AFS Library

Search Results

1–10 of about 625 matches for molding materials processes
1 2 3 4 5 6 7 8 9 10 11 next »

Transactions of the American Foundrymen's Society V 69 P 409-421, 1961 (13 p)
Steel castings offer a definite advantage to the designer of aerospace vehicles in the form of high strength and attendant weight and volume savings. The author's company's designers have utilized these advantages in the design of a supersonic trainer. Steel castings used on the trainer have been a problem from the standpoint of mechanical properties, and the causes of these problems appear to originate in the foundry. Controls in the foundry are required and will be more important as the alloys become more complex and the casting requirements more stringent. Foundrymen need to reevaluate their position and up-grade their product in order to get their fair share of business from the aerospace movement.

Transactions of the American Foundrymen's Society V 63 P 306-312, 1955 (7 p)
Casting finish is becoming in creasingly important. New processes such as shell molding, D process, and investment casting have been developed with one of their features being good finish. Over the years, various means have been used to improve the surface finish of green sand castings. Today a variety of additives is being used in molding sands in an attempt to minimize cleaning costs, eliminate or reduce machining operations, or improve appearance. The trend in sand seems to be toward finer sands with a specified number of screens. Several years ago, a series of test castings was made using sands from the various molding units in the plant. Some production sands produced expansion defects on the test casting though they could produce a satisfactory finish on the size and weight of jobs on the molding units in which they were used. A test pattern 12 in. square and varying from 5/8 to 2 in. thick was used. The pat tern was made of plywood and the thickness was increased by adding more pieces of wood. Castings were made to compare the molding sand mixes, pouring times, and iron temperatures.

Transactions of the American Foundrymen's Society V 70 P 612-621, 1962 (10 p)
Reactions between materials in close contact with metals and alloys occur easier when the latter are in the liquid. rather than in the crystalline slate. The possibilities for such reactions to take place are many, e.g., reactions between metal on the one hand and ceramics, molding materials or the atmosphere on the other hand. This paper deals with the reactions between liquid metals and oxygen. Investigations of reactions between liquid nonferrous metals and atmospheric oxygen, have alreadv been carried out on frequent occasions. Reactions between oxygen and metals, such as lead and zinc, have been studied with respect to the products formed and also the times taken for these reactions. It has been found that the latter are functions of the temperature and the composition of the allow and when plotted give either a linear or a parabolic graph. In contrast, reactions between liquid cast iron and oxygen of the air. have hardly been investigated. This may have stemmed from the belief that the slags encountered in castings were, in many cases, products of the reaction between melt and ceramic materials (in the widest sense). In the course of this investigation it was found that the observations published in the literature agreed with the authors' findings. These confirm that the slags appearing in spongy areas of castings arc developed bv the interaction of liquid iron and the air: this occurring in the ladle, in Ihe pouring stream or even in the mold. This preliminary contribution to the clarification of the problem of the kinetics of slag formation confirms the fact, known from the literature, that such reactions depend on the composition of the cast iron and especially on the silicon, managanese and sulfur contents. The author shows thai a close relationship exists between the composition of a cast iron, the temperature at which the oxide films are formed and the composition of the slags and their properties. In melts of cast iron that are rich in sulfur a sulfide slag is the first to develop, followed by a silicate slag. The temperature interval between the beginning of oxide film formation and the complete covering of the bath surface with slag is considerably smaller for melts low in manganese than for melts high in manganese. The possible cause of this may be a difference in wettability of metal and slag respectively. Summarizing, it is concluded that the formation of spongy areas in an iron casting is determined by the silicon, managanese and sulfur contents of the cast iron, by the pouting temperature and by the time during which the molten metal is exposed to the air.

Transactions of the American Foundrymen's Society V 61 P 367-377, 1953 (11 p)
The proper choice of a sand and the resin binder for shell molding determine to a large extent whether the process will be successful and economic. Most resins perform differently in degree and their utility depends upon their physical properties and the mechanism of the thermosetting reaction. Some are far superior to others. A cheap sand with the desired fineness is not always an economic shell molding sand. The performance of a sand on the automatic machine is dependent greatly upon the particle size distribution and grain shape, but of extreme importance is the condition of the surface of the sand. The choice of molding materials may be guided by proper screening methods and once production has started, control methods must be inaugurated to insure smooth and economic operation.

Transactions of the American Foundrymen's Society V 66 P 484-494, 1958 (11 p)
A large percentage of the shell-mold casting scrap is due to shell cracking and shell expansion defects. This report covers work performed in cooperation with the AFS Shell Molding Materials Testing Committee (8-N) in order to determine the causes of such casting defects when various sand and resin mixes were used. Hot expansion and tensile strength tests of the shell mixes were performed in the laboratory in an attempt to correlate these tests with the expansion defects found in test pattern castings.

