National Bureau of Standard; Library, N.W. Bldg OCT 1 9 1964

NBS MISC. PUBL. 260-2

Standard Reference Materials:

PREPARATION OF NBS

COPPER-BASE SPECTROCHEMICAL

STANDARDS
THE NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards is a principal focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. Its responsibilities include development and maintenance of the national stand- ards of measurement, and the provisions of means for making measurements consistent with those standards; determination of physical constants and properties of materials; development of methods

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listing of its four Institutes and their organizational units. Institute for Basic Standards. Electricity. Metrology. Heat. Radiation Physics. Mechanics. Applied Mathematics. Atomic Physics. Physical Chemistry. Laboratory Astrophysics.* Radio Standards Laboratory: Radio Standards Physics; Radio Standards Engineering.** Office of Standard Ref- erence Data. Institute for Materials Research. Analytical Chemistry. Polymers. Metallurgy. Inorganic Materials. Reactor Radiations. Cryogenics.** Office of Standard Reference Materials. Central Radio Propagation Laboratory.** Ionosphere Research and Propagation. Troposphere and Space Telecommunications. Radio Systems. Upper Atmosphere and Space Physics. Institute for Applied Technology. Textiles and Apparel Technology Center. Building Research.

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* NBS Group, Joint Institute for Laboratory Astrophysics at the University of Colorado.

'* Located at Boulder, Colorado.
UNITED STATES DEPARTMENT OF COMMERCE • Luther H. Hodges, Secretary NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director

Standard Reference Materials:

Preparation of NBS

Copper-Base Spectrochemical

Standards

Robert E. Michaelis, LeRoy L. Wyman, and Richard Flitsch

Institute for Materials Research

National Bureau of Standards Washington, D.C.

National Bureau of Standards Miscellaneous Publication 260-2

Issued October IS, 1964

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C., 20402 - Price 35 cents
Library of Congress Catalog Card Number: 64-60093
PREFACE

Within the framework of the NBS Institute for Materials

Research the area of standard reference materials is a broad

and important one, including the preparation, characterization

and distribution of a wide variety of materials in such diverse

fields as metallurgy , polymers and inorganic materials. In carrying out such a program there is much interaction with

representatives of industry and science, beginning with discussions as to which primary standard materials will do most

to advance technology, the furnishing of materials and fabrication of samples, and the characterization and certification

of the materials by cooperative efforts. The many groups

participating in a standards program are very interested in

detailed information on specific aspects of the program -- but to date there has been no publication outlet for such

written discussions.

To meet this need, NBS Miscellaneous Publication 260 has

been reserved for a series of papers in the general area of

"standard reference materials". This series will present the

results of studies and investigations undertaken within the

Institute for Materials Research with emphasis on the preparation and characterization of standard reference materials.

This sub ject -oriented series will provide a means for rapid

dissemination of this detailed information and we hope will

stimulate the use of standard reference materials in science

and industry.

iii
OTHER NBS PUBLICATIONS OF INTEREST

NBS Miscellaneous Publication 260-1, Preparation of NBS White

Cast Iron Spectrochemical Standards, June 1964. 30 cents. NBS Miscellaneous Publication 24l, Standard Materials Issued

by the National Bureau of Standards: A Descriptive List

with Prices, March 1962. 30 cents. Up-to-date supplementary insert sheets to Misc. Publ. 24l list new, renewal,

out of stock, and discontinued standards. This sheet is

available without charge directly from the National Bureau

of Standards, Washington, D.C., 202^4.

NBS Miscellaneous Publication 250, Calibration and Test

Services of the National Bureau of Standards, November 1963.

70 cents. Send orders with remittance to: Superintendent of Documents,

U. S. Government Printing Office, Washington, D.C., 20402.

Remittances from foreign countries should include an additional one-fourth of the purchase price for postage.

iv
CONTENTS

PAGE

1. INTRODUCTION 1

2. PRELIMINARY PLANNING 3

3. CONSIDERATION FOR PREPARATION 4

4. CHEMICAL COMPOSITIONS 5

5. CASTING 7

6. MELTING 8

7. PRELIMINARY ANALYSIS 15

8. HOMOGENEITY TESTING 15

9. PROCESSING 20

10. CHEMICAL ANALYSIS . . . . 22

11. PRECAUTIONS FOR APPLICATION 28

12. EXAMPLES OF ANALYTICAL CURVES 29

13. REFERENCES 36

LIST OF TABLES

TABLE No. PAGE

1. Planned Compositions of NBS Copper-Base

Spectrochemical Standards 6. 2. Materials Used in Melting NBS Copper-Base

Standards 10

3. Log of Melt for Cartridge Brass (600 lb)

Standard (NBS No. C1100) November l8 3 1959 . . 11

4. Provisional Certified Values for NBS CopperBase Spectrochemical Standards 24

v
LIST OF FIGURES

FIGURE No. PAGE

1. Tapping the molten metal from the furnace

into the ladle . 12

2. Pouring of test samples prior to pouring

the molten metal into the stoppered

pouring basin 13

3. Solidified casting on the water-cooled

copper plate after removal of pouring basin . 14

4. Sampling of disk for homogeneity testing ... 16

5. Typical etch pattern of the casting thickness. 17

6. Typical results of homogeneity testing .... 19

7. Analytical curve for zinc by x-ray analysis. . 31

8. Analytic?l curve for nickel by x-ray analysis.,

uncorrected 31

9. Analytical curve for nickel by x-ray analysis

corrected for background and zinc 32

10. Analytical curve for zinc by optical emission

analysis 32

11. Analytical curve for nickel by optical emission

analysis s uncorrected 3^

12. Analytical curve for nickel by optical emission

analysis, corrected for copper interference

on nickel line 3^-

vi
PREPARATION OF NBS COPPER- BASE

SPECTROCHEMICAL STANDARDS

Robert E. MIchaelis, LeRoy L. Wyman 3 and Richard Flitsch

Institute for Materials Research, National Bureau

of Standards, Washington, D.C.

