Feb., I 9 1 4
T H E J O r R S A L O F I S D I ’ S T R I A L A S D E*VGI-VEERI*VG C H E M I S T R Y
b u t also those processes a n d reactions which cause t h e oil t o eliminate rolatile substances, which might detract materially from t h e weight of t h e paint. I n this connection i t is of interest t o cite t h e tests of Olsen a n d Ratner’ upon t h e drying of linseed oil. T h e y record a gain in weight of 18 per cent at t h e end of approximately I O weeks. T h e y also showed t h e elimination of approximately j per cent of carbon dioxide and ~j per cent of water. SUMMARY O F CONCLUSIOXS
I. When linseed oil or similar drying oils are spread in t h i n layers, t h e absorption of oxygen which takes place is accompanied b y t h e evolution of considerable amounts of carbon dioxide a n d organic substances. Carbon monoxide is also evolved in small a m o u n t . 11. Oil paints containing lead or zinc pigments do not emit volatile compounds of a metallic nature. 111. Drying paints evolve water-soluble acid substances such a s formic acid, as well as acid substances which are apparently of a f a t t y nature. Carbon dioxide a n d carbon monoxide are also present in t h e vapors from t h e drying paint. T h e t y p e of pigment used i n t h e paint m a y directly affect t h e a m o u n t a n d character of t h e volatile substances produced. Basic pigments apparently stimulate t h e evolution of such products. IT’. Aldehydic substances are present in t h e vapors from drying oil paints. These substances probably h a r e a marked bactericidal effect upon pathogenic bacteria a n d would t h u s account for t h e sanitary value ascribed t o oil-pigment paints. T h e writer desires t o t h a n k H. C. Fuller, L. G. Carmick a n d t h e staff of T h e Institute of Industrial Resea:ch for their assistance in carrying out t h e above experiments. RESE~RCH WASHINGTOS
I N S T I T U T E OF INDUSTRIAL
METALLOGRAPHY AS-APPLIED TO INSPECTION By WIRT TASSIN
Received December 11, 1913
T h e sudden failure of engineering structures of metal. t h e static physical tests of which, before use, pointed t o t h e good quality of t h e materials. is well known. Such failures h a r e usually been attributed t o a socalled deterioration known as “fatigue.” Whether or not repeated stresses below t h e elastic limit of t h e metal can set up such a deterioration m a y be questioned. One fact has however been proven beyond all question, a n d t h a t is t h a t in a n y metal there are always present certain structural conditions, t h e influence of which are either favorable or unfavorable t o “fatigue.” The character of these structural conditions is indicated in p a r t only, a n d t h e n o f t e n b y chance, b y t h e static a n d dynamic tests. I t m a y , however, be completely revealed b y metallographic methods, t h a t is, b y t h e s t u d y of t h e structure of t h e metal as seen on t h e etched surface under t h e microscope. T h e possibilities of metallographic methods as a n additional safeguard t o determine quality have been 1
J S C. I , 31, 9 3 ; (1912).
