Tool steels are hardened alloys. They’re shaped into sharp-edged cutting and forming profiles. However, in order to retain those rigid geometrical outlines, tool alloys need heat treatment work. With the post-manufacturing work, the super-hardened metals gain additional mechanical strength and material durability. They won’t succumb to abrasive wear, nor will they experience metal fatigue when forced to operate around the clock on a heavy-duty production line.
On Playing Devil’s Advocate
Skipping the heat treatment stage, a batch of sharp tool blades heads to market. The tools are keenly sharp, and they operate as intended, cutting the cleanest of edges. At least, that’s what happens initially. After an undetermined period of time, the blades dull. They no longer slice neatly. Ragged edges are slipping untidily off the conveyor belt. Elsewhere, punches are fracturing, dies are warping, and impact-heavy tools are shattering. The reputation of tool-quality steel is being sullied.
Counterintuitive Hardness Issues
That’s what the industry has to look forward to if steel tools aren’t post-processed. The tools will initially operate as intended, but the effects of fatigue and wear will make the equipment unusable. The almost diamond-hard point of a punch dulls, as does the edge of a formerly razor-sharp cutting tool. Dies crack when they’re used to form metal parts, even when that subject metal is soft. And all of the failures are taking place because an effective heat treatment program hasn’t been incorporated. Think of it, the notion that these alloys are already super-hard. But hardness does not always equal durability. In fact, overly hard tools can be brittle. They shatter when put into service because of that undesirable brittleness factor.
Hitting The Hardness Sweet Spot
So tool hardness isn’t necessarily a good feature, not if the hardened tool steel is brittle. We heat treat the part, anneal and normalize the tool components. Mechanically hard and profile-obdurate, the next stage takes the tool through an essential tempering operation. It’s here that work stress and process brittleness are eliminated. The tools are heated and quenched, tempered and heated again, all so that the steel balances its essential hardness quotient against a much-needed fatigue resistance feature.
To add substance to the matter, imagine the tool steel arriving for machining as an annealed product. Cold and hot-worked stresses are gone, the tool steel is rated according to the Brinnell hardness scale, and it’s ready for further processing. An effective heat treatment strategy transforms the homogenized microcrystalline structure of the steel. It grants the tools mechanical durability, fatigue-proof strength, and a newly refined level of uniform product hardness.