A procedure has "been developed for the preparation

of copper alloys in both the chill-cast and wrought

forms, sufficiently uniform in composition and

microstructure for calibration and use as standard

samples in spectrochemical analysis. The method

involves casting the molten metal on a massive

water-cooled copper plate producing unidirectional

cooling. A large disk casting 27 in. in diameter

and about 4 in. high is obtained which is split

laterally into two pieces, the lower section providing standards in the chill-cast condition and

the upper section material for subsequent fabrication into standards for the wrought condition.

Details of the planning, preparation and testing

of the standards material for 21 compositions are given, and application of 'the samples in calibration for optical and x-ray spectrochemical analysis

is described.

1. INTRODUCTION

Spectrochemical analysis of alloys usually is complicated

by the fact that the component elements react to form intermediate phases, and these constituents represent different

energy relationships from each other. As a consequence, it

requires different amounts of energy input to excite a given

component atom, depending on how tightly it is bonded to itself or to other components in the various constituents of an alloy system. Because of this, the uniformity of the

microstructures of samples for spectrochemical standards is vitally important. Particularly is this true for the copperbase alloys such as the brasses and the bronzes.

1
The need for copper-base spectrochemical standards" has

existed for a considerable length of time. For example, a survey made in 1950 by ASTM Committee E-2 revealed that standards were required to cover more than 50 different types of

copper-base alloys. Of greater significance than numbers of

standards, however, was the realization that the effects of

disperse phases and physical characteristics on the spectral

excitation seriously complicated the spectroscopic analysis

for many of the copper alloys. To illustrate, it was known

that as the copper-rich end of an alloy system was approached,

a small change in composition could markedly affect the electrical properties and heat conductivity, and hence the volatility rates in spectral excitation. It was no wonder, then,

that chill-cast versus wrought samples frequently led to major

differences in the spectrochemical results. Moreover, differences often were observed depending on the size, shape, and

material of the molds used in obtaining chill-cast samples,

the type of heat treatment for wrought samples, and the sur- face preparation of both types of samples for spectrochemical

analysis

In 1955:5 a cooperative program was initiated between the

NBS and a Task Group of Subcommittee V, ASTM Committee E-2,

to plan for the preparation of a limited number of needed

copper-base standards.

The main purposes of this paper are to describe the . development of a satisfactory method for the preparation of

2
the copper-base standards and to evaluate the application of

this method to 21 prepared copper-base compositions for NBS

spectrochemical standards.

2. PRELIMINARY PLANNING

As a result of several initial meetings with the ASTM

Task Group , three main recommendations were adopted. (1)

Standard samples were to be prepared for seven principal

copper-base alloys: cartridge, free-cutting, naval., red, and

aluminum brasses, gilding metal, and commercial bronze. Close

liaison was maintained with the Copper and Copper Alloy

Spectrographic Committee of the Canadian Association for

Applied Spectroscopy to prevent duplication of efforts since

this group also was planning the preparation of standards.

(2) Three standards were to be provided for each alloy

consisting of a nominal, a high, and a low composition. Thus,

individual analytical curves could be established to eliminate

the effects of matrix composition for the seven alloys; but

equally significant, standards would be available for study

of these effects for application to other copper-base alloys.

(3) Finally, it was considered important to prepare both

chill-cast samples primarily for the producer and wrought

samples primarily for the consumer for each composition. By

so doing, the problems attributed to chill-cast versus wrought

samples or standards would not exist.

3
3. CONSIDERATION FOR PREPARATION

At the same time as consideration was being given at NBS to the preparation of the copper-base standards, studies were also being devoted to the preparation of a set of eight

white cast iron spectrochemical standards [1]. For both, it was noted that the preparation of spectrochemical standard

samples to be provided in the "as cast" condition presented

several difficulties not encountered in those which could be

provided in the wrought condition. Further complicating

the preparation of the copper-base standards was the

necessity of providing both chill-cast and wrought samples.

Since it is next to impossible to obtain complete homogeneity from conventional castings or ingots of any size from

melts having complex compositions , it was evident that advantage must be taken of the generally accepted method to minimize segregation, namely , to solidify the molten metal as rapidly as possible. For the cast iron standards, it was believed that a scheme of rapid unidirectional solidification

from the melt would provide samples of suitable homogeneity

which would be useful both in optical emission and in x-ray

spectrochemical analysis. Although differing in details from

the cast iron, another scheme utilizing rapid unidirectional

solidification was considered for the preparation of the

copper-base material by which, and on further processing, it was believed that both chill-cast and wrought samples could be

obtained from the same casting.
The main advantage of rapid unidirectional solidification

over other types for the preparation of spectrochemical standards is not that it eliminates segregation., but that it does

force the segregation to occur largely at the top of the

casting where it may either be removed or where it at least

does not interfere with optical emission or x-ray spectrochemical analysis.

4. CHEMICAL COMPOSITIONS

As indicated previously modern metallurgy is

concerned not only with those elements that may be considered

the main components of an alloy,, but also with the effects of

minute amounts of other elements. For the copper-base standards s it was deemed essential to provide suitable standards

containing all of the trace elements of interest; however., it was not believed necessary to provide a graded and certified

series for each of the seven alloys.

