Electrode ("covered" electrode) gas welding or welding and melting the metal strips that fill in the junction of the welding workpiece. Electrode materials are usually the same material as the workpiece.

The composition of theWelding Rod.

The electrode welding core and drug skin of two parts. The electrode is outside the core of metal welding, coating (drug skin) uniform pressure applied to the welding core carefully. Different types of electrode welding core. Ie, electrode welding core metal core, in order to ensure the quality and performance of the weld, butt the content of metal elements in the core there are stringent regulations, especially the content of harmful impurities (such as sulfur, phosphorus, etc.), there should be strict restrictions, better than the parent metal. Welding core components directly affect the composition and performance of the weld metal, the harmful elements in the welding core to minimize the core of welding carbon steel and low alloy steel welding generally use low-carbon steel welding core, and fill up the manganese silicon, chromium, nickel, and other ingredients (see the wire national standard GB1300 77). The one hand, low-carbon and low carbon content steel wire plastic, easier to wire drawing, on the other hand can reduce the reducing gas CO concentration, reduce spatter or porosity can be increased weld metal solidification temperature, beneficial to the overhead position welding. Adding other alloying elements in order to ensure the comprehensive mechanical properties of the weld, welding performance and to remove impurities, but also have a certain effect. Other high-alloy steel, aluminum, copper, iron and other metal materials, the composition of the solder core addition to asking the weld metal are similar, the same should also control the content of impurities, according to process requirements often by adding certain alloying elements. The electrode is coated with a drug skin for SMAW consumable electrode, which is a medicated skin and welding core composed of two parts. Electrode front-end drug skin around the 45 ° chamfer, in order to facilitate arc. Some bare welding core in the tail, about the electrode length of 1/16, to facilitate the welding clamp hold and conductivity. Electrode diameter Chung actually refers to the solder core diameter) is usually 2,2. 5,3. 2 or 3, 4, 5 or 6mm several specifications, it is common 3. 2, 4, 5 its length "L" is generally between 250 ^ -450 mm.
    Welding core
Electrode welding in the metal core covered by the medicine bag is known as core. Welded core is generally a certain length and diameter of the wire. When welding, the welding core has two effects: First, the conduction of the welding current, arc energy converted into heat, welding core melting as the formation of the weld filler metal with the liquid base metal fusion. Electrode welding, welding core metal part of the whole of the weld metal. Welding core {chemical composition directly affect the quality of the weld. Therefore, as the electrode core wire provides separately its grade and composition. , Known as the wire for submerged arc welding, electroslag welding, gas shielded arc welding, gas welding fusion welding method for the filler metal.
(1) welding of various alloying elements in the core welding
1) carbon (C) Carbon is the major alloying elements in steel, when the increase in carbon content of steel {strength, hardness significantly increased, while the plasticity decreases. In the welding process, the carbon play a certain role in deoxy role in the arc under high temperature and oxygen compounds, to generate carbon monoxide and carbon dioxide gas, arc and pool ambient air excluded, to prevent oxygen in the air, nitrogen harmful gas bath adverse impact of reducing the oxygen and nitrogen content in weld metal. If the carbon content is too high, severe reduction will cause a large splash and stomatal Taking into account the impact of carbon steel hardened crack sensitivity increased, the carbon content is generally of low carbon steel welding core cluster by 0.1%. 2) Manganese (Mn) of manganese in steel is a good alloying agent, with the increase of manganese content, the strength and toughness will be increased. In the welding process, manganese is also a good deoxidizer, can reduce the oxygen content in the weld. Manganese and sulfide co-formation of manganese sulfide float in the slag, thereby reducing the weld hot cracking tendency. General carbon structural steel welding core manganese content of 0.30% 0 55%, welding some of the special purpose of the wire, and its manganese content up to 1. 70% of 2.10%. 3) Silicon (Si), silicon is also a good alloying agent in steel and adding an appropriate amount of silicon can improve the yield strength, flexibility and acid resistance; if the content is too high, then reduce the ductility and toughness. In the welding process, the silicon also has a good deoxidation capacity with oxygen to form silicon dioxide, but it will improve the viscosity of the slag, easy to promote non-metallic inclusions generated. 4) Chromium (Cr) Chromium can increase the hardness, wear resistance and corrosion resistance. For low-carbon steel, chromium is an accidental impurity. Metallurgical characteristics of the chromium is subject to rapid oxidation, the formation of refractory oxides of chromium oxide (Cr2O3), thereby increasing the likelihood of weld metal inclusions. Chromium oxide transition to slag make the slag viscosity increased, decreased mobility. 5), nickel (Ni of nickel on the toughness of steel have a more significant effect, the general low-temperature impact value is higher, properly mixed with some nickel. 6) sulfur (S) Sulfur is a harmful impurity, with increasing sulfur content will increase the tendency of hot cracking of welds, welding core sulfur content not greater than 0.04%. In the welding of important structures, the sulfur content not greater than 0.03%. 7) Phosphorus
