methods, suitable types of Fe, methods of melting, and melting control are discussed. R. B . C.
R a t e o f a u s t e n i t e t r a n s f o r m a t i o n i n c a s t i r o n .
D. W . M u rp h y , W . P. W o o d , and D. G i r a l d i (Trans.
Amer. Soc. Met., 193S, 2 6 , 173— 191).—The macro- grain-size p attern appears to be a trace of a condition arising soon after solidification is complete. A fine network structure representative of the austenitic grain size on reheating and outlined by nodular troostite has been developed. The macro- and micro- network structures are parallel in a given series, i.e., irons of coarse macro-network p attern show also the coarse m icro-pattern. Differences between the hardened structures of deep- and shallow-hardening cast hons are associated with wide differences in the austenitic transform ation rates. The fine-grained, shallow-hardening irons transform much faster a t 548°
th an do the coarse-grained, deep-hardening types. In general, the ra te of transform ation of austenite a t 548°
is much slower th an th a t for plain C steel. R. B. C.
I n i t i a l s t a g e s o f g r a p h i t i s a t i o n [ o f c a s t i r o n ] .
H. A. Schwartz and M. K . Barn et t (Trans. Amer.
Soc. Met., 1938, 26, 358—366).—A reinvestigation was made of the course of the tim e-graphite curves for cast Fe, with special reference to the interval when little graphite has formed. I t is shown t h a t . the previously established relation in which graphite cc (time)? m ay be preceded by an interval in which graphite increases very slowly, oc tim e. This interval is probably th a t considered by other investigators to be an incubation period before the s ta rt of any
reaction. R. B . C.
M i c r o g r a p h i c a n d t h e r m o m a g n e t i c s t u d y o f s p i e g e l w i t h c a s e s o f a b u n d a n t p r o d u c t i o n o f g r a p h i t e . J . S e i g l e (Rev. F ind. Min., 1938,
143—152, 176— 182).—A detailed review.
P. G. McC.
G a s e o u s m e d i a f o r c a r b u r i s i n g . G. T. W i l lia m s (Trans. Amer. Soc. Met., 1938, 26, 463—492).—
The properties and utility of commercially available carburising gases, and gas reactions in the carburising
chamber, are reviewed. R. B . C.
F a c t o r s g o v e r n i n g s e l e c t i o n o f t y p e o f c a r b u r i s e d c a s e . A. L. B o e g e h o l d and C. J . T o b in
(Trans. Amer. Soc. Met., 1938, 26, 493—514).—The stresses imposed on autom otive parts, e.g., crushing, bending, and abrasion, which determine the depth and character of the case required on the various components are discussed. R. B . C.
I n f l u e n c e o f o x y g e n o n a g e i n g o f i r o n a n d s t e e l .
A. B. W i l d e r (Met. and Alloys, 1938, 9 , 119—123, 145—14 8 ).—Tests on the quench and strain age- hardening of several low-C steels and Armco Fe after heating in 0 2 are described. Some of tho alloys were also examined after carburising. The results indicate th a t carbide pptn. is m ainly responsible for increase in hardness on quench-ageing, and oxide pptn. for the ageing after cold-work. L. N.
I n f l u e n c e o f r a t e o f d e f o r m a t i o n o n t b e t e n s i l e t e s t w i t h s p e c i a l r e f e r e n c e t o t h e y i e l d p o i n t i n i r o n a n d s t e e l . C. F. E la m (Proc. Roy. Soc., 1938,
A , 1 6 5 , 568—592).—Experim ents are carried out to investigate the deformation of those m etals in which
th e stress-strain curve does not im mediately rise a t the onset of plastic deformation and to study the effectof rate of deformation on the yield and subsequent stress-strain curve. The results of previous investigators are confirmed and it is found th a t the rate of deformation has an im portant influence on the stress-strain curve for both ferrous and non-ferrous m etals. I t determines th e stress a t which plastic yielding begins and thus the val. of the lower yield in Fe and steel. The effects of grain size, elastic after-working, and the hardness changes during and after deformation are discussed. Tests were carried out on Armco Fe, two steels, Cu, and high-duty Al
alloys. G. D. P.
