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Stone-Working Axe Heads Fabricated by
Convicts at an Early Australian Colony
Leonard E. Samuels

Department of Materials Engineering, Monash University, Clayton, Victoria, Australia
The axe heads are thought to have been manufactured before 1857 b y transported convicts
in a jail at Fremantle, Western Australia, which was then a remote a n d isolated British colony. They were of a type u s e d to quarry a n d dress building blocks from a soft, local limestone a n d h a d been fabricated b y joining o n a central plane b y forge welding two plates of
puddled wrought iron, a central region being left unwelded to form a shaft hole. A sectionof crucible steel was then inset into the bit edge, also b y forge welding (a process known as"steeling"). This procedure obviously required a high level of blacksmithing skill, and at
least a reasonable level of skill h a d been achieved at the Fremantle jail. However, a numberof fabrication abnormalities were present in the axe heads, drawing attention to some intrinsic deficiencies in the fabrication procedure. Examples are the difficulties of achieving
weld bonding in regions adjacent to the shaft hole a n d that of avoiding "burning" in both
wrought iron and steel during the steeling operation. High-carbon hypereutectoid steels
h a d been used in the inserts, b u t they were i n a normalized condition; that is, they h a d notbeen quench hardened as might have been expected if full advantage were to be taken ofsteeling. This may have been d u e to ignorance of quench-hardening heat treatment or to alack of skill in its application, b u t it m a y have been b y choice. It may have been realized thatthe properties of the normalized steel were adequate for the intended use, to which fact oneof the axes examined bears witness, thus avoiding the hazards of quench hardening. Evenin this event, it would be unnecessary a n d even undesirable to use insert steels with carbon
contents as high as those actually used. Their use m a y have been due to ignorance in steel
selection or it m a y simply indicate that smiths in such isolated communities h a d to use
whatever materials happened to b e at hand. © Elsevier Science Inc., 1996

INTRODUCTION
Australia was first colonized b y Europeansin the eastern coastal regions, where England founded a number of prison colonies.
The first a n d the largest of them was estabin 1788 at the site of the present cityof Sydney, one objective being to relieve
the gross overcrowding of jails in the homecountry. Undoubtedly, however, a further
objective was to establish a permanent
presence o n the continent to confirm England's claim to possession. Later, it was
judged that a presence was also needed in

lis'hed

MATERIALS CHARACTERIZATION 37:211-226 (1996)
D
I Elsevier Science Inc., 1996
655 Avenue of the Americas, N e w York, NY 10010

211

the western regions of the continent, but
this time a cost-conscious British government decided to leave settlement to private
enterprise a n d to free settlers. A Crown
Grant was given to a company, Thomas
Peel & Co., and the first group of investorsettlers arrived in 1829 at the southwestern
corner of the Australian continent. They established a town that they named Perth on
the banks of a river that they n a m e d theSwan River and a port at the mouth of thisriver that they named Fremantle. Thesem u s t have been among the most isolated
European settlements of any time. More1044-5803/96/$15.00
PII S1044-5803(96)00129-5

L. E. Samuels

212

over, the settlers were ill prepared for the
local conditions, which turned out to bemuch harsher than h a d been expected, a n dthey were soon struggling for survival,
Consequently, they campaigned for a
supply of cheap, disciplined labor—namely,transported convicts. This arrangement
was eventually agreed to b y the British
government, and the transportation of convicts commenced i n 1850 at a time w h e n it
was being phased out i n the eastern Australian colonies. It continued until as late as
1868. The convict population in the intervening years averaged about 1500, all men,w h e n the free population barely reached10,000. The convicts were used to constructroads a n d a number of substantial publicbuildings for which purposes a large supplyof iron h a n d tools m u s t have been required.
A blacksmith's forge is known to have been
established o n the grounds of a jail complex
at Fremantle, and its site has been identified[P. Bindon, Western Australian Museum,
personal communication, 1994]. Tools were
presumably fabricated and repaired at thissite, b u t the raw materials required would
have h a d to have been imported, almost
certainly from England. Materials of this

1 Omm

lOMM
1•18

a

b

FIG. 1. Side (a) a n d end (b) views of the unused axe head as recovered from the earthing pit. The arrow i n (b) indicates a discontinuity in the blade originating at the shaft hole.

