KR100875303B1 - Manufacturing Method of Reinforced Platinum Using Discharge Plasma Sintering - Google Patents

Abstract

The present invention relates to a method of manufacturing reinforced platinum using a new spark plasma sintering method (SPS; Spark Plasma Sintering), which overcomes the disadvantages that the manufacturing process is complicated, expensive, and takes a long time. It is designed to. To this end, after the preparation of the reinforcement platinum powder of the desired composition, degassing by high temperature heat treatment, filling the mold with powder, and achieving a good sintering density in a short time using the discharge plasma sintering method proposed as a new method of sintering. To produce a strengthened platinum. As described above, in the present invention, by using the discharge plasma sintering method, which is a new sintering method, it is possible to manufacture the strengthened platinum having a much shorter manufacturing process and manufacturing cost than the existing process.

Description

Method for producing reinforced platinum using discharge plasma sintering method {Method of intensification platinum using a spark plasma sintering}

1 is an overall flowchart of the production of reinforced platinum using the discharge plasma sintering method of the present invention.

2 is an enlarged view of a metal cross-sectional structure after cold rolling and heat treatment.

The present invention is used as a device that is exposed to high temperatures for a long time, such as devices in the glass-related industries, and reinforcement using a new sintering method for a reinforced platinum material that improves mechanical properties at high temperatures such as high temperature strength and creep resistance of the platinum material. The present invention relates to a method for producing platinum, and in particular, to develop a reinforced platinum material by a discharge plasma sintering method.

The discharge plasma sintering method according to the present invention is a method of applying a direct current pulse current in a direction parallel to the pressing direction while sintering the powder in one axis, and injecting pressure, a low voltage and a large current into the gap between the powder particles, It is a sintering method that applies high energy of plasma generated by sparks in an instant to electric field diffusion, thermal diffusion, and the like. Compared to the conventional hot press method, since the sintering temperature is 200 to 500 ° C lower and the sintering can be completed in a short time including the temperature raising and holding time, the power consumption is greatly reduced, the handling is simple, and the running Inexpensive, skilled in the sintering technique is not required, and can be applied to materials that are difficult to process at high temperatures and sintering materials.

In general, in order to improve the mechanical properties of platinum, alloying using gold (Au), rhodium (Rh), etc., as a reinforcing element is carried out, but there are disadvantages in that there is a possibility of coloring of glass and high cost of alloying elements depending on alloying components. .

In recent years, dispersion-reinforced platinum dispersed by using oxide has been developed and used. Such oxide-disperse-reinforced platinum has excellent creep characteristics due to its low grain growth and strain even after long-term storage at high temperatures. It is reported. Therefore, the oxide dispersion-reinforced platinum is low in cost compared with the platinum strengthened by the existing alloy, and has the advantage of not only having a long life at high temperature but also thinning.

Existing reinforcement platinum production method, after manufacturing the reinforcement platinum powder by the wet method, the molded body is produced by primary molding and cold isotropic compression molding (CIP), etc., and then sintered, hot worked and cold rolled Form a reinforced platinum material. In the dry process, the ingot is melted and cast, then powdered by atomizing or arc spraying, pulverized, degassed, oxidized, hot pressed, and repeated. Heat treatment and the like are carried out, and finally, a reinforced platinum material is produced by hot working and cold working.

However, when manufacturing the strengthened platinum by the above-described methods, the manufacturing method of the wet method has a short time or a high temperature characteristic is lower than the dry method, the high temperature characteristics in the dry method is excellent, but due to complex processes In addition to the disadvantages that the manufacturing cost increases, manufacturing time is a long time, the process such as hot processing has a disadvantage that the working environment is also poor because the operation (Handling) of the product is more than 1200 ℃.

As described above, in order to manufacture reinforced platinum by known methods, complex processes such as powder making, degassing, sintering, hot working and cold working are required, as well as high cost and long manufacturing time. Required.

However, the core configuration of the present invention is to produce a high-density reinforced platinum material by the discharge plasma sintering method using the final powder subjected to the degassing process after manufacturing the powder by wet and dry method, according to the process conditions hot press and repeated The heat treatment process is excluded, and the operation at high temperature is omitted, and thus the handling is easy.

In order to solve the above problems, reinforcement platinum production method using the discharge plasma sintering method of the present invention comprises the steps of preparing a reinforced platinum powder of the desired composition, the step of degassing the powder produced, and after the powder is filled in the mold discharge The method comprises the steps of obtaining a reinforced platinum material close to the theoretical weight by using plasma sintering, and finally, performing cold rolling and heat treatment. Reinforced platinum produced by the above method, it is possible to manufacture a reinforced platinum material close to the theoretical weight in a short time, excellent high temperature characteristics, excellent creep characteristics, blister occurs at 1400 ℃ temperature used in the glass industry It is to provide a method for producing a non-reinforced platinum material.

Hereinafter, the process of this invention is demonstrated in detail with reference to FIG.

1 is an overall flowchart of the production of reinforced platinum using the discharge plasma sintering method of the present invention.

Firstly to prepare a strengthened platinum powder of the desired composition (S1).

