy and the device forms a body from a raw material having a first average solute level to produce the formed body; The formed object has an initial porosity, the formed object has an open porosity), and a solute level changing process is performed on the formed object to remove the formed object from the surface of the formed object. Means for adding or removing a solute, thereby changing the average solute level of the object to a second average solute level, and performing a solidification step on the object having the second average solute level, So that the sex is equal to the desired level Includes a means for reducing such a range as desired.

  In a further aspect, the present invention provides a method, the method comprising performing a method step according to the first aspect of the present invention, wherein the solute level changing step is It is executed according to either.

  In a further aspect, the present invention provides a method, the method comprising performing a method step according to the first aspect of the invention, or a previous aspect of the invention, the method comprising: Forming an object to produce a formed object from a raw material having an average solute level, the formed object has an initial porosity, the formed object has an open porosity, In accordance with either, the method further includes performing a solute level changing step and a solidifying step.

2 is a process flow diagram illustrating certain steps of an example process for producing a titanium alloy mechanical component in which an embodiment of an oxygen reduction process is performed. 2 is a process flow diagram illustrating certain steps of the process of forming a member that are performed during the process shown in FIG. FIG. 3 is a schematic view (not a constant scale factor) of a member formed using the process shown in FIG. 2. It is the 1st cross section of the member after using the process shown in FIG. 2, and the schematic of the 2nd cross section (it is not a fixed scale factor). 2 is a process flow diagram illustrating certain steps of an embodiment of an oxygen reduction process performed on a member during the process shown in FIG. FIG. 6 is a process flow diagram illustrating certain steps of a deoxygenation process performed on a member during the process illustrated in FIG. 5. FIG. 7 is a schematic view (not to scale) of a deoxygenation chamber used in the process of FIG. It is the schematic (it is not a fixed scale factor) of the 1st cross section after a deoxidation process was performed with respect to the member, and a 2nd cross section. FIG. 6 is a process flow diagram illustrating certain steps of a reoxidation process performed on a member during the process shown in FIG. 5. It is the schematic (it is not a fixed scale factor) of the 1st cross section after the reoxidation process was performed with respect to the member, and a 2nd cross section. FIG. 6 is a process flow diagram illustrating certain steps of an oxygen homogenization process performed on a member during the process shown in FIG. 5. It is the 1st cross section after the oxygen equalization process was performed with respect to the member, and the schematic of a 2nd cross section (it is not a fixed scale factor). 2 is a process flow diagram illustrating certain steps of a process for producing a titanium alloy member, in which an oxygen reduction process is performed before the member is fully solidified. FIG. 14 is a process flow diagram illustrating certain steps of a process of partially solidifying a member as performed during the process of FIG.

  FIG. 1 is a process flow diagram illustrating certain steps of an example process for producing a titanium alloy mechanical member (hereinafter referred to as a “member”) in which one embodiment of an oxygen reduction process is performed. .

  In step s2, a member is formed.

  One exemplary process for forming the member is described in more detail below with reference to FIG.

  In step s4, an oxygen reduction process is performed on the member.

  In this example, the oxygen reduction process is performed to reduce the level of oxygen in the member (ie, oxygen concentration).

  One embodiment of the oxygen reduction process will be described in more detail below with reference to FIG.

  Accordingly, a process for producing a titanium alloy member is provided.

  FIG. 2 is a process flow diagram illustrating certain steps of the process of forming a member, performed in step s2 of the process of producing the member (described above with reference to FIG. 1).

  In step s6, a metal injection molding process is performed to produce a so-called “green part”.

  In this example, a conventional metal injection molding process is performed. A relatively finely powdered alloy is mixed with the binder material to produce a so-called “feedstock”. This feedstock is molded using an injection molding process to produce green parts.

  In this example, the alloy is titanium with 6% aluminum and 4% vanadium (also known as Ti-6Al-4V or 6-4, 6/4, ASTM B348 grade 5). In this example, the alloy also contains a certain amount of oxygen in the solid solution. In this example, the alloy contains greater than 0.18% oxygen, ie greater than 1800 parts per million (ppm) oxygen.

  In step s7, after the green part is cooled and released, a part of the binder material is removed from the green part to produce a so-called “brown part”.

  In this example, a conventional process is used to remove the binder material from the green part, for example by using solvent, thermal evaporation and / or catalytic processes.

  In this example, the brown part produced by metal injection molding and the binder removal process has a solid density of about 60%. In other words, the brown part is relatively porous.

  Also in this example, the brown part has a substantially uniform porosity throughout the part. The surface of the brown part and the internal structure have substantially equal porosity.

  In step s8, a sintering process is performed on the brown part to form a member. In this example, a conventional sintering process is used.

  In this example, the brown part is sintered at a temperature in the range of 1000 ° C to 1300 ° C. This sintering process tends to agglomerate the metal particles in the brown part, thereby increasing the solid density of the part.

  In this example, the member formed by sintering the brown part has a solid density in the range of 92% to 100%.

  Also in this example, at this stage (ie, after the sintering process), the member has an oxygen concentration greater than 1800 ppm. Furthermore, this oxygen concentration is substantially uniform throughout the member.

  Thus, a step of forming a member is provided.

  FIG. 3 is a schematic view (not to scale) of member 2 formed using the forming process described in more detail above with reference to FIG.

  In this example, member 2 is a single solid piece of titanium alloy.

  The term “solid” is used herein to mean a material having a density by volume (ie, solid density) between 92% and 100%. .

  For convenience and for ease of understanding, the shape of the member 2 may be two cylinders (hereinafter “first cylinder 4” and “second cylinder” configured as described in more detail below). May be described with reference to a cylinder 6). However, it should be understood that in this embodiment, member 2 is a single solid piece.

  In this example, the first cylinder 4 has a diameter of about 20 mm and a length of about 100 mm.

  In this example, the second cylinder 6 has a diameter of about 9 mm and a length of about 100 mm.

  In this example, the first cylinder 4 and the second cylinder 6 are positioned such that one end of the first cylinder 4 is in contact with one end of the second cylinder 6. Furthermore, in this example, the cylinders 4, 6 are positioned so that they are coaxial, ie the cylinders 4, 6 share a common axis. Therefore, the length of the member 2 is 200 mm.

  A cross section of the first cylinder 4 (hereinafter referred to as “first cross section”) is indicated by a dotted line and a reference number 8 in FIG.

  In addition, a cross section of the second cylinder 6 (hereinafter referred to as “second cross section”) is indicated by a dotted line and a reference number 10 in FIG. 3.

  FIG. 4 is a schematic view (not to scale) of first cross section 8 and second cross section 10 after formation of member 2 (ie, after performing step s2 of FIG. 1). .

  In FIG. 4, the regions in cross-sections 8, 10 that have a relatively high oxygen concentration (ie, a relatively high oxygen level) are shown as being filled with black (ie, filled with no gaps). ). The term “relatively high concentration of oxygen” is used herein to mean a region having an oxygen concentration higher than 1800 ppm. In this example, after formation of member 2 (ie, after step s2), member 2 has an oxygen concentration greater than 1800 ppm. Furthermore, this oxygen concentration is substantially uniform throughout the member. In other words, the member 2 includes a substantially uniform and relatively high oxygen level. Accordingly, in FIG. 4, the first and second cross sections 8 and 10 are filled with black.

  For completeness, such reasons are not shown in FIG. 4, but regions within cross-sections 8, 10 having moderate oxygen concentrations (ie, medium oxygen levels) are indicated by cross-hatching. The term “medium oxygen level” is used herein to mean a region having an oxygen concentration in the range of 1300 ppm to 1800 ppm. Also, areas in cross sections 8, 10 that have a relatively low oxygen concentration (ie, a relatively low oxygen level) are not filled (ie, shown as blank areas). The term “relatively low concentration of oxygen” is used herein to mean a region having an oxygen concentration lower than 1300 ppm.

