eniso 3690

EUROPEAN STANDARD

NORME EUROPÉENNE

EUROPÄISCHE NORM

EN ISO 3690

December 2000

ICS 02.016.40

English version

Welding and allied processes - Determination of hydrogencontent in ferritic arc weld metal (ISO 3690:2000)

Soudage et techniques connexes - Détermination de lateneur en hydrogène dans la métal fondu pour le soudage

à l'arc des aciers ferritiques (ISO 3690:2000)

Schweißen und verwandte Prozesse - Bestimmung desdiffusiblen Wasserstoffgehaltes im ferritischen Schweißgut

(ISO/FDIS 3690:2000)

This European Standard was approved by CEN on 15 December 2000.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.

CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATIONC OM ITÉ EUR OP ÉEN DE NOR M ALIS AT IONEUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: rue de Stassart, 36 B-1050 Brussels

© 2000 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.

Ref. No. EN ISO 3690:2000 E

EN ISO 3690:2000

Foreword

The text of the International Standard ISO 3690:2000 has been prepared byTechnical Committee ISO/TC 44 "Welding and allied processes" in collaboration withTechnical Committee CEN/TC 121 "Welding", the secretariat of which is held by DS.

This European Standard shall be given the status of a national standard, either bypublication of an identical text or by endorsement, at the latest by June 2001, andconflicting national standards shall be withdrawn at the latest by June 2001.

According to the CEN/CENELEC Internal Regulations, the national standardsorganizations of the following countries are bound to implement this EuropeanStandard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany,Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain,Sweden, Switzerland and the United Kingdom.

Endorsement notice

The text of the International Standard ISO 3690:2000 was approved by CEN as aEuropean Standard without any modification.

Reference numberISO 3690:2000(E)

© ISO 2000

INTERNATIONALSTANDARD

ISO3690

Second edition2000-12-15

Welding and allied processes —Determination of hydrogen contentin ferritic steel arc weld metal

Soudage et techniques connexes — Détermination de la teneur enhydrogène dans le métal fondu pour le soudage à l'arc des aciersferritiques

ISO 3690:2000(E)

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© ISO 2000

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ii © ISO 2000 – All rights reserved

ISO 3690:2000(E)

© ISO 2000 – All rights reserved iii

Contents Page

Foreword.....................................................................................................................................................................iv

Introduction .................................................................................................................................................................v

1 Scope ..............................................................................................................................................................1

2 Normative reference ......................................................................................................................................1

3 Test procedures.............................................................................................................................................13.1 Production of weld specimens.....................................................................................................................13.2 Welding procedures for the production of weld specimens.....................................................................53.3 Measurement of hydrogen in the test weld...............................................................................................13

Annex A (informative) Older methods of measurement........................................................................................19

Bibliography ..............................................................................................................................................................20

ISO 3690:2000(E)

iv © ISO 2000 – All rights reserved

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISOmember bodies). The work of preparing International Standards is normally carried out through ISO technicalcommittees. Each member body interested in a subject for which a technical committee has been established hasthe right to be represented on that committee. International organizations, governmental and non-governmental, inliaison with ISO, also take part in the work. ISO collaborates closely with the International ElectrotechnicalCommission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.

Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this International Standard may be the subject ofpatent rights. ISO shall not be held responsible for identifying any or all such patent rights.

International Standard ISO 3690 was prepared in collaboration with the International Institute of Welding which hasbeen approved by the ISO Council as an international standardizing body in the field of welding.

This second edition cancels and replaces the first edition (ISO 3690:1977), which has been technically revised.

Annex A of this International Standard is for information only.

ISO 3690:2000(E)

© ISO 2000 – All rights reserved v

Introduction

During welding processes hydrogen is absorbed by the weld pool from the arc atmosphere. During cooling some ofthis hydrogen escapes from the solid bead by diffusion but some also diffuses into the HAZ and parent metal. Theamount which does so depends on several factors such as original amount absorbed, the size of the weld and thetime-temperature conditions of cooling. Other factors being equal, the more hydrogen present in the weld thegreater the risk of cracking. The principal sources of hydrogen in welding are:

� moisture contained in and picked up by electrode coatings and fluxes;

� other hydrogenous materials which may break down in the heat of the arc;

� oil, dirt and grease on the plate surface or trapped in the surface layers of welding wires;

� atmospheric moisture during welding.

Measurements of weld hydrogen level therefore provide the means of deciding the degree to which a given weldingconsumable is introducing hydrogen to the weld pool. They may thus help to categorize the sources of hydrogenand classify different welding consumables. In addition, such measurements provide a starting point for calculatingpreheating temperatures and temperatures of heat treatment to remove hydrogen after welding.

Hydrogen is unlike other elements in ferritic weld metal in that it diffuses rapidly at normal room temperatures andsome of it may be lost before an analysis can be made. This, coupled with the fact that the concentrations to bemeasured are usually at the parts per million level, means that special sampling and analysis procedures areneeded. In order that results be comparable between different laboratories and can be used to develop hydrogencontrol procedures, some international standardization of these sampling and analysis methods is necessary.

