KR20010045000A - Control method of partial density from parts sintered forming - Google Patents

Abstract

PURPOSE: A method for controlling the partial density during forming of a sintered component is provided to manufacture a product in which the area surrounding a hole has a partially increased density after forming by improving the forming process so that the powder is pressed in the state that the powder surrounding a core rod is increased. CONSTITUTION: In a sintering method comprising blending process of mixing powder to be sintered; forming process forming a shape of a product, wherein a powder distribution chamber (53) is formed so that powder (52) to be formed in a lower die (51) is supplied for formation of the product, a core rod (55) is projected to the upper direction so that a hole of the product formed is formed at the lower side of the lower die, and an upper die is installed at the upper side of the lower die for pressing and forming powder (52) distributed into a powder distribution chamber by descending of the upper die; sintering process of providing properties by heating the formed body formed in the forming process; restoring process of improving the overall accuracy by correcting the deformation which can be generated in the sintering process; and post-treating process of passing through heat treatment, finishing and coating for improving quality and durability of the product, the method comprises the steps of lowering the elevation of the upper surface (56) of the core rod than the powder distribution surface (57) of the powder distributed into the powder distribution chamber; and ascending the core rod during pressing of the distributed powder by lowering the upper die so that powder distributed on the upper side of the core rod is supplied to the surrounding area of the core rod, thereby removing drop of the density surrounding the core rod.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a partial density of a sintered component,

The present invention relates to a method of controlling the partial density of a powder during sintered component molding, and more particularly, to a method for controlling a partial density of a sintered body by improving the density of the machine parts formed by squeezing metal powders, will be.

Compared with conventional techniques such as casting and roll forming, the sintering method using metal powder is a method widely used in recent years due to its simplicity of processing, improvement of precision, weight and cost reduction.

Such a sintering process is a mixing process in which a solid lubricant is added and mixed to facilitate the shape-imparting of various metal powders such as iron powder (Fe), copper powder (Cu), and stainless powder, 10);

A molding step (20) of forming a shape by pressing the mixed powder into a mold of desired shape and applying pressure thereto;

A sintering process (30) for imparting physical properties by applying heat such that chemical bonds are formed by atomic diffusion between powder particles formed in the shaping step (20);

A shaping step (40) for repressing the sintering step (30) so as to improve the overall precision by correcting deformation due to dimensional deformation, warping or the like;

A post-treatment step (50) is carried out through a process such as heat treatment, finishing and coating treatment for improving the quality and durability of the product after the shaping process.

When various kinds of industrial parts are completed by the sintering method as described above, high precision can be obtained, and not only the quality can be improved, but also the overall manufacturing cost can be reduced.

However, since holes and uneven portions around the holes of a product to be formed are liable to have a density lower than that of the surrounding, a phenomenon such as a crack or a part of the product occurs after completion or operation.

3, the feed rod 2 is formed in the lower mold 1 to receive the powder 3 and the core rod 4 forms the hole of the product when the upper mold is pressed.

That is, the powder in the core rod portion moves to the upper surface of the core rod while the powder is compressed by the upper die, and the density of the core rod portion after molding is relatively lower than the surrounding portion. The amount of the portion pressed by the step (distance) to the lower end becomes small, so that the partial density around the core rod becomes relatively low.

Accordingly, it is an object of the present invention to overcome the above-mentioned problems, and it is an object of the present invention to improve the molding process so that the top surface position of the core rod is set to be lower than the level of the surface of the core rod, The present invention is intended to provide a product which can reduce the deviation of partial density after molding by making it possible to produce a product which is squeezed in a state where the powder is increased around the core rod.

1 is a block diagram showing a sintering molding process for explaining the present invention.

Fig. 2 is a cross-sectional view of a mold showing a partial density control relationship of powder during sintered component molding according to the technique of the present invention. Fig.

Fig. 3 is a cross-sectional view of a mold for molding a sintered part to which the prior art is applied. Fig.

Description of the symbols used in the main parts of the drawings

20; Molding process

51; Lower mold

52; powder

53; Rapid loss

55; Core rod

60; incline

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a sintering molding process for explaining the present invention, and FIG. 2 is a cross-sectional view of a mold showing the control of the partial density of the powder during sintered component molding according to the present invention.