95
recognized, b u t their usefulness has been limited by t h e lack of protability in t h e , appliances necessary for their use. This has made i t difficult, if not impossible, t o s t u d y t h e forging, t h e casting or t h e bar as a whole, with t h e result t h a t t h e metallographic field has been limited t o t h e examination of more or less small specimens cut from t h e piece a n d which. like t h e bar used for t h e machine tests, m a y or m a y not be representative of t h e whole. It is t h e purpose of this paper t o describe a complete metallographic outfit which is portable a n d may be used either in t h e mill or t h e laboratory a n d is serriceable for t h e s t u d y of t h e forging, t h e b a r or t h e casting as a whole; t o give certain types of structure found in t h e ferrous metals; t o give a list of certain probable causes for failure a n d t o outline a scheme for their detection a n d t h u s supplement other methods of testing. THE APPARATUS
The apparatusi consists of a microscope, illuminating device a n d a camera, all self-contained. Fig. I , .I. B and C. T h e microscope, Fig. 2 , consists of a barrel, b , a n d a draw-tube, d , mounted on a handle a r m provided with a coarse a n d a fine adjustment. Attached t o t h e barrel is a shoulder, c, which holds a rod, Y , controlled b y a set screw. T h e base of this rod rests on t h e pinion head of t h e handle-arm a n d when lockcd m-ith t h e sets c r e n prevents t h e coarse adjustment from overrunning when using t h e camera. T h e whole is carried on a base which is t h e stage. Through t h e center of t h e stage is a 1-inch circular opening which affords free space for t h e objective when examining large masses below it. Leveling screws are provided, one in each of t h e four corners of t h e stage, which permit t h e adjustment of t h e microscope perpendicular t o nearly a n y surface. T h e illuminating device consists of an a r m . a , in Fig. 2 , which locks into t h e microscope barrel b y means of a threaded collar. The a r m serves t o carry t h e condensing arrangement made up of a telescope tube, t t , which carries t h e lenses. T h e t u b e is mounted in a sleeve, y, provided with a set-screx t o lock i t in a n y position. A hanger, h , from t h e a r m is attached t o this sleeve by means of a trunnion controlled b y a set-screw which permits t h e t u b e as a whole t o be tilted a t a n y angle. -4 vertical adjustment is provided for b y a set-screw a t t h e outer extremity of t h e arm. T h e rear of t h e telescope t u b e carries a shield, X X , pro\-ided with clips t o hold t h e source of light when electricity is used a n d is slotted t o hold a rod a n d a movable l a m p carrier when gas is used. T h e source of light may be a n acetylene jet or a n electric l a m p . When acetylene is used t h e gas m a y be obtained from a generator or from a prestolite t a n k . T h e support for t h e lamp is a rod which locks into the slot in t h e shield of t h e illuminator. On t h e rod is placed t h e movable carrier for t h e source of light, see B , Fig. I . T h e n electricity is used t h e l a m p is carried in a socket fixed in an insulated metal hood a n d held in 13Ianufactured by Bausch and Lomb, Rochester, K Y
96
T H E J O U R N A L OF I N D U S T K I A L A N D E N G I N E E R I N G C I € B M I S T R Y
Vol. 6, No.
2
I
Prc. ,-,I
FIC. 1-B
position with refcrence t o t h e lenses of t h e condensing train by clips fastene.d t o t h e shield of t h e illumiuator; see A , Fig. I . The current may be obtained from a n accumulator or by cutting down t h e lighting current. A lamp bank t o reduce a I I O volt current is wired as in Fig. 3. T h e lamp resistance needed for t h e various candle power 6 volt tungsten miniature lamps is: Two 3 2 a n d one 16 c. p. carbon lamps for a 6 volt, 16 c. p. tungsten miniature. One 3 % a n d one Y c. p. carbon for a 6 volt, 8 c. p. lamp. One 3 2 , or tsvo 16, a n d one J c. p. carbon lamps for a 6 volt, 6 c. p. tungsten miniature.
One 16 a n d one 4 c. p. carbon for a 6 volt, 4 c. p. tungsten. Any of these candle power tungsten lamps m a y be used h u t t h e one recommended is t h e 6 volt, 16 c. p. lamp known as “Headlight Mazda, No. 68, 1 2 G., candelabra base.” T o get t h e light f r o m t h e condensing train through t h c objective use is made of a device known as a “vertical illuminator,” K in Fig 2 . This device screws into t h e barrel of t h e microscope below t h e hanger which carries t h e condensing train. Turning t h e plate d of t h e illuminator t o some desired angle reflects the illuminating r a y , which enters t h e aperture, down upon t h e surface of the metal. This in t u r n reflects t h e light up through t h e barrel t o t h e eye. A “quick-acting nose piece” is fitted t o t h e lower end of t h e vertical .illuminator. This device permits
FlO. I--e
of a ready change of objectives without a n unscrewing motion a n d consists of a clamp operated by a spring controlled b y two handles. Pressing t h e handles opens t h e clamp and permits t h e insertion of a ring, one of which is provided for each objective and t o which it has been previously fastened. The camera, see Fig. I , is connected with t h e barrel of t h e microscope by a t u b e which slips in and out like t h e draw t u b e of t h e microscope and may be removed with t h e same ease. The camcra moves with, a n d becomes part of t h e barrel and any degree of focusing is possible. T h e distance between t h e eye piece and t h e ground glass is a constant so t h a t t h e amplification is standard for each magnification. T o use t h e camera t h e draw t u b e of t h e microscope is removed and t h e tube of t h e camera inserted.
