By J. KING This Paper deals with some of the factors influencing the production of sound castings in M eehanite, for sound castings are the prim ary aim of every foundrym an. Soundness is governed by a num ber of factors, including m etal com position, melting conditions, casting tem perature, sand control, gating, etc. To discuss all, or even several factors, would entail too much time and space. In the m ain the author deals in detail with the results of personal experience.
Sand Control
This plays a very im portant p art in the pro
duction of castings, and is responsible for many wasters, usually through lack of permeability.
Permeability can be increased by judicious venting, but few m oulders seem able to use a vent wire properly, and therefore sand should, w here possible, be graded and mixed to give the desired permeability without resort to the vent wire. This can be proved by experim ent
ing with sand moulds using sands of varying permeability. Low refractoriness in sands is responsible for surface defects and machining troubles due to sand adhering or fusing to the surface of the metal. This increases machining difficulties and fettling costs rather than being a cause of unsoundness.
C ontrol of moisture content is also essential in order to avoid blow-holes and loss of permeability. It will also possibly affect the structure of the casting, as steam and gases generated by the contact o f hot m etal with the water in sand pass through the metal. Excess m oisture also causes chilled edges, etc. Care should be taken in ram m ing the mould, which is generally done more efficiently by machine.
The au th o r’s firm uses a fusion test of sand—
believing it to be essential for heavy work, especially for tops of moulds for large castings.
F o r instance, if a riser blows air (commonly called “ draw ing ” air in the foundry) it gives an idea as to the heat to which the top face of the m ould is subjected as the hot m etal rises to it, especially if the top has facing strips on it.
One job to which it seems desirable to refer is a casting m ade off the old one used as the pattern. It was a 100-ton press casting, a com bination of two cylinders and table, weighing 11 tons 10 cwt. Sand* control played a big p art in m aking this a successful job, which is illustrated in Figs. 1 to 3. The casting used as a pattern was over thirty years old, and was analysed to discover its composition. Samples were taken which gave a tensile test o f less than 9 tons per sq. in., and the analysis was that of a very poor iron. The new casting was made in an ordinary grade of Meehanite, which gave a tensile of 18 tons per sq. in.
F o r successful results, the sand requirem ents for cores are similar to those already mentioned, and sand testing and control contribute greatly tow ards this end. The author recognises the progress made in sand research in this country.
To-day executives can confidently operate their foundries with every property in sand practice under direct control. This is as it should be, since the mould for containing the hot metal is just as im portant as the metal itself in the p ro duction of quality castings. However, it might be as well for all to rem em ber at all times that just testing sands, or trying to m ake syn
thetic sands, does not make castings. Foundry- men must in all cases employ judgm ent as to results from sand tests, and especially is this the case in the m anufacture of synthetic sand.
Interpretation Needed
Hasty judgm ent in connection with either of these procedures leads to negative results.
Sound knowledge, coupled with proper inter
pretation, is o f vast im portance to anyone interested in the proper selection and use of sands in the foundry. It now appeàrs clear that foundrym en can look forw ard with con
fidence to great improvements in sand practice in the near future. Rapid changes are de
veloping in the mechanical treatm ent, m ore use is being m ade of clays for re-bonding, and even cement is also used. W ith these developments the industry should soon be in a position to select, blend, and use sands located anywhere 165
in the country with good success, for iron, steel, o r non-ferrous castings. Sand testing and co n tro l in conjunction w ith the proper blend
ing m akes possible the use of local m aterials in place o f m oulding sands located perhaps scores o f miles away.
O perations o f this sort develop econom ies of considerable value to foundrym en. Selection of sands fo r use in the foundry is based prim arily on needs as related to the range in size o f the castings to be m ade. It is now a simple m atter to select approved m oulding and core sands w ith the assurance th a t in use they will yield satisfactory results. F ounders can if they wish subm it specifications to the sand suppliers, and
T he author's practice consists in the use of one type of sand for light and m edium work, and another for heavy tops, etc. ’I t is quite custom ary to find jobbing foundries operating with a great variety of m oulding sands of different grain-size, clay content an d per
meability. It is also quite usual in jobbing foundries to find m oulders free to use their own judgm ent in mixing and blending any of the sands in the shop.
T he m ixing and blending o f sands with widely different physical properties is wrong, and runs contrary to established knowledge of better sand control. In m aking specific re
com m endations for sand practice in foundries,
F i g . 1.— S o m e o f t h e C o r e s u s e d f o r t h e M a k i n g o f a 1 0 - t o n C a s t i n g u s i n g a D i s c a r d e d C a s t i n g a s a P a t t e r n .
they in tu rn will, w ith reasonable accuracy, supply the sand in accordance with the speci
fication. H ow ever, some foundries are still ordering by trade nam es and no t by specifica
tion.