M a n u f a c t u r e a n d u s e o f s h e e t i r o n f o r e n a m e l l i n g . J . S. W a l t o n (Sheet Met. Ind., 1938, 1 2 ,
575— 578).-—A review. R . B. C.
I n f l u e n c e o f t h e m i x i n g p r o c e s s o n t h e c o m b u s t i o n o f a i r - g a s m i x t u r e s f o r f i r i n g [ s t e e l ] f u r n a c e s . K . R u m m el (Arch. Eisenhiittenw ., 1936— 7,
1 0 , 505—510, 541—548; 1937— 8, 1 1 , 67—80, 113—
123, 163— 181, 215—224).—The aerodynamics of the gas and air streams in technical steel furnaces have been critically studied theoretically and by th e aid of models with the object of designing a suitable burner to give even and uniform distribution of the heat with max. utilisation of the fuel. The construction of several new types of burners is described and illustrated by diagrams. A. R . P.
C o m p a ris o n of c a rb o n a n d g ra p h ite e le c tro d e s in e le c tric a r c fu rn a c e s fo r s te e l-m a k in g . H.
Weitzer (Stahl u. Eisen, 1938, 58, 542—546).—The m anufacture of electrodes from am orphous C and synthetic graphite is described, and their performance in three furnaces o f capacity 6-5, 7, and 7-5 tons, respectively, compared. The ohmic resistance of the graphite electrode was 20—25% of th a t of th e C electrode. The ra te of consumption of th e latter was almost double th a t of the graphite electrode, whilst power consumption and melting tim e were somewhat higher. F u rth er tho graphite electrode could be loaded nearly three times as h ig h ly ; its use resulted in slight increase in o utp u t and a saving in the cost of furnace refining. W hen compared on a price basis, however, the cost is 3-6 times th a t of the C electrode.
Reference is m ade to an a tte m p t to overcome this difficulty by adapting th e construction of th e arc furnace to th e graphite electrode. C. M. A.
E f f e c t o f r a t e o f c o o l i n g o n t r a n s f o r m a t i o n s o f s t e e l s . I I . F. W e v e r and A. R o s e . I I I . H.
L a n g e (Mitt. Kaiser-W ilh.-Inst. Eisenforsch., 1938,
2 0 , 55—60, 61—65; cf. B., 1938, 660).—II. To
eliminate errors due to superheating and supercooling, transform ation temp, have been determ ined on a series of plain C steels a t low rates of heating and cooling (0-04— 40°/sec.) by means of an apparatus which records electrically expansion versus tem p.
The slope of the curve becomes less steep in the ferrite—pearlite region, b u t steeper in the austenite region, for increasing C content. The contraction due to the pearlite-austenite transform ation is a max. a t about 0-S% C, which is therefore th e probable composition of th e eutectoid, b u t th e superheating
C l . X .—M ETALS; METALLURGY, INCLUD ING ELECTROM ETALLURGY. 1045 and supercooling a t the A l point are independent,
for a given ra te of tem p, change, of the C content.
This transform ation shows much less supercooling th an the austenite-ferrite transform ation, so th a t the am ount of ferrite separated in hypoeutectoid steels diminishes a t higher rates of cooling, whilst the pre- eutectoid cementite form ation in hypereutectoid steels increases under the same conditions.
I I I. A vac. dilatom eter operating photoelectrically has been used to determ ine the expansion-tem p.
curves of a series of C steels a t very low rates of heating or cooling (0-5—8°/min.). A t rates of heating
<2-7°/'min. the superheating of the pearlite-austenitc transform ation is no longer independent of C content, b u t shows a m ax. a t the eutectoid composition. The tem p, hysteresis a t equal cooling and heating rates of 0-5°/min. is 27°, bu t small am ounts of alloying elements aro believed to influence the rato o f tra n s
formation. A. R . Pe.
L o a d -e x te n s io n d ia g r a m fo r m ild s te e l. G.
