i National Bureau of Standards

Library, N.W. Bldg SEP 3 0 1966

NBS MISC. PUBL. 260-14

Standard Reference Materials:

DETERMINATION OF OXYGEN

IN FERROUS MATERIALS

SRM 1090, 1091, AND 1092

U.S. Department of Commerce

National Bureau of Standards
THE NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 provides measurement and technical information services

essential to the efficiency and effectiveness of the work of the Nation's scientists and engineers. The

Bureau serves also as a 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. To

accomplish this mission, the Bureau is organized into three institutes covering broad program areas of research and services: THE INSTITUTE FOR BASIC STANDARDS . . . provides the central basis within the United

States for a complete and consistent system of physical measurements, coordinates that system with the measurement systems of other nations, and furnishes essential services leading to accurate and uniform

physical measurements throughout the Nation's scientific community, industry, and commerce. This

Institute comprises a series of divisions, each serving a classical subject matter area: —Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic Physics—Physical Chemistry—Radiation Physics—Laboratory Astrophysics2—Radio Standards Laboratory,2 which

includes Radio Standards Physics and Radio Standards Engineering—Office of Standard Refer- ence Data. THE INSTITUTE FOR MATERIALS RESEARCH . . . conducts materials research and provides

associated materials services including mainly reference materials and data on the properties of materials. Beyond its direct interest to the Nation's scientists and engineers, this Institute yields services which are essential to the advancement of technology in industry and commerce. This Institute is or- ganized primarily by technical fields: —Analytical Chemistry—Metallurgy—Reactor Radiations—Polymers—Inorganic Materials—Cryogenics2—Materials Evaluation Laboratory—Office of Standard Reference Materials. THE INSTITUTE FOR APPLIED TECHNOLOGY . . . provides technical services to promote the use of available technology and to facilitate technological innovation in industry and government. The

principal elements of this Institute are: —Building Research—Electronic Instrumentation—Textile and Apparel Technology Center

Technical Analysis—Center for Computer Sciences and Technology—Office of Weights and Measures—Office of Engineering Standards Services—Office of Invention and Innovation—-Clearing- house for Federal Scientific and Technical Information.3

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D. C,

20234.

2 Located at Boulder, Colorado, 80302.

3 Located at 5285 Port Royal Road, Springfield, Virginia, 22151.
UNITED STATES DEPARTMENT OF COMMERCE • John T. Connor, Secretary NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director

Standard Reference Materials:

Determination of Oxygen

in Ferrous Materials

SRM 1090, 1091, and 1092

Oscar Menis and J. T. Sterling

Institute for Materials Research

National Bureau of Standards Washington, D.C.

National Bureau of Standards Miscellaneous Publication 260-14

Issued September 23, 1966

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20 40 2 - Price 30 cents
Library of Congress Catalog Card No.: 66-61928
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 subject-oriented series will probide a means for rapid dissemination of this detailed information

and we hope will stimulate the use of standard reference

materials in science and industry.

W. Wayne Meinke, Chief

Office of Standard Reference Materials

iii
CONTENTS

PAGE

1. INTRODUCTION 2 2. SELECTION OF MATERIALS 4

3. EXPERIMENTAL 5 Vacuum Fusion Manometric Apparatus ...... 5 Vacuum Fusion CO-Infrared Apparatus 6 Inert Gas Fusion Apparatus 7 Sample Preparation 8 Sampling Policy ......... 8

4. OBSERVATION AND DISCUSSION . 9 5. ACKNOWLEDGMENTS 16

6. REFERENCES 26

7. APPENDIX 27

(Certificate of Analysis^ Standard Reference

Materials 1090 3 1091,, 1092, Oxygen in Ferrous

Materials .

)

LIST OF TABLES

Table No.

1. Effect of sample preparation conditions . . „ . 10

2. Comparison of control and SRM data ...... 13

3. Comparison of the mean and precision of

cooperating laboratories. SRM 1090-Ingot

Iron ....... o * . 18

3a. Summary of methods and conditions used at cooperating laboratories. SRM 1090-Ingot

Iron 19

4. Comparison of the mean and precision of

cooperating laboratories. SRM 1091-Stainless

Steel (AISI 431) 20

vi
LIST OF TABLES (Con't)

Table No. PAGE

4a. Summary of methods and conditions used at cooperating laboratories. SRM 1091-Stainless

Steel (AISI 4^1) 21

5. Comparison of the mean and precision of

cooperating laboratories. SRM 1092-Vacuum

Melted Steel ........... 22

5a. Summary of methods and conditions used at cooperating laboratories. SRM 1092-Vacuum

Melted Steel 25

LIST OF FIGURES

Figure No.

1. Schematic diagram of vacuum-fusion-manometric

apparatus ..... .. 5 2. Schematic diagram of vacuum-fusion-CO infrared

apparatus ......... 6

3. Schematic diagram of inert gas fusion

apparatus . ..... 7

4. Control data and homogeneity study of NBS-SRM

1090 ingot iron 12

5. Control chart of a single rod of NBS-SRM 1091

high alloy steel . . 12

6. Control chart of a single rod NBS-SRM 1092 vacuum melted steel ............. 15

7. Homogeneity study - determination from a single rod for sample weight 0.2 to 2 grams . 14 s 8. Summary of precision and accuracy of

cooperating laboratories for SRM 1090, 1091

and 1092 ........ 24,25

vii

STANDARD REFERENCE MATERIALS

DETERMINATION OF OXYGEN IN FERROUS MATERIALS - SRM 1090, 1091 and 1092

Oscar Menis and J. T. Sterling

Institute for Materials Research

National Bureau of Standards

ABSTRACT

A description is presented of methods used for the

determination of homogeneity and the establishment of the

oxygen values certified by NBS for three ferrous standard

reference materials. These standards are represented by two low alloy materials, ingot and vacuum melted iron containing

484 and 28 ppm of oxygen respectively, and a high alloy steel

containing 131 ppm of oxygen. The analyses of these materials

are based on two vacuum fusion procedures. The poor results

for the high alloy steel obtained by the first of these

methods are explained. The first method is based on manometric measurements and depends on the conversion of CO

to CO^ by copper oxide and on a differential freezing of

gases. In the second method a system is used which provides

a highly efficient degassing of sample and a direct measurement of CO by infrared absorbancy. Additional data from

an analysis by inert gas fusion method also indicate that

the homogeneity of a single rod of ingot iron, over a wide

range of sample size, has a relative standard deviation of

less than two per cent. From control data and homogeneity

studies it was ascertained that the uncertainty limits stated

in the NBS certificate include the error due to the relative

inhomogeneity between rods. Finally, data from eighteen

laboratories cooperating in this program are presented.

