Papers by Keyword: Green Strength

Abstract: In this paper we present the production of alternative industrial materials from the mining waste in the form of tailings, this study was made with the tailings of Dos Carlos, establishing 4 sampling zones, dividing them into three strata in the bottom, middle and top. The sampling method used is quartering, to homogenize the material and anticipate the possible use of it as a building material, having for this purpose 12 ceramic mixtures for subsequent treatment. Chemical composition was determined as 70.43% SiO₂, 7.032% Al₂O₃, 2.69% Fe₂O₃, 0.46% MnO₂, 3.98% K₂O, 3.34% CaO, 2.50% Na₂O, 56 grams per tonne of Ag y 0.6 grams per tonne of Au. In the mineralogical characterization the tailings presents silica, albite, berlinite, orthoclase and potassium jarosite as the main mineral phases, among other mineral phases in lesser concentration such as gypsum, calcite, anorthoclase, pyrite, sphalerite and galena. The determinations of the tailing material granulometry in the range of 60% in a size less than 270 mesh (53 μm). Afterwards, the alternative industrial materials were produced by using the tailings and heavy clay in order to give the composite a good green strength and plasticity during development, but above all to give it a compressive strength similar or higher than that of products derived from conventional processes. Keywords: Tailings, green strength, compressive strength, plasticity, heavy clays, alternative industrial materials.

Abstract: In this study, the ejection stage during the densification process and the mechanical strength of green (unsintered) compact were studied for the binary powder compact of iron and micro crystalline cellulose (MCC). The mass percentage of MCC powder were varied between 0% to 60% of the total mass composition of the iron and MCC mixture. Three different compaction load of 30kN, 60 kN and 90 kN were applied during the compaction process. The tensile strength of the green compact was determined by conducting diametral compression test where the green compact was loaded until fracture. From the compaction experiment, green compact with 60% MCC and 40% iron is the least friable which leads to coherent and well compactable powder. This composition also results in the green compact with the highest tensile strength.

Abstract: Two different types of un-vulcanized natural rubber, air dried sheets (ADS) and SVR-3L block rubber, were investigated by a new testing method and the results are compared with other mechanical properties. It was found that green strength is strongly reduced if the sample is ther­mal­ly treated before testing. Presumably, the decrease of strength is caused by a decrease of branch points, mainly composed of phospholipids, which are linked to the a - terminal groups of the rubber molecules. The existence of two different types of branch points is indicated by relaxation spectra, obtained from temperature scanning stress relaxation (TSSR) measurements.

Abstract: “Shikoko” clay and dredged river sand from Warri, Nigeria were investigated for their use in synthetic sand moulding. Shikoko is a local name for organic clay that dries appreciably to a brownish gray, leather-like consistency. The clay was initially tested for organic matter content, natural water content, particle size distribution, consistency limits and linear shrinkage. The base sand dredged river sand from the same town - was tested for specific gravity, and grain size characteristics. Tests showed that the best mix with the clay was at the binder contents of 13, 17, 33 and 50% of the dry weight of the sand. The synthetic sand mixture was tested for the dry and green compressive strengths, and green permeability. At clay contents of 13 and 17 %, the green and dry compressive strengths of the synthetic mixtures at 5, 10, 15 and 20% moisture contents compared well and were at times higher than the corresponding values for synthetic moulds used in founding. Test results indicated that the synthetic mixture can be used for light casting and in non-ferrous production.

Abstract: The green strength of a powder compact results from the mechanical interlocking of the irregularities on the particle surfaces. During compaction, particle rearrangement, plastic deformation and particularly surface deformation of powders occur. Titanium powder is susceptible to interstitial element contamination, which may lead to solid solution strengthening of the particles and/or the formation of non-metallic compounds on the surface. However, the influence of these various impurities, namely oxygen and nitrogen, on the green strength has not been investigated. This work investigates and quantitatively evaluates the factors influencing the green strength of the powder compacts. The indirect tensile test was applied for the determination of the green strength of the powder compacts, and test results were compared to that of a more conventional 3-point bending test. The substantial dependence of green strength on both the amount of impurity element in the core of the powder particles and the compaction pressure is demonstrated. The effect of the surface condition of the powder particles on green strength is also reported.

Abstract: High velocity compaction (HVC) is a production technique with capacity to significantly improve the mechanical properties of powder metallurgy (PM) parts. Several investigations indicate that high-density components can by obtained using HVC. Other characteristics are low ejection force and uniform density. Investigated here are green body data such as density, tensile strength, radial springback, ejection force and surface flatness. Comparisons are performed with conventional compaction using the same pressing conditions. Cylindrical samples of a pre-alloyed water atomized iron powder are used in this experimental investigation. The different behaviour of HVC-pressed green bodies compared to conventional pressed green bodies are analysed and discussed. The HVC process in this study resulted in a better compressibility curve and lower ejection force compared to conventional quasi static pressing. Vertical scanning interferometry (VSI) measurements show that the HVC process gives flatter sample surfaces.

Abstract: New P/M lubricant formulations implement micron-sized (“micronized”) cellulose particles (MCP) to create MCP-enhanced lubricants. Surprising increases in green strength, up to 70% for iron and even higher for stainless steel are obtained with standard transverse rupture bars shapes made with 0.75 wt-% additive concentrations in iron (MPIF F-0000) and 316L stainless steel powders in comparison with the same parts made under the same conditions with industry standard lubricantbinders of zinc stearate, ethylene-bis-stearamide (EBS), and oxidized polyolefin (OP) wax. Two specific forms of new MCP materials are used in these tests: micronized cotton fibers (MCF), and micronized starch particles (MSP). The findings support expectations of significantly increased process yields for green parts and related production cost savings.