Sept., 1913
T H E JOURLVAL OF I N D G S T R I A L AND EA’GIA‘EERI“L’G CHEMISTRY
a n d t h e Finance Committees of the Federal Congress. T h e injurious action of wood alcohol on t h e general health a n d eyesight of working people handling i t in the industries was strongly emphasized a t these hearings by manufacturers employing it, workmen a n d experts. T h e United States a n d practically every state in the union have specific laws against t h e sale of wood alcohol as a beverage, or as a n addition t o beverages. I n thickly populated communities t h e fear of detection is lessened, hence cases of adulteration are more numerous, especially where there is foreign cheap labor. T h a t fact (especially in New York a n d New Jersey) coupled with a f e w cases of serious poisoning by wood alcohol in varnishing brewers’ vats, which are not properly ventilated, caused the New York State Factory Investigating Commission t o look into the wood alcohol situation. T h e Commission invited Professor Baskerville of t h e College of the City of New York, then Chairman of the Committee on Occupational Diseases in the Chemical Trades of the A-ew York Section a n d chemical adviser of t h e Committee on Occupational Diseases of the New York State Labor Association a n d now Chairman of t h e Committee on Occupational Diseases of t h e American Chemical Society, t o make a report on “Wood Alcohol.” This report, based on a thorough investiga-
I
713
tion of t h e literature a n d extensive inspection of works of all kinds where wood alcohol is made a n d used in various ways, we have been privileged t o abstract previous t o final publication by the State, which abstract appears elsewhere in this issue. The full report may be secured by writing to t h e Commissioner of Labor, Albany, N . Y. Wood alcohol presents a unique case for legislation, not only on account of its general resemblance t o ethyl alcohol, b u t especially on account of the word “alcohol,” which has a definite meaning t o the chemist, but is more associated in the lay mind with “drink.” Methyl alcohol is used extensively a s a valuable solvent and in the manufacture of many important materials. I t s legitimate use should not be throttled. T h e present laws in regard to its use as an adulterant of beverages or in a n y preparation intended for internal use or external application on the human body are in most states now adequate, but they should be more rigidly enforced. Where inadequate, we trust t h a t reasonable legislation, such as is recommended in t h e report referred t o above, may be enacted. At present, however, we insist upon t h e rigid execution of the laws as they exist before further encumbering the codes.
ORIGINAL PAPERS THE MICROSTRUCTURE OF STEEL CASTINGS B Y WIRTTASSIN Received July 23, 1913
I N T R OD U C T I 0 N
This paper deais with t h e results of some metallographic investigations of steel castings. All of t h e micrographic work was done i n t h e machine shop on t h e castings themselves, not on small sections cut from them. T h e work was undertaken during t h e course of what is planned t o be a fairly comprehensive study of t h e relation between structure a n d physical properties of steel in the mass, a n d intended for use as a guide b y t h e Inspector a n d Engineer of Tests. T h e present paper gives t h e results of the work on Tropenas steel castings, a n d is intentionally made as non-technical as possible. INFLUENCE O F ANNEALING O X STRUCTURE
A steel casting in t h e “green,” especially when of a complicated shape, is always liable t o be under internal strain. I n order t o relieve these strains annealing is resorted to. This process has a marked effect upon t h e structure of the metal. T h e structure of a steel casting in t h e “green,” i. e., as i t leaves t h e mold, is coarsely crystalline a n d exhibits t o a greater or less degree a regularly arranged network, t h e meshes of which usually intersect a t some angle of a n octahedron (Fig. I ) . This structure is known as “ingotism.” Heat-treating such a casting breaks down this original crystallization and, if properly carried out, effaces it. T h u s in a properly annealed casting t h e coarse crystal-
line structure gives place t o another which is finegrained a n d of a uniform distribution (Fig. 2 ) . T h e degree t o which this change takes place is limited by the temperature reached, its uniformity, t h e time t h a t it is maintained, the rate of cooling, a n d the size a n d shape of t h e casting. Given the proper temperature, but let t h e time be too short t o permit of a complete re-arrangement, t h e structure will be analogous to t h a t seen in Fig. 3, in which the original structure is readily traced by t h e parallel grouping of the new crystallization. With a still shorter time period there is only a partial recrystallizing, a n d more or less of t h e original network is visible (Fig. 4). Let t h e time be long enough, b u t the temperature be too low, there will be again a partial re-grouping with more or less of the original crystallization present (Fig. j ) . Let the temperature be right b u t the time period be t o o long, all traces of t h e original structure will be destroyed, but in place of the fine granular structure seen in Fig. z there will be a much coarser one (Fig. 6) characterized by the large-sized areas of a certain kind. Let the temperature be too high a n d the increase in size of certain areas become marked (Fig. 7 ) . RELATION O F STRUCTURE TO PHYSICAL P R O P E R T I E S
T h e character of t h e structure bears a relation t o t h e physical properties of t h e metal in t h e casting, the finer t h e grain, t h e more uniform its distribution a n d t h e freer it is from occluded foreign matter as slag, sulfide, oxide, etc., the better will be the physical properties.
