IS 6396: Methods of Measuring Decarburized Depth of Steel

10 Pages·2000·1.2 MB·English

by  Bureau of Indian Standards

इंटरनेट मानक
Disclosure to Promote the Right To Information
Whereas the Parliament of India has set out to provide a practical regime of right to
information for citizens to secure access to information under the control of public authorities,
in order to promote transparency and accountability in the working of every public authority,
and whereas the attached publication of the Bureau of Indian Standards is of particular interest
to the public, particularly disadvantaged communities and those engaged in the pursuit of
education and knowledge, the attached public safety standard is made available to promote the
timely dissemination of this information in an accurate manner to the public.
“जान1 का अ+धकार, जी1 का अ+धकार” “प0रा1 को छोड न’ 5 तरफ”
Mazdoor Kisan Shakti Sangathan Jawaharlal Nehru
“The Right to Information, The Right to Live” “Step Out From the Old to the New”
IS 6396 (2000): Methods of Measuring Decarburized Depth of
Steel [MTD 22: Metallography and Heat Treatment]
“!ान $ एक न’ भारत का +नम-ण”
Satyanarayan Gangaram Pitroda
““IInnvveenntt aa NNeeww IInnddiiaa UUssiinngg KKnnoowwlleeddggee””
“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता हहहहै””ै”
Bhartṛhari—Nītiśatakam
“Knowledge is such a treasure which cannot be stolen”

IS 6396:2000

Indian Standard
METHODS OF MEASURING DECARBUNZED
DEPTH OF STEEL
(Second Revision )
ICS 77.080

C) BIS 2000
BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002

Price Group 2
/;/j.:t[.s/2000
Metallography and Heat Treatment Sectional Committee, MTD 22
FOREWORD
This Indian Standard (Second Revision) was adopted by the Bureau of Indian Standards, after the draft finalized
by the Metallography and Heat Treatment Sectional Committee had been approved by the Metallurgical Division
coLlncil,
This standard was first published in 1971 and was revised in 1983. On the basis of experience gained and recent
cievelopments, the committee decided to revise this standard. In the present revision the following modifications
have been made :
a) Spectrometer Method has been added under Chemical Analysis Method.
b) Microhardness Method has been incorporated in the main methods.
c) ASTM and JIS standards have also been considered while considering this revision.
d) A new clause has been added giving details of various IS standards to be referred to in utilizing this
standard.
This standard outlines the methods for measuring and designating decarburized depth of steel.
In the preparation of this standard, assistance has been derived from the following standards:
GOST 1763-42 Method for microscopic determination of decarburized depth in semi-finished and
finished steel products committee of the Russian Federation for Standardization,
Metrology and Certification.
SAE.1419 Methods of measuring decarburization.
ASTM-E 1077-85 The Society of Automotive Engineers, ‘U.S.A and The American Society of Testing
Mate~ial.
JIS-Ci0558 Japanese Industrial Standards Committee.

For the purpose of deciding whether a particular requirement of this standard is complied with the final value

observed or calculated, expressing the result of test or analysis, shall be rounded off in accordance with
IS 2: 1960 ‘Rules for rounding off numerical values (revised)’. The number of significant places retained in
the roLmding off value should be the same as that of specified value in this standa:d.
IS 6396:2000
Indian Standard
METHODS OF MEASURING DECARBURIZED
DEPTH OF STEEL
(Second evision )
1 SCOPE homogeneous microstructure.
This standard specifies the following methods of The chemical analysis method is limited to simple
measuring decarburized depth of steel and also lays shapes and is generally used only for research
down the code for designating decarburized depth: investigations.
a) Microscopical method 4 TERMINOLOGY
b) Microhardness method
For the purpose of this standard, the following defin-
— cross section traverse
itions shall apply.
— longitudinal traverse
c) Chemical analysis method 4.1 Decarburization
— combustion method It is the loss of carbon from the surface layers of steel
— spectrometer method at high temperatures under oxidizing conditions.
Decarburization may be complete or partial (see
2 REFERENC~S Fig. 1).
The following Indian Standards are necessary adjuncts
to this standard:
ISNo. Title
228:1959 Methods of chemical analysis of
steels
1501 Method for Vickers hardness test for
metallic materials
5072: 988 Method for Rockwell superficial LCOMPLETE--+PARTIAL 4
hardness test (N&T scales) for steel DECARBURIZATION
6885: 973 Method for knoop hardness testing