We l t e r and S. Go6k o w s k i (Metallwirts., 1938, 1 7 ,
571—578; cf. B., 1937, 680).—The view th a t the drop in stress a t the yield point is a phenomenon associated with the testing machine and not with th e m aterial under test is confirmed. The springing of the machine has an im portant influence on the appearance of tho upper yield point, b u t slight eccentricity o f loading has no appreciable effect. The upper yield point may be avoided on machines w ith either mechanical or hydraulic-pneum atic springing, and with thin or
norm al specimens. C. E. H.
E le c tro c h e m ic a l s tu d y of h e a v y -m e ta l s u l
p h id e s , in re la tio n to c o rro s io n of e x tr a - m ild ste e ls . E. He r z o g (Arh. Hem iju, 1938, 1 2 , 8—12).
—In the colls, soft steel|H 20 , 0-In-K C I or 0-1n- H 2S 0 4|sulphides, only MnS activates anodic dis
solution of steel. Corrosion of steel in aq. solutions, and in contact with sulphides, diminishes in the order Cu2S, NiS, CuS, WS, MoS, FeS, MoS2, MnS, FeS2.
R . T . O sc illa tio n t e s t a n d c r y s ta l s tr u c tu r e [of ste e l].
H . Mo l l e r and M. He m p e l (Mitt. Kaiser-W ilh.-Inst.
Eisenforsch., 1938, 2 0 , 15—33).— Changes in the crystal structure of plain C steels have been followed by means of X -ray diagrams taken a t the same point on th e surface of the specimen a t successive stages during the bending test. W ith loads > the alternating stress limit, th e crystallites soon begin to show a progressive distortion which in the immediate neigh
bourhood of th e fracture becomes so extensive th a t the individual points of the diagram grow indistinct in outline and fuse into more or less complete rings (cf. B., 1936, 841). Changes of smaller order of m agnitude were detected w ith loads slightly < the limit, whilst -with alternating loads well below the limit, and w ith static loads, there was no distortion until (in the la tte r case) shortly before breakage occurred. Thus the X -ray diagrams enable prediction to be made as to w hether the specimen will break after a comparatively limited no. of oscillations or will w ithstand a no. large enough for practical use although not necessarily infinite. A. R. P e.
S tr u c tu r e of g ra p h ite a n d c e m e n tite in h y p e r e u te c tic ir o n - c a r b o n a llo y s. H . Gr o b e r and H .
H a n esian n (Arch. Eisenhiittenw., 1937— 8 , 1 1 , 199—
202).—P rim ary graphite in Fe-C alloys has th e same structure as n atural graphite; graphite pptd. from hypereutectic alloys gives sharper interferences in the rontgenogram th an does graphite pptd. from eutectic alloys since the latter is contam inated with secondary graphite o f submicroscopic crystal size. X -R ay exam ination of cementite in pure Fe-C alloys shows it to have no appreciable solvent action on Fo or C ; its lattice consts. a t 20° are a 4-51 ± 0-005, b 5-06 ± 0-005, c 6-72 ± 0-01 A. In hypereutectic alloys solidified in th e white state there is in addition to cementite a constituent which can be considered as spherulitic prim ary graphite; this is attrib u ted to the m etal solidifying first according to the stable system and th en according to th e m etastable system.
A. R. P.
R ev iew of fu n d a m e n ta ls of c a r b u r is in g [steel].
M. A. Gr o s s m a n n (Trans. Amer. Soc. Met., 1938, 26, 427— 442).—Tho equilibria a t th e surface of the steel and the ra te of subsequent diffusion of the C from the surface to th e interior are discussed. Pack- and gas- carburising aro both considered as gas-carburising processes, the gas in the former case being a m ixture of CO and C 02. The equilibria a t various tem p, and w ith various gas m ixtures are reviewed on tho basis of
available data. R. B. C.
S te e ls u s e d in th e c a r b u r is in g p ro c e s s . O. W.
McMullan (Trans. Amer. Soc. M et., 1938, 26, 546—
573).—The general requirem ents of carburising steels, e.g., ability to absorb C to a sufficient depth and quantity, are reviewed. The compositions of S.A.E.
carburising steels are tabulated, and the modifying effects of adding Mn, Ni, Cr, or Mo discussed.