The sintering method is;

A mixing step (10) in which a solid lubricant is added to the metal powder to be sintered for ease of shape shaping and ease of mold release, and mixing;

A shaping process (20) for shaping the mixed powder in the mixing step (10) by rapidly dividing the powder into a desired shape and applying pressure thereto;

A sintering process (30) for imparting physical properties to the shaped body formed in the forming step (20) by applying heat so as to cause a pyramidal bonding by atomic diffusion movement of the powder particles;

A squeezing step (40) for re-pressurizing the sintering step (30) so as to improve the overall precision by correcting deformation or the like which may occur in the sintering step (30);

A post-treatment step (50) is carried out through a process such as heat treatment, finishing and coating for improving the quality and durability of the product through the shaping step (40).

In the molding step 20, a feed chamber 53 is formed so as to be supplied with the powder 52 to be molded in the lower mold 51 for product molding, and a molded product 53 is formed under the lower mold 51 And a core rod 55 protruding upward so as to form a hole.

Above the lower mold 51, there is provided a top mold for press-molding the powder 52 rapidly dispersed in the feed chamber 53 by descending.

In the present invention, the core rod (55) provided in the lower mold (51) of the molding step (20) is improved to minimize or increase the drop in the partial density variation that may occur during the pressing process of the powder Thereby contributing to the improvement of the quality and durability.

For this purpose, according to the present invention,

The upper end face 56 of the core rod 55 is positioned lower than the feed face 57 of the powder 52 that is rapidly dispersed in the feed rate chamber 53 and the upper die is lowered to form the rapidly divided powder 52 The core rod 55 is raised so that the powder 52 is supplied to the periphery of the core rod 55 above the core rod 55 so that the density around the core rod 55 is higher than the density of the other portions So that it can maintain a high state.

Of course, as another example, even if only the core rod 55 is raised and the entire lower mold 51 and the feed chamber 53 are lowered to raise the core rod 55, the same is true.

It is preferable that an inclined surface 60 is formed on the upper end surface 56 of the core rod 55 so that the powder 52 located above the core rod 55 is naturally supplied around the core rod 55.

The upper end of the core rod 55 is moved up by the upward movement of the core rod 55 in the process of pressing the rapidly divided powder 52 while matching the lower die 51 and the upper die in the molding step 20, The powder 52 is supplied around the core rod 55 to maintain the density at the time of molding at a level higher than that of the other portions.

When the molded product is completed, the density of holes formed by the core rod 55 is increased, so that the quality and durability of the product can be improved.

As described above, the present invention improves the molding process to set the position of the top surface of the core rod lower than that of the rapid surface, and then, when the core rod is compressed, the lower mold and the feed chamber are lowered, So that it is possible to produce a product capable of controlling the partial density after molding, thereby providing a product close to perfection.

Claims (3)

A mixing step (10) of mixing the powder to be sintered; A feed chamber 53 is formed in the lower mold 51 for the purpose of product molding so as to receive the powder 52 to be molded; A core rod 55 protruding upward below the lower mold 51 so as to form a hole of a product to be molded; A shaping process 20 for forming a product shape by providing an upper mold for press-molding the powder 52 rapidly dispersed in the feed chamber 53 by the lowering of the lower mold 51; A sintering step (30) of applying a heat to the shaped body formed in the forming step (20) to impart physical properties; A shaping step (40) for correcting deformation that may occur in the sintering step (30) and improving the overall precision; In a sintering process completed by a post-treatment process (50) through heat treatment, finishing, coating and the like for improving the quality and durability of the product through the shaping step (40); The upper end face 56 of the core rod 55 is positioned lower than the feed face 57 of the powder 52 that is rapidly dispersed in the feed rate chamber 53; When the upper mold is lowered to press the rapidly divided powder 52, the core rod 55 is raised so that the powder 52 is rapidly supplied to the upper portion of the core rod 55 around the core rod 55, So that a decrease in the density around the rod (55) can be eliminated. The method of claim 1, further comprising: The lower mold 51 and the feed chamber 53 are entirely lowered so that the core rod 55 protrudes above the feed surface 57 in order to prevent the density around the core rod 55 from being lowered. Method of removing density variation during component molding. The method of claim 1, further comprising: The inclined surface 60 is formed on the upper end surface 56 of the core rod 55 so that the powder 52 located above the core rod 55 can be naturally supplied around the core rod 55 A method for removing density variation during sintered component molding.