The apparatus lends itself readily t o all forms of metallographic work and is adapted t o t h e needs of t h e inspector, t h e engineer of tests a n d t h e metallurgist. It m a y be used in t h e mill or t h e laboratory a n d i s equally adapted for t h e s t u d y of t h e mass, Figs. 4, 5 a n d 6 , or t h e small specimen. It is used both for visual examinations a n d for making photographic records. It is portable, self-contained a n d compact. METALLOGRAPHIC xE?nons SAMPLING.-B~sampling is meant t h e location a n d number of areas t o be polished. It is not necessary nor practicable t o polish t h e entire surface of t h e mass provided t h a t a sufficient number of small areas be taken which shall properly represent it. I n selecting these areas i t is desirable t o follow some fixed rule a n d a1ways.prepare t h e surface at definite positions which shall be t h e same for t h e same kind of objects so a s t o be of value for comparison. This is especially desirable when grain size is t o b e taken i n t o consideration a s t h e grain m a y vary greatly i n different parts of t h e work as from t h e thick t o t h e thin parts of a casting.
F e b . , 1914
T H E J O C R N A L O F I , V D C S T R I A L AArD E N G I N E E R I S G C H E M I S T R Y
I n billets t h e cross section a t each e n d should be t a k e n , together with several areas parallel t o t h e direction of t h e work a n d preferably on t w o or more sides. With rounds prepare a cross section a t each e n d a n d several others parallel t o t h e direction of t h e work. With flats t a k e along t h e center lines of t h e several sides. With hollow forgings a n d similar material areas along t h e outer a n d inner surfaces i n t h e direction of t h e work should be chosen together with t w o or more cross sections a t each end. With castings both thick a n d t h i n p a r t s should be selected a n d where t h e cope a n d drag can be distinguished, sections along each should be t a k e n together with areas i n those p a r t s which have t o t a k e t h e major p a r t of a n y sudden load, as trunnions. Sections should never be prepared t o o near a n y distorted p a r t as a sheared edge or punched hole. With annealed material, especially with castings There t h e soaking has been prolonged, care should be t a k e n t o get below t h a t p a r t decarbonized b y t h e action of t h e flame.
FIG. 4
FIG. 5
T h e size of t h e sections polished should be a b o u t three inches wide b y a b o u t twelve inches long. POLISHING.-This is done b y wheels a n d buffs driven b y a n electric or a pneumatic grinder. one or t h e other of which is usually t o be found in a n y mill. When preparing a surface t h e following t r e a t m e n t has been f o u n d satisfactory for most purposes: If t h e surface is very rough grind down with a 24 grain emery wheel, follow with a cloth wheel charged with 60 emery, t h e n use a similar wheel charged with 1 2 0 emery, follow with a buff charged with washed flour emery paste a n d finish with a buff charged with rouge. T h e above procedure requires a b o u t ~j minutes t o finish a n a r e a 3 inches b y 1 2 inches a n d will give a surface t h a t is perfectly satisfactory if t h e etching is done with picric acid or iodine. It is n o t necessary t h a t t h e surface should be free from scratches b u t i t is necessary t h a t t h e scratches should all lie in t h e same direction.
