JPH06128603A - Method of manufacturing injection-molded powder metallurgy products - Google Patents

Abstract

(57) [Summary] [Structure] The method for producing an injection-molded powder metallurgical product according to the present invention comprises injection-molding a kneaded product of a metal powder and a binder, and introducing the obtained molded product into a debinding furnace to remove the binder. In addition to the above, temporary sintering is performed at 700 to 1000 ° C., and then the temporary sintered body is introduced into a sintering furnace to perform sintering. [Effect] According to this method, since the debindered molded body becomes a temporary sintered body, it has sufficient strength, and it becomes extremely easy to handle when it is transported from the debinder furnace to the sintering furnace. For example, in this carrying step, it becomes possible to automate robots such as alignment without using human hands, which is extremely useful for improving productivity.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an improved method for producing sintered products using injection molding powder metallurgy.

[0002]

2. Description of the Related Art Injection molding powder metallurgy is a suitable method for producing a sintered metal product having a three-dimensionally complicated shape, for example, a sintered metal product having a thin portion or a knife edge portion. Are known. In this method, a kneaded material of raw metal powder and a binder is injection-molded, the obtained molded body is introduced into a debinding furnace for debinding, and then the molded body is introduced into a sintering furnace and sintered. Is to do.

[0003]

However, in the conventionally known injection molding powder metallurgy method, since the unbindered green body before sintering is low in strength, it is transferred from the debinder furnace to the sintering furnace. Therefore, the transfer process is liable to be broken, and the transfer process must be manually performed, which makes it difficult to automatically mechanize by a robot or the like.

In this case, since the binder removal and the sintering are both heat treatments, it is conceivable to perform them in the same furnace or to perform the binder removal in the sintering furnace. Therefore, it can be considered to be practically impossible. That is, in general, it is inevitable that the binder is removed in the state where the molded body is embedded in the ceramic powder such as alumina, especially for the molded body having a complicated shape. Further, during sintering, although it varies depending on the metal material used and the shape of the molded body, shrinkage of about 15% usually occurs. Therefore, if the binder is removed and then the sintering is performed as it is, the ceramic powder is caught in the molded body due to the contraction at the time of sintering, resulting in an abnormal deformation.

Further, in the case of industrially producing a metal sintered product, an extremely large variety of products are simultaneously produced, and in particular, in the debinding process, a multi-product compact is simultaneously treated by a mixed loading process during operation. On the other hand, the sintering process is
Since the conditions such as the sintering temperature and the time are different depending on the kind of the metal material used, it is impossible to simultaneously perform the processing on various kinds of molded products. Therefore, as a practical matter, debinding and sintering cannot be performed in the same furnace.

Further, it is desired to perform sintering in the sintering furnace without debinding. This is because the structure of the sintering furnace is simple, the equipment cost is low, and the sintering furnace is not contaminated with the removed binder, and the occurrence of troubles is reduced.

Therefore, an object of the present invention is to provide an injection-molded powder metallurgy which has a sufficiently high strength of a green body before sintering and which can be effectively conveyed from a debinding furnace to a sintering furnace without trouble such as damage. To provide the law.

[0008]

According to the present invention, a kneaded product of a metal powder and a binder is injection-molded, and the obtained molded product is introduced into a debinding furnace to perform debinding, and subsequently calcination. A method for producing an injection-molded powder metallurgical product is provided, which comprises the steps of: binding, and then introducing the pre-sintered body into a sintering furnace for sintering.

[0009]

In the present invention, the remarkable feature is that the binder is removed in the debinding furnace and the preliminary sintering is subsequently performed. The strength is improved, and it becomes possible to effectively avoid troubles such as breakage when the molded body is transferred from the debinding furnace to the sintering furnace. For example, the provisional sintered body is supplied to a parts feeder or the like and automatically aligned. Then, it becomes possible to carry the material to the subsequent sintering step.

