JP6604869B2 - Platinum palladium rhodium alloy - Google Patents

Description

  The present invention relates to a platinum palladium rhodium alloy mainly used at high temperatures.

  Platinum rhodium alloy is known as a material excellent in workability, weldability, heat resistance and corrosion resistance. High strength from room temperature to high temperature compared to pure platinum, which has similar advantages, and less consumption due to oxidation and volatilization of iridium compared to platinum iridium alloy, heat-resistant alloy, chemical instrument, conductive material, discharge electrode material, contact material It is used in a wide range of fields.

  The following publicly known documents are examples of heat-resistant applications of conventional platinum rhodium alloys.

  Patent Document 1 discloses a platinum alloy composed of Pt and Rh as a constituent material of a glass fiber manufacturing nozzle and bushing.

  Patent Document 2 discloses that a platinum rhodium alloy is suitable for a glass ceramic material manufacturing apparatus. As in these examples, the platinum rhodium alloy is used as a high temperature member having high oxidation resistance.

  Patent Document 3 discloses a binary platinum rhodium alloy wire incorporated in a temperature sensor element having a heat resistance of 1000 ° C., and the Rh content is preferably 10 to 20 mass%.

  Patent Document 4 discloses that a platinum alloy containing 5 to 15 mass% of Rh or Rh is suitable as an electrode wire of a temperature sensor used at a high temperature.

  As in these examples, platinum rhodium alloys are also suitably used as conductive materials that require heat resistance and high temperature strength.

JP 2003-261350 A JP-A-2005-119959 JP-A-11-40403 JP2010-60404

  The heat-resistant material is naturally required to have a high melting point, high strength, high corrosion resistance, and the like, and it is desirable that the heat-resistant material can be used stably for a long period of time.

  However, when a conventional platinum rhodium alloy is used at a high temperature for a long period of time, grain growth inevitably occurs, the crystal grains become coarse, and grain boundary fracture may occur. For example, there is a composition in which a binary platinum rhodium alloy is recrystallized at 600 ° C. or higher and is coarsened until the crystal grain size exceeds 100 μm only by holding it at a high temperature of 1000 ° C. or higher for several hours. Such a platinum rhodium alloy has insufficient reliability for stable use for a long period of time because the probability of breaking due to slipping of the grain boundary increases with time even though the initial performance is high.

  Also, Pt and Rh (especially Rh) are low in production volume and the country of origin is unevenly distributed, and most of the demand for Pt and Rh is for industrial use. have.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a platinum palladium rhodium alloy capable of maintaining strength without coarsening crystal grains even when used at a high temperature for a long time. To do.

  In the first invention, a total of 0.1 to 1.2 mol% of alkaline earth metal elements composed of at least one of Ca, Sr, and Ba, 0.1 to 43 mol% of Pd, and 1 to 43 mol of Rh Platinum palladium, characterized in that the second phase precipitated particles mainly composed of Pt, Pd and the alkaline earth metal are dispersed in the parent phase. Rhodium alloy. In addition to the above components, unintended inevitable impurities mixed from raw materials or processing steps including melting crucibles may be included.

  The second invention relates to the first invention, and is characterized by being used at 600 ° C. or higher. Here, the use form of the platinum rhodium alloy is not limited, and may be any form such as a wire, a plate, a strip, and a tube, such as a crucible material, a heater wire, a sensor lead wire, and a spark plug discharge electrode. .

  According to the present invention, since the second phase precipitated particles are present, the movement of the grain boundary is restricted, and as a result, the platinum palladium rhodium alloy in which the crystal grains are not coarsened even when used at a high temperature for a long time. It can be. Therefore, it is possible to provide a platinum palladium rhodium alloy that can be used at a high temperature for a longer period of time. Further, the strength is improved by the effect of precipitation strengthening, and the advantage that the elongation at break is large because the particle size is fine is also obtained.

  Almost all of the alkaline earth metal is present as second-phase precipitated particles, and the parent phase portion is substantially a PtPdRh alloy. Therefore, electrical conductivity and thermal conductivity are equivalent to conventional platinum rhodium alloys and are not impaired, and are particularly suitable as high-temperature conductive materials. Further, since the eutectic point between the second phase precipitated particles and the parent phase is lower than that of the parent phase PtPdRh alloy, welding is also easy.

  Furthermore, according to the present invention, by replacing a part of Pt with Pd and adding a small amount of alkaline earth metal, the oxidation resistance and high melting point characteristics of Rh are maintained, and the strength is higher than that of the platinum rhodium alloy. It is possible to obtain an alloy that can be used at a high temperature for a long time. In addition, the amount of Pt and Rh used can be relatively suppressed, and the material can be manufactured at a low cost.

  The present invention can be applied to all fields where conventional platinum rhodium alloys are used, and is particularly effective when used as a heat-resistant material, and durable when applied to crucibles, heater wires, sensor lead wires, spark plug discharge electrodes, etc. Improves yield, yield, reliability, and lifetime. As a result, it is possible to reduce the thickness and diameter of the conventional dimensions, and it is expected to reduce costs and save precious metal resources.

FIG. 1 is a diagram in which the abscissa represents the Rh concentration and the ordinate represents the tensile strength of the alloys of Examples and Comparative Examples. FIG. 2 is a graph showing the Rh concentration on the horizontal axis and the elongation on the vertical axis for some alloys in the examples and comparative examples. FIG. 3 shows an alloy cross section of Example 4.