97
CLEAiVISG.--After polishing a n d before etching clean t h e surface with cotton moistened with alcohol or gasoline. ETCHIsG.-*ifter cleaning, t h e surface is now ready t o have its structure developed. This is usually done b y means of some reagent which a t t a c k s or colors some constituent of t h e metal more t h a n it does others. F o r t h e ferrous metals a I O per cent solution of picric acid in gj per cent alcohol will be found t h e more useful. Soak some absorbent cotton in t h e solution. T a k e up t h e cotton with a pair of tongs or tweezers a n d allow t h e excess acid t o drain off. Place t h e cotton on t h e surface t o be etched a n d move i t back a n d forth till t h e desired d e p t h of etch is obtained. T h e degree of temperature affects t h e speed of etching, t h e colder i t is t h e longer t h e time; with j j t o i o degrees of temperature a b o u t 20 seconds is sufficient. After etching wipe off t h e acid with cotton or clean, soft waste, t h e n clean thoroughly with cotton moistened with alcohol. Care must be t a k e n t h a t t h e etching fluid covers t h e
FIG 6
whole area a n d t h a t t h e saturated cotton is moved back a n d forth with a rapidity sufficient t o insure t h e even distribution of t h e acid over t h e surface a t all times as otherwise there m a y be variations in t h e character of t h e etch which m a y give rise t o false conclusions. This variation i n t h e etch is less likely t o happen with picric acid t h a n with other etching mediums. T H E VIs u A L Ex A MIPI’A T I 0 s .- Wi t h t h e unaided eye look for streaks or areas which are differently colored. Carbon-rich areas will usually appear darker a n d carbon-lean areas lighter t h a n t h e rest of t h e surface. I n general t h e segregations of t h e alloy elements will also be indicated b y a color difference. Heat a n d forging cracks are commonly rendered visible as well as pipes, seams, shakes, flow lines, cold shuts, welds, etc. When making t h e microscopic examination t h e ins t r u m e n t should be leveled, if necessary, by means of t h e screws on t h e stage.
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T H E JOUR-V-4L O F I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
T h e field should be clear, distinct a n d free from a n y haze, glare or image of t h e lamp. Should a n y of these appear t h e illumination is faulty a n d must be corrected. T o adjust t h e illumination t h e condensing train a s a whole should be raised or lowered so t h a t t h e plane of its lenses is centrally in line with t h e opening of t h e vertical illuminator. Then shift t h e angle of t h e mirror in t h e illuminator, or t h e source of light. It is recommended t h a t b u t three sizes of objectives a n d one size eye piece be used, a 32 mm., a 16 m m . , a n d a n 8 mm. Bausch & Lomb objective a n d a 7 . 5 s eye piece. These will give magnifications of 3 0 , 6 j a n d I j o , respectively. Where higher magnifications are desired eye piece magnifications are preferable t o t h e use of higher powered objectives a n d a magnificatibn of 31 j can be obtained with a I j x eye piece a n d t h e 8 m m . objective. Care should be t a k e n t h a t t h e entire area etched should be gone over a n d t h a t p a r t selected for t h e photograph should be strictly representative. PHOTOGRAPHISG.-when inserting t h e camera it is advisable t o rack t h e t u b e of t h e microscope well up away from t h e surface of t h e metal before removing t h e draw t u b e a n d attaching t h e camera. This will prevent t h e chance of damaging t h e objective b y jamming i t against t h e metal. 9 f t e r attaching t h e camera i t is brought in focus by t h e coarse adjustment. T h e rod Y , in Fig. 2 , is brought squarely down on t h e pinion head a n d locked with t h e set-screw; this prevents a change of focus when changing plate holders. F u r t h e r should t h e t u b e rack too easily, tighten i t b y setting down t h e screws holding t h e pinion of t h e coarse adjustment. T h e final focus is fixed with t h e fine adjustment, t h e sharpness of t h e image as seen on t h e clear spot of t h e ground glass being determined with a pocket magnifier. All photographs should be taken with t h e eye piece in t h e camera a n d it will be found convenient t o have t w o 7. j x eye pieces, one for t h e draw t u b e of t h e microscope a n d one t o be kept in t h e t u b e of t h e camera. The plates used should be fast a n d give good color values a n d t o this end Seed’s “ L Ortho’‘ are recommended. The size of t h e plate is 3 ’ ’ ~ X 3l inches a n d t h e image is about 31/4 inches. T h e t i m e of t h e exposure depends upon t h e character of t h e surface a n d t h e plates used. For steel, using t h e above plates i t will not average over I O seconds. After exposing i t is always well t o verify t h e focus by looking through t h e ground glass and thus make sure t h a t i t has n o t been overrun as a result of changing t h e plate holder. DEVELOPIKG.-The plates may be developed in t h e ordinary way with a n y of t h e developers on t h e market. It is suggested t h a t “ I n g e n t o edinol hydrochinon developing t a b l e t s ” be used because of their a d a p t a bility for dish a n d t a n k developing a n d for printing. Where a d a r k room is not available a n Ingento changing bag will be found a n efficient substitute while loading a n d changing plates. Such a bag together with t w o t a n k s makes i t possible t o develop a n d fix t h e plates without leaving t h e work,
*
1’01. 6 , NO.