It has become clear from work within the International Institute of Welding that the same sampling and analysisprocedure can be used with minor modifications to deal with a number of fusion welding procedures and also forpurposes other than the simple classification of consumables. The purpose of this document is therefore to define astandardized procedure of sampling and analysis of weld metal for the determination of hydrogen. The essentialfeatures of the International Standard provide for the production of a weld specimen in the form of a rapidlyquenched single bead, and the procedure is described in 3.1; 3.2 of this International Standard gives details of theprocedures to be used when different welding processes are under investigation. The specimen obtained in thisway is then compatible with the recommended analytical techniques specified in 3.3.

There are two principal ways in which this International Standard is intended to be used:

a) To provide information on the levels of weld hydrogen arising from the use of consumables in specific states(e.g. wet or dry), or as a result of the use of specific welding parameters (e.g. different current levels). For suchpurposes the method can be applied with a variety of welding parameters and states of consumable, and thesewill be chosen on each occasion in order to provide the specific information sought. It is important however tostate such conditions when results are reported so that misunderstandings can be avoided.

b) To enable consumables to be classified and to assist in quality control. In such cases consumables have to betreated in like manner — i.e. with fixed conditions of drying temperature and time, welding current and so on.

It is understood that mercury is a hazardous substance, and that its use may be restricted in some countries. Itshould be recognized that this International Standard provides a reference method against which all other methodsare to be calibrated. Once a proper calibration of an alternate method against this reference method is established,normal testing can be conducted with the alternate method. Then the reference method need only be used in rareinstances, such as for checking calibration or in cases of dispute.

INTERNATIONAL STANDARD ISO 3690:2000(E)

© ISO 2000 – All rights reserved 1

Welding and allied processes — Determination of hydrogencontent in ferritic steel arc weld metal

1 Scope

This International Standard specifies the sampling and analytical procedure for the determination of diffusible andresidual hydrogen in ferritic weld metal arising from the welding of ferritic steel using arc welding processes withfiller metal. Collection of the hydrogen over mercury is the primary method. Provided that the weld specimen size ismaintained within limits dictated by the size of the test block, variations in welding parameters are permissible inorder to investigate the effect of such variables on the weld hydrogen content. The techniques described in thisInternational Standard constitute a reference method which should be used in cases of dispute.

2 Normative reference

The following normative document contains provisions which, through reference in this text, constitute provisions ofthis International Standard. For dated references, subsequent amendments to, or revisions of, any of thesepublications do not apply. However, parties to agreements based on this International Standard are encouraged toinvestigate the possibility of applying the most recent edition of the normative document indicated below. Forundated references, the latest edition of the normative document referred to applies. Members of ISO and IECmaintain registers of currently valid International Standards.

ISO 14175, Welding consumables — Shielding gases for arc welding and cutting.

3 Test procedures

3.1 Production of weld specimens

3.1.1 Principle

The welding process to be tested is used to deposit a single weld bead which is rapidly quenched andsubsequently stored at �78 °C or lower until required for preparation and analysis.

3.1.2 Welding fixture

A copper welding jig for heat inputs up to 2 kJ/mm, which may be water cooled, is shown in Figure 1. It is designedto promote the proper alignment and clamping of the test piece assembly by means of the single clamping unitwhich is used with a ring spanner or other suitable means. See 3.1.4 for evidence of proper alignment andclamping. A welding jig without water cooling may be used as long as the same dimensions are retained and aslong as the temperature is controlled in the manner described in 3.1.4 below.

The welding jig shown in Figure 2 will allow the production of test welds with a heat input greater than 2 kJ/mm andup to about 3 kJ/mm.

ISO 3690:2000(E)

2 © ISO 2000 – All rights reserved

Dimensions in millimetres

Key

1 Copper block

2 Test piece assembly

3 Copper foil

4 M12 bolt

NOTE Water cooling channels may be used.

a Dimension X u 25 mm.

Figure 1 — Welding fixture and test piece assembly for weld deposits made with heat inputs up to 2 kJ/mm

ISO 3690:2000(E)



Key


2 Water cooling jacket

3 Lever clamp

4 Copper foil is inserted here

A Made of copper

B Made of mild steel

NOTE 1 1 mm copper inserts (not shown) for SA are 300 mm � 45 mm.

NOTE 2 The run-off bead length shall be such that the trailing end of the crater is on the run-off piece but within 25 mm ofthe test piece. See distance X in Figure 1 for clarity.

a 135 mm for submerged arc welding or 85 mm for gas or self-shielded welding.

Figure 2 — Welding fixture and test piece assembly for weld deposits made with heat inputs greater than2 kJ/mm up to 3 kJ/mm

ISO 3690:2000(E)


3.1.3 Test piece assemblies

The test piece assembly shall be prepared from a plain carbon non-rimming steel with a carbon content of not morethan 0,18 % and sulfur content of not more than 0,02 %. The test assembly shall be made according to thedimensions shown in Figure 3, with a tolerance of � 0,25 mm on all dimensions except the length of the run-on andrun-off pieces. The lengths shown in Figure 3 for the run-on and run-off pieces are suggestions only.


Test assembly la = lb lc e t

Figure 1 45 30 15 10

Reference 3.2.2 135 15 30 10Figure 2

Reference 3.2.3 85 15 30 10

A/B Run-on / Run-off test piece.

C Centre test piece.

