Historical development of powder metallurgy

Historical development of powder metallurgy Introduction The powder metallurgy has long time history in human being development. As we know, Powder metallurgy is a forming and fabrication technique consisting of three major processing stages. The first stage is the formation of the primary material which is physically powdered, and then divided into many small individual particles. Next, the powder is injected into a mold or passed through a die to produce a weakly cohesive structure (via cold welding) which is very near the dimensions of the object ultimately to be manufactured. This method is very useful when we come across those products which need high accuracy dimension and tight tolerance in dimension. Two main techniques used to form and consolidate the powder are sintering and metal injection molding. However, recent developments have made it possible to use rapid manufacturing techniques which use the metal powder for the products. Because of this technique the powder is melted and not sintered. Thus, better mechanical strength can be accomplished. History The history of powder metallurgy and the art of metals and ceramics sintering are intimately related. Sintering involves the production of a hard solid metal or ceramic piece from a starting powder. There is evidence that iron powders were fused into hard objects as early as 1200 B.C. In these early manufacturing operations, iron was extracted by hand from metal sponge following reduction and was then reintroduced as a powder for final melting or sintering. Powder metallurgy has been called a lost art. Unlike clay and other ceramic materials, the art of molding and firing practical or decorative metallic objects was only occasionally applied during the early stages of recorded history. Sintering of metals was entirely forgotten during the succeeding centuries, only to be revived in Europe at the end of the 18th century, when various methods of platinum powder production were recorded. Metal powders such as gold, copper, and bronze, and many powdered oxides were used for decorative purposes in ceramics, as bases for paints and inks, and in cosmetics since the beginnings of recorded history. This was because most of the decorative apparatus like necklaces, ear rings at that time are mostly small in size especially for cosmetic purpose. Usually those iron oxide are use as pigment for the decorative equipment to make the looking more attractive and creative. Powdered gold was used to illustrate some of the earliest manuscripts. It is not known how these powders were produced, but it is possible that some of the powders were obtained by granulation after the metal was melted. Low melting points and resistance to oxidation (tarnishing) favored such procedures, especially in the case of gold powder. The use of this method for pigments and decorative purpose cannot truly consider as true powder metallurgy. This is because the true powder metallurgy is the production of powder and the consolidation of it into solid state using pressure or heat at the temperature below the melting point of the major constituent. However, early man learned by chance that particles of metal could be joined together by hammering, resulting in a solid metallic structure. In time, man learned how to build furnaces and develop temperatures high enough to melt and cast metals and to form lower melting alloys, such as copper and tin to make bronze. As the introduction of new material coming in, metal like platinum which brought by the conquistadores from South America, this metal could not be melted, but the early part of the 19th century workers in England, Spain, and Russia developed similar process for making wrought platinum. Another important product is tungsten wire filaments, which is pioneered in USA. Unlike the earlier products that were made from powder because the metal concerned could not readily or at all be processed by melting. This are made by powder metallurgy is because of the special properties that result. With this method, it can be arranged that a considerable volume of interconnected porosity remain. Besides, if the gas is extracted from the pores and the parts are immersed in lubricating oil, the pores are filled with oil. Such parts are used as bearing in most small rotating or reciprocating machinery which no further lubrication during the life of the equipment. After the First World War, another powder metallurgy product came out. In 1925, a German company F Krupp, was granted a patent for a process and product consisting of tungsten carbide particles held together by a cement consisting of metallic cobalt. This material is used originally in the form of wire drawing dies, for tungsten as a replacement for diamond dies. Since powder metallurgy come to human being technology, it bring a lot of consequence and change in metal industry. Advantages of Powder Metallurgy There are advantages and disadvantages in powder metallurgy. The advantages are main from technical and commercial aspects. The technical and commercial advantages of producing parts from powder can be summarized as below: production to near net shape. This means that the product can have very tight tolerance of dimension. The accuracy of the dimension of product can be reach higher degree using powder metallurgy. few or no secondary operations. Usually powder metallurgy didnt required secondary operation such as cutting. high material utilization from low levels of in process scrap For example, those scrap are being recycle used by crushing it into powder and reform new product using powder metallurgy. homogeneous powder, and hence part, chemical composition due to absence of gross solidification segregation and uniform pre-alloyed powder particle composition unique compositions and structures possible as there is no melting e.g. Introduction of specific particles to give special properties such as silica and graphite in brake pads, and porosity in bearings for oil retention non-equilibrium compositions possible e.g. Copper-chromium alloys metallurgical structures are usually fine and isotropic e.g. Carbide distribution in atomized high speed steel powder parts Disadvantage of Powder Metallurgy Inevitability there is some limitations including: costs of powder production. limitations on the shapes and features which can be generated e.g. The process cannot produce re-entrant angles by fixed die pressing or radial holes in vertically pressed cylinders the size will always change on sintering. This can usually be predicted as it depends on a number of factors including as-pressed density which can be controlled potential workforce health problems from atmospheric contamination of the workplace. Powder particles size can be very small up to micrometer measurement scale. So it is very hard to see using eyes and prevent it from taking inside of lungs.