R. B . C.
A c tio n of s o lid [stee l] c a r b u r is in g a g e n ts . H . W. McQu a i d (Trans. Amer. Soc. Met., 1938, 26, 443—462).—The p a rt played by th e charcoal and carbonate energiser in supplying a gaseous carburising medium is discussed. Tho function of the carbonate energiser is assumed to be th a t of supplying C 0 2 when required, and th a t o f tho charcoal th e conversion of C 02 into CO and th e prevention o f accum ulation of C 02 on th e steel surface. R. B . C.
H a rd e n a b ility t e s t fo r c a r b u r is in g s te e l. W. E.
Jo m e n y and A. L. Bo e g e h o l d (Trans. Amer. Soc.
Met., 1938, 26, 574—606).—A steel bar, 1 x 3 in., is carburised for 8 hr. a t 926°, removed from the carburising box, and the cup-faced bottom face of the bar is H 20-quenched. The hardness o f tho b ar is measured a t various points on the surface, after which tho latter is ground off to a depth of 0-015 in. and another set of hardness readings is taken. From the two sets o f readings tho hardening characteristics of the steel are determined. The test discriminates between steels of various compositions and different grain sizes. D ata are given for 13 S.A.E. steels.
R . B . C.
H y d ro g e n d e c a rb u r is in g of p u r e ir o n - c a r b o n a llo y s a n d of allo y s te e ls . W . Ba u k l o h and W.
v o n Kr o n e n f e l s (Arch. Eisenhiittenw., 1937—8,
1 1 , 145— 156).—The rate of decarburisation of pure Fe-C alloys a t 700° decreases hyperbolically with increase in C content b u t above 900° it increases
1046 B R IT IS H CHEMICAL AND PHYSIOLOGICAL ABSTRACTS.—B.
linearly with increasing C content, the slope of the lines being the greater the higher is the tem p. Below 700° decarburisation is determ ined by the ra te of diffusion of H 2 into the m etal and this is decreased by increasing proportions of cem entite; above 700°
removal of C is influenced by tho rate of diffusion of the C, the ra te of diffusion of the H 2, and the ra te of reaction between the C and H 2 as well as by the form in which the C exists. Although carbide reacts more readily w ith H 2 th an does graphite a graphitic structure is m uch more porous th an a eementitic structure an d therefore alloys with th e former structure are more readily docarburised. Tho effect of the presence of Si, Mn, Cr, Ni, W, Ti, and Al on the decarburisation of steels with 0-2— 1-5% C a t 700°, 900°, and 1000° is shown in a series of graphs; even small quantities of these elements have a profound effect on tho decarburisation since the rates of diffusion of C and H 2 are affected considerably by the formation of carbides and solid solutions. A. R. P.
F u rn a c e a tm o s p h e re s a n d d e c a rb u r is a tio n [of ste e l]. J . A. We b b e r (Trans. Amer. Soc. Met., 1938, 26, 515— 545).—Troubles caused b y de
carburisation in furnace atm . the effects of various gases present in th e combustion products of fuel- fired furnaces, and current m ethods for preventing decarburisation are reviewed. R. B. C.
C o p p e r in c a s t ste e l. W. B. Sa i x i t t (Found. Tr.
J ., 1938, 58, 385—387).—D ata showing the com
positions and mechanical properties of Cu steels are tabulated. Cu steels have good casting properties, weld readily, and their yield ratio is high in comparison w ith th a t of C steels. R. B. C.
C ry s ta l o rie n ta tio n a n d in te r c r y s ta llin e c o r ro sio n [in iro n -n ic k e l a llo y s]. J . L. Sk o e k (Z.
Metallic., 1938, 30, 94).—Max. resistance to oxidation in 0 2 and in air a t 3 mm. is shown by thin sheets of ferronickel when the surface crystallites are all approx.
of the same orientation so th a t the sheet behaves like a single crystal. Perm eability measurements show th a t irregularly oriented polycryst. m etal undergoes considerable intercryst. corrosion under these con
ditions. A. R . P.
M a g n e tic b e h a v io u r of h a r d e n a b le f e rritic iro n -n ic k e l-c o p p e r a llo y s. W. Da n nOh l (Z.
