JP5457018B2 - Platinum iridium alloy and method for producing the same - Google Patents

Description

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

  Platinum iridium alloys are superior in heat resistance and corrosion resistance, and have higher strength than pure platinum, which has similar advantages. Therefore, platinum iridium alloys are used in a wide range of fields such as heat-resistant alloys, chemical instruments, conductive materials, and contact materials. Yes. As heat-resistant materials, attempts have been made to improve performance with various additive elements in addition to simple binary alloys. The following publicly known documents are examples of conventional heat-resistant applications of platinum iridium alloys.

Patent Document 1 proposes a platinum iridium alloy containing 5 to 40 wt% of Ir as a crucible material for melting lead glass.
In Patent Document 2, as a heat-resistant material having high high-temperature strength and excellent room temperature toughness, a platinum iridium alloy with Ir exceeding 0% by weight and less than 50% by weight, and this binary alloy include Ru, Rh, Pd, An alloy to which a third element selected from Os, Mo, Nb, Ta, Hf, W, Ti, Zr, Y, La, Cr, and V is added has been proposed.
Patent Document 3 proposes a platinum iridium alloy in which Ir is alloyed by 20 wt% or less as a lead wire of a wide range type thermistor.
Patent Document 4 proposes a platinum iridium alloy composed of 75 to 86% Pt, 12 to 20% Ir, and 0.5 to 5% W as a discharge electrode of a low-consumption spark plug.
Japanese Patent Laid-Open No. 02-11734 JP 2003-96525 A JP 2005-294653 A Japanese translation of PCT publication No. 2002-520790

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.
The conventional platinum iridium alloy design has been aimed at increasing the strength or melting point by selecting an additive element. However, when used for a long time at a high temperature, grain growth inevitably occurs, the crystal grains become coarse, and grain boundary fracture may occur. For example, a binary platinum iridium alloy is recrystallized at approximately 600 ° C. or higher, and is coarsened until the crystal grain size exceeds 100 μm only by being held at a high temperature of 1000 ° C. or higher for several hours. Since such a platinum iridium alloy has a high initial performance, the probability of breaking with time increases, so it must be said that the reliability is insufficient for stable use over a long period of time.

  An object of the present invention is to provide a platinum iridium alloy in which crystal grains are not coarsened even when used at a high temperature for a long time in view of the above-described problems of the prior art.

The first invention is an alloy containing 0.1 to 2.0 mol% of an alkaline earth metal element and 4 to 50 mol% of Ir, and the balance being Pt and inevitable impurities , mainly comprising Pt and the alkaline earth metal element The platinum iridium alloy is characterized in that the precipitated particles of the second phase composed of are dispersed in the matrix phase, and the area ratio of the second phase in the cross section is 25% or less.
Here, the alkaline earth metal elements are Ca, Sr, and Ba. 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 a platinum iridium alloy cut, the cut surface is polished to a mirror surface, and when this polished surface is observed by an optical microscope, SEM or other observation means, it occupies a finite area included in the observation field, It is the area ratio of the 2nd phase which can be visually recognized.

The second invention relates to the first invention, and is characterized in that it contains 0.2 to 1.0 mol% of an alkaline earth metal element and 4 to 50 mol% of Ir, and consists of the balance Pt and inevitable impurities .

3rd invention is related to 1st or 2nd invention, 0.2 to 1.0 mol% of alkaline-earth metal elements and 8 to 12 mol% of Ir are comprised, The remainder Pt and an unavoidable impurity are comprised, It is characterized by the above-mentioned. .

The fourth invention relates to the first or second invention, wherein the alkaline earth metal element is 0.2 to 1.0 mol%, Ir is 4 to 50 mol%, and at least one element of Rh and Ni is 25 mol% or less. Including, remaining Pt and inevitable impurities .

A fifth invention relates to the first to fourth inventions, a step of preparing an ingot by blending a predetermined amount of metal raw material and dissolving in a non-oxidizing atmosphere, and forging the ingot hot or cold And a step of hot or cold processing while sandwiching a step of annealing and a step of annealing at 600 ° C. or higher for 1 minute or longer.
Here, for the dissolution, any melting means capable of dissolving the entire amount of the metal raw material in a non-oxidizing atmosphere such as in vacuum, in an inert gas, or in a reducing gas can be employed. Melting, vacuum melting, arc melting, plasma melting, electron beam melting and the like. For the annealing, any means capable of the above conditions can be adopted regardless of the atmosphere such as air, vacuum, inert gas, etc., for example, continuous furnace, batch type electric furnace, gas furnace, gas burner, etc. It is. The said process can employ | adopt well-known methods, such as swaging, rolling, groove rolling, and wire drawing.