Australian Stone-Working A x e Heads

nature are indeed known to have been imported. For example, the wreck of the James
Matthews, ex. London, which foundered i n1841 while unloading at Fremantle has recently been investigated. Bundles of iron bars
were found among its cargo [1].
Among the buildings constructed b y theconvicts was a large jail barracks at Fremantle, which was completed in 1857. Thisbuilding continued to be in use until quite
recently, w h e n it was decommissioned as ajail and conservation as a jail museum cornmenced. To this end, archeologists investigated a number of sites, one being a pit thath a d been constructed to earth (ground) thebuilding's lightning conductor. The pit was
found to have been filled with a number ofobjects that appear to have been gatheredfrom the scrap pile of a blacksmith's shop[2]. Most of them were axe heads, the majority being of a type that is known to havebeen used for splitting and dressing the local limestones (calcarenites and aoelianites), which were widely used as a building
material. A distinguishing characteristic ofan axe head of this type is the section contour, which is flat o n one side of the blade
and convex on the other.
Two axe heads recovered from the earthing pit were kindly made available b y theWestern Australian Museum for destructive examination. One of them (Museum
Ref. No. 93.503) appeared to be unused. It
contained a manufacturing abnormality,
which was also present in a number ofother recovered axe heads [I. MacLeod,
Western Australia Maritime Museum, personal communication, 1993]. The second
ake head (Museum Ref. No. 93.515) clearlyh a d been used to the extent that it h a d been
irreparably damaged.

EXAM I NATION OF THE AXE HEAIDS
U t \IL) S ED AXE HEAD

Physical Characteristics
The axe head was comparatively flat on
one side a n d slightly convex o n the other213[Fig. 1(a)], as is characteristic of stoneworking axes. The bit edge was squared
and showed n o indication of having beenused. A discontinuity was visible o n theend faces of the blade [arrowed i n Fig. 1(b)]and extended from the eye toward the bit,emerging along part of the length of theconvex blade surface at a position some
400mm from the bit edge [Figs. 1(a) a n d 21.
The head h a d been fabricated b y forge
welding together four pieces of iron or steel(Fig. 2). These pieces were: two plates of
puddled wrought iron [labeled 1 a n d 2 inFig. 2(c)] joined above and below the eyeaFIG. 2. Etched sections of the unused axe head. The
two sections, (a) a n d (b), were cut 25mm apart at
about the midwidth of the blade. The four units fromwhich the axe head was fabricated are identified i n (c).
Note the asymmetric cross section of the head and thediscontinuities extending from both the crown a n d theroot of the shaft hole. The discontinuity in the blade extends to one of the blade surfaces at the position identifled b y the arrow in (a). The grain flow i n the region
identified b y the arrow at the root of the shaft hole in(b) indicates that the two plates from which the blade
was fabricated had not been brought into contact at thisposition. The other arrow in (b) points to a small surface
forging fold. Etched in 10% aqueous nitric acid.

214

L. E. Samuels(shaft hole) to form the blade and poll, respectively; a strip of iron [labeled 3 in Fig. 2(c)]welded to the back surface of the poll; and astrip of steel [labeled 4 in Fig. 2(c); see also Fig.
3] inset into the bit at the working edge.
Blade Body
The microstructure of the plates used forthe blade was characteristic of a puddled
wrought iron,* consisting of a matrix ofequiaxed ferrite grains in which was dispersed numerous elongated nonmetallic inclusions (Fig. 4) with a duplex structure ofa continuous phase of a n iron silicate [darkin Fig. 4(a)] a n d a dispersed phase of aniron oxide [light grey in Fig. 4(a)]. The grainof the forging, as indicated b y the alignment of the inclusions, ran from the poll tothe bit (Fig. 2). The grain size of the matrix
ferrite was reasonably small ( 5 4 , m averagegrain diameter) and uniform throughout
both pieces of iron. The volume fraction of
the inclusions varied in segregated bands[cf. Fig. 4(a, b)], as is usual with wroughtirons, each band representing a different
puddling batch. I n general, however the,volume fraction a n d size of the inclusions
were comparatively large. This iron i n thisrespect was of only moderate quality,
The chemical compositions of the irons(Table 1) were also typical of puddled

FIG. 3. Etched section of the steel insert i n the bit of
the unused axe. The discontinuity extending from theeye bifurcated at the crown of the insert a n d then extended along a path slightly removed from the weld
plane, the location of which is indicated b y the large
arrow. The discontinuity then extended to the bladesurface o n one side of the insert. The small arrows indicate cracks developed in the insert as a result of partial liquation during welding (see Fig. 10). Etched innital.

*Fuddled wrought irons were the dominant engineering structural material for most of the nineteenth century. They were made b y refining blast-furnace castirons b y selective oxidation a t high temperatures inthe solid state, the process being called puddling. The
product was an iron of low carbon content in which
was dispersed a considerable amount of the nonmetallic reaction products of the refining process. As muchas possible of these reaction products was squeezed
out b y hot forging in a n operation called shingling. The
shingling also formed the mass into a rough b a r suitable for further shaping. The particles of reaction
product that remained after shingling constitute thenonmetallic inclusions found in the final product. The
shingled bars were variable in composition a n d inclusion content. A more homogeneous product was madeb y hot forging or hot rolling groups of bars together,
this so-called piling process perhaps being repeated anumber of times. A range of quality grades w a s produced, depending on the skill a n d thoroughness withwhich these various processes were carried out.

