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Publication numberUS3795129 A
Publication typeGrant
Publication dateMar 5, 1974
Filing dateJan 21, 1972
Priority dateOct 7, 1971
Also published asDE2205493A1
Publication numberUS 3795129 A, US 3795129A, US-A-3795129, US3795129 A, US3795129A
InventorsGoto S
Original AssigneeGoto S
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method of forging sintered articles of high density
US 3795129 A
A method of forging sintered articles of high density characterized in that pre-shaped powdery articles are heated to a temperature of 1120 DEG -1200 DEG C and then are forged by a tool, which is pre-warmed to 80 DEG -120 DEG C and maintained at such pre-warming temperature, at a tool speed of 7-10m/second. The articles thus forged are rapidly separated from the tool through the medium of an ejector provided on the forging machine.
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Description  (OCR text may contain errors)

United States Patent Gate Mar. 5, 1974 [54] METHOD OF FORGING SINTERED 2,821,016 H1958 Dickson 72/342 ARTICLES OF H DENSITY 3,645,728 2/1972 Hrinevich, Jr. 29/4205 3,605,245 9 1971 Zapf 29 4205 [76] Inventor: Saburo Goto, 49-Banchl, Shrchrku Kamiumenoki-cho, Kita-ku, Kyoto, Japan Primary ExamznerL0well A. Larson Attorney, Agent, or FirmWenderoth, Lind & Ponack [22] Filed: Jan. 21, 1972 l [2 1 App] No 219,652 ABSTRACT [30] Foreign Application Pri i Data A method of forging sintered articles of high density Oct 7 I971 Ja an M8909 characterized in that pre-shaped powdery articles are p heated to a temperature of ll20l200C and then are forged by a tool, which is pre-warmed to 8|. 72/342,B and maintained at Such pre warming term I peramre, at a too] speed of 7 10m/second The arti [58] Field of ch 29/4205 72/342 cles thus forged are rapidly separated from the tool [56] References Cited through the medium of an ejector provided on the forging machine.

UNITED STATES PATENTS 8/1956 Boegehold et al. 29/4205 3 Claims, 1 Drawing Figure METHOD OF FORGING SINTERED ARTICLES OF HIGH DENSITY BACKGROUND OF THE INVENTION This invention relates to a method of forging whereby the necessity of the precise forged articles of high density can be produced without re-sintering process of moulding.

This invention is characterized in that powdery articles, pre-shaped by a conventional method or by a specific method, are heated to a temperature of ll20 1200C, while a tool is pre-warmed to a temperature of from 80 to 120C and is maintained at this prewarming temperature. The heated articles then are forged in the tool at a speed of 7 lm/second. forging, the finished forged article and the tool are separated rapidly by a separating apparatus provided on the forging machine.

High density is essential for sintered articles such as forged machine parts. In this respect, US. Pat. No. 3,410,683 discloses the method whereby a molded article is heated to a temperature of about 750C 1 100C before it is re-pressed, and the press tool is pre-warmed to a temperature of 150C 350C and is maintained at this pre-warming temperature throughout the repressing operation, in order to keep the recrystallisation conditions of the article during re-processing constant. It appears that the purpose of this method is to obtain precise finished articles by maintaining the temperature of the press tool high and by maintaining the temperature of article low or from 750C to 1 100C so as to reduce the temperature difference between the tool and the material, thereby avoiding temperature drop of the article as far as possible and thus increasing the fluidity of the material. However, the lower temperature of the actually material results in lowering the fluidity and consequently lowering the degree of preciseness of the finished article. Moreover, since the press tool is bulky, it is extremely difficult to maintain its temperature high.

The most important problem raised in hot forging is that during the processing of a highly heated article on the press tool, the surface temperature of the tool rises and the surface of tool is transformed due to thermal fatigue and wear. A finished article, after separation from the tool, is cooled by compulsory cooling but it is difficult to prevent the rising of its temperature due to conduction of heat at the contact surface with the tool during processing. Thus, the best way for forging a powdery substance is to process the heated substance as quickly as possible. Furthermore, a faster tool speed and a shorter processing time improve the flow of the material of a preshaped sintered article, decrease the coefficient of kinetic friction and effect the uniform distribution of pressing force into every part of the finished article, with the result of uniform density. The forging machine primarily used is an oil-pressure forging press of low processing speed (0.6m/second or lower). Presses such as the drop hammer, friction press, etc., work at the medium speed or 2 4m/second, and a forging machine of the upward pressurizing type works at the high speed of 7 lOm/second.