Powdered platinum powder is available in both wet and dry methods, but when it is manufactured by wet method, the powder size is fine, but it is difficult to precisely control the composition of the target, and there is adsorption gas, so post-treatment is required. When manufactured by the dry method, it is possible to precisely control the desired purpose, but powdering, oxidation treatment, grinding and degassing processes are required.

Dispersion-enhancing materials used in reinforced platinum are oxides such as zirconium (Zr), samarium (Sm), yttrium (Y), europium (Eu), and hafnium (Hf) .In the case of the wet method, it is used during powder manufacturing. It can be provided in the form of an oxide by a solvent, and in the dry method, it is possible to provide an oxide by heat treatment in the air at high temperature, which is preferred to platinum when contacted with oxygen because these reinforcement elements have affinity for oxygen in comparison with platinum material. This is due to the property of forming oxides.

The amount of reinforcing elements presented above is suggested in the form of oxide from 0.02wt% to 5wt%. This means that an oxide dispersion strengthening effect cannot be obtained at less than 0.02 wt%, and a concentration exceeding 5 wt% has a disadvantage in that dispersion strengthening by residual dispersed particles is increased and workability is also decreased.

Finally, the size of the powder to be used is preferably in the range of 0.1 ~ 20㎛, which is easy to aggregate when less than 0.1㎛ and more than 20㎛ may lead to a deterioration of the final high temperature creep properties deteriorate the oxide dispersibility. Recrystallization proceeds by the final heat treatment, which may result in non-uniform recrystallization.

The prepared powder is subjected to degassing through vacuum heat treatment (S2).

The powder produced by the wet method and the dry method has to be degassed, since the adsorption gas remains. The vacuum heat treatment temperature is appropriately in the range of 2 to 5 hours at 1300 ° C. to 1500 ° C., which generates pores due to the adsorption gas. This is because the temperature and time can be extremely suppressed.

In the case of the powder produced by the dry method, oxidation is required because the form of the powder is Pt-Zr by degassing after dissolution.

The degassed powder is filled into a mold of a desired size, and then discharge plasma sintered after setting in a chamber (S3).

The amount of filling in the mold is calculated according to the final thickness, and then the charging amount is calculated using the theoretical weight. Before filling the powder, the reaction between the mold and the powder occurs due to the increase of the temperature due to the pressurization during the sintering and the application of a high current, and the expensive mold is broken when the mold and the sintered body are separated after the end of the sintering. Carbon sheets should be used to avoid contact between powder and mold. Even when a carbon sheet is used, a reaction may occur between the strengthened platinum and the mold due to the high pressure and temperature rise. In this case, the super high temperature BN may be used for the upper and lower punches in contact with the powder to suppress the reaction.

A powder-filled mold set is set in the discharge plasma sintering apparatus chamber, and discharge plasma sintering is carried out while gradually applying a DC pulse while pressing under reduced pressure. The reduced pressure is preferably 10 Pa or less, in order to protect the carbon mold due to the high temperature rise of 1000 ° C. or more during the reinforcement platinum discharge plasma sintering. Atmosphere control is possible in addition to the vacuum atmosphere, argon atmosphere or nitrogen atmosphere.

The pressure applied to the powder is appropriately 10 MPa to 50 MPa, which means that when the pressure is 10 MPa or less, a high current may be input for sintering, resulting in a high temperature rise. If the pressure exceeds 50 MPa, the sintering temperature may be lowered and the sintering may not sufficiently occur. And the carbon mold may be broken.

When applying the current, it is desirable to increase the same width for a predetermined time, which makes it difficult to control the temperature when the rapid current is applied, and the accurate sintering temperature measurement is impossible.

During discharge plasma sintering, it is important not to cool immediately at the end of sintering, but to maintain for several tens of minutes, in order to facilitate the cold rolling and recrystallization to proceed to the later process by growing the grains.

After discharge plasma sintering, the furnace is cooled in a vacuum atmosphere to a temperature of 200 ° C. or lower to protect the carbon mold and the punch used in the chamber.

Since the carbon sheet is fixed to the discharge plasma sintered specimen (S4). In case of carbon sheet, it is removed by oxidative combustion during heat treatment at the temperature of more than 1000 ℃ in the air. The proper heat treatment temperature and time is within 1 hour at 1000 ~ 1400 ℃. When the heat treatment temperature is less than 1000 ℃ it may take a long time to remove the carbon sheet, when the temperature is more than 1400 ℃ crystal grains are likely to occur.

Cold rolling is performed on the reinforced platinum sintered body from which the carbon sheet is removed (S5). The purpose of introducing the processing structure is to prioritize the homogenization of the tissue by recrystallization through post-heat treatment, and to be limited by the size, which is the biggest disadvantage of the discharge plasma sintering when manufactured by the discharge plasma sintering. Since the size is limited to φ = 300, there is also an object to increase the size through cold rolling. The reduction ratio is suitably 50% or more so that recrystallization may occur through subsequent heat treatment.

The cold-rolled material is heat-treated in the air (S6), which, as mentioned above, aims at recrystallization for homogenization of cold-rolled tissue. Heat treatment temperature is suitable for 1 hour at 1200 ~ 1400 ℃, if the temperature is lower than 1200 ℃ difficult to recrystallization, coarse crystal may occur when the temperature is above 1400 ℃.

