DE2205493A1 - PROCESSING AND FORMING SINTERED WORKPIECES HIGH DENSITY - Google Patents

Description

DIPL.-ING. HARRO GRALFS PATENT ADVOCATE

33 BRAUNSCHWEIG

AT CIVIL PARK 8 TELEPHONE (053D7479B

February 3, 1972 i - G 1909

Sabtiro Goto

4-9-Banchi

Shichiku Kamiumenoki-cho

Kita-ku

Kyoto, Japan

Process for deforming sintered workpieces of high density

The invention relates to a deformation method with which precisely shaped, high density articles can be produced without the need for re-sintering the workpiece is required.

The invention is characterized in that powdery workpieces, which are preformed by means of a conventional or special process, are ^{heated to a temperature between 1120 and 120O 0} C, and that the tool is ^{preheated to a temperature between 80 and 120 0} O and at this preheating temperature is held, whereupon the deformation process takes place at a tool speed of 7 to 10 m / sec; and that after the

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IANK DEUTSCHE BANK AG. SR AUN SCHWEIG. ACCOUNT NO. OS / 017 88 POST CHECK ι HANNOVER 26 16 01

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quickly form the finished workpiece and the tool by means of a cutting device on the forming machine separated from each other.

For sintered objects such as B. molded machine parts, the high density is essential. Therefore, the US Patent 3 4-10683 discloses a method in which the molding is heated to a temperature of about 750 to 1,100 ⁰ C before it is compressed again, and in which the pressing tool to a temperature between 150 and 35O ⁰ C is preheated and kept at this temperature during the pressing process in order to keep the Eekristallisierungsbedingungen constant for the workpiece material during the deformation process. It seems that the production of this method is intended by in the final state of precisely shaped products by means, in which the temperature of the pressing tool is high and the temperature of the workpiece material is kept low or 750-1100 ⁰ C, so that the temperature difference is reduced between Wakzeug and workpiece in order to prevent heat extraction from the workpiece as much as possible and to increase the flowability of the material. However, a lower temperature of the material causes a decrease in the flowability and accordingly also a reduction in the achievable accuracy of the finished product. In addition, however, because of the bulky and bulky tool shape, it is extremely difficult to keep the tool at its high temperature.

The main problem with hot working arises from the fact that when working a highly heated Workpiece in the tool shape, the surface temperatures rise and the surface of the tool as a result of a thermal material fatigue and as a result of wear

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is deformed. A finished workpiece is after that Separation from the tool by means of forced cooling cooled, as it is difficult to achieve during the deformation process in accordance with the thermal conductivity in the area of the contact surfaces to prevent temperature increase. It is therefore the best solution "when deforming powdered materials, the heated material so quickly to process as possible. In addition, a higher tool speed and a shorter processing time Both the flow of the preformed sintered material workpiece and the kinetic one improves The coefficient of friction is reduced, and there is a more even distribution of the pressing force overall achieved every part of the workpiece, so that there is a uniform density of the finished workpiece.

The most common deforming machine is an oil press with a low working speed of 0.6 m / sec or below. Other machines, such as die presses, friction presses etc., have an average working speed of 2 to 4 m / sec. On the other hand, pressurized ones work upwards Machines with a high speed of 7 to 10 m / sec.

From the above it can be seen that the contact time between the tool and the heated workpiece is inversely proportional the working speed is. Therefore, when using a deforming machine, a low operating speed must be used the temperature of the tool in the lowest pail must be kept at 150 to 550 ° C, otherwise the temperature will drop occurs at the contact surfaces between the tool and the workpiece to be processed, which corresponds to the partially different cooling speeds different densities result. On the other hand, if you use a High speed deforming machine, such as

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for example the DXETAPACK commercially available in Japan, then the tool wear due to a required longer cutting time of the tool is great, although the processing time is short in itself (12 to 19 m / sec). Therefore, to carry out the method according to the invention the use of a forming machine with a high operating speed and a shorter tool parting time proposed, for example, a KJH type deforming machine commercially available in Japan. This deformation measure chine belongs to a group of impact presses with tools guided upwards under pressure. they work with a speed of 7 to 10 m / sec and are equipped with an ejector for separating the tool. You have by the downward movement of an upper tool part and the upward movement of a lower part of the tool optimal properties to achieve a uniform density with a powdery, material to be deformed. Instead of adding a lubricant to the powdery material, you can perform of the method according to the invention also includes the lubricant can be added directly to the mold. One with this deforming machine and with the ones according to the invention The series of tests carried out under temperature conditions led to the following result:

Deformation conditions

preformed material: electrolytic iron powder

Compressed powder density: 6.8g / cnr

Deformation temperature: 1180 ⁰ G

Heating time: 30 minutes (hydrogen atmosphere)

Working energy: 7OO kpm

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Workpieces fully formed according to these conditions were microscopically magnified 200 times on their physical properties investigated (cf. the attached microscope photo). There were the following Values determined:

density

g / cm ⁵
7.85

tensile strenght

kp / mm 26.24-

f6 6 L2 6 J lθ

^w Impact test elongation at break (Charpy pendulum hammer)

% 55.7

kpm / cm

30 or higher

From these values it can be seen that the workpieces produced by the method according to the invention are the Conventional methods are superior to processed workpieces in terms of their physical properties are.

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Claims (2)

Claims 1. A method for shaping sintered workpieces of high density, characterized in that powdered, preformed workpieces are heated to a temperature of 1120 "to 1200 ⁰ C and by means of a tool preheated to a temperature * of 80 to 120 ° C and kept at this preheating temperature a tool speed of 7 to 10 m / sec, and that after the deformation, the workpiece is quickly separated from the tool by means of a cutting device arranged on the shaping machine. 2. The method according to claim 1, characterized in that a downwardly moving upper tool mold and an upwardly moving lower tool mold, the movements of which are synchronized, are used for deforming. J. The method according to claim 1 or 2, characterized in that the deformation takes place by means of a machine with an ejector sum separating the tool and releasing the workpiece Bvs the tool shape, 4-, Method according to one of the preceding claims, characterized in that a lubricant is introduced into the tool before the deformation. 309818 / 064Θ