2
For t a n k developing in addition t o t h t Ingento developer referred t o t h e following formulas may be used for 20 minute developing a t 60 t o 70 degrees: Hydrochinon. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 grains 400 grains Sod. sulfite (anhydrous). . . . . . . . . . . . . . . . . . . . . . . . . . Sod. carbonate (anhydrous) . . . . . . . . . . . 390 grains Water. , , , , , , , . . , , , . . , . , , ........... 30 ounces
T o each p a r t of this stock solution a d d three p a r t s of water before using. Edinol.. . . . . . . . . . . . Sod. sulfite (anhydro Sod. carbonate (anhydrous). Water.. . . . . . . . . . . .
................ ................ .................. ................
145 grains 300 grains 300 grains 40 ounces
To each p a r t of this stock solution a d d three parts of water before using. T h e plain fixing b a t h of 4 ounces of ‘ ( h y p o ” t o 16 ounces of water may be used with any of these formulas; t h e following is, however, t o be preferred: TVater., , , , ,
.... Sod. sulfite..
,
..
96 ounces 2 pounds 2 ounces
Sol. 2
4
Chrome alum..
,
( Sulfuric acid.. , ,
32 ounces 1,’d
ounce
Dissolve I a n d 2 separately, t h e n slowly pour z into with constant stirring. It s h o t l d be remembered t h a t for t h e permanency of t h e negative, a complete fixing followed b y a thorough washing a n d a slow drying is a n essential. Occasionally prints are desired as soon as possible. Then t h e plate after fixing may be quickly rinsed with water, soaked in alcohol a n d dried in I j minutes. After t h e prints are made t h e plate should be washed thoroughly in water t o remove a n y traces of t h e fixing b a t h which m a y remain a n d again dried. C A R E O F NEGATIVES.-The negatives should be k e p t in envelopes plainly marked with sufficient d a t a :o identify t h e m a t a n y time. Most micrographic negatives contain areas t h a t are n o t needed or are out of focus. It will be found convenient t o use a mask t o c u t out such p a r t s when printing from them. Time will be saved if each negative is matted o u t permanently. To this end i t will be found convenient t o prepare a template out of 1/16” sheet steel or brass which shall be a 3 inch square with a Laying t h e template 2i; 16 inch circular central opening. a n d a suitable piece of paper on a sheet of glass a n y number of masks may be quickly a n d easily cut with a sharp knife. One of these masks is t h e n pasted ,on t h e film side of t h e negative t h u s always ensuring t h e same field. PRISTING.-hy of t h e gaslight papers may be used. The glossy papers give better detail b u t they are liable t o be scratched during manipulation a n d require squeegeeing t o get t h e best results a n d are t o this degree not so desirable as t h e velvet or satin finishes. I n printing. n-here electric light is available, a printing or developing lantern as shown in Fig. 7 mill be found convenient. Throwing t h e switch, one way gives t h e exposure, t h e other way gives t h e developing light. With two I O O c. p. hIazda lamps t h e time of exposure will rarely exceed 1 2 seconds. The prints after developing should be thoroughly fixed and washed a n d preferably dried between blotI
F e b . , 1914
T H E J O I - RS.4 L 0 F I S D C7ST RI .-I L A S D E S G I S E E RI S G C H E M I S T R E'
ters. If t h e y are needed quickly t h e y m a y be soaked in alcohol a n d dried within I j minutes. RECoRDs.-It is always well t o make notes a t t h e time of t h e examination as t h e eye is better t h a n t h e best of photographs. T h e records should include remarks as t o appearance, opinion as t o what t h e area indicates a n d other details. Note t h e number a n d description of t h e piece, location of t h e area examined, t h e etching medium a n d t h e time of etching, t h e number of t h e objective a n d eye piece a n d t h e magnification. T Y P E S bF S T R U C T U R E The structure of steel m a y be profoundly modified b y t h e r a t e of cooling from a high temperature, t h e degree of re-heating a n d t h e a m o u n t a n d kind of work t o which i t has been subjected. T h e several structures so obtained m a y each be referred t o a type. I n a steel obtained b y t h e simple solidification of t h e liquid metal followed b y a slow a n d undisturbed d
