Sinter-Hardened Steels

 

Cost-efficient PM Processing for hardenable alloy steels

Process and Equipment:

ASCO Sintering manufactures parts by conventional Powder Metallurgy which is also known as “mold and Sinter”. During sintering, enhanced cooling can be used to improve metallurgical properties without subsequent heat treating processes. Continuous sintering furnaces are used to move product through atmosphere controlled furnaces. It starts in the pre-heat zone used to burn off lubricant that was added to the powder for compaction. From pre-heat there is a transition to the “high temp” zone. It is in this zone where metallurgical or diffusion bonding between the particles takes place. After sufficient “time at temperature”, parts then enter the cooling zone. This cooling zone combines radiant and convection cooling, exchanging heat between the atmosphere and the surrounding water cooled muffle. The cooling rate can be drastically increased if the atmosphere in the first section behind the high-temp zone is circulated through a heat exchanger .The resultant rapid cooling of the atmosphere enables sinter hardening by accelerating the transition of steel from the austenitic phase to a martensite-bainite structure. Once cooled to room temperature, the final step is to temper the matensite in a secondary batch type furnace to draw the hardness back and restore ductility.

Benefits:

  • The need for a second separate Austenitizing operation is eliminated. This is less steps which means lower costs and shorter process cycle times

  • Apparent hardness up to 45HRC

  • Particle Hardness up to 57HRC

  • Superior  dimensional control when compared to conventional heat treatment

  • Environmentally friendly; quench oil entrapment is eliminated  during tempering

Materials:

  • ASCO processes the full range of MPIF Standard 35 PM Steels that feature nickel, molybdenum, and manganese as major alloying elements in combination with elemental copper and carbon in the form of graphite

  • Special chromium-molybdenum manganese steels are also widely used

ASCO Sintering has two enhanced cooling/sinter hardening systems to offer: Our Vari-Cool and Hyper Cool processes both operate on a similar principle. Please contact ASCO Sintering for a better understanding of which of these systems would be the right one for your application.