wrought irons except that the phosphorus
content was higher than the 0.05% that wasconsidered at the time to b e the upper limit
acceptable for good-quality wrought irons[3]. Itwas thought that phosphorus induced brittleness at ambient temperaturesand hence needed to be kept to low levels,b u t modern work [4] has established thatthese fears were largely unfounded. Phosphorus in amounts of u p to 0.3% actually
increases the tensile strength of low-carbon
irons, particularly after cold working, without deleteriously affecting toughness. It is
not likely, therefore, that the phosphorus
content of the irons in the axe heads would
have detrimentally affected their performance in service. The hardness of the irons

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rielsAustralian Stone-Working Axe Heads

215

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FIG. 4. Representative microstructures of the wrought iron plates used to fabricate the blade of the unused axe
head. Area (a) is representative of bands containing a large volume fraction of nonmetallic inclusions and area (b)of bands containing a smaller volume fraction of inclusions. The base structure in both is composed of small equiaxed grains of ferrite. A duplex structure is visible in the inclusions in (a). Light micrographs; etched in 2% nital.

varied somewhat but was everywhere within
the range listed in Table 1; these values arenormal for wrought irons.
The two plates h a d been forge welded together along the approximate midplane of
the head, a mandrel having been positioned at a n appropriate position to shape
the shaft hole. Separate forge welds thus
would have h a d to be effected to form theblade and poll, respectively (Fig. 2). During
this process, the asymmetric section shapecharacteristic of a stone-working axe wasestablished b y bending one of the plates
farther around the mandrel than the other.
A strip of iron h a d then been welded overthe end face of the poll, the poll having
been upset a small amount i n the process(Fig. 2). The blade h a d been tapered down
to the bit edge and a 4mm X 30mm strip ofsteel inset into the edge.
A few superficial forging laps developedin the blade surface [one is indicated b y an

L. E. Samuels

216

arrow in Fig. 2(b)], b u t otherwise the grain
flow smoothly follows the external contourof the head. The discontinuity visible o n
the end faces of the blade begins at the rootof the eye [Fig. 1(a)] a n d extends along thefull length of the eye. It extends along thec e n t r a l j o i n t plane toward the bit insert,
where it bifurcates to follow the contour of
the insert [Fig. 2(a)] along a plane slightly
removed from the insert-blade interface(Fig. 3). For about half the bit length, thediscontinuity then extends to the blade surface o n one side [Figs. 2(a) and 3(b)]. The
discontinuity at the midplane contains aconsiderable amount of a layered corrosion

p r o d u c t (rust) b u t a l s o contains extensive

patches of a nonmetallic material with a- duplex structure (Fig. 5). This material
clearly was welding slag that h a d n o t been
expelled from the weld plane, as would benecessary to achieve metal-to-metal bonding. t Moreover, the forging grain flow at
the root of the eye indicates that the surfacesof the two blade plates h a d not been brought
into contact in this region [Fig. 2(b)].
The discontinuity is thus primarily a n
area over which bonding was not achieved
during welding, because the surfaces of thetwo plates h a d not been brought into intimate contact. It is possible, nevertheless,that the original forging discontinuity extended during burial owing to expansive
forces induced b y the growth of corrosion
Vorge welding is based o n the principle that two surfaces of a solid will b o n d if they are pressed together
at a suitable temperature, provided that contaminantfilms, such as oxide films, are not present to prevent
intimate metal-to-metal contact. This condition isachieved with iron if the surfaces are heated to a temperature (approximately 1375°C) at which the iron oxide melts (more strictly, flows freely). The temperature
required can be reduced b y sprinkling a fluxing material over the surface. Sand can be used, for example;
this forms a n iron silicate slag that has a lower melting
point than that of iron oxide. The welding temperature is then about 1175°C. (Pudclled wrought irons are
self-fluxing in this manner because they contain inclusions rich in iron silicate, which, w h e n molten, can illssolve iron oxide.) The surfaces have to be pressedfirmly together when the welding temperature has
been reached, preferably with a shearing action to
help to break u p a n d expel the molten oxide or slagfrom the weld plane.

Table 1

C h e m i c a l C o m p o s i t i o n a n d Hardnesso f t h e M a t e r i a l s U s e d t o Fabricate theU n u s e d A x e HeadBlade