In 1955 the NBS., in cooperation with the copper industry.,

planned the chemical compositions for three standards each

of seven copper-base alloys. The final compositions adopted

by NBS and accepted by industry are shown in table 1. As can be seen., each alloy is covered by a nominal,, high 5 and

low composition standard. All of the elements covered by the

then present and proposed chemical specifications were included for each alloy type; additionally., all of the trace

elements of interest were purposely included only in the

cartridge brass series.

5
Table 1. Planned Compositions of NBS Copper-Base Spectrochemical Standards

Designation Code

Cartridge Brass Spec. 67.0 70.0

73.0

0.10

0.05 0.02 Free-Cutting Brass Spec. 60.0-63.0 2.5-3.7

0.10 0.04

0.01

29^84

(26. 9*0 Remainder

Other and Ren

below) below

)

below)

59.0

61.5

64.0 4.0

3.0

2.0

0.30

0.10 0.05

(35.75) 34.93

33.72

0.15 0.07

0.03 Naval Brass 59-0-62.0" 0.20 max. Sn 0.5-1.0 Total Other 0.10 58.7

61.0

65.0

0.03

0.15 0.06

0.02

0.07

(40.40) 37.40) 34.37

0.75

1.2 0.42

0.06 0.02 0.10 0.08

0.03 0.03

0.02 0.01 Red Brass (85-15) Spec. 82.0

84.5 87.0

0.07 0.03 0.010.07

0.03

0.01

(17.66) 15.34

(12.94)

Total Other 0.15 max. Sn Ni 0.10 0.10

0.05 0.05 0.02 0.02 94.0-96.0 0.05 max. Total Other 0.15 max.

93.5 95.0

96.5

0.07 0.03

0.01

0.07

0.03

0.01

6.16) 4.84

3.44

0.10

0.05 0.02 Total Other 0.13 max. 0.01 0.03

0.07

0.07 0.03

0.01

11.72) 9.34 6.88

0.10 0.10

0.05 0.05 0.02 0.02 Aluminum Brass 76.0-79.0 0.07 max. 0.06 max. Remainder Al 1.8-2.5 As, Sb, or P 0.02-.10

75.0

77.5

80.0

0.02

0.05

0.10

0.07 0.03

0.10

(21.97) 20.14)

18.14) 0.01 0.01

0.06 0.06

0.12 0.12

Total Other Impurities 0.15 Max. ^^NiSbAsMn SiBi Te Al Be I £d Ag, 0.05 0.05 0.02 0.02 0.02 0.01 0.0008 0.005 0.008 0.002 0.008 0.015 0.020

0.015 0.015 0.01 0.01 0.01 0.005 0.0001 0.002 0.003 0.001 0.003 0.003 0 009 0.005 0.005 0.005 0.005 0.0035 0.002 0.0003 0.001 0.0003 0.00015 0.001 0.005 0.004

£ Pb may be 0.30 max. for some specifications.

Fe may be 0.10 max. for some specifications.

° Fe allowed to 0.35 max. for one specification.

d Cu allowed to 65$ for some specifications.

6
5. CASTING

The massive water-cooled copper-mold assembly that was designed and constructed at NBS for the unidirectional

casting of the copper-base alloy standards. This mold

assembly has been described in detail elsewhere [1], but

essentially it consists of a plate, 64 in. sq. by 1 in.

thick, made of OPHC copper (oxygen free-high conductivity)

and which is water cooled on the Dottom side. To accomplish the casting of the copper-base alloys, it was reasoned that if a sufficiently thick disk could be cast

and solidified in but a few minutes, then a minimum of

heterogeneity would result. Moreover, the chill-cast face

of the disk could serve to provide the as-cast samples, while

a portion of the remaining thickness of the disk could be

fabricated into bar stock 1 1/4 in. in diameter and sliced

to form the wrought samples.

The thickness of the disk would need to be about 3 1/2

or 4 in. to allow for (1) a smoothing cut on the chill-cast

face, (2) parting cuts, (3) finished sample thickness of

5/4 in. for the as-cast samples from the bottom layer and

(4) adequate thickness of the top layer both to permit

rejection of the objectionable top surface of the casting and

to provide sufficient material for working into round bars

1 1/4 in. in diameter.

With the thickness of the casting limited by the above

requirements, the diameter of the disk would be established

7
by the number of samples desired. Inasmuch as this might

vary, it was decided to define the periphery of the disk by

means of iron castings , slightly arched, and having a tongue

at one end and a groove at the other to permit interlocking;

the size of the annulus being defined by the number of blocks

in the circle. A disk size of 27 in. in diameter finally was

adopted.

To minimize the peripheral chilling of the casting by the

iron blocks and thus to obtain the maximum unidirectional chill

from the plate, an inner wall, 5 in. thick, of baked-sand

forms was assembled within the cast iron ring, and their

joints sealed.

In pouring the casting, several schemes were investigated

which included lip-and bottom-pouring from ladles, and rapid

dumping of the melt. The criterion here was to permit complete

coverage of the disk area in the minimum of time but with

neither cold shuts nor splatters. This study resulted in the

adoption of a tun dish ( pouring basin) having six stoppered

orifices into which the entire melt was poured, and from which

all metal was run onto the casting plate by simultaneously

releasing the six stoppers.

6. MELTING

Following extensive investigations in the NBS foundry

during 1957 and 1958, which included the preparation of one cartridge brass and one naval brass standard, techniques of

melting, casting, and fabrication were established for

8
producing suitable chill-cast and wrought samples from a single casting.