NOTE The centre test piece has the same dimensions in all the three cases.

Figure 3 — Dimensions of the weld test assembly

All surfaces shall be finished at right angles to ensure good contact between adjacent pieces during the weldingoperation. Each test piece assembly may be finished with one operation on a surface grinder so as to ensure auniform width, or closer dimensional control may be exercised to obtain proper clamping. See 3.1.4 for evidence ofproper clamping.

Prepare three or more sets of test pieces and number them by engraving or stamping the opposite side to that tobe used for welding. Number and degrease each centre test piece in each set. Determine the weight of each centretest piece (m1) to the nearest 0,01 g. Degas the centre test pieces in a vacuum, or dry inert carrier gas, at650 °C � 10 °C for 1 h and cool in a vacuum or inert carrier gas prior to weighing. It is permissible to degas thesteel from which the test piece assembly is made prior to machining operations, in which case it is not necessary todegas the centre piece after machining. It is also permissible to degas in air when this is followed by completeremoval of surface oxide by grit blasting with a clean, dry abrasive. In case of dispute, the run-on and run-off piecesshall also be degassed.

Certain welding processes, such as submerged arc, or those using high current levels, may produce weld beadsincompatible with the dimensions of test piece assembly as shown aligned in Figure 1. In this case, the testassembly shown in Figure 2 shall be used. The centre test piece is the same for both assemblies: it is rotated 90°about a vertical axis. The run-on and run-off pieces shall be compatible with the new cross-section and the lengthincreased to accommodate the longer weld bead. Those welding processes or parameters which necessitate thisalternative test piece assembly are specified in 3.2. For all welding processes the test piece assembly is clamped in

ISO 3690:2000(E)


the welding fixture using annealed copper foil as shown in Figures 1 and 2. The annealed copper foil may be usedto prevent erosion of the fixture. The foil may be annealed repeatedly and quenched in water after each annealing.Oxide scale after annealing is removed by pickling with dilute nitric acid (10 %) followed by washing with distilledwater and drying.

3.1.4 Welding and test piece storage

The temperature of the welding jig before each weld is made shall be ambient or not more than 25 °C aboveambient. If difficulty is caused by condensation of water on the jig and test piece assembly, it will be necessary touse cooling water thermostatically controlled to ambient temperature or as much as 25 °C higher. Using thewelding process as specified in 3.2, and parameters appropriate to the type of investigation, make a single weldbead on the test piece assembly that is clamped in the welding jig as shown in Figure 1 or Figure 2.

a) Welding shall be initiated on the run-on piece at a point sufficiently distant from the centre test piece such thata stable arc and a stable deposit shape are achieved before reaching the centre test piece.

b) Welding shall be terminated with the trailing edge of the crater within 25 mm of the centre piece.

c) After extinction of the arc, and without any delay, the clamp shall be released and the test piece assemblyremoved and quenched as rapidly as possible to below room temperature in stirred iced water and thentransferred to a low-temperature bath saturated with solid carbon dioxide, or to liquid nitrogen.

d) Once chilled, the underside of the central test piece shall be examined to assess the uniformity and extent ofheat tinting. Properly aligned and clamped test assemblies shall show parallel and uniform heat tinting of theunderside of the central test piece, and dark oxidation shall not extend to the edges of the underside of thecentral test piece.

e) Slag shall be removed, the run-on and run-off pieces broken off and the centre piece returned to cold storage.The centre pieces may be stored at �78 °C in the solid carbon dioxide bath for a period of up to three days, orat � 196 °C in liquid nitrogen for a number of weeks if necessary, before analysis.

f) For purposes of classifying welding consumables, during welding of the test assembly, the ambient absolutehumidity shall be at least 3 g of water vapour per 1 000 g of dry air. (This corresponds to 20 °C and 20 %relative humidity.) When the absolute humidity, measured using a sling hygrometer or other calibrated device,equals or exceeds this condition, the test shall be acceptable as demonstrating compliance with therequirements of this International Standard provided that the actual test results satisfy the diffusible hydrogenrequirements of the applicable consumable classification standard.

3.1.5 Recording of data

All welding details such as current, voltage, travel speed, filler metal type and composition, etc. shall be recordedon the appropriate weld data sheet as given in 3.2. It is particularly important to record atmospheric temperatureand humidity at the welding station. All these data are reported with the analytical results.

3.2 Welding procedures for the production of weld specimens

The welding process under investigation shall have its operating parameters defined so as to permit the productionof a single weld bead on the test piece assembly described in 3.1.

3.2.1 to 3.2.3 describe the procedures for different welding processes.

ISO 3690:2000(E)


3.2.1 Manual metal arc welding

3.2.1.1 Electrodes

The covered electrode to be tested shall be used in one of the following ways:

a) For the purposes of classification, the electrode and the method of deposition of the weld shall be as specifiedin the standard with which the electrode complies.

b) For the purposes of investigation, the electrode and welding parameters shall be those given in the specificwelding procedure. If no procedure has been given, then a current which is 90 % of the maximum suggestedby the manufacturer shall be used.

When a predrying treatment is specified, the time and temperature specified by the consumable's manufacturershall be used. If a range is given by the manufacturer, e.g. 300 °C to 350 °C, the average shall be used.