  Referring again to FIG. 1, after the formation of the member 2 (ie, step s2), an oxygen reduction step (step s4) is performed on the member 2.

  FIG. 5 is a process flow diagram illustrating certain steps of an embodiment of the oxygen reduction process performed on the member formed in step s2.

  In step s10, a deoxidation process is performed on the member 2.

  This deoxygenation step is performed to remove oxygen from the member 2.

  The deoxygenation process used in this embodiment will be described in more detail below with reference to FIGS.

  In step s12, the reoxidation process is performed on the member 2.

  This reoxidation step is performed to add oxygen back into the member 2.

  The reoxygenation process used in this embodiment will be described in more detail below with reference to FIGS. 9 and 10.

  In step s14, a step of uniforming the oxygen concentration level throughout the member 2 is performed. This is a step of increasing the uniformity of the oxygen concentration level throughout the member 2. The desired degree of oxygen level uniformity within the member 2 may depend, for example, on the service requirements of the member 2. This process is hereinafter referred to as “oxygen homogenization process”.

  The oxygen homogenization process used in this embodiment will be described in more detail later with reference to FIGS.

  Thus, an oxygen reduction process is provided.

  Referring again to step s10 of the oxygen reduction process, FIG. 6 is a process flow diagram illustrating certain steps of the deoxygenation process performed on member 2 in step s10.

  In step s16, the member 2 is placed in a chamber in which the deoxygenation of the member 2 occurs. For convenience, this chamber is hereinafter referred to as a “deoxygenation chamber”.

  The deoxygenation chamber and the positioning of the member 2 within the deoxygenation chamber will be described in more detail below with reference to FIG.

  In step s17, the material used to remove oxygen from member 2 is placed in the deoxygenation chamber.

  This material and its placement within the deoxygenation chamber will be described in more detail below with reference to FIG.

  In step s18, the deoxygenation chamber is sealed, as will be described in more detail below, so that the deoxygenation chamber completely contains both the member 2 and the material.

  Here, the structure of the deoxygenation chamber and the member 2 and the substance in the deoxygenation chamber will be described. The remaining steps of the process of FIG. 6 (steps s19 to s22) will be described in more detail after this information.

  FIG. 7 is a schematic view (not to scale) of the deoxygenation chamber 12.

  In this embodiment, the deoxygenation chamber 12 includes a container 13 and a stand 14. The stand 14 is positioned in the container 13 as a whole.

  As described above, the entire member 2 is disposed in the deoxygenation chamber 12. In this embodiment, the member 2 is placed on the stand 14 so that the member 2 is generally inside the wall of the container 13.

  Further, the substance 16 is disposed at the bottom of the container 13. The member 2 is held above the level of the substance 16 in the container 13 (by the stand 14).

  In this embodiment, the material 16 includes a chemical oxygen scavenger and a flux. In this embodiment, the chemical oxygen scavenger and flux are placed in a container in solid form (eg, in the form of powder or pellets).

  In this embodiment, the chemical oxygen scavenger is a chemical element that has a greater affinity for oxygen than titanium (ie, member 2).

  The term “greater affinity” is used herein to mean a greater level of reactivity. Thus, a chemical oxygen scavenger is a chemical element that has a higher level of reactivity with oxygen than does titanium. Similarly, a “lesser” affinity means a lower level of activity. Equivalently, the term “greater affinity” is used herein to refer to a higher level of stability (ie, more negative free energy of more in the reaction product). formation)). Similarly, “smaller” affinity is used to mean a lower level of stability (ie, less negative free energy of formation) in the reaction product.

  Also, in this embodiment, the chemical oxygen scavenger is not reacted or alloyed with titanium (ie, member 2) or diffuses into the alloy during the oxygen scavenging process. In this embodiment, the chemical oxygen scavenger is calcium.

  In this embodiment, the flux is used to advantageously assist the transfer of chemical oxygen scavenger to the surface of member 2. Furthermore, the flux tends to advantageously remove reaction products from the surface of the member 2 during the deoxygenation process. In this embodiment, the flux is a calcium chloride salt.

  In this embodiment, the ratio of chemical oxygen scavenger (calcium) within the material (ie chemical oxygen scavenger and flux) is in the range of 1 mol% to 20 mol%. This tends to result in the deoxygenation process being particularly effective. Preferably, the proportion of chemical oxygen scavenger in the flux is greater than 15 mol%.

  In this embodiment, the container 13 of the deoxygenation chamber 12 is sealed with the member 2 and the substance 16 inside. When the deoxygenation chamber 12 is heated (as described in more detail below with reference to step s19 of FIG. 6), the material 16 melts and a portion of the material 16 is vaporized. The vaporized material (hereinafter referred to as “vapor”) is depicted as a wavy line in FIG. The steam 18 contacts the member 2.

  Referring now again to FIG. 6, in step s19, the deoxygenation chamber 12 is heated to melt the material 16 and then vaporize it (and thereby produce a vapor 18).

  In this embodiment, the deoxygenation chamber 12 is heated to between 772 ° C. (flux melting temperature) and about 1660 ° C. (titanium alloy (ie, member 2) melting temperature). Preferably, the deoxygenation chamber 12 is heated to between 1000 ° C and 1200 ° C. This temperature tends to favor moderately rapid deoxygenation, while avoiding reaction with deoxygenation chamber equipment (eg, stand 14) and other problems associated with very high temperatures. Or reduced.

  Heating of the deoxygenation chamber 12 such that the substance 16 vaporizes results in the vapor 18 contacting the member 2. Since the calcium in the substance 16 (and hence the vapor 18) has a greater affinity for oxygen than the titanium of the member 2, oxygen atoms tend to be removed from the surface of the member 2 by the vapor 18. Therefore, the oxygen concentration on the surface of the member 2 tends to be lower than the oxygen concentration near the center of the member 2. This concentration gradient tends to generate a net flow of oxygen from the inside of the member 2 (due to solid diffusion) to the surface of the member 2.

  As calcium in the vapor 18 reacts with oxygen in the member 2, calcium oxide is formed. This calcium oxide tends to deposit on the surface of the member 2. The flux in the vapor 18 (i.e. vaporized calcium chloride) advantageously tends to dissolve, move away or otherwise remove calcium oxide from the surface of the member 2. For example, during deoxygenation, the member may become covered with a liquid film of calcium chloride / calcium solution, which is the liquid flux in embodiments where the member is immersed in the liquid flux and reactants. There is a tendency to perform similar functions (eg, the function of dissolving calcium oxide reaction products and supplying fresh calcium to the surface). Calcium contacts the member in the form of steam and may be dissolved in the flux. However, since calcium oxide is not relatively volatile, it tends to remain in the liquid film. This liquid film may flow down from the member and return to the lower liquid reservoir. It has been found in experiments that the deoxygenation rate is greater in calcium chloride / calcium vapor than in calcium vapor alone.

  In other words, the flux in the vapor 18 (i.e. vaporized calcium chloride), which tends to dissolve, divert away or otherwise remove calcium oxide from the surface of the member 2, is preferably There is a tendency to facilitate access to the member 2 by the vapor 18 and to maintain the concentration of reactants and reaction products, which results in the reaction being continued at the desired rate. Accordingly, the use of the flux material tends to favorably facilitate the removal of oxygen from the member 2.

  In this embodiment, the deoxygenation chamber 12 is heated for a first predetermined period. In other words, the temperature of the deoxygenation chamber 12 is maintained, for example, between 1000 ° C. and 1200 ° C. over a first predetermined period. In this embodiment, the first predetermined period is between 0.5 and 100 hours. For example, the average oxygen level in a 9.3 mm diameter Ti-6 / 4 bar was reduced from 2000 ppm to 600 ppm using a 20 mol% solution of calcium in calcium chloride at 1000 ° C. for 72 hours. Also good.

