862

THE COLLIERY GUARDIAN

May 4, 1917.

SOUTH WALES MINING TIMBER TRADE.

The demand for riiining timber continues very heavy, and
although imports are fairly good, and larger- supplies of
home-grown wood are being utilised, quotations for French
and Spanish fir are firmly held at 74s. to 75s. per ton ex
ship Cardiff, the high figures making matters most difficult
for colliery companies.: For the week ending April 27, the
imports of foreign mining timber into South Wales
amounted to 19,566 loads, the following being the actual
quantities received by consignees:—

Cardiff (Barry and Penarth) :—

To	Loads.

Lysberg Limited ................. 13,920

Morgan and Cadogan ............... 1,500

A. E. Williams ..................  1,080

F. R. Howe and Company ............. 360

Total....... 16,860

Newport :—

Marcesche and Company .............. 480

Franklyn Thomas and Company ........ 600

T. P. Thomas and Company ........... 720

Total.......	1,800

Swansea :—

H. D. Evans and	Rogers ............ 300

W. Davies and Company .............. 106

Total.......	406

Port Talbot :—

Lysberg Limited	............ 500

The bulk of the supplies came from France, but in defer-
ence to the wishes of the authorities, the ports from whence
supplies were obtained have been omitted.

Heavy Demand for Home-Grown Timber.

There is a very heavy demand for home-grown timber
for mining purposes, and although a much larger quantity
has been taken by the collieries, the trade is beset with
difficulties. Chief amongst these is the acute shortage of
labour. As previously stated in these columns, there is a
large amount of wood awaiting transport. The scarcity of
hauliers is so pronounced that several forests are incom-
moded with wood awaiting delivery, some of which was
purchased two months ago. Complaints have been rife of
the irregular sizes of the wood received by colliery com-
panies, which has led to a wide variation in prices. For
instance, sales we’re reported last week of larch mining
timber at 77s. 6d. per ton, or 2s. 6d. above the price of
the best French fir ex ship Cardiff or Newport. This
wood, however, was of exceptionally good quality. On the
other hand, odd lots* of crooked timber were sold at as
low as 27s. per ton. The Monmouthshire and South Wales
Coal Owners’ Pitwood Association asked the various
colliery companies of the association not to purchase home-
grown wood except through the association. This associ-
ation has . notified the maximum prices at which they are
prepared to purchase, viz., 50s. to 55s. for larch, and 40s.
per ton for hardwood, delivered collieries or free on rail.
There is, however, a heavy demand elsewhere, and higher
prices are being realised. The requirements of larch
timber are very pressing in other directions, and merchants
find a very ready sale. Collieries are pressing for
deliveries, whilst land owners are equally desirous of
getting the felled timber removed as early as possible. A
fairly large amount of West of England and Irish timber
has arrived in South Wales ports. The freight rate from
Ireland rules from 13s. 6d. to 15s. A large amount of
cutting is proceeding in South Wales, Monmouthshire, and
adjacent counties, and, with supplies limited, there are
indications of much higher prices prevailing shortly.

OBITUARY.

Mr. A. W. Staveley, of the firm of Gent and Company
Limited, electrical engineers, Faraday Works, Leicester,
died suddenly on the 23rd ult. at his residence in
Nottingham, at the age of 58 years. Mr. Staveley joined
the late Mr. J. T. Gent in 1880, and took an active part
in the management of the business. When the firm was
formed into a limited company, he took the position of
senior director, and continued this office up to the time of
his death.

Capt. A. N. Drysdale, M.C., Highland Light Infantry,
one of the directors of Drysdale and Company Limited,
“ Bon Accord” Works, Yoker, Glasgow, died on April 15
at a casualty clearing station in France from wounds
received in action on April 1.

Mr. Arthur Spencer, a director of the Scottish Iron and
Steel Company Limited, died suddenly at his residence at
Coatbridge on the 21st ult. His father was the founder of
the Phoenix Iron Works at Coatbridge.

We regret to record the death, from heart failure, of
Mr. George G. Ward, deputy-chairman of Davidson and
Company Limited, Sirocco Works. The sad event took
place on the 23rd ult. at his residence at Craigavad.
Mr. Ward, who was 56 years of age, was the eldest sur-
viving son of the late F. D. Ward, and began his business
career with the well-known firm of Marcus Ward and
Company. He joined the Sirocco Works 21 years ago,
and was appointed a director when the company became
a limited concern in 1898.

One of the oldest members of the London Coal Exchange,
in the person of Mr. Geo. J. Wood, recently passed away.
He was for many years hon. secretary of the Inland Colliery
Owners’ Subscription Room. A large number of the mer-
chants attended the funeral on Tuesday last. He was the
colliery representative of the Sheepbridge Colliery
Company.

Capt. W. Marley, of the Durham Light Infantry, son
of Mr. T. W. Marley, secretary of the Horden Collieries
Limited, has been killed in action. He was a partner in
a well-known firm of Newcastle coal merchants and
shippers.