H ere is an initial opportunity for simplicity, fo r an effort should be m ade to have the least num ber of sands possible in the foundry. This procedufe avoids com plications. F o r example, if a coarse sand with high perm eability for heavy w ork be needed, an endeavour should be m ade to use th a t type o f sand exclusively for heavy w ork. A t no time should a very fine sand be mixed with it, because in doing so the advantages of open grain and high perm eability are lost through small grains and interstitial congestion in the fine sand.
one should always take into consideration the shop conditions under w hich the sands will be used.
It is no t sound to suggest the use of any sand unless the m ethods of operation in the foundry are know n. T hen only can con
structive advice be given on the type of sand best suited to th a t particu lar practice. For exam ple, one foundry m ay use a continuous sand handling system, an o th er m ay use muller m ixing operations, and a third one employs m achines o f the R oyer type or sand cutter.
All m echanical treatm ents are good, bu t they produce widely different results. This must be borne in m ind when m aking definite recom m endations. Simplicity has been strongly em phasised throughout this reference, both
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from the standpoint of selection and use, a s 2 well as testing and control o f sands.
Runners and Risers
In leaving this subject it seems clear that by careful selection to begin with, followed by suitable preparation for the w ork in hand and then applying com monsense m ethods of testing and control, foundrym en can accom- .. plish m uch in the m anufacture of castings. In
m ost foundries engaged in m aking a m iscellaneous line of castings, and this applies to practically all M eehanite foundries, the ques
tion of risers, their size, shape and location is one th at calls for profound attention and
out extensive use o f risers, it is not his purpose to say whether risers should or should not be used in other shops as they are now being used.
It is possible this practice is correct, and, while it may be expensive in that it reduces the yield in saleable castings per ton o f metal melted, yet it may be a m easure of insurance against the loss of a casting for which the customer m ay be in quite a hurry. Then, again, risering may do m ore harm than good. An interesting Paper given on runners and risers, to which reference is strongly com m ended, was given to the Scottish Branch by J. Longden (Paper No.
624, Volume X XX, 1936-1937).
F i g . 2 .— C o r e s b e i n g A s s e m b l e d i n t h e M o u l d .
consideration—m ore than is given in a good Defective Castings
m any cases. Considering the variety of cast- Everybody has heard that some foundries li® ings as wide as in m ost foundries known to the have no scrap, whilst others have 5 to 10 per
author, the risers used are few in num ber. It is cent. The A uthor has his own opinion o f the true the au th o r’s firm has perhaps a little better so-called 100 per cent, no-scrap foundry, so he
»8 chance to develop their shop practice because wju try to help the alleged 5 to 10 per c e n t..
® most of their w ork is for use in their own scrap category. Three basic factors m ust be 'sti machine shops, and for their own line of considered in this connection: (1) M ental atti-machines of various types, but there is no tude towards defectives; (2) m anagem ent Ifi chance of anything being accepted by the responsibility; and (3) nature and conditions of p Inspection D epartm ent, unless it is entirely work.
j satisfactory in m aterial and in w orkm anship. M ental A ttitu d e.— In considering the basic The author was convinced that in many cases conditions responsible for defective work, it is
I I I « ! some foundries would be rather glad of a evident that the m ain factor is that defective
B|k chance to take for their use some of the cast- castings are tolerated in the foundry. In other ings his firm scrap as not being up to stan- words, the m ental attitude of m anagem ent and
„¡I dard However successful or otherwise the staff is to expect defective castings. They are lull firm m ay be, or have been, in succeeding with- accepted as a m atter of course, and, provided
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th a t they are kept dow n to w hat is considered a n orm al w orking range no great attention is paid to the m atter. It is frequently argued that the foundry loses nothing by defective work since this is covered by the estim ated loss in
cluded in the price.
T his is an exam ple o f the m ental attitude which is responsible for defectives.
M anagem ent R esponsibility.—T h e scrap p ro b lem is essentially a m anagem ent problem , in fact, it m ay be stated as a general rule that the percentage o f defective w ork is inversely proportional to the attention given by the foundry m anagem ent to this m atter. M anage
m ent is directly concerned with obtaining the m axim um operating efficiency, and elim ination o f defectives is as closely related to efficiency as is production capacity.
mm
Fi g. 3.— Th e Fi n i s h e d Ca s t i n g.
N ature and Conditions o f W o rk .— Defective castings m ay be classified into two m ain divi
sions: (1) D efective m aterials, and (2) defective w orkm anship. Both o f these conditions are traceable to the m anagem ent whose duties in-
* elude: (1) Suitable places for m en to w ork; (2) supply o f the correct w orking m aterials for the men; and (3) education and supervision o f m en in correct m ethods of working. Owing to the nature of foundry w ork, these duties become o f vital im portance in foundry m anagem ent. In the days o f apprenticeship a casting m ade just before leaving off for the day, and know n to be a waster, w ould cause a restless night, but by experience it has been found th a t w orry will no t rem ove the cause. A n inquest on the defective will prevent a repetition. N o replace
m ent should be m ade until the cause o f the trouble is ascertained. M r. L. J. T ibbenham , in his presidential address, referred to defective castings. Since then, the A uth o r has thought that a Paper on the subject would be m ost o p por
tune. It is h ard to obtain 100 per cent, good castings, but an effort is m ade to get as near to it as possible, and tackling this defective problem objectively will help the foundry to reach this goal.