Fro. I. X
65
Fm. 2. X 65
Fro. 3. X 6 5
x 65
Pia. 6 . X 65
FIG. 4.
x 65
Plr. 5.
FIG.'^.
X 65
Fro. 9. X
150
FIO. 10.
X
150
Fio. 13. X 150
Pic.
12.
x 150
Sept., 1913
T I I E J O U K S A L OF I.\'IIUS?'KJAL
A S 1 1 EArGIATEERIiVG C H E M I S T R Y
715
with a low resistance t o shock and t o suddenly applied loads. The microstructure of such castings commonly shows t h e presence of slag, sulfidcs, oxide arid other impurities. Typical illustrations of this are to be seen in Figs. 16 and 17. The following examples (Figs. 1 8 - 2 0 ) give the type of t h e structures as obtained from four or more places on t h e casting. The physical vaiucs were obtained from coupons cast on and part of t h e casting. The photographs are of t h e same amplification with a magnification of I jo. These impurities play a n important p a r t as a cause
The following examples (Figs. 9-1j) give t h e type of t h e structures as obtained f r o m four or more diffcrent places on each casting. The physical values given i v c r c obtained from a coupon j. j" X 3. j" X r . j " cast on a n d part of t h e casting and placed, i t \vas heliered, so as t o represent neither t h c best nor t h c worst of t h e casting b u t t o give t h e average of the piece. The castings were spot polished, etched and photographed in t h e shop with t h e portable mctallographic outfit (Fig. 8) described by t h e writer in Melalburgical and Chemical Engineering, 11, 56-8. All t h e photographs are of t h e same amplification
TABLE I Analysis
Mark Tenrile 71,356 Fig. 9 . . . . . . . . . . . . . . . . Pig. 10. . . . . . . . . . . . . . . . 70,991 Fig. 11 . . . . . . . . . . . . . . . . 70.791 Fi8.12 . . . . . . . . . . . . . . . . 70,620 Fig. 13 ................ 69,980 Pis. 14 ................. 72.000 ~ i 15 .~. . .. . . . . . . . . . . . . 73,000
Yield point 38,832 38,489
39.~02 39,216 39,205
3~,ono 4o.000
Elong. 23.75 19.25 16.75 14.00 12.00 10.75
Red 34.72 23.26
8.50
1n.on
i8.m 15.75 14.50 11.50
with a magnification of I jo and are directly comparable with one another. Tho castings werc made b y t h e same process h u t in widely separated heats.
PIG.
I t will be noted t h a t these structures are all referahie t o one or t h e other of the types previously shown as resulting from t h e conditions of annealing. Annealing, however, is not t h e only factor t h a t influences t h e physical properties, for, given good annealing practice, i t is not infrequent t o find a casting
C 0.31 0.31 0.31 0.37 0.31 0.31 0.31
M"
0.63 0.61 0.59 0.60 0.60 0.67 0.62
-
Si
S
0.27 0.29 0.29
0.07i
0.044
0.073 0.072 0.069 0.069 0.065 0.054
0.043 o ,040 n ,040
0.29
0.28
0.28 0.28
P
0.013 0.040
n ,044
of failure. T h u s in Figs. 2 1 and 2 2 , from castings which have failed in service, and which are areas some distance away f r o m t h e point of actual rupture, i t will be noted t h a t there arc minute cracks in t.he grain
8
and t h a t these cracks start in and follow the line of the impurities. In Fig. 23 t h e cause of the rupture is clesrly indicated. CO.YCLUSION
One, more, or all of t h e several structures here illustrated may be found in a n y one steel casting.
Mark Tensile Pis. 18. . . . . . . . . . . . . . . . ~n.nnn Fig. 19 . . . . . . . . . . . . . . . . 71.400 pig.20 . . . . . . . . . . . . . . . . in.9nn
Y i e l d point
el on^.
Red
36son 37,480 35,150
I2..50
16.25 13.25 17.40
10.50 13.75
If, as is generally the casc, t h e coupon be gated t o the casting, or be cast on the heavy part, or on the drag, i t will rcpresent the hest vslnes of the rnctal, whcn,
C
Mn
Si
S
P
0.35 0.38 0.32
0.65 0.68 0.64
0.2Y 0.29 0.28
0.070 .065 0.071
0.040 0.042 0.045
the microstructure of the casting and its physical value. I t can be slioam t h a t a casting may he spot polished
Fld. 16
Fro. 15. X 150
Fie. 17
310. 20.
x isn
Fra.
18.
x
pro.21.
in fact, the average value of t h e casting may be such t h a t it will have b u t little resistance t o sudden strains. It has been indicated that there is a relation between
n
150
x isn
Pro.
19. X I 5 0
Ptc. 22. x
150
in eight or more different places with b u t little, if any, more expense and time than i t takes to prepare a standard test bar.
.