The sixth invention relates to the fifth invention, wherein a predetermined amount of alkaline earth metal element is made of at least part of Pt or at least part of an alloy of Pt and Ir before the melting step. It arrange | positions so that it may contact in a container, The alloy of this alkaline-earth metal element and Pt or a platinum iridium alloy is formed by hold | maintaining in a non-oxidizing atmosphere of 600-1200 degreeC for 5 minutes or more, It is characterized by the above-mentioned. To do.
Here, the container may be any shape such as a dish, a cup, a cantilevered tube, and a flask as long as the content dissolved by heat treatment does not flow out. The container may be provided with a lid, and may be sealed by pressure bonding, welding or other methods. As a means for holding in a non-oxidizing atmosphere at 600 to 1200 ° C. for 5 minutes or longer, any means capable of the above conditions can be adopted in a non-oxidizing atmosphere such as vacuum, inert gas, reducing gas or the like. For example, a continuous furnace, a batch type electric furnace, a gas furnace, a gas burner, and the like. When the alkaline earth metal element is heat-treated in a container made using a part of the raw material in this way, an alloy or intermetallic compound of the alkaline earth metal and the component of the container is formed, and the alkaline earth metal alone is oxidized and oxidized. Evaporation can be suppressed.

7th invention relates to 1st-4th invention, It uses at 600 degreeC or more, It is characterized by the above-mentioned.
Here, the form of use of the platinum iridium alloy is not limited, and may be any form such as a wire, plate, strip, or tube, such as a crucible material, a heater wire, a sensor lead wire, or 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 iridium alloy that does not coarsen the crystal grains even when used at a high temperature for a long time, can do. Therefore, a platinum iridium alloy that can be used at a high temperature for a longer period of time can be provided. 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.
Furthermore, according to the manufacturing method of the present invention, evaporation of the alkaline earth metal element to be added can be effectively suppressed, and the quality of such excellent platinum iridium alloy products can be stabilized and the yield can be improved.

  The present invention can be applied to all fields where a conventional platinum iridium alloy is used, and is particularly effective when used as a heat resistant material. When applied to a crucible, a heater wire, a sensor lead wire, a discharge electrode of a spark plug, etc., it is durable. 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.

  Moreover, according to this invention, it is possible to manufacture with the manufacturing equipment which can be obtained normally, without requiring a special process. Therefore, one of the effects is that the manufacturing cost can be kept low.

The first invention is an alloy comprising 0.1 to 2.0 mol% of an alkaline earth metal element composed of any one of Ca, Sr, and Ba and 4 to 50 mol% of Ir, the balance being Pt and inevitable impurities. The platinum is characterized in that the second phase precipitated particles mainly composed of Pt and the alkaline earth metal element are dispersed in the parent phase, and the area ratio of the second phase in the cross section is 25% or less. Iridium alloy.
Here, when the content of the alkaline earth metal element is below 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 is deteriorated, and the second phase is easily cracked during processing. More preferably, it is good to set it as the range of 0.2-1.0 mol%. When the area ratio of the second phase exceeds 25%, it is an appearance of excessive precipitation, which deteriorates the oxidation resistance 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 second invention relates to the first invention, and is characterized in that it contains 0.2 to 1.0 mol% of an alkaline earth metal element and 4 to 50 mol% of Ir, and consists of the balance Pt and inevitable impurities .
This is a suitable form in the case of a platinum iridium alloy whose main component is a binary system.

3rd invention is related to 1st or 2nd invention, 0.2 to 1.0 mol% of alkaline-earth metal elements and 8 to 12 mol% of Ir are comprised, The remainder Pt and an unavoidable impurity are comprised, It is characterized by the above-mentioned. .
This is a suitable form when the main component is a binary platinum iridium alloy and Ir is in the above range.