Key words: vacuum fusion, inert gas fusion, oxygen, ferrous

standard reference materials, CO by infrared absorbancy,

homogeneity, certified value, eighteen cooperating laboratories.

1
1. INTRODUCTION

It has been well established that even at low

concentrations , the oxygen content of ferrous and nonferrous metals has a pronounced effect (most frequently

deleterious) on their physical and mechanical properties.

The need for accurate methods for its determination in these

materials is therefore quite obvious.

The instrumental methods currently used for the determination of oxygen in metals require standards for calibrating

apparatus as well as to provide material for inter-laboratory

comparisons and agreement on values. The latter problem is

very timely as evident from a current report at an annual

meeting of Division I, Committee E-3 of ASTM at St. Joseph,

Michigan, April 4-5, 1966. Over a period of two years

they have been working on round robin studies intended to establish criteria for control of variables in order to bring

about inter-laboratory agreement for an oxygen value in a sample of material. Earlier correspondence with producers

and consumers, including members of the Iron and Steel

Institute, also pointed up the need for a certified material.

This report deals mainly with the results of analysis

of the ferrous material which led to the certification of

three Standard Reference Materials. In this study at the

NBS Analytical Chemistry Division, the vacuum fusion and gas

evolution methods were employed. A discussion is presented

of the problems associated with homogeneity testing,

establishing the precision and accuracy, and with the

evaluation of results from cooperating laboratories.

The choice of the methods and the selection of the

material is based on the Bureau's long experience in these

areas. Historically, as early as about 1925, Jordan and

Eckman of the National Bureau of Standards published a method for the determination of oxygen and hydrogen in

metals by fusion in a vacuum [1]. Oberhoffer and Schenck

published in Stahl u. Eisen [2] a report which also

contributed to the development of the vacuum fusion method

for the determination of gases in metals. In 1937 an NBS publication [3] thoroughly described an international

cooperative effort both to evaluate the accuracy of the vacuum fusion method and to compare it with other chemical

methods

.

Sloman and his associates in England were the first

investigators to systematically study this method. This

group has published a large number of papers dealing with

the subject. The most important from a theoretical point

of view is tha'c found in the 1952 Issue of the Journal of the

2
Institute of Metals [4], The other method, an inert-gas

fusion procedure, was introduced by Smiley [5] who used

capillary traps and manometric measurements. Since then

other methods of measurements, such as conductivity measurements and more recently, gas chromatographic analysis have

provided convenient and rapid methods for the determination

of the evolved CO gas. A new modification of vacuum fusion apparatus consisting

of a resistance heated all metal vacuum fusion apparatus

using an infra-red measurement of the evolved carbon monoxide

was discussed by Kraus [6] in 1962. A recent review

describing the various techniques used for the gas analysis

in metals has been presented by James [7]. Other methods,

such as activation analysis [8 J and Fassel's modification

of an inert gas fusion by means of an arc melting and

chromatographic determination of oxygen as carbon monoxide

have recently come to the forefront [9].

5
2. SELECTION OF MATERIALS

The Bureau with the cooperation of the AISI, for the

purpose of producing suitable Standard Reference Materials

,

procured several ferrous materials. These included an

ingot iron, a stainless steel (AISI 431) and a vacuum melted

steel. The ingot iron was obtained from the Armco Steel

Corporation in the form of 1/4 inch diameter centerless

ground rods, 12 feet long from a single heat preparation. It is a low-alloy material with a low carbon and a relatively

high oxygen content. Its nominal composition is as follows:

C = 0.026$; Mn = 0.043$, P = 0.004$, S = 0.016$, Si = 0.004$,

Cu = 0.095$. The second sample, a stainless steel (AISI 431)

alloy, was obtained from the Jones and Laughlin Steel

Corporation in the form of centerless ground 5/l6" diameter

rods, 12 feet long and likewise prepared from a single heat.

This high alloy steel contains an especially high percentage

of chromium which could conceivably be a source of some difficulties in an oxygen determination. It would therefore

serve as a critical standard for checking out procedures

under more demanding conditions. The material has a nominal

composition as follows: C = 0.15$, Ni = 2.2$, Cr = 15 . 8$,

V = 0.04$, N = .07$. The alloy is an important structural

material in today's technology. It contains intermediate

amounts of oxygen and relatively high amounts of nitrogen.

The third material, a vacuum melted steel, contains low

concentration of impurities as well as a low oxygen content.

The nominal composition of this material is as follows:

C = 0.016$, Mn 0.01$, P = .001$, S = .006$, Si = 0.008$,

Ni = .023$, Cr = 0.002$. It was supplied as 1/4 inch diameter

rods approximately 3 feet long by the United States Steel

Corporation.

These materials are intended primarily for the calibration of vacuum fusion and inert gas evolution apparatus,

the two most commonly used instruments and to provide stan- dards for interlaboratory checking.

4
3. EXPERIMENTAL

Three types of equipment were used in this study:

(1) Vacuum fusion-manometric measurement apparatus

(NRC-912)*, National Research Corporation, Newton Highland,

Massachusetts, is shown schematically in figure 1. The

sample was introduced into a previously outgassed system at 10-5 torr by means of sample addition devices (A) into an inductively heated furnace (B) where it was vacuum melted

in the graphite crucible at 1650 °C. The evolved gas was collected for 20 minutes in the calibrated McLeod gauge (D),

D.P

A = SAMPLE ADDITION DEVICE

B = FURNACE (INDUCTION)

C = TOEPPLER PUMP

D = McLEOD GAUGE

E = COPPER OXIDE FURNACE

F = FREEZE TRAP

D.P I. AND D.R 2 = DIFFUSION PUMPS ( MERCURY)

CONDITIONS FOR ANALYSIS TEMPERATURE 1650° C PRESSURE I0 -5 TORR

COLLECTION TIME - 15 MIN BATH -IRON

Figure 1. Schematic diagram of vacuum-fusionmanometric apparatus.

