ELECTRODE MATERIALS and ELECTRODE SELECTION
ME 473 WELDING TECHNOLOGY Yrd.Doç.Dr. Oğuzhan Yılmaz
Welding Welding Technology
Types of welding consumables
There are many types of materials used when making welds. These welding materials are generally categorized under the term filler metals, metals, defined as the metal to be added in making a welded, brazed, or soldered joint. weld. Specifications of filler metals have been determined by standart organisations, such as;
AWS (American welding society) and ANSI (The American National Standart Institute) CSA (Canadian Standart Association) ISO (International Standarts Organisation) DIN (Germany) EN (European Norm) TS (Turkish Standarts)
Welding Welding Technology
Types of welding consumables
There are many types of materials used when making welds. These welding materials are generally categorized under the term filler metals, metals, defined as the metal to be added in making a welded, brazed, or soldered joint. weld. Specifications of filler metals have been determined by standart organisations, such as;
AWS (American welding society) and ANSI (The American National Standart Institute) CSA (Canadian Standart Association) ISO (International Standarts Organisation) DIN (Germany) EN (European Norm) TS (Turkish Standarts)
Welding Welding Technology
Filler Metals
Filler Metals can be classified into four basic categories:
Covered electrodes
Fabricated (tubular or cord) electrode wire Fluxes for welding
HORIZONTAL POSITON
Most specifications include usability factors showing the; or filler metal is designed desi gned ffor or the welding current that should be used coating. the type of coating. Size and packaging information is also provided.
VERTICAL POSITON
Welding Technology Welding
Covered Electrodes
The covered electrode is a very popular type of filler metals used in arc welding. The selection of the covered electrode for specific work is based on the electrode usability, the composition and properties of the deposited weld metal. n or er o proper y se ec an e ec ro e, s necessary o un ers an e function of the coating, the basis of specifiying, the usability factors, and the deposited weld metal properties. The coating of the electrode provides;
Gas from the decompositon of certain ingredients of the coating shield the arc from the atmosphere The deoxidizers for purifying the deposited weld metal Slag formers to protect the deposited weld metal with a slag from atmospheric oxidation Ionizing elements to make the arc more stable and to operate with alternating current Alloying elements to provide special characteristics to the deposited weld metal Iron powder to improve productivity of the electrode
Welding Technology Welding
Covered electrodes
An electrode coating is designed to provide as many as possible of the following desirable characteristics:
Specific composition of the deposited weld metal Specific mechanical properties of the deposited weld metal Elimination of weld metal porosity Elimination of weld metal cracking Desirable weld deposit contour Desirable weld metal surface finish (i.e., smooth) Elimination of undercut adjacent to the weld Minimum spatter adjacent to the weld Ease of manipulation to control slag in all positions Stable arc welding High rate of metal deposition Elimination of harmful odors and fumes Reduced electrode overheating during use Strong, tough, durable coating Easy slag removal
No single electrode type will meet all of the requirements.
Instead, there is a variety of electrode types, each having certain desirable characteristics.
Welding Technology Welding
Covered electrodes
The coatings of electrodes for welding mild and low-alloy steels may have from six to twelve ingredients, such as; Cellulose: to provide gaseous shield with reducing agent. The gas shield surroundin the arc is roduced b the disinte ration of cellulose. Metal carbonates: to adjust basicity of the slag and to provide a reducing atmosphere (with the aid of CO gases) Titanium dioxide: to help form a high fluid but quick-freezing slag. It will also provide ionization for the arc. Ferromanganese and ferrosilicon: to help dioxidize the molten weld metal and to supplement the manganese content and silicon content of the deposited weld metal. Clays and gums: to provide elasticity for extruding the plastic coating ma er a an o e p prov e s reng o e coa ng Calcium fluoride: fluoride to provide shielding gas to protect the arc, adjust the basicity of the slag, and provide fluidity and solubility of the metal oxides. Mineral silicates: to provide slag and give strength to the electrode covering Alloying metals: include nickel, molybdenum, chromium, and so on, to provide alloy content to the deposited weld metal.
