Process and device for producing sintered parts
First Claim
1. A process for producing a sintered part with high wear resistance and good dynamic strength properties from a formed body which has been pressed as a green part from a completely-alloyed air-hardened heat-treatment steel powder with a carbon content of at least 0.3% added as graphite, the process comprising the steps of:
- sintering the part under protective gas at a sintering temperature of at least 1000°
C.;
immediately cooling, the sintered part from the sintered temperature to a first holding temperature in a range of Ar3 to a maximum of 150°
C. above Ar3 and holding the part at the first holding temperature for a first holding period of 5-25 minutes;
cooling the sintered part in an accelerated manner by convective gas cooling to a second holding temperature and holding the cooled part at this temperature for a second holding period, the second holding temperature lying in a temperature range in which a bainitic structure forms, the second holding period having a length so that the part has a bainite structure portion of at least 50%; and
subsequently cooling the part to room temperature.
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Accused Products
Abstract
A process for producing sintered parts with high wear resistance and good dynamic strength properties from formed bodies, which have been pressed as green parts from a completely-alloyed air-hardened heat-treatment steel powder with a carbon content of at least 0.3% added in the form of graphite. The process includes sintering the parts under protective gas at a sintering temperature of at least 1000° C. and subsequent cooling. The sintered parts are cooled immediately after sintering from the sintering temperature to a first holding temperature in the range of Ar3 to a maximum of 150° C. above Ar3 and are held for a first holding period of 5 to 25 minutes at this temperature (austenitizing phase). Immediately after this, the sintered parts are cooled in accelerated fashion to a second holding temperature by convective gas cooling and are held at this temperature for a second holding period. The second holding temperature lies in a temperature range in which a bainitic structure forms and is of such a length that a bainitic structure portion of at least 50% is established. The sintered parts are then cooled to room temperature.
10 Citations
12 Claims
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1. A process for producing a sintered part with high wear resistance and good dynamic strength properties from a formed body which has been pressed as a green part from a completely-alloyed air-hardened heat-treatment steel powder with a carbon content of at least 0.3% added as graphite, the process comprising the steps of:
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sintering the part under protective gas at a sintering temperature of at least 1000°
C.;immediately cooling, the sintered part from the sintered temperature to a first holding temperature in a range of Ar3 to a maximum of 150°
C. above Ar3 and holding the part at the first holding temperature for a first holding period of 5-25 minutes;cooling the sintered part in an accelerated manner by convective gas cooling to a second holding temperature and holding the cooled part at this temperature for a second holding period, the second holding temperature lying in a temperature range in which a bainitic structure forms, the second holding period having a length so that the part has a bainite structure portion of at least 50%; and subsequently cooling the part to room temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A device for producing a sintered part with high wear resistance and good dynamic strength properties from a formed body which has been pressed as a green part from a completely-alloyed air-hardened heat-treatment steel powder with a carbon content of at least 0.3% added as graphite, comprising:
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an electronically controlled sintering furnace having a sintering zone, a sudden cooling zone located behind the sintering zone and having gas cooling, and a conventional cooling zone located behind the sudden cooling zone; an austenitizing zone arranged between the sintering zone and the sudden cooling zone; and a bainitizing zone arranged between the sudden cooling zone and the conventional cooling zone. - View Dependent Claims (10, 11, 12)
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Specification