JPS62208527A - Manufacture of end cap for magnetron - Google Patents

Abstract

PURPOSE:To improve dimensional accuracy and processing yield, by performing cold forging on a sintered material made of molybdenum by powder metallurgy, to give the material a final form. CONSTITUTION:A powder of molybdenum in a prescribed grain size is molded under pressure in a metal mold so that a compared powder piece in a prescribed form is made. The piece is sintered at a temperature of 2,000 deg.C or more in a steam flow or the like so that a sintered material 5 for an end cap 1 is obtained nearly in final form and dimensions. The dimensions of the sintered material 5 are slightly larger than those of the end cap, and are not very accurate because of a distortion or the like caused in the sintering. The sintered material 5 is then subjected to cold forging in a prescribed metal mold so that the end cap 1 is obtained. The cold forging is called 'sizing' and performed by using the metal mold comprising a die having an end cap formation opening and an upper and a lower punches, and a hydraulic or pneumatic press or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing an end hat for a magnetron used in a microwave oven or the like.

[Prior Art] An end hat for a magnetron (hereinafter simply referred to as an end hat, S')'l is brazed to the tip of a round bar-shaped support member 2 that acts as a lead rod, as shown in Fig. 1, and is used for conducting electricity. It is used to support the coil 3,
Molybdenum is generally used as the material.

[Problems to be solved by the invention] Conventional molybdenum end hats were manufactured by cutting a round bar, resulting in high manufacturing costs.
Material yield was also low. In order to improve this, attempts have been made to produce a sintered body in a predetermined shape using a powder metallurgy method, but there is a problem in that it is difficult to obtain the desired dimensional accuracy with the sintered body as it is.

[Means for Solving the Problems] In order to solve the above problems, the present invention employs the following configuration.

That is, the method for manufacturing an end hat for a magnetron according to the present invention is characterized by cold forging a molybdenum sintered body material manufactured by a powder metallurgy method to obtain an end hat in the final shape and size.

To explain this in more detail based on an example, first, a sintered material made of molybdenum is manufactured using a known powder metallurgy technique. That is, molybdenum metal powder of a predetermined particle size is pressure-molded in a mold to form a compact into a predetermined shape, and this compact is sintered, for example, at a temperature of 2000° C. or higher in a hydrogen stream. As a result, an end hat sintered material 5 having approximate R-line shape dimensions as shown in Fig. 2 is obtained, but this material is slightly larger than the final dimension and has poor dimensional accuracy due to distortions generated during sintering. It's not that good.

Next, this sintered material is subjected to cold forging using a predetermined mold to obtain an end hat 1 as illustrated in FIG. 3. This cold forging is called sizing, and is carried out using a mold consisting of a die having an end hat forming space and upper and lower punches, and a press machine operated by hydraulic or pneumatic pressure. It is preferable to perform forging using a suitable lubricant, and it is preferable to apply pressure from both the upper and lower sides. The press machine requires a high-pressure knockout function to take out the end hat after molding.

The above lubricant may be carbon-based or molybdenum disulfide (
It is preferable to use a powdered lubricant based on MoS 2>.

In order to improve the adhesion to the sintered body material 5, it is preferable to add a small amount of liquid such as lubricating oil to the powdered lubricant.

Although the shape of the end hat shown in FIG. 3 is slightly different from that shown in FIG. 1, it is possible to manufacture end hats of various shapes and sizes using this method.

FIG. 4 schematically shows an example of a forging device used in carrying out the present invention. This forging device O is equipped with an upper pressure drive piston 11 and a lower pressure drive piston 12,
5 is mounted on the table 13. Further, the upper punch 16 is attached to the upper piston 11, and the lower punch 17 is attached to the lower piston 12. The lower bunch 17 is formed by combining a cylindrical core portion 17a and a cylindrical outer peripheral portion 17b. Note that the die 15 made of cemented carbide and the upper punch 16 made of tool steel are connected to heaters 19 and 16, respectively.
It is heated by 20. The heating temperature of the mold is preferably 50 to 400'C, and 150 to 400'C.
It is more preferable to set the temperature to 300°C. If the heating temperature is too low, cracks will easily occur in the molded product, and if it is too high, the fit between the punch and die will be distorted due to the difference in materials. Similarly, it is preferable to preheat the sintered material 5 that will become the workpiece to 50 to 4QQ°C, more preferably 200 to 300°C.