  In this embodiment, the first predetermined time period is predetermined to achieve the desired oxygen level in the member 2. Advantageously, this first predetermined period and / or the amount of substance 16 used and / or the concentration of chemical oxygen scavenger in substance 16 achieve the desired oxygen level in member 2. Tend to be able to be determined / changed for. These may be determined depending on certain parameters (for example, the initial oxygen content in the member 2, the thickness of the member 2, and the temperature at which the deoxygenation chamber 12 is heated).

  In this embodiment, the first predetermined period and / or the amount of chemical oxygen scavenger is such that after treatment of member 2 over this period, member 2 has an average oxygen level of less than 1300 ppm by weight (ie, this Such as having a low oxygen level).

  In this embodiment, during step s19 (ie, during heating of the deoxygenation chamber 12), the deoxygenation chamber 12 is evacuated or backfilled using a partial pressure of argon. The partial pressure of argon tends to avoid unwanted internal pressurization of the container at the processing temperature or, in the case of evacuation, external pressurization of the chamber by atmospheric pressure. In this embodiment, the reactant and argon partial pressures are such that the total internal pressure of the container 13 is about 1 atmosphere at the processing temperature.

  In this embodiment, the container 13 and stand 14 are made of a material that is not alloyed with either titanium or deoxygenated chemicals at the processing temperature and does not react adversely. In this embodiment, titanium is used for the container 13 and the stand 14. However, in other embodiments, refractory metals such as molybdenum and / or high temperature steel may be used.

  In step s20, after the first predetermined period has expired, the deoxygenation chamber 12 is left for cooling.

  In step s21, the container 13 of the deoxidation chamber 12 is opened, and the member 2 is taken out.

  In step s22, the member 2 is cleaned. In this embodiment, water is used to remove the flux from the member 2, and dilute acid (eg, dilute hydrochloric acid) is used to remove the calcium oxide residue.

  Thus, a deoxygenation step is provided.

  FIG. 8 is a schematic of the first cross section 8 and the second cross section 10 after the deoxygenation step is performed as described above with reference to FIG. 6 (that is, after step s10 of FIG. 5 is performed). It is a figure (not a fixed scale ratio).

  As in FIG. 4, in FIG. 8, the regions in cross-sections 8, 10 that have a relatively high oxygen concentration (ie, an oxygen concentration higher than 1800 ppm) are filled with black and have a moderate oxygen concentration ( That is, areas having a range of 1300 ppm to 1800 ppm are indicated by cross-hatching, and areas having a relatively low oxygen concentration (ie, an oxygen concentration lower than 1300 ppm) are not filled.

  In this embodiment, after the deoxygenation step, the member 2 is referred to as a relatively small central inner portion (hereinafter “inner core”) having an oxygen concentration higher than 1800 ppm in its first cross section 8, in FIG. (Denoted by reference numeral 20).

  The member 2 has an oxygen concentration between 1300 ppm and 1800 ppm in its first cross section 8, and is a region surrounding the inner core 20 (hereinafter referred to as “outer core”, and is indicated by reference numeral 22 in FIG. 8. Have).

  The member 2 has an oxygen concentration between 1300 ppm and 1800 ppm in its first cross section 8 and is adjacent to the surface of the member (hereinafter referred to as “edge”, and is indicated by reference numeral 23 in FIG. 8. Have).

  In FIG. 8, for clarity and ease of understanding, the three regions of the first cross-section 8 (ie, the inner core 20, the outer core 22, and the edge 23) have clear discrete boundaries. Shown as having. In practice, however, in this embodiment, after the deoxygenation step, the oxygen level across the first cross section 8 of the member 2 is reduced from a relatively low level at the edge / surface of the member 2 to a relatively high level at the member center. Change continuously.

  In this embodiment, after the deoxygenation step, the member 2 has an oxygen concentration of less than 1300 ppm through its second cross section 10. Further, in this embodiment, the oxygen concentration is substantially uniform throughout the portion of the member 2 corresponding to the second cross section 10. Therefore, in FIG. 8, the second cross section 10 is not filled.

  In this embodiment, after the deoxygenation step, member 2 has an average oxygen level (ie, a low oxygen level) of less than 1300 ppm by weight. In other words, after all the oxygen in the member has spread substantially uniformly throughout the member 2 after the deoxygenation step, the oxygen level of the member 2 is low (ie, less than 1300 ppm).

  Thus, in this embodiment, during the deoxygenation process, oxygen is removed from the surface of the member 2 substantially uniformly, so that regions of the member 2 having different thicknesses (ie, the first cylinder 4 and The second cylinder 6) tends to have a different oxygen concentration after the deoxygenation step. In particular, the relatively thin section (second cylinder 6) tends to have a lower oxygen level than the relatively thick section (first cylinder 4).

  Thus, in this embodiment, the deoxygenation step is performed on member 2 to reduce the average oxygen level in member 2. The deoxygenation component is also performed to increase the gradient of oxygen level across the member 2. This is in contrast to traditional deoxygenation processes (such as those performed to reduce alpha cases in parts) that tend to be performed to reduce the gradient of oxygen levels in the object being processed. Is.

  In this embodiment, optional additional steps are provided in which reoxidation of member 2 is performed (ie, step s12 of FIG. 5 is performed). This optional reoxidation process tends to increase the oxygen level of the thinner part of the member proportionally more than the oxygen level of the thicker part can be increased. This is done in this embodiment to increase the average oxygen level of the thinner section of member 2 to be substantially equal to the average oxygen level of the thicker section.

  Referring now again to FIG. 5, the reoxidation process performed in this embodiment in step s12 will now be described.

  FIG. 9 is a process flow diagram illustrating certain steps of the reoxidation process performed on member 2 in step s12.

  In step s24, member 2 is placed in a chamber in which reoxidation of member 2 occurs. For convenience, this chamber will hereinafter be referred to as the “reoxidation chamber”.

  In this embodiment, the reoxidation chamber is substantially the same chamber as deoxygenation chamber 12 described above with reference to FIG. 7 (ie, the reoxidation chamber is configured in the same manner as the components of deoxygenation chamber 12). Metal container and stand).

  In this embodiment, member 2 is placed on the stand of the reoxidation chamber such that member 2 is generally inside the wall of the reoxidation chamber container.

  In step s25, additional material used to introduce oxygen into member 2 is placed in the reoxidation chamber.

  In this embodiment, the additional material is placed at the bottom of the container of the reoxidation chamber so that the member 2 is immersed under the additional material.

  In this embodiment, the additional materials include oxidizing chemicals and flux. In this embodiment, the oxidizing chemical and flux are placed in a container in solid form (eg, in the form of powder or pellets).

  In this embodiment, the oxidizing chemical is calcium oxide.

  In this embodiment, the flux used in the reoxidation process is the same as the flux used in the deoxygenation process (ie, calcium chloride). The flux advantageously assists in transporting the oxidizing chemical to the surface of the member 2.

  In this embodiment, the ratio of oxidizing chemicals in the further substance is in the range from 1 mol% to 20 mol%, preferably in the range from 15 to 20 mol%. This tends to result in the reoxidation process being particularly effective.

  In this embodiment, reoxidation of the member uses the same chemical reaction as the deoxygenation step. In this embodiment, preferably a 15-20 mol% solution of calcium oxide in calcium chloride is used. By increasing the concentration of calcium oxide and decreasing the concentration of calcium, the equilibrium point of the reaction changes (according to Le Chatelier's principle) and oxidation occurs rather than deoxygenation.