D efectives in the Machine Shop A large p roportion o f the castings found de
fective in the m achine shop are due to the lack o f collaboration between designer and machine shop. In the production o f castings there is involved the w ork o f the designer, the pattern
m aker, the foundrym an, and the m achine shop engineer. M uch of the difficulty o f collabora
tion between these departm ents is due to the lack o f appreciation o f the difficulties involved in other w ork and in particular to the fact that each talks in a different technical language.
The collaboration should be divided into three. F irst, choice o f m aterials— inform ation available to the designer fo r the selection of the m aterial best suited to the service involved.
Secondly, collaboration between designer and foundry to reduce m oulding and m etallurgical problem s. T hirdly, collaboration between foundry and m achine shop to facilitate m achin
ing operations.
Each of the subjects touched upon are such that a P aper could be given on each, and a very interesting Paper, too. T hese subjects were selected from experience in changing from ordinary cast iron to M eehanite. In conclusion, the au th o r would like to thank the m anagem ent o f Ransom es & R apier, Lim ited, also the Inter
national M eehanite M etal C orporation, for per
mission to give this Paper.
DISCUSSION
M r. J. L. Fr a n c is congratulated the author on his practical Paper, and put the following q u e s tio n s:— (1) Are denseners em ployed? and (2) is any rod feeding practised? C om m enting on the standardised pouring basins, runners and gates, m oulded from p roper patterns, he said how often one saw every care taken with moulds and cores whilst ingates were cut at the m oulder’s discretion and any odd piece o f wood em ployed to form a dow ngate. This haphazard m ethod tended tow ards a surface m ade up of disturbed sand grains which cam e aw ay with the m etal stream . All the m etal entering a m ould m ust pass through the runners and, there
fore, they should have at least as m uch care and attention as the mould itself. G ates and runners supplied as part o f the pattern ensured the same undisturbed sand surface as m ould
and cores, and m ade a serious contribution to
w ards soundness in castings.
Mr. Ge o. Hall thanked Mr. King for his foundrym an’s lecture to foundrym en. H e asked whether the pencil runners used were invariably the diam eter of a pencil and m ore o r less used according to the size and weight of the casting.
As Mr. K ing em ployed no horse m anure in his sand, w hat did he use in place o f it? Mr. Hall had used sawdust successfully, but it had to be from wood containing a minim um of oil, as otherwise difficulty was experienced in the blacking of the sand surfaces.
Mr. D. Carrick: inquired as to the time taken in pouring moulds, and asked if Mr. K ing made use of any m eans o f calculating the size of gates and runners relative to the weight and size of the casting.
Mr. L. E. Sl a t e r asked if Mr. K ing made fluidity tests, and said also th at where sand burnt on it was m ore often due to unsuitable sand than the fault of the runner. He also asked whether the author had tried feeding from the side and bottom of, for example, a flywheel with clutch plate, the latter cast in the bottom .
Mr. H. H . Sh e p h e r d said that M eehanite metal had the right to rank as high as any other metallurgical development of recent years.
The lecturer had given instances of M eehanite replacing castings of malleable cast iron. Such high grade irons, however, had not been successful in m aking the replacem ent in all cases, and service equipm ent subject to blast effect was a case in point. A beneficial feature of the use o f strainer cores was their prevention of air sucking in with the metal. Finally he
proposed a hearty vote of thanks to Mr. King for his excellent practical talk.
A uthor’s Reply
Mr. Kin g, in replying, expressed appreciation for the way in which his P aper had been re
ceived. D enseners were used round the outside of some castings, but not internally. Rod feed
ing was used, but by standardised methods of running and risering as explained, he had cut down this m ethod o f feeding by 20 per cent.
W ith regard to pencil runners, these were approxim ately the diam eter of a pencil, and could only be applied for top running. In place of m anure he employed cocoanut fibre, cut about 1 in. long. Mr. Francis had used spent hops as obtained from breweries with success.
In reply to Mr. C arrick, Mr. Kin g said that sizes of down gates and runners were fixed empirically, and from experience accum ulated by recording pouring times for various castings over a period.
Mr. Fr a n c is, intervening, said th a t D ietert had done much work on this subject in A m erica, and had evolved formulae by means of which size o f choke and height o f runner could be calculated relative to weight and section thickness.
On the question of fluidity, Mr. Kin g said it was m ainly a question o f correct distribution of metal in one m ould which avoided trouble.
H e considered that the feeding methods m en
tioned by Mr. Slater would not be so good as top feeding. If rapid flow and squirting of the metal were prevented by opening the choke, liquid shrinkage was largely taken up as p our
ing progressed.