Analysis of the New Metals. Titanium, Zirconium, Hafnium, Niobium, Tantalum, Tungsten and Their Alloys

286 Pages·1966·4.02 MB·English

by  W. T. Elwell and D. F. Wood (Auth.)

ANALYSIS OF THE
NEW METALS
Titanium, Zirconium, Hafnium,
Niobium, Tantalum, Tungsten
and their Alloys
by
W. T. ELWELL
Chief Analyst,
Imperial Metal Industries (Kynoch) Limited
and
D. F. WOOD
Technical Officer,
Imperial Metal Industries {Kynoch) Limited
P E R G A M ON PRESS
OXFORD • LONDON • EDINBURGH • NEW YORK
TORONTO • PARIS • BRAUNSCHWEIG
Pergamon Press Ltd., Headington Hill Hall, Oxford
4 & 5 Fitzroy Square, London W.l
Pergamon Press (Scotland) Ltd., 2 & 3 Teviot Place, Edinburgh 1
Pergamon Press Inc., 44-01 21st Street, Long Island City, New York 11101
Pergamon of Canada, Ltd., 6 Adelaide Street East, Toronto, Ontario
Pergamon Press S.A.R.L., 24 rue des Ecoles, Paris 5e
Vieweg & Sohn GmbH, Burgplatz 1, Braunschweig
Copyright© 1966
Pergamon Press Ltd.
First edition 1966
Library of Congress Catalog Card No. 66-18956
Printed in Great Britain by Blackie and Son Ltd., Bishopbriggs, Glasgow
2778/66
PREFACE
Analysis of the New Metals is an extension of the publication The
Analysis of Titanium, Zirconium and their Alloys, published in 1961.
This latest publication includes methods for the analysis of hafnium,
niobium, tantalum, tungsten and their alloys, and earlier methods
for the analysis of titanium and zirconium have been brought
up to date.
Imperial Metal Industries (Kynoch) Limited, formerly Imperial
Chemical Industries Limited, Metals Division, has had considerable
experience in analysing these new metals, and in furtherance of
Company policy to make available the outcome of its research and
development in this analytical field, procedures currently used in the
Company's laboratories for the analysis of these materials are
detailed in this publication.
One of the functions of the Company's Research Department
Analytical Laboratory is to provide new and improved procedures,
and to ensure by rigorous trial that such procedures are accurate and
reliable. The following are typical examples.
The earlier method for determining boron was based on a pre-
liminary distillation of boron as methyl borate and the subsequent
formation of rubrocurcumin under carefully controlled conditions.
Anyone with experience of this earlier method, particularly in deter-
mining boron below 0-5 ppm, will appreciate the value of the method
now recommended, which requires neither a distillation nor unduly
critical conditions for development of the final colour; the determina-
tion is completed colorimetrically by the formation of an intense
red-coloured compound, rosocyanin.
A new method has also been included for the determination of
zirconium, based on extraction of zirconium ions into tri-n-octyl-
phosphine oxide, followed by the development and optical density
measurement of a coloured zirconium-pyrocatechol-violet complex.
This procedure has a wide application and is particularly suitable for
the determination of small amounts of zirconium (down to about
20 ppm) in niobium.
ix
X PREFACE
On the instrumental side, X-ray fluorescence procedures are
included for the first time, but only sufficient information has been
given to show how such methods are used, and to emphasize potential
applications and advantages of this relatively new technique compared
with many other determinations referred to throughout the book.
The Spectrographic Section has been extended to include the
determination of cadmium, lead and boron in zirconium, and in
other respects this section has now been brought up to date, e.g.
procedures are now included for the direct spectrographic examina-
tion of solid samples.
Atomic-absorption spectrophotometric procedures are now being
applied more extensively to these materials, and there are at least
two determinations where this represents a marked advance over
earlier published methods, viz. in the determination of magnesium
and sodium. In these instances, detailed instructions are given, but
where the advantages to be gained by atomic-absorption spectro-
photometry are marginal, only passing reference is made.
Polarography, in particular square-wave polarography, is be-
coming increasingly important in this field of analysis, especially
when the sample can simply be dissolved and the solution analysed
directly. Polarographic procedures, particularly as applied to the
analysis of zirconium and hafnium, have been extended to the
determination of many more elements.
Present-day trends in analytical chemistry are towards further
instrumentation, but the need for conventional methods of analysis
is not always eliminated with the introduction of an instrumental
method. Most instrumental methods require the provision of samples
of known composition for calibration purposes, and invariably
these samples must be analysed by approved chemical procedures.
It would be wrong to claim that the recommended procedures
contained in this book are the only reliable methods available for
the accurate determination of the constituents in question. The
only claim made is that all the recommended procedures have either
been developed or had their reliability confirmed in the Company's
Analytical Laboratory, and were in use in the Company's Labora-
tories at the time the manuscript was prepared.