Experimental melting at NBS was carried out in a highfrequency induction furnace of 1,000-Tb rated capacity;

however , all production heats with the exception of the one cartridge and one naval brass were made at the Naval Research

Laboratory* in a similar type of furnace also of 1,000-lb

rated capacity.

High-purity metals were used either directly or in the

preparation of master alloys , and these are shown in table 2. The copper was OFHG grade. the zinc was five nines pure

and added as a prepared and analyzed 50 copper-50 zinc

alloy.

Heats of approximately 600 lb were melted under a charcoal cover. Careful control was maintained over the

melting procedures to include time, temperature, and amount

and order of additions to the furnace. Table 3 shows as an example the melt log for a cartridge brass standard (Code

Al in table l). For this standard it is noted that the iron,

nickel, and manganese additions were made with the initial

furnace charge. On subsequent melts, these additions were combined, melted separately in a small gas-fired furnace, and

added in the molten condition to the main melt at the same T

The authors express their appreciation to L. DePue and the

foundry staff at the Naval Research Laboratory for permitting

the use of their facilities and personnel in the production

of the 19 remaining copper-base spectrochemical standards.
Table 2. Materials Used in Melting NBS

Copper-Base Standards

Element Material Description Purity8,

Cu OFHC, rod ends 99. 9+

Pb Metal, shot 99 + Fe

b CuFe, small ingot (50$ Fe

)

99 + Zn

b CuZn, ingot 99. 9+

Sn Metal , small ingot 99. 9 Nib CuNi, small ingot (50$ Ni) 99 +

Sb Metal, lump 99 + As Metal, lump 99 + Mn CuMn, small ingot (35$ Mn) 99

Sib CuSi, broken ingot (10$ Si) 99

Bi Metal, lump 99..5+ Te

b CuTe, lump (45.5$ Te) 99 + Al Metal, small ingot 99.S

Beb CuBe, broken ingot (13.4$ Be) 99 +

Pb CuP, lump (10$ P) 99 +

Cdb CuCd, broken ingot (50$ Cd) 99. 9 Ag Metal, chips 99..9+

Semiquantitative spectrochemical analyses were obtained on all materials to assure positive identification and to determine the approximate concentrations of the impurities that

could affect the schedule for additions.

b A master alloy was prepared for the addition of this element.

10
Table 3. Log of Melt for a Cartridge Brass

(600 lb) Standard (NBS No. C1100) November lQ, 1959

Charge

Furnace On

Melt Down

Skim

Additions

Stir

Tap

Skim

Mold Water on Pour

Basin Plugs Pulled

Pouring Basin Empty

Casting Solidified

OFHC Cu (199.6 lb), 50 Cu-50 Zn (399.6 lb)

s 50 Cu-50 Fe ( 1.2 lb), 50 Cu-50 Ni

(0.6 lb),

65 Cu-35 Mn (0.343 lb), charcoal

cover

11:05 A.M. Time 11: 58 A.M., Temp. l800°F

Most of charcoal removed. Time

11:42 A.M.

(All were encased individually in

copper foil)

Pb (272.2 g), Sn (136.1 g), Sb

(54.4 g), As (54.4 g), CuMn (155.6 g), CuSi (272.2 g), Bi (2.18 g), CuTe

(29.9 g), Al (21.8 g), CuBe (40.4 g),

CuP (155.1 g), CuCd (81.6 g), Ag

(54.4 g).

Time 11:47 A.M., Temp. l875°F.

Stir in ladle. Time 11:51 A.M.,

Temp. 1950 F, Time 11:53 A.M. Time 11:54 A.M. Time 11:54 A.M., Temp. 1920 F. Poured

three test samples into ceramic molds

on plate edge; followed by pouring

entire melt into stoppered basin.

Time: 11:56'20" A.M. Time: 11:56 '35" A.M. Time: 11:58'00" A.M.

11
time as the other additions. This was done to assure complete

melting of these higher melting point additives.

For this cartridge brass standard, it can be seen that

a total of 1 min 25 sec time had elapsed from pulling the

stoppers in the pouring basin to complete solidification for

the 600 lb disk 27 in. in diameter and 4 in. thick. The

total time varied from about 40 sec to 2 min for the various

melts and was dependent primarily on the alloy, but also to

a lesser degree on the particular composition for a given

alloy.

Figure 1 shows the tapping of the molten metal from the

Figure 1. Tapping the molten metal from the furnace

into the ladle.

12
furnace into the ladle. This was done approximately 100°

F

above the liquidus temperature for each melt. Once in the

ladle j the molten metal was skimmed to remove the last of the

charcoal cover and the dross.

Figure 2 shows the pouring of test samples into separate

ceramic molds on the water-cooled copper plate prior to pouring

the main heat. In the background is seen the mold assembly

into which the molten metal is poured. Note the stoppered

pouring basin at the top. Once the molten metal has been

poured into the basin., the plugs are pulled simultaneously.

Figure 2. Pouring of test samples prior to pouring the

molten metal into the stoppered pouring basin.

13
Solidification is unidirectional, from the bottom up, with

little freezing occurring from the periphery inward, or from

the top downward.

Figure 3 shows a view of the solidified casting. Note

the use of the interlocking cast iron blocks to retain the

circular disk casting.

Figure 3. Solidified casting on the water-cooled copper

plate after removal of pouring basin.

14
7. PRELIMINARY ANALYSIS

Once a casting had been prepared, preliminary analyses

were obtained on the separately cast test samples both at NBS

and by a cooperator* . At NBS, both chemical** and spectrochemical determinations were made and a complete analysis for

each heat was obtained before preparing a subsequent heat.

In general, it was relatively easy to prepare the copper-base

castings close to the aim or the desired composition.