Electrodes with cracked or broken coatings shall not be used and electrodes to be tested in the as-receivedcondition shall be taken from a freshly opened undamaged packet. During any drying treatment the electrodes shallnot touch each other or the side of the oven. During any drying operation a calibrated oven shall be used and theelectrodes shall spend the full specified time at the drying temperature. Only electrodes under test shall be placedin the oven during this time. When the drying operation is complete, the electrode shall be cooled to ambienttemperature in a container, e.g., a dried borosilicate glass tube sealed with a rubber bung. The electrode shall beused as soon as possible after it reaches ambient temperature. Any electrodes removed from the drying oven andnot then used shall not be redried and subsequently used for the test.

When electrodes are to be tested in the as-received condition from a hermetically sealed container, the electrodesshall be protected from moisture pickup once the seal is broken, until each can be welded. Some sealed containersare resealable. In such a case, each test electrode can be withdrawn individually and the container resealed whilethe withdrawn electrode is welded. If the container is not resealable, then all of the test electrodes shall bewithdrawn when the seal is broken, and each electrode shall be individually placed in a dried borosilicate glasstube sealed with a rubber bung until the electrode is to be used for test.

3.2.1.2 Making the test welds

A copper fixture, such as that shown in Figure 1, shall be used for the alignment and clamping of the test pieceassembly, which uses a 15 mm � 10 mm � 30 mm length centre test piece.

If the classification standard is silent on this matter, the following shall apply. The classification of coveredelectrodes is carried out using 4 mm diameter electrodes. In this case the welding current shall be 15 A less thanthe maximum or 90 % of the maximum stated by the manufacturer, being controlled within a tolerance of � 10 A.The speed of welding shall be adjusted to produce 4 g � 0,5 g of deposit on the centre test piece, which is usuallyaccomplished by an electrode consumption of between 1,2 cm and 1,3 cm per cm of weld.

Three or more test welds shall be made on different test piece assemblies using a different electrode for each weld.The deposit shall be made, without weaving, along the centre line of the test piece assembly which is usuallyaligned as shown in Figure 1. No burning-off prior to testing shall be allowed. The run-on deposit length shall notexceed 25 mm. The time spent in deposition shall be noted. The trailing end of the crater shall be on the run-offpiece but no further than 25 mm from the central test piece. The unused portion of electrode shall be retained formeasurement. The method of using the welding fixture is described in 3.1.4. When welding is completed, the weldspecimen shall be quenched and may be stored as described in 3.1.4., after which it shall be cleaned and analysedfor hydrogen content as described in 3.3.1.2 to 3.3.1.4.

At the time of welding, due to the influence of atmospheric moisture on the test results, for purposes of classifyingcovered electrodes, the arc length shall be maintained as short as possible consistent with maintaining a steadyarc. For all purposes, the details listed in 3.2.1.3 shall be recorded.

ISO 3690:2000(E)


3.2.1.3 Recording of welding data and results report form

The following report sheet gives full details of all the test variables which pertain to the test results.

Report form (diffusible hydrogen, manual metal arc)

Investigating laboratory: Date:

Investigator's name:

Make of electrode: Batch No.:

Type of electrode: Electrode designation:

Diameter of electrode (mm): Overall length of electrode (mm):

Drying treatment °C for h

Electrode polarity (d.c. �ve, d.c. �ve or a.c.):

Relative humidity (%) and temperature (°C) at the welding station during welding

Approximate evolution temperature: °C

Hydrogen collection time: d; h

Number of test piece: 1 2 3

Voltage, V; a.c. or d.c.:

Current, A: type of meter:

Welding time, s:

Weld length, mm:

Heat input, kJ/mm:

Electrode length used, mm:

Run-on length, mm:

Mass of deposited metal on test piece, g:

Test piece to crater distance, mm:

Diffusible hydrogen 1 2 3 Average

(a) HD, ml/100 g of deposited metal

(b) HF, ppm of fused metal

Other test details not included above:

3.2.2 Submerged arc welding

3.2.2.1 Electrode wire

The diameter of the consumable wire used in the submerged arc welding process is linked to the current used andto the size of the weld bead. In general this is a high current process with consequently large weld beads.Therefore it will usually be necessary to use the welding fixture shown in Figure 2.

ISO 3690:2000(E)


The consumable solid or cored wire to be tested shall be used in one of the following ways:

a) For purposes of classification, the welding parameters shall be the same as those used in the preparation ofthe all-weld-metal test assembly for mechanical property determination, with travel speed adjusted to provide adeposit weight on the centre test piece of 4 g � 0,5 g.

b) For the purposes of investigation, the electrode wire and welding parameters shall be those given in thespecific welding procedure. The use of a solid wire which has been degassed in a vacuum or inert gas at650 °C for 1 h facilitates the investigation of the effect of welding parameters, and type of flux and its dryingprocedure, upon the hydrogen content of the weld.

The arc energy for making the weld is restricted to a maximum of 3 kJ/mm.

3.2.2.2 Flux

When drying is required, the flux shall be dried in one of the following ways:

a) for the purposes of classification, in accordance with the requirements of the standard with which the fluxcomplies;

b) for the purposes of investigation, in accordance with the manufacturer's recommendations.

