1280
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 18, No. 12
Pressure Lubricants
Special Lubricants
The following lubricants have good adhesive properties, but do not stand up quite so well in contact with strong chemical reagents. However, they are much more stable than the vaseline mixtures generally used.
Where the joints are not subjected to changes in pressure varying greatly from atmospheric, special materials may often be used with a fair degree of success.
(1) Parowax, heavy paraffin oil, latex crepe (2:5:1). Melt the Parowax on the steam bath and add the paraffin oil and latex crepe. Continue t o stir and heat until all the solvent has been removed. The Parowax may be replaced with beeswax, ceresin, or lanolin if a heavier body is desirable. _- ( 2 ) Heavy paraffin oil and latex crepe (3:4). Heat the paraffin oil and latex crepe with rapid stirring on a steam bath until the solvent is all removed. This gives a semifluid lubricant which stands up exceptionally well under heavy pressure. ( 3 ) Beeswax and lanolin (1:2). Melt on a steam bath with constant stirring. (4) Heavy paraffin oil and beeswax (1:l). Melt on the steam bath with thorough mixing until the mixture becomes chilled.
The latex crepe should be dissolved in a mixture of petroleum ether and benzene to form a heavy, viscous liquid before adding to the other constituents. This method gives a clear, homogeneous product without discoloration due to charring which takes place when the solid latex is heated high enough to melt.
(1) Fuming sulfuric (20 per cent SOs) or sirupy phosphoric acid, or even phosphorus pentoxide, may be used t o withstand bromine vapors or acid fumes. However, they lack body and are difficult to apply satisfactorily. ( 2 ) Blackstrap molasses or glycerol may be used where oils, fats, waxes, and rubber may be objectionable-for example, where kerosene is used for dilatometer determinations. ( 3 ) Ordinary petroleum jelly may be used in special cases, but it lacks body and is readily attacked by strong chemical reagents. (4) Deflocculated graphite thoroughly ground with heavy paraffin oil makes a n exceptionally good lubricant for metal joints.
Application
The old lubricant should be entirely removed and in most instances it is preferable to wash the surfaces with a volatile solvent such as ether before applying new lubricant, As a general rule, the smaller the quantity, so long as the film is entirely continuous, the better the results. A thin coating on one surface is sufficient and is usually more evenly applied with the fingers.
Properties of Some Sand-cast Aluminum-Magnesium Silicide Alloys' By Samuel Daniels WAR D E P A R T M E N T , AIR SERVICE, MCCOOK FIELD,DAYTOS,OHIO
The magnesium silicide alloys do not possess valuable the quenching temperature. 2 AGNESIU&I silicide, Mg&3i, takes a place properties in the sand-cast condition, but when The increase in strength and beside the compound quenched and artificially aged those quasi binary alhardness conferred by such loys which contain from about 1.25 to 1.75 per cent of n a t u r a l aging may be enC u A l z i n i t s a b i l i t y prof o u n d l y to affect the methis compound develop an excellent combination of hanced by artificial or acstrength and ductility. The benefits to be derived from celerated aging a t (elevated) chanical properties of alumithe heat treatment of alloys of this composition are temperatures between 100" num alloys, especially after heat treatment. Hanson and to be utilized rather in the wrought materials, of which and 200" C., but with attendthe proprietary 51s alloy is an example. The metalant decrease, as in natural Gaylerz established the equilography of the series is described and illustrated. aging, of the percentage of l i b r i u m diagram shorn in Figure 1, which m a n i f e s t s el~ngation.