© COPYRIGHT 2000 THE ESAB GROUP, INC. LESSON III a)   Alloying Elements - Alloying elements such as molybdenum, chromium, nickel, manganese and others impart specific mechanical properties to the weld metal. b)   Binders - Soluble silicates such as sodium and potassium silicates, are used in the electrode coating as binders.  Functions of binders are to form a plastic mass of coating material capable of being extruded and baked.  The final baked coating should be hard so that it will maintain a crater and have sufficient strength so that it will not spall, crack or chip.  Bind- ers are also used to make coating non-flammable and avoid premature decomposition. c)   Gas Formers - Common gas forming materials used are the carbohydrates, hydrates, and carbonates.  Examples would be cellulose (such as wood flock), the carbonates of calcium and magnesium, and chemically combined water as is found in clay and mica. These materials evolve carbon dioxide (CO2), carbon monoxide (CO), and water vapor (H2O) at the high temperature of the welding arc.  Free moisture is another gas-forming ingredient that is found particularly in cellulosic type electrodes and is a part of the formulation in amounts of 2%-3%.  It has a marked influence on the arc and is a necessary ingredient in the E6010 type electrode. d)   Arc Stabilizers - Air is not sufficiently conductive to maintain a stable arc, so it becomes necessary to add coating ingredients that will provide a conductive path for the flow of current.  This is particularly true when welding with alternating current.  Stabilizing materials are titanium compounds, potassium compounds, and calcium compounds. e)   Fluxes and Slag Formers - These ingredients are used primarily to give body to the slag and impart such properties as slag viscosity, surface tension, and melting point. Silica and magnetite are materials of this type. f) Plasticizers - Coatings are often very granular or sandy, and in order to suc- cessfully extrude these coatings, it is necessary to add lubricating materials, plasticizers, to make the coating flow smoothly under pressure.  Sodium and potassium carbonates are often used. The chart in Figure 2 shows typical coating constituents and their functions for two types of mild steel electrodes.  Note that the moisture content in the cellulosic E6010 is much higher than in the low hydrogen E7018 type.  The moisture in the E6010 coating is necessary to produce the driving arc characteristic and is not harmful when welding the lower strength steels.  Hydrogen can cause problems when welding the higher strength steels and will be discussed in detail in Lesson IV.

Lesson 1
The Basics of Arc Welding
Lesson 2
Common Electric
Arc Welding Processes
Lesson 3
Covered Electrodes for Welding
Mild Steels
Lesson 4
Covered Electrodes for Welding Low Alloy Steels
Lesson 5
Welding Filler Metals for Stainless Steels
Lesson 6
Carbon & Low Alloy
Steel Filler Metals -
Lesson 7
Flux Cored Arc Electrodes Carbon Low Alloy Steels
Lesson 8
Hardsurfacing Electrodes
Lesson 9
Estimating & Comparing Weld Metal Costs
Lesson 10
Reliability of Welding Filler Metals
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