C a r b o n , wt.%+

Silicon, wt.%*
M a n g a n e s e , wt.%*
Sulfur, wt.%*

Flat
side

Convexside

Bit
insert

0.025
0.13
0.03

0.06
0.14

0.86
0.08
0.05
0.01

Phosphorus, wt.%*

0.01
0.22

0.03
0.01
0.24

H a r d n e s s , HV(10)125-145120-125

0.03
285+ Analysis by Analabs Ltd., Western Australia.
*Analysis by Chemistry Centre, Department of Minerals andEnergy, Western Australia.
products within the discontinuity. The hifurcated parts of the discontinuity adjacentto the bit insert, for example, h a d not beenpart of the original welding discontinuity
b u t developed subsequently b y fracture.
Expansion resulting from the growth ofcorrosion products is the most likely driving force for such a process.
A discontinuity was also present along
the weld plane at the poll side of the shaft
hole eye [Fig. 2(a)]. This discontinuity extended from the root of the eye for u p tohalf the depth of the poll [Fig. 2(a, b)] andwas largely filled with a material that had a
duplex structure similar to that illustrated
in Fig. 5. Layered corrosion products werealso present. This discontinuity can again
be attributed to failure to bring the two surfaces into intimate contact when welding
was being attempted.
Cover Strip, Poll Face
The strip welded over the face of the poll
was approximately 2mm thick and cornDosed of two pieces of different materials.
One was a puddled wrought iron containi n g a n u n u s u a l l y small volume fraction of
nonmetallic inclusions [Fig. 6(a)]. The hardness of this material was 125HV(10). The
other was a low-carbon steel estimatedfrom its microstructure to contain 0.2%C[Figs. 5, 6(b) a n d 7]. Most likely, it was aI(tAustralian Stone-Working A x e Heads

217

F I G . 5 . Section through the discontinuity in the blade of the unused
axe. A n area located close to the shaft hole isshown. The duplex structure of the nonmetallic material in the discontinuity indicates that it is welding slag thatwas not expelled from the weld interface. Light micrograph; etched in 2% nital.

piece of decarburized crucible steel. Its microstructure consisted of fine-grained ferrite a n d a small volume fraction of degenerate pearlite (Fig. 7). The hardness of this
/
•

%

: .

material was 285HV(10). The degenerate
structure of the pearlite can be attributed toa low manganese content, which is to be expected in a crucible steel derived from a1..'-' _..Y1',..i...,-V'V e.::•tr . ••••. • •,,,,,,,,-*•,,,..
,.„,f--i.
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FIG. 6 . Microstructures of the two materials used in the strip covering the back surface of the poll of the unused
axe. The section plane is parallel to the poll surface. (a) This structure is characteristic of a puddled wrought ironbut contains a n unusually small volume fraction of nonmetallic inclusions (cf. Fig. 4). The grain of the inclusions isparallel to the back face of the poll; that is, perpendicular to that in body plates. (b) This structure is characteristicof a low-carbon steel in the slowly cooled condition. The material contains networks of inclusions that are probably a result of partial liquation during forging. Light micrograph; etched i n 2% nital.

L. E. Samuels

218

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FIG-7. Microstructure of the low-carbon steel used in the cover strip on the poll of the unused axe, a matrix ofsmall equiaxed grains of ferrite a n d colonies of degenerate pearlite. Light micrograph; etched in 2% nital.

wrought iron. Oxide inclusions arranged in
networks [Fig. 6(b)] also were present inthis material, probably as a result of partial
liquation during welding, a phenomenon
that will b e discussed later. The weld bonds
between the two constituents of the strip
and between both of them and the main
body of the axe head were good.
It was common practice, i n iron works,a n d presumably also in blacksmith shops,
to forge together miscellaneous scraps ofiron and steel that h a d accumulated about
the works [3]. The product was called bushelled iron. Presumably, the objective of thepoll cover strip was to negate deleterious
effects of the end grain that would otherwise have been exposed at this surface. In
this event,, the use of a low-grade productsuch as a bushelled iron would have been
acceptable, particularly if the material contained few nonmetallic inclusions, as d i dthe material used in this axe head.
Insert, Bit Edge
A steel strip h a d been inset b y forge welding along the full length of the bit edge
(Figs. 2 a n d 3), a common practice withwrought iron edged tools before the adventof cheap steel-making practices toward theend of the nineteenth century. The practice
was known as steeling a n d was designed touse the relatively expensive steel only
where it was actually needed. It also afforded the advantage that a hard b u t perhaps brittle steel would be supported b y a
tougher backing, thus reducing the probability of fracture in service.
The strip was first tapered to an edge a t
its upper end, which enabled it to be
blended smoothly into the wrought ironblade plates between which it was sandwiched (Fig. 3). It appears that it was normal practice to shape bit inserts in this w a y[5, 6]. The layers of wrought iron that coyered the sides of the insert were comparatively thin a n d were thinner o n one sidethan the other (Fig. 3). It was through thethinner side that the midplane discontinuity extended to the blade surface (Fig. 3).
The insert was inclined at an angle of 1-2°
to the midplane of the head away from its
convex side (Fig. 3), a n d it seems that thiswas a consequence of the procedure used
to develop a n asymmetrical section i n theblade. The inclination would perhaps have

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Australian Stone-Working A x e Heads