Certain commercial materials and equipment are identified in

this paper in order to adequately specify the experimental

procedure. In no case does such identification imply

recommendation or endorsement by the National Bureau of

Standards, nor does it imply that the material or equipment

identified is necessarily the best available for the purpose.

5
with a collector pump DPI and Toeppler pump (C). The total

pressure was then measured. Next, by means of the pump DP2,

the gas was circulated through a heated copper oxide tube

where the CO and Hp were converted to CO2 and H2O respectively. About 10 minutes were usually required to obtain

a constant pressure. Condensable gases were retained in a liquid nitrogen cold trap and any residual gas was then

measured as nitrogen. The cold trap was next changed to a dry ice-trichloroethylene system and the evolved CO^

measured manometrically in the McLeod gauge. Based on these

measurements, the amounts of gaseous components were calculated from the PVT relationships.

(2) The second vacuum fusion apparatus, Gas Analyser

Exhalograph EA-1*, Bendix-Balzer s Vacuum, Inc., Rochester,

N. Y. , is shown schematically in figure 2. The sample was introduced by means of the vacuum sample chamber (B) into a pre-outgassed system, .-The system was initially brought to a pressure less than 10*-° torr by means of a graphite rod

resistance furnace (A). The sample was vacuum melted in a graphite crucible at 1650 °C. Next, with a high capacity

A = FURNACE (RESISTANCE) B = SAMPLE ADDITION HEAD

C = DIFFUSION PUMP (OIL) D = COLLECTOR PUMP

E = CALIBRATION DEVICE F= INFRARED ANALYZER

G = RECORDER

H = MECHANICAL VACUUM PUMP

CONDITIONS FOR ANALYSIS TEMPERATURE 1675° C FURNACE PRESSURE I0 -5 TORR

COLLECTION TIME 4 MIN BATH -6-7gm NICKEL

Figure 2. Schematic diagram of vacuum-fusion-CO

infrared apparatus*

See footnote on page 5. 6
oil diffusion pump (C) the evolved gas was transferred into

the collector pump (D) and was contained in a standard

volume. Because of the high efficiency of the pumps, this

process takes less than 30 seconds. In practice, however,

the collection time was extended over a period of 4 minutes.

The gaseous components were measured as follows: CO in a calibrated infrared analyzer, Hg by thermal conductivity and

nitrogen or the residual gas manometrically. All these

operations were carried out semi-automatically and the data

were collected on a strip chart recorder. The apparatus

also contained a gas injection system (E) by which the

measuring systems for the three gases were calibrated, by

the introduction of standard volumes of 0g, Hg and Ng.

(3) The third instrument, an inert gas fusion apparatus.

The Leco Carbon Analyzer*, Laboratory Equipment Corp„,

St. Joseph, Michigan, is shown schematically in figure 3.

He-* =

CONDITIONS FOR ANALYSIS ATMOSPHERIC He TEMPERATURE 2100° C COLLECTION TIME 2MIN BATH - NICKEL

A= HELIUM PURIFIER

B = FURNACE (INDUCTION) C= COPPER OXIDE FURNACE

D = CHROMATOGRAPHIC ANALYZER

E= RECORDER

F= SAMPLE ADDITION HEAD Figure 3. Schematic diagram of inert gas fusion

apparatus

.

See footnote on page 5.

7
The sample was introduced into the furnace chamber (B) by

means of a sample addition head (F). It was then melted in

a previously outgassed graphite crucible which was heated

inductively to 2100 °C . The apparatus was operated under a flow of prepurified helium. The evolved CO gas was collected

over a 2-minute period and converted to CO2 by copper oxide

heated in a furnace (C) and then introduced into a chromatographic system (D) where it was collected and measured

with a thermoconductivity cell,, whose output was recorded

either in an integrating clock or on a strip chart recorder

(E).

Sample Preparation:

Samples from rods ranging from 0 0 4 to 2 grams were

sawed by hand to obtain a complete cross section. The

surfaces were carefully abraded with a clean sharp file,

degreased with CP acetone and then dried in warm air. The

samples after cutting were handled only with clean oil free

forceps and tested within an hour.

Sampling Policy:

(1) Ingot Iron - Since there was no recorded history of

the consecutive position of the rods from the single heat,

they had to be sampled at random. It was discovered, after

a considerable number of analyses, that the material was segregated into two groups of different oxygen content and it was necessary to analyze a 0.4-g sample from each of the

12-ft rods in order to sort them into their respective lots.

Only one of these groups has been certified at this time,

(2) Stainless Steel (AISI 431) - This material was also

received with no history as to the consecut iveness of the

rods. Therefore, rods were again taken at random and 0 o 8-g

samples were cut from these rods at both ends and from the

middle for analysis specimens.

(3) Vacuum Melted Steel - These rods were received in

approximately 3-ft lengths and 2-g samples were taken from

each rod.

8
4. OBSERVATION AND DISCUSSION

In certifying the oxygen content of the three ferrous

materials an effort was made to assure the highest degree

of accuracy,. Unfortunately the preparation of this type of

standard does not lend itself to synthetic control. The

goals of certifying materials to contain known amounts of

i oxygen must be attained by assuring that the material has the

best homogeneity, and that the methods used to establish the

certified values do not suffer from systematic errors. In this report the method of evaluating the homogeneity is

presented and data obtained by two relatively independent

methods are shown. These were used to establish the certified

j values. It is to be expected that, if two methods are based

on operations which are not basically alike, the agreement

in the values obtained between these are not primarily

fortuitous. In addition, results are included from

I cooperating laboratories

.