The Murder of Emmett Till

Clearly, the murder of Emmett Till was a major part of the Civil Rights Movement because it had opened the eyes of citizens who had believed there was no difference living as a person of color than there was living as a white person. The Emmett Till case was about a young boy who was visitings some relatives up in Money, Mississippi. He rode in a car with a few other cousins and family members around his age (14) to Bryant's Grocery and Meat Market, when one of Emmett's relatives had recommended that he attempt to get with the clerk of the store. However after attempting to flirt with her he left unsuccessful and gave her a kiss on her cheek. The clerk then told her husband about the encounter and how she was approached as Emmett made unwilling advances upon the clerk. As Emmett left the store he had bragged about how he â€Å"Got a Date† with the clerk, his relatives were instantly worried for his safety warning him that it was dangerous to make advances on white people, especially women. After being taken to the home in which his relatives lived in, there was commotion at the door, then all of a sudden. The clerks husband and his brother in law had barged into the room where Emmett was sleep and drug him outside and beat him to near death. They had thought of taking him to a hospital and giving them a fake story about how they found him beaten up, but decided he was a lost cause and tied a cinder block to his ankle and dropped what was left of him down the Tallahatchie River to sleep with the fishes. After three days of the kidnapping of Till they had found his body in the Tallahatchie River, the only way they knew it was him was by the ring on his finger, a ring his father had given to him. The news had spread around Till's family quickly, and his mother demanded his body be brought back to chicago so he can be buried properly. She had also requested that the funeral had an open casket to show the 50,000 people that attended the funeral just what those men had done to her son. She had later set up a trial to put the two men who had murdered her boy behind bars, however after hours of the court arguing who did what and who didn't do what, the two men were found not guilty for the murder of 14 year old Emmett Till