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been advantageous when side dressing
stone blocks b u t not w h e n cutting blocks,
A fully bonded weld h a d been achieved
completely around the insert (Figs. 3 a n d8). Diffusion of carbon h a d occurred acrossthe weld plane, resulting in carburizationof the adjacent wrought iron and decarburization of the steel, each to a depth of
125µm (Fig. 8). This diffusion is characteristic of forge welding because the weld regions remain at high temperatures for alengthy period of time. The austenitic grain
size in the diffusion zone was small (50µmaverage grain diameter). Large nonmetallic inclusions in the wroughf iron immediately adjacent to the weld plane h a d been
fractured into small segments (Fig. 8), another characteristic of forge welds.
The steel of the insert can be taken to be a
crucible steel.t Chemical analysis indicatedthat regions remote from the bit edge andthe weld plane contained 0.85%C (Table 1).
It also indicated that the manganese content was low compared with that of mode m steels b u t was of the magnitude to be
expected in a crucible steel made from a
puddled iron. The phosphorus content also
was low, much lower than that of thewrought irons used for the blade (Table 1).
It was the practice to select irons with low
phosphorus contents when manufacturingtCrucible steels, sometimes called cast steels, weremade in two stages. First, carbon was diffused into thesurface of puddled wrought iron bars b y heating u p to
1100°C for several days while buried in charcoal in an
airtight container. This stage was called cementation; it
is called carburization in modern terminology. The carburized iron bars were undesirably inhomogeneous.
The carbon content varied with depth a n d the inclusions of the parent wrought iron were either stillpresent or replaced b y cavities. A more uniform product was made b y melting the carburized bars in small
crucibles, the melt having been cast into ingots thatwere then hot rolled to final shape. This was the principal method used to make steel in England from the
middle of the eighteenth century to the late nineteenth
century, during which period England was the world's
major supplier of quality steels. In the late 1800s, thecrucible process began to be replaced b y large-scalecheaper processes in which cast iron was refined in
the liquid state. Nevertheless, the crucible processcontinued to b e used for quality steels until well into
the twentieth century.

219

steels b y the cementation route because
phosphorus greatly reduces the rate of carburization. The phosphorus contents oftypical English wrought irons were undesirably high from this point of view, so it
was normal practice in England to use selected Swedish irons as the starting material for crucible steels [7, 8] The low silicon
content of the insert is characteristic of a
product originating from a pig iron produced i n a charcoal blast furnace, which
also points to a Swedish source. It can beconcluded that the steel used for the insert
was of high quality for the time.
The microstructure of the insert steel inregions remote from the bit edge consistedof thin grain boundary allotriomorphs of

FIG. 8. Section of the forge weld between the wroughtiron (right) and the steel insert (left) at the bit of theunused axe. The weld line is indicated b y the lightetching b a n d (arrows). Good bonding was achieved
along the weld a n d diffusion of carbon occurred
across the weld plane from the steel into the wroughtiron. Note that the inclusions in the wrought iron adjacent to the weld are much smaller than those remotefrom the weld [cf. Fig. 3(b)] because the original inclusions were fragmented by the strains imposed during
welding. Light micrograph; etched in 2% nital.

220

L. E. Samuels

10 xi mFIG. 9. Representative microstructures of the bit insert steel of the unused axe. (a) A region close to the crown of
the insert. Thin grain-boundary allotriomorphs of proeutectoid cementite surround colonies of fine lamellar pearlite. (b) A region close to the bit edge. The proeutectoid phase is ferrite, only a small volume fraction being present.
Light micrograph; etched in 2% nital.

proeutectoid cementite surrounding c o b nies of fine lamellar pearlite [Fig. 9(a)]. The
steel thus appears to be slightly hypereutectoid, which is consistent with the ana-lyzed carbon content. The austenitic grain
size was comparatively small (approximately
50µ,m average grain diameter). The volume
fraction of proeutectoid cementite decreased

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FIG. 11. Mi
FIG. 10. Microstructure of the crown region (identified b y a n arrow in Fig. 3) of the insert in the unused axe. The sert and cL
crack a n d cavities indicated b y the white arrows are the result of partial grain boundary liquation during welding. wrought in
The weld line is indicated b y the black arrows. Light micrograph; etched in 2% nital.
at the time.

Australian Stone-Working A x e Heads

221

as the bit edge was approached until thestructure became near-eutectoid [Fig. 9(3)].
The carbon content in these regions is estimated from this microstructure to be approximately 0.75%. Thus slight decarburization of the steel h a d occurred toward the
bit edge during manufacture. Nevertheless,the hardness of the insert steel w a s reasonably uniform throughout, being in therange 280-290HV(10).
A noteWorthy feature of the insert wasthat partial grain boundary liquation h a doccurred in a localized region remote fromthe bit edge (Fig. 3). In modern terminology[9], the steel h a d been burnt in this region
during heating for forging. As a result, networks of oxide-filled cracks a n d occasional
cavities are present (Fig. 10). These liquation structures establish the locations of theaustenitic grain boundaries at the time offorge welding the insert a n d so establishthat the austenitic grain size of the insert
steel immediately after forging was about
1mm. This in considerably larger than thatcurrently existing (about 50p.m), from which
it can be deduced that the axe head musthave been subjected to a grain-refining heat