The authors have been criticized in one review of The Analysis of
Titanium, Zirconium and their Alloys, for including a chemical
procedure for the determination of oxygen. This procedure is
retained in this present edition, because it may find a useful applica-
PREFACE xi
tion in laboratories where a more expensive vacuum-fusion unit
with all its outstanding advantages cannot be justified.
Imperial Metal Industries (Kynoch) Limited has made significant
contributions to the analytical chemistry of these new metals, and
has published such information in the technical press, but no
originality is claimed for some of the methods described in this book.
Full advantage has been taken of the work of other analysts in
related fields, and this is gratefully acknowledged.
Analysis of the New Metals is intended as a laboratory compendium
containing essential information for the satisfactory analysis of
titanium, zirconium, hafnium, niobium, tantalum, tungsten and their
alloys, rather than a treatise on the analytical chemistry of these
metals, because such information is readily available elsewhere.[1_4]
However, to give the analyst a better appraisal of the principles and
limitations of the recommended methods, a more detailed introduc-
tion to the determination of each element has been included in this
present edition, and further information is contained in a selection
of supporting references.
For most determinations, more than one procedure is given, and
the uses and limitations of each are briefly described. This informa-
tion should be used as a guide in making a choice between a rapid
procedure and one that is intended to provide accurate information
without undue regard to the time involved.
Sections 1 and 2 deal with Sampling, Reagents and Abbreviations,
and all procedures subsequently described must be applied in strict
conjunction with this information. In this way, and because of the
close chemical similarity of these six metals, it has been possible to
present the relevant analytical information in what is hoped is a
simple, clear and unequivocal style without unnecessary duplication.
Research Department
Imperial Metal Industries {Kynoch) Ltd.
Witton
Birmingham 6
6 April 1965
ACKNOWLEDGEMENTS
The authors acknowledge the assistance given by J. A. F. Gidley,
R. T. Clark, A. G. Gofton and other members of the Analytical
Section of Research Department, Imperial Metal Industries (Kynoch)
Ltd., who have been associated with developing or proving the
procedures contained in this book.
Due acknowledgement is also made to Miss C. J. Underhill for
typing the manuscript and assisting in checking the proofs.
I. INTRODUCTION
1. SAMPLING
Special procedures are necessary to obtain representative samples
of titanium or zirconium sponge. Earlier difficulties in obtaining
representative samples of some grades of titanium have been largely
overcome as a result of improvements in quality and uniformity of
the raw product and the introduction of better melting techniques.
Some sampling precautions, however, are still necessary, depending
on the form of the material to be examined.
In all procedures, traces of oil, grease, moisture or other con-
taminant, and conditions likely to cause oxidation or nitriding, must
be avoided; this applies to all machining operations. A lubricant
must only be used when it is essential. Extraneous iron must be
removed from prepared samples by means of a magnet.
Because of the pyrophoric nature of finely divided titanium,
hafnium and, more particularly, zirconium, special care must be
taken to avoid excessive generation of heat in all machining opera-
tions ; niobium and tantalum are less pyrophoric than titanium.
Recommended methods of sampling are summarized as follows:
1.1. Titanium or Zirconium Sponge {Kroll Process)
The heterogeneous nature of Kroll sponge presents difficulties
which are best minimized by using the sampling procedure 1.1.1.
Where compacting facilities are not available, and where solution of
the sample is permissible, preparation of a master solution, as
described under 1.1.2, is recommended.
1.1.1. Compacting and Drilling
Riffle the consignment down to about 450 g and compact under pressure
of about 25 tons/in2 to a block about 2 in. square x 1 i in. Drill at least
nine evenly spaced i-in. holes through the entire block; this will provide
about 50 g of material.
l
2 ANALYSIS OF THE NEW METALS
Mix the drillings thoroughly, weigh, sieve (No. 44 mesh), and weigh the
separate fractions.
All samples for analysis must consist of coarse and fine drillings in
proportion to the weight of these two fractions. Samples for oxygen and
hydrogen determinations are re-compacted. Preparation of an evaluation
button, by arc melting about 100 g of the material, in a small vacuum
furnace, or in an atmosphere of high-purity argon, has the advantage of
providing a more homogeneous sample.
1.1.2. Preparation of Master Solution
Riffle the consignment down to about 450 g, then cone and quarter to
provide a final sample weight of about 10 g.
Dissolve this representative sample, under water reflux, in 750 ml of
sulphuric acid (1+4), cool, and dilute to 1 1.
Transfer appropriate aliquots for individual determinations.
1.2. Titanium Granules (ICI Sodium Process)
This material is usually sampled mechanically, but uniformity of
the granules makes sampling permissible by either riffling or coning
and quartering.