8. HOMOGENEITY TESTING

Before processing a casting into standard samples, extensive homogeneity testing was performed and figure 4 shows the

selection of samples that were chosen for this testing. Metallographic studies, optical and x-ray analyses, and chemical

analyses were made at NBS. In addition, a large amount of

testing was performed by members of the cooperating Task Group

3, Subcommittee V of ASTM Committee E-2***. These studies provided information on the composition and structure differences

from outside to center and from bottom to top of the casting.

* F. V. Schatz, Revere Copper and Brass, Inc., Rome, N. Y. ** R. K. Bell, Quantitative Separations Section (formerly

Standard Reference Materials Section).

Task Group 3 cooperators:

Bridgeport Brass Co., Bridgeport, Conn., A. W. Young

Chase Brass and Copper Co., Waterbury, Conn., H. J. Smith

Mueller Brass Co., Port Huron, Mich., S. C. Richards

Olin Mathieson Chemical Corp., New Haven, Conn., R. G. Russell

Revere Copper and Brass, Inc., Rome, N. Y.

,

F. V. Schatz (Chairman)

The Anaconda American Brass Co., Waterbury, Conn., J. P. Irwin

Titan Metal Mfg. Co., Beliefonte, Pa., W. M. Rumberger

15
27"

SAMPLES FOR M ETALLOG R APH I C TESTING Figure 4. Sampling of disk for homogeneity testing.

Differences in structure were observed by etch tests and

metallographic examinations. Figure 5 shows a typical etch

pattern through the casting thickness. Extending from the

chill-cast surface upward to about half the thickness is the

columnar structure indicative of a rapid solidification.

Above this are the more randomly oriented large grains of the

dendritic structure typical of a slower cooling rate of the

molten metal. Finally , near the top, is seen another break in

structure where the solidification from the bottom met that

coming down from the top. The main purpose of obtaining etch

patterns for each casting was to determine that the columnar

structure extended upward sufficiently to provide for the

16
Figure 5. Typical etch pattern of the casting thickness.

chill-cast samples. Although a minimum height of only 7/8 in. was required, all castings were observed to exhibit this

structure to a height of at least 1 1/4 inches. Except for

the chill-cast samples, the structure initially was believed

to be relatively unimportant, particularly since it would be

changed completely during forging. However, on preliminary

forging trials considerable radial cracking occurred, and this was attributed to sub-surface porosity that appeared at the

interface of solidification from the bottom and top of the

casting. Thus, the etch pattern also served to determine the

amount of material that had to be removed from the casting top

to prevent cracking on subsequent forging.

Although homogeneity studies did demonstrate some non- uniformity of composition near the casting top, the entire

17
casting thickness generally was found to be considerably better

than was anticipated. When the material at the top containing

the sub-surface porosity was removed, the remaining material

for most castings was found to be of high homogeneity. Typical

results of a homogeneity study are shown in figure 6. The

test positions on a section of the casting thickness are indicated on the sketch; three such sections from center to outside of the casting were examined. The test level indicated

at the bottom is the standard deviation of the reported average,

which is obtained by dividing the calculated standard deviation

by the square root of the number of values on which the average

is based. In general, differences among positions exceeding

the test level values are statistically significant at the

5 percent level. Iron shows no difference from bottom to top

at the test level of four parts per million.

Lead shows a statistically significant trend of increasing

content from top to bottom but this was deemed to have little

practical significance. Position 4 differs from positions 1,

2 and 3 for both nickel and zinc. Even including position 4,

the variation for nickel is acceptable. For zinc, however,

cutting the top portion to discard does considerably reduce

the variation. Practical significance of inhomogeneity is

adjudged on the basis of (1) method precision, (2) number of

replications in testing, (3) the concentration of the element

under test and (4) the accuracy of the certification which

may itself, in some instances, be limited by the homogeneity.
TYPICAL RESULTS OF HOMOGENEITY TESTING

NBS NO. IIIO NBS NO. 1 109

FOR CHILLCAST SAMPLES

POSTION ZINC IRON LEAD NICKEL

BOTTOM

TEST LEVEL 0.06

0.029

8

0.030,

0.030

0

0.030,

0.0004

0.099,

0.100.

0.073

9 0.074

2

0.075 2 O.I00 0

0.075

6 0.100,

O.OOU 0.0003 Figure 6. Typical results of homogeneity testing.

An example of the latter situation exists for lead nominal)

in free-cutting brass. Here the lead is added to impart high

machineability . Since the solubility of lead in brass is nil,,

the lead appears as small soft particles dispersed throughout

the brass matrix. Although not necessarily a factor in the

end use of the material, certain variations do occur in the

particle size and in the distribution of the lead. With lead,

then, the inherent heterogeneity limits the accuracy of the

certification. Whereas ± 1 percent of the amount present is

normally acceptable from the practical significance standpoint,

with lead in free-cutting brass ± 5 percent of the amount

present is deemed acceptable, but this in turn, limits the

19
accuracy of certification by reporting values only to the

nearest 0.1 percent.

In general^ the homogeneity of the copper-base alloy

material was found to be sufficiently good so that a single

set of results served for both the chill-cast and the wrought

samples. For the nominal composition lot of the cartridge

brass, however, a practically significant difference was observed between the chill-cast and wrought material

necessitating separate certification.