  In other embodiments, the oxidation of the member 2 may be performed in a different manner, for example using gaseous oxygen. However, this tends to be difficult to control. In other embodiments, different oxidizing chemicals, for example, chemical elements that have a lower affinity for oxygen than titanium (ie, member 2) are used to reoxidize member 2. In other embodiments, water vapor is used to reoxidize member 2. In such cases, titanium tends to react with water vapor, and both oxygen and hydrogen diffuse into the metal. The hydrogen may be removed later by, for example, vacuum degassing.

  In step s26, the reoxidation chamber is sealed so that the container completely contains both member 2 and further material.

  In step s19, the reoxidation chamber is heated to melt further material, thereby producing further material that has been liquefied.

  In this embodiment, the reoxidation chamber is heated to between 772 ° C. (flux melting temperature) and about 1660 ° C. (titanium alloy, ie, member 2 melting temperature). Preferably, the reoxidation chamber is heated to between 1000 ° C and 1200 ° C. This temperature advantageously avoids oxidation proceeding at a suitable rate, as well as reaction with reoxidation chamber equipment (eg, reoxidation chamber stand) and other problems associated with very high temperatures. Or tend to be alleviated.

  Heating the reoxidation chamber causes additional material to melt and contact the member 2. Oxygen atoms tend to be removed from further material (thus forming calcium) and introduced into the surface of the member 2. Therefore, the oxygen concentration on the surface of the member 2 tends to be increased by the reoxidation process. There is a tendency that a net flow of oxygen from the surface of the member 2 toward the inside of the member 2 is generated.

  As calcium oxide in the further substance reacts with the member 2, calcium is formed. This calcium tends to deposit on the surface of the member 2. The flux in the further substance (i.e. vaporized calcium chloride) advantageously tends to dissolve or remove calcium from the surface of the member 2. This tends to promote access to member 2 by calcium oxide and tends to maintain the concentration of reactants and reaction products, which results in the reaction being continued at the desired rate. Therefore, the use of the flux material tends to favorably facilitate the introduction of oxygen into the member 2. In this embodiment, the reoxidation chamber is heated for a second predetermined period. In other words, the temperature of the reoxidation chamber is maintained, for example, between 1000 ° C. and 1200 ° C. over a second predetermined period. In this embodiment, the second predetermined period is between 0.5 hours and 100 hours. For example, the oxygen level of a 9.3 mm diameter Ti-6 / 4 bar was increased from 2000 ppm to 3500 ppm by immersion in a solution of 20 mol% calcium oxide in calcium chloride at 1000 ° C. for 72 hours. Also good. In this embodiment, the second predetermined time period is predetermined to achieve a further desired oxygen level in the member 2. Advantageously, this second predetermined period and / or the amount of further substance used and / or the concentration of the oxidizing chemical in the further substance is determined by the further desired oxygen in the member 2. There is a tendency to be able to decide / change to achieve the level. These are specific parameters (eg, the initial oxygen content in member 2 (ie, the oxygen content in member 2 after the deoxygenation step), the thickness of member 2 and the reoxidation chamber being heated. Depending on the temperature).

  In this embodiment, the second predetermined period and / or the amount of oxidizing chemical is such that after treatment of member 2 over this period, member 2 has an average oxygen between 1300 ppm and 1800 ppm by weight. Such as having a level (ie, medium oxygen level in the terminology of this specification).

  In this embodiment, during step s27 (ie, during heating of the reoxidation chamber), the reoxidation chamber is evacuated or backfilled using a partial pressure of argon. The partial pressure of argon tends to avoid undesired internal pressurization of the reoxidation chamber container at the process temperature or, in the case of evacuation, external pressurization of the chamber by atmospheric pressure. In this embodiment, the reactant and argon partial pressures are such that the total internal pressure of the reoxidation chamber container is about 1 atmosphere at the process temperature.

  In step s28, after the second predetermined period expires, the reoxidation chamber is left for cooling.

  In step s29, the container of the reoxidation chamber is opened and the member 2 is removed.

  In step s22, the member 2 is cleaned. In this embodiment, water is used to remove the flux from the member 2, and dilute acid (eg, dilute hydrochloric acid) is used to remove calcium and calcium oxide residues.

  Thus, a reoxidation process is provided.

  FIG. 10 is a schematic of the first cross section 8 and the second cross section 10 after the re-oxidation step is performed as described above with reference to FIG. 9 (ie, after performing step s12 of FIG. 5). It is a figure (not a fixed scale ratio).

  Similar to that in FIGS. 4 and 8, in FIG. 10, the areas within cross-sections 8 and 10 that have a relatively high oxygen concentration (ie, oxygen concentration higher than 1800 ppm) are filled with black and are medium in size. Regions having an oxygen concentration (ie, in the range from 1300 ppm to 1800 ppm) are indicated by cross-hatching, and regions having a relatively low oxygen concentration (ie, an oxygen concentration below 1300 ppm) are not filled.

  In this embodiment, after the reoxidation step, the inner core 20 of the first cross section 8 has an oxygen concentration higher than 1800 ppm. Also, the outer core 22 of the first cross section 8 has an oxygen concentration between 1300 ppm and 1800 ppm.

  In this embodiment, oxygen is introduced into the surface of the member 2 in the first cross section 8. Thus, after the reoxidation step, the region called edge 23 in FIG. 8 has oxygen introduced into it (from the surface of the member).

  Thus, in this embodiment, after reoxidation, edge 23 has a first region adjacent to the surface of member 2 (indicated by reference numeral 24 in FIG. 10) having an oxygen concentration between 1300 ppm and 1800 ppm. ) And a second region (indicated by reference numeral 25 in FIG. 10) between the first region 24 and the outer core 22 having an oxygen concentration lower than 1300 ppm.

  In this embodiment, oxygen is introduced into the surface of the member 2 in the second cross section 10.

  Thus, after the reoxidation step, the second cross-section 10 shows an “inner region” (indicated by reference numeral 26 in FIG. 10) having an oxygen concentration lower than 1300 ppm and an oxygen concentration between 1300 ppm and 1800 ppm. Having an “external region” (indicated by reference numeral 27 in FIG. 10). The outer region 27 is adjacent to the surface of the member 2 in the second cross section 10, and the inner region 26 is near the center of the second cross section 10 away from the surface of the member 2 (ie, inside the outer region 27). Located in.

  In this embodiment, after the reoxidation step, member 2 has an average oxygen level (ie, medium oxygen level) between 1300 ppm by weight and 1800 ppm by weight. In other words, after all the oxygen in the member 2 has spread substantially uniformly throughout the member 2 after the reoxidation process, the oxygen level of the member 2 is moderate (ie, between 1300 ppm and 1800 ppm). .

  In FIG. 10, as in FIG. 8, for clarity and ease of understanding, different regions of cross-sections 8, 10 are shown as having distinct discrete boundaries. In practice, however, in this embodiment, after the reoxidation step, the oxygen level across each of the cross sections 8, 10 changes continuously.

  Therefore, in this embodiment, oxygen is introduced substantially uniformly into the surface of the member 2 during the reoxidation process, so that regions of the member 2 having different thicknesses (ie, the first cylinder 4 and the first cylinder 4). The two cylinders 6) tend to have oxygen introduced into them at different average rates (per unit volume). Thus, in this embodiment, after the reoxidation step, the first and second cylinders 4, 6 have a substantially equal average oxygen concentration (ie, a medium oxygen concentration). However, at this stage, oxygen in the cylinders 4 and 6 (that is, in the member 2) does not spread uniformly throughout the member 2.

  Thus, in this embodiment, the reoxidation process is performed on member 2 to increase the average oxygen level in member 2. The reoxidation component is also performed to increase the gradient of oxygen level across (at least a portion of) member 2.

  Referring to FIG. 5 again, after the re-oxidation process (step s12) is performed, the oxygen homogenization process of step s14 is performed. This step is performed to make the oxygen concentration level substantially uniform throughout the member 2.