The fourth invention relates to the first or second invention, wherein the alkaline earth metal element is 0.2 to 1.0 mol%, Ir is 4 to 50 mol%, and at least one element of Rh and Ni is 25 mol% or less. Including, remaining Pt and inevitable impurities .
This is a ternary or higher platinum iridium alloy, which is a preferred form when Ir is in the above range.

A fifth invention relates to the first to fourth inventions, a step of preparing an ingot by blending a predetermined amount of metal raw material and dissolving in a non-oxidizing atmosphere, and forging the ingot hot or cold And a step of hot or cold processing while sandwiching a step of annealing and a step of annealing at 600 ° C. or higher for 1 minute or longer.
The platinum iridium alloy of the present invention is easily work-hardened due to the presence of precipitated particles of the second phase. When excessive work hardening occurs during hot or cold working, it may cause cracking, and thus it is preferable to perform one or more annealing. When the annealing temperature or the annealing time is below the above range, there is no annealing effect, and processing becomes difficult. More preferably, the annealing is performed at 800 to 1200 ° C. for 10 to 60 minutes. After the annealing step, it can be processed again hot or cold.

The sixth invention relates to the fifth invention, wherein a predetermined amount of alkaline earth metal element is made of at least part of Pt or at least part of an alloy of Pt and Ir before the melting step. It arrange | positions so that it may contact in a container, The alloy of this alkaline-earth metal element and Pt or a platinum iridium alloy is formed by hold | maintaining in a non-oxidizing atmosphere of 600-1200 degreeC for 5 minutes or more, It is characterized by the above-mentioned. To do.
Here, if the material of the container is Pt or a platinum iridium alloy, the alkaline earth metal element reacts with the components of the container during the heat treatment to form an alloy or an intermetallic compound. This alloy or intermetallic compound has a composition containing a large amount of an alkaline earth metal element, but is less susceptible to oxidation than a simple alkaline earth metal element as a starting material, and can suppress the amount of evaporation during dissolution. Therefore, it is very suitable for controlling the alkaline earth metal element to a predetermined content. The material used for producing this container may be the total amount of Pt and Ir necessary for producing the ingot, or may be a part thereof.
When the heat treatment temperature is lower than the above range, the formation of an alloy between the alkaline earth metal element and the container component becomes insufficient, and when it exceeds the above range, the evaporation amount of the alkaline earth metal element increases. The furnace is contaminated and it becomes difficult to obtain a predetermined content. More preferably, it is 900-1100 degreeC. When the heat treatment time is less than the above range, the formation of an alloy between the alkaline earth metal element and the container component becomes insufficient. More preferably, it is 10 to 60 minutes.

7th invention relates to 1st-4th invention, It uses at 600 degreeC or more, It is characterized by the above-mentioned.
If it is a platinum iridium 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 iridium alloy in which the production process includes a step of 1000 ° C. or higher, or the use temperature is 800 ° C. or higher.

Tables 1 and 2 show the compositions and test results of the alloys of Examples and Comparative Examples.
“AE” in the table represents “alkaline earth metal element”.

(Melting of alloy)
Method A: A predetermined amount of an alkaline earth metal and a platinum iridium alloy were blended, and the whole amount was arc-melted.

  Method B: A predetermined amount of alkaline earth metal element was placed in a container made of a predetermined amount of platinum iridium alloy, heat treated in advance, and then arc melted. The container was a platinum iridium alloy block with a hole in the center of the upper surface, and was covered with another platinum iridium alloy. In the heat treatment, the container was placed in a tubular furnace, heated from room temperature to 1050 ° C. over about 1 hour in an Ar air flow of 200 ml per minute, held for 30 minutes, and then allowed to cool in the furnace.

  Method C: A predetermined amount of alkaline earth metal element was put in three containers made of a predetermined amount of a part of platinum iridium alloy and heat-treated in advance under the same conditions as described above. Subsequently, these and the remaining raw material were put into a zirconia crucible, melted in a high-frequency melting furnace substituted with argon, and cast into a mold.

  Method D: A predetermined amount of raw materials were blended, and the entire amount was put into a zirconia crucible, melted in a high-frequency melting furnace substituted with argon, and cast into a mold.