In the present invention, the term "pre-sintering" means that a part of the surface of the powder particles constituting the molded product is coagulated, and it varies depending on the kind of the metal powder to be used.
In general, sintering is performed at a temperature of 1000 ° C. or higher, whereas pre-sintering is performed at a temperature range of 700 ° C. to 1000 ° C. The specific calcination temperature is, for example, Fe-Ni-C.
About 700 ℃, 800 ℃ with water atomized SUS316
Approximately 1000 ° C. with gas atomized SUS316. Further, such temporary sintering is carried out for a time period such that the above-mentioned adhesion occurs and a certain degree of strength is imparted to the molded body, but usually 0.5 to 1 hour is sufficient.

As the furnace for carrying out the preliminary sintering together with the binder removal, a mesh belt furnace or a batch furnace can be used, and the binder removal and the subsequent preliminary sintering are carried out with nitrogen gas, argon gas or the like. It is carried out in an inert gas or in a reducing gas such as hydrogen gas, shift gas, or ammonia decomposition gas.

The method for producing an injection-molded powder metallurgical product according to the present invention is carried out by employing a method known per se, except that the above-mentioned pre-sintering is carried out subsequent to debinding.

For example, as the raw material metal powder to be used, various metal or alloy powders, mixed powders thereof and the like are used depending on the intended product. As the binder, waxes such as paraffin wax and thermoplastics such as polyethylene are used alone or in combination of two or more kinds.

The above-mentioned kneaded material of the metal powder and the binder is subjected to injection molding at a melting temperature of the binder or higher, then introduced into a debinding furnace, and heated to a temperature above the decomposition temperature of the binder for debinding. . The debindered compact is subsequently subjected to the above-mentioned pre-sintering in a debinding furnace.

The obtained pre-sintered body is introduced into a sintering furnace and subjected to sintering, whereby a sintered metal product having, for example, a three-dimensionally complicated shape is obtained. The conditions for such sintering are appropriately determined depending on the type of metal powder used.

[0016]

【Example】

Example 1 10 kg of carbonyl iron powder having an average particle diameter of 5 μm and an organic binder were mixed at a weight ratio of 92: 8 using a small kneader. Using the obtained kneaded product, injection molding was performed at a molding temperature of 80 ° C. to prepare a molded body for guitar parts shown in FIG. 1 having a length of 16 mm, a width of 10 mm, a height of 4 mm and a weight of 4.5 g. The obtained molded body was embedded in an alumina powder on a stainless tray and introduced into a de-by-pre-calcination furnace to remove the binder and pre-sinter. A large batch furnace capable of heating up to 1000 ° C. in an ammonia decomposing gas atmosphere was used as the de-by-temporary sintering furnace. The binder removal and pre-sintering were performed with the thermal history shown in FIG. The tentatively sintered body taken out from this furnace has almost no dimensional shrinkage,
It was strong enough not to be damaged even if dropped on the floor or rolled in a basket. Further, this pre-sintered body was placed in a semi-continuous type vacuum sintering furnace and sintered at 1250 ° C. for 2 hours. The obtained sintered body had a healthy appearance.

Comparative Example 1 An injection-molded article obtained by the same method as in Example 1 was placed in a debinding furnace and debinding was performed with a thermal history shown in FIG. The obtained binder-removed molded product was brittle and damaged when rolled in a tray, so it had to be handled carefully.

[0018]

EFFECTS OF THE INVENTION According to the present invention, the debindered molded body before sintering has sufficient strength, which makes it extremely easy to handle when it is conveyed from the debinding furnace to the sintering furnace. In this transfer process, it is possible to perform robotization such as alignment by a robot without using human hands, which is extremely useful for improving productivity.

[Brief description of drawings]

FIG. 1 is a view showing the shape of a molded body created in an example.

FIG. 2 is a diagram showing a thermal history of de-bindering and pre-sintering performed in Examples.

FIG. 3 is a diagram showing a thermal history of debinding performed in a comparative example.

Claims (1)

[Claims] 1. A kneaded product of a metal powder and a binder is injection-molded, and the obtained molded product is introduced into a debinding furnace to perform debinding, and subsequently calcination is carried out, and then the calcinated product. A method for manufacturing an injection-molded powder metallurgical product, comprising: introducing into a sintering furnace to perform sintering.