In order to attain the highest degree of accuracy

all the potential sources of error must be carefully

I controlled. As stated in the introduction, the vacuum

I fusion method has been thoroughly studied and evaluated,

j The critical requirements of these methods are well understood

and have been adhered to in the current work. With the

few stated exceptions most of the conditions involved in

this procedure were therefore not re-examined.

Starting with the sample preparation as the first

I condition, it has been long established that the surface area

to weight ratio should be minimized. This ideally requires

a production of a spherical sample „ Since spheres of

uniform oxygen content are difficult to manufacture, the

actual sample used was a cylindrical section from a rod.

This form, however, closely approximates the requirement of

a minimum surface-to-weight ratio.

The requirement of minimum surface contamination in the

process of sample preparation is evident. Therefore,

an additional test was carried out with a special sample to ascertain the best method. As shown in table 1, the values

obtained by a method in which the sample was more drastically

treated with an abrasion wheel lead to higher results. It is

evident that such a treatment contaminates the surface with

oxygen. For that reason, the slower and more reliable filing

process as described in the Experimental Section was used

throughout these tests.

9
Table 1. Effect of sample preparation conditions

Oxygen,, ppm

Samplea Sample No. Treatment Mean Std. Dev. Re.l. Std, Dev,

3.1

^31-9 B 131.2 1.3 1.0

A 171.3 .96 136 .

1 Q A 170.5 5.26

B 131.2 1.3

A 142.0 9.7

B 134.8 1.9

A 157.3 10.5

B 135.3 2.9

6.8

431-12 B 134.8 1.9 1.4

6.7

431-Cont. B 135.3 2.9 2.1

aSample treatment: (A) Cut with water coated slitting wheel

and grind surfaces on a Buehler paper disc grinder with a No. 120 grit silicon carbide paper. (B) Hand hacksaw used

to cut specimen and surface cleaned by filing with a clean

sharp file.

The next parameter has to do with the optimum temperature that must be employed with these types of materials.

It again has been widely established that I65O C assures

the complete release of oxygen from the three types of

materials studied.

In the two vacuum apparatus, two different fusion baths

also were used, an iron and a nickel. In both cases it has

been proven that they fulfill the role of good dispersants

for the carbide formed in the fusion reaction which in turn

produces surface agglomerates in the form of "kish" or dross". However, since some of the data by the cooperating

laboratories were carried out in platinum, an additional test

was carried out using a platinum bath and flux at 1900 C. The results of this experiment yielded for six determinations

on SRM 1092 an average value of 31.5 ppm + 6%. This value is

within the statistical limits of the certTfied value. Thus,

in this case, the use of the platinum bath does not significantly affect the value for oxygen.

10
It also has been proven that the high rate of outgassing

and high vacuum necessary for the release of the evolved CO

is critical. This is especially true where getter ing of

the released CO may occur by a volatile component of the

sample. With both instruments used at the Bureau, one employing a mercury diffusion pump and the other a highly

efficient oil diffusion pump, these requirements have been

met. One advantage of the oil diffusion pump is that it has

a higher capacity and pumping speed and permits a faster

outgassing of carbon monoxide from the sample melt. Any

errors due to losses from gettering of CO in the system are therefore minimized.

The final step in the methods is the measurement of the

evolved carbon monoxide. Two basically different methods

were used, one a manometric measurement with a calibrated

McLeod gauge and the other, an infrared absorbancy measurement

of carbon monoxide. In the manometric measurements there are

the additional steps for the conversion of carbon monoxide to the carbon dioxide by means of a copper oxide reactor and the

differential freezing of C02 and HpO. The use of CuO at the

Bureau has been described previously [10], It performed satisfactorily in the case of the low alloy materials, such as the

high oxygen sample of the ingot iron, and the low oxygen vacuum

melted iron. However, with the 431 stainless steel high alloy

type material, the results were erratic. This is apparent

from the data reported in table 4 dealing with the results

from cooperating laboratories. The mean value given for

Lab. NBS-A was low and the relative error large. An examination of the copper oxide used in the analysis indicated

that contamination from the sample had occurred and losses

through gettering and reduced efficiency of the reagent may

account for the low and erratic results. The second method

of measurement by infrared absorbancy is based on calibration

with standard volumes of carbon monoxide and offered an independent check on the accuracy of the measurement without

the associated problem of CO to C0

2 conversion.

In the analysis of large numbers of samples from the

different materials an effort was made to check the reproducibility of the method over a long period of time and to evaluate

the error arising from samples taken from different rods. In the case of SRM 1091 and 1092 consecutive samples from the same rod were taken and analyzed over a period of 15 and 10 days,

respectively. In the case of SRM 1090 duplicates of adjacent

samples were also taken from the center of the rods. These can

be compared with all the analyses recorded and used to obtain

the certified value. As shown in figures 4,5 and 6 and also

summarized in table 2, there is no significant difference in the

precision for the control and SRM samples for SRM 1091 Stainless

Steel and 1090 Ingot Iron. In the latter case duplicate samples

B and B ' , as shown in figure 4, also reflect the relative

11
f 6ft. .|

|- 6ft. <\ |a! !b| |b'! !c|

NUMBER OF MATERIAL RODS ANALYZED DETERMINATIONS MEAN SD R so ppm ppm %

NBS-SRM 1090 SAMPLES -B & B' 17 34 494.7 8.7 1.8

NBS-SRM 1090 SAMPLES-A,B,B\&C 17 68 494.9 15.1 3.1 Figure 4. Control data and homogeneity study of

NBS-SRM 1090 ingot iron.

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 r

02 ppm

128

4 h

M = 0

-4

-8

-12

+ 2SD

±ISC

MEAN = 132.5 ppm • STANDARD DEVIATION SD = 7.4 ppm

RELATIVE STANDARD DEVIATION RSD = 5.6%

DATA TAKEN OVER A PERIOD OF 15 DAYS

13 17 21 25 29 33

SAMPLE NUMBER

37 41

Figure 5. Control chart of a single rod of NBS-SRM 1091

high alloy steel.