treatment after forging. The current microstructure suggests that the head h a d beenheated to 800-850°C (austenitized i n modern
terminology) a n d then cooled in air (normalized in modern terminology). Note thata n attempt h a d not been made to quench
harden the insert steel. This would have required that the insert region be quenched
i n water after austenitizing. A recognizably
different distinctive microstructure and amuch higher hardness would have been
produced.
A n unusual structure is also present in
the wrought iron in a region adjacent to theone in which burning occurred in the bit
steel. The nonmetallic inclusions in the iron
were relocated in a network around what
can be presumed to have been the austenitic grain boundaries that existed at thetime a n d temperature of forging (Fig. 11). It
seems that the inclusions melted, penetrated along the boundaries while molten,
and then subsequently solidified at theseboundaries. This structure can also be taken
to indicate that an undesirably high ternperature was attained locally during the insetting operation. This structure indicates• • • • • ••
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FIG. 11. Microstructure of a region in the wrought iron blade of the unused axe adjacent to the weld to the bit insert a n d close to the area at which partial liquation h a d occurred in the insert. Nonmetallic inclusions in thewrought iron appear to have melted a n d penetrated along the austenitic grain boundaries that existed i n the ironat the time. Light micrograph; etched in 2% nital.

L. E. Samuels

222

that the grain size at the forging temperature was considerably larger than that fromwhich the current microstructure was generated, again indicating that the materialh a d been subjected to a grain-refining heat
treatment after forging.
Steeling
The unused axe head was steeled b y insetting a strip of high-carbon steel, b u t advantage h a d not been taken of the possibility of quench hardening this material. Many
steeled-edge tools and edged weapons manufactured through the centuries have been investigated, and the steeling in most, b u t notall, has been found to have been quench hardened and often also to have been tempered after hardening [5]. Wood-working axes recovered from a remote site in Canada andthought to have been manufactured earlyin the eighteenth century h a d been quench
hardened a n d tempered [6]. The techniquesof quench hardening and tempering werecertainly well known, if not understood, b y
the mid-nineteenth century and were, infact, being used in the routine manufactureof edged tools in England [7]. Moreover,the implementation of quench hardening in
the present instance would have required
only that the edge region be quenched in water instead of being cooled in air after the austenitizing treatment to which the head isthought to have been subjected after forging.
A subsequent tempering treatment would,
however, also have been required with steels
containing more than about 0.5%C.
The question that consequently arises is,
Why was this axe head not quench hardened? It is possible that a decision wasmade not to bother to quench harden thisparticular head because a decision h a d already been made to discard it, because of
the central discontinuity that it contained.
It is also possible, b u t not particularly
likely, that the Fremantle smiths were notskilled in the technique of quench hardening. It is even possible that experience h a dshown that quench hardening was not necessary for axes used to work the soft Fremantle limestones. It was in an attempt toAustraliail S

resolve these questions that a used axe head
was examined.
USED AXE HEAD
The poll face of the axe selected h a d beenhammered to such an extent that the poll
was severely distorted a n d the midplane
weld in the poll separated [Fig. 12(b)]. Theaxe appears to have been used as a wedge,
its edge having being held against the surfaceof the stone being worked and its poll surface then hammered. Nevertheless, theworking edge, which had been sharpened toa convex shape [Fig. 12(a)], seems to havewithstood these service conditions well. A
small spall developed at one position [identifled by an arrow in Fig. 12(a)], but the edge
remains reasonably sharp and no wear of theside faces is evident. This edge may, of course,
have been resharpened repeatedly during thelife of the axe but, if so, not to a great extent,
because very little of the edge region was removed in total. Moreover, the existing edge
must have survived at least the period of service in which the poll finally split.
This axe head is of the same general typeas the unused head and was fabricated by
the same sequence (Fig. 13). The bit insert
was larger (15 X 50mm) than that in the anused axe; as a consequence, it was bettersupported b y the blade [cf. Figs. 2(a) and13]. Full bonding of the insert weld h a dagain been attained, b u t burning of the insert steel h a d not occurred during welding.
The microstructure of the insert steel consisted of discontinuous allotriomorphs of
cementite surrounding colonies of comparatively course pearlite (Fig. 14). The austenitic grain size was similar to that of the unused axe. From this, it can be deduced thatthe carbon content of the insert steel wasapproximately 1.1% (higher than that for
the unused axe) a n d that the insert had
been austenitized at a temperature similar
to that for the used axe b u t that it h a d beencooled more slowly. Consequently, it was
somewhat softer [hardness 205-220HV(10)1.
In modern terminology, it can be said tohave been annealed. Note that, again, it h a dn o t been quench hardened.

FIG. 12. Side (a)emerged at the s
split in the poll.

The bladealong its mid]around the bi
surface at soir
a weld disconiin the blade ai
in service, atmade the mz
had, in effect,b y the service
fractures in b
mote from the,that a blade othis mechanis
weld discontir,

Australian Stone-Working A x e Heads

FIG. 12. Side (a) and e n d (b) views of the used axe head after derusting. The arrows indicate a discontinuity thatemerged at the side face of the blade a n d a chip in the working edge. Note the distortion of the poll surface and thesplit in the poll.