As is obvious from the foregoing, the time during which the tool makes contact with a heated article decreases in inverse proportion to the tool speed. Therefore, when using a forging machine of low speed, the

temperature of the tool must be kept at least as high as 350C, or otherwise the article undergoes a large temperature drop at the area in contact with the tool, with the result of uneven density due to the partial difference in cooling speed. On the other hand, when a forging machine with a high processing speed, such as DYNAPACK, is used, the wear of the tool is large due to the longer time required for separation, even though the operating speed is high (12 l9m/second).

SUMMARY OF THE INVENTION In the present invention, a forging machine having a high processing speed and a shorter tool separation time is used, for example, a forging machine of the KJ H series. This type of forging machine belongs to the group of hammering machines of the upward pressurizing type. It works at a speed of 7 lOm/second and is equipped with a tool separating apparatus such as an ejector. It provides optimum conditions for obtaining the uniformly high density of the powdery article during forging because of the synchronization of the dropping of an upper tool and the rising of a lower tool. In the present invention, a lubricant may be applied to the tool, instead of adding a lubricant to the powdery substance.

BRIEF DESCRIPTION OF THE DRAWINGS The single FIGURE is a microscopic photograph of a finished article forged in accordance with the present invention.

EXAMPLE OF INVENTION The result of test forging carried out by using the above discussed forging machine in accordance with the temperature and other limitations of the process of this invention was as follows:

Forging conditions:

Pre-shaped powder: Electrolytic iron powder Pressed powder density: 6.8g/cm Forging temperature: 1 180C Heating duration: 30 minutes (hydrogen atmosphere) Processing energy: 0.7 ton m Tensile Charpy Density strength Elongation impact value g/cc kg/mm Kgm/cm 7.85 26.24 55.7 30 or more As is obvious from the above test results, forged articles produced according to the present invention exhibit superior physical properties to conventionally forged articles.

What is claimed is:

l. A method for forging a sintered article having a high density, said method comprising:

pre-heating to a temperature of 80-120C the forging tool of a forging machine of the type having an upper element and a lower element movable together in syncronization;

heating a pre-shaped powdery article to a temperature of ll20l200C;

forging said heated pre-shaped powdery article by said pre-heated tool at a forging operating speed of ing is accomplished by a synchronized lowering of said upper element and raising of said lower element.

3. A method as claimed in claim 1, wherein said preshaped powdery article is heated to a temperature of 1 -l200C.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2757446 *Jun 4, 1952Aug 7, 1956Gen Motors CorpMethod of manufacture of articles from metal powders
US2821016 *Mar 3, 1955Jan 28, 1958Dickson William MMethod of hot forging or extruding metal shapes and lubricant for use in hot forging and extruding operations
US3605245 *Oct 8, 1969Sep 20, 1971Krebsoege Gmbh SintermetallProcess for manufacturing high density press-formed articles
US3645728 *Jun 3, 1970Feb 29, 1972Gen Motors CorpMethod for making spark plug shells
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3864809 *Mar 29, 1973Feb 11, 1975Int Nickel CoProcess of producing by powder metallurgy techniques a ferritic hot forging of low flow stress
US3889350 *Oct 9, 1973Jun 17, 1975Ford Motor CoMethod of producing a forged article from prealloyed water-atomized ferrous alloy powder
US4019239 *Sep 11, 1974Apr 26, 1977Hoganas AktiebolagMethod of producing magnetite article
US4244738 *Mar 24, 1978Jan 13, 1981Samuel StorchheimConsolidation into a high density article with better isotropic strength than other methods provide
US6110419 *Dec 2, 1997Aug 29, 2000Stackpole LimitedPoint contact densification
WO1979000833A1 *Mar 23, 1979Oct 18, 1979Iit Res InstMethod of and apparatus for hot pressing particulates
U.S. Classification72/342.8, 419/28
International ClassificationB22F3/14, B21J5/00, B22F3/17, B22F3/02, B22F3/00
Cooperative ClassificationB22F3/14
European ClassificationB22F3/14