12
ppm _m

i

1 1 1 1 r i—i—i—

r

r

±2SD

±ISD

MEAN = 26.4 ppm

STANDARD DEVIATION SD = 1.2 ppm

RELATIVE STANDARD DEVIATION RSD =4.4%

DATA TAKEN OVER A PERIOD OF 10 DAYS

J I I I I I I L

13 17 21 SAMPLE NUMBER

Figure 6. Control chart of a single rod NBS-SRM 1092 vacuum melted steel.

Table 2. Comparison of control and SRM data.

Control Dataa SRM Datac Oxygen,, ppm

Number Oxygen } ppm Number

SRM

Std. Relative of Std. Relative of

Mean Dev. Std. Dev. %

Determ. Mean Dev. Std. Dev. %

' Determ

1090 26.4 1.2 4.4 21 28 2 7.1 105

1090 132.5 7.4 5.6 41 131 8 6.1 286

1090 494.9 15.1 3.1 68, 484.1 14 2.9 216

494.7 8.7 1.8 34b

b Taken over a period of 10 to 15 days.

Based on duplicate determination from adjacent positions on

a rod.

15
homogeneity in that the determinations from duplicate sample

taken from adjacent position yield the greatest precision.

The data from the SRM 1092 vacuum melted material also

indicate a higher precision, the error being less from

samples taken from consecutive positions. One can conclude

therefore that the relative homogeneity of the rods are the

dominant factors which set the limit of accuracy. The

precision in the determination of oxygen from a portion of a typical 4-inch SRM sample should be better than the overall

uncertainty in accuracy which is stated in the certificate

(see appendix).

In addition, a limited study was carried out using an inert gas fusion apparatus in combination with a gas chromatographic measuring unit. Unfortunately, because of the

initial difficulties with the integrator clock used as the

readout device, the study is limited. The data are the

measurement of the thermal conductivity output from the

chromatograph with a recorder. Data are presented in

figure 7 for consecutive samples of ingot iron which varied

/

80 - / /

//

/

0 1 / I I L_L_I 1 1 1 1 1 1 1 -20 0 20 40 60 80 100 120 140 160 180 200 220 PEAK HEIGHT Figure 7. Homogeneity study - determination from a single rod for sample weight 0.2 to 2 grams.

14
in weight from 0.2 g to 2 g. The relative standard deviation

of the slope of the line was less than 2%. Since this value

is based on data taken over a wide range of sample weight it

also indicates a relative high degree of homogeneity of the

oxygen content within a given rod.

Finally, tables 3j 3a, 4, 4a, 5 and 5a and figure 8 are presented showing the results from the various cooperating laboratories.

If we use the generally accepted criteria for rejection

of values from a given laboratory whose relative standard

deviation at the 500, 100 and 50 ppm levels is greater than

5, 10 and 20 per cent respectively, one finds on inspection

of these data the following:

(1) Ingot Iron: (SRM 1090)

a. Fourteen out of 19 laboratories reported results

with relative standard deviation less than 5 per cent*.

b. Eleven of the fourteen laboratories reported mean

values which fell within the two-standard deviation limits of

the certified values for SRM 1090.

c. The mean oxygen value of these eleven laboratories

is 474 ppm.*

(2) Stainless Steel: (AISI 431)

a. Ten out of the 18 laboratories reported results

with relative standard deviation of less than 10 per cent.

b. Ten of the ten laboratories reported means which

fell within the two standard deviation limits set up as the

certified values of the SRM 1091.

c. The mean oxygen value for these ten laboratories

is 126 ppm.

(3) Vacuum Melted Steel: (SRM 1092)

a. Eighteen out of 19 laboratories reported results

which had a relative standard deviation of less than 20 per

cent.

b. Thirteen of the eighteen laboratories reported

mean values which fell within the two standard deviation

limits set up as the certified values for SRM 1091.

c. The mean oxygen value for these 13 laboratories

is 28.6 ppm

Some of the laboratories reported on sample number 10. It was found that this bar contained oxygen at a higher level;

therefore, the results received from these laboratories were adjusted so as not to include results obtained on this

specimen.

15
It is evident from these reports that the best general

agreement was obtained on samples from low alloy content

material. A larger number of cooperating laboratories had

poorer results with the high alloy steel standard.

5 . ACKNOWLEDGMENTS

We would like to acknowledge our indebtedness to

Mr. Francis Palumbo who made many of the determinations using

the NRC-912 and inert gas fusion apparatus and especially to the cooperating laboratories listed below who gave generously

of their time and talents in analyzing these materials.

Cooperating Laboratories

A. 0. Smith Corp., Milwaukee, Wisconsin. (D. E. Wallschlaeger

Allegheny-Ludlum Steel Corp., Brackenridge Works, Brackenridge

Pa. (D. P. Bartell)

Applied Research Laboratory, U. S. Steel Corp., Monroeville,

Pa. (L. M. Melnick, J. F. Martin, and R. Rapp)

Battelle Memorial Institute, Columbus, Ohio. (M. W. Mallett)

Bethlehem Steel Co., Bethlehem, Pa. (D. W. Murphy)

Bettis Atomic Power Laboratory, Westinghouse Electric Corp.,

Pittsburgh, Pa. (D. L. Smith)

Crucible Steel Company of America, Midland Works, Midland, Pa.

(R. L. Rudolph)

Graham Research Laboratory, Jones and Laughlin Steel Corp.,

Pittsburgh, Pa. (L. Pasztor)

Institute for Atomic Research and Department of Chemistry,

Iowa State University, Ames, Iowa. (V. A. Fassel and

W. E. Dallmann)

Knolls Atomic Power Laboratory, General Electric Co.,

Schnectady, N. Y. (R. F. Dufour)

Laboratory Equipment Corp., St. Joseph, Michigan. (H. J. Schmitt and G. Helling)

16
Lamp Division,, Westinghouse Electric Corp., Bloomf ield , New

Jersey. (M. F. Quaely)

Large Steam Turbine-Generator Department , Materials and

Processes Laboratory, General Electric Co., Schenectady,

N. Y. (C. C. Carson)

National Research Corp., Cambridge, Mass. (J. P. Martin)

Research and Development Center, Westinghouse Electric Corp.,

Pittsburgh, Pa. (¥. F. Harris)

Research Center, Republic Steel Corp., Cleveland, Ohio.