~~~ that the Al-?rlgpSi alloys form a quasi binary system, Archer and Jeffries4 have described the attributes of the wherein a maximum of 1.6 per cent of MgzSi (I per cent proprietary 51s wrought aluminum alloy, which, containing magnesium, 0.6 per cent silicon) is soluble a t the eutectic 1 per cent each of magnesium and silicon, represents the temperature, 580" C. With decrease in temperature the commercial application of the principles just enunciated. solubility falls, along the line NN,, to not more than 0.5 They state that this alloy differs from a purely silicide per cent of MgzSi a t 30" C. Magnesium in excess of that material in that the silicon content is deliberately in excess amount necessary to form Mg2Si causes rapid diminution of of the theoretical 1.75 Mg : 1Si (Mg2Si) ratio in order to the solubility a t high temperatures; and excess of silicon was compensate for the fact that iron, present as an impurity, reported to exert only little effect upon solubility conditions. may unite with some of the silicon and render it unavailWhen MgzSi has been dissolved and retained in the alu- able for magnesium silicide formation. The properties of minum-rich solid solution by quenching, the alloy is subject 515, depending upon its condition of treatment, embrace a to age-hardening, a process involving the reprecipitation, range in ultimate strength of from 14,000 to 50,000 pounds from the supersaturated solution, of MgzSi in highly dispersed per square inch, in elongation of from 30 to 10 per cent, particles, and adding further increment to the strength and and in Brinell hardness of from 15 to 100. It is the lighthardness, which have already been improved by the quenching. est of the high-strength alloys, having a specific gravity of Hanson and Gayler, working with wrought materials, were 2.69. The present paper is the fourth of a series of investigations' the discoverers of age-hardening caused by reprecipitation of MgzSi, and they pointed out that quenched aluminum- into the properties of sand-cast alloys of the aluminumMg& alloys age-harden a t atmospheric temperature, to an :Institute Mechanical Engineers, 11th Report t o Alloys Research extent dependent upon the quantity of MgzSi in solution a t Committee, 19p1, p. 241,
M
Published by permission of the Chief of 1 Received May 27, 1926. Air Service, w a r Department. f J. Inst M e l d s , 36, 321 (1921)
4
I
Archer and Jeffries, Trans. Am. Inst. Min. Met. Eng ,71, 828 (1925). Daniels, T ~ 1 3JOURNAL, 16, 1243 (1921); 17, 486 (1925): 18, 393
11926).
INDL'STRIAL AA'D E,VGIXEERING CHE-ITISTRY
December, 1926
silicon-magnesium system, undertaken by the Material Section, Engineering Division, Air Service, U. S. A. In it are described seven melts whose magnesium silicide contents were calculated to run from 0.68 to 13.5 per cent, the last alloy being slightly hypereutectic. With these alloys is included melt 2828, containing about 1 per cent each of magnesium and of silicon, which was prepared accidentally and which, on the basis of mechanical properties obtained from it, was recommended for forging and rolling development prior to the issue of the patent6 covering 515 alloy. O;
I 1
1281
crucibles in an oil-fired furnace. The maximum furnace temperature was kept as low as possible and the magnesium WRS added to the bath just before pouring, at about 704' C. (1300" F.). Table I1 outlines the details of the melting practice. Method of Casting Test Specimens
Three molds of Air Service standard TB1 tension test specimens were cast to size (1.28 cm., or 0.505 inch, diameter over the gage length), in an open green sand, from each melt. There are three test bars to the mold, with individual risers and a common pouring sprue. Temperature measurements were made with a base chromel-alumel thermocouple and a potentiometer. Methods of Testing
CHEMICALANALYsIs-The results of analysis, made by standard methods, are given in Tables I and 11. MECHANICAL TESTING-Tensile, Brinell hardness (10 mm. ball, 500 kg. load, applied for 30 seconds), and specific gravity tests resulted in the data of Table IV. The tensile properties represent the average for three bars, but only one Brinell hardness test, impressed on a sanded flat on the grip end of the middle bar in the mold, and one specific gravity determination, also on a sanded grip-end cylinder, were made for each condition of treatment. The sand-cast specimens were tested within 2 days after having been cast, while the heat-treated specimens were tested within 7 days after the completion of heat treatment. Two quenched and aged specimens from melt 2830 and the three from melt 2831 were slightly bowed by the heat treatment and were straightened before the tension testing.