Second-Lieut. Henry Greener, of Craghead, who has been
killed in action in France, was an assistant mining sur-
veyor with the South Moor Colliery Company Limited.

The death is announced of Mr. Andrew Stevenson
Biggart, chairman of Sir William Arrol and Company.

Mr. William Allison, of Ivy House, Birtley, died on
Sunday. night, after a long illness, at the age of 75. He
began life as a pit boy, and finished as a colliery’owner on
his own account, within sight of his birthplace. He had
been on the County Council for 25 years, and has served
as member and vice-chairman of some of the important
committees.

REFRACTORY MATERIALS USED IN

THE IRON AND STEEL INDUSTRY.*

By Cosmo Johns, F.G.S., Sheffield.

With the exception of carbon, and its compounds
with silicon, which have a limited application, the
available refractory substances are chiefly the oxides
SiO2, A12O3, CaO, MgO, Cr2O5, or mixtures of these
with oxides of iron, K20, Na2O, and traces of other
substances, regarded as impurities, some of which may
function as catalysts. The materials available are
therefore strictly limited; they never occur in a state
of purity in nature. Their manufacture into refrac-
tory products involves in many cases sizing, agglomer-
ation, or bonding, and final heating to a temperature
that varies according to the purpose for which the
product is intended and the functions it has to per-
form. The problems that arise are not solved by a
knowledge of the properties of the compounds men-
tioned; they are complicated by the presence of
impurities and the varying nature of the bonding
material employed. The final product, as delivered to
the user, is always a mineral aggregate, often of great
complexity. They possess no fusion point, but rather
a range during which softening, at first incipient, at
last, with increasing temperature, causes the material
to fail to perform its functions. The constituents have
varying melting points, and during heating they
invert, and new phases appear. Some inversions,
involving serious volume changes, should be completed
during manufacture, but often are not. This is not
imputing blame to the manufacturer, for the temper-
atures required for such changes are rarely known,
and even when known as a result of experiments under
laboratory conditions, it does not follow that they
apply to manufacturing processes. The art has been
so long in front of the science of the refractory
industry that the most urgent need at present is for
an expression, in terms of scientific precision, of the
most successful practice in manufacturing the refrac-
tory product and of the physico-chemical changes
which take place when they are used.

Tenacity and Compressive Strength,

Tenacity and compressive strength at ordinary tem-
peratures are valuable only in so far as they permit
the refractory products to be transported and enable
them to withstand the structural stresses to which they
are exposed when used. This is not difficult to attain.
It is when the material is exposed to high temperatures
that the value of these properties becomes most impor-
tant. The abrasion caused by the movement of solid
substances while in contact with their heated surfaces
is important, while the erosion caused by the passage
of dust-laden gases at high velocities becomes serious
in time. Little or nothing is known of the conditions
that favour or retard abrasion and erosion. High
tenacity, which in most cases would mean that of the
bonding or of the most fusible constituent, is most pro-
bably the desired property. It is the surface exposed
to the highest temperature which suffers, for it is the
one that is in contact with the moving solids, liquids,
or gases. Compressive strength is rarely a cause of
failure, for the bulk of the refractory material is at a
lower temperature than the face, and therefore less
affected. There is, however, urgent need for accurate
determination of the two properties under discussion
at wide ranges of temperature for the more important
materials under both oxidising and reducing condi-
tions.

Corrosion Changes.

Not less important than resistance to high temper-
ature with concurrent abrasion and erosion is resist-
ance to the corrosion caused by slag gases. The effect
of acid slags on basic refractories and of basic slags
on acid refractories are familiar, while a most strik-
ing example might be indicated on the marked corro-
sion of the silica bricks in the gas ports and uptakes
in open-hearth furnaces, due to The alternating
passage of oxidising and reducing gases with the
resulting formation of fusible silicates.- A factor con-
ducive to rapid corrosion in the last case is the absence
of large particles of silica in the bricks employed, and
the presence of excessive pore spaces. Here again
little has been published, and few observations
recorded. The effect of the alkalies found in certain
coal on the refractories used in coke oven construction
is serious, and here, too, little is known as to the real
nature of the destructive influences at work.

Volume Changes.

Every element or compound used as a refractory
undergoes changes in volume during heating and cool-
ing. Apart from the fact that these volume changes
may, and do at times, cause disintegration, with the
consequent lessening of the useful life of the material,
abnormal' expansion causes structural difficulties,
while contraction may be even more undesirable, per-
mitting the passage of gases from one part of the fur-
nace to another. In the case of coke ovens, the reten-
tion of gas-tight partitions is absolutely necessary, and
this involves the use of a refractory material which
does not undergo appreciable volume • change. This
apparent contradiction of the first statement simply
means that a mixturef of substances with volume
changes of opposite sign are employed, viz., clay and
silica. But while the contraction of the burnt clay
is fairly- regular with increased temperatures, quartz,
which is the form of silica found associated with it in
nature, has an inversion point at which it becomes
tridymite. In the presence of certain compounds this
inversion takes place at a temperature lower than that
at which coking is carried on. In their absence the
inversion is retarded, and does not take place until a
temperature higher than that usual in coking prac-
tice is attained.