(First invention)
In the first invention, a total of 0.1 to 1.2 mol% of alkaline earth metal elements composed of at least one of Ca, Sr, and Ba, 0.1 to 43 mol% of Pd, and 1 to 43 mol of Rh Platinum palladium, characterized in that the second phase precipitated particles mainly composed of Pt, Pd and the alkaline earth metal are dispersed in the parent phase. Rhodium alloy.

  Here, when the content of the alkaline earth metal is less than the above range, the precipitation of the second phase is insufficient, so that excessive grain growth cannot be suppressed, and when the content exceeds the above range, Since the second phase is excessively precipitated, the oxidation resistance and toughness are deteriorated, and the second phase is easily cracked during processing.

  The area ratio of the second phase is preferably 10% or less. When the area ratio of the second phase exceeds 10%, it is an appearance of excessive precipitation, which deteriorates the oxidation resistance and toughness, and easily breaks during processing. In addition to the above components, unintended inevitable impurities mixed from raw materials or processing steps including melting crucibles may be included. The area ratio is obtained by cutting a platinum palladium rhodium alloy, polishing the cut surface to a mirror surface, and observing the polished surface with an optical microscope, SEM, or other observation means in a finite area included in the observation field. The area ratio of the second phase is visible.

  If the content of Rh exceeds 43 mol%, it becomes difficult to process. The content of Rh is more preferably 5 to 28 mol%. When the content of Pd exceeds 43 mol%, defects are likely to occur due to gas occlusion. The content of Pd is more preferably 1 to 28 mol%. Further, the total content of Pd and Rh is preferably 6 mol% ≦ Pd + Rh ≦ 56 mol%.

  The alkaline earth metal contained in the platinum palladium rhodium alloy may be any one of Ca, Sr and Ba, but two or more are selected, for example, two kinds of Ca and Sr, two kinds of Sr and Ba are platinum. You may make it contain in a palladium rhodium alloy. Moreover, you may contain all three types in a platinum palladium rhodium alloy. Even when the alkaline earth metal is two or more, or all three of Ca, Sr, and Ba, the same effect can be achieved as when any one of them is used.

(Second invention)
The second invention relates to the first invention, and is characterized by being used at 600 ° C. or higher.
If it is the platinum palladium rhodium alloy used in the said range, a use will not be specifically limited, It can use as various embodiments. For example, crucible, thermistor lead, spark plug discharge electrode, pressure sensor, heater, resistance temperature detector, carbon monoxide and flammable gas sensor heater and resistance temperature detector, solid electrolyte gas sensor lead, semiconductor gas sensor lead, etc. It is. Particularly preferred is a platinum palladium rhodium alloy in which the production process includes a step of 1000 ° C. or higher or the use temperature is 800 ° C. or higher.

  Examples of the present invention will be described.

  First, a predetermined amount of alkaline earth metal, Pt, Pd and Rh raw materials were blended, and the whole amount was arc-melted. The obtained ingot was annealed at 1000 ° C. for 1 hour, and processed to φ0.29 mm by wire drawing.

  A φ0.29 material was annealed at 1400 ° C. for 1 hour to obtain a test piece. And the following measurements were performed using the test piece.

  The area ratio is the area ratio of the second phase measured by cross-sectional observation. The grain size is an average crystal grain size measured by etching the alloy cross-section and by a quadrature method defined in JIS H 0501 (a copper grain size test method). Tensile strength and elongation were measured with a tensile tester.

  Table 1 shows the compositions and test results of the alloys of the examples and comparative examples. “AE” in Table 1 represents “alkaline earth metal element”. Table 2 shows the elongation for some alloys. FIG. 1 is a diagram in which the abscissa represents the Rh concentration and the ordinate represents the tensile strength of the alloys of Examples and Comparative Examples. FIG. 2 is a graph showing the Rh concentration on the horizontal axis and the elongation on the vertical axis for some alloys in the examples and comparative examples.

  The alloy cross section of Example 4 is shown in FIG. When analyzed by EPMA, the second phase precipitated in Examples and Comparative Examples was identified as an intermetallic compound mainly composed of Pt, Pd and alkaline earth metal.

  From Table 1, it can be seen that the alloy of the example has an area ratio of the second phase of 10% or less, and even when annealed at a high temperature, the particle size is maintained as fine as 100 μm or less. Moreover, it can be seen from the results of the examples that when the content of the alkaline earth metal is large, the area ratio of the second phase tends to increase.

  From FIG. 1, it can be seen that the alloys of these examples have higher tensile strength and improved strength compared to platinum rhodium alloys having the same Rh addition concentration.

  FIG. 2 shows that the elongation of the alloys of some examples is higher than that of the platinum rhodium alloy having the same Rh addition concentration.

  From the above results, it has been clarified that the effects as described above can be achieved according to the present invention.

Claims (2)

  A total of 0.1 to 1.2 mol% of alkaline earth metal elements composed of at least one of Ca, Sr, and Ba, 0.1 to 43 mol% of Pd, and 1 to 43 mol% of Rh, and the balance Pt and A platinum palladium rhodium alloy, which is an alloy composed of inevitable impurities, wherein the second phase precipitated particles composed of Pt, Pd and the alkaline earth metal are dispersed in the matrix phase.   The platinum palladium rhodium alloy according to claim 1, wherein the platinum palladium rhodium alloy is used at 600 ° C or higher.