Dezincification resistant brass
Standard Brass components have gained universal acceptance in many facets of the water distribution industry. However, in certain circumstances when exposed to particular combinations of pH and concentrations of chlorides, they can experience a severe form of corrosion known as dezincification.
The solution to this problem is a dezincification resistant alloy - DZR brass. This material is the ideal choice when aggressive conditions prevail.
LDM offers two DZR alloys from its comprehensive range. Both conform to the latest European Standard CW602N (CuZn36Pb2As). They are available in solid rod for machining or hot forging applications, and some Profiles.
DZR - Metallurgical
Standard Extruded Brass contains a mixture of alpha and beta phases, and a fine distribution of lead particles, which impart excellent machinability.
In binary brasses, zinc is soluble in copper up to 37% and exhibits an all alpha phase; further increases in zinc results in the appearance of the second phase, beta.
The combination of these two phases, alpha - ductile at room temperature, and beta - easily hot worked, is the key to wide range and unique fabrication properties of extruded brass. However the beta phase is particularly vulnerable to dezincification.
For maximum protection against dezincification, whilst still retaining the ease of fabrication, three factors have to be balanced to achieve the ideal structure with a minimum beta content. LDM has substantial expertise in these areas.
- Careful control of time and temperature during manufacture, which may include a special heat treatment.
- A slight increase in copper content to minimise the proportion of the beta phase
- The addition of a small amount of arsenic which implies protection to the alpha phase.
Processing of DZR semi manufactured products
When ordering DZR products it is important that the manufacturing process is specified. Metal for machining is treated to the final resistant condition before leaving the LDM factory
Where hot forging is undertaken prior to machining, the material is supplied without heat treatment. It will require careful control of temperature during its further stages of fabrication.
Forging in the range of 700 to 800 °C MAXIMUM is recommended. The material must then be cooled slowly, not quenched or cooled rapidly. Ideally for maximum resistance, a final heat treatment of two hours at 500/525 °C is strongly recommended.
The characteristics of preparation and performance of DZR are very similar to standard brasses for most surface treatment processes.