At least 1 kg of flux is required for three welds. Drying shall be done in an open container placed in a calibrateddrying oven set at the correct temperature. The maximum flux depth shall be 15 mm.

The flux shall spend the full specified time at the drying temperature and other fluxes shall not be placed in theoven during this time. When the drying treatment is complete, the flux shall be cooled to ambient temperature in asealed container, where it shall remain until required for use. Used flux shall not be re-cycled.


A copper fixture, which may be water-cooled, such as that shown in Figure 2, shall be used for the alignment andclamping of the test piece assembly. The spring-loaded lever clamp ensures that the applied pressure is uniformlytight from test to test to ensure good thermal contact.

Water cooling is an essential aid to the rapid through-put of test pieces.

The centre piece remains the same size as described in 3.1, but is aligned with longer run-on and run-off pieces(135 mm) as shown in Figure 2. The preparation, degassing and use of the test piece assembly is described in 3.1.The flux is kept at a predetermined constant depth of 30 mm by levelling off along the top of the copper foil insertsshown in Figure 4. If a different flux depth is specified by the flux manufacturer, then the dimension of the copperfoil shall be modified in order to achieve the specified flux depth. At the end of the copper foil there shall be asuitable piece of copper foil to contain the flux.

Three or more test welds shall be made on different test piece assemblies. The deposit shall be along the centreline of the test piece assembly. The time spent in deposition shall be noted. The trailing end of the crater shall beon the run-off piece but no further than 25 mm from the central test piece. No length for the run-on portion of theweld deposit is specified, but the length shall be sufficient to achieve arc and deposit stability before reaching thecentral test piece. The welding fixture is used as described in 3.1.4.

The range of consumable wire diameters, and therefore the range of currents and welding traverse speeds,enables variations in welding parameters to be made within the maximum heat input of 3 kJ/mm. Generally, thevalues chosen shall be compatible with the welding parameters recommended for a particular wire diameter.

The welding current, polarity, voltage, time, weld length, wire feed and electrode extension (stickout), ambienttemperature and humidity shall also be noted.

After extinction of the arc and without any delay, the test piece assembly shall be released from the fixture and thetest piece quenched, cleaned and stored as described in 3.1.4.

ISO 3690:2000(E)


For all purposes, the details listed in the report form under 3.2.2.4 shall be listed.

Key

1 1 mm copper foil, 40 mm � 300 mm


3 Welding fixture

Figure 4 — Use of copper foil to maintain constant flux depth

ISO 3690:2000(E)



The following report form gives full details of all the test variables which pertain to the test results.

Report form (diffusible hydrogen, submerged arc)



Electrode diameter, mm: Electrode designation:

Make of electrode: Batch No.:

Type of flux:

Flux maker: Batch No.:

Flux drying temperature and time °C for h

Electrode polarity (d.c. �ve, d.c. �ve or a.c.):

Relative humidity (%) and temperature (°C) at the welding station during welding






Welding time, s:

Weld length, mm:

Welding speed, mm/s:

Heat input, kJ/mm:

Wire feed speed, mm/s:

Electrode extension, mm:







ISO 3690:2000(E)


3.2.3 Tubular cored electrode with or without gas shield and wire electrode with gas shield

3.2.3.1 Filler material

The filler material to be tested shall be used in one of the following ways:

a) For purposes of classification, the welding parameters shall be the same as those used in the preparation ofthe all-weld-metal test assembly for mechanical property determination, with travel speed adjusted to obtain adeposit weight on the centre test piece of 4 g � 0,5 g. It is well established that diffusible hydrogen results fromtubular cored electrodes are strongly affected by the electrode extension. Care shall be taken that theelectrode extension used for the diffusible hydrogen test is the same as that used in preparing the all-weld-metal test coupon for mechanical property determination.

b) For investigation purposes, the filler material and welding parameters shall be those given in the specificwelding procedure. If a current range is given by the manufacturer, then the average shall be used.

When an unused reel of filler material is being tested, the complete outer layer shall be discarded.

3.2.3.2 Shielding gas

The shielding gas shall be of a welding grade as specified in ISO 14175. The shielding gas used and gas flow shallbe according to the manufacturer's recommendations. Details of the shielding gas composition and flow shall berecorded on the report form. For investigation purposes it may sometimes be necessary to dry the shielding gas inorder to remove moisture. If this is done, then the moisture content of the gas shall be measured and reported.


For heat inputs up to 2 kJ/mm, a copper fixture such as shown in Figure 1 shall be used for the alignment andclamping of the test piece assembly. For heat inputs greater than 2 kJ/mm up to 3 kJ/mm, a water-cooled copperfixture such as shown in Figure 2 shall be used. The spring-loaded lever clamp ensures that the applied pressure isuniformly tight from test to test to ensure good thermal contact.

The copper fixture shown in Figure 1 may incorporate water cooling channels in order to achieve a faster through-put of test pieces.

The run-on and run-off pieces of the test piece assemblies may be 45 mm long when using the assembly shown inFigure 1, and 85 mm long when using the assembly shown in Figure 2. The welding parameters shall be chosen toensure that the heat input for the fixture in use is not exceeded.

Using the welding fixture appropriate to the heat input, the test piece assembly shall be clamped in the fixture usingannealed copper foil as shown.

