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A Note on Britain's Experimental

Foundry

By G. ERNEST WELLS, Sheffield, England

I shall endeavor in this brief paper to give a short description of the foundry built during the war by the British government at Brentford, and the reasons which prompted the British ministry of munitions in establishing it. Primarily the purpose was to enable researches to be made into all questions affecting the manufacture of malleable iron castings. In Great Britain the output of most firms is small and the result is that with one or two exceptions, practically no producer does sufficient business to enable it to conduct the manufacture of malleable iron castings on thorough and up-to-date scientific lines.

Before the war, makers of pig iron specialized in irons suitable for use in the manufacture of malleable iron castings, and each maker used a brand or trade mark by which his iron was known. The malleable iron founder made tests of the different brands and eventually bought those particular ones which in his opinion best suited his methods.

Supplies Were Cut Off

After the outbreak of the war, many of our supplies of raw material were either cut off or sidetracked for different purposes with the result that although malleable iron founders. still continued to buy the brands of iron which had given them satisfaction in the past, they found all sorts of new troubles cropping up for no apparent reason. Had all the founders been in posession of up-to-date chemical laboratories before the war, they would naturally have quickly discovered that the analysis of their material had completely changed and would have acted accordingly, but in view of the lack of facilities for carrying out this work, it was felt by the

ministry of munitions that the best thing to do was to equip a small foundry with trained technical staff, in order that the difficulties experienced should be submitted to impartial and independent investigation.

The plant erected contained an up-to-date cupola, a number of pot-holes, one or two different types of annealing furnaces, and a completely equipped physical and mechanical testing laboratory. This laboratory was put in charge of Mr. Mason, a skilled research chemist who had specialized in malleable iron problems, while the foundry itself was in charge of a malleable iron founder of considerable experience.

As the work developed, difficulties of all sorts experienced by manufacturers were put up to the government's experimental foundry for solution, and after a thorough investigation a report was made which was at the disposal of any founder who wished to see it.

Results Were Valuable

In this way a great deal of valuable work was done, and in certain cases raw materials were successfully used which hitherto had been considered valueless for the manufacture of malleable iron castings. At a later date, a good deal of help was given to firms who were experiencing difficulty in the manufacture of so-called semisteel shell, and John Shaw arranged demonstrations at the Brentford foundry so that contractors were able to send their technical men to see exactly how success was to be attained.

Report of A. F. A. Committee on Specifications for Malleable Iron Castings

AFFILIATED WITH A SIMILAR COMMITTEE OF THE AMERICAN SOCIETY FOR TESTING MATERIALS

Your committee begs leave to report as follows: The majority of the members of your committee have been constantly in touch with the work of the American Society for Testing Materials committee with whom they are affiliated in their efforts to have the tentative specifications for malleable iron castings made standard. In view of this fact it was thought it would serve no useful purpose to call a meeting for a personal discussion of the matter unless some member of the committee had in mind some change he cared to recommend.

A letter was written to each member asking his opinion in regard to the desirability of discussing the situation personally prior to our meeting in September but they have signified their desire to endorse the action taken by the American Society for Testing Materials committee on malleable iron castings and recommend to the American Foundrymen's association its acceptance of this specification as standard.

Inasmuch as the tentative specifications have been made standard there are no remarks to be made in connection with them beyond what was contained in the committee's report of last year.

Respectfully submitted,

A. E. HAMMER

W. G. KRANZ

F. E. NULSEN

ENRIQUE TOUCEDA, Chairman

The Elimination of Strains in

Iron Castings

By C. J. WILTSHIRE, Schenectady, N. Y.

It is a well known fact that appreciable strains remain in iron castings after cooling, which are caused by unequal radiation of heat from the castings after they are poured. This unequal radiation is due to variation of section and difference in length of paths from inner to outer surfaces, through which the heat must pass to escape.

In consequence, the heat is not uniformly dissipated as the portions where the metal is thickest and those most remote from point of heat exit retain temperature longest, causing shrinkage strains to be set up in the parts which have been first to cool.

Some 22 years ago, Alexander Outerbridge, of Philadelphia, discovered that vibration of a cast iron bar (by tumbling in a barrel or by a continued tapping with a hammer) would invariably increase the strength of the casting. The theory of this treatment is that the action of cooling causes molecules of iron to be held in tension which is relieved when the casting is subjected to vibration.

It has since been found that this tension can also be relieved by annealing the castings in an oven of moderate temperature, which method it is the purpose of this paper to describe.

That shrinkage strains exist in most castings is demonstrated by the fact that if a plain cast-iron plate is machined to a true surface on one side, the operation of machining the other side will frequently disturb the accuracy of the surface first finished. This phase of the matter was presented to the American Foundrymen's association in a paper on "The Seasoning of Gray-Iron Castings," by L. M. Sherwin, of Brown & Sharpe Mfg. Co., at the Boston meeting in 1917.

Large castings which have been left in the sand to cool off slowly and then finished to true dimension, after a few days have been found distorted under ordinary temperature changes, but these same castings after treatment in the oven did not show any change whatever.

Results of Annealing

Other castings which have been finished and put under steam for test have shown considerable distortion when taken apart, while castings from same patterns when treated in an oven before finishing and tested out in the same way, showed absolutely no distortion.

Again, large castings which have been finished and lined up as parts of a large unit, after a number of months in service have shown sufficient distortion to cause parts of the machine to become out of line. Such castings are now being annealed and from results obtained it is believed that this treatment will prevent the defects experienced.

The method of treatment is as follows:

The castings are placed in the oven, the doors are closed, the heat turned on, and the temperature raised to 700 degrees Fahr., which generally takes from seven to eight hours. This temperature is held for an additional seven hours, when the heat is shut off and oven is allowed to cool down slowly for approximately 20 hours, with a resulting temperature of about 300 degrees Fahr. The oven doors are then opened and temperature is allowed to drop to approximately 150 degrees Fahr., when the castings are in shape to be taken out. The entire operation consumes about 48 hours.

The ovens are heated with oil and the amount of oil per ton of castings treated has averaged 9.6 gallons. Each heat required 284 gallons of oil and approximately 29 tons of castings were treated each heat.

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