Metallk., 1938, 30, 95—99).—Magnetic hardening of the irreversible N i-C u-Fe alloys is shown to be due to re-formation of austenite and the simultaneous pptn.
of Cu from the quenched supersaturated solid solution.
I f the m etal is reheated a t tem p, a t which these two processes occur simultaneously there is an enormous increase in coercivity, e.g., to 328 cersted with the 12 : 15 : 73 N i-C u-F e alloy; on subsequently cooling in liquid air the austenite reverts to ferrite, causing a sharp decrease in coercivity accompanied by an increase in m agnetic saturation and remanence.
Annealing of the alloys in the a f p s y range causes a much more intense separation into two phases of different Ni content th an is produced under similar conditions in Cu-free alloys. A. R. P .
C o m p a ra tiv e to rs io n te s t s on c h r o m iu m - n ic k e l a n d c h ro m iu m -m o ly b d e n u m s t r u c t u r a l ste e ls. W. Bl u t h g e n (Stahl u. Eisen, 1938, 58,
646—650).—Tests were m ade on a series of steels containing C 0-15—0-50% with Cr 1—2% and Mo 0-2—0-4% or Cr 0-5—1% and N i 1-5— 4-5%, using the m ethod of Gottwein and Reichel. The effect of various heat-treatm ents on th e physical properties of each steel is tabulated, and photomicrographs show the effects on structuro. The tests showed th a t, in general, the Cr-Mo steels were a t least equal in m achinability to the Cr-Ni steels, while in m ost cases th e former proved superior. C. M. A.
In flu e n ce of h e a t- tr e a tm e n t on c re e p of c a r b o n - m o ly b d e n u m a n d c h r o m iu m -m o ly b d e n u m - silic o n ste e l. R . F. Miller, R . F . Campbell, R. H . Aborn, and E. C. Wright (Trans. Amer. Soc.
Met., 1938, 26, 81— 105).—The least-square m ethod of analysis for the interpretation of creep d ata was employed. Specimens of a C-Mo steel (C 0-11, Si 0-17, Mn 0-47, P 0-01, S 0-014, Mo 0-54%) were tested for 3000 hr. a t 593° after normalising and after six differ
en t tempering treatm ents. The m ost creep-resistant structure contained a fine shower (groundmass) ppt.
probably of carbides rich in Mo. Specimens showing the greatest change of structure during th e creep test had the greatest tendency to develop an increasing creep rate. Mechanical tests indicated th a t pro
longing the tim e a t tem p, under stress lowers the strength and slightly increases the ductility. In creep tests a t 450°, 510°, and 593° on Cr-Mo-Si steel (C 0-20, Si 0-49, Mn 0-49, P 0-019, S 0-009, Cr 1-56, Mo 0-65%) little change in structure occurred except a t 593° when coarsening of the carbides was noted. A t 593° the annealed m aterial had greater creep-resistance th an th a t which had been normalised and tempered.
R. B. C.
C h an g es in th e s t r u c t u r e a n d p r o p e r tie s of h e a t- r e s is ta n t c h r o m iu m - a lu m in iu m a n d c h r o m iu m -s ilic o n s te e l c a u s e d b y n itro g e n a b s o r p tio n . G. Ba u d e l (Arch. Eisenhiittenw., 1937—8, 11, 139— 144).—On heating ferritic or ferritic-carbide Cr or Cr-Si steels in a h , N 2, or com
bustion gases containing N2 th e N absorbed by th e steel causes the ferrite and carbides to react w ith the form ation of N-contahung austenite; this has no effect on the scaling of the steels a t high temp. I n Cr-Al steels th e N absorbed forms AIN, which is pptd. in th e groundmass before this is converted into N -au sten ite; th e effect of this is to prevent diffusion of tho Al to th e surface to form a non-scaling oxide film, and therefore nitriding of such a steel adversely affects its non-scaling properties and favours local growth of F e30 4 scale. A. R. P.
H e a t- r e s is tin g s te e ls . C. T. Eakin (Iron Age, 1938,141, No. 1, 149—157).—A review. R . B. C.