  The oxygen homogenization step executed in this embodiment in step s14 will now be described.

  FIG. 11 is a process flowchart showing specific steps of the oxygen homogenization process performed on the member 2 in step s14.

  In step s32, the member 2 is placed in a chamber in which oxygen level homogenization occurs throughout the member 2. For convenience, this chamber is hereinafter referred to as a “homogenization chamber”.

In this embodiment, the homogenization chamber is a conventional vacuum furnace. Preferably, the homogenization chamber includes a refractory metal heating element and is capable of maintaining a vacuum better than 10 ⁻⁵ mbar.

  In step s34, the homogenization chamber is filled with an inert gas (eg, argon) such that an inert gas atmosphere is maintained in the chamber during the homogenization process. In other embodiments, instead of filling the chamber with an inert gas, a vacuum may be formed in the homogenization chamber.

  In step s36, the member 2 is heated to a relatively high temperature (in the homogenization chamber). Preferably, the member 2 is heated to between 1000 ° C and 1300 ° C. This temperature range advantageously tends to result in avoiding or mitigating problems associated with very high temperatures. In addition, this temperature range is high enough to provide a relatively fast processing time, and the member 2 (e.g., deformation under its own weight, initial melting, excessive grain growth, or other Tend to be low enough to avoid damage (due to the detrimental metallurgical reaction).

  In general, the oxygen homogenization process may be performed at a higher temperature than the deoxygenation (or reoxidation) process because no reactive chemicals are used. There are suitable high temperature furnaces.

  In this embodiment, the member 2 is heated for a third predetermined period. In this embodiment, the third predetermined period is between 0.5 and 100 hours. Preferably, the third predetermined period is less than 12 hours. This tends to ensure that the homogenization process is relatively cost effective.

  Advantageously, this third predetermined period of time depends on certain parameters, such as the initial oxygen content in the member 2 (ie the oxygen content in the member 2 after the reoxidation process), various parts of the member. Tends to be able to be determined / changed depending on the specified oxygen range, the thickness of the member 2 and the homogenization temperature.

  In this embodiment, the third predetermined period is long enough to cause oxygen homogenization within member 2 to occur (ie, the oxygen gradient within member 2 disappears or is reduced). Accordingly, members 2 having properties that are substantially uniform or change by an acceptable amount in different regions tend to be advantageously produced. Furthermore, for porous powder products, such as those produced by MIM, the heating process performed during oxygen homogenization tends to further sinter the component. This may be tolerated by using a shorter initial sintering time in the MIM process.

  In step s38, after the third predetermined period expires, the homogenization chamber is left for cooling.

  Thus, an oxygen homogenization process is provided.

  FIG. 12 is a schematic diagram (not to scale) of the first cross section 8 and the second cross section 10 after the oxygen homogenization process (ie, after performing step s14 of FIG. 5).

  Similar to that in FIGS. 4, 8, and 10, in FIG. 12, the regions within cross-sections 8, 10 having relatively high oxygen concentrations (ie, greater than 1800 ppm) are filled with black and medium. Regions with moderate oxygen concentrations (ie, within the range of 1300 ppm to 1800 ppm) are shown by cross-hatching, and regions with relatively low oxygen concentrations (ie, below 1300 ppm) are not filled.

  In this embodiment, after the oxygen homogenization step, the member 2 has a medium oxygen concentration. Furthermore, this oxygen concentration is substantially uniform throughout the member. Accordingly, in FIG. 12, the first and second cross sections 8 and 10 are cross-hatched.

  Accordingly, a process is provided for producing a titanium alloy member having a substantially uniform oxygen level at a concentration from 1300 ppm to 1800 ppm by weight.

  The advantage provided by the above process is that the parts are produced using powder metallurgy manufacturing techniques. This tends to result in near net shape members being produced with very little waste. Furthermore, machining can be prohibitively expensive, and it can be relatively easy to create relatively complex shapes.

  A further advantage provided by the above-described process is the use of relatively inexpensive alloy powders (generally not suitable for the production of structural parts due to their high oxygen content) ) Tend to be able to produce. The member may be formed using a low quality and low cost (ie, high oxygen concentration) alloy that is then processed (as described above) to reduce and homogenize oxygen. A relatively higher quality (ie, lower oxygen concentration) component is produced. Traditionally, higher quality (ie, lower oxygen concentration) components are produced using relatively high quality alloys. These tend to be relatively expensive. For example, the cost of a high quality titanium alloy powder may be about £ 150 to £ 250 per kilogram, whereas the cost of a lower quality titanium alloy powder is £ 20 to £ 100 per kilogram There is. The cost of alloy powders, for example, tends to be a very large part of the total manufacturing cost of components produced using it. The above described process tends to result in significant cost savings compared to conventional methods.

  The above described process tends to result in the desired oxygen content in the member being achieved at a lower cost.

  The above described process advantageously addresses the problem of removing bulk oxygen from a member (eg, a titanium alloy member). Furthermore, the above-described steps can be performed on an industrial scale. As described above, removal of bulk oxygen from the member first removes oxygen from the surface of the member (ie, reduces the oxygen level of the portion of the member proximate to the surface of the member) and then the entire member. May be performed by equalizing the oxygen level through. This reduces the oxygen level throughout the bulk of the member (ie, the majority of the body). In other words, the oxygen level is not only reduced at or close to the surface of the member. Instead, the oxygen level tends to be reduced throughout the (bulk) member. Conventionally, high temperature chemical treatment has been applied to titanium powder to reduce the oxygen content of the titanium powder. Such high temperature chemical treatment is generally not suitable for fine powder sizes (eg preferred for metal injection molding) due to the strong tendency of the powder particles to sinter. The process described above can be advantageously applied to members made from powders of any size. This is because the process is performed after the formation of the member (ie after the powder has been sintered).

  A further advantage provided by the above process is that it tends to be possible to achieve the desired oxygen concentration in the member. This can be achieved using the deoxygenation and reoxidation steps described above. At certain concentrations, oxygen strengthens and hardens the titanium alloy. This tends to be an important alloy additive in many alloys. However, if the oxygen concentration in the alloy is too high, oxygen tends to embrittle the alloy and reduce toughness and ductility.

  Many conventional processing operations, including forging and heat treatment, introduce oxygen into the alloy. This introduced oxygen is usually limited to a thin region near the outer surface of the member (called “alpha case” in the Ti-6Al-4V alloy). This thin layer can be machined or removed chemically. However, machining tends to be expensive and chemical processing (called “chemical milling”) tends to be expensive and subject to increasingly restrictive environmental and safety legislation. The above described process tends to result in a lower cost and environmentally acceptable alpha case removal method.

  A further advantage provided by the above-described process is that any of the deoxygenation, reoxidation, and oxygen homogenization processes may be performed on multiple members simultaneously. Thus, the cost (per member) of performing any or all of these operations can be greatly reduced.

  At any stage in the above process for producing a titanium alloy member, there is a tendency to be able to assess or determine the oxygen level in the member. Conventional techniques may be used to assess or determine the average oxygen level in the member. For example, this is the process of “Oxygen Determination by Gas Fusion” using a TC400 series Leco ™ machine, for example, on a test member that is substantially identical to the member being produced. (Or other hardness test process) may be performed. Conventional techniques may also be used to assess or determine the oxygen level gradient through the member by testing the selected piece of material.

  In the above embodiment, after step s2 is completed, an oxygen reduction process is performed on the solid material and the member has a density in the range of 92-100% (ie, the member is “fully solidified”). (Fully consolidated) ").

  A further embodiment will now be described in which the oxygen reduction step is performed before the member is fully solidified.

  FIG. 13 is a process flow diagram illustrating certain steps of the process for producing a titanium alloy member, in which the oxygen reduction process is performed before the member is fully solidified.