Three or more test welds shall be made on different test piece assemblies. The deposit shall be along the centreline of the test piece assembly. The time spent in deposition shall be noted. The trailing end of the crater shall beon the run-off piece but no further than 25 mm from the central test piece. No length for the run-on portion of theweld deposit is specified, but the length shall be sufficient to achieve arc and deposit stability before reaching thecentral test piece. The welding fixture is used as described in 3.1.4.

The welding current, polarity, voltage, time, weld length, electrode extension, wire feed speed and gas flow andambient temperature and humidity at the welding station shall be noted for each of the triplicate welds andrecorded on the report form.

After extinction of the arc and without any delay, the test piece assembly shall be released from the fixture and thetest piece quenched, cleaned and stored as described in 3.1.4.

For all purposes, the details listed in the report form under 3.2.3.4 shall be recorded.

ISO 3690:2000(E)



The following report form gives full details of all the test variables which pertain to the test results.

Report form (diffusible hydrogen, MIG, MAG, TIG, or cored electrode)



Type of filler material: Shielding gas: Drying treatment:

Filler material designation: Gas cup i.d., mm:

Diameter of filler material, mm: Shielding gas flow, I/min:

Electrode polarity (d.c. �ve, d.c. �ve or a.c.): Details of tungsten electrode, if any

Make:

Diameter, mm:

Cone angle:

Relative humidity (%) and temperature (°C)at the welding station during welding

Designation:






Welding time, s:

Weld length, mm:

Welding speed, mm/s:

Heat input, kJ/mm:

Wire feed speed, mm/s:

Electrode extension, mm:







ISO 3690:2000(E)


3.3 Measurement of hydrogen in the test weld

3.3.1 Primary method: collection over mercury

The gas collection apparatus described in this section is known as a Y-tube and mercury shall be used as thecollecting fluid. Other designs of collecting apparatus may be used, provided the same principles as for the Y-tubeare used.

3.3.1.1 Preparation of gas burette (Y-tube)

The volume of mercury required to fill the size of gas burette illustrated in Figure 5 is about 110 ml. It is essentialthat the mercury be free of contaminants. The mercury shall be poured into the wide limb of the gas burette, thetwo-way vacuum stopcock shall be fitted and vacuum applied. Air shall be removed by laying the gas burette on aflat surface so as to allow an unrestricted application of the vacuum to the top of the capillary tube. The gas buretteshall be slowly raised to the vertical position and air admitted to the wide limb by rotating the stopcock. Ensure thatthere is no air bubble at the top of the capillary tube. If air is present, then the evacuation process shall be repeateduntil a final check confirms the absence of air. The vacuum stopcock shall be removed from the wide limb of thegas burette.


a) Two-way glass vacuum stopcock b) Side view of bent arm 3 in c)

Key

1 29/32 socket

2 29/32 cone

3 Arm bent up 45° [see b)]

4 Seal (flat inside)

5 Precision bore tube, i.d. 4 mm

NOTE Not to scale.

a To air.b To vacuum.c Inside diameter (23 mm to 25 mm).d Straight portion before bend.

c) Overall view of 'Y' tube

Figure 5 — Diffusible hydrogen collecting apparatus, 'Y' tube

ISO 3690:2000(E)


3.3.1.2 Test piece cleaning

The central test piece shall be cleaned by thorough brushing to remove all slag and oxide using a steel wire brush,in good condition, with intermittent periods of cooling. The intervals spent outside the cooling bath during thisoperation shall not exceed 15 s.

3.3.1.3 Test piece handling

The test piece shall be removed from the storage coolant and raised to room temperature. This can beconveniently achieved by immersing the test piece in water until the ice begins to melt.

The following part of the procedure shall be carried out as quickly as possible, taking not more than approximately2 min.

Following a rinse with acetone and drying in a jet of air, transfer the test piece to the wide limb of the burette. Closethis with the two-way vacuum stopcock and evacuate. Acetone and traces of condensed water evaporate from thesurface of the test piece and are removed with the evacuated air. Using a magnet, manœuvre the test piece intoposition under the capillary tube by carefully lowering the burette towards the horizontal position until it just floatsalong the mercury surface. It is essential that care be taken to prevent air entering the capillary tube when theburette is raised to the vertical position and air is admitted to the wide limb. Remove the two-way stopcock andclose the wide limb by means of, e.g., a cork or a glass cap, to prevent the release of traces of mercury vapour.

Diffusible hydrogen is evolved from the test piece and collects in the capillary tube.

WARNING — Mercury vapour is emitted from open mercury surfaces at room temperature. Therefore,accidental spillage should be removed. Glassware containing mercury can be handled safely on a benchwith a raised edge in a well-ventilated area.

3.3.1.4 Analytical procedure

Maintain the test piece at 25 °C � 5 �C, until there is no increase in calculated hydrogen volume (corrected to STP)on successive days. "No increase" can be understood as allowing for a change, over 24 h, of no more than 1 % ofthe total volume collected. See annex A. Measure the length of the hydrogen gas column and the head of mercuryusing a cathetometer. Measure and record room temperature and barometric pressure. The volume of hydrogencollected, corrected to standard temperature and pressure, is given by the following equation:

P H r CV

T

2273 ( ) ( )760 (273 + ) 1 000

� � ��

�

where

V is the volume of hydrogen collected in millilitres at STP;

P is the barometric pressure in millimetres of mercury;

H is the differential head of mercury between the two limbs of the Y-tube in millimetres;

C is the length of the gas column above the mercury in millimetres;

r is the radius of the capillary tube in millimetres;

T is room temperature at the time of hydrogen measurement in degrees celsius.

