When Only a Hammer Will Do

To those who work daily in the forging industry—people such as SIFCO employees—forging is understood to be a superior process when it comes to shaping metal into the strongest and most reliable parts known to humankind.

True, forging has been around for about 4,000 years, and longevity is worthy of some distinction on its own merit. But forging has so many advantages over other metal-working processes, even in the 21st century, that it begs an explanation as to why.

1537bThere are three main metal-working processes to make a part: machining from bar, casting or forging. Simply put, forgings are stronger, more reliable and more adaptable than the other methods.

Only forging allows for the directional grain alignment that results in the maximum strength of a forged part. “We forge from bars that we get from steel mills,” said Jim Woidke, SIFCO’s chief operating officer. “Those bars have grain flow that is parallel to the length of the bar. When you forge the part, you will align the grain flow to the shape of the part. Our engineers take the shape of the part into account when designing the forging dies.”

1537aA cast part doesn’t have the grain flow or directional strength that a forged part can provide, and the process of casting can’t prevent formation of certain metallurgical defects, according to the Forging Institute of America.

“The downside of a machined part from bar is that you don’t have the strength level,” said Woidke, “because you haven’t aligned the grain boundaries with the shape of the part. Also, there could be a lot of material that’s wasted.”

Forged parts offer greater consistency than machined or cast parts: There are no seams that can cause a part to fail, and a forged part has no internal voids that can bring about failure under stress or impact. There is also far less scrap, which means greater efficiency and cost savings. A way of looking at it is to ask if safety or long-term reliability is essential, then a forged part is required. One look at a sample list of SIFCO forged parts should be enough to convince anyone of that fact: landing gear components, aircraft turbine engine components, gearboxes, engine shafts, compressor discs, wheel and brake assemblies, structural supports, propeller hubs and turbine discs. Each one of these products speaks to safety. From the people in the front office to the men and women on the factory floor, SIFCO has always taken that profoundly seriously.

When will only a forging hammer do? A forging hammer will only do when lives are on the line, such as in commercial aircraft, military jets and helicopters. That seems obvious, but there are less obvious examples, too, including one that goes back to SIFCO’s beginnings.

In SIFCO’s early days, C.H. Smith Sr. identified a part used in large quantities in oil refineries. The part, a “still-plug,” was subjected to high temperatures, a corrosive atmosphere, and tremendous pressure. Smith determined that the part would have a longer life if it were forged rather than cast from a nickel alloy known as monel (a composite of nickel, copper, iron and other trace elements) metal. In 1983, in a speech given by his son and successor at SIFCO, C.H. Smith Jr. said: “A sample order, produced for the Standard Oil Company of New Jersey [now Exxon], was so successful that SIFCO was producing still-plugs for refineries all over the United States. Technology and metallurgical control gave the company an edge over competitors who doubted a nickel-based alloy was forgeable.”

“There are lots of things you can do with a hammer that you can’t do on a press,” commented SIFCO Chairman Jeffrey Gotschall. “At SIFCO we specialize in small runs, exotic shapes and exotic materials.” And indeed, that forged still-plug was first forged in the manner Gotschall spoke of, but in the 1920s. Nearly a century later, forging remains the best manufacturing process for critical parts.

The facts of forging’s superior strength and reliability, the economic advantages, the simplified production and the integrity of the forged material will not change with times, even if the products change and evolve, whether for alternative energy sources on Earth, commercial or military aviation, or for space travel. When only a hammer will do, SIFCO will continue to stand ready.