CLASSIFICATION

CHARACTERISTICS & APPLICATIONS

ísaw-XXXX+ísol-XXX series of low, medium & high manganese flux-wire combinations are designed for use on carbon steel, however in addition to their use on carbon steel, these are also used for joints involving normal-strength and medium steels. The combinations are ideally suitable for fillet joints, butt joints and square-butt joints to put sound joints when used with single and/or multi-run technique at optimum parameters with inter-pass temperature and cleaning. Irrespective of the grade of steel, switching-over to flux with higher basicity is recommended above 20 mm thickness or utmost precautions need to be taken to obtain defect-free weld. The fillet welds made in flat welding position have a slightly convex to flat weld face, with a smooth and finely rippled surface. The electrodes are characterized by a smooth, quiet hidden arc and shallow, medium, or deep penetration depending upon type of combination and usage parameters. The electrodes can be used at higher travel speeds with appropriate high-speed versions of flux.

The electrodes covered herein are carbon steel electrodes which vary from one another in their carbon, manganese, and silicon contents. An electrode from this group is selected for use with a particular flux to provide the best combination of these elements to meet application requirements. These requirements can include (but are not limited to) resistance to cracking and porosity, welding characteristics, welding speed, bead appearance, and weld metal mechanical properties.

Fluxes in neutral, active, alloy, high speed & tailor-made proprietary versions are also available.

Chemical Composition Requirements for Solid Electrodes

Chemical Composition Requirements for Solid Electrodes

Single values are maximum.

The copper limit includes any copper coating that may be applied to the electrode.

Tension Test

X = “A” for as welded and “P” for post weld heat treated.

The temperature shall be raised at the rate of 85°C to 280°C per hour until the post weld heat treatment temperature of 620°C ± 15°C is attained. This temperature shall be maintained for one hour (–0, +15 minutes).

The test assembly shall then be allowed to cool in the furnace at a rate not greater than 200°C per hour. After the test assembly has reached 315°C it may be removed from the furnace and allowed to cool in still air.

Impact Test

Diffusible Hydrogen (Optional supplemental diffusible hydrogen designator)

Diffusible Hydrogen (HD) FXXXX–EXXX–HX

Hydrogen-induced cracking of weld metal or the heat-affected zone is not generally a problem with carbon steels containing 0.3% or less carbon, or with lower-strength alloy steels. However, the fluxes and electrodes classified in this specification are sometimes used to join higher carbon steels or low-alloy, high-strength steels where hydrogen-induced cracking may be a serious problem.

Submerged arc welding is generally considered to be a low-hydrogen welding process. As the weld metal or heat affected zone strength or hardness increases, the concentration of diffusible hydrogen that will cause cracking under given conditions of restraint and heat input becomes lower.

This cracking (or its detection) is usually delayed some hours after cooling. It may appear as transverse weld cracks, longitudinal cracks (especially in the root beads), and toe or under-bead cracks in the heat-affected zone.

Since the available diffusible hydrogen level strongly influences the tendency towards hydrogen-induced cracking, it may be desirable to measure the diffusible hydrogen content resulting from welding with a particular flux-electrode combination.

Storage & Drying

Flux in its original unopened container shall withstand storage under normal conditions for at least six months without damage to its welding characteristics or the properties of the weld. Heating of the flux to assure dryness may be necessary when the very best properties (of which the materials are capable) are required. For specific recommendations, consult METAFIL.

Holding Ovens: 30°-140°C above ambient temperature.

Drying Conditions: 260°C-425°C for 1-2 hours prior to use.

Flux of any specific trade designation may have many classifications. The number is limited only by the number of different electrode classifications and the condition of heat treatment (as welded and post weld heat treated) with which the flux can meet the classification requirements. The flux marking lists at least one, and may list all, classifications to which the flux conforms. It should also be noted that the specific usability or operating characteristics of the various fluxes of the same classification often differ in one respect or another.

Solid electrodes having the same classification are generally interchangeable when used with a specific flux.

