JPS60200901A - Molding method of powder by cold hydrostatic press - Google Patents

Abstract

PURPOSE:To simplify the stage for molding a green compact in the stage of molding the green compact by a hydrostatic pressurization method by molding preliminarily raw material powder by a heat shrinkable tube then molding the powder by a cold hydrostatic press. CONSTITUTION:A heat shrinkable tube 6 made of crosslinked PE is fitted onto flanges 2 supported by a mandrel 1 and raw material powder 4 for a green compact is packed therein. The entire outside circumference of the tube 6 is then heated to 110-200 deg.C by a heater 10. The tube 6 is contracted by the diametral shrinkage effect generated by the heat thereof and molds preliminarily the powder 4 in the tube. The powder molded preliminarily in the above-mentioned way is put into a cold hydrostatic press device by which the powder is hydrostatically pressed and molded to an intended molding. The molding having excellent shape accuracy is easily molded by the press without requiring the stage for preliminary molding of the powder which is required in the prior art.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to an improvement in a method for molding a green compact by an isostatic pressing method.

[Prior art and its problems]

A method of producing a green compact by applying hydrostatic pressure is known as a so-called hydrostatic pressing method or a rubber press method, and is well known. In this powder molding method, as shown in Figure 1 (a), a bag (3) made of an elastic material such as rubber is placed between upper and lower flanges (2) supported by a core metal (1). : A method in which the powder to be molded (4) is packed into the molded powder, and this is press-molded by hydrostatic pressure as shown in (b) to form a green compact;
After preforming the powder (4) with a press as shown in (a) of E), it is placed in a rubber bag (3) as shown in Figure 1).
) and deaerated the bag (3) to form the preformed powder (4
), and as shown in Figure (c), this is pressure-molded using hydrostatic pressure to form a green compact. Note that (5) in the figure indicates a molded product. However, the previous method has the disadvantage that the rubber bag is deformed by the static pressure during powder feeding, making the shape of the molded product unstable, and in case 1c, wrinkles or unevenness occur on the surface. The latter method also requires a powder preforming step using a press.

This forces an increase in costs.

[Purpose of the invention]

The present invention was made to eliminate the drawbacks of the conventional methods described above, and provides a simple and accurate molding method that employs a preforming process using a heat-shrinkable tube.

[Structure of the invention]

This invention is characterized by filling a heat-shrinkable tube with powder and heating it to perform preforming by shrinking the tube, or by performing preforming by applying light pressure at the same time as heating, and then cooling it. All pressure forming is done using an isostatic press.

〔Example〕

Hereinafter, embodiments of the present invention will be explained based on FIGS. 2 and 3, which illustrate examples.

In Figures 2 and 3, (6) is a heat-shrinkable tube made of, for example, cross-linked polyethylene (shrinkage: 50 to 70 inches), which is attached to the outer periphery of a flange (2) supported by a core bar (1). It is fitted, and the powder to be molded (4) is packed inside.

The procedure for assembling the flange (2) and core metal (1) and coating the heat-shrinkable tube (6) is shown in Figure 3.
, as shown in the same figure (a), first remove the lower flange (2).
At the lower end of the tube (6), heat the area around this part to shrink it, then (b) as shown in K, stand up the core bar (1) and fill it with powder (4). Then, after joining the upper flange (2) to the top end of the core bar (1), the outer periphery of the tube (6) in contact with the upper flange (2) is heated and contracted.Depending on the shape of the product, Core metal (
1) can also be omitted.

Once the powder (4) has been encapsulated in the photon state as described above, the entire outer periphery of the tube (6) is heated at a temperature of 110 to 200°C. The powder (4) is preformed by radial action, and in the method shown in Fig. 3, the tube (6) containing the powder (4) is placed in a mold (c) as shown in Fig. 3(c).
a) and the pusher (8), heat it, lower the pusher (8), apply light pressure, and prepare the preform (9) to obtain a molded product of the desired shape. Following the first step of preforming in this way,
The q42 step, that is, pressure forming by cold isostatic pressing, is exactly the same as conventional means, and p, for example, 1000 to 1500 p.
Pressurize at a pressure of Kyf/cJ. In addition, as a heating means applied in the above preforming, a device (10) using an air heater or a gas burner is used, and in the method shown in FIG. The mold (7) and pusher (8) are selected that are suitable for obtaining the powder.Moreover, this method requires relatively rough molding of irregularly shaped products and improvement of the density of the powder. In addition, in Figures 2 and 3, (5) indicates a molded product.

〔Effect of the invention〕

As described above, according to this publication 8Arc, a heat-shrinkable tube is used to preform the powder by its heat-shrinking action, and the tube shrinks equally and sensitively over its entire area, resulting in good moldability. There are no wrinkles due to shrinkage of the powder, the shape of the molded product is stable, and the surface finish is smooth and beautiful. Note that by applying light pressure to the heating, the density of the powder can be improved, and the effects are doubled, such as the ability to accurately preform comparatively complex deformed products.

[Brief explanation of drawings]

FIG. 1 (A) (B) Vi explanatory diagram showing the conventional molding method,
FIGS. 2 and 3 are explanatory diagrams showing an embodiment of the present invention. (1) is core metal, (2) is flange, (4) is powder, (6
] is a heat-absorbing 1.1d tube, (7) is a mold, (8) is a pusher, and σO1 is a heating device. (r Fig. 2 7 Fig. 3

Claims (1)

[Claims] (1) Fill a heat-shrinkable tube with powder and heat it to perform preforming by shrinking the tube, or perform preforming by applying light pressure at the same time as heating, and then apply cold isostatic pressure. A powder forming method using a cold hydraulic press, which is characterized by pressure forming using a press.