My View of the World Essay

As I stand here looking over the lush green foliage of thousands of trees, I glanced down toward the base of the mountain to see curvy, windy roads, weaving in and out between tiny little box houses, plotted around here and there. I can see for miles and miles, the views are breath taking. That’s mostly why people come to see me, to look out with me, to see the fantastic views. My arms are sore from standing here for about 75 years, just doing nothing but wondering. For many months I have started to think what is beyond the horizon of the sea. There could be a whole new world over the edge. Is there even an edge? Who knows? Years ago those little things climbed on my feet, just to get a better view or to pose in front of a compact box, with a blinding flash for a couple of seconds, but now there are large metallic fences at my feet. This is predominantly because I am old, weary and wearing out so I need protecting. People get here in many different ways, clear boxes which travel up and down continuously, moving stairs, or climbing 222 steps reaching the summit, exhausted. Oh yeah! I forgot to say about the odd people that walk all the way up the ridge of mount Corcovado who wear small shorts, long pulled up socks, big chunky boots, weird hats and really, really big bags on their backs. They come in there hordes, they come in all shapes and sizes; big ones; small ones; fat ones; thin ones; some are noisy; some are quiet; some just scream and laugh; some are in awe of me and gaze up at me, as I gaze out at the horizon. These people see me as a god, but if only it were true because all I want to do is just fly to the moon, to the white wonderful wide space, where I could rest my sore painful arms and legs. No one knows the pain I’m in or even know I have any feelings. I remember the journey of how I came to be here. I was created by a local engineer called Heitor da Silva Costa. He made me out of reinforced concrete and layers of soap stone. Firstly I was going to be made out of steel but that wouldn’t of had much of a chance against extreme weather conditions. I was built in small chunks and slowly brought to the top by a struggling train on the Corcovado Rack Railway. Then I was pieced together bit by bit, slowly rising above the ridge to embrace the people of the world. Through my amazingly large nostrils I can smell the wondrous cuisine from the land below swirling and rising up the mountain side. Just after dark the surroundings black out and all attention is drawn towards the bright lights of the city. Although no one else sees it, it’s not all happiness up here. I have seen many things in my life like robbery’s, suicides, murders, but what always happens almost every night is groups of people sell drugs and sit there injecting liquids into their arms, snorting dust and sniffing corrosive fumes of acids. The fumes are so strong even I get a headache and my heads made out of concrete! It is disgusting what they do, but it is what they want to do, and what could I do any way. As dawn emerges it makes up for the previous night. The sun rises and a new day begins. In the early morning, the mountain air is fresh and crisp; the sun rises leisurely, bringing a slow warmth to the city. The most beautiful part of the day is now, when it is peaceful and you can hear the chirping of the birds below. The heat from the sun breaks through my layers of soap stone reaching into the hard cold concrete inside.