Types of Flux

Submerged arc welding fluxes are granular, fusible mineral compounds of various proportions and quantities, manufactured by any of several different methods. Some fluxes may contain intimately mixed metallic ingredients to deoxidize the weld pool. Any flux is likely to produce weld metal of somewhat different composition from that of the electrode used with it due to chemical reactions in the arc and sometimes to the presence of metallic ingredients in the flux. A change in the arc voltage during welding will change the quantity of flux interacting with a given quantity of electrode and may therefore change the composition of the weld metal. This latter change provides a means of describing fluxes as “neutral,” “active,” or “alloy.”

Neutral Fluxes:Neutral fluxes are those which will not produce any significant change in the weld metal chemical analysis as a result of a large change in the arc voltage and thus, the amount of flux melted. The primary use for neutral fluxes is in multipass welding, especially when the base metal exceeds 25mm in thickness. Note the following considerations concerning neutral fluxes:

1. Since neutral fluxes contain little or no deoxidizers, they must rely on the electrode to provide deoxidation. Single-pass welds with insufficient deoxidation on heavily oxidized base metal may be prone to porosity, centerline cracking, or both.
2. While neutral fluxes maintain the chemical composition of the weld metal even when the voltage is changed, the chemical composition of the weld metal may not be the same as that of the electrode. Some neutral fluxes decompose in the heat of the arc and release oxygen, resulting in a lower carbon value in the weld metal than the carbon content of the electrode itself. Some neutral fluxes contain compounds with manganese and silicon, which can decompose in the heat of the arc and add manganese and silicon to the weld metal even though no metallic manganese or silicon was added to these fluxes. These changes in the chemical composition of the weld metal are consistent, even when there are large changes in voltage.
3. Even when a neutral flux is used to maintain the weld metal chemical composition through a range of welding voltages, weld metal properties such as strength level and impact properties can change because of changes in other welding parameters such as depth of fusion, heat input, and number of passes.

Active Fluxes Active fluxes are those which contain small amounts of manganese, silicon, or both. These deoxidizers are added to the flux to provide improved resistance to porosity and weld cracking caused by contaminants on or in the base metal. The primary use for active fluxes is to make single-pass welds, especially on oxidized base metal. Note the following considerations concerning active fluxes:

1. Since active fluxes do contain some deoxidizers, the manganese, silicon, or both in the weld metal will vary with changes in arc voltage. An increase in manganese or silicon will increase the strength and hardness of the weld metal in multipass welds but may lower the impact properties. For this reason, the voltage may need to be more tightly controlled for multipass welds with active fluxes than when using neutral fluxes.
2. Some fluxes are more active than others. This means they offer more resistance to porosity due to base metal surface oxides in single pass welds than a flux which is less active but may pose more problems in multipass welding.

Alloy Fluxes: Alloy fluxes are those which can be used with a carbon steel electrode to make alloy weld metal. The alloys for the weld metal are added as ingredients in the flux. As with active fluxes, where the recovery of manganese and silicon is affected significantly by arc voltage, so with alloy fluxes, the recovery of alloy elements from the flux is affected significantly by the arc voltage. With alloy fluxes, the METAFIL’s recommendations should be closely followed if desired weld metal compositions are to be obtained. The use of crushed slags generated from alloy flux is not recommended.

Choice of Electrodes: n choosing an electrode classification for submerged arc welding of carbon steel, the most important considerations are the manganese and silicon contents of the electrode, the effect of the flux on recovery of manganese and silicon in the weld metal, whether the weld is to be single pass or multiple pass, and the mechanical properties expected of the weld metal.

Certain minimum weld metal manganese content is necessary to avoid centerline cracking. This minimum depends upon restraint of the joint and upon the weld metal composition. If centerline cracking is encountered, especially with a low manganese electrode and neutral flux, a change to a higher manganese electrode, a change to a more active flux, or both, may eliminate the problem. Certain fluxes, generally considered to be neutral, tend to remove carbon and manganese to a limited extent and to replace these elements with silicon. With such fluxes, a silicon-killed electrode is often not necessary though it may be used.

Other fluxes add no silicon and may therefore require the use of a silicon-killed electrode for proper wetting and freedom from porosity.

