Method for Manufacturing Iron-based Powder Metallurgical Parts

A method for manufacturing iron-based metallurgical parts, the method comprising:

• (a) mixing graphite powder, iron powder, alloy element powder, and lubricant powder to obtain a mixed powder;
• (b) pressing the mixed powder on a powder metallurgical molding press to obtain a molded green compact;
• (c) presintering the molded green compacts in a non-oxidizing atmosphere at 600° C. to 1050° C. for 10 min to 300 min to obtain a presintered metallurgical part;
• (d) oxidizing the presintered metallurgical part to form an oxide layer having a thickness of 1 μm to 50 μm on its surface to form an oxidized presintered metallurgical part;
• (e) performing a secondary sintering of the oxidized presintered metallurgical part in an non-oxidizing atmosphere at 1050° C. to 1350° C. for 10 min to 200 min to obtain a sintered metallurgical part;
• (f) performing a process to increase the density and/or surface compactness of the sintered part to form a compact metallurgical part;
• (g) carburizing the compact metallurgical part in an atmosphere having a carbon potential of 0.3% to 2.0% at 700° C. to 1200° C. for 5 min to 400 min to form a carburized metallurgical part, and cooling the carburized metallurgical part to a temperature suitable for quenching;
• and
• (h) quenching and tempering the carburized metallurgical part to achieve the desired mechanical properties, wherein the iron-based metallurgical part comprises iron, 0.2% to 1.5% by mass percentage carbon, the alloy element and the lubricant.