The blade of this axe also started to split
along its midplane, and the split bifurcatedaround the bit insert to extend to the bladesurface at some positions (Fig. 12). Althougha weld discontinuity could have been present
in the blade and contributed to the splitting
in service, a n additional factor probably
m a d e the major contribution. The insert
had, in effect, been driven into the bladeb y the service stresses, thereby developing
fractures in blade material in regions remote from the weld plane (Fig. 13). It seems
that a blade of this type might be split b y
this mechanism even in the absence of aweld discontinuity.

DISCUSSION
The axe heads were fabricated b y joining
two plates of wrought iron b y forge welding. A central length of the interface wasleft unwelded and shaped into a shaft hole,and the blade and polI were formed to an
asymmetric section characteristic of stoneworking axes. A strip of high-carbon steel
was inset into the bit edge of the blade anda strip of low-carbon iron was welded overthe poll surface to cover the end grain of the
body plates. The finished forging is thought
finally to have been given a grain-refining
austenitizing heat treatment; the unused axe

224

FIG. 13. Etched section of the used axe head. The insert h a d driven into a n d begun to split the blade inthis region. Etched in 10% ammonium persulfate.

was probably cooled in air from an austenitizing temperature of about 850°C and the used
axe was cooled somewhat more slowly,
The forging procedure is one that wascommonly used to fabricate axe heads fromwrought iron and is one that clearly required a high level of blacksmithing skills.
A reasonable high standard was achievedin the smithing of the used axe, which appears to have been driven as a wedge b yhammering the poll. The standard of forging in the unused axe, however, was notparticularly high, and it could have been areject forging. In any event, it provides ex-

L. E. Samuels

amples of the difficulties to which the fabrication method was prone.
Perhaps the foremost difficulty was thatof obtaining a bond over the full area of theinterface between the two body plates. A
mandrel must have been inserted between
the two plates during welding to form theshaft hole, a n d its presence impeded, in immediately adjoining areas, the flow necessary to bring the two surfaces into intimatecontact. The consequence was a tendency
for bonding not to be achieved i n these regions. A n extensive unbonded area of thisnature w a s present in the blade of the unused axe a n d may have been the reason
w h y it was abandoned. A much larger
bonded area was obtained in the blade of
the used axe, and this weld withstood severe service conditions without parting extensively. Internal fractures were initiatedin this blade, b u t this appears to have been
the result of the insert being, in effect,driven into the blade. The weld in the pollof the unused axe also contained an extensive unbonded region adjacent to the shaft
hole, the unbonded region occupying about aquarter of the intended weld area. The quality of the weld in the poll of the used axe
could not be assessed, because the weld had
separated in service, b u t it did so only after
the poll had been subjected to severe battering. The need for a poll weld appears to be aweakness of this method of fabrication if
the poll is to be hammered. A n alternative
fabrication procedure has sometimes beenused in which a plate is folded around amandrel a n d a weld made in the blade only,
obviating the need for a weld in the poll.
The unused axe head also contains a n example of a phenomenon common to all
wrought iron implements steeled b y forge
welding; namely, partial liquation at theaustenitic grain boundaries due to a n excessively high temperature. This phenomen o n in known as burning in modern terminology [9]. Melting at the austenitic grainboundaries would commence in an 0.8%C
steel at a temperature of about 1350°C. A
temperature exceeding 1150°C would haveto be attained to achieve a forge weld, so a
blacksmith would have to judge the forg-

AI/stdFIG. 14.
of proeut

ing tenproduce
ing therange 1welds L
content
within tering thrfrom sutemperalvolume .1
features'used axe

could hasert in se
h a d not e:
the insert. perhapl
variabjhjt
process.
The stemed diffe
tent. Then o t quenc
used axe
from an at
e m term in
produce a

MIUMIM1.11411—

Australian Stone-Working A x e Heads

225

FIG. 14. Representative microstructure of the insert steel of the used axe, in which discontinuous idioniorphic films
of proeutectoid cementite surround colonies of course lamellar pearlite. Light micrograph; etched in 2% nital.

ing temperature to within about 200°C toproduce a fully bonded weld without burning the insert. The permissible temperature
range would be larger for iron-to-ironwelds b u t smaller the higher the carbon
content of the insert. Judging temperature
within these limits is n o mean feat, considering that temperature h a d to judged solely
from surface color. A n excessively hightemperature h a d been reached in a small
volume at the root of the insert in the unused axe, a location where the cracklikefeatures and cavities produced b y burning
could have promoted detachment of the insert in service. O n the other hand, burningh a d not occurred in the used axe, in which
the insert was of higher carbon content. Thisis perhaps indicative of a n understandable
variability in the control of the welding
process.
The steel inserts in the two axes examined differ in dimensions a n d carbon content. The common feature is that they were
not quench hardened. The insert in the unused axe was probably cooled in still air
from a n austenitizing temperature (in mode m terminology, it has been normalized) to
produce a hardness of about 280HV. The