(M. K. Weiss)

Research Laboratory, The International Nickel Company, Inc.,

Sterling Forest, Suffern, N. Y. (C. H. Albright)

Technology Department, Union Carbide Metals Co., Niagara Falls,

N. Y. (L. A. DeAeth)

The Youngstown Sheet and Tube Co., Youngstown, Ohio. (W. F. Harris

)

U. S. Army Materials Research Agency, Watertown, Mass.

(S. Vigo and F. P. Valenti)

17
Table 3- Comparison of the mean and precision

of cooperating laboratories.

SRM 1090 - Ingot Iron

Oxygen s ppm

Number

Std. Relative of

Lab. Mean Dev. Std. Dev. Determ,

1 400. 3 29.5

7° 30

2 oyy .d Qlift ll JH-0 . 4 hn ft 4y . 0 id

3

)\ c;c ft dU . £i 4.4 id 4 inn ft 00 7 03. ( ftO . Od

1

id

5 10 h -l-0«4 O 7 0

y

0 1 ( . O Q Q 3 • y X £1 7

)|Q7 7 y* r i1.0ft "I 1 1

p0 ^uy . 1 J-C- • D d. • *+ Q

9 Hpy . y O.O (0 ft 10 H-^O . U 9.1 0 ri d . U 15 11 449.2 27.4 6.1 12

12 454.9 16.7 3.7 15

13 465.5 9.0 1.9 9 14 458.9 19.6 4.3 9 15 446.7 6.9 1.5 12 16 443.5 7.1 1.6 12 17 532.3 23.8 4.5 6 NBS--Aa 462.9 11.2 2.4 88

NBS--Bb 484 14 2.9 216

Jsee footnote 1 in table 3a.

'See footnote m in table 3a.

18
Table 3a. Summary of methods and conditions used at cooperating laboratories.

SrtM luyu - ingot Iron

Weight

Collection of

Lab

.

Method Temperature time sample Bath

°C (min .

)

(g)

1 Vacuum fusion a 1650 30 2 None

2 Vacuum fusion 1650 — 1.0-1.5 None

3 Inert ££as fusion13 2350 6 0.4-0.7 Ptc 4 Vac uum fusion 1650 15 0.3-0.5 Fe

5 Vacuum fusion 1650 .6-1.9 Fe

6 No information available

7 Vacuum fusiond 1700 3 0.5-1.5 Ni-Fe

8 Inert gas fusion 2000 -- 0.5-2.5 None

9 Vacuum Q fusion 1850 5 1.0-1.4 pt f

10 Vacuum fusion 1700-1800 10 I.O-2.5 None

11 Vacuum fusion 1650 20 0.7-3.0 Fe g 12 Vacuum fusion^ 1650 1 20 1.0-2.0 Fe

13 Vacuum „ . h fusion 1850 20 1 Fe

14 Vacuum „ . h fusion 1650 -- 1.2-1.8 None

15 Vacuum fusion 1950 5 0,5 Pt J

' 16 Vacuum * . h fusion 1830-1920 15 1.1-1.8 None

17 Vacuum „ . k fusion 1650 15 1 Fe NBS-A Vacuum ~ . 1 fusion 1650 20 2 None

NBS-B Vacuum „ . d fusion 1650 4 0.5 Nim

^Constructed in laboratory.

Leco.

.Pt: sample = 6:1. B.B. Exhalograph EA-1.

e Used Model 21-610 mass spectrometer for analysis of gases.

gPt: sample = 1.3:1.

°FIve grams Fe

.

NRC

.

A few samples run using Pt bath 1950-2000 °C.

J 2.5 g Pt degassed for 3 minutes

^before each sample is added.

, Serf ass analyzer

NRC-modified for fractional

freezing.

^Approximately 7 grams Ni

bath used.

19
Table 4. Comparison of the mean and precision

of cooperating laboratories.

SRM 1091 - Stainless Steel

(AISI 431)

Oxygen, ppm

1 — Number

Std. Relative of

Lab. Mean Dev. Std. Dev. Determ.

$

b

1

1 41.2 12.2 29.2 30

2 100.0 22.7 22.7 20

3 98.3 29.2 29.7 12 4 134.2 5.2 3.8 12

6 120.8 5.2 4.3 12

7 125.3 6.2 4.9 13

8 127-0 6.5 5.1 12

9 72.2 17.5 24.3 12

10 128.0 7.8 6.1 15

11 107.7 16.6 15.4 14

12 120.3 4.1 3.4 12

13 132.0 oil 0 24 . J

-1 Q li lO . 4 17

14 118.9 9.7 8.2 12

15 99-5 11.3 11.4 12 16 113.9 5.3 4.7 12

17 136.2 2.9 2.1 9 NBS-Aa 104.3 14.6 14.0 85

NBS-* B 131 8 6.1 286

JSee footnote n in table 4a. See footnote d in table 4a.

20
Table 4a. Summary of

cooperating

methods and conditions

laboratories

. used at SRM 1091 - Stainless Steel

(AISI 4^1)

Lab. Method

Collection

Temperature time

°C (min.

)

Weight

of

sample

(g)

Bath

j 1 Vacuum a fusion 1650 30 2 None

1 2 Vacuum fusion 1650 1.0-1.5 None

1 3 Inert £ b^as fusion 2350 6 0.4-0.7 Pt

c

! 1

1 Vacuum fusion 1650 15 0.3-0.5 Fe

I 6 No information available

Vacuum fusiond 1900 3 0.5-1.5 Pt

e 8 Inert g „ . b

^as fusion 2000 0.5-2.5 None

9 Vacuum f fusion 1850 5 1.0-1.4 Pt g

10 Vacuum fusion 1700-1800 10 I.O-2.5 None

11 Vacuum fusion 1650 20 0.6-3.8 Feh

12 Vacuum fusion1 1650 20 1.0-2.0 Fe J 13 Vacuum fusion1 1850 20 1.0 Fe

14 Vacuum fusion1 1800

1975

1.6-2.0

1.6-2.0

None

Pt&Sn

15 Vacuum fusion 1950 5 0.5 Pt k

16 Vacuum fusion1 1830-1920 15 1.1-1.8 None"

1" 17 Vacuum „ . m

fusion 1650 15 0.75 Fe NBS-A Vacuum fusion11 1650 20 0.5 None

NBS-B Vacuum f usiond 1650 4 0.75 Ni°

.Constructed in laboratory.

c Leco.

