An Inuence of Slag Rening on the Structure and Mechanical Properties of the Brass CuZn39Pb2

The results presented in the dissertation show the inuence of a kind and concentration of the ux added during the process of the lead brass smelting on its structure, chemical composition and mechanical properties – hardness and strength. A positive i rening, structure, mechanical properties, brassnuence of the rening and modication process manifested in an improvement of mechanical properties as well as an increase of the structure, chemical composition and mechanical properties homogeneity in the entire volume of the ingot has been proven.


Introduction
Due to its properties (malleability, ductility, corrosion resistance), brass is one of the most common alloys. Brass and its alloys belong to materials which can be recovered from recyclable resources (production wastes, scrap). Depending on the level of the copper scrap purity and its chemical composition dependability, it can be smelted directly or it must be re ned and modi ed during the smelting process [19PS]. The re ning aims at eliminating the unfavourable additions and, as a result, at the improvement of mechanical properties. Nowadays, the re ning and modi cation play the key role in the processes of manufacturing metals and alloys with high mechanical properties [1][2][3][4][5].
Modifying metals and their alloys with microadditions of selected elements enables a positive impact on a primary structure of alloys made in a process of solidi cation. The studies of the authors [1,6,7] have shown a signi cant complexity of the brass alloys modi cation processes. On account of the environmental protection [1,5,7], to reduce the amount of harmful substances emerged in the re ning and modi cation process, an attempt to intensify the impact of chemical substances on an alloy by their appropriate selection should be made [1,5].

Research Methodology
In the research, the copper CuZn39Pb2 has been used. Its chemical composition, in accordance to the standard, has been presented in table 1. The smelting has been proceeded in industrial conditions in Radne 1500 coreless induction furnace. The feedstock was the process scrap from the material removal processing, containing the cooling lubricant.
The single kiln charge was 1200kg.
The places in the smelt where the samples for the research have been cut out from have been presented in Fig.1.
The structure of prepared microsections has been examined by an optical microscope AXIO Observer A1m in six zones with zooms 50-1000x. The quantitative and qualitative research has been done on the scanning microscope JSM-5600LV by JOEL, equipped with a EDS 2000 X-ray analyser by IXRF SYSTEMS.

The Research Results
The research of the re ning in uence on the brass structure has given the results shown in g. The analysis of the chemical composition the samples has been presented in the g. 3 -11.
The percentage difference in the basic alloy elements for particular smelts, for the samples from different areas of the ingot, has been presented in the g. 12-14.
As shown in the pictures above, the alloy re ning contributed to the increase of the chemical composition stability in the entire volume of the ingot. The closest to the normative and the most stable chemical composition has been reached for the ux added to the smelt in the concentration of 0.15%.
The hardness of the particular samples has been measured and the results have been shown in the g. 15.
As seen in Fig. 15, in the zone 1 there is an essential difference in the hardness of the samples from different smelts. The highest hardness in this zone, discovered in the sample cast without the ux, was caused by the increased thickness of the frozen crystals zone. The increased hardness in the zone of the casting skin (the surface zone of the cast), can result, in case of mechanical processing, in a faster cutting tool wear. In the rest of the zones considered, the hardness values have not shown any signi cant differences.
The results of the strength tests have been presented in the g. 16.
On the basis of the data received by the tensile testing it may be stated that materials emerged in the re ning process are characterised by higher strength parameters. The differences in the parameters of the strength properties for the samples from the smelting with the use of the ux are insigni cant. However, they are noticeably higher than parameters for the sample created without any modi cation.

Conclusions
As a conclusion from the research done, what must be highlighted, is the signi cant and positive impact of the Topbal Z ux on the re ning process and receivedmetallographic structures, characterised by higher homogeneity and grain re nement. The re ning contributed also to an improvement of mechanical properties by increasing the strength of the alloys received as a result of the re ning. Taking the further alloys mechanical processing into consideration, modifying the alloy with the ux concentration 0.1% of the kiln charge has proven to be the most favourable. The surface layer expansion, characterised by higher hardness which may result in the increased cutting tool wear, has not been observed at this concentration. Compliance with ethical standards All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript. The authors give their consent for publication.