Since the preheating temperature of these molds and workpieces is lower than the recrystallization temperature of molybdenum, this forging falls within the range of cold forging. Traditionally, cold forging of molybdenum has not been put to practical use because it causes cracks and cracks in the workpiece.
As described above, by selecting an appropriate preheating temperature and lubricating oil, it is possible to put it into practical use. It should be noted that this cold forging can be carried out automatically and efficiently, making it suitable for actual production.

Example] A molybdenum end hat sintered body material as shown in FIG. 2 was manufactured by a known powder metallurgy method.

Place the sintered material (several pieces) and a carbon-based powder lubricant (pre-moistened with a small amount of machine oil) into a ball mill pot, and rotate the pot for 30 minutes to 4 hours. A lubricant was applied to the entire surface of the sintered material. Thereafter, forging was carried out using a forging device and a mold as shown in FIG. 4 at a mold temperature of 200° C. and a workpiece temperature of 200° C. to obtain an end hat 1 as shown in FIG. 3.

Regarding the dimensions of 25 samples before and after forging, the average value of the outer diameter A before forging is 9.896 mm, the maximum value is 9.980 m, the minimum value is 9.820 m, and the standard deviation (σ) is 0. The total length after forging was 10.000m. In addition, the inner diameter B has an average value of 5.104mm before forging, a maximum value of 5.180m, a minimum value of 5.060rMt1 standard Q-deviation (σ) of 0.027an
And the total number of @Zoki's was 5.000mm.

In addition, the average value of the inner height C before forging is 3.112 m1
Maximum value 3.200m, minimum value 3.040m, standard deviation 0
．． 040 order, and on the other hand, the average value after forging is 2.99
9, maximum value 3.000m, minimum value 2.990m, standard deviation 0,003. Met. Roughly speaking, the outer height D is
The average value before forging is 5.108, the maximum value is 5.180m,
Marketed with a minimum value of 5.060 shoes and a standard deviation of 0.029 shoes.The average value after forging is 4.999s, and the maximum R value is 5.0OOs.
, the minimum value was 4.980 m and the standard deviation was 0.005 m. When the end hat is used, a lead rod is fitted and soldered to the end hat, so strict dimensional accuracy is required, and by implementing the present invention, such strict requirements can be fully satisfied.

Next, Vickers hardness and specific gravity are the hardness before forging (HV)
The average value of specific gravity was 149, the average value after forging was 183, the average value of specific gravity before forging was 49, and the average value after forging was 9.83. Since the lead rod is sometimes spot welded to the end hat, it must have a certain degree of strength, but one having the above-mentioned hardness and specific gravity after forging can sufficiently withstand this requirement.

In general, the results of investigating the surface roughness show that the surface before forging has a matte finish and has a rough feel, but the surface after forging is smooth and has a metallic luster. Koita Research Institute! l!
When the surface roughness (μm) before and after forging was measured using a 5P-11 type surface roughness measuring device, the maximum roughness (μm) before forging was
ax = 13.25, ten point average roughness RZ = 9.25
, center line average roughness Ra=0.77, and after forging Rmax=2.01RZ=1.0. Ra=0.
It was 11. In order to stabilize the direction of electromagnetic waves emitted from the thoriated tungsten coil, the surface of the end hat must be smooth, but as mentioned above, the surface roughness of the end hat after forging must be extremely good and sufficient. It satisfies that requirement.

Note that the crystal structure before forging had coarse crystals typical of sintered ingots, whereas the crystal structure after fR forging was sufficiently refined.

[Effects of the Invention] As is clear from the above description, the manufacturing method of the present invention makes it possible to manufacture end hats with high dimensional accuracy and processing yield, as well as good strength and other properties, on a commercial scale. became.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the end hat in use, FIG. 2 is a sectional view of the sintered material, FIG. 3 is a sectional view of the end hat, and FIG. 4 is an explanatory diagram of the forging device.

Claims (1)

[Claims] (1) A method for producing an end hat for a magnetron, which is characterized by cold forging a molybdenum sintered material produced by powder metallurgy to obtain an end hat in the final shape and size.