3c04
11; 2
NI
4,
8
6
,
l
10 .
-12
/
14
16
I8
Mg$i per Cent. Figure I-Equilibrium
Diagram for A1-MggSi Alloys (Hanson and Gayler)
Method of Alloying
Eight melts were sand-cast in the form of tension test specimens. The numbers of these melts and their calculated composition follow: Melt 2826 2827 2832 2828 2916 2896 2830 2831
Magnesium Per cent 0.43 0.85 1.0 1.09 1.7 3.4 5.1 R.5
Silicon Per cent 0.25 0.5 0.6
MgaSi Per cent 0.68 1.35 1.6 Excess Si 2.7 5.4 8.1 13.5
1.0
1.0 2.0 3.0 5.0
Table I indicates the composition of the aluminum ingot, of the aluminum-silicon hardener, and of the magnesium metal used as raw materials. The aluminum ingot was of 99.5+ purity; the hardener contained 18.45 per cent of silicon, and the magnesium stick, 99+ per cent of the metal. Table I--Composition of R a w Materials (Per cent) Melt 2063 2370 2415 919
Material Copper Silicon Aluminum /ngot 0 . 0 2 0.14 Aluminum ingot 0 . 0 1 0.09 A1-Si hardener 18.45 Magnesium stick ..
.. . .
...
Table 11-Foundry
Iron 0.28 0.24 0.48
...
Mag- Aluminum nesium (diff.) 99.54 99.66
... ...
-
99.'d+
Practice
(Furnace, Monarch; fuel, oil; weight of charge, IO pounds) r
Melt 2826 2827 2832 2828 2915 2896 2830 2831
Time in furnace Minutes 15 20 20 15 25 25 20 20
TEXPERATURE------
Mazimum furnace C. F. 749 1380 749 1380 732 1350 740 1365 735 1355 730 1345 743 1370 730 1345
-Pouring--
c.
707 707 704 704 70i 702 702 704
7
' F. 1305 1306 1300 1300 1305 1295 1295 1300
The various alloys were made in 10-pound lots by melting the aluminum and the hardener together in plumbago 6
U. S . Patent 1,472,739 (October SO, 1923).
Figure 2
FiCure 6-8.81
Me. 4.95 Si.
X 100
Fisure 7.--R.81 &I*, 4.95 Si. X 100 Primary M&i ill side oi specimen shown in Pi*ii*r 6
npure
'","
cemtage of t.his compound from 0.76 to 1.4 per cent, was iiicreased froom 30 sharply to about 40; and the elongation correspondingly dropped precipitately from 14 to about 5 per cent. Witb still further increments of N g a i the hardness mounted rapidly to about 50, wliile tlie elongation slowly declined to about 1.5 per cent. From tbesc considerations it will be seen that, for an alloy to be used ill tbe cast state, tbc best combination of strength and ductility attaches to a very low magnesium silicide content, which conilition in itself does not m k e for good casting qualitit%. '1'11~ specific gravity of the several alloys decreased wit iiiCrcase in percentage OF Mg& from 2.64 to 2 The frnctures of the specimeiis were silve lraviiig a11 increasingly blue tinge as the quantity of M& becaine greater. M e l t s 2x30 and 2831 were distinctly blue in fracture, tbe latter being semicrystalliiic. HE.AT-TRZATEXI Ai,r,ous-The results from heat treat,nicirt arc oubiirxd iii TdJe I V and in Figure 2 are e o r n p ~ i r d with tbose of t.he materials as sand-cast.
a--m ~ g 4.9s , si. x IOU
14,760-1.M9., Exundissolved psimary ME&!. All other curi~fitiienfspresent except posszhly Si Qurnched and agcd.