Welding Technology Welding
Covered electordes
Iron or manganese oxide: to adjust the fluidity and properties of the slag. In small amounts, iron oxide helps to stabilize the arc. Iron powder: to increase the productivity by providing additional metal to be . The binder used for most electrode coatings is sodium silicate, which will chemically combine and harden to provide a tough and strong coating. Covered electrodes can be easily damaged. Therefore they need special care Electrodes may become unusable if they are exposed to moisture for an extended lenght of time. The coatin s of some t es of electrodes absorb moisture when ex osed to humid atmosphere. Cellulose, rutile and acid electrodes are fairly insensitive to moisture and can tolerate quite high moisture content without the risk of porosity in the weld.
Welding Technology Welding
Covered electrodes
The coatings of low-hydrogen electrodes pick up moisture quickly when exposed to a high humidity atmosphere. Electrodes should be stored in a special storeroom with controlled . Electrodes can be damaged by aging. Very old electrodes of most types will have a furry surface on the coating, usually white. This is from the crystallization of the sodium silicate.
Welding Technology Welding
Electrode selection for steels
Covered electrodes are mostly used for by welding processes in construction and fabrication industries due to cheapness, basicity, flexibility, weldability of different materials etc. there is no single electrode type for general purpose. Selection of the best electrode type mainly depends on the type of steel and its mechanical properties. In catalogues which are prepared by manufacturers, each type of electrode is classified as follows:
Manufacturing standarts Materials to be used for Chemical and mechanical properties Welding positions to be used
Welding Technology Welding
The role of coverings:
There are five groups of coverings:
Acid covering: They contain oxides, silicates and high content of oxygen. Slag is in porous and honeycomb shape. It can be easily . , are not used in general purpose. Cellulose covering: mainly contain celluloses such as, vegetals. These substances decomposes and produce hydrogen gases. Hydrogen improves the arc voltage and arc penetration. Due to high hydrogen content, these types of electrodes are not preferred for the welding of high strength steels. Rutile covering: Main composition is titanium oxide. The titanium oxide eas y orms s ag an s a ze e arc. ese e ec ro es can e use for all positions. Hydrogen content is high which is above the accepted limits for high strength steels. Basic covering: The cover mainly consists of calcium-flouride and calcium carbonate. These electrodes are used for high strength steels. Weld metal has good mechanical properties. Slag cannot be easily removed.
Welding Technology Welding
The role of coverings
Iron-powder covering: In order to increase the efficiency of the electrodes, iron powders are added to the covers. This process increases the efficiency more than %100. It also increases the deposition rate and fairly good weld .
Welding Technology Welding
Electrode Standarts
Although electrode manufacturers have their own brand-name, electrodes are produced based on specific standarts and designated according to the used standart. ,
TS 563 EN 499 Turkish Standart AWS A5.1/ ASTM-233 EN 499 European Standarts
Welding Technology Welding
TS 563 EN 499 Designation of the elctrodes for nonnon-alloy and low low-alloy steels
Welding Technology Welding
Electrode selection for carbon steels
Welding Technology Welding
Welding Technology Welding
Welding Technology Welding
Welding Technology Welding
Welding Technology Welding
Welding Technology Welding
Welding Technology Welding
Welding Technology Welding
Welding Technology Welding
Welding Technology Welding
SAMPLE ELECTRODES (1): Rutile E 42 0 RR 12
Welding Technology Welding
SAMPLE ELECTRODES (2): Basic E 42 3 B 42 H10
Welding Technology Welding
SAMPLE ELECTRODES (3): Alcord 12 Si
Welding Technology Welding
SAMPLE ELECTRODES (4): Citodur 600
Welding Technology Welding
SAMPLE ELECTRODES (5): INOXINOX - Special electrode
Welding Technology Welding
SAMPLE ELECTRODES (6): Citochromax
