Brazing/heat treating

Numerous types of metals and alloys are used in medical device manufacturing, but different properties of the same material may be necessary for different devices, which can be altered by processes such as brazing and heat treating. By using brazing or heat treating to manipulate the structure of metal after it is formed, the metal’s wear resistance, toughness, or hardness properties can be enhanced.

The brazing process in medical device manufacturing involves joining metals using a filler metal heated just above its melting temperature to flow over (also known as wetting) and join components without melting the base metal. Chemical or mechanical cleaning steps may be necessary before brazing to create the proper surface roughness for wetting. Most brazing happens in an inert environment like a furnace, but a paste, liquid, or powder flux is sometimes required to prevent metals from oxidizing when heated.

There are numerous heat treating methods used in medical device manufacturing, including quenching, a process in which metal is heated to the point where there is a change in the microstructure, and then rapidly cooled to force an unusual microstructure change not found in slow cooling. Milling, buffing, rolling, or forging metal can create stresses in metal parts, but in an annealing process, metal is heated nearly to quenching temperature, but is slowly cooled to create a microstructure free of stress. The stress relieving process heats the part to an even lower temperature to deal with residual stress by partial annealing. Tempering, carburizing, and carbonitriding are other heat treating processes that result in changes to the toughness and hardness of a metal component.