*-
*-j
eau70.I
5
cooling t h e grain size will be large; Fig. 8. If now t h e metal be re-heated t o some temperature below its melting point a n d cooled slowly without mechanical work being applied. there will be a corresponding change in t h e grain; Fig. 9. I n a n y steel, other things being equal, t h e smaller a n d more uniform t h e grain t h e better t h e physical properties a n d t h e size a n d uniformity of t h e grain is influenced by heat a n d b y work. Steel is heated t o give t h e plasticity required for rolling or forging. I t is heated t o relieve internal stress b u t a n improper heating or a n interrupted cool, ing m a y set u p such stresses a n d even cause rupture. It is heated t o give hardness or t o t a k e i t away. T h e higher t h e temperature from which it cools t h e larger will be t h e grain. Heating t o some certain temperat u r e will give t h e finest grain possible a n d all previouslJexisting structures, however coarse, will be obliterated. Heating for a longer period or a shorter time a t too high a temperature. or a long heating a t t o o low a temperature will coarsen t h e structure. Too rapid heating or t o o rapid cooling or a n unequal r a t e of cooling m a y set u p internal stresses a n d cause rupture. K i t h steel castings t h e effect of these conditions is shown by Fig. I O , t h e structure of t h e metal as
99
c a s t ; Fig. I I , the structure as properly annealed; Fig. I 2 , t h e effect of annealing a t too lorn a temperature. 'With rolled or forged material t h e y are shown b y Figs. 13, 14 a n d ~j which show t h e normal grain as properly annealed a n d t h e effect of higher temperatures upon i t . T h e size of t h e grain a n d its uniformity is also affected b y t h e amount a n d kind of work t o which t h e metal has been subjected. Work m a y be applied in t w o ways, hot or cold. H o t working when finished a t some certain temperature gives a small grain and t h e most tough a n d ductile metal. If t h e finishing temperature be too low t h e grain will be more or less distorted a n d if t h e work be carried far enough t h e metal will have a tendency t o become brittle or t o split along t h e direction of t h e work. The higher t h e finishing temperature t h e coarser t h e grain a n d t h e weaker a n d more brittle t h e metal. Cold working distorts t h e grain a n d renders i t fibrous. T h e effect of work can be seen best on t h e cross section. T h u s i n a hammer-forged piece if t h e work be applied during t h e proper temperature a n d is vigorous enough, each blow will penetrate t h e center a n d t h e grain will be practically uniform throughout. If t h e work is n o t vigorous enough, or t h e metal hotter in one portion t h a n in another there will be more or less marked differences in grain a n d there m a y be alternate layers of hard a n d soft metal if t h e heating be followed b y mTork with portions of t h e interior colder t h a n t h e exterior or if t h e work be applied locally when t h e exterior is much colder t h a n t h e interior. Fig. 16 shows t h e fracture of a hammered piece having t h e interior much hotter t h a n t h e exterior. T h e tendency of t h e several constituents of steel t o segregate is known a n d in general t h e y are t o be regarded as elements of weakness. Figs. 17 a n d 18 show t h e appearance of such segregations t o t h e unaided eye after etching; Figs. 19 a n d 2 0 their appearance under t h e microscope. These areas are in general relatively large a n d t h e y can be seen best with t h e lowest powers ; in fact t h e higher powers, because of t h e smallness of t h e field, often fail t o show t h e structural differences between t h e segregated a n d nonsegregated areas. Slag is liable t o be found in a n y steel a n d when sparingly distributed in isolated particles m a y be disregarded. b u t when occurring in a n y amount i t is always a source of weakness. Fig. 2 1 is a n illustration of its occurrence under conditions where it is a n element of danger. Sulfides, Figs. z z t o 2 4 , like slag. may be found in a n y steel a n d when sparingly distributed in isolated or minute particles m a y be disregarded, b u t as t h e amount increases t h e element of weakness increases. S T R L - C T U R E O F S O ~ S D sTEEL.