up under gas or water pressure. All over the country foundries are making hydraulic and ammonia castings by the greensand method; and they are stoutly claiming the fact that they are getting away with it. Careful investigation, however, will prove that the consumer is kept busy closing up porosities and that every so often a truck load of defective castings are brought back to the foundry and are carefully smuggled in the back door, so too many people won't see them. It is possible to make hydraulic castings in green sand molds, but it is not possible to make them day in and day out and be fairly certain that they are all sound. It is almost an impossibility to control the water in the green sand mold; and water suddenly converted into steam has a habit of exploding in the most unforseen places and in the most peculiar ways. As a general rule, a hydraulic or gas casting should be made in a thoroughly baked mold, and if proper materials are used, and the melting is carefully done and the mold is kept clean, there is no trick in turning out acceptable hydraulic castings. There is one more item in the molding department that deserves attention and that is the proper method of pouring. The scrap pile receives a great many contributions because of the carelessness or incompetency of the man at the ladle. Every ladle of metal should be held for a minute or two to allow the slag and other impurities to come to the surface. Stopping to allow the metal to clear itself may seem like a waste of time to the modern production hog, but if the gentleman will stand by a ladle and watch the various impurities float up to the surface he will understand why it pays to give the metal time to clear. In the end more good castings will accrue from such practice, and in the final analysis real production will be increased. Metal going into a sand mold should be poured evenly and carefully and under no consideration should hot metal be poured at high pressure directly over a large flat area of sand. Cuts and scabs and snakes are too often the result of fast, furious pouring. It is far better when dealing with a casting having a large flat surface, to cut back-up gates and break the force of the stream of metal rather than resort to a mass of finishing nails, a lot of swabbing and other dodges to prevent the facing from cutting. Another exceedingly common error is the practice of pouring metal directly up against a core at right angles to it. If it is possible to allow the metal to slide parallel to the core, there will be far less cutting and much less dirt. It is obviously impossible for any one man or group of men to enumerate, much less describe, the many apparent defects and troubles that exist in a foundry. If the foundryman will carefully study and examine the defective castings, if he will try to trace out his problems from cause to effect rather than trust to dumb luck, he will find, as stated before, that the real fundamental troubles in the foundry are comparatively few. The value of a scrap pile lies in the fact that it offers a real course of instruction in foundry practice, and this paper has been written in an attempt to induce the foundryman to commune with his defectives, to study their peculiarities, to grasp the principles of casting in their broadest sense, to realize his responsibility to the community, and finally, it is written with the hope that the foundryman will earnestly strive to manufacture sound castings, rather than alibis and fictitious production sheets. Discussion MR. ROBERT J. ANDERSON.-At the present time, foundries are in need of inquiry as to the reasons for scrap losses and wasters in the production of castings, and no preventative measures can be taken until the causes for defects are known. Every progressive foundryman should inspect his daily production with a view to determining the reasons for defects. The suggestion offered in the paper that an experimental molder should be employed is sound. Although Mr. Traphagen has not given any figures for scrap losses, it is a well known fact that these are often high in many foundries. The author complains of the work done by scientific men in connection with foundry practice and claims that their contributions to the literature are of little value to foundrymen. The writer entertains considerable doubt that the literature of the foundry is any worse than that of any other industry, and is compelled to conclude that the fault does not lie entirely with the scientific men. It seems to me that it is exceedingly dangerous to belittle the work of scientific men in general. As a matter of actual fact, with the exception of the present paper by Mr. Traphagen, and a few other papers and some text books, I have never been able to find a frank discussion of the foundryman's troubles written by foundrymen. This is an opportane time for foundrymen to lay all the cards on the table and come to the fore with a frank discussion of their difficulties. Relation of Gases to Casting Practice Mr. Traphagen's remarks regarding gas evolution when liquid metal is poured into a sand mold are interesting. The relation of gases