JjPti sample = 6:1.

e B.B. Exhalograph EA-1.

25 g Pt bath maintained at

LfLeast Pt: S = 3:1.

Used model 21-610 mass spectrometer for analysis of gases, gPt: sample = 1.3:1.

•Five grams Fe. NRC

.

J A few samples run using Pt bath at 1950-2000 oc. 2.5 g Pt degasses for 3

1minutes before sample is added m

Tin added- intermittently.

Serf ass analyzer.

nNRC-modif ied for fractional

freezing.

Approximately 7 grams Ni

bath used.

21
Table 5« Comparison of the mean and precision

of cooperating laboratories.

SRM 1092 - Vacuum Melted Steel

Oxygen, ppm

Number

Std. Relative of

Lab. Mean Dev. Std. Dev. Determ.

7*

1X 1Q fl ± c. 0CL Pft 7 x . U P • P

Q

OD

OP. "2 do . jj M- . 1 0

0 c 0

or? • 0 Jo 1U . U 9

5 2o . 0 . 4 1.3 0

c

0 30 .

1.5 4.9 9

7 2o . 0 • 52 1 . 0

00

QO 27.1 2.9 10.7 QO

9 23.

1.9 00 .

r

O 10 26 .

5.2 19.3 rO 11 28 .

1.5 5.0 9 12 28.3 •9 3.2 08 13 31.0 2.4 7.7 6 14 25.5 2.3 9.1 9 15 19.0 .9 4.6 9 16 30.5 1.6 5.2 6 17 34.3 5.2 15.0 6 NBS-Aa 32.4 1.8 5.6 27

NBS-Bb 28 2 7.1 105

^See footnote m in table 5a. See footnote d in table 5a.

22
Table 5a. Summary of methods and conditions used at cooperating laboratories.

SRM 1092 - Vacuum Melted Steel

Lab. Method Temperature

°C

Collec t ion

time

(min.

)

Weight

01 sample

(g)

Bath

1 Vacuum fusion 1650 30 2 None

2 Vacuum fusion 1650 1.0-1.5 None

3 Inert gas fusion 2350 6 O.4-O.7 Pt c 4 Va.cuum fusion 1650 15 1.0 Fe

56 Vacuum fusion

No

1650

information available

3.0 Fe

7 Vacuum d fusion 1700 3 1.5 Ni-Fe

8 Inert £ b5as fusion 2000 2.5 None

9 Vacuum fusion 1800 5 1.0-1.4 Pt

f 10 Vacuum fusion 1700-1800 10 2.5 None

11 Vac uum fusion 1650 20 2.4-2.8 Feg 12 Vac uum

~ . h fusion 1650 1 20 1-2 Fe

13 Vacuum v . h fusion 1850 20 1 Fe

14 Vacuum „ . h fusion 1650 — 1.6-2.0 None

15 Vacuum fusion 1950 5 0.5 Pt J

' 16 Vacuum ~ . h fusion 1830-1920 15 1.1-1.8 None^" 17 Vacuum fusion"'' 1650 15 1.0 Fe NBS-A Vacuum „ . m fusion 1650 20 2.5 None

NBS-B Va,c uum

„ . d fusion 1650 4 2.0 Nin

^Constructed in laboratory.

Leco.

?Pt: sample = 6:1. "B.B. Exhalograph EA-1

.

Used model 21-610 mass spectrometer for analysis of gases.

*Pt: sample = 1.3:1.

°Five grams Fe

NRC

.

x Pt bath at 1950-2000 used for

.one specimen.

J 2.5 g Pt degassed before each

^sample is added.

-^Tin added intermittently.

.Serf ass analyzer mNRC -modified for fractional

freezing

.

Approximately 7 grams Ni

bath used.

23
i

1 1 r

H= 699 +348.4

1

1 1 1 • OBSERVED MEAN O ± I STANDARD DEVIATION INTERVAL A ± 2 STANDARD DEVIATION INTERVAL [%) RELATIVE STANDARD DEVIATION

i±

1344 J 2_ J L

SRM 1090

I I

I 2 3 4 5 6 T 8 9 10 II 12 13 14 15 16 17 NBS NBS |Q%| [408%] |D%1 [3l%l fl8%| f24»1 |Q%] |Q%| |6l*] [jjg [jjg [jjg [Lai (A) (B) CERTIFIED LABORATORIES [M%] [2l%]

1 r

• OBSERVED MEAN O + I STANDARD DEVIATION INTERVAL A + 2 STANOARD DEVIATION INTERVAL E) RELATIVE STANDARD DEVIATION

--*—-?-

-

SRM 1091

I

, 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 K "»» »°» [ZQ%1 |22J%1 1H!%| P%1 ^ISElI^lffillSlimilSIISIIS'lSEilTM ^CERTIFIED

1 14.0% I |6.l%| LABORATORIES

24
J.

1 5.6%

• OBSERVED MEAN O ± I STANDARD DEVIATION INTERVAL A ± 2 STANDARD DEVIATION INTERVAL GO RELATIVE STANDARD DEVIATION J L

SRM 1092

J L

I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 NBS MBS

[35J%] |5l%l [iml H5%| p%1 [4l%1 fll»1 fibl%1 |0%1 [To*! fl2%] [7T7%1 [ml [4l%] [l2%] p5J%l (A) (B) CERTIFIED LABORATORIES |T6*]

Figure 8, Summary of precision and accuracy of cooperating

laboratories for SRM 1090, 1091 and IO92.

25
6 . REFERENCES

[1] Jordan, L. , Eckman, J. R. , Ind. and Eng. Chem. 18,

279-282 (1926).

[2] Oberhoffer, P. Yons Schenck, H. a Stahl u. Eisen 47,

1526 (1927). ~~

[3] Thompson, J. G. 3 Vacher, H. C, Bright, H. A., J. of

Res. NBS 18, 259 (1937).