cess and
Through quericliiiig and artificial aging the mechanical properties of-all the alloys except those-very poor and very rich in Mg& (melts 2320, 2896, 2830, and 2831) wereimproved. M e l t 28% could not be responsive to heat treatment, for its composition (0.40 hIg, 0.31 Si) p1iict.s it very ncarly in equilibrium at all temperal,ures (Figure 1). Melts 288F, 2530, and 2831 were of inferior strength and ductility, pmbahly because of oxidation. The skin of tbe test spcciinens was porous and blackened. Analysis of the data shows that the effect 05 additions of Mg& in amounts between 1.25 aiid 1.73 per cent was to rove markedly after quenching and aging, upon the igth and ductility of the stmd-cast alloys. nd 2532, of sucli composition, had; after beat treatment, an ultimate strength OF about 30,000 pounds pe: squilre inch arid an elonxation of over 8 p~ cent. The llrincll bardricss of tbese alloys raried between 00 and 65. Melt 2828, not it inagnesiuin-silicide alloy, hut with ab& 1 per cecit each of inngnesiimi a i d of silicunl is the mwt iiitercsting alloy in tbe sarics, possessing, aFt.er quencliiiig and azine. ., an ultimate strenztli of about 31.000 woiiils per squarc inch and an eloiigation of above ti per Archer and Jeffriesl st.& that while "theoretically, the niaxiirium liardeniiig power should be obtained w.ben the ratio of silirun to magnesium is just right to form the compound M&i**' t,be iron content of tho alloy must be Laken into aecount, as ihe iron may combine with same ofthe silicon and render it insoluble. It is, therefore, logical that the silicon content sliould exceed the tlieoretical ratio." This reason does not secm alt,ogetlier complete, for, in the sandcast alloy, a fairly hlc quaiitity of (t.ernary?) outectic silicon is present. Tlic elTect of excess silicon is evidently to increase the strength and decrease the elongat.ion hecause of its own solubility. X o attempt was made to determine whether the solution treatment could be shortened (from a soaking period of 80 hours). It is belicved, and the patent covering 51s alloy indicates, that sand-cast material may be accorded proper solution treabment in somewhat more than 24 hours. It is probably true also that the artificial aging period can be less t.han tlie 8 iiours employed in the present work. hnnealing caused pronounced forfeiture of strengtli arid I
'I'ahlc
1V--Chemical
Analysis and Mechanical AI-MpSI Alloys
Yrvpertlrr
A s Sond-Cost
of
.
..
as26 2X%i
288% 2K2H 24ii
.. .. .. ..
.. .. .. ..
11.860
28.7
11,m
20.2
ll,BXO 11,670
17.7
14.0
20 20 22 22
2.01 a.e4 2.114
2.02
8 As the result of this investigation, this alloy was recommended lor erpcrimrnial devel~~p$nent as B wrought and heaiMreated mntcrid but this was precluded when, shortly alterward, U. S.Pnient 1,472.iYY (Poolnote 0 ) was issued.
x
Figure 9--8.81 Me, 4.95 Si. 100 iOiL32.8-22. All c o n d i t s e e t ~ present, iiiciuding some si
Aiiiiealrd.
~ g 4 .. ~ 5si. 500 AI-MmSi eutectic atlout central hrr of MgrSi
Figure 1x-.n.81 Sand-cast.
Figure 10-0.9 Mg, 0.47 Si. Annealed.