Computers and Homeland Security Essay - 836 Words

Computers and Homeland Security Homeland Security is one of the most important departments in the United States. The United States Department of Homeland Security job is to reduce our vulnerability to terrorism and lead a national effort to help prevent terrorist attacks on our nation (Computer Concept, pg. 50). As technology evolves over the course of time, computers end up playing a crucial role in homeland security. Computer systems are used throughout everyday lifestyles in order to make difficult tasks much simple. The government utilizes such systems in order to support their efforts in locating suspected terrorists throughout U.S. boundary lines. There are several software programs, which can be†¦show more content†¦One negative component of computers is that hackers often find methods to penetrate the information barriers. â€Å"Homeland security agencies are trying to secure the national computer with programs that target individual computer owners, corporate computer networks, internet service providers, and communications carriers† (Computer Concepts, pg. 51). The main purpose of the program US-CERT is to reduce the vulnerability of computer systems. Hackers usually try to harm computers by placing viruses or worms in them, but the US-CERT program helps reduce the damage of these viruses and worms. US-Cert reduces damage by sending mail to the computer wh en threats and vulnerabilities are found. The National Security Agency â€Å"coordinates, directs, and performs highly specialized activities to protect U.S. government information systems and produce foreign signals intelligence information† (http://www.nsa.gov/about/index.cfm). Without the NSA the systems of the government would not be able to function as well as it does. The NSA has been with computer security research, investigating a variety of security topics. This system helping the government must be able to separate information between confidentiality and integrity to help provide system security. An operating system security mechanism makes the separation between the two. Unfortunately, many operating systems the security features to make the separation. Since many systems lack the ability toShow MoreRelated Computers and Homeland Security Essay735 Words   |  3 PagesComputers and Homeland Security After the terrorist attacks on September 11, 2001 security became a major concern for citizens and of course lawmakers. Unsure of what could happen next we were all afraid. Homeland Security encompasses policies, laws, organizations, and procedures designed to protect the rights and freedoms inherent in the US Constitution. Homeland defense which is sometime interchanged with Homeland Security deals with extra-territorial threats and preemptive operationsRead MoreEssay about Computers and Homeland Security Unite794 Words   |  4 PagesComputers and Homeland Security Unite Homeland security was created by the Bush administration in 2001 as a result of the September 11th events. It is an independent agency in the United States whose mission is to protect the nation from potential terrorist attacks. Together the agency is made up of twenty two agencies and 180,000 employees. Their main focus is â€Å"intelligence and warning; boarder and transportation security; domestic counterterrorism; protecting critical infrastructure; defendingRead MoreAmerica And Its Homeland Security Online Essay1587 Words   |  7 PagesAmerica and Its Homeland Security Online Abstract: Everyday security is provided by the states and federal government. These tasks get more difficult as new technology introduces itself. Cybersecurity is one of the most popular security sectors in today’s world. There is not only cyberbullying going on in the world. Terrorism can be planned and sent from person to person over the internet. People’s identities are being stole to help carry out these terrorist acts and this is just the being of itRead MoreElectronic Mail Acceptable Use Policy1054 Words   |  5 PagesOperation of Information Systems/Computers directive. The Department of Homeland Security, Management Directive System MD Number: 4900 â€Å"directive establishes the Department of Homeland Security (DHS) policy for the use and operation of DHS information systems and computers by individual users† (Department of Homeland Security, n.d.). Department of Homeland Security, Management Directive System, MD Number: 4500.1 relates to DHS E-Mail Usage (Department of Homeland Security, 2003). This directive establishesRead MoreThe Impact Of Legislation On An Organization854 Words   |  4 Pagesdecade, every individual, and organizations did paperwork with a typewriter and a cabinet or book shelf to store their files. These days our old ways is been replaced by computers and databases or cloud. This in order words mean that government organization like the department of veterans affairs do their workload with computer, databases as to the old days. This modern change makes some organization vulnerable to attackers. In other to reduce these treats from the attackers, cybersecurity rulesRead MoreThe Internet And Its Effects On The World Nation Itself853 Words   |  4 PagesAs we all known, now in days almost everything that we see and everything that we do is throughout an electronic devise. No matter what small little thing, almost everything that you do is from a computer. For instance, to communicate with a family member (cellphone), to send a via-text, to check your e-mails, to watch television, almost everything is throughout a devise. For this same reason, government has to make sure that these devises are protected from any predator that would do bad with thoseRead MoreThe Department Of Homeland Security1602 Words   |  7 PagesDepartment of Homeland Security The Department of Homeland Security is an agency made up of 22 different federal agencies which were combined in an effort to streamline the United States effectiveness in defending our nation. The core mission of the Department of Homeland Security include prevent terrorism and enhancing security, secure and manage our borders, enforce and administer our immigration laws, safeguard and secure cyberspace, ensure resilience to disasters (Department of Homeland Security, 2015)Read MoreCritical Infrastructure Protection1106 Words   |  5 PagesProtecting an infrastructure takes an important security initiative called Critical Infrastructure Protection (CIP). The United States critical infrastructure is protected by the Department of Homeland Security. Examine three areas of the Department of Homeland Security: mission, operations and responsibilities The first area is the Department of Homeland Security’s mission. The Department of Homeland Security (DHS) was created in 2002 by the Homeland Security Act. In 2003 the DHS started their operationsRead MoreProtecting Yourself Against the Treats of Cyberspace1022 Words   |  5 PagesCyber Security It seems like everyone in today’s society has access to a computer, a cell phone, or some other type of technology that allows information to be passed from one person to another through space. With your private information out there in cyberspace, clever thieves are finding ways to access your personal informational and to steal from you without you even knowing about it until it is too late. The thieves are taking your personal data and using it to gain access to your accountsRead MorePersonally Identifiable Information Essay1071 Words   |  5 PagesUNDERSTANDING OUR RESPONSIBILITY REGARDING PERSONALLY IDENTIFIABLE INFORMATION IFSM 201 JULY 22, 2012 Abstract Anyone who uses computer technology today accepts the fact that their Personally Identifiable Information (PII) may or could be transmitted, collected, and used to benefit the one who receives that information. It is our responsibility to know what PII transmissions are being made available for public use over the web. Understanding all the aspects of PII and the approaches that are