Samet TÜRKMEN-030060143-7th week

1-BUFFİNG (finishing process)

NEW( better)

Buffing, which is refined polishing, consist of two steps cutting and coloring. Cuting,which is done with medium-fine abrasives such as tripoli or fine aluminum oxide, removes minute quantities of metal or surface imperfections like the tarnish found on brass. Coloring,however, removes no appreciable amount of metal, but blends the fine lines left by polishing and cutting.

(Rummell H. S., popular mechanics, p.203)

         

OLD:

The purpose of buffing is to improve the surface appearance of the metal and to produce a smooth, tihht surface. Buffing is used as a fina finishing opperation and is particularly adaptable to finishing a localized area of a part. Items such as body prostheses, pacemakers, and heart valves reauire a highly buffed, tight surface to prevent entrapment of particles. Close fitting parts for euipment, such as the modern guidance systems and electronics appilications, require highly polished surfaces obtained by buffing. In addition, sheet sizes too large to be proccesed by other abrasive finishing methods, such as mass finishing or wet blasting, can be economically processed by buffing.

(Donachie M.J., Titanium: A Technical Guide, 2000, p.90)

2-Duplex materials(material)

New (better)

Duplex steels contain approximately equal amounts of the ferrite and austenite phases. They contain significant amounts of cromium, nickel and molybdenum. Nickel promotes the austenite phase, whilst cromium and molybdenum promote the ferrite  phase. Duplex materials combine high pitting resistance and high strength. Duplex finds wide application in aggressive environments, especially where high strengths are required, for example high pressure, high temperature wells.

(Bellarby J., well completion design, p.440)

Old

İn material science a combination of two materials bonded together in order to attain properties sperior to those produced with a single mel tor starting material.

(Christopher G. Morris, Academic Press dictionary of science and technology,page 694)

3-Brittleness: (features of material)

New

From the historical point of wiev, brittle fracture proved to be one of the most frequent and dangerous failure occuring in engineering practice. Besides the well known brittleness of utility ceramics and glasses,metallic materials may also exhibit intrinsically brittle proporties depend on temperature;there exists a critical temperature, the so called ductile-brittle transition temperature(DBTT) under which metarial is brittle.

However, brittleness is often induced by other effects such as flawed material processing or segregation of deleterious impurities at grain boundaries.

(Pokluda J., Micromechanisms of fracture and fatigue, p.73)

Old (better)

Brittleness is the property which renders substances easily broken, or separated into irregular fragments. This property belongs chiefly to hard bodies.

It does not appear that brittleness is entirely opposed to elasticity, since in many substances, both these properties are united. Glass is the standard, or type of brittleness, and yet a ball, or fine threads of this substance are highly elastic, as may be seen by the bounding of the one, and the springing of the other. Brittleness often results from the treatment to which substances are submitted. Iron, steel, brass, and copper, become brittle when heated and suddenly cooled, but if cooled slowly, they are not easily broken.

(Comstock J.L., A System of natural Philosophy: in Which The Principles of Mechanics, Hydrostatics, Hydraulics, Pneumatics, Acoustics, Optics, Astronomy, Electricity and Magnetism, page 22-23)

4-Gasketing (plastic technology)

New(better):

Gasketing materials are used for sealing joints between parts to prevent leakage of gas or liquid. Many different plastics are used for gaskets depending on whether heat oil or chemical or some other property is primarily required.

Gasketing materials are generally preformed elastomers that are avainle as o- rings, rope, and other convenient shapes. However ,sealants can be used to make formed-in-place gaskets.

Two types of sealants are conventionally used for formed-in-place applications. These are room temparature curing silicones and anaerobic sealants.RTV( room temperature vulcanizing silicones) are generally used in joints where movement is required.

(Harper C. A.,Petrie E. M.,plastics materials and processes:Aconcise encyclopedia, p.227)

Old:

The gasketing technology is known, from the material point of view, as Foam in Place Material (FIPM) technology. A Foam-in-place material is a foam which is applied to a substrate as a liquid or semi-liquid and cures to a solid on the substrate. The technology involves two-component formulations, such as Polyurethane or Silicones. The liquid or semi-liquid material must be applied to the substrate very accurately since curing will occur, and is mostly applied by robots.

(UTECH Asia'99, March 16-18, 1999, Singapore, Elastomer Paper 7, p. 7)

5-Cupola( manufacturing process/cast iron)

New(better)

Production of pig iron by blast furnaces gave birth to the iron foudry. In the beginning, pig iron was used for making iron casting. With the advent of time, the use of iron casting become more common and gave birth to smaller shaft furnaces. Cast irons produced in smaller shaft furnaces also possess better properties. This small shaft furnace is known as a cupola.

Cast iron produced in cupola possess the following advantages:

1-     Molten metal in the ladle from the cupola can be tapped at regular intervals.

2-     The cost of melting is low.

3-     The control of chemical composition is better.

4-     Temperature control is easier.

5-     It consumes abundantly available and  less expensive fuel.

The main disadvantage of the cupola is that it is not possible to produce iron below 2.8% carbon in this furnace. Sufficient quantity of alloying elements like aluminium and molbdenum are also lost in the cupola. For producing white cast iron, the duplex process is employed. First cast iron is prodused in a cupola and the refining is carried out in an open hearth or electric furnace to lower its carbon content.

( Bawa H. S., manufacturing processes, p.50)

Old

Heat is provided externally ( for example, by electric, gas , or oilheating), internally(as by electic induction) or, only for cast iron, by mixing the fuel with the charge itself. CAst iron is usually melted semicontinuously in a vertical shaft furnace (cupola); lining of the cupola with a refractory is being abondened in favor of water-cooled steel jackets. The charge is mixe

d with coke and some minerals(primarily limestone, CaCO3), and hot air is blown through the column. Coke burns to give heat and is also a source of carbon for the cast iron. The liquid metal is tapped at the bottom, seperately from the slag which is formed by the limestone with nonmetallic contaminants and metal oxides. In the duplex process, the liquid metal is tapped into an electic holding furnace where alloying and suğerheating is also practiced.

(Schey, J., A., Introduction to Manufacturing Processes, 2nd Edition, pg.148-149)