This paper will discuss the production history, current challenges and the future plans for the PT Freeport Indonesia (PTFI) minerals district as it transitions from primarily open-pit production to a series of large volume caving mines. The Grasberg open pit commenced mining in 1989 and completed at the end of 2019, having mined over 1.37 billion tonnes of ore and having produced 27 billion lbs of payable copper as well as 46 million ozs of payable gold. In addition to the ore mined, the pit also moved over 3.4 billion tonnes of overburden during this timeframe. This paper discusses the rapid mining process, challenges encountered and the pivotal role the Grasberg open pit played in supporting the future underground era. PTFI has been cave mining since the 1980s and has ramped up production over time with a series of progressively deeper mining horizons in the East Ertsberg Skarn System (EESS). Currently, the Deep Ore Zone (DOZ) mine is in active production and is the third lift in the EESS. In 2004, an access development named the AB Adits commenced at a mining horizon approximately 500 m below the DOZ mine. This allowed the fourth lift in the EESS, the Deep MLZ (DMLZ) mine to be constructed. The DMLZ initiated caving in 2015 and is currently ramping up production. In addition, the AB Adits allowed timely access to the downward extension of the Grasberg ore body, and the Grasberg Block Cave mine initiated caving in 2018 and is also undergoing a rapid production ramp-up. These long-lived, high-volume caving operations will extend the life of the mineral district past 2040 with a plan to produce approximately 200 -250 ktpd at peak production rates. The paper will discuss the strategic plans applied to construct these large and long-lead projects and some of the challenges faced during the 16 years of pre-production, cave initiation and production ramp up. Critical topics such as rapid access, infrastructure construction, ground control, wet muck mitigation and seismicity are discussed in the paper, focusing on lessons learned and ongoing improvements.
Este é um artigo de acesso aberto distribuído sob os termos da Licença de Atribuição Creative Commons ExpErimEntação no Ensino dE Química
Esta pesquisa tem como objetivo avaliar o processo de oxidação térmica como uma forma de aumentar a resistência à corrosão do aço inoxidável. Próteses e instrumentais cirúrgicos produzidos em aço inoxidável foram expostos à atmosfera rica em oxigênio nas temperaturas de 300 e 400 ºC, pelos períodos de 30 e 60 minutos. Posteriormente, o material oxidado foi submetido a repetidos ciclos de esterilização em uma autoclave vertical, na temperatura de 127°C e pressão de 147,1 kPa. Os resultados foram analisados quanto à rugosidade, formação de descoloração e pites de corrosão. O processo de oxidação térmica mostrou efeito positivo em combinações de 300°C por 30 minutos e 60 minutos. Nessas condições, as superfícies analisadas apresentaram menor número de pites de corrosão, descoloração e riscos. Pode-se concluir que a oxidação térmica, um tratamento de fácil operacionalidade e baixo custo, pode melhorar a resistência à corrosão por pites de próteses e instrumentais cirúrgicos submetidos a repetidos ciclos de esterilização em autoclave.
Resumo Uma das principais exigências de uma prótese de quadril, além da biocompatibilidade, é que ela tenha um bom desempenho em fadiga. As propriedades de fadiga estão diretamente ligadas com a microestrutura do material, sendo assim, entendem-se as exigências microestruturais determinadas por normas para próteses. A microestrutura passa a ter um papel importante na qualidade desses componentes; e sendo ela diretamente influenciada pelos processos de fabricação precedentes, tais processos também devem ser rigorosamente controlados. Nesse trabalho foi analisada uma prótese de quadril, fabricada a partir de uma liga de aço inoxidável, que fraturou por fadiga durante o uso. A análise foi conduzida pelo uso de lupa, microscópio eletrônico de varredura, análise química e análise metalográfica. Foi verificado que apesar da análise química estar dentro dos limites determinados pela norma ABNT NBR ISO 5832-1, a microestrutura estava heterogênea, devido ao processo de forjamento, comprometendo o desempenho em fadiga do componente. Palavras-chave: Análise de falha; Prótese de quadril; Aço inoxidável ABNT NBR ISO 5832-1; Fadiga. THE IMPORTANCE OF MICROSTRUCTURE ON THE PERFORMANCE OF HIP PROSTHESIS Abstract One of the main requirements of a hip prosthesis, besides biocompatibility, is that it has a good fatigue performance. The fatigue properties are directly connected with the microstructure of the material, under these circumstances, is understood the standards specifications for microstructural in prosthetics. So, the microstructure becomes important in the quality of these components, and being it, directly influenced by the fabrication processes, such processes must also be rigorously controlled. In this study was analyzed a hip prosthesis manufactured from a stainless steel alloy that fractured by fatigue during use. The analysis was conducted by using a stereoscope, scanning electron microscopy, chemical and metallographic analysis. It was found that chemical analysis was as determined by ABNT NBR ISO 5832-1 while the microstructure was heterogeneous, due to the forging process, damaging the fatigue performance of the component.
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