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Ref. No.: ISO/R 635 - 1967 (E)
IS0
INTERN AT I ON AL ORGAN I Z AT1 O N FOR STAND AR D I Z AT I O N
IS0 RECOMMENDATION
R 635
CODE OF SYMBOLS FOR COVERED ELECTRODES
FOR ARC WELDING OF MILD STEELS
AND LOW ALLOY HIGH TENSILE STEELS
1st EDITION
November 1967
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 635, Code of Symbols for Covered Electrodes for Arc Weld-
ing of Mild Steels and Low Alloy High Tensile Steels, was drawn up by Technical Committee
ISO/TC 44, Welding, the Secretariat of which is held by the Association Française de Normali-
sation (AFNOR).
Work on this question by the Technical Committee began in 1953 and led, in 1957, to the
adoption of a Draft IS0 Recommendation.
In September 1957, this Draft IS0 Recommendation (No. 178) was circulated to all the
IS0 Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial
nature, by the following Member Bodies :
Bulgaria India Portugal
Burma Israel Romania
Czechoslovakia Italy Spain
Denmark Japan Sweden
Finland New Zealand Switzerland
France Norway United Kingdom
Greece
Poland Yugoslavia
Four Member Bodies opposed the approval of the Draft.
Belgium
Netherlands
Republic of South Africa
U.S.S.R.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council,
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which decided, in November 1967, to accept it as an IS0 RECOMMENDATION.
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ISO/R 635 - 1967 (E)
IS0 Recommendation R 635 N ovem be r 1967
CODE OF SYMBOLS FOR COVERED ELECTRODES
FOR ARC WELDING OF MILD STEELS
AND LOW ALLOY HIGH TENSILE STEELS
FOREWORD
This IS0 Recommendation is one of a set which also includes the following:
ISO/R 61 5, Methods for Determining the Mechanical Properties of the Weld Metal Deposited
by Electrodes 3.15 mm or more in Diameter,
ISO/R 632, Methods of Test for Determining whether an Electrode is a Deep Penetration
Electrode,
ISO/R . . . ,* Special Method of Mechanical Testing to Determine the Coding for Deep Pene-
'L
tration Electrodes.
INTRODUCTION
This IS0 Recommendation deals with the coding of covered electrodes for the manual arc weld-
.ng of mild steels and low alloy high tensile steels.
1
It should be noted that this Code should be considered only as a guide which may be adopted by
all countries for the purpose of describing electrodes to users, more particularly by means of
symbols. It is in no way designed to be a specification intended to furnish guarantees.
In order to avoid complicating the codification, it has been necessary to disregard certain special
conditions existing only in a small number of countries. In spite of these imperfections however,
this codification may be expected to fulfil its purpose, which is to facilitate mutual understanding
among welding people of the various countries.
The codification is divided into three parts.
L
The first part gives a general symbol indicating the scope of the codification. The second part
describes the mechanical properties of the deposited metal, by means of three symbols, and is
intended for the information of designers, authorities, etc. who have to select the strength and
quality required for given welds.
These first two parts give enough information for the indications which should be given in draw-
ings, specifications, etc., while the third part, relating to welding characteristics, is of interest to
welders.
More generally, in some cases, an abbreviated codification can be used, the symbols which are
not used being replaced by crosses, for example.
This codification for covered electrodes should be applied by electrode manufacturers. The
latter are not bound hereby to comply with requests made by users for electrodes designated by
any combination whatever of symbols.
* At present Draft IS0 Recommendation No. 1040.
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ISO/R 635 - 1967 (E)
1. GENERAL SYMBOL FOR ARC WELDING ELECTRODES AND SPECIAL SYMBOL
FOR DEEP PENETRATION ELECTRODES
1.1 General symbol for covered electrodes for arc welding
E (placed at the beginning of the designation)
The letter E is separated from the symbols following it by a dash signifying that the electrode
is for welding a mild steel or a low alloy high tensile steel. The purpose of the letter E is
to establish a difference between the designation of arc welding electrodes and notations
which may be adopted for other processes.
For instance, where the letter E symbol appears on drawings, it will be possible to distin-
guish the designation from those used for gas welding filler wire.
