Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
  • C22C33/0264—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements the maximum content of each alloying element not exceeding 5%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy

Definitions

• the invention relates to a method for producing high-strength
• a minimum tensile strength of 750 N / mm 2 is considered to be high strength
• This known steel alloy powder is produced by water atomization, subsequent reduction annealing and grinding of the resulting agglomerate. As further described in EP 0 136 169 B1, this powder after mixing with 0.5% by weight
• the parts thus hardened were finally tempered at 170 ° C for 90 minutes. Afterwards, the parts should have a tensile strength of 1000 or 1170 N / mm 2 .
• Energy use also includes the use of an oil bath as a quenching medium. The latter is not just from a precautionary point of view
• Sintered parts adhering oil production problems since in many cases it must be removed thoroughly in order to obtain usable parts. Examples of this include oil pump and gear parts that are delivered to the end user ready for installation. Compared to the oils used in engine and gear construction, the hardening oil has only little lubricating properties and must therefore be removed. This removal also often requires
• the object of the invention is therefore to provide a method with which high-strength sintered parts can be produced, but for the hardening of which no quenching in an oil bath is required.
• Self-hardening agent i.e. a material that can be cooled comparatively mildly (in air or under a gas shower arranged in the cooling zone of the sintering furnace) and which nevertheless guarantees complete martensitic hardening. Due to these mild cooling conditions, hardening stresses do not occur, as in the known oil-hardening material, which result in a subsequent
• Tempering treatment is therefore not only superfluous per se in the material to be used according to the invention, but one should even have expected that tempering would result in a decrease in the strength properties. But that would have meant that the aim according to the invention would not have been achieved. It was therefore completely surprising that in the case of the invention
• Maraging steels during the tempering treatment because when the martensite is stored at 480-500 ° C, intermetallic phases separate from added alloy elements without the martensite converting.
• the alloying elements responsible for this are not contained in the steel powder to be used according to the invention.
• a tempering temperature of about 300 ° C and a tempering time of about 50 to 70 minutes have proven particularly useful.
• the sintering heat for example, have been cooled and hardened under a gas shower arranged in the cooling zone of the sintering furnace, because of their high strength and hardness, they can no longer be subjected to a metal-forming calibration process.
• the method according to the invention allows dimensional accuracies that are below + 0.05%.
• a steel powder with the following composition (% by weight) was produced by water atomization of a steel melt:
• Milling to dissolve the powder agglomerate formed on annealing was 0.15% oxygen content of the powder.
• About 1.0% of finely divided copper and 0.6% of graphite and about 1% of zinc stearate were then added to this steel powder as a lubricant.
• Metal powder presses were produced from this powder by cold pressing with a density of approx. 7 g / cm 3 . These compacts were then sintered at 1120 ° C and from the sintering heat under one

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Powder Metallurgy (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=6398605

Family Applications (1)

Country Status (2)

Families Citing this family (5)

Family Cites Families (4)

• 1990
  • 1990-01-19 DE DE19904001899 patent/DE4001899C1/de not_active Expired - Lifetime
• 1991
  • 1991-01-17 WO PCT/DE1991/000041 patent/WO1991010754A2/de not_active Ceased

Also Published As

Similar Documents

Legal Events