9. PROCESSING

Following acceptance of the homogeneity of the material,

the castings were fabricated to finished chill cast and

wrought samples. Essentially, about 1/8 in. was removed from

the chill-cast face of the casting, in. from the top, and

1/2 in. at the periphery. The remaining slab then was cut into strips, the bottom portion of which was further cut to provide the chill-cast samples; and the top portion of which

was forged to rods and annealed for the wrought samples. In forging, the material was soaked in a furnace at the

appropriate temperature and then it was worked thoroughly to provide a uniformly recrystallized structure. The proper

annealing temperature was determined by metallographic examination and by hardness measurements of samples annealed at 100°F

intervals. Intercomparisons were made for each of the three

standards for a particular alloy, and with the other alloys as well, to insure the maximum compatibility of the standards.

20
Because of extreme difficulties encountered in forging

some compositions, wrought standard samples will not be available initially for a few standards. For example , the high

impurity level standard of both cartridge brass, NBS No. 1100,

and red brass, NBS No. 1109, would not permit forging without

severe cracking. Additionally, the low lead composition

standard (2$ nominal) of the free-cutting brass series,

NBS No. 1105, and all three of the aluminum brass series,

NBS Nos. 1118-1120, also would not forge.

Although the standards described above would not forge,

it was believed that an extrusion process could be utilized to produce the wrought samples. In late 196l, test lots of the

red brass, NBS No. 1109, and the free-cutting brass, NBS No. 1105, were sent to Nuclear Metals, Inc. for extrusion by a procedure agreed upon by both NBS and NMI. Subsequent testing

of selected extruded samples indicated that the material

should be satisfactory for the wrought samples although some cracking and some nonuniformity of metallurgical structure

was in evidence.

Based on the above investigation, the remaining material

of all the standards that would not forge (with the exception

of the one for cartridge brass which broke up completely on forging and could not be extruded) were sent to NMI for extrusion. Some of the pertinent details of the procedure follow:

(a) the NBS copper-base material was cut into convenient

size pieces for close packing in copper extrusion cans (about

21
6-in. diameter); (b) each cut piece was given a light etch

(< 5 seconds) in dilute nitric acid before packing in the

cans; (c) the cans were evacuated to 0.0^>\i pressure at room temperature and sealed; (d) the extrusion temperature was

1550°F, the ram speed 40 in./min, and the extrusion force

from about 700-950 tons; (e) the final extruded size was

1 1/2 in. in diameter.

As with the test lots,, some cracking and nonuniformity

of metallurgical structure was evident on testing the returned material. Although all the testing has not been completed

at this writing, it is believed that the material will be useful as wrought standard samples. A separate report covering

the testing of the extruded material has been planned.

10. CHEMICAL ANALYSIS

Samples for cooperative chemical analysis were prepared

in the form of millings taken from the cross section of the

finished samples of both the chill-cast and wrought material.

Chemical analyses were made at NBS for all standards and in

six cooperating laboratories, one of which also analyzed all

standards .

* Quantitative Separations Section (formerly Standard

Reference Materials Section), National Bureau of Standards,

Washington, D.C. (R. K. Bell and E. E. Maczkowske). Analyzed

all standards.

Department of Mines and Technical Surveys, Mines Branch,

Ottawa, Ontario, Canada (A. E. LaRochelle, Elsie M. Penner,

C. H. McMaster, and W. R. Inman). Analyzed all standards.

22
Provisional Certificates of Analyses were prepared for

naval brass in March,, 1961 (revised in August 1962); for

cartridge and red brass in August 1962; and for free-cutting

brass, gilding metal, commercial bronze, and aluminum brass

in February, 1964. The certified values are shown in table

4**. It is to be noted that additional elements having

useful concentration ranges are contained in the cartridge

brass series to include Al, Sb, As, Be, Bi, Cd, Ag, and Te.

"^(Footnote con't from preceding page)

Anaconda American Brass Co., Waterbury, Conn. (0. P. Case

and Mrs. Kathleen M. O'Brien). Analyzed cartridge, naval,

and red brass.

Anaconda American Brass Co., Metallurgical Dept., Research

and Technical Center, Waterbury, Conn. (Joseph P. Irwin).

Analyzed commercial bronze and aluminum brass.

Revere Copper and Brass, Inc., Rome, N.Y. , (Frederick V. Schatz and R. E. Hahn) . Analyzed free-cutting brass, gilding metal, commercial bronze and aluminum brass.

Mueller Brass Co., Port Huron, Mich. (S. C. Richards, Ray

Stevens and Albert Stuever). Analyzed cartridge, naval,

and red brass.

Twin City Testing and Engineering Laboratory, Inc., St. Paul,

Minn. (Albert C. Holler ). Analyzed free-cutting brass.

Ledoux and Co., Teaneck, N. J. (Silve Kallmann). Analyzed

gilding metal.

A brief summary of the chemical methods used in the analysis

of the copper-base alloys is available on request to the

Analytical Chemistry Division, National Bureau of Standards,

Washington, D.C.

Additionally, a paper Is being prepared describing the

factors involved in the basic standardization of the x-ray

spectrochemical method as applied to the certification of

the copper-base alloys. This paper will appear shortly in

this publication series.

23
Table 4. Provisional Certified Values for NBS

Copper-Base Spectrochemical Standards

(May 1964)

Cartridge Brass

TiTTD C T\T/-s ^

iNJDO 1NO . b CllOO

1101

c c C1101

1102

C1102

Element*^ Percent

Cu 67. 4^ 69.

Q 69.

n0 72. 8^ Zn 52. 2 Q 30.

6 30.

4

27.

0 Pb 0.106 0.05 0.05 0.020

Fe .072 .037 .037 .011

Sn .055 ' .016 .016 .006

Ni .052 .013 .013 .005

Mn ( .003) e

( .006) ( .006) ( .004)

P .01 ( .002) ( .002) ( .006)

Si ( .01 ) ( .005) ( .005) ( .002)

Free-Cutting Brass

NBS No.

a 1103 f no4 b CH03 cno4 C1105

Element2 Percent

Cu 59.