  In step s42, a member is formed and partially solidified. The term “partially consolidated” is used herein to mean a member having a solid density of less than 92%, preferably in the range of 70-80%. In other embodiments, the terms “fully solidified” and / or “partially solidified” may mean a different range of solid densities.

  The process of forming and partially solidifying the member will now be described in more detail with reference to FIG. The remaining steps (steps s44 and s46) of the process of FIG. 13 will be described after the description of FIG.

  FIG. 14 is a process flow diagram illustrating certain steps of the process of partially solidifying the member, performed in step s42 of FIG.

  In step s48, a metal injection molding process is performed to produce a so-called “green part”.

  In this further embodiment, the metal injection molding process is performed as described above with reference to step s6 of FIG.

  In step s50, after the green part is cooled and released, a part of the binder material is removed from the green part to produce a so-called “brown part”.

  In this further embodiment, the process of producing brown parts from green parts is performed as described above with reference to step s7 of FIG.

  In this further embodiment, the produced brown part has a solid density of about 50-60%. In other words, the brown part is relatively porous. In addition, the brown part has a substantially uniform porosity throughout the part and is “open porosity” (which is a porous interconnected internally and open to the surface). Have what is known as).

  In step s52, the brown part produced in step s50 is "partially sintered".

  In this further embodiment, a conventional sintering process is used. The brown part is sintered at a temperature in the range from 1000 ° C to 1300 ° C. The brown part is sintered until it has a solid density of less than 92%, preferably in the range of 70-80%. In other embodiments, the partially solidified member has a solid density within a different range (eg, 60-92%).

  Thus, a process is provided for forming and partially solidifying the member.

  Referring now again to FIG. 13, in step s44, for a partially solidified member (ie, having a solid density of less than 92% and preferably having a solid density in the range of 70-80%). Thus, the oxygen reduction process is executed.

  In this further embodiment, the oxygen reduction step is performed as described above with reference to FIG. 5 to reduce the level of oxygen (ie, oxygen concentration) in the member. This process tends to reduce the oxygen concentration in the partially solidified member from a high level to a desired medium level.

  The advantage provided by performing the oxygen reduction process on a partially solidified member (ie, a member that is still relatively porous) is that deoxygenation and / or reoxidation process steps during deoxidation process steps. The fluid used to perform the oxygen / reoxidation (ie, vaporized material, or further liquefied material) may penetrate deeper into the member than would be the case for a fully solidified member. This is possible (i.e., the fluid passes more easily between the grains of the partially solidified member than for a fully solidified member). Therefore, deoxygenation / reoxidation of relatively porous members tends to be relatively efficient. This tends to reduce the time and cost of the deoxygenation and / or reoxidation process.

  A further advantage of performing the oxygen reduction process on a partially solidified member is that the oxygen concentration tends to be more uniform throughout the member. Thus, less oxygen homogenization of the member may be used to achieve the desired level of oxygen uniformity within the member.

  A further advantage provided by performing the oxygen reduction process on a partially solidified member is that the member is fully sintered / solidified (ie, its solid density is in the range of 92% to 100%). The oxygen homogenization process tends to be able to be performed on the partially solidified member at a sufficiently high temperature. Accordingly, the number of process steps for producing a member is reduced, which tends to reduce the cost of producing the member.

  In step s46, if desired (in a vacuum or inert atmosphere) to fully sinter / solidify the part (ie resulting in its solid density being in the range of 92% to 100%). A) The sintering process is carried out. In other embodiments, different types of consolidation steps may be performed to fully sinter / solidify the member. For example, in other embodiments, a hot isostatic pressing (HIP) process is performed.

  Thus, a step of producing a titanium alloy member (in which an oxygen reduction step is performed on a partially solidified member) is provided.

  In the above embodiment, the member is formed as described above with reference to FIG. 2 (in step s2). In particular, the member is formed using a process that includes a metal injection molding process. However, in other embodiments, the members are formed using different net shape or near net shape manufacturing processes. The term “near-net shape manufacturing process” is used herein to mean that the initial production of an item is (substantially) the same (substantially) as the final (net) shape. Is used to mean a process that is close to (ie, within acceptable tolerances). This tends to reduce the need for surface finishing of the object. For example, in other embodiments, parts / objects / items are produced using one or more of the following near net shape manufacturing processes: casting, permanent mold casting, powder metallurgy, linear friction welding, metal Injection molding, rapid prototyping, spray forming, and superplastic molding. Such a process may include using other powder metallurgy processes. Such processes may include, for example, hot isostatic pressing (HIP), cold isostatic pressing (CIP), and 3D powder melting using a scanning laser or electron beam. Such a process may be used to form fully or partially solidified metal or alloy members / objects. Such a process may use feedstock produced by a conventional ingot route, or, via a powder metallurgy route, billets, plates, made from a lower cost, higher oxygen alloy powder, Alternatively, solid feedstock materials such as bars may be used. The metal / alloy powder used to produce the object may be, for example, a mixed elemental powder. For example, an object made of Ti-6Al-4V may be produced from a mixed elemental powder made by mixing titanium, aluminum, and vanadium powders. The mixed elemental powder tends to be alloyed and homogenized during the sintering process. Objects made of Ti-6Al-4V may also be produced from mixed elemental powders made by mixing titanium powder with Al-V master alloy powder.

  In the above embodiment, the member is an alloy containing titanium with 6% aluminum and 4% vanadium (Ti-6Al-4V or 6-4, 6/4, also known as ASTM B348 Grade 5). Formed). Also, in the above embodiment, the alloy includes a certain amount of oxygen in the solid solution. However, in other embodiments, the members are formed from different materials. For example, in other embodiments, the member is formed from a pure (ie, non-alloy) metal or a different type of alloy than that used in the above embodiments. Preferably, the member is a metal or alloy that has significant oxygen solubility and diffusivity at convenient processing temperatures, and a suitable deoxygenated metal (in the form of a vapor or liquid, or in solution) is present. Where the deoxygenated metal oxygen negative free energy of formation is greater than the deoxygenated metal / alloy oxygen negative free energy of formation. For example, the member may be formed from any of the following metals or an alloy of one or more of the following metals: titanium, tantalum, vanadium, zirconium, molybdenum, niobium.

  In other embodiments, the object / member is made of the alloy Ti-3Al-2.5V. Objects made of this alloy may be required to have a relatively low maximum oxygen level (eg, 1200 ppm or less) (eg, when used in certain applications). In general, the metal injection molding (MIM) process can add about 1000 ppm of oxygen to the alloy. Thus, it has traditionally been impossible or impossible to produce objects made of Ti-3Al-2.5V and having a relatively low maximum oxygen level using the MIM process. is there. However, such an object can be made using the process described above. For example, (i) providing some Ti-3Al-2.5V powder, (ii) producing an object from the powder using a MIM process, and (iii) performing a deoxygenation process (see, eg, FIG. (Iv) (as described above with reference), and (iv) performing a homogenization step (if necessary) (eg, as described above with reference to FIG. 11) to produce such an object. Also, for example, (i) Ti-6Al-4V powder combined with commercial pure titanium powder (CP), and / or other element or master alloy powder, substantially the same as Ti-3Al-2.5V. Making a mixed powder having a composition, (ii) producing an object from the powder using the MIM process, and (iii) performing a deoxygenation process (eg, as described above with reference to FIG. 6) , (Iv) performing a homogenization step (if necessary) (eg, as described above with reference to FIG. 11) to produce such an object. The composition range of Ti-3Al-2.5V tends to be quite wide, and therefore it tends to be possible to produce standards-compliant objects. The oxygen level in the body tends to be advantageously homogenized during sintering. Ti-6Al-4V, and CP material / powder, and other suitable element or master alloy powders that may form Ti-3Al-2.5V mixed powders are readily available and relatively inexpensive In contrast, Ti-3Al-2.5V tends to be more difficult and more expensive to obtain.