Needles ticks
and
X
roiiiided
500 par-
of MmSi
x
Figure 13-8.81 MC, 4.95 s i . 580 Sand-cast. Duplex iron-bearins needles, binary A l - ~ & i and mixture of AI-Si =aid AI-X, in segrepied zone
hardness and concomitant improvement in ductility, if the new properties are compared with those of the alloys as sand-cast,. The percentage of elongation decreased inversely villi the content d MgnSi. The funnee-cooling of these alloy, especially of those rich in Mg,Si, was very detrimental to the mechanical properties. The visual evidence of this condition was in porous and blackened test specimen surfaces and in oxidized fractures. Metallography
The inetallograplry of thc series is depicted in Figures 3 to 14, inclusive. All photomicrographs are of unetched structures, excepting Figures 11 to 14, inclusive. The st.ructures of melt 2827 (0.90 Mg, 0.47 Si, 0.58 Fe) were very similar, condition for condition, to those of melt 2828 (1.16 Mg. 1.02 Si, 0.56 Fe), beyond the amount of hard compounds formed in tho cast material. Metallographs of the latter melt are shown as Figures 3, 4, and 5. Duplex needles and skeletons (FeAI, cores and X rims) of the ironbearing constiiuents, F e d , and X , werc found somewhat more abundantly in melt 2828 than in melt 2827, and the skeletons tended to be broken up and rounded by heat treatment. The former melt as cast also had more AlMg&i eutectic and more Al.Si, both alooc and ukimately
FIemre 11-8.81 Sand-cast.
Mg, 4.95 Si. Binary eutectic of and M&
x
500
dtminom
Mp. 4.95 Si. x 1000 Rounded eutectic arid priuiaiy (needle) M&i
Figure I+-R.Rl 4nirealed.
associated with Mgai or X(?),but about the same aniount of the blue-gray SiO,. After quenching and aang, no silicon remained in either melt 2827 or 2828 and no MgSi in 2827. In melt 2828, however, a considerable quantity of large, rounded particles of Mg& wm present (Figure 4), representing the excess which was coagulated from the original (binary) skeletons and finely divided (ternary?) particles originally associated with silicon. There was an excess of silicon in melt 2828, which gave such a good combination of strength and ductility after this heat treatment. Although this alloy was heated at and quenched from 552" 6. (1025' F.), at which temperature the maximum solubility of Mg3i in almninum would not ncccssarily be attain&, it appears from the amount of MgSi not dksolved (Fignre 2) that the question of temperature was less import.ant in effect than the excess of silicon, which, itself being retained in solution, apparently lowered the solubility of Mg&, contrary to the findings of Hanson and Gayler.z In the annealed specimens melt 2827 generally resemhled melt 2828. The M@i occurred in moderate quantity 8s small, rounded or acicular particles and the blue-gray coustituent more scantily. Of the iron-bearing compounds the rounded skeleton form, rather than needles, predominated.
I S D C S T R I A L A S D ENGINEERING CHE;MISTRY
December, 1926
No silicon was detected in melt 2827, although it was sparingly present in melt 2828. The loss in strength and the gain in ductility peculiar to the annealed specimens are accounted for by the expulsion of Mg2Si and silicon from solution during slow cooling (compare Figure 5 with Figure 4). Melt 2831 (8.91 Mg, 4.95 Si, 0.60 Fe est.) was the only other alloy examined metallographically. It is nearly of eutectic (Al-MgBi) composition (Figure 6). Besides the abundant binary eutectic (Figures 11 and 12) duplex needles (Figure 13) and skeletons of the iron-bearing compounds, the blue-gray constituent, binary AI-Si eutectic (Figure 13) were the structural features. In the cope part of the tension specimen liquation caused the appearance of pri-
1285
mary Mg&i (Figure 7). The cross section of one of these large hexagonal plates of primary magnesium silicide is shown in Figure 14. Fan-shaped ternary areas containing silicon, such as obtained in melts 2827 and 2828, were absent in melt 2831. Binary AI-Si eutectic in the last melt was always associated with segregated, duplex iron-bearing needles (Figure 13). After having been quenched and aged melt 2831 had no abnormal characteristics. The iron-bearing particles tended to roundness, as did the excess MgzSi (Figure 8); and while the silicon was retained in solution, the blue-gray constituent was unaltered. The annealed specimen showed even more ostensible rounding of MgzSi and a small quantity of particles of silicon (Figure 9).
The Rate of Polymerization of Perilla Oil' By Maximilian Toch and T. T. Ling TOCHBROTHERS, NEW Y O R K ,N. Y.