For individual determinations, a sample weight of about 1 g
normally provides sufficient granules to be representative of the
consignment.
1.3. Hafnium Crystal Bar
There is some evidence of segregation of impurities in this material.
To obtain a representative sample for analysis, an evaluation button
is prepared from chippings taken from the ends of the bars.
1.4. Ingots and Wrought Products
These materials are sampled by drilling or machining, after
removal of any surface oxide skin produced during heat treatment.
Samples in a finely divided condition are used when rapid solution
of the metal is required, but when oxygen or hydrogen is to be
determined, the sample should preferably be in a single piece. In the
determination of nitrogen, a sample in one piece is also preferred,
but where the metal is difficult to dissolve it may be expedient to use
a sample made up of several pieces.
INTRODUCTION 3
1.5. Notes on Machining and Drilling
General recommendations for machining and drilling samples
may be summarized as follows.
All metals and alloys referred to in this publication can be
machined successfully on conventional machine tools, provided that
certain essential requirements are satisfied. With tungsten, however,
tool-wear is excessive.
In all machining operations rigidity of both workpiece and cutting
tool is essential. The machine tool should be in good condition and
generally more robust than would be necessary for similar operations
with alloy steels.
All these materials, with the exceptson of tungsten, particularly
niobium and tantalum, have a tendency to gall or smear on to other
metals, and sliding contact between the workpiece and its support
should be avoided.
In general, cutting speeds should be low and feeds as coarse as
possible, in keeping with the strength and rigidity of the tool.
Tool materials may be of high-speed steel, cast alloy or tungsten
carbide. Few tungsten, tungsten carbide tools are used. High-speed
steel tools are preferred for unalloyed niobium and tantalum; for some
of their alloys the use of tungsten carbide tools may be necessary.
Top rakes for tungsten-carbide tools should be from 6° positive to
7° negative, depending on the severity of the operation. Cast-alloy
tools operate best with a 5° positive rake, and high-speed tools with a
positive rake up to 20°. A relief angle of about 7° is always advisable.
The table gives the range of speeds within which trial cuts should
be taken to establish optimum machining conditions for titanium-
and zirconium-base materials, and these will serve as a guide for the
machining of other materials.
These metals may be drilled with short high-speed steel drills; the
Cast Tungsten
H.S.S.
alloy carbide
MMaatteerriiaall
(ft/min)
IMI Titanium 115, 125, 130 \ 100-120 120-140 200-300
IMI Zirconium 10, 20, 30 )
IMI Titanium 150, 160, 230, 314C 60-80 80-100 150-200
IMI Titanium 314A, 317, 318A, 679 20-40 40-60 100-120
4 ANALYSIS OF THE NEW METALS
holes should be as shallow as possible. For small sizes, below J in.,
a 140° point is best, though for larger sizes, a 90° or a double-angle
point is better. If long holes of a depth greater than five diameters are
needed, it is helpful to retract the drill at intervals and clear the
swarf. A continuous feed of about 0-002-0-005 in. per rev for small
sizes, or 0005-0-009 in. per rev for larger sizes, should be maintained.
Sawing can be carried out at speeds 25-50 % less than those used
for sawing steel of comparable hardness. Where it is permissible to
use a lubricant in sawing operations, paraffin oil is recommended,
but steps must be taken to ensure its complete removal before the
specimen is analysed.
Whatever type of tool is used, it is essential to keep it sharp and to
replace it before appreciable wear occurs because, once started, tool
wear accelerates rapidly and the sample surface is contaminated.
All sample preparations must aim at minimizing evolution of heat;
the importance of light cuts, light feeds and/or slow speeds cannot
be over-emphasized.
Drilled or machined samples for analysis must have extraneous
iron removed magnetically and must be degreased, e.g., with tri-
chloroethylene, then pickled for a few minutes in dilute acid, washed
with water, then with acetone and finally dried. Cold hydrochloric
acid (1 +2) is suitable for pickling titanium samples, but for the other
metals hot hydrochloric acid (1 +1) is preferred.
2. GENERAL INFORMATION
In presenting the information contained in this publication, it is
assumed that the reader is fully conversant with the safety pre-
cautions pertaining to the handling of reagents, apparatus, etc.
On such matters as nomenclature and abbreviations, due cogni-
zance has been taken of the recommendations of the British Standards
Institution[5] and the Chemical Society[6].
The use of proprietary names has been kept to a minimum; these
include Anhydrone (anhydrous magnesium perchlorate) and
Carbosorb (a self-indicating soda-asbestos absorbent), but alterna-
tive brands may be equally satisfactory.
Most books dealing with gravimetric analysis contain information
on the care and attention necessary during the drying and ignition of
filter papers, and this information is not repeated here in detail. It is
emphasized, however, that filter papers, including the material
filtered off, must be well dried, and the paper charred at a con-