Melting practice

The coreless induction furnace is used for melting but cannot be used for refining. Therefore, in steel foundries the induction furnace has to be charged with raw materials of the correct chemical composition, i.e. that corresponding to the required composition of the melt hence steel scrap is mainly used. If necessary, the metal can be refined after melting in an AOD converter or in special treatment ladles (see Section 2.4.12). 

Induction furnaces are excellent melting units, but in general they are less efficient holders. When they are used for melting only, the molten metal is mostly moved to an efficient holding furnace as soon as it has reached the desired temperature. Many types of coreless induction furnaces are available, with fixed or removable cmcibles. For aluminium, both channel and coreless induction furnaces are available for melting and holding. However, the charmel type is seldom used, due to difficulties in keeping the channel open and due to the need to maintain a molten heel at all times. 

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A. G. E., Robiette, Electnc Melting Practice, John Wiley Sons, Inc., New York, 1972, 412 pp., arc, induction resistor, and special melting furnaces are discussed. 

Selenium is added up to 0.1% to silicon steels (2—4% Si) used in transformer cores to enhance the development of the secondary recrystallization texture which, in turn, improves the magnetic characteristics. Selenium alloying additions to the melt may be made as elemental Se, nickel—selenium, or ferroselenium. The recovery depends on the melting practice and method of addition. Normally, it is in the range of 66%, but may be as high as 90%. 

Multiple-arc melting for a minimum of two melts is conventionally used to ensure a homogeneous ingot. Although conventional arc-melt practice involves a negative electrode, improved alloying is achieved with a positive electrode for at least one of the several melts and usually the first melt. 

White. C. H.. P.M. Williams, and M. Morley Gleaner Superalloys Via Impmved Melting Practices." Advanced Materials A Processes. 53 tApri) 1990). 

If flow in a physical model is to have the same character as that in large-scale melting practice, the conditions required by the similarity theory have to be met. The properties of the model liquid have to bear a certain ratio to those of the glass melt. Mere geometrical similarity of the model and the furnace (scaling down) is not sufficient it is also necessary to observe the similarity with respect to forces acting on the corresponding masses of liquids in tlie model and in the actual furnace. 

No negative effects were noted on the refractory. After an initial 3 month startup period, the furnace was cooled down and the internals were inspected, with no refractory damage noted. It was even possible to reduce the furnace temperature set point after optimizing the charging and melting practice. Overall, the roof temperature was lowered by 100°F (56°C), while maintaining the 30% increase in melt rate. This reduction was expected to result in considerable savings in refractory expenses. 

Group W is water hardening, essentially high carbon steels made to improved melting practices. Group W is used for cutlery, forging dies and hammers... 

Amorphous solid, faint aromatic odor. Softens at 55. mp 61 -67° (clear melt). Practically insol in water. Sol in chloroform. ether, ethylene dichloride, oils. The soly in vegetable oils is increased by the addition of camphor- MED i.m in rats 250 mg Bi/kg (Lauter, Braun). therap cat Formerly as antisyphililic. 

Crystals from dil pyridine, dec above 280° without melting. Practically insoluble in water, alcohol, ether, benzene, tettic acid sparingly sol in chloroform sol in nitrobenzene, pyridine. 

With the exception of Germany, most European coimtries follow American practice for the selection of materials to operate at subzero temperature (see Table 4-18). Impact-tested, killed carbon steel is used down to -50 F and -150° F and austenitic, chromium-nickel or 9% nickel steel from -150°F to -300°F. As a rule, the carbon steel specified for low temperatures in Europe is a fine-grain, aluminum-treated type, whereas in the U.S. it is more usual to request fine-grain melting practice which, in most cases, is produced by deoxidation with silicon and aluminum. 

