Melting and casting processes of CuZn40Pb2 alloy carried out with two types of casting alloys depending on charge materials and the casting parameters. The first alloy produced by using 100% recycles as charge materials. CuZn40Pb2 alloy recycle of gas valves for about 3000 kg are sequentially charged into coreless induction furnace. The melting point of the alloy mixture is located between 875 and 890˚C according to equilibrium diagram of copper-zinc alloy [11] . Temperature of molten alloy increased to 1050˚C and then chemical composition of alloy is estimated. The molten alloy temperature increased again to 1100˚C as pouring temperature before pour the melt into casting mold of a vertical semi- continuous casting machine. The molten alloy in casting mold covered with powder flux called “Cuprit 103” which is a white powder used as a protective cover on molten metal during the casting process. This protective cover will prevent any contaminations and will produce oil lubricant for mold liner after melt by molten metal [12] . The casting parameters used for this alloy are illustrated in Table 2 which adopted according to the technical knowhow of the supplying company.

The second alloy produced by using 70% recycles in addition to 30% of pure materials such as Cu, Zn and Pb added as charge materials. The production process for the second CuZn40Pb2 casting alloy is performed by repeating the same production processes adopted for the first alloy except some changes adopted in casting parameters as illustrates in Table 2. The final products of

casting processes are two strands of leaded brass alloy billets of 180 mm diameter and 6000 mm length.

Samples of 180 mm diameter and 300 mm length prepared from the previously produced castings billets of the two alloys types. These samples are heated by induction furnace before extruded. Extrusion process carried out experimentally under two different extrusion conditions cases Table 3, to produce two extruded leaded brass rods of 32.2 ± 0.2 mm diameter in each extrusion action. The extruded rods after pickling and oxidation removing are cold drawn by hydraulic draw bench to produce (Ø 30 ± 0.1) mm diameter of straight leaded brass rods.

The above mentioned fourteen samples (see Table 4) collected after casting, hot extrusion and cold drawing production processes under different conditions are grinded and polished carefully. A programmable hardness device (AFFRI 251 VRSD) is used to check and calculate the hardness of samples. Brinell hardness measured for each sample using 5 mm diameter ball indenter and an applied load of 62.5 N. The indenter mark pictures and diameters are calculated by optical lenses which equipped with hardness device, and then the hardness values are estimated and displayed onto the device screen. For each sample, three hardness measurements are taken and averaged to reflect its hardness value.

The tensile tests are accomplished for hot extruded and cold drawn rods sam-

ples. Standard tensile test samples are machined according to ASTM E8M [13] on turning machine (VDEST-AIRINE, DA 300 MASEHINE type), and then grinded with abrasive paper of grade 2000 μm. Tests carried out at Mechanics of Materials Laboratory-American University-Cairo-Egypt, using a programmable tensile test device (INSTRON 3382 type) which has a capacity of 100 KN. Two groups of tensile test specimens are considered. The first group contains four specimens of 9 mm gage diameter while the other consists of four specimens with 6 mm gage diameter. The ultimate tensile strength and elongation of samples measured and the stress-strain curves are obtained.

This test is performed only for the eight specimens obtained from the extruded (specimens 7 to 10) and cold drawn (specimens 11 to 14) processes after their fracture under the tensile test process. The micro-hardness values for the samples are checked using testing device LECO CORPERATION type, model 251 VRSD, 115\230 Volt. The load used is (100) gf and 10 seconds as dwell time. The test locations are selected on the surface and center of samples to explain the difference of hardness values between these locations. Three points of test values for each location on the sample are measured and then, the averages of these hardness values are estimated.

Table 5 presents the Brinell (HB) and Vickers (HV) hardness results for the collected specimens at different production stages. Noting that, Vickers hardness (HV) values obtained from Brinell hardness (HB) values according to ASTM E140-02 [14] . Moreover, Figure 1 shows the hardness values of all tested speci-

mens which provide a rapid and complete comparison between the effect different production stages on the product hardness. These results explain that, the hardness of the first three specimens (i.e. 1, 2 and 3) which taken from casting process are more than other samples due to the effect of increasing in some impurities such as iron (Fe) and silicon (Si). The increase of these impurities leads to refine the grain size of these castings and therefore, increases the hardness values. Also, the microstructure of materials influences the properties of the material and variation in microstructure can significantly change the strength, toughness and hardness values [8] . The reasons of impurities rise are due to using the whole charge elements from brass valve recycles. Sample 3 has the highest hardness value compared to the other samples due to its location into the chill zone area of casting billet. The hardness values decreased in extrusion case as in samples 7 to10 due to the rise in temperature of billet castings during hot extrusion which leads to enlarge the sample structure. The hardness values are increased again during the cold drawing process due to the work hardening process and dislocation density increases which agree with the results of [15] .

The micro-hardness test results of extruded and cold drawn samples after fracture by tensile test illustrate that, all hardness values are higher than other samples before tension due to the effect of work hardening. In same time, the hardness values are increased from extrusion to cold drawing processes due to the same reasons mentioned above. The maximum micro-hardness value (i.e. 198 HV, see Table 5 and Figure 2) is appeared in sample 12 produced from 100% recycle and formed by cold drawing process. The comparison between the micro-hardness values in surface and center of tensile test samples (Figure 2) illustrate that, all hardness values in center are more than that in surface. The reasons for this difference can be explained by that the sample grain structures in center are small equiaxed grains, while the circumferential grains are larger due to the fact that the extrusion, drawing and may be torsion during tension makes the circumferential strain degree higher and microstructure finer. In addition, the work hardening of samples during tensile test process also contributed in these differences in micro-hardness values. These differences in hard

ness values between the center or circumferential hardness values and the radial or center hardness values supports also the results obtained by Li et al. [16] . Moreover, the differences in hardness results can be verified by microstructure observations.

Figure 3 and Figure 4) and also Table 5 illustrate the results of ultimate tensile strength and elongation percent of extruded and cold drawn leaded brass samples. It can be noted that, the maximum ultimate tensile strength of 459 MPa is appeared for the 8^th sample (Figure 3). The increasing in these values can be due to the strain hardening. In addition, this sample is already taken from the first alloy that produced from 100% recycle, which included some percentages of impurities as Fe and Si; therefore, the mechanical properties as tensile strength can be slightly increased which agree with the results of Jha et al. [17] . The best ultimate tensile strength is appeared by the14^th sample due to using the mixture of pure materials and recycle into melting charge, and due to the cold drawing

process. The minimum value of tensile test is illustrated by the 10^th sample, while the elongation appears of high limit in the same sample.

The elongation values for the extruded and cold drawn samples are affected by the initial charge and the parameters adopted for each stage in the production process. Figure 4 shows the percentage elongation values of extruded and drawn leaded brass alloy specimens. It is worth to note that, the maximum elongation value appeared by the 10^th sample which produced from an initial charge contains 30% pure material using casting process followed by hot extrusion process.