Posted by MoparNorm on Tuesday, October 26, 2004 at 8:23PM :
In Reply to: mo'par norm, please elucidate some erudition posted by wally on Tuesday, October 26, 2004 at 7:22PM :
From a technical manual, abridged of course...
Malcolm Blair and Raymond W. Monroe,
Steel Founders’ Society of America, Crystal Lake, Illinois:
"Much has been said and written recently by the forging industry about the advantages of forged products over castings. Such articles with headlines such as "Upgrade to Forgings" intend to imply that castings are in some way inferior and less reliable. It should be recognized that castings and forgings start from very similar beginnings and castings can have some very distinct advantages over other product forms, including forgings
Most steel components start as castings: metal that has been melted, poured into a mold and solidified. In the casting process at the foundry, because the mold has the shape of the desired component, all that remains to be done after casting are the various finishing operations.
With forgings, the first shape is an ingot or continuously cast billet. Ingots are large, usually rectangular in form and weigh up to several tons. Ingots or continuously cast billets are forged into shapes by hammers or presses. Extensive machining to final configuration usually is required, and welding also may be necessary before finishing operations can begin.
In forging, metal is moved while it is still in the solid state. Because the forging billet is solid, substantial force is required to change its shape to the desired configuration. Because of this, the required force increases as section size increases. In practical terms, there is a limit on size and section thickness produced by forging. The principal mechanical properties of interest to designers are strength, ductility and hardness. But how does the user know the mechanical characteristics of a part?
For cast steel, it is relatively easy. If the component is made from a standard alloy, the characteristics are given in a standard specification. If it is made from any other alloy, standard foundry tests will provide the answers. The values will apply to that component regardless of the axis along which measurements were made.
Many metal parts are made from rolled products like bars or plates. The rolling process changes the properties of the metal. The major advantage is that the strength is increased in the rolling direction or the longitudinal axis. Both forgings and fabrications have directional properties as a result of the rolling process."
There you have it, in short, and in English, forged steel is denser, harder, and more consistent in it's properties. = )
MN