(Alloy processing)
The obtained ingot was annealed at 1200 ° C. for 1 hour, and was processed by cold rolling to a thickness of 0.5 mm. Those in which cracking was observed during the processing were subjected to intermediate annealing at 1200 ° C. for 1 hour.
By the above operation, alloys having the compositions shown in Tables 1 and 2 were obtained.

(test)
In the test, the processed material was used after annealing at 1500 ° C. for 1 hour.
The area ratio shown in the table is the area ratio of the second phase measured by cross-sectional observation.
The grain size shown in the table is an average grain size measured by the quadrature method defined in JIS H 0501 (Copper grain size test method) after etching the alloy cross section.
The hardness shown in the table is the Vickers hardness of the alloy cross section.

(Test results)
A cross section of the example alloy is shown in FIG.
When analyzed by EPMA and XRD, the second phase precipitated in Examples and Comparative Examples was identified as an intermetallic compound mainly composed of Pt and an alkaline earth metal element.

  Examples 1 to 7 and Comparative Examples 1 to 5 are alloys obtained by adding various alkaline earth metal elements to the platinum iridium alloy of Comparative Example 7. If the content of the alkaline earth metal element is in the range of 0.1 to 2.0 mol% and the area ratio of the second phase is 25% or less, the particle size is 100 μm even when annealed at high temperature. It was found that it was maintained as fine as below. Further, it was found that these example alloys have high Vickers hardness and improved strength. When the content of the alkaline earth metal element was less than 0.1 mol%, the area ratio of the second phase was almost zero and the particle size was coarse (Comparative Example 2 and Comparative Example 3). In addition, when the content of the alkaline earth metal element exceeds 2.0 mol%, the second phase is excessively precipitated and becomes brittle, and cracks are generated on the entire surface even after intermediate annealing (Comparative Example 4 and Comparative Example). 5). Other examples and comparative examples could be processed without any particular problems.

  Even when the Ir content was changed, it was confirmed that by adding an alkaline earth metal element, coarsening of crystal grains was suppressed and the strength was improved (Examples 8 and 9).

  By adding an alkaline earth metal element to the platinum iridium alloy containing the third alloy element in Pt and Ir, the precipitated particles of the second phase are present, the coarsening of the crystal grains is suppressed, and the strength is increased. It was confirmed to improve.

  From the above results, the effects of the present invention became clear.

It is a figure which shows the cross section of an Example alloy.

Claims (7)

  An alloy containing 0.1 to 2.0 mol% of an alkaline earth metal element composed of any one of Ca, Sr, and Ba and 4 to 50 mol% of Ir, the balance being Pt and inevitable impurities, mainly comprising Pt and the alkali A platinum iridium alloy comprising precipitated particles of a second phase composed of an earth metal element dispersed in a matrix phase, and an area ratio of the second phase in a cross section being 25% or less.   2. The platinum iridium alloy according to claim 1, comprising 0.2 to 1.0 mol% of the alkaline earth metal element and 4 to 50 mol% of Ir, the balance being Pt and inevitable impurities.   3. The platinum iridium alloy according to claim 1, wherein the platinum iridium alloy contains 0.2 to 1.0 mol% of the alkaline earth metal element and 8 to 12 mol% of Ir, and consists of the balance Pt and inevitable impurities.   The alkaline earth metal element is 0.2 to 1.0 mol%, Ir is 4 to 50 mol%, at least one element of Rh and Ni is contained in an amount of 25 mol% or less, and is composed of the balance Pt and inevitable impurities. The platinum iridium alloy according to claim 1 or 2. A step of preparing an ingot by blending a predetermined amount of a metal raw material and dissolving in a non-oxidizing atmosphere, a step of forging the ingot hot or cold, and a step of annealing at 600 ° C. or higher for 1 minute or longer. The method for producing a platinum iridium alloy according to any one of claims 1 to 4 , comprising a step of processing hot or cold while sandwiching.   Prior to the melting step, a predetermined amount of alkaline earth metal element is placed in contact with a predetermined amount of at least part of Pt or at least part of a container made of an alloy of Pt and Ir. The manufacturing method according to claim 5, wherein an alloy of the alkaline earth metal element and Pt or a platinum iridium alloy is formed by holding in a non-oxidizing atmosphere at 1200 ° C for 5 minutes or more. It uses at 600 degreeC or more, The platinum iridium alloy of any one of Claims 1-4 characterized by the above-mentioned.