* From a paper presented to the Iron and Steel Institute.

+ See Prof. Fearnsides’ paper, Colliery Guardian,
February 2, 1917, p. 223.

Heat Conductivity.

If the refractory materials used possess a fusion
point or softening range higher than the maximum
temperature to which they are exposed, it would in
most instances be desirable that they should be non-
conductors of heat, for radiation losses would then be
at a minimum. More often the prevailing tempera-
tures approach and sometimes exceed that at which
fusion or softening occurs. In those cases it is neces-
sary to encourage radiation from the surface farthest
removed from the heated surface, in order to cause a
steep temperature gradient from the heated to the
cooler face. In special cases, cooling devices are neces-
sary to prevent the rapid destruction of the material
employed. Good conductivity for heat is most desir-
able where the material is used to form walls which
transmit heat from the burning fuel to the contained
charge which is being heated. The melting of steel
in crucibles and the coking of coal are instances where
a refractory material with good heat conductivity is
required.

Texture and Porosity.

These physical characteristics of refractory materials
determine in large measure their suitability or other-
wise for particular duties. Owing to the complex
nature of most of the materials used in practice, their
properties are not those of the simple minerals of
which they are composed, but the resultant of varia-
tions which are sometimes of opposite sign, and are
always varying at different rates. The relative size
of the grains employed, the extent of the surface
exposed by the more resistant constituents to the
others used as bond or matrix, are most important
factors in contributing to the ability of the material
to perform useful service. Another point of some
importance is the influence of mass in promoting or
retarding inversions. Some of these inversions take
place almost instantly once the critical temperature
has been reached, but with others marked hysteresis
occurs. Porosity must always occur when the refrac-
tory material is composed of more than one consti-
tuent, and where their chief volume changes are dis-
similar or occur at different temperatures.* Little is
known of the effect of porosity on the properties of
refractory materials. That the pores encourage the
deposition of extraneous substances in the interior of
the bricks, and that they render the structure per-
meable to gases, is, of course, obvious.

Stresses Caused by Temperature Changes.

The stresses caused by temperature changes are due
to the volume changes which take place during heat-
ing. If the refractory material happens to be a good
conductor of heat, these are not serious, unless one
face is rapidly heated and the distortion produced
exceeds the tenacity of the material. The remedy
available is to avoid rapid temperature changes, and
whenever possible .to raise the temperature of the
material during the burning stage of manufacture well
above that at which the inversion to which the prin-
cipal volume change should take place, and hold it at
that temperature long enough for inversion to be com-,
pleted. The u spalling ” of magnesite bricks which
sometimes occurs has been thus explained, and it is
certain that the excessive expansion of silica bricks
would be avoided if the manufacturer could ensure the
completion of the quartz-tridymite inversion during
burning. Despite the considerable advances in our
knowledge of the inversions of silica made recently,
their bearing on the problems that face the manufac-
turer are not yet sufficiently clear.

Need for Further Research.

Advances in the art of metallurgy are largely con-
ditioned by the nature of the refractory materials
available. The manufacture of these materials is
based almost entirely on empirical rules and the
experience of the men employed. Such rules are the
result of experiences gained during a century or more
by a rude process of trial and error, but where there
were but very inadequate means of correlation. The
methods employed to-day represent the survival of the
fittest by the searching test of commercial success, but
it by no means follows that they represent the best
attainable. Further progress, if made at all, can only
be slow and uncertain, and by consent it is now
admitted that only by adequate and well-directed
scientific research can such progress be accelerated.
The first step—and in all probability the one easiest to
take—would be to prepare specifications for the most
important refractory products expressed in terms
capable of precise measurement or description, basing
the specification on the best current practice. This
would only be following the excellent example of the
gas industry, which established standard specifications
for refractory materials. But specifications at their
best only serve to stereotype the best current practice
of their day. These specifications should be the start-
ing point of systematic research, which should cover,
not only the problems that occur during manufacture,
but the occurrence in nature and characteristics of the
raw materials. Their concentration and purification,
proximate and ultimate analysis, mineralogical
description, and thermal analysis, are all points on
which additions to our present knowledge would be of
great value. But the refractory materials are so
complex, and the problems involved are so difficult of
direct attack, that any contributions to our knowledge
of the properties of the pure minerals, or of the impure
aggregates which are used in- practice, would be
welcomed, even if their immediate application did not
happen to be possible.

The schedule of the requirements of the iron and
steel industry, so far as the most pressing problems
affecting the use of refractory materials, which is
appended to this communication, is to be regarded as
tentative only. Its most useful function will be to
provide a basis for discussion, in the course of which
it is hoped that corrections and additions will be
made, And thus enable a reasoned statement of the

* See “ Deterioration of Refractory Materials,” by H. B.
Cronshaw. Carnegie Scholarship Memoirs, 1916, vol. vii.