used axe was cooled somewhat more slowly
after austenitizing to produce a hardness ofabout 210HV. Much higher hardnesses
would have been produced if the bit edge
h a d been quenched in water from the austenitizing temperature instead of being
cooled in air; that is, if it h a d been quench
hardened. It might seem at first that theomission of this apparently simple change
i n the heat treatment procedure to a large
extent negated the point of steeling the bitedge. Yet the softer of the two inserts apparently performed satisfactorily in theparticular application in which they are assumed to have been used.** Probably,
therefore, the use of inserts in the normalized or annealed condition was deliberatebecause the local smiths h a d learned thatthe result was adequate for the purpose.
The inserts were, after all, twice as h a r d as
the wrought iron in which they were conIt is thought that these axes may also have been used
to split wood. If so, this would only reinforce the conclusions reached here. However, it does not necessarily follow that normalized inserts would perform satisfactorily when working hard stones or when cutting
wood, particularly Australian hardwoods.

L. E. Samuels

226

tamed. Possibly the smiths had even learned
that quench hardening was best avoided because of the distortion and cracking that
could result. They m a y even have learned
that quench-hardened steels of the typeused were excessively brittle in certain applications. Quench-hardened hypereutectoid
steels are brittle in impact unless the proeutectoid cementite is spheroidized before austenitization; austenitization is carried out
within a specific narrow range of temperatures, and quenching is followed b y ternpering at a n appropriate temperature. Sucha sophisticated heat treatment can scarcely
be expected to be implemented b y a blacksmith anywhere, let alone under the conditions that probably prevailed at Fremantle.
In the event that normalizing or annealing was deliberately chosen for the finalheat treatment, it follows that the same
hardness and similar wear resistance [10]could have been obtained with steels of lower
carbon contents (perhaps as low as 0.7%).
Higher carbon contents than this are evenundesirable because, as indicated earlier, thesteels are then likely to be more susceptible
to burning during forging. Crucible steelsof appropriate lower carbon contents wereavailable in England [8], b u t whether they
were available i n Fremantle and whether
these distinctions were appreciated there isanother matter. Perhaps a steel was just asteel in the Fremantle smithy, as it still is insome undeveloped parts of the world such as
Mali [11] and eastern Turkey [M. McConchie,
University of Melbourne, personal communication, 1996]. Perhaps, moreover, thesmiths were forced to use whatever steel
types a n d sections available at the time.
A side effect of steeling was observed in
the used axe; namely, the insert tended to be
driven into the blade, developing internal
splits. The hardness of the insert would haveh a d to be about twice that of the blade forthis to occur, b u t the effect would n o t havebeen greatly enhanced b y a further increasein hardness. It would have been affected tosome extent by the shape of the crown of theinsert. It seems, however, that failure of anaxe is likely to occur b y other mechanisms
before this one becomes significant.
The author is grateful to Dr. I. MacLeod (Head,
Department of Materials Conservation) and Mr
P. Bindon (Head, Anthropology Department),
Western Australian Museum, for supplying theaxe heads investigated and for the information on
their provenance. He is also grateful to Professor
Paul Rossiter (Head, Department of Materials
Engineering, Monash University), for making
laboratory facilities available, and to Julie Fraser,
who carried out the macrophotography.

References
1. G. Henderson, Marine Archaeology in Australia.
University of Western Australia Press, Nedlands,
Western Australia (1986).
2. P. Bindon a n d J.-P. Raynal, Excavations in the Fremantle Jail. Western Australian Museum, Perth,Western Australia (1993).
3. H. D. Ward, "Best Yorkshire" from West Yorkshire.
J. Iron Steel Inst. 210:396-405 (1972).
4. B. E. Hopkins a n d H. R. Tipler, The effect of phosphorus on the tensile and notch-impact propertiesof high-purity iron and iron-carbon alloys. I. Iron
Steel Inst. 188:218-237(1958).
5. R. F. Tylecote and B. J. J. Gilmour, The Metallographyof Early Ferrous Edge Tools and Edge Weapons. BAR
British Series 155, B.A.R., Oxford, England (1986).
6. J. D. Light a n d H. Unglik, A Frontier Fur Trade Blacksmith's Shop. Environment Canada, Ottawa, Canada (1987).
7. K. C. Barraclough, Sheffield Steel. Moorland, Buxton, England (1976).
8. H. Brearley, Steel-Makers and Knotted String. P. R.
Beeley a n d P. J. Beeley, eds., The Institute of Materials, London (1995).
9. L. E. Samuels, Optical Microscopy of Carbon Steels.
American Society for Metals, Metals Park, OH,
p. 258 (1980).
10. W. A. Glasser, Friction and wear of carbon a n d alb y steels. In Friction, Lubrication and Wear Technology, ASM Handbook, Vol. 18, ASM International,
Materials Park, OH, pp. 702-709 (1992).
11. P. Coles, Heat of Invention. New Sci. 148:1998(1995).
Received May 1996; accepted September 1996.