Carbon steel piping as applied for warm services may, in accordance with ANSI B31.3, be used at usual allowable stress down to a minimum temperature of -20°F. With additional requirements as to chemistry, melting practice, heat treatment and impact properties in accordance with ASTM A333 (Grade O), carbon steel is usable down to a minimum temperature of -50°F. This specification limits manufacture to seamless or welded pipe without filler metal addition. 

The results of low-temperature and intermediate-temperature specific heat measurements on stainless steel 31 OS (two heat treatment conditions) and Inconel X750 (four melting practice/heat treatment combinations) were presented and discussed at the 1975 International Cryogenic Materials Conference (ICMC) [% In a continuation of that work, measurements have been made on 10 more samples, consisting of Inconel X750 (HIP), Inconel 706, Kromarc 58, and Nitronic 33, in various metallurgical conditions. 

Depending on the installed power density and the melting practice the thermal efficiency can exceed 80 %, but usually ranges from 60 to 70 %. If the efficiency of the electric power generation is taken into account, an overall efficiency of 15 - 20 % results, which is rather low in comparison with other furnace types. 

When the bubbling of inert gas is used for the degassing of copper, 50 - 70 litres of gas are used for each 100 kg of copper. An alternative is the use of specific tablets or briquettes. Degassing treatment usually takes 3-10 minutes depending on the size of the melt. The precise amount of deoxidant needed depends on the melting practice used. 

In this section, techniques concerning melting practices and furnace operation will be discussed. These techniques may apply either to cold or hot blast operation, or to both. Flue-gas related techniques, such as post combustion and flue-gas cleaning, are discussed in Section 4.5.2. That section also discusses the conversion of cold blast to hot blast cupola furnaces. 

Possible good melting practice measures include ... 

Good melting practice measures are applied in all cupola foundries. 

There is no clear distinction between solution and melt. Practically, liquid mixtures which are highly concentrated with the crystallizing substance (solute) are named melt. Liquid mixtures of low concentrated solute are named solution and their non-crystallizing components are called solvent. 

The next five figures show experimental results on the melting of pentacontane, C50H1Q2, a paraffin which melts practically reversibly [3]. Figure A.13.11 illustrates the comparison of a standard DSC trace and a quasi-isothermal analysis with a... 

Comparing the evolution of the structure depth (defined as the vertical size of the periodic structures. Fig. 7(b)) and the depth of the molten pool at the interference maxima (Fig. 7(a)) with the laser fiuence, the following observations can be made. Firstly, both experimental results and thermal simulations indicate that SS samples are molten at lower laser fluences than aluminum and copper in that order (see insert in Fig. 7(a)). This result can be explained due to the high absorptance and the low thermal diffusivity of SS at the utilized wavelength (355 nm). Secondly, aluminum and copper start to melt practically at the same laser fiuence, which confirms that... 

Most cast alloys are derived from their wrought coimterparts. Others are proprietary alloys developed as casting alloys. The only allo) discussed here are those covered by ASTM specifications. Use of industry specifications is not a guarantee that the required casting quality will be obtained. The more critical the applications, the more the end-user should know about the material, the foundry, and any intermediate fabricators. When there are no industry specifications, a private specification should be developed, either by the end-user or by the foundry, and carefully reviewed by the end-user. Extensive testing is required to develop a melting practice, compositional... 

Product Special ingot melting practices must be em-... 

Alloy Segregation. Ingot composition must be controlled within specified limits, and special melting practices, particularly for the final melt, are required to minimize segregation during solidification. Excessive macrosegregation results in "beta flecks, which are harder, less-ductile areas afler heat treatment. Defrim tal effects of beta flecks have not been demonstrated for this aUoy. 

The following information is included in many of the Technical Requirements sections composition, melting practice, condition of utilization, heat treatment, properties, quality, and tolerance. This is one of the core sections of many material specifications. The acceptable chemical composition is usually tabulated with the minimum and maximum elemental contents specified. The acceptable analytical methods are listed in the subsection of the composition. In AMS 5663, the weight percentage of constituent elements is required to be determined by wet chemical methods in accordance... 

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