Forged article with prealloyed powder

#This invention relates to forged articles made from ferrous powder prealloyed with manganese and sulfur. More specifically, the forged articles are forged engine connecting rods.

#The connecting rod manufacturing process involves pressure molding metal particles in a closed mold under significant pressure to produce a green compact form of the rod. Next, the green compact is heated in a furnace sufficiently to form a sintered preform in which metal particles are bonded. Next, the sintered preform is hot forged to final rod shape which increases the rod's density and strength.

#The automobile industry continues to challenge connecting rod manufacturers to increase the fatigue strength of these articles. As a result, higher performance materials are needed for forged connecting rods. The goal Is to engineer a powder metal blend to manufacture connecting rods with the following characteristics: high strength; good machinability; reasonable cost, good weight and dimensional control. Our research included materials considerations; metallurgical and microstructure evaluation; dimensional change measurements; tensile strength; fatigue strength and machinability tests.

#FIG. 1 is a perspective view of a forged connecting rod.

#The methods for preparing the prealloyed powder may vary widely. Typically, the powder is prepared by atomization of a molten metal stream of iron, manganese and sulfur. The resulting particles usually have an irregular spherical shape. To facilitate compaction, the atomized particles can be collected after solidification and subjected to annealing at 1700° F. for about 1-½ hours, followed by grinding to break up particle cakes, and then passed through an 80 mesh sieve.

#The prealloyed ferrous powder then is mixed with copper and graphite at room temperature. The copper powder generally has a purity of 99%. The copper powder and carbon (graphite flake powder), however, are commercial grade materials. The copper powder is mixed in a range of 2.0 to 5.0% by weight of the mixture. The graphite powder is added to yield a final carbon content in the product ranging from 0.2 to 1.0 weight percent.

#FIG. 1 illustrates forged connecting rod 10. Rod 10 has an elongated configuration extending along longitudinal axis A-A. Rod 10 includes midportion 12; small end portion 14; and large end portion 16. Bore 18 is formed through small end portion 14 adapted to receive a wrist or piston pin (not shown) as Is well known in the engine art. Aperture 20 is formed through large diameter end 16 and is adapted to receive a journal of a crankshaft (not shown) as is well known in the engine art. Large end portion 16 has a side thrust face 22. Rod 10 includes large end portion 16 having a pair of oppositely facing edges or end surfaces 24. In the particular design of the connecting rod shown in FIG. 1, side thrust face 22 is in a raised plane with respect to the remaining side surface 26. Side thrust face 22 also includes a pair of radially outwardly extending portions 28, 30 located to either side of aperture 20. Portions 28, 30 extend radially outward from aperture 20 and terminate at end of edges 24.