  In the above embodiments, the member is a member (eg, a member suitable for use in or by a single machine). However, in other embodiments, the member is a different type of entity, object, or item made of metal or alloy (eg, ingot, billet, plate, sheet, wire, or bar, or some other intermediate Product form).

  In the above embodiment, the shape and size of the members are as described in more detail above with reference to FIG. The shape of the member is the shape of two coaxial cylinders arranged with the ends connected to each other. The first cylinder has a diameter of about 20 mm and a length of about 100 mm, and the second cylinder has a diameter of about 9 mm and a length of about 100 mm. However, in other embodiments, the size and / or shape of the member is different, i.e., the member may be of any suitable size and shape.

  In the above embodiment, the step of forming a member (step s2) is used to form a single member. In the above embodiment, the oxygen reduction step (step s4) is performed on a single member at a time. However, in other embodiments, the step of forming the member is used to simultaneously form a different number of substantially identical or different member (s). In other embodiments, the oxygen reduction step (step s4) is performed simultaneously on a different number of substantially identical or different members. Simultaneously performing the forming process or the oxygen reduction process on a plurality of members tends to advantageously reduce the cost of the process per member.

  In the above embodiment, the sintering of the member is carried out for the time period specified above at the temperature specified above. However, in other embodiments, the sintering of the member is performed at different suitable temperatures and / or over different suitable periods.

  In the above embodiment, an oxygen concentration higher than 1800 ppm has been described as a high level. Also, oxygen concentrations between 1300 ppm and 1800 ppm have been described as moderate (desired) levels. Also, oxygen concentrations below 1300 ppm were described as low levels. However, in other embodiments, the high, medium, and / or low oxygen concentration levels are different. In other embodiments, the deoxygenation step is used to reduce the average oxygen concentration in the member from any level to any other level. In other embodiments, the re-oxidation process is used to increase the average oxygen concentration in the member from any level to any other level.

  For example, in other embodiments, the desired (average) oxygen concentration is between 1000 ppm and 2300 ppm. In other embodiments, the desired oxygen concentration is between 1300 ppm and 1800 ppm. In other embodiments, the desired oxygen concentration is between 1700 ppm and 1800 ppm. In other embodiments, for example, when a Ti-6Al-4V Extra Low Interstitial (ELI) object is desired, the desired oxygen concentration is 1300 ppm or less, or 1000 ppm or less.

  Also, for example, in other embodiments, a high (average) solute concentration level, i.e., an initial solute concentration level of an untreated member, or an initial solute concentration level of a raw material forming the member (e.g., by using MIM). Is between 2300 ppm and 10000 ppm. In other embodiments, the high solute concentration level is between 5000 ppm and 10,000 ppm (eg, 8000 ppm). In other embodiments, the high solute concentration level is greater than 10,000 ppm. Titanium alloy powders with a high oxygen concentration (eg 8000 ppm) tend to be advantageously cheaper, and the objects produced from such powders can be processed as described above to form objects with much lower oxygen concentrations. Can be deoxygenated.

  In other embodiments, the desired solute concentration level is a percentage of the (high) initial solute concentration level. For example, the desired solute concentration level may be half, or one quarter, or one fifth of the (high) initial solute concentration level.

  In the above embodiment, the deoxygenation chamber, the reoxidation chamber, and the homogenization chamber are each configured as described above (the deoxygenation chamber was described above with reference to FIG. 7). However, in other embodiments, one or more of these chambers are configured differently (eg, made from different suitable materials, or have different or additional equipment), It still provides the above functionality.

  In the above embodiment, the deoxygenation step (performed in step s10 as described above) fills the bottom of the deoxygenation chamber container with material (so that the member is completely above the material level), This is done by sealing the container and heating the container so that the material is vaporized. This vaporized material deoxygenates the member. However, in other embodiments, the deoxygenation chamber container is filled with the material such that the member is partially or fully submerged within the material. The container may then be heated so that the material is liquefied or vaporized. This liquefied / vaporized material tends to deoxygenate the member.

  Also, in the above embodiment, the reoxidation process (performed in step s12 as described above) causes the reoxidation chamber container to be further materialized (so that the member is completely immersed in the additional material). Filling, sealing the container and heating the container so that further substances are liquefied. This further liquefied material reoxidizes the member. However, in other embodiments, the container of the reoxidation chamber is filled with additional material so that the member is partially immersed in the additional material or not at all in the additional material. If the member is partially immersed in the further material, the container may then be heated so that the material is liquefied or vaporized. This further liquefied / vaporized material tends to oxidize the component. If the member is not immersed at all in the further material, the container may then be heated so that the material is vaporized. This further vaporized material tends to oxidize the component.

  The advantage provided in embodiments in which the member is not immersed at all in the liquefied / further material (ie, the member is deoxygenated or reoxidized by steam) is that after processing, the member is disposed of as waste (eg, It is only thinly covered with salt). This tends to facilitate cleaning / cleaning of the member. In addition, removal of the member from the processing container tends to be facilitated. This tends to be in contrast to embodiments in which the member is fully or partially immersed in the liquefied / further material. In such embodiments, after processing, the member tends to be at least partially covered with solid waste material (which may be removed in some way (eg, typically by hot water washing)). . This member covering problem can be addressed by providing a method of separating the member from the liquid before the waste solidifies.

  A further advantage provided in embodiments in which the member is not immersed at all in the liquefied material / further material (ie, the member is deoxygenated or reoxidized by steam) is that less material / further material is used. It is that there is a tendency to be. This tends to result in cost savings.

  In the above embodiment, the material includes a chemical oxygen scavenger and a flux. However, in other embodiments, the material comprises a different set of suitable components. For example, in other embodiments, no flux is used. In other embodiments, a relative ratio of chemical oxygen scavenger and flux different from the relative ratio used in the above embodiment is used.

  In the above embodiment, the additional materials include oxidizing chemicals and fluxes. However, in other embodiments, the additional material comprises a different set of suitable components. For example, in other embodiments, no flux is used. In other embodiments, a relative ratio between the oxidizing chemical and the flux that is different from the relative ratio used in the above embodiment is used.

  In the above embodiment, the chemical oxygen scavenger in the substance is calcium. However, in other embodiments, one or more different chemical oxygen scavengers are used in place of or in addition to calcium. For example, sodium or a different alkaline earth metal may be used.

  In the above embodiment, the oxidizing chemical in the further substance is calcium oxide. However, in other embodiments, one or more different oxidizing chemicals are used in place of or in addition to calcium oxide. For example, sodium oxide may be used.

  In the above embodiment, the flux used within the material and further material is calcium chloride. However, in other embodiments, one or more different flux materials are used in place of or in addition to calcium chloride in either or both of the deoxygenation and reoxidation steps. For example, sodium chloride may be used. The sodium chloride / calcium chloride eutectic mixture has a lower melting temperature than calcium chloride. This may be desirable in some steps.

  In the above embodiment, the substance and the further substance are solid powders / pellets that are later liquefied / vaporized. However, in other embodiments, the material, and / or additional material fluxes, and / or chemical reactants may have different states. For example, a vapor form flux may be used.

  In the above embodiment, the deoxygenation step preferably includes heating the deoxygenation chamber to 1000 ° C. to 1200 ° C. for 0.5 to 100 hours. Performing the deoxygenation process at a relatively high temperature (eg, 1100 ° C.) ensures that the oxygen associated with the produced part is more evenly and advantageously distributed within the part (ie throughout the produced part). The oxygen concentration is more uniform). This may eliminate or reduce the need to perform further homogenization for some objects. However, in other embodiments, during the deoxygenation process, the deoxygenation chamber is heated to a different suitable temperature. In other embodiments, the deoxygenation step is performed over a different suitable period.