of metals FIG. 1PARTIALANDCOMPLETEDECARBURIZATION

4.2 Depth of Complete Decarburization
3 SELECTION OF METHOD
The depth below the SLUlace of steel to the zone where
These methods are intended to measure decarburized phases other than ferrite begin to appear. The complete
depth of steel due to heating at elevated temperatures decarburized layer is the layer where only ferrite is
during hot working or by detecting changes in the present.
microstructure, hardness or carbon content at the
surface. The decarburized depth is taken as the depth 4.3 Zone of Partial Decarburization
where a uniform microstructure, hardness or carbon
Itis characterized by partial reduction of carbon
content of the base material is observed.
concentration in the surface layer. In the presence of
3.1 The method to be used is dependent on accuracy a completely decarburized zone, the zone of partial
desired, the degree of decarburization, microstructure decarburization isatransition zone inwhich the ferrite
and base carbon content of the steel. structure blends into the base structure of the metal.
The microscopic method issufficiently accurate for — 4.3.1 In the absence of a zone of complete decarbu-
ashc:-rolled, as forged, as annealed and as normalized rization, the zone of partial decarburization shall be
sample’ 5ut not for small amount of decarburization measured from the edge of amicro section to the base
in steels having high carbon (above 0.70 percent), high
structure of the metal, whereas in the presence of a
alloy content or high hardness.
completely decarburized zone, it shall be measured
Microhardness method is suitable for accurate mea- from the first bands of pearlite or other stmctural
surement of hardened structures with relatively constituent to the base structure of the metal.
1
iS 6396:2000
4.4 Total Depth of Decarburization epoxy materials generally give the best edge retention
of the commonly available plastics. An additional
The perpendicular distance from the surface of steel
method of protection is to electroplate a metallic
to the part where the carbon content of the base metal
coating of 0.025 to 0.075 mm on the specimen before
isfound. Total depth of decarburization shall be equal
mounting.
to the depth ofcomplete decarburization pius the depth
of parlia! decarburization, 6.2.1 Polishing must be done in accordance with good
metallographic practice to produce a true represen-
4.5 Decarburized Depth of Specified Residual
tation of the surface microstructure.
Carbon Percentage
6.2.2 Etching in 3 percent nital (cone. HNO~ in
The depth from the surface of the steel to the part
alcohol) is usually suitable for showing changes in
having the specified residual carbon percentage.
microstructure caused by decarburization. Special
etcha’nts may be used, if required, subject to an
4.6 Decarburized Depth of Specified Hardness
agreement between the manufacturer and the
The depth from the surface of the steel to the part purchaser.
where the specified hardness is obtained.
6.3 Measurement
5 SA,MPLING
Generally a magnification of 100 x is used. The
The samples shall be taken at locations that are magnification should be high enough to resolve the
representative of the bulk specimen. The number of structure and to achieve the desired accuracy. If the
test pieces to be used for testing and their selection microscope is of a type with a ground glass screen,
shall be as agreed to between the manufacturer and theextent of decarburization may be measured directly
the purchaser. with ascale. Ifan eye-piece is used for measurement,
it should have a cross hair or a scale.
6 MICROSCOPIC METHOD
6.3.1 For each sample, several measurements (five at
This method isbased on evaluation of the variation in
the maximum) shall be carried out in the deepest
microstructure at the surface due to change in carbon
uniformly decarburized zone. The average of these
content.
rneasurernents defines the maximum depths of total
decarburization (see 4.4). Points of extreme depth of
6.1 Specimen
decarburization shall be excluded except if agreed to
The somple to be examined shall be cut at right angles by the Contracting Parties concerned.
to the longih~dina] axis of the product so that mea-
smements are made on atransve r se plane. The depth 7 MICROHARDNESS METHOD