Sept., 19x3
.l,
T H E J O U R N A L OF I N D U S T R I A L A i i D E Y G I S E E R I S G C H E M I S T R Y
It follows t h a t , given sufficient experience and a set of standards, the metallographic method will give information t h a t cannot be obtained conveniently b y
PIC. 23.
any other manner of test. It becomes, therefore, an additional safeguard i n the inspection of important castings. 1423 R Sr.. N. W. WASHINGTON, D. C.
LUBRICATION WITH
OILS, AND GRAPHITE
WITH
COLLOIDAL
By CBIRLBSF. M ~ B H R Y Received July 14. 1913
I n a paper‘ published three years ago, an account was given of some results o n the comparative efficiency in lubrication of oil lubricants, and oils carrying colloidal2 graphite. It appeared in all t h e tests therein described t h a t a lower coefficient of friction was given b y the use of graphite t h a n b y t h e use of oils alone, t h a t oils supported a much greater pressure with t h e aid of graphite, and especially t h a t the graphite film was capable of sustaining the friction of a heavy pressure f o r a long period after the supply of lubricant was s h u t off, Much attcntion has since been given t o various features of lubrication with colloidal graphite, especially in attempts t o ascertain t h e actual economy of its use in replacing oil lubricants. The observations t o be described in this paper present high economic cffcicncy and a remarkable durability of a graphoid surface. (For a definition of this term see page 7 2 2 . ) It has long been felt t h a t lubrication with oils under heavy pressures is an artificial system, for t h e friction is supported by a thin film of oil which must scparate completely and continuously the bearing surfaces. If this film he in. t h e least broken, even in minute places, there will be a catch between t h e metal surfaces with greatly increased friction, as shown by higher temperatures as well as by higher coefficients. This uncertainty in oil lubrication depends on an inherent weakness of thc hydrocarbons which constitute the main body of petroleum lubricants, assuming ‘ t h a t they have been separated from the crude oil without decomposition in the process of refining; they are few in number, and members of a limited series reprcsented mainly b y the general formulas CwHm, C,H,,.,, and C%Hsm-.. The limited number of hydrocarbons in these series is shown by the fact t h a t they may be collectcd within comparatively narrow limits of temperature during distillation, provided, of course, * T ~ i Joualin~. s P, 11s: Journal of the American Sarirlg of Mcchonirol Enginrrrs, January, 1910. At the time of the former publication the term “defloeeulatcd“ wwhich had b-en iound to be altogether different in it. properties from the other well known forms. Further study demolistrated its colloidnl gudity.
used to deripnate this iorm of
7‘7
that decomposition is avoided. The stability of these hydrocarbons diminishes in a somewhat regular manner with the increase in complexity of composition, until a point is reached where the oils cannot be distilled without cracking even in YOCUO. This variation in stability appears in their use as lubricants, especially under irregular conditions of friction and temperature. But so long as the temperature is kept down and t h e bearings have a properly even surface, the hydrocarbons of suitable viscosity serve as durable luhricants. Under uneven conditions of friction they are liablc t o immediate decomposition even t o carbonization. This complete decomposition is frequently observed especially in the extremely variable conditions of automobile lubrication. I n fact the demands of modern locomotion with unprecedcnted high speeds, such as in automobile racing, uneven loads, and t h e variable changes of highway traffic, have reached a. burden of lubrication t h a t no oils, mineral, vegetable, or animal, are capable of supporting. Carbonization in automobile lubrication is an occurrence of common observation, and oils are rated on t h e basis of a socalled carbon test, which shows certain differences in stability depending on a difference in t h e composition of the oils, and also on the method of refining. N o oils can withstand the irregular operations of certain automobile practice without carboniaing t o a greater or less extent. Lubrication with oils is based on the quaiity of oiliness, or grcasiness t h a t is inherent in the hydrocarbons poorer in hydrogen mentioned above. It is not strictly defined by viscosity as ordinarily determined. Whilc the molecules have a certain freedom of motion within the body of the oil attended with a cansequcnt inherent friction, they have also an attraction for external surfaccs on which they may form an attachment, b u t preserving their continuity and freedom of motion even under high pressures and high speeds, thus forming, under constant conditions, a continuous and a durable film. Engler’ in referring t o oil lubricants statcd t h a t “ D a s Schmiermittel par Excellence” is not known, b u t t h a t for every special use a lubricating oil must be selected on the basis of its viscosity; t h a t since for variable combinations of pressure and speed, there is no definite standard, the viscosity must be dctermined for any set of conditions in practical operation. It may be said further t h a t viscosity as ordinarily determined is not always reliable for determining t h e quality of a lubricating oil for any stated condition, for the reason t h a t i t is possible t o prepare a n oil lubricant b y compounding a heavy .distillate with a lighter one, leaving out t h e middle fraction, in such a manner as t o give any viscosity desired as determined b y the viscosimeter. But in the use of such a lubricant there is a tendency of the lighter constituents t o creep and evaporate, leaving t h e heavy constituents between the hearing surfaces. It is evidently possible t o determine the presence of any considerable amount of the lighter constituents by determining t h e flashing point of t h e oil, b u t this test is scarcely sufficient to I
Das Erdod. Leiprig. 191% I). 83.