in metals and alloys to casting practice is one that has been rather neglected. In casting, gases are derived from two sources; those evolved from the metal, and those set free by the mold and possibly the cores. Liquid metal cannot remain in an mpervious mold because the gases evolved must find an outlet. In the case of an impervious mold, the gases would find a path to freedom by throwing the metal through any possible outlet, and here there would be a kick-back through a runner or ejection through a riser. The gases evolved on pouring liquid metal into a sand mold must be drawn through the sand, and it is usually necessary to augment the porosity of the sand by venting. Blowholes and sponginess in castings may be due to gases dissolved in liquid metals which are liberated on final freezing. These defects can also result from gases given off from the mold and cores on pouring. Chill blows and core blows are defects which every foundryman is familiar with, and they can be overcome by proper precautions. With particular regard to gases in metals, liquid metals dissolve increas ing quantities of gas with rising temperatures. This is a departure from the law of Henry, for aqueous solutions dissolve less gas with increasing temperatures. Hence the higher any metal or alloy is heated before casting, the more gas will be dissolved. These gas-metal solutions readily remain supersaturated, and consequently an overheated melt will usually contain more gas at the moment of pouring than one heated not so high. If the dissolved gas is largely given off during the freezing range, and this appears to be the case, then castings poured from overheated charges will be more porous than those poured from charges heated to the correct temperature. Probably the greatest variable in iron and steel casting practice, with the exception of the human element, is the casting temperature. Troubles Traced to Molding Practice In the daily inspection of castings, it is possible to enumerate the defects which lead to rejection, determine the causes, and make corrections. Defects in castings may be grouped roughly into three classes, namely those due to metallurgy, those due to molding, and miscellaneous. Mr. Traphagen's statement that 90 per cent of the troubles can be traced to the molding department accords with the writer's experience. Many of the defects traceable to the molding department are due to carelessness, and this is particularly true under fast production methods. Laxity in mold inspection is a prolific cause of defects in the resultant castings. Misplaced cores, core shifts, cores left out, chills left out, dirty cores, broken cores, poor ramming, misruns, run-outs, etc., can largely be avoided by proper supervision. Many of the defects in castings can be placed in the avoidable class at once. Some defects are due to the method of molding, the gating, and the position, and size of risers. These cannot be remedied unless by changing the molding, and this is where Mr. Traphagen's experimental molder will be extremely useful. Concrete Foundry Molding Floors By HUTTON H. HALEY, New York A foundry, no matter what its kind, type or size, is not a solid, compact, producing institution in the same sense as those branches of the metal-working art with which it is so closely associated. Almost every part of a machine shop, for instance, may be operated with clock-like regularity; every move, operation, cost or loss may be closely tabulated and predetermined if necessary. Hence the machine shop, which usually has an intimate connection with the foundry, is tangible in its operations. The foundry, however, may be likened to the stomach into which raw materials are taken, broken down, assimilated and a new product generated with varying degrees of wastage. The foundry is constantly affected by wide ranges of fluctuations, caused by innumerable unpreventable conditions and contingencies, therefore it is recognized by those well versed in its practices to be perhaps the most intangible, misrepresented and least understood of all our great industries. In a foundry it must be understood that the basis of production is and probably always of necessity will be more or less destructive, crude, dirty and disagreeable compared with other metal-working processes. The fluctuating common-labor element will always play an important part as it cannot be entirely supplanted by mechanical devices. This being the case, it would seem wise to anticipate the most agreeable conditions possible and to provide every reasonable facility for light, air, cleanliness, neatness and order. The foundry is too often pictured as a place where filth, darkness, heat and disorder abound and very often all of these disagreeable conditions exist. However, anyone who has visited any number of our most up-to-date foundries will readily agree the reverse may be true. No floor expanse may be viewed with as much pride and satisfaction as a businesslike foundry, shipshape and ready for work shortly before seven o'clock in the morning or just before heat time, with its floor checkered with thousands of orderly molds. Every profit-mak |