Lesson 3 - Covered Electrodes for Welding Mild Steels

3.3.1 Chemical Composition of Weld Metal (AWS A5.1-91) - Chemical requirements are as follows: a) Classifications E6010, E6011, E6012, E6013, E6020, E6022 and E6027 have no requirements. b) Classification E7018 and E7027 must have no more than 1.60% Manga- nese, 0.75% Silicon, 0.30% Nickel, 0.20% Chromium, 0.30% Molybde- num, and 0.08% Vanadium. c) Classifications E7014, E7015, E7016, E7024, E7028 and E7048 must have no more than 1.25% Manganese, 0.90% Silicon, 0.30% Nickel, 0.20% Chromium, 0.30% Molybdenum, and 0.08% Vanadium. 3.3.2 Mechanical Properties (AWS A5.1-91) - Physical tests are performed on all specimens in the "as-welded" condition. This means that the weldment or weld metal is not subjected to any type of heat treatment. Tensile test specimens for all electrode classifications other than the low hydrogen types (E7015, E7016, E7018, E7028 and E7048) are aged at 200°F to 220°F for forty-eight (48) hours prior to being subjected to the tensile test. This is not considered heat treatment. It simply accelerates the diffusion of hydrogen from the weld metal welded with the cellulosic or titania type of electrodes. EXAMPLE: E 60 1 0 (1) (2) (3) (4) 1. E — Stands for electrode. 2. Two digits indicate tensile strength x 1000 PSI. 4. Last digit indicates usability of the electrode, i.e. type of current and the type of covering. In some cases, both the third and fourth digits are significant. 3. Third digit refers to welding position. EXX1X All position (flat, horizontal, vertical, overhead). EXX2X Horizontal and flat only. EXX3X Flat position only. EXX4X Flat, overhead, horizontal, vertical down. Classification Current Arc Penetration Covering & Slag Iron Powder EXX10 DCEP Digging Deep Cellulose - sodium 0- 10% EXXX1 AC or DCEP Digging Deep Cellulose - potassium 0 EXXX2 AC or DCEN Medium Medium Titania - sodium 0-10% EXXX3 AC or DCEN or DCEP Soft Light Titania - potassium 0- 10% EXXX4 AC or DCEN or DCEP Soft Light Titania - iron powder 25-40% EXXX5 DCEP Medium Medium Low hyd. - sodium 0 EXXX6 AC or DCEP Medium Medium Low hyd. - potassium 0 EXXX8 AC or DCEP Medium Medium Low hyd. - iron powder 25-40% EXX20 AC or DCEN Medium Medium Iron oxide - sodium 0 EXX22 AC or DCEN or DCEP Medium Medium Iron oxide - sodium 0 EXX24 AC or DCEN or DCEP Soft Light Titania - iron powder 50% EXX27 AC or DCEN or DCEP Medium Medium Iron oxide- iron powder 50% EXX28 AC or DCEP Medium Medium Low hyd. - iron powder 50% EXX48 AC or DCEP Medium Medium Low hyd. - iron powder 25-40% DCEP — Direct Current Electrode Positive Note: Iron powder percentage based on weight of the covering. DCEN — Direct Current Electrode Negative MILD STEEL COVERED ELECTRODES ELECTRODE CLASSIFICATION FIGURE 3

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