? 59.

9 61.

3 63.

2 Zn 35.7 35.7 35.3 34.0

Pb 3.7^ 3.8, 2 ' 7

6 2.0,

Sn 0.88 0.88 0.43 0.21

Fe .26 .26 .090 .04^

Ni .16 .16 .071 .043

P .003 .003 .005 .003

24
Table 4. (Continued

)

Naval Brass

NBS No.

a 1106

C1106

1107

C1107

n -7 r\ O llOo

C1108

Element Percent

Cu

Zn

59. On

O 40. Oq

61.2

37.

4

64.

5 34.

2 PbFeSn

Ni

Al

Mn

0.032

.004

.74

.025

h

.005

0.18

.037

i.o4

0.098

O.063

.050

.39

.033

.025

Red Brass

NBS No.

a b

C1109

1110

C1110

nil

Cllll

Element Percent

Cu 82. 2

2 87. i4 Zn 17.

5

15.

Q

12.

1 PbFeSn

Ni

P

0.075

.053

.10

.10

0.033

.033

.051

.053

0.013

.010

.019

.022

Gilding Metal

a NBS No. 1112

CH12

1113

C1113

1114

Clll4

Element 1 Percent

Cu

ZnSn

93.

8 6.30 0.12

95. 0^

4.8

Q

0.06^

96.

5 3.4

? 0.02

7 .021

.01

.012

.009

Ni

FePb

P

• 10

o .070 .057

.009

.057

.04

.026

.008

25
Table 4. (Continued)

Commercial Bronze

a 1115 1116 1117

NBS No. C1115 C1116 C1117

Element^ Percent

Cu 87.

6 90. 3 7 93.

1 Zn 11.7. 9-\ 6.87 Fe 0.13 0.046 0.014

on • U4i| 02no

1 Ni .074 .048 .020

Pb .013 .042 .O69

P .005 .008 .002

Aluminum Brass

a b b b NBS No. C1118 C1119 C1120

Element k Percent

Cu 75.

? 77.

2 80. i4

Zn 21.

X 20. 5 3 18. lo

Al 2.80 2.14 1.46

Fe 0.06g 0.0^ 0.01.

0 Pb . .024 .051 .105

P • 12

5 .070 .018

10ns: 1100 series are wrought

3/4 in. thick. C1100 series

in. square, 3/4 in. thick.

The wrought material for this standard is not available.

Size and metallurgical condit:

samples 1 1/4 in. in diameter

are chill-cast samples 1 1/4

Small differences in the copp

necessary the separate analys

cast material for this standa

Other purposely added element

ranges in the cartridge brass

antimony, arsenic, beryllium,

tellurium. Some of these are

a later date.

er and zinc contents made

is of the wrought and chillrd.

s having useful concentration

standards include: aluminum,

bismuth, cadmium, silver, and

expected to be certified at

26
Q Values in parentheses are not certified, "but are given

for information on the composition.

f Small differences in the copper and lead contents made

necessary the separate analysis of the wrought and chillcast material for this standard.

g Bi and Ag also are present in small quantities in the

standards, but these elements have not been certified.

^ Dashes indicate elements present but not certified.

1 Al, Mn, Ag, and Si also are present in small quantities

in the standards , but these elements have not been

certified

.

^ Ag, Si , and Mn also are present in small quantities in

the standards, but these elements have not been certified.

Ag, As, Sb, and Si also are present in small quantities

in the standards, but these elements have not been

certified

.

27
Work currently is underway to certify these elements; also,

to provide final certificates for all the copper-base standards

wherein the cooperative results will be listed. Completion

of the work on the copper-base standards is planned for the

fall of this year.

11. PRECAUTIONS FOR APPLICATION

Several precautions are important in the application of

these standards to spectrochemical analysis. For the chillcast samples , the NBS number has been stamped on the surface

opposite the chill-cast face. For use in calibration by

either optical emission or x-ray techniques s analyses always

should be made on the chill-cast surface (opposite that which

is numbered)

The determination of lead in the free-cutting brass series

by x-ray spectrochemical techniques presents the same problem

as lead In leaded steel and is highly dependent on proper

surface preparation because of the tendency toward smearing

or removal of the lead [2]. It may be found necessary to utilize a metallographic polishing technique to minimize the

effects of changes in particle size of an undissolved

constituent or in the metallurgical structure size [3>]. For use by optical emission techniques , the NBS chillcast samples are designed for the analysis of samples prepared

in a similar manner. It should be cautioned that samples

for analysis prepared by casting techniques other than that

28
of unidirectional solif ica.tion may produce a bias in the

spectrochemical results, the magnitude of which will depend

on the excitation parameters.

For wrought material, care should be taken to insure that

spectrochemical results obtained on samples relative to the

NBS wrought standards are not biased because of differing

fabrication techniques or heat treatment.

When the copper content of an alloy is high, 90 percent or more, the heat conductivity, and hence the volatility rate in

optical emission analysis, is sensitive to relatively small

changes in composition, particularly of copper. At the high

copper levels, the heat conductivity also is sensitive to the mass of the samples; therefore, it may be found necessary

not only to match samples and standards in terms of size and

shape, but also with respect to the positioning of the electrical discharge on the samples. These illustrations serve to emphasize the fact that in order to obtain reliable spectrochemical results, it is imperative to match closely in all

aspects the standards and the samples for analysis. Any

deviation from this axiom should be investigated thoroughly

to insure that a bias has not been introduced.