1.2 Special symbol for deep penetration electrodes
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P (placed at the end of the designation)
The expression “deep penetration” is used for designating a type of electrode which, under
the optimum operating conditions stated by the maker, can be used for welding
(a) a close square T joint giving a penetration of not less than 4 mm, as measured along the
joint (Fig. 1, page 5), the gap between the plates not exceeding 0.25 mm and the thickness
d, and/or
of the plates being at least equal to twice the diameter of the electrode core wire
(b) a close square butt joint performed in two runs (one on each side of the joint), the joint
thus obtained presenting no lack of penetration, and the thickness of the plates being at
least equal to twice the diameter of the electrode core wire d plus 2 mm, i.e. 2 d + 2 mm,
with a gap between the plates not exceeding 0.25 mm (Fig. 2, page 5).
2. SYMBOLS RELATIVE TO THE MECHANICAL PROPERTIES OF THE DEPOSITED METAL
2.1 Tests on the deposited metal
In order to make possible a code of symbols based upon comparable figures, the tests on the
deposited metal should be carried out and interpreted under the conditions specified in IS0
Recommendation R 6 15, Methods for Determining the Mechanical Properties of the Weld
Metal Deposited by Electrodes 3.15 mm or more in Diameter.
IS0 Recommendation R 615 specifies that the mechanical tests should be carried out at a
temperature of 20 3 2 “C in temperate climates and 27 5 2 “C in tropical climates. It also
states all the necessary requirements under which the metal should be deposited, and how
the test pieces should be selected.
2.2 Symbolization of results
In selecting a symbol for each of the mechanical properties, the symbol corresponding to
the lowest of the values obtained by testing all sizes of the electrode should be taken from
the Tables given below.
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IÇO/R 635 - 1967 (E)
FIG. 1. - Fillet weld
FIG. 2. - Butt weld
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IÇO/R 635 - 1967 (E)
2.2.1 Tensile strength (minimum)
As the tensile strength of the deposited metal may vary between one diameter and
another of a given electrode it is specified that the highest value of this property should
not exceed the minimum tensile strength indicated by the symbol for that electrode by
more than 10 kgf/mm2 (6.5 tonf/in2).
The type of test piece to be used is a proportional test piece of circular cross-section
conforming to IS0 Recommendation R 82, Tensile Testing of Steel, and with a diameter
of 10 mm.
TABLE 1. - Tensile strength
Symbols Symbols kgf/mm2 kgf/mm2 Ibf/in2 Ibf/in2 tonf/inz tonf/inz
- - - - - -
O* O*
1 1 41 41 58 58 O00 O00 26 26
2 2 44 44 63 63 000 000 28 28
3 3 48 48
69 69 O00 O00 30.5 30.5
4 4 I 52 52 74 74 O00 O00
33 33
5 56 80 80 O00 O00
35.5 35.5
I 5 I 56
6 6 60 85 85 O00 O00 38 38
I I 6o
* The symbol O is used when no minimum value can be given for tensile strength.
2.2.2 Elongation (minimum)
TABLE 2. - Elongation
Symbols
Elongation* %
-
O **
1 14
2 18
3 22
4
26
5
30
* To determine elongation, the original gauge length should be taken as Lo = 5.65 dSo, where So is the
original cross-sectional area of the gauge length, expressed in square millimetres.
** The symbol O is used when no minimum value can be given for elongation.
2.2.3 Impact strength KV (minimum)
The test piece to be used is the type with V-notch complying with IS0 Recommen-
dation R 148, Beam Impact Test (V-notch) for Steel.
TABLE 3. - Impact strength
Symbols Impact strength kgf.n
I
3
6
9
12
15
* The symbol O is used when no minimum value can be given for impact strength.
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ISO/R 635 - 1967 (E)
3. SYMBOLS RELATING TO WELDING CHARACTERISTICS
The third part of the codification comprises three symbols indicating the type of covering, the
welding positions and the conditions of electrical supply.
3.1 Type of covering
The type of covering is symbolized by one of the following letters:
A = Acid
B = Basic
C = Cellulosic
O = Oxidizing
R = 1st rutile type
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T = 2nd rutile type
V = Other types
These designations should be understood as follows :
Covering of the acid type: Symbol A
3.1.1
Electrodes of the acid type have a medium or thick covering and produce an iron oxide/
mangane
...