Processes for Forging of Metals Dec16

Processes for Forging of Metals...

Processes for Forging of Metals Metal forging is a deformation process where metal is pressed, pounded or squeezed under great pressure into high strength parts known as metal forgings. The forging process is entirely different from the casting (or foundry) process, as metal used to make forged parts is neither melted nor poured as in the casting process. Forging is defined as a metal working process in which the specific shape of metal work piece is obtained in solid state by compressive forces applied through the use of dies and tools. During the forging process controlled deformation of metal takes place. Forging process is accomplished by hammering or pressing the metal.  In modern times, industrial forging is done either with presses or with hammers powered by compressed air, electricity, hydraulics or steam. All the metals and alloys are forgeable, but the forgeability rating of different metals and alloys can vary from high to low or poor. The factors involved are the composition, crystal structure and mechanical properties all considered within a temperature range. The wider the temperature range, the higher the forgeability rating. Most forging is done on heated work pieces. Cold forging can also take place at the room temperatures. Forging process is one of the oldest known metalworking processes with its origin about some thousands of years back. The process goes back to 8000 BCE and evolved from the manual art of simple blacksmithing. Traditionally, forging was performed by a smith using hammer and anvil. Using hammer and anvil is a crude form of forging. The smithy or forge has evolved over centuries. Then as now, a series of compressive hammer blows performs the shaping or forging of the part. Modern forging uses machine driven impact hammers or presses which deform the...

Impact Toughness Testing of Metals...

Impact Toughness Testing of Metals Metals undergo dynamic fracture under rapidly applied loads which are generally produced by impact or by explosive detonation. In comparison to quasi-static loading, dynamic conditions involve loading rates which are higher than those encountered in conventional tensile testing or fracture mechanics testing. Dynamic fracture includes two cases namely (i) a stationary crack subjected to a rapidly applied load, and (ii) a rapidly propagating crack under a quasi-stationary load. In both the cases the material at the crack tip is strained rapidly and, if rate sensitive, can offer less resistance to fracture than at quasi-static strain rates. As an example, values for dynamic fracture toughness are lower than those for static toughness as experienced in the testing of low carbon steels at different temperatures. Many structural components are subjected to high loading rates in service. They also are to survive high loading rates during accident conditions. This makes high strain rate fracture testing is of interest and components are to be designed against crack initiation under high loading rates or designed to arrest a rapidly running crack. Also, since dynamic fracture toughness is normally lower than static toughness, more conservative analysis requires consideration of dynamic toughness. Measurement and analysis of fracture behaviour under high loading rates is more complex than under quasi-static conditions. There are also several different test methods which are used in the evaluation of dynamic fracture resistance. Test methods based on fracture mechanics produce quantitative values of fracture toughness parameters which are useful in design. However, several qualitative methods are also been used in the evaluation of impact energy to break a notched bar, percent of cleavage area on fracture surfaces, or the temperature for nil ductility or crack arrest. These qualitative tests include methods such as...

Supervisors and their Role in the Organization...

Supervisors and their Role in the Organization Supervisor is a person who is in charge of, and coordinates the activities of a group of employees engaged in related activities within a unit of an organization. He is a front line manager and is responsible for getting the non-executive employees to carry out the plans and policies set by the management. A supervisor is also sometimes being called as a front line supervisor since he is the first link between the management and the non-executive employees. A supervisor plan, direct, motivate, and monitor the work of non-executive employees at the operational level of the organization. Supervisors are the first-level executives, since they have only non-executive employees reporting to them. Supervisors can also be second-level supervisors when they supervise a combination of other supervisors and non- executive employees. Place of supervisors in the organizational structure is given in Fig 1. Fig 1 Place of supervisor in the organizational structure The main job of a supervisor is supervision which is defined as instructing, guiding, monitoring and observing the employees while they are performing their duties in the organisation. The word supervision is the combination of two words, i.e., supervision where super means over and above and vision means seeing. So, supervision means seeing the activities of employees from over and above. Supervisors are member of management and hence they also carry out in the front line the so called four functions of the management namely planning, organizing, directing and controlling. Supervisors are leaders for their team. They play very important role in the organizational functioning. Their thinking and actions are to be professional and disciplined. They are to have positive approach to work environment.  They are to think in a systematic way. They need to approach the...

Processes for Casting of Metals Dec07

Processes for Casting of Metals...

Processes for Casting of Metals Casting of metals is a process of manufacturing materials made of metals. It is a forming process for the forming of hot liquid metals. It is the simplest, most direct route to a near net shape product, and often the least expensive.  It is a process, in which liquid metal is poured into a mould, which contains a hollow cavity of the desired shape, and then allowed to cool and solidify. The solidified part is also known as a casting, which is ejected or removed out of the mould to complete the process. Casting is very often used for making complex shapes which are difficult or uneconomical to make by other methods. The processes for the casting of metals (Fig 1) have two distinct subdivisions namely (i) non-expendable mould casting, and (ii) expendable mould casting. It is further broken down by the mould material, such as sand or metal, and pouring method, such as gravity, vacuum, or low pressure. Fig 1 Processes for the casting of metals Non-expendable mould casting processes Non-expendable mould casting is a casting process in which the mould need not be reformed after each production cycle. Non-expendable mould casting is a casting technique which has at least 4 distinct casting processes. These are (i) continuous casting, (ii) centrifugal casting, (iii) die casting, and (iv) permanent mould casting. This form of casting also results in improved repeatability in parts produced and delivers near net shape casting. Continuous casting process Continuous casting of metals can be defined as a refined process of casting for continuous production in high volume of metal shapes with constant cross-section. During the process, the pouring of liquid metal takes place into a water-cooled, open-ended copper mould. This allows a skin of solid metal being formed...