METAFIL may be consulted for electrode recommendations suitable for a given flux. When welding single-pass fillet welds, especially on base metal with mill scale, it is important that the flux, electrode, or both, provide sufficient deoxidation to avoid unacceptable porosity. Silicon is a more powerful deoxidizer than manganese.

In such applications, use of a silicon-killed electrode or of an active flux, or both may be essential. Again, METAFIL’s recommendations should be consulted.

The “G” indicates that the electrode is of a general classification. It is general because not all the requirements specified for each of the other classifications are specified for this classification. The intent, in establishing this classification is to provide a means by which electrodes that differ in one respect or another (chemical composition, for example) from all other classifications (meaning that the composition of the electrode, in the case of the example, does not meet the composition specified for any of the classifications in the specification) can still be classified according to the specification. The purpose is to allow a useful electrode, one that otherwise would have to wait for a revision of the specification, to be classified immediately under the existing specification. This means that two electrodes, each bearing the same “G” classification, may be quite different (chemical composition, for example).

Mechanical Properties

The mechanical properties of a weld are the function of its chemical composition, cooling rate, and PWHT. High amperage, single-pass welds have a greater depth of fusion and hence, greater dilution by the base metal than lower current, multi-pass welds. Large, single-pass welds solidify and cool more slowly than the smaller weld beads of a multipass weld, and succeeding passes of a multi-pass weld subject the weld metal of previous passes to a variety of temperature and cooling cycles that alter the metallurgical structure of different portions of those beads. For these reasons, the properties of a single-pass weld may be different than those of a multi-pass weld made with the same electrode and flux.

The weld metal properties are determined in either the as-welded condition or after a PWHT, or both. For multiple pass classifications tested in the post weld heat treated condition (“P” designator) the PWHT procedure is one hour at 620°C. Most of the weld metals are suitable for service in either condition, but the specification cannot cover all of the conditions that such weld metal may encounter in fabrication or service. Hence, this combination requires that the weld metals be produced and tested under specific conditions.

Procedures employed in practice may require voltage, amperage, type of current, and travel speeds that are considerably different from those specified herein. In addition, differences encountered in electrode size, electrode composition, electrode extension, joint configuration, preheat temperature, interpass temperature, and PWHT can have a significant effect on the properties of the weld. Within a particular electrode classification, the electrode composition can vary sufficiently to produce variations in the mechanical properties of the weld deposit in both the as welded and PWHT conditions. PWHT times in excess of the one hour used for classification purposes in this specification may have a major influence on the strength and toughness of the weld metal. The strength can be substantially reduced, and the toughness increased or reduced. The user should be aware of this and should understand that the mechanical properties of carbon steel weld metal produced with other procedures than those required in this specification may differ from the properties required.

Flux Storage and Drying Conditions: Hydrogen can have adverse effects on welds in some steels under certain conditions. One source of this hydrogen is fluxes in general and base materials in particular whose entrapped gases, flaws and imperfections are likely to make ways through weld joints in the form of weld defects like centerline cracks, transverse cracks, porosities and so on. For this reason, proper storage, reconditioning, and usage of flux in as-hot condition are necessary.

Fluxes and electrodes can be contaminated by the condensation of moisture from the atmosphere and in some cases can absorb significant moisture if stored in a humid environment in damaged or open packages, especially if unprotected for long periods of time.

In extreme cases of high humidity, even overnight exposure of unprotected flux or electrode can lead to a significant increase of diffusible hydrogen. In the event the flux or electrode has been exposed, the manufacturer should be consulted regarding probable damage to its low hydrogen characteristics and possible reconditioning of the flux or electrode. Solid electrodes can also be contaminated under the same conditions. In this case, the moisture contamination is on the surface and can be seen as surface rust.

WELDING PARAMETERS (AC or DCEN or DCEP)

E-EXT= Electrode Extension

TS = Travel Speed

WARNING: Safety and health information is available from many sources, including, but not limited to Safety and Health Fact Sheets listed in A11.3, ANSI Z49.1 Safety in Welding, Cutting, and Allied Processes published by the American Welding Society, 8669 Doral Blvd., Suite 130, Doral, FL 33166., and applicable federal and state regulations. The Safety and Health Fact Sheets are revised, and additional sheets added periodically.