of dccarburization shall be dete rmined on semi-
It is suitable for measuring decarburization depth in
finished and finished products in the condition ‘as
heat-treated samples. lt is not suitable if two
supp!iwi’. If the products to be evaluated have been
constituents of significantly different hardness are
subjected to hardening or cold-working, they may,
present. It is based on the variation in microhardness
bcfol-e examination, be normalized or annealed insuch
with respect to “the depth below the surface due to
away ihat they are protected against additional decar-
depletion in carbon.
5urization or carburization. For sections up to 25 mm
diameter, the entire cross-section is polished and 7.1 Cross Section Microhardness Traverse
examined. For iar.gersections, one or more samples
7.LI Specimen
shall be prepared to assess variation in surface
decarburization. Comers of straight sided sections The sample to be checked shall be cut at right angle
shou id not be incIuded, since they are not considered tothe longitudinal axis of the product so that measure-
rqxwscmtative. ments are made on transverse plane. If cross-section
istoo large, aportion of suitable size including surface
6.2 Preparation
to be checked should be cut for examination.
.%mp!e polishing shall be done in such a way that
7.L2 Preparation
edge rounding is avoided. Samples, which are small
h case of hardened and tempered material, no further
or of an inconvenient shape, should be mounted in a
~lan~p or in a p]astic mount. Compression mounting treatment is necessary. In case of non-hardened
2
IS 6396:2000
materials, samples may be hardened by quenching at which no increase in hardness is found. After the
after heating under conditions which minimize hardness traverse, the hardness values need to be
further change in carbon distribution. The soaking plotted on graph paper. The decarburised depth can
period should be minimized to avoid excessive carbon then be determined accurately from the hardness
diffusion. profile.
For sections up to 25 mm, the entire cross-section
8 CHEMICAL ANALYSIS METHOD
should be polished and examined, if necessary after
mounting. This method isnormally used only in research investi-
gations or to check the accuracy of other methods.
7.1.3 Measwements
Analysis is difficult and,slow in application because
A series of microhardness impressions shall be made of limitation of size and section of material. Method
at right angles to the decarburized surface by Vickers of procuring sample itself depends upon shape and
or Knoop indenters from the surface until the hardness hardness of test piece. Measurements by this method
of the base metal is obtained. If Knoop indentor is will usually produce greater estimates of total depth
used, its long axis should be parallel to the sample of decarburization than the other methods.
surface.
This method isused for samples with asimple uniform
The applied test load should be appropriate to mini- shape and is based on analysis of incremental layers >--
mize inaccuracy in diagonal measurement. A load of after turning or milling.
300 g or 500 g is recommended.
8.1 Combustion Method
7.2 Longitudinal Traverse (Taper or Step Grind)
8.1.1 Specimen
7.2.1 Specimen Test specimens or parts too hard to machine may
A specimen containing the surface on which decarbu- be tempered at 600 to 650°C to permit machining
of surface layers into chips for subsequent carbon
rization is to be measured, is prepared so that it may
analysis. Care should be taken to avoid further
be manipulated on a superficial hardness tester.
decarburization during tempering.
7.2.2 Preparation
8.1.2 Successive layers of 0.1 mm thickness, parallel
If the specimen is not in the hardened condition, it is
to the surface of the test piece, are removed by dry
recommended that it be hardened by quenching after
machining avoiding all contamination. Any surface
heating under conditions which avoid further change
oxide should be removed before machining. Corners
in carbon distribution. should be avoided while milling. Weight of the chips

must be sufficient to permit accurate analysis.
7.2.2.1 For the taper grind specimen, a shallow taper
is ground through the dccarburized layer. The angle 8.1.3 Analysis
is chosen so that hardness readings, spaced equal
Analysis for carbon content shall be done in accor-
distances apart, will represent the hardness at the
dance with latest version of IS 228.
desired increments below the surface. Unless special
anvils are used on the hardness tester, aparallel section 8.1.4 Measurement Procedure
should be prepared so that indentations will be atright
The depth of total decarburization shall be measured
angles to the tapered surface.
from the surface to the part of the sample in which
7,2.2.2 For the step grind procedure, flats are ground the carbon content does not differ from the minimum
at predetermined intervals below the original surface. content of the nominal range of the product minus the
These flats should have sufficient area to allow several permissible negative check-analysis variation, by more
!~ardness readings to be taken on each flat. than the values given below:
7.2.3 Measurement Nominal Content of Permissible Deviation
the Product Max
A superficial hardness tester such as a Rockwell
superficial or Vickers tester using a light load should Carbon percent up to 0.60 0.03 percent Carbon
be employed in making the hardness measurements.
Carbon percent above 0.60 5percent of nominal
The depth of decarburization isdefined asthe distance
content
measured from the nearest original surface tothe point
3
IS 6396:2000
8.2 Spectrometer Method 9.1 The indication of the depth of decarburization
shall be made by the following notations:
In this method, the sample is ground to known depths
and the surface is sparked to determine the carbon
Depth of Microscopic Hardness Chemical
content using an optical emission vacuum spectro- the Decar- Examiriation Test Analysis
meter. This method is restricted to flat surfaces. burized Layer Method Method Method
8.2.1 Specimen Total depth of DT XX M DTH xx ~lJDT xx A
decarburization
Specimens are taken containing the surface on which Depth of DF XX — —
decarburization is to be measured. decarburization
8.2.2 Preparation Decarburized — — DSC(...)2)
depth to specified XXA
Surface scale is removed before initial grinding. The residual carbon
sample is then ground parallel to the longitudinal
Decarburized — DSH(...) —
surface of the sample incrementally to known depths. depth to speci- xx HX
The depth is measured using a micrometer. fied hardness
I)[ndlcatetypeoftestorloadifhardnesstestis carriedbytheVickers
8.2.3 Analysis
method,forexample,HRNindicates hardnessmeasureonRockwell
The surface is sparked after each grind and the carbon NScale,H5indicatesVickerstestwith5kgload.
content is determined. Successive sparkings should 2)S~cifred carbon~ercentageinbrackets,inunitsof0.01.
not be superimposed and corners should be avoided.
Specified hardness in brackets, in relation to the type
8.2.4 Measurement of test indicated at the end of notation.
The depth of total decarburization shall be measured Examples:
from the surface to the part of the sample where the
S1 Notation Description
carbon content becomes constant and does not differ
No.
from the minimum content of tlienominal range minus
the negative permissible check-analysis variation by 1. DT28M Total depth of decarburization
more than the values given below: measured by the microscopic
method – 0.28 mm
Nominal Content of Permissible Deviation
2. DT 30 A Total depth of decarburization
the Product Max
measured by chemical analysis
method – 0.3 mm
Carbon percent up to 0.60 0. 03 percent carbon