12. EXAMPLES OF ANALYTICAL CURVES

It is felt desirable to show some examples of analytical

curves that can be developed by means of the NBS copper-base

standards both by x-ray and by optical emission techniques.

These will serve to point to some additional problems that may

29
be encountered in applications. The analytical curves cover only the first three sets of standards originally made

available; viz. 3 cartridge, naval, and the red brass series.

Figure 7 shows the analytical curve for zinc by x-ray

analysis. As might be expected., no significant differences

between chill-cast and wrought samples are evident. Although

some workers have indicated a nickel correction is necessary

for the x-ray determination of zinc., certainly one is not

required here where the nickel concentration of the standards

is 0.1 percent or less.

The situation depicted in figure 8 for nickel by x-ray

determinations is not uncommon; that is, where it is not

possible initially to draw a single analytical curve through

all the points. A reason must exist. The problem for nickel

was resolved when a linear correction for a zinc interelement

effect was made, along with a background correction, as shown in figure 9. A reasonable fit of the analytical points

for nickel now is evident. The enhancement of nickel by

zinc, two mass number higher in the periodic table, is of course predictable. The exact effect over wide concentration

ranges of zinc may not be linear and would be more difficult

to calculate. However, when the effect is not large and when

relatively limited concentration ranges are involved, a linear correction normally is sufficient.

It will be of interest to compare the analytical curves

of the same elements by optical emission analysis. Figure 10

30
60 1

1 1 1 1 1 1 1 1 r

I i

i i 0 20 40 60 80 100 CHART READING Figure 7. Analytical curve for zinc by x-ray analysis

(abscissa is arbitrary units).

I4

I ! I I

1 1 1 1 1 j—

•12 L o WROUGHT

0.2 0.4 0.6 0.8 1.0 DIGITAL VOLTMETER RESPONSE , v

Figure 8. Analytical curve for nickel } by x-ray

analysis, uncorrected.

31
.12

DIGITAL VOLTMETER RESPONSE, v

Figure 9. Analytical curve for nickel, by x-ray

analysis s corrected for background and zinc.

r~—i

1 1 1 1 1 1 1 1

3.0 5.0 7.0 9.0 11.0 13.0 DIGITAL VOLTMETER RESP0NSE.V Figure 10. Analytical curve for zinc by optical

emission analysis.

32
illustrates the analytical curve for zinc. Note that by

optical emission analysis the ordinate or vertical scale now

is in terms of concentration ratio rather than concentration;

that is, the zinc content divided by the copper content times

100. This is necessary to correct the intensity of the copper

internal standard line for the rather large change in copper

content; from about 59 to 87 percent of copper with these

standards. Note also that only the chill-cast samples have

been plotted. Contrary to expectation, no significant

differences have been observed between the chill-cast and the

wrought samples for these three alloys. The excitation was provided by a low-voltage triggered spark discharge which

was half-wave rectified and adjusted to be critically damped.

Other sources or changes in parameters for this source may

exhibit differences but these have not yet been investigated.

This curve for zinc is perhaps not as good as shown previously

by x-ray, but certainly it is acceptable.

Figure 11 shows an analytical curve by an optical emission

spectrometer analysis relating the ratio of the Ni J>klk.QA

o line in the second order over the Cu 3108.1A internal standard

line in the first order to the concentration ratio.

Similar to the uncorrected x-ray curve, it is not

possible to draw a single analytical curve through all the

points. The problem here is not an interement effect, but

an interference that is caused by the third order of the

o copper line, 2275. 2A passing through the same slit as the

33

1
.24

.20

Ni 3414.8 CONCENTRATION RATIO, CU3I08 I (Ni%/Cu%XIOO)

CARTRIDGE AND

2 " NAVAL BRASS

.08

.0 4

0

C 1 1 07

h ciioi

CI 102

3.0 4.0 5.0 6.0 7.0

DIGITAL VOLTMETER RESPONSE^

Figure 11. Analytical curve for nickel by optical

emission analysis^ uncorrected.

.24

20 . CORRECTED FOR Cu INTERFERENCE ON Ni LINE

.16- C0NCENTRATI0N RATIO

(Ni %/ Cu %X 100)

CII07r

3.0 4.0 5.0 6.0 7.0

DIGITAL VOLTMETER RESPONSE, V (CORRECTED TO 50% Cu) Figure 12. Analytical curve for nickel by optical

emission analysis., corrected for copper

interference on nickel line.

34
second order of the Ni 3>4l4. 8A line. When an appropriate

correction is made, a reasonably good curve may be drawn

as indicated in figure 12. A better solution to this particular problem obviously

would be to choose another nickel line which would be free

from interference. With spectrometers , however, one line of

an element may need to serve for several matrices and

corrections may be required. In general, good analytical

curves for the certified elements were obtained by both

x-ray and optical emission analysis.

35
13 . REFERENCES

Michaelis, R. E. and Wyman, L. L. s NBS Misc. Publ.

260-1, 1964.

Kilday, Betty Ann^ and Michaelis, R. E., Applied

Spectroscopy, Vol. 16, No. 4, 1962.

Michaelis, R. E., and Kilday, Betty Ann, Advances

in X-Ray Analysis s Vol. 3, ^05. Edited by W. M. Mueller,

Plenum Press, 1962.

36

GOVERNMENT PRINTING OFFICE : 1964 O —741-607
Announcement of New Publications on Standard Reference Materials

Superintendent of Documents

Government Printing Office Washington, D. C. 20402

Dear Sir: Please add my name to the announcement list of new

publications to be issued in the series: NBS Miscellaneous

Publication 260 - Standard Reference Materials.

Name

Company

Address

City State Zip Code

(Notification key N-330)