Heat Treatment Process of Non-Ferrous Metals
31 January 2019Heat treatment science employs an equal opportunities approach to the field of metal strengthening. That’s another way of saying the techniques used here aren’t just used to harden ferrous workpieces. Indeed, full-service heat treatment facilities toughen soft non-ferrous components, too. Needless to say, though, a different set of processing standards are implemented when a non-ferrous workpiece run is ordered. Changing things up a little, a metal-by-metal list illustrates the different treatment variations.
Copper Alloys
Clients expect malleability when they receive their heat treated copper workpieces. Hindering this expectation, copper parts become brittle when they’re exposed to cold-worked fabrication practices. To minimize this effect, the orange-red metal is annealed at 650°C. Then, thanks to the alloy’s low melting point, copper workpieces can be precipitation hardened at a moderately high temperature. This action is generally sustained for three-hours.
Lightweight Aluminium
Here’s another relatively soft metal, one that’s not generally thought of as a heat treatment candidate. Nowadays, there’s a vast number of alloy-strengthened aluminium families on the market. Of note, manganese or magnesium alloyed aluminium don’t respond well to heat. Let’s drop those unresponsive types and turn instead to the copper and zinc amalgams. Taken as high as 410°C, the metal is held here for a few hours while it’s annealed. Interestingly, although the alloys respond well to solution heating and homogenizing temperatures, aluminium can also be naturally aged. At room temperature, in a warehouse environment, the metal stabilizes slowly after it has been quenched.
Exotic Brass Alloys
Annealed at approximately 590°C, the material strengthening options open up when the metal’s copper and zinc content is varied. This method of classifying different types of brass can be taken even further. For example, there are “Alpha” brasses, which are less than 37% zinc. For “Beta” alloys, the zinc content rises above 37% but stops at a 45% limit. Dependent on these metal ratios, a thermal treatment process is selected. Solution treatment procedures and normalizing operations are common, with the alloy reacting favourably to rapid quenching.
In ferrous metals, the mechanical and material properties correlate directly to the grain properties of a nominated metal. Those grain forms are easily influenced when the carbon content of the workpiece is manipulated. In non-ferrous heat treatment, this approach is much harder to emulate. To overcome such processing hurdles, we seek out recrystallization alterations and quench time controllability. Precipitation hardening and aging work well here, as do annealing operations. Lacking carbon as a process instigating master manipulator, furnace management profiles become essential, as do the quench times and mediums that regulate the recrystallization stage.
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