1. Rotary Evaporator
(Old)
Rotary evaporators are a common feature in most undergraduate laboratories. Their primary purpose is to remove solvent following a reflux, perhaps before crystallization of a reaction product. To operate the evaporator, we place the reaction solution in a round-bottomed flask while pressure inside the evaporator is decreased to about 1/30 x p0. The flask is then rotated. The solvent evaporates more easily at this low pressure than at p0 . The solvent removed under vacuum is trapped by a consider and collected for easy re-use, or disposal in an environmentally sensitive way.
(Monk P. M. S., Physical Chemistry: Understanding Our Chemical World, 2004, p.188)
(new/better)
A rotary evaporator is an instrument designed to distill a liquid under reduced pressure. It consists of a heated rotating vessel (usually a large flask), which is maintained under a vacuum through a tube connecting it to a condenser. The rotating flask is heated in a hot-water bath. The rotation provides enhanced heat transfer to the liquid inside, and also strongly reduces the occurrence of bumps caused by superheating of the liquid. The solvent vapors leave the flask by the connecting tube and rate condensed in the condenser section. The condenser section is so arranged that condensed vapors drain into another flask, where they are collected. It is an efficient way to rapidly remove large quantities of solvent. Rotary evaporation is mainly used to recover non-or semivolatile solutes in preparative chromatography and solvents for recycling purposes.
(Xing B., Senesi N., Huan P. M., Biophysico-Chemical Processes of Anthropogenic Organic Compounds, p.1772)
2. Surface hardening
(Old)
Surface hardening, a process that includes a wide variety of techniques, is used to improve the wear resistance of parts without affecting the more soft, tough interior of the part. This combination of hard surface and resistance to breakage on impact is useful in parts such as a cam or ring gear that must have a very hard surface to resist wear, alonf with a tough interior to resist the impact that occurs during operation. Further, the surface hardening of steel has an advantage over through hardening, because less expensive low- and medium- carbon steels can be surface hardened without the problems of distortion and cracking associated with the through hardening of thich section.
(Joseph R.D.,Surface hardening of steels: understanding the basics, page 1)
(new/better)
Surface hardening technology is a quite active field, whether in scientific research or in industrial production. In recent 20 years , the surface hardening technology develops rapidly because it can reduce the repair cost and is efficient to control and improve the wear resistance. Surface hardening technology can advance product quality (including repair quality) with surface plating technology and surface characteristic altering technology. It can attain special component, structure and surface performance with a variety of physical, chemical, electrochemical, mechanical or electronic technology, and meet special requests of parts.
(Luo J. , Meng Y., Shao T., Zhao Q., Advanced Tribology: Proceedings of CIST2008 & ITS-IFToMM2008, p.449)
3. Through hardening
(Old)
Through-hardening bearing steels which contain about 1 % carbon and 1 to 2 % chromium. These steels are used in the through-hardened condition for normal service with operating temperatures less than 150 C. Modification of the basic chemical composition, by an increase in manganese content or an addition of molybdenum, is used to increase the hardenability of heavier sections and ensure freedom from no martensitic transformations in hardening.
(Nayar,The Metals Databook, page113)
(new/better)
Through-hardening steels increase their hardness by the formation of martensitic, which results form rapid quenching. The mechanical properties depend on the quenching medium and the cooling rate. Quenching media are water, oil or air. Water Works fastest and has the most drastic effect, while oil and air are milder. Thermal conduction, among other factors, determines the cooling rate, too.
Through-hardening steels exhibit very good dimensional stability when heat-treated. Because of their natural hardening capacity they have high compressive strength and are especially suitable for molds with shallow cavities where high pressure peaks may be expected.
( Georg Menges,Walter Michaeli,Paul Mohren, How to make injection molds, p.8-9)
4. Annealing Texture:
(Old)
Preferred orientation evolved in the course of primary recrystallization or grain growth. Recrystallization texture occurs because recrystallization nuclei are of nonrandom orientations and grow into the deformed matrix at different rates. It can be similar to deformation texture or quite different from it. Texture changes during grain growth are connected with different driving forces for growth of variously oriented grains and different mobility of their boundaries (see compromise texture). Grain growth commonly (but not always) results in weakening of the primary recrystallization texture. Annealing texture is usually characterized by an increased scatter and a decreased intensity in comparison to the initial deformation texture, except for a cube texture in some cold-rolled FCC alloys and the Goss texture in ferrite steels.
(Recrystallization, Grain, Growth And Textures (PG:448 )
(New/ better)
The annealing textures in tubing appear to be complex rolled and annealed sheet. In tubing, different features of annealing textures can develop, depending on the relative reductions in wall thickness and diameter, the degree of deformation, the temperature of deformation, and on the deformation method before annealing (extruding, rocking, drawing).
(Erich Tenckhoff, Deformation mechanisms, texture, and anisotropy in zirconium and zircaloy, P.54)
5. Drop forging
This is the operation done in closed impression dies by means of drop hammers. Here the force for shaping the component is applied in a series of blows.
( Rao, Manufacturing technology: foundry, forming and welding, p.255)
PS.There is not old definition
No comments:
Post a Comment