What is brass hot forging?
Brass hot forging or hot stamping consists in deforming a brass bar previously exposed to temperature, then subject to the pressure of two moulds giving it shape. It is one of the oldest metal works processes, by around 8000 b.C. it was already used for obtaining tools, jewellery… hammering on the metal by using stone tools.
The two metallurgic parameters to be taken into account at hot stamping are brass composition and temperature.
Considering brass composition, this material acquires a given properties and affects the mechanic features, plasticity, fusibility and structure capacity by any of the following techniques:
- hot forging or stamping
- machining, including bar turning
Brass used at rmmcia contains the appropriate composition of copper, zinc and other metals to achieve best ability for forging and later machining, usually under regulation EN12165 CW617N.
Generally, hot forging temperature fluctuates between 650 and 750ºC. In order to know minimal temperature needed, which is different for each metal or alloy, we have to take into account that any metal suffers the recrystallisation process: a transformation of the lengthened metal grains which have suffered a deformation in cold to equiaxial or polyhedral grains by heating the material over a minimal temperature. For instance, for the brass we work with the needed temperature goes from 680ºC to 790ºC, the minimal one within this interval and may vary with the type of piece. We should add also that recrystallisation time is the time needed for achieving the 95% of the material recrystallisation, enough to start working with it.
Advantages of the hot forging:
- variety in shape of the pieces, this technique allows more options on shape modifications;
- possibility of serial production at important quantities, we are talking about thousands of pieces/hour;
- less strength required for deformation;
- obtaining of excellent mechanic features with fatigue resistance; this is due to the fact it contains an isotropic property of strength: brass by forging keeps the same physical properties at all directions, thanks to the fact the internal structure is essentially unchanged from the brass bar coming from an extrusion process;
- perfect sealing of the pieces by the lack of porosity or fissures;
- facilitates the later machining of the pieces, becoming a more competitive and complex elements;
- less costly than casting;
- possibility of brass waste material recycling.