-Steel of normal composition a n d treatment will show after etching a surface free f r o m segregations a n d laminations. The structure will be regular a n d uniform a n d t h e grain will show a gradual increase in size from t h e outside t o t h e center as t h e result of work. The boundaries of t h e grain will be quite regular inloutline with little or n o signs of ingotism, or incomplete grain refining. Slag
T H E J O C K K A L O F I.VDUSTRIAL
100
Fic. 21
xis0
F ~ C .22
xi50
and sulfides arc absent or only spnringly prcscnt and in isolated particles. T h c n cold roiled or drawn the grain will he distorted in those parts affcctcd by the work b u t there will be no cracks or fissures either in or between t h e grain nor a n y “loosening.” S T R U C T U R E 01‘ U N S O U X D smfL.--The ca11ses which may give risc t o unsoundness a n d failure are sand splits, seams, pipes, bioxholes, ravities a n d honeycomb, ai! of which during work are extcnded as cracks. Etching develops these defects a n d usuiilly renders t h e m plainly visibie t o the unaided e y c . Ingotism, incompiete grain refining a n d failure to
I:,,;. i n
X(M
Fir; 2 3
XlS”
Fioll
Pic. 24
XhS
X30
destroy an existing coarsc structure-these conditions if present to a n y extent imply internal stress, lack of cohesion, liability to cieavagc a n d bi-ittieness. Lack of uniformity of t h e grain in which those nearcr t h e center are smaller t h a n those further away from itsuch a structure is common t o material whicli has bcen heated either too high or too long. Too high heating coarsens t h e grnin; Figs. 13, r q a n d T j. I n gencra? any marked lack of iiiiiioriiiity 01 t h e grain implics a lowered resistance t o a rcpcated or a suddenly applicd load. Segregations of certain essentiai components of t h e steel as t h e carbon or t h e alloying eiemcnts--Figs. 1 7 a n d 18-give rise to arcas e:Lch of which have
Feb., 1 9 1 4
THE JOCRNAL OF I N D r S T R I A L . A N D ENGINEERING CHEMISTRY
different physical properties. T h e presence of such areas implies a lack of continuity i n t h e metal, since t h e junction lines between t h e m are more or less sharp; Figs. 1 9 a n d 20. Such areas when under a load have a tendency t o slip one upon t h e other, t h u s setting u p a rupture. Their presence is revealed microscopically a n d macroscopically b y etching. When studying t h e m under t h e microscope t h e use of t h e lowest powers is advised. Layers, streaks or patches of various impurities as slag, sulfide, etc.-all of these are less ductile a n d more brittle t h a n t h e steel. UETHOD OB EXAMIXATIOX
Sample, polish a n d etch. Examine macroscopically f o r pipes, cracks, seam, laps, blow-holes, honeycomb or sponginess, welds, segregations a n d laminations (especially on t h e cross section), flow lines, excessive slag a n d sulfide areas, cinder, etc., Examine microscopically for lack of uniformity of grain, coarseness, ingotism or incomplete refining. Look for slag a n d sulfide areas with reference t o their abundance a n d distribution. CONCLUSION
I t can be shown t h a t a large piece of work can be spot polished in eight or more different places with b u t little, if a n y , more expense a n d t i m e t h a n it takes t o prepare a s t a n d a r d test bar; t h a t there is a relation between structure a n d physical properties. I t follows t h a t given sufficient experience a n d a set of standards, metallographic methods will give information t h a t cannot be obtained conveniently b y a n y other method of inspection. It should be s t a t e d t h a t metallography is not intended t o replace other methods of test a n d inspection b u t t o supplement t h e m a n d t h u s afford a n additional safeguard against failure. 1423 R . St, WASHINGTON, D. C.
