FCAW MEANING CODE

FCAW MEANING CODE

The Structural Welding Code – Steel (AWS D1.1-2000)5 has provisions related to hydrogen in the preheat table (Table 2). Some codes and specifications refer to hydrogen control in terms of either (1) requiring low hydrogen SMAW electrodes or (2) placing specific limits on diffusible hydrogen. Use of the Term in Codes and Specifications For example, the E6010 classification (non-low hydrogen, 30-50 mL/100g) has a minimum CVN requirement of 20 ft-lbs at minus 20☏. Actually, some deposits with high hydrogen levels can deliver relatively high levels of notch toughness. The better approach is to specify notch toughness requirements since there is no automatic link between low diffusible hydrogen content in the weld and CVN values. This has led some people to specify low hydrogen when the real desire is for notch toughness.

Since low hydrogen SMAW electrodes like E7018 are also required to have a minimum specified level of Charpy V-notch (CVN) impact energy, low hydrogen is sometimes equated with a minimum CVN level. It is only in severe cases that it can influence the ultimate tensile strength. Hydrogen, however, does not typically influence the impact toughness, ultimate tensile strength or yield strength results. A high hydrogen content in a tensile specimen can produce 'fish-eyes' on the fracture surface as seen in Figure 1.Īdditionally, the presence of hydrogen can reduce ductility (as expressed by elongation and reduction in area). The influence of hydrogen can be observed in mechanical testing however, its effects on the test results are limited. 'Fish-eyes' on an all-weld-metal tensile specimen fracture surface.Ĭan Hydrogen Affect Mechanical Properties? Table 1 lists the SMAW electrodes with low hydrogen coating contained in A5.1.įigure 1. Many of today’s E7018 products have actual coating moisture content levels much lower than the maximum of 0.6% in the as-received condition.

For example, AWS A4.3, Standard Methods for Determination of Diffusible Hydrogen4, shows that when E7018 is welded at 70 ☏ and 60% relative humidity a 0.6% coating moisture equates to approximately 12 mL/100g of diffusible hydrogen. This moisture level corresponds to a relatively low diffusible hydrogen level in the deposited weld metal, typically less than 16 mL/100g. These classifications must have a coating moisture level of less than 0.6% when tested at 1800 ☏ (980 ☌), according to AWS A5.1. This specification lists several electrode classifications with 'low hydrogen' coatings. The closest thing to a formal definition for low hydrogen SMAW electrodes is found in the AWS A5.1 filler metal specification3. 'Low Hydrogen Electrode' Means SMAW Electrode This may come as a surprise to some, especially to engineers that have been specifying that 'only low hydrogen electrodes shall be permitted,' or 'all welds shall be low hydrogen', or that 'all welding processes shall be low hydrogen.' Without a formal definition, the term 'low hydrogen' can be understood differently by engineers, contractors, or inspectors, which can lead to confusion and conflicts. Many codes and specifications use the designation, however, neither 'low hydrogen' nor 'low hydrogen electrodes' are listed in the American Welding Society’s (AWS) Standard Welding Terms & Definitions (AWS A3.0-94)2. They were created to avoid hydrogen cracking on high strength steels, such as armor plate.Īlthough so-called 'low hydrogen electrodes' have been around for many years, there is some confusion about what is meant by the term.

It was first introduced to differentiate this classification of shielded metal arc welding (SMAW) electrode (e.g., E7018) from other non-low hydrogen SMAW electrodes (e.g., E6010). The term 'low hydrogen' has been around for about 60 years. This article will address specifying filler metals that resist hydrogen related cracking while also providing good mechanical properties. While this may be true, it can not be assumed. In some cases the engineer may specify low hydrogen electrodes because he believes these electrodes will also provide weld deposits exhibiting a high minimum level of notch toughness.

When selecting filler metals, the specifier may elect to require 'low hydrogen electrodes.' Such electrodes may be required to minimize the possibility of hydrogen related cracking.

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