Laws of Metal Forging
Forging is the process of heating and shaping metal into specific shapes. “Hot Forging” is when heated metal is compressed and shaped using a hammer or die. E.J. Hadaway specializes in a few hot forging techniques, described below.
Open-die forging is also known as “smith forging”, and it is one of the more familiar types of forging. The heated metal is pressed between two “open” dies, meaning they are flat surfaces or they don’t fully enclose the metal. The metal is compressed and then its position is adjusted slightly before the next blow; the shaping is accomplished over a series of compressive movements. Open-die forging is a bespoke process, relying on the skill of the operator and the tools used; it’s best for producing small quantities of custom-made products.
In closed-die forging, the heated metal is compressed between two dies that act as molds to create an impression of the intended shape. The process tends to force some metal outside the die impression, called “flash”; this is trimmed off later in the process. Closed-die forging is the most common forging process.
In upset forging, one end of a heated metal bar is flattened or widened through compressive pressure on the length of the bar; for example, a small length of metal could be made into a nail or screw when one end is compressed to form the nail head. When designing an upset forging process, three specific principles should be followed:
– There is a limit to the length of unsupported metal that can be upset in one blow without injurious buckling. That limit is three times the diameter of the bar (3D).
– However, lengths of metal greater than 3D can be upset successfully, as long as the diameter of the upset is no more than one-and-a-half times the diameter of the bar.
– In an upset requiring metal length greater than 3D, where the diameter of the cavity is no more than one-and-a-half times the diameter of the stock, the length of unsupported metal past the face of the die must not exceed the diameter of the bar (1D).
Please contact us for a consultation about your forging needs.