Metal weight loss during melting (see weight loss) represents an immediate financial loss for the foundry. An increased metal yield of the melting furnace, on the contrary, means shorter periods for return on investment (ROI) and therefore represents an important investment criterion.
Shaft melting furnacemetal yield
For being able to deliver documented data material on the metal yield of a shaft melting furnace and to give substantiated advices, StrikoWestofen performed a metal balancing on a StrikoMelter® where all incoming and outgoing melt flows at the furnace were weighed. This was aimed at obtaining reproducible results on the metal yield, performing a comprehensive metal balancing and thus creating the basis for investment calculations.
The financial equivalent of a 1 percent melting loss with a melting performance of 1 t/h in three-shift operations amounts to approx. 100,000 euros/year. The calculation is based on the price of 2,000 euros/ton for aluminum block material (1st Quarter 2010) and a yearly melting time of 5,000h.
The examination results of a customer foundry revealed the results listed in Table 1. These values confirm the efficiency of this furnace type. It has to be noted that the metal yield was not determined on the basis of weighing scum taken out of the furnace, but on the basis of the difference between metal initial and output weight. By comparing the scum quantity a low amount of pickup was balanced which results from metal oxidation during the melting process. Altogether, a closed and complete metal balancing was achieved during the examination.
The examination result represent a reference value for standard alloys (note: Aluminum die casting alloys). In reality, the melting process often has to be interrupted. Under certain circumstances a lower return scrap quality has to be expected. The material is either impure or contains high amounts of flash. It is also important not to underestimate the effect on the metal yield of extracting metal on the fuse link by stirring. The evaluation of shift protocols revealed a metal yield which was 0.5 percent lower than the reference measurement. In case of pure block material the difference tends to be a bit smaller, in case of return scrap material a bit larger.
These briquetting presses combine a compact, space-saving design with a high throughput and almost 100% metal yield. The machine equipment can be configured individually according to customer wishes and needs. Briquette diameters of 45-100 mm and throughput rates of 60 - 600 kg/h enable a tailor-made briquetting solution (Hoecker Polytechnik GmbH).
As a result of the “Ordinance on Facilities for Handling Substances Hazardous to Water” (AwSV), which came into force on 01.08.2017, the classification and handling of substances which are hazardous to water has changed significantly. This waste with the highest metal yield can be optimally used by means of briquetting presses.
In addition to the significant volume reduction and the resulting minimized transport routes, the adhering cooling lubricants are pressed out to such an extent that the briquettes may be stored and transported in accordance with the new AwSV Ordinance. The briquetting presses are ideally suited to the processing of predominantly short, loose metal shavings from the mechanical processing of non-ferrous metals, steel and cast parts or other metals such as aluminum and magnesium.