  In the above embodiment, the reoxidation step includes heating the reoxidation chamber, preferably from 1000 ° C. to 1200 ° C. for 0.5 to 100 hours. However, in other embodiments, during the reoxidation process, the reoxidation chamber is heated to a different suitable temperature. In other embodiments, the re-oxidation step is performed over a different suitable period.

  In the above embodiment, the oxygen homogenization step preferably includes heating the deoxygenation chamber to 1000 ° C. to 1300 ° C. for 0.5 to 100 hours. However, in other embodiments, the homogenization chamber is heated to a different suitable temperature during the oxygen homogenization process. In other embodiments, the homogenization step is performed over a different suitable period (eg, between 50 hours and 100 hours, or between 70 hours and 100 hours).

  In the above embodiment, the member is cleaned using water to remove the flux and dilute acid to remove other residues. However, in other embodiments, the member is cleaned using a different suitable process. Also, in other embodiments, the member is not cleaned.

  In the above embodiments, during deoxygenation (or reoxidation) of the member, oxygen is removed (or added) substantially uniformly from the surface of the member. However, in other embodiments, oxygen is not removed or added substantially uniformly during these steps. For example, in other embodiments, during the deoxygenation and / or reoxidation process, a portion of the member may be masked from the steam (or may not be in contact with the steam).

  In the above embodiment, the deoxygenation and reoxidation process is stopped by stopping the heating of the associated chamber after the associated period. However, in other embodiments, the deoxygenation and / or reoxidation of the member may be stopped by different methods. For example, in other embodiments, the reactants can be achieved after the desired average oxygen content has been achieved by supplying only sufficient deoxygenation / reoxidation chemistry to remove / introduce a specific ratio of oxygen. Or the chemical reaction may reach equilibrium.

  In the above embodiment, the above steps are performed to remove (or add) bulk oxygen from the component parts. However, in other embodiments, the process may be performed to remove or add different interstitial solutes from the member. For example, in other embodiments, the process is performed to remove carbon, hydrogen, or nitrogen from the member.

  Some of the process steps shown in the flowchart above may be omitted (eg, the re-oxidation process of step s12, or the homogenization process s14), or such process steps are presented above, Note that it may be performed in a different order than the order shown in the figure. Furthermore, although all process steps have been shown as separate time sequential steps for convenience and ease of understanding, nonetheless, some of the process steps are: In practice, they are executed simultaneously or at least to some extent in time overlap.

  In the above embodiment, an independent homogenization process is performed (eg, in step s14) to equalize the oxygen concentration level throughout the member / object. However, in other embodiments, such a process is not performed. For example, the homogenization process may not be performed because changes in oxygen concentration in the produced object can be tolerated. Further, for example, the oxygen in the produced object is sufficiently homogenized by the deoxygenation and / or reoxidation process, and thus the homogenization process may not be performed.

Claims (32)

A method of producing an object,
The object is made of metal or alloy, the object has a desired shape, the object is a non-porous object;
The method
Providing some metal or alloy, wherein the provided metal or alloy has a first average solute level;
Using the provided metal or alloy to perform a net shape or near net shape manufacturing process to produce an intermediate object, wherein
The intermediate object has the desired shape;
The intermediate object is a non-porous object;
The intermediate object has a second average solute level, and the second average solute level is greater than or equal to the first average solute level;
Performing a solute level changing step on the intermediate object to change the solute level in at least the bulk of the intermediate object to provide the intermediate object having a third average solute level, thereby Providing an object, wherein:
The third average solute level is different from the second average solute level;
Method.   The method of claim 1, wherein the third average solute level is lower than the first average solute level.   The method of claim 1 or claim 2, wherein the solute level reduction step is performed such that the intermediate object substantially retains its shape and solid density.   4. The method according to any one of claims 1 to 3, wherein the object is made of a titanium alloy and the provided metal or alloy is a titanium alloy.   The method according to claim 1, wherein the object is made of Ti-6Al-4V.   The method according to claim 1, wherein the object is made of Ti-3Al-2.5V.   The method according to any one of claims 1 to 6, wherein the solute level is one of an oxygen level, a carbon level, a hydrogen level, or a nitrogen level.   The method of claim 7, wherein the solute level is an oxygen level.   Performing the solute level changing process includes exposing at least a portion of the intermediate object to a fluid, wherein the fluid includes a chemical reactant, the chemical reactant being different from the metal or alloy. 9. A method according to any one of the preceding claims having a level of reactivity towards the solute.   The method of claim 9, wherein the chemical reactant is an alkaline earth metal.   The method of claim 10, wherein the alkaline earth metal is calcium.   The fluid further comprises a flux material, the flux material for facilitating removal of reaction products between the chemical reactant and the metal or alloy from the surface of the object. The method according to any one of claims 11 to 11.   The method of claim 11, wherein the flux material is calcium chloride.   The method according to any one of claims 9 to 13, wherein the fluid is a liquid.   The method according to claim 9, wherein the fluid is steam.   16. A method according to any one of the preceding claims, wherein the produced object and the intermediate object each have a solid density in the range of 92% to 100%.   17. A method according to any one of claims 1 to 16, wherein an amount of the metal or alloy is provided in powder form.   The method of claim 17, wherein the provided metal or alloy is in the form of a mixed powder.   The method of claim 18, wherein the mixed powder comprises Ti-6Al-4V powder and titanium powder.   2. The net shape or near net shape manufacturing process is selected from the group consisting of casting, permanent mold casting, powder metallurgy, linear friction welding, metal injection molding, rapid prototyping, spray forming, and superplastic forming. The method according to any one of claims 19 to 19.   21. The method of claim 20, wherein the net shape or near net shape manufacturing process is metal injection molding. The solute level changing step includes
Removing a certain amount of solute from the intermediate object, thereby reducing the average solute level of the intermediate object;
Adding an amount of solute to the intermediate body, thereby increasing the average solute level of the intermediate body, wherein
The amount by which the average solute level of the intermediate object is reduced is greater than the amount by which the average solute level of the intermediate object is increased;
The method according to any one of claims 1 to 21.   23. The method of claim 22, wherein adding the amount of solute is performed after removing the amount of solute.   The first average solute level is between 2300 parts per million and 10,000 parts per million, between 5000 parts per million and 10,000 parts per million, and higher than 10,000 parts per million. 24. A method according to any one of claims 1 to 23, wherein the level is within a range selected from the group of ranges.   The third average solute level is between 1000 parts per million and 2300 parts per million, between 1300 parts per million and 1800 parts per million, 1700 parts per million and 1800 parts per million The level within a range selected from the group consisting of: less than 2000 weight parts per million, less than 1300 weight parts per million, and less than 1000 weight parts per million. The method as described in any one of.   26. The method of any one of claims 1 to 25, wherein performing the solute level reduction step comprises heating the intermediate object to between 1000 <0> C and 1200 <0> C. Performing the solute level changing step to change the solute level of at least the bulk of the intermediate object;
Removing a certain amount of solute from the surface of the intermediate object,
After removing the amount of solute from the surface of the intermediate object, performing a homogenization step on the intermediate object to increase the uniformity of the solute level in the intermediate object. 27. A method according to any one of claims 1 to 26.   28. The method of claim 27, wherein the homogenizing step is performed such that a solute level within the object is substantially uniform throughout the object.   29. The method of claim 27 or claim 28, wherein performing the homogenization step comprises heating the object to between 1000C and 1300C for between 0.5 hours and 100 hours. Method.   30. An object produced by carrying out the method according to any one of claims 1 to 29.   A method of producing an object, said method being substantially as described herein with reference to the accompanying drawings.   Object as described herein with reference to the accompanying drawings.

Images