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The key objective of this course is to help the student to “take a walk” with any green PM part starting at the front of a conveyor furnace up to or near the actual sintering temperature or high heat section of the furnace. Most powdered metal, ceramic, or composite materials are mixed with lubricants and/or binders prior to compaction, injection molding or extrusion into green parts or shapes. In case of Fe- Cu-C- Lube green parts, the students learn to take a “walk” with the green part up to about 1900F in the furnace - before the admixed or to be infiltrated Copper melts at 1983F.

 

“Preparation for Better Sintering” is defined as the complete delubing/debinding, reduction of all surface oxides on the iron or alloy particles, and complete diffusion of the admixed Graphite into the entire iron or alloy matrix. In the case of an Fe-Cu-C-Lube example, complete and proper preparation before sintering renders all internal and external surfaces of particles in each part metallurgically clean before the part reaches a temperature when admixed or to be infiltrated Copper is about to melt. If this very important milestone (metallurgically clean) is reached then the Copper, upon melting, spreads farther and more uniformly along the clean interconnected pores in the iron matrix. This leads to higher strength, less variation in properties, better dimensional control, more uniform microstructure and less or no warpage.

 

By putting science into the art of powder metallurgy, Course 1 prepares the student to perform a high quality preparation of the entire part rather just pre-heating the part. Students start replacing the term “Pre-heating” section with “Preparation” section. High quality preparation throughout the part leads to the overall sintering process that is much more efficient, stable and in control.

 

“Preparation” consists of the following 4 stages:

  1. Melting and Vaporization of the admixed lubricant and or Binder:

  2. Destroying or burning or oxidizing of lubricant and or binder vapors to harmless byproducts like H2O and CO2.

  3. Reduction of all powder particles surface oxides

  4. Diffusion of admixed graphite into iron matrix.

 

The above mentioned 4 stages are covered during the 4-day long hands-on course

through a combination of:

  • 12 pre-designed experiments on the 6 inch belt furnace

  • One experiment outside of the furnace

  • A half dozen or more short lectures between the experiments

  • Lectures from industry experts

  • Students doing all the measurements and data recording in the computers

  • Students working as a team to analyze the data, make graphs and presentations

  • Interactions, discussions and Q/A periods with lecturers and students themselves

  • Reading of published selected articles on the subject matter of the course

  • Discussions driven by students’ questions and concerns from their own plants

  • Students reflecting on what they’ve learned at the end of each day and at the end of the course by writing down what information they felt was most useful

 

Delubing or debinding of the green parts is the first and most important requirement for better preparation before sintering. For this reason, 50-60% of the experiments are devoted to delubing/debinding studies. Students learn the physical properties of the commonly used lubricants and binders, how they come out of parts as vapors, and effective methods to destroy or burn them into harmless byproducts like H2O and CO2. A balance of the experiments are devoted to oxide reduction and diffusion of admixed graphite into the iron matrix.

 

During all these experiments, students learn the role of temperature, atmosphere flow and composition and time in carrying out each stage of the preparation before sintering. At the end of the course, students have an understanding as to what the optimum temperature and atmosphere profile for the preparation part of the process prior to sintering is. During the 4 day course, students learn not only why high quality preparation before sintering is very desirable, but also how it can be completely and efficiently achieved under production conditions. A broad range of part shapes, sizes, compositions, weights and densities up to 7 g/cc are used during the 12 experiments.