MAHONE PETROLEUM Its Recent Origin, and the Origin of Petroleum in General By CHARLESF. MABERY
Received December 22, 1913
Six years ago I was invited t o visit a section of t h e Valley of t h e Mahoning River in Mahoning County, Ohio, where a deposit of petroleum h a d been known in Milton Township f o r several years, a n d where a n open well was still t o be seen from which oozed a small stream of thick oil. At t h e time of this visit, several wells h a d recently been drilled over a n extended area, a n d were producing a considerable supply of oil. B u t on account of faulty operation a n d mismanagement, these wells soon afterward became inoperative a n d t h e entire field was closed until some years later. Several wells were t h e n t o be seen on a f a r m bordering on t h e river valley, t h e property of ilk. R. Wiesener, f r o m which some years earlier oil had been pumped freely a n d sold as a lubricant without refining. On learning of t h e shallow depths a t which this petroleum was reached, m y interest was naturally aroused with reference t o i t s origin, a n d I made several subsequent visits t o become better acquainted with i t s
IO1
occurrence, in connection with a laboratory s t u d y of t h e oil which seemed especially inviting, for i t evidently differed very materially in its composition f r o m t h e other well known varieties of petroleum. It h a d t h e further attraction t h a t , associated with t h e petroleum i n or near t h e river valley, there were extensive beds of high-grade bituminous coal, sections of which in t h e adjoining Township of Palmyra, were mined on a n extensive scale. I n a narrow section of t h e valley, approximately one hundred feet in width, where t h e river h a d cut i t s way down from a considerable height, exposing a n a b r u p t vertical section of t h e geological formations, a vein was exposed, three or four feet in thickness, of partially weathered carboniferous deposits with t h e accompanying shales so friable t h a t t h e y were easily crushed in t h e hands. Analysis showed t h a t these deposits contained nearly fifty per cent of pure carboniferous material. It, therefore, seemed probable t h a t t h e coal a n d t h e oil were of a common origin, which, in connection with t h e shallow depths of t h e oil s t r a t a , less t h a n I jo ft., presented a n inviting opportunity t o s t u d y t h e origin of petroleum a t close range. GEOLOGICAL O C C U R R E N C E O F M A H O N E P E T R O L E U M
T h e Mahoning River rises in Columbiana County, a n d flowing sinuously through Portage, Trumbull, a n d Mahoning Counties, finally enters t h e Ohio River. I n Mahoning C o u n t y t h e valley is a few miles in length, a n d i t s greatest width is 2800 f t . T h e wells drilled for oil v a r y i n depth from 1 3 5 t o I jo i t . ; i n one well t h e oil sand was reached a t a depth of 11; f t . according t o t h e report of t h e driller, t h e surface layer extends i n a depth of 2 0 f t . t o a bed rock of shales t h a t are continuous t o t h e oil-bearing sand. These shales are partly light a n d partly dark in color, a n d just above t h e upper layer, below t h e surface silt is a bed of sand a n d below t h a t a bed of shale impregnated with bituminous carbon. T h e oil sand composed of rather coarse granules of very pure quartz is overlaid b y a soapstone shale 14 f t . thick. a n d i t extends to a depth of roj ft., of which t h e upper coarser layer, 16-18 ft. thick, carries t h e oil above a large volume of water. Below this sand is a bron-n shale sixty feet thick, a n d below this a lighter shale extending t o t h e Berea Grit. So far as i t appears from t h e 2 j or more wells t h a t have been drilled b y t h e hIahone Oil a n d Gas Company, there are no restricted pockets i n t h e oil s t r a t a , b u t a somewhat regular anticlinal a n d synclinal formation, t h e anticlinals approximately 2 0 f t . in height a n d On account of t h e inertness 200-300 f t . in diameter. of t h e crude oil, special care is necessary in drilling, a n d particularly in pumping: i t is raised with some water into large settling t a n k s a n d t h e water drawn off. T h e daily yield from a single well is small; t h e largest daily o u t p u t from a n y one well has been 8 barrels. There is evidently nothing especially striking in t h e formations connected with t h e occurrence of this petroleum, except t h e shallow depths at which t h e oil is found, a n d t h e absence of a n y complicated conditions connected with i t s origin. As mentioned above, t h e Berea Grit appearing in
