Brass production on the AMP 20 S

Forging blanks made of brass are mainly used as fitting components in sanitation and heating systems. Brass offers vital benefits in processing: The copper and zinc alloy has far better flow properties than steel, so the forming process is much easier. For example, the AMP 20 S can in most cases be operated below its maximum press load of 900 kN. In the area of the forward dead center, the press loads then climb – as with steel pressing.
 

The key to successful brass processing

We know from decades of experience that, because of its special properties, brass forging requires a different process to that used for producing steel blanks. During training sessions, we share the knowledge we have gained with our customers in order to support them efficiently in all matters. So what are the main factors for success in brass processing?

1. Quality of the alloy

Depending on the area of use, we recommend two types of raw material. To produce conventional brass parts like union nuts or cap nuts, CuZn40Pb2 (DIN 2.0402) quality is used. In brass parts with more complex shapes or extruded parts like spouts or screw nipples, we advise admixing aluminum. The alpha and beta mixed crystals of the alloy give the material good machineability and very good hot formability. The mixed crystals are created by the specific proportion of copper and zinc in interaction with the forming temperature.

2. Forging temperature

Brass only has the right properties for hot forming within a narrow temperature range. In the most unfortunate case, the bar melts during heating or between the last heating coil and the infeed rollers. It is therefore crucial to have a constant temperature across the entire brass bar. The brass bars also need to have a bevel at both ends. This prevents the bars melting together when being fed in or when being heated to the forging temperature.

3. Tool construction

There are essentially only minor differences between steel and brass in three-station tool construction. The main thing to bear in mind is that brass is easier to form and flows easily into all edges. As a result, all clearances – between ejector and die, between punch and die and between punch and holding pin – have to be designed accordingly. Ventilation areas to prevent the ingress of water and air have to be reduced to half the steel values.

Free upsetting without allowing the material to lie radially on the die is inconceivable in brass forming. At the beginning of pressing, the punch also always has to be guided in the die to prevent the material from accidentally flowing out.

A major difference to steel production is to be found at the shearing station, which has to be matched exactly to the requirements for brass production. Shear blades and stationary blades made of high-speed steel can be used, whilst the clamping piece has no function. Infeed rollers with a smaller cross-groove depth and the feed bushes are designed to fit the brass bar in order to minimize its deformation.
 

Side note: Special tool construction with gas spring assembly

At Hatebur, we have developed a flexible die for all workpieces such as spouts, screw nipples and top parts of water taps which require a very deep drilled hole. This allows a long flow section of up to about 38 mm. The associated gas spring assembly operates with a movable piston which is supported on the nitrogen-filled cavity in the bush during forming. A connection hole needs to be provided on the machine part to guarantee nitrogen input.

Coolant

To improve the flow of the material on the tool walls, the tools have to be cooled with an emulsion and lubricated.This emulsion is produced by admixing a lubricating oil in the cooling water tank. The best results are achieved with a lubricating oil content of around 15 percent.

Training sessions 

It is obvious that every production process and every tool has its own peculiarities that cannot be covered in this article. If you would like access to all of our expertise regarding brass processing, we would be happy to arrange a training session for the team responsible at your company. Whether on-site or online – you can always rely on Hatebur’s proven expertise.