EXAMPLE

ZrO ₂ is used as the dispersion strengthening material of the reinforced platinum powder, and the target composition is prepared with Pt- 0.3% ZrO ₂ . To using the 3㎜, the theoretical specific gravity and the amount of 4-inch-like product after the discharge plasma sintering diameter, desired thickness prepared preparing a 520.00g calculated approximately, which contains the platinum powder and 518.44g zirconium oxide powder ZrO ₂ 1.56g mixed. Reinforced platinum powder prepared by the wet method has a particle size analysis, the central particle size is 1.5㎛, showing a range of 1 ~ 10㎛.

The prepared powder is widely spread in a non-consolidated state for degassing treatment, and then vacuumed under a vacuum of 0.5 Pa or less at a temperature rising rate of 10 ° C./min from 1 ° C. to 1300 ° C., and maintained at 1300 ° C. for 2 hours. Heat treatment is performed.

The degassed powder is filled into a 4 inch circular carbon mold for discharge plasma sintering. In order to avoid contact between the powder and the mold, a carbon sheet is used in advance in the mold. After the filling is completed, the mold set is matched with the upper and lower electrodes in the chamber of the discharge plasma sintering apparatus, and then discharge plasma sintering is performed.

In the discharge plasma sintering, the initial vacuum was reduced to 5 Pa or less, and then pressurized to 10 MPa and the current was adjusted to maintain a temperature increase rate of 100 ° C / min.

After the discharge plasma sintering is completed, the furnace is cooled in a vacuum atmosphere.

The sintered sintered body is subjected to high temperature heat treatment at 1200 ℃ for 1 hour in air atmosphere to remove carbon sheet, and the heat treated specimen is cold rolled to make final thickness 1mm, and the final heat treatment is performed at 1200 ℃ in air. After the heat treatment for 1 hour to prepare a reinforced platinum material.

As a result of measuring the specific gravity after removing the carbon sheet, the specific gravity was 21.159, and the relative specific gravity was over 99%, and it was possible to manufacture reinforced platinum close to the theoretical specific gravity in a short time using the new sintering method. In addition, the microstructure was observed to determine the recrystallization of the specimen subjected to heat treatment after cold working, and the creep test was performed at 1400 ° C. to evaluate the presence of blisters and the high temperature mechanical properties after heat treatment at 1400 ° C. for 1 hour.

As a result of tissue observation, uniform recrystallized grains were observed as shown in FIG. 2 and blisters were not observed.

The results of the creep test are shown in Table 1, which shows that the creep resistance is almost similar to that of the previously reported reinforced platinum. Therefore, from all these results, it can be seen that the strengthened platinum produced using the discharge plasma sintering method, which is a new sintering method, was produced very soundly.

Blister generation after heat treatment at 1400 ℃ for 1 hour Creep strength, MPa (at 1400 ℃, 200 hours) Example none 10 Existing reporting example (ZGS-Pt) none 9 Existing reporting example (GTH-Pt) none 10.5

In the present invention, after the preparation of the reinforcement platinum powder of the target composition is subjected to degassing treatment by high temperature heat treatment, the powder is filled into the mold, and using a discharge plasma sintering method proposed as a new method of the sintering method has a good sintering density in a short time Reinforced platinum can be prepared.

In addition, in the present invention, by using the discharge plasma sintering method, which is a new sintering method, it is possible to manufacture a reinforced platinum material having a much shorter manufacturing process and manufacturing cost than the existing process.

Claims (7)

In the method of manufacturing the reinforced platinum using the discharge plasma sintering method, Preparing a strengthened platinum powder in which oxides of zirconium (Zr), samarium (Sm), yttrium (Y), europium (Eu), or hafnium (Hf) are dispersed by a wet method and a dry method, Degassing the prepared platinum powder at a temperature of 1300 ℃ to 1500 ℃ in a vacuum atmosphere, and After the degassed powder is filled in the mold and set in the chamber to reduce the pressure, and then pressurizing and applying a current to sinter the discharge plasma, and then the furnace cooling; Removing the carbon sheet by quenching the sintered body; Giving a processing structure to the sintered body from which the carbon sheet is removed through cold working; Method of producing a strengthened platinum, characterized in that consisting of a heat treatment step for recrystallizing the microstructure of the cold-processed reinforced platinum. The method of claim 1, The amount of the zirconium (Zr), samarium (Sm), yttrium (Y), europium (Eu), or hafnium (Hf) oxide is 0.02wt% ~ 5wt% manufacturing method of the reinforced platinum. The method of claim 1, Method for producing a strengthened platinum, characterized in that for producing the powder of the strengthened platinum powder to produce a particle size of 0.1 ~ 20㎛. The method of claim 1, The pressure applied during the discharge plasma sintering method of the strengthened platinum, characterized in that 10 ~ 50MPa. delete The method of claim 1, Process for producing a strengthened platinum, characterized in that the processing amount in the cold processing, the reduction ratio is processed to 60% or more. delete

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