[4] Sloman, A. A., Harvey, C. A., J. Inst. Metals 80,

391 (Appendix - 0. Kubasekewski. ) (1952).

[5] Smiley, W. W., Anal. Chem. 27, IO98 (1955).

[6] Kraus, Von Thaddaus, Arch. Eisenhuttenw. 33 ^ 527 (1962).

[7] James, J. A., Metallurgical Reviews 9_, 93 (1964).

[8] Harris, William F. , Talanta 11, 1376 (1964).

[9] Winge, R. K. and Fassel, V. A 0 , Anal. Chem. 37 67

(1965). ~~

[10] Walter, D. I., Anal. Chem. 22, 297 (1950).

26
U. S. Departnjjy& of Commerce

John T. €TJ^CT?ecretary

Certificate of &nalp£i*

Standard Reference Materials 1090, 1091, 1092

Oxygen in Ferrous Materials

(By Vacuum and Inert Gas Fusion Methods)

No. Type Oxygen, ppm Uncertainty, ppmd 1090 Ingot Iron" 484« 14

1091 Stainless Steel (AISI 431)" 131' 8 1092 Vacuum Melted Steelc 28<= 2

Size: 1090, rods % in. in diameter and 4 in. long; 1091, rods %

This

and 4 in. long; 1092, rods '4 in. in diameter and 4 in. long.

» Determination on 0.5g sample,

b Determination on 0.75g sample

e Determination on 2g sample.

include nethod, as well as dif- inhomngeneity of the

ibtained at NBS, is the average of 216 de- terminations on 54 rods. An average value of 487 parts per

million was obtained by 18 cooperating laboratories. Of the

18 laboratories reporting, 7 were within the 2-sigma limit, 15 within the 3-sigma limit and 3 were outside the 3-sigma

' This value, obtained at NBS, is the average of 105 de terminations on 105 rods. An average value of 29 parts pei million was obtained by 13 cooperating laboratories. Of th< 13 laboratories reporting, 12 were within the 2-sigma limi CAUTION: Oxygen determinations should be made on thoroughly and freshly cleaned samples that represent the full cross-section of the rods.

List of Analysts

1. J. T. Sterling, F. J. Palumbo, and O. Menis, Division of Analytical Chemistry, Institute for Materials Research, National Bureau of Standards.

2. L. M. Melnick, J. F. Martin, and R. Rapp, Applied Research Laboratory, United States Steel Corp., Monroeville, Pa.

3. W. F. Harris, Research and Development Center, Westinghouse

Electric Corp., Pittsburgh, Pa.

4. L. A. De Aeth, Technology Department, Union Carbide Metals Co., Niagara Falls, N. Y.

5. M. K. Weiss, Research Center, Republic Steel Corp., Cleveland,

Ohio.

6. D. E. Wallschlaeger, A. O. Smith Corp., Milwaukee, Wise.

7. S. Vigo and F. P. Valenti, U. S. Army Materials Research Agency, Watertown, Mass.

8. W. F. Harris, The Youngstown Sheet and Tube Co., Youngstown,

Ohio.

9. D. L. Smith, Bettis Atomic Power Laboratory, Westinghouse Electric Corp., Pittsburgh, Pa.

10. D. W. Murphy, Bethlehem Steel Co., Bethlehem, Pa.

M. F. Quaely, Lamp Division, Westinghouse Electric Corp., Bloomfield, N. J. R. F. Dufour, Knolls Atomic Power Laboratory, General Electric Co., Schenectady, N. Y.

C. C. Carson, Large Steam Turbine-Generator Department,

Materials and Processes Laboratory, General Electric Co., Schenectady, N. Y.

C. H. Albright, Research Laboratory, The International Nickel Company, Inc., Sterling Forest, SufFern, N. Y. M. W. Mallett, Battelle Memorial Institute, Columbus, Ohio.

J. P. Martin, National Research Corp., Cambridge, Mass.

D. P. Bartell, Allegheny-Ludlum Steel Corp., Brackenridge Works,

Brackenridge, Pa.

L. Pasztor, Graham Research Laboratory, Jones and Laughlin Steel Corp., Pittsburgh, Pa. H. J. Schmitt and G. Helling, Laboratory Equipment Corp., St. Joseph, Mich.

R. L. Rudolph, Crucible Steel Company of America, Midland Works,

Midland, Pa.

Washington, D. C. W. Wayne Meinke, Chief March 1, 1966 Office of Standard Reference Materials 27
SUPPLEMENTARY INFORMATION

OTHER ELEMENTS: Although not certified at this time, nitrogen was determined by a distillation-photometric method,

with the following results:

Nitrogen, ppm

1090..

1091..

1092..

63 865

10 PREPARATION FOR THE DETERMINATION OF OXYGEN:

1. Samples should be cut from the original rod in such a manner as to minimize heating of the sample; i.e., by a hand

hacksaw.

2. All surfaces of the cut sample should be thoroughly cleaned with a fine file. 3. Samples should be washed with CP. ether, acetone, or other suitable solvent, dried in a stream of warm clean air and

then handled only with clean forceps.

4. Analyses should be made as soon as possible after cleaning the sample. CONDITIONS FOR ANALYSIS AT NBS:

Method Vacuum fusion Furnace temperature ...1675 °C. Furnace pressure .. <10-5 Torr.

Collection time 4 mins. Bath material... .....High-purity nickel Carbon monoxide determination... Infrared absorption When these conditions are used, together with the certified values, the three Standard Reference Materials plot to a straight-line analytical curve. A complete report on the testing and analysis of these materials will be published in the NBS Misc. Publ. 260 Series. The material for these Standards was furnished to NBS by Armco Steel Corp., Jones and Laughlin Steel Corp., and U. S. Steel Corp.

28
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)
i

!

|

!
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)

»U.S. GOVERNMENT PRINTING OFFICE: 1966 —251 -019/21*
I

1

U.S. DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20230 POSTAGE AND FEES PAID

U.S. DEPARTMENT OF COMMERCE OFFICIAL BUSINESS