S tr u c t u r a l s te e ls fla m e -so fte n e d d u r in g g a s - c u ttin g . H. H . Moss (Iron Age, 1937, 140, No. 27, 22—30; 1938, 141, No. 3, 22—27).—I n the flame- cutting of high-C and alloy steels a hardened zone is left on the cut edge, which presents difficulties in the subsequent fabrication. The technique and equip
m ent requhed for flame-softening the hardened surface during the cutting process are described.
R . B. C.
A n n e a lin g [c o ld -ro lled s te e l] s t r i p . T. N.
Keelak (Steel, 1938,102, No. 6, 40—44).—The
heat-C l. X .—M ETALS; M ETALLURGY, INCLUDING ELECTROM ETALLURGY. 1047 treatm ent practices in use a t various mills are
described. D ata for box-type and radiant-tube furnaces, and m ethods for obtaining various types of surface finish, e.g., black, blue, or deoxidised, are
discussed. R. B. C.
S te e ls lo w in allo y c o n s titu e n ts , s ta in le s s s te e ls , a n d a c id - re s is tin g s te e ls . W. To f a u t e (Tech.
Mitt. K rupp, 1938, 6, 17—24).—The mechanical properties, workability, and corrosion-resistance of Cr, Cr-Mn, and Cr-Mo steels and p lated m etals after various refining, annealing, or welding treatm ents are discussed. To obtain good mechanical properties in Cr-Mn steel (8—12% Mn) the Cr should be >15% . The corrosion-resistance of these alloys is not high;
however, th ey can be satisfactorily used for dairy and brewery utensils in place of 18 : 8 Cr-Ni steel. Ni- free steels containing 18% o f Cr or Cr + Mo with low C contents and additions of Ti, Ta, or N b are of general applicability. P lated m etals have good mechanical and corrosion-resisting properties.
R. B. C.
P i t c o rro s io n of s ta in le s s s te e ls . H. A. S m i t h
(Met. Progr., 1938, 3 3 , 596—600)—A pparatus for circulating aq. FeClg over a specimen of steel in order to test liability to p ittin g is described. D ata obtained for a range of stainless steels are given. R. B. C.
C a s e -h a rd e n in g of ste e ls w ith 1 4 % C r. E.
Wi d a w s k i (Arch. Eisenhiittenw., 1937—8, 1 1 , 195—
198).—Two steels 'with 14% Cr and (a) 0-12, (b) 0-45%
C were case-hardened under various conditions and the depth, composition, and structure of the case determined. Above 1000° the C content of th e outer case tended towards a max. of 3 % ; above 950°. tho depth of penetration of the C increased rapidly with rise in tem p, whereas below 950° carburisation rapidly came to a stop, further prolongation of the tim e of heating having no effect on the C content or depth of the case. Above 1000° case-hardening produced a coarse-meshed carbide network, probably owing to pptn. of a Cr carbide along the grain boundaries as the austenite became saturated w ith C. Max. surface hardness in the completely carburised steels was obtained by quenching from S40°; a t higher quench
ing tem p, tho hardness obtained was less owing to the formation of more austenite, whilst with a lower quenching tem p, the stabihty of the hardness on annealing was greatly reduced. A. R. P.
E ffe c t of s u p e r h e a tin g on th e s tr u c tu r e a n d p h y s ic a l p r o p e r tie s of s t r u c tu r a l allo y ste e ls.
A. S c h o b e r l and R. M i t s c h e (Stahl u. Eisen, 1938,
5 8 , 546—549),—Both metallic and non-metallic
inclusions in steel are affected by superheating of the melt. Tests were carried out on basic and acid melts of Cr-Ni case-hardening steels, and on acid melts of C r-N i-W and Cr-Ni-Mo heat-treated steels and on an unalloyed steel casting produced in basic and acid arc furnaces, and also in a coreless induction furnace.
Superheating a t >1600° h ad no visible effect on structure. Photographs of etched sections of steels superheated a t 1640° and non-superheated steels produced under otherwise identical conditions show prim ary and secondary structure in both cases.
E xcept in a narrow rim the columnar crystals in the prim ary structure disappeared after superheating.
Cr-Ni case-hardening steel prepared in the acid arc or basic high-frequency furnace showed a m arked refine
m ent of th o : prim ary structure after superheating.
m ent of th o : prim ary structure after superheating.