3. DT20HVY Total depth of decarburization
Carbon percent above 0.60 5pe rcent of nominal
measured by Vickers micro
content hardness test at a load of ‘Y’ g
4. DF5M Depth of complete decarburi-
9 DESIGNATION OF DECARBURIZED DEPTH
zation measured by the micro-
The depth of decarburized layer shall be calculated scopic method – 0.05 mm
toone place ofdecimal when measured by the chemical 5. DSC(40)20A Decarburized depth to the
method (see 8) and hardness method (see 7) and specified carbon content of
to two places of decimals when measured by 0.40 measured by the chemical
analysis method – 0.2 mm
the microscopic (see 6) method. The depth shall be
expressed in units of 0.01 mm. 6. DSH(70)20 HRN Decaburized depth to specified
hardness of 70 HRN – 0.2 mm
Bureau of Indian Standards
BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promote
harmonious development of the activities of standardization, marking and quality certification of goods
and attending to connected matters in the country.
Copyright
BIS has the copyright of all its publications. No part of these publications may be reproduced in any form
without the prior permission in writing of BIS. This does not preclude the free use, in the course of
implementing the standard, of necessary details, such as symbols and sizes, type or grade designations.
Enquiries relating to copyright be addressed to the Director (Publications), BIS.
Review of Indian Standards
Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewed
periodically; a standard along with amendments is reaffirmed when such review indicates that no changes are
needed; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standards
should ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of
‘BIS Catalogue’ and ‘Standards: Monthly Additions’.
This Indian Standard has been developed from Doc :No. MTD 22 (3825).
Amendments Issued Since Publication
Amend No, Date of Issue Text Affected
BUREAU OF INDIAN STANDARDS

Headquarters :

Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002 Telegrams : Manaksanstha
Telephones :3230131, 3233375, 3239402 (Common to all offices)
Regional Offices : Telephone
Central : Manak Bhavan, 9 Bahadur Shah Zafar Marg 3237617
NEW DELHI 110002 { 3233841
Eastern : 1/14 C. 1.T. Scheme VII M, V. 1.P. Road, Kankurgachi 3378499,3378561
CALCUTTA 700054 { 3378626,3379120
Northern : SCO 335-336, Sector 34-A, CHANDIGARH 160022 603843
602025
{
solithern : C. 1.T. Campus, IV Cross Road, CHENNAI 600113 2350216,2350442
2351519,2352315
{
Ww[crn : Manakalaya, E9 MIDC, Marol, Andheri (East) 8329295, 8327858
MUMBAI 400093 { 8327891,8327892
f31”allches : AHMADABAD. BANGALORE. BHOPAL. BHUBANESHWAR. COIMBATORE.
FARIDABAD. GHAZIABAD. GUWAHA~I. HYDERABAD. JAIPUR. KANPUR.
LUCKNOW. NAGPUR. PATNA. PUNE. RAJKOT. THIRUVANANTHAPURAM.

Printed at PRINTOGRAPH, New Delhi