ERILLA oil is obtained from the seeds of perilla plants which grow in China, Japan, and India. The seeds average 38 per cent of oil. Aside from its edible value, the oil is used in the manufacture of varnishes in the oriental countries. During recent years perilla oil has been imported into the United States. Early investigators'?* reported perilla oil as a valuable raw material for the manufacture of paints and varnishes, but its scarcity and high price have prevented it from being widely used. However, the present demand for the oil has already created a market and there is no doubt that it will be employed more extensively in the future. The analytical constants of perilla oil are very close to those of linseed oil. However, the former is characterized by its high iodine number, 196 to 206, which is the highest among all known drying oils. Many investigators2J have reported different results with regard to the drying properties of perilla oil. Some have found such phenomena as formation of droplets, running into streaks, tendency to creep, and slow drying as compared with linseed oil, while others have not noticed these condit,ions and have taken opposite views. These different results may be due to factors such as the source and species of the seeds, the methods of extraction, and the treatment of the oil. From a number of samples the writers have found that perilla oil generally dries twelve hours sooner than linseed oil, and produces a satisfactory film. I t has been observed that the dried film turns yellow more quickly than that of linseed oil. This is natural on account of the greater degree of unsaturation, as indicated by the iodine number, so that more oxidation products are formed. The chemical composition of perilla oil has not been thoroughly investigated. Bauer4 states that it consists of the glycerides of 88 per cent unsaturated acids and 12 per cent saturated acids. They are chiefly linoleic, isomeric linolenic, palmitic, and oleic acids.
P
Previous Work
Perilla oil is often used by manufacturers of paints and varnishes in the form of "bodied" oil. Bodied perilla oil, like all other bodied drying oils, is obtained by heating the oil at an elevated temperature. The effect of heat upon linseed oil and China wood oil has been thoroughly investi1
Received June 18, 1926.
* Numbers in text refer to bibliography a t end of paper.
gated.'-9 In the case of linseed oil there is an increase in specific gravity, refractive index, and acid number and a decrease in iodine number, while in the case of China wood oil there is an increase in specific gravity and a decrease in refractive index, acid number, and iodine number. In both instances the molecular weights have increased and it is therefore considered as being a polymerization process. Lewkowitsch states that no doubt polymerization also takes place on the heating of perilla oil. GardnerlO heated perilla oil to 300", 400", and 500" F. separately in open beakers for 10 minutes. After cooling, the results of his analysis showed a slight increase in specific gravity and saponification number and a decrease in acid number and iodine number. Bodying of Perilla Oil
The laboratory experiment by Gardner did not attempt to produce a bodied oil which was used by varnish makers. Practically no data on either laboratory or commercial production of bodied perilla oil have been reported. The authors have tried various methods of bodying perilla oil, both in the laboratory and on a commercial scale. A sample of raw perilla oil studied in the laboratory showed the following analytical constants : Specific gravity (20' C.) Refractive index (25' C.) Acid number Iodine number
0.9134 1.4812 3.10 201
Three hundred cubic centimeters of raw perilla oil were heated in a 500-cc. Erlenmeyer flask at a temperature of 580"F. To another lot heated in the same way air was blown through. The rate of the polymerization was checked by the determination of the refractive index of a drop of oil drawn out at quarter-hour intervals. T a b l e I-Refractive I n d i c e s (25" C . ) of Perilla Oil Heated Alone at 580' F. a n d Air-Blown a f t e r H e a t i n g Time Hours Heat alone Heat and air 1.4812 1.4812 1.4817 1.4819 1.4826 1.4827 1.4845 1.4839 1.4849 1.4861 1.4860 1.4873 1.4869 1.4885 1,4879 1.4896 2'1.4887 1.4904 1.4892 1.4913 2L / r 1.4898 1.4919 2 1 ' 1 .... 1.4904 23/4 3 1.4909
....