Transactions of the American Foundrymen's Society V 64 P 398-405, 1956 (8 p)
New molding processes have received a great deal of attention in the past few years. Shell molding, D-process, pressure molding, C02 -process, and diaphragm molding, to name a few, have been widely heralded as providing a new era of progress in mold ing. Amid the claims and accomplishments of the new methods, it is worthwhile to take a new and critical look at an old process, green sand molding. What are the true capabilities of the process? How well is it now being used relative to its ultimate possibilities? What can be done to get the best results from it? Complete answers to these questions cannot be given for lack of certain fundamental information. However, the general direction of improvements can be discussed. To get the best green-sand casting, the best mold possible must be produced from a combination of molding sand and molding equipment. This mold should have uniform sand density, high hardness, high strength and thermal stability. Inevitably certain characteristics of the sand mixture will affect the ability of the process to obtain such a mold. There fore, consider first the molding sand.

Transactions of the American Foundrymen's Society V 65 P 499-512, 1957 (14 p)
The first serious interest in titanium was started in about 1946. Metallurgists reasoned that the high melting point of titanium, 3140 F, might make it applicable for service at elevated temperatures. In addition, the low density of titanium, approximately 40 per cent that of stainless steel, added to the interest in this metal. The potentiality that titanium might possess a high strength-to-weight ratio for use at elevated temperatures made it appear particularly attractive for military aircraft, especially the jet planes designed for supersonic speeds.

Transactions of the American Foundrymen's Society V 67 P 553-576, 1959 (24 p)
The difficulty of poor collapsibility, predominate as a limitation in the sodium silicate-C02 method of sand bonding, is obviated by establishing simple laboratory test methods to determine an optimum quantity of sodium silicate binder. This is designated as the minimum critical percentage for each sand considered. Additives such as sugar, coarse grain silica flour and iron oxide, properly used, contribute to the flowability, ramming qualities and green strength and enhance collapsibility as well as provide hot strength and cushion ing during thermal changes. The binder requirements should be developed on the hypothesis of adhesive bonding rather than on the basis of a mortar composition, which fills voids between the grains. Adhesive binders are most effective in thin films and with the greatest number of sand grain to grain adhesive contacts uniformly distributed in the sand structure. The viscosity and penetrating qualities of the binder composition determine the degree of correlation that binder requirements have to B.E.T. specific area measurements. The B.E.T. data can be used to designate those sands which will need more or less binder than their AFS fineness number indicates. A straight line correlation between minimum critical percentage and a dimension al parameter calculated from AFS fineness data, shape factors, ratio multipliers and specific volume ratios raised to the fourth power is given. The limitations due to high relative humidity and the use of clay additives are discussed. Experimental data, as well as numerous references, are used to support these findings.

AFS Transactions 1975 p. 437-440 Available as Preprint No. 75-33 @ $3.00
A presentation of the flexible mold process, a new concept in coreboxes and patterns utilizing elastomeric materials is given. The patented process combines nobake technology with flexible one-piece coreboxes and patterns, eliminating costly core assemblies and loose pieces, while producing higher quality castings with lower casting and pattern costs. The flexible mold, when properly applied, also provides further savings to the casting customer in reduction of machining and the removal of normal foundry restrictions in casting design and engineering.

AFS Canadian Regional Conference, Oct. 1969, Canadian Metalworking/Machine Production--June, 1969, p. 11-18
This extensive paper, to use a modern cliche, tells it like it is by investigating numerous phases of the metal casting industry. For example, it shows how metal casting is feeling the pinch of competitive materials and processes. It points out how metal casters have left themselves vulnerable to competitive processes by not paying the attention to product quality and reliability required to meet the demands of today's markets. It further points out in detail that although the technology to upgrade standard areas of foundry operation has become available in recent years, it is still begging for application. It shows examples of how many jobbing metal casters could use some of the techniques used in the captive operations. It points out examples of how a general overhaul of processes is needed along with a program to educate industrial designers to the advantages and limitations inherent in castings could do much to promote their use. It further discusses a variety of new processes suitable for use in the large and small company. These processes discussed range from melting through molding, coremaking, pouring, shakeout and cleaning. Production control as to metals and sand are discussed in detail and it is pointed out that the size of the company does not have to be a limiting factor in its use.

1–10 of about 625 matches for molding materials processes
1 2 3 4 5 6 7 8 9 10 11 next »