When evolution has ceased, remove the test piece from the apparatus and determine, to the nearest 10 mg, itsfinal weight m2 in grams. Record all the relevant data.

ISO 3690:2000(E)


3.3.1.5 Calculation and expression of results

3.3.1.5.1 Diffusible hydrogen in deposited metal HD

Calculate the volume HD at STP of diffusible hydrogen per 100 g of deposited metal from the following equation:

D2 1

100( )

H Vm m

� �

�

in ml per 100 g of deposited metal.

3.3.1.5.2 Diffusible hydrogen in fused weld metal HF

If the hydrogen content is required in terms of concentration in the fused metal, it is necessary to measure thecross-sectional area of the fused metal and of the deposited metal. These shall be measured on the ends of thetest piece by using an enlarged tracing or photograph, or an image-analysing microscope, and then averaging theresults. Diffusible hydrogen in the fused weld is calculated as shown by the following equation:

F DAverage area of deposited metal

0,9Average area of fused metal

H H� � �

in parts per million by mass.

3.3.1.5.3 Reporting of results

All data which can be relevant to the interpretation of results shall be reported on the report form under 3.3.1.6. Forthe purposes of this International Standard, the average value of the hydrogen concentration of triplicate weldsshall be reported to one decimal place.

The report forms given in 3.2 of this International Standard are used to report details of the welding consumable,the welding parameters and test conditions for each set of triplicate welds. The results of the hydrogenmeasurements shall be recorded on the same forms.

ISO 3690:2000(E)


3.3.1.6 Analysis data sheet

All data required for the calculation of the diffusible hydrogen shall be recorded as follows:

Date:

Hydrogen collection temperature: °C


Barometric pressure (recorded during measurement) (P): mm Hg

Room temperature (recorded during measurement) (T): °C

Radius of capillary: mm


Mass of centre test piece (m1), g:

Mass of centre test piece plus weld (m2), g:

Mass of deposited metal (m2 � m1), g:

Average area of deposited metal, mm2:

Average area of fused metal, mm2:

Length of hydrogen gas column (C), mm:

Head of mercury in capillary (H), mm:

3.3.2 Rapid methods for the measurement of diffusible hydrogen in ferritic arc weld metal

The primary method for the measurement of diffusible hydrogen in ferritic arc weld metal is based upon collectionand measurement, over mercury, of the hydrogen evolved from a standard-sized weld sample. The evolution takesplace at room temperature and consequently the collection time is typically about 14 d. This time scale isacceptable in a primary method, but when results are required for purposes such as quality control, or release of aconsumable for sale, then more rapid techniques of measurement are required.

In order to reduce the hydrogen evolution time, it is necessary to heat the weld sample, and the mercury methodimposes a significant health hazard above 45 �C. The heating temperature will determine the time taken forcomplete evolution to occur; e.g., a temperature of 45 �C is said to enable analysis to be carried out in 3 d, oralternatively at 150 �C in 6 h, even for test pieces somewhat larger than those of the primary method. The higherthe temperature, the quicker the evolution. The choice of temperature is important because above about 400 °Cthere will be significant dissociation and release of hydrogen which, at room temperature, would remain in themolecular state and other compound forms and be permanently trapped in voids in the weld metal. At 650 °Canalysis for total hydrogen, which includes residual hydrogen not measured by this reference method, can beachieved within 30 min. The condition of the sample surface has a marked effect upon the measured hydrogenvolume when methods involving heating above about 500 �C are used.

It is not the objective of this subclause to describe the several alternative methods which are available for themeasurement of hydrogen in metals. However, it is important to note that any alternative method incorporating thefacility for measuring diffusible hydrogen in weld metal has to provide a proper correlation, in terms of accuracy andreproducibility, with room temperature diffusible hydrogen results obtained using the primary method presented in3.3.1.

When evaluating the suitability of an alternative method for the measurement of diffusible hydrogen in test welds, itis essential that the following factors be examined.

ISO 3690:2000(E)


3.3.2.1 Calibration

Calibration of analytical instruments is normally achieved by using certified reference materials to quantifyinstrument responses. Further, it is normal to check calibrations by performing regular analyses of referencematerials or secondary standards. In the case of hydrogen, such reference materials and secondary standards arenot available because of the transitory mode of occurrence of hydrogen at, or above, room temperature. Calibrationby injection of pure hydrogen is, in practice, not always the primary method it appears to be. This is because of thedifficulty of reproducing the characteristics of hydrogen evolution from a weld sample with the dynamic gas flowsystems of the instrumental methods.

Because standard samples are not available, calibration shall be by injection of a known volume of hydrogen intothe carrier gas system over the operating range of interest.

The instrument shall first be set up according to the manufacturer's instructions and left to stabilize for a sufficientperiod of time with the carrier gas flowing. This period could be up to 2 h. Calibration is then performed by injectinghydrogen volumes ranging from 0,05 ml to 0,95 ml, equivalent to about 30 ml at STP per 100 g for a typical manualmetal arc deposit mass of approximately 3,5 g. For weld deposits giving volumes of hydrogen beyond this rangethe calibration shall be extended accordingly.

During normal instrument use, any existing calibration shall be checked by gas dosing before analysis is attempted.The instrument preparation procedure shall also be adhered to. Checks shall be made at hourly intervals during aseries of analyses in order to ensure that no drift has occurred in the instrument calibration.

3.3.2.2 Linearity

The linearity of response of the instrument may be judged by using linear regression analysis to fit the calibrationdata and then calculating the correlation coefficient R. Values of R close to unity indicate a high degree ofcorrelation.

The range of hydrogen contents to be measured will range from 0,05 ml to over 1 ml at STP.

Hydrogen injection shall cover this range in order to confirm linearity of response, but tests with weld specimensshall be carried out to confirm that the hydrogen evolution characteristics of the sample are followed by theinstrument in a linear fashion.

3.3.2.3 Accuracy

There are no primary standards available which will release diffusible hydrogen at temperatures below 150 �C. Theonly way in which accuracy may be assessed is by a statistical comparison of a series of nominally identical testwelds, divided into two groups in a random fashion, the first group being analysed by the alternative method whilstthe second group is analysed by the primary method.

The accuracy of the alternative method shall be determined at several levels of hydrogen content. These shallinclude the 5 ml, 10 ml and 15 ml at STP per 100 g deposited weld metal hydrogen levels. A further check at the25 ml level should be done in order to cover the analysis of non-hydrogen controlled consumables.

It is recommended that nine repeat determinations be carried out using both the rapid method and the primarymethod described in 3.3.1. The accuracy of the rapid method is then judged by assessing the statisticalsignificance of the difference in means of the two sets of results. If the probability of the difference not due tochance is greater than 95 %, then the difference in means is probably significant. The most common statistic to usewhen comparing means is the t value defined as:

Difference of meansStandard of difference

t �

ISO 3690:2000(E)


The following equation may be used to calculate t:

� �R P

2 2R P

R P

x xt

s s

n n

�

�

�

where xR, sR and nR are respectively the mean, standard deviation and number of test pieces for the rapid methodand xP, sP and nP are respectively the mean, standard deviation and number of test pieces for the primary method.

The t value so obtained is applied to tables of statistics where, for the number of degrees of freedom involved(nP + nR – 2), the probability of this value having arisen by chance will be given. If the difference in means is judgedto have arisen by chance, then the two methods may be assumed to give identical results.

3.3.2.4 Reproducibility

A series of repeat welds, analysed as indicated for the test on accuracy, will also provide information on thereproducibility of the alternative method.

Reproducibility is the consistency of replicate tests and is expressed by the standard deviation s. A reproducibilityindex, 2s, may be defined and in statistical terms 95 % of results would lie within a band x � 2s where x is the meanvalue. A decrease in the numerical value of s implies an increase in reproducibility.

Reproducibility of a method is best determined using a planned trial in which analysts from several laboratories areinvolved in order to characterize the within-operator and between-operator components of the standard deviationgiven by the following equation:

2 2b ws s s� �

where

sb is the between-operator standard deviation;

sw is the within-operator standard deviation.

The standard deviation of the nine results of each of the control levels mentioned under 3.3.2.3 gives values of swfor both the rapid and primary methods.

3.3.2.5 Blank

A blank shall be carried out to determine the alternative method response to a standard-sized degassed specimen.This operation is advisable on a regular basis in order to confirm proper functioning of the instrument. It should benoted that the instrument response, as shown by the increments of the readout, has an influence upon both theaccuracy and the reproducibility; e.g., for a 4 g deposit weight, a readout of 0,01 ml at STP represents 0,25 ml H2per 100 g of deposited weld, or about 0,11 ppm of fused weld.

ISO 3690:2000(E)


Annex A(informative)

Older methods of measurement

Older practices of hydrogen evolution for 72 h at approximately 20 �C, using the smaller central test piece size of7,5 mm � 10 mm � 15 mm, are likely to result in appreciably less than complete hydrogen evolution, unlesscleaning after welding is perfect. 67 % to 80 % of the total diffusible hydrogen may be collected. Therefore,consumables tested in accordance this International Standard may be given a higher hydrogen classification thanthey would have been given under, e.g., ISO 3690:1977 or DIN 8572-1, without any change in the real product.With the larger central test piece of this International Standard, a still lower percentage of the total diffusiblehydrogen could be expected after 72 h of hydrogen evolution.

ISO 3690:2000(E)


Bibliography

[1] ISO 630, Structural steels — Plates, wide flats, bars, sections and profiles.

[2] ISO 2560, Covered electrodes for manual arc welding of mild steel and low alloy steel — Code of symbolsfor identification.

[3] DIN 8572-1, Determination of diffusible hydrogen in weld metal; manual arc welding.

[4] Doc.IIS/IIW-452.74, Weld hydrogen levels and the definition of hydrogen controlled electrodes. Welding inthe World, 1974, Vol. 12, No.3/4, p.69.

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