(2) the classification of welding core
Welding core welding wire in accordance with national standards (GB 1300-77) classification for the welding of special steel wire can be divided into the three types of carbon structural steel, alloy steel, stainless steel.
   Drug skin
Pressure applied to the surface of the coating of the welded core called coating. The electrode coating plays an extremely important role in the welding process. The use of a drug-free skin, light electrode welding in the welding process, the oxygen and nitrogen in the air will be a substantial intrusion of molten metal, oxide and nitride formation of metallic iron and useful elements carbon, silicon, manganese and other various oxides and nitride, and left in the weld, causing the weld slag or cracks. Melt into the molten bath, the gas may cause the weld to produce a large number of pores, these factors can greatly reduce the weld mechanical properties (strength, impact value, etc.), while the weld brittle. In addition to using the optical electrode welding, the arc is very unstable, serious splash, weld forming poor. Found in the course of practice outside in the light electrode coated with a layer from a variety of minerals composed of drug skin, make arc stability, weld quality is improved, the electrode is coated electrode. With the continuous development of industrial technology, people created a now widely used in high-quality thick coated electrode.
    The requirements of the welding rod
(1) easy arc to ensure a stable arc, little splash in the welding process. (2) drug skin melting rate should be slower than the speed of welding core melt to cause the horn-like set of simple (sleeve length should be less than the solder core diameter), droplet transition and resulting in the protective atmosphere; (3) slag proportion should be less than the proportion of molten metal solidification temperature should be slightly lower than the metal solidification temperature, slag shell should be easy to take off; (4) the role of blended gold and metallurgical processing; (5) adapt to a variety of position welding.
   Electrode model and grades
(1) The grades of the electrode
Structural steel, for example: grades, the preparation method. Results XXX, became the structural steel electrode, the first three figures represent the type of drug skin welding current requirements 1, 2: on behalf of the tensile strength of weld metal.
(2) model of the electrode
Model of the electrode is determined by the relevant national standards with international standards. EXXX, structural steel, for example, model preparation method for the letter "E", said electrode, said deposited metal minimum tensile strength, in the first two of the third digit electrode welding position, and the third, the four-digit type of welding current and the type of drug skin.
(3) electrode models representation
Cast iron electrode with Z at the beginning, low temperature steel, nickel alloy electrode W Ni, heat-resistant steel welding rod, welding electrodes R with D chromium stainless steel electrode with GA, special welding rod, said silver-based electrode using the TS HL , copper and copper alloys T, aluminum and aluminum alloys with the L and air electrode with HS.
    Of electrode classification
Welding under different circumstances, three classification methods: Classification of welding rod use classification, according to the classification of the main chemical ingredient of the drug skin, drug skin melting slag characteristics. There are two forms of expression in accordance with the purpose of the electrode, a former Ministry of Machinery Industry prepared, welding can be divided into: structural steel electrode, heat-resisting steel electrodes, stainless steel welding rod, welding electrodes, low temperature steel electrodes, cast iron electrode , nickel and nickel alloy rods, copper and copper alloys, aluminum and aluminum alloys and special purpose welding rod. National standards for carbon steel electrode, low alloy electrodes, stainless steel welding rod, welding electrodes, cast iron welding rod, copper and copper alloys, aluminum and aluminum alloys. Two there is no difference of principle, the former commercial grade, the latter model, said. Classified according to the chemical composition of the electrode drug skin, welding can be divided into: type electrode of titanium dioxide, titanium dioxide calcium electrode, ilmenite type electrode, the iron oxide type electrode, cellulose type electrode, low hydrogen type electrode graphite electrode and the base electrode. According to the melting of the electrode drug skin characteristics of the slag to classification, welding can be divided into acid electrode and alkaline welding rod. The main ingredient of the drug skin acid electrode for acidic oxides such as silica, titanium dioxide, ferric oxide, etc.. Alkaline electrode main ingredient of the drug skin as alkaline oxides, such as marble, fluorite. The classification of the welding rod, respectively, by end-use, the different perspectives of the slag basicity, the main component of the electrode drug skin, the electrode performance characteristics to classify the welding.
 By Type
Current electrode classification, is prepared according to the the electrode national standards and the Ministry of Machinery Industry of the welding material samples. The electrode model is divided into eight categories, according to national standards electrode grade use is divided into 10 categories.
 
Categories of division of welding electrodes
 
 
Electrode Model Code national standards of the classification model of serial electrode electrode the the grades code electrode classification (use classification) grades code characters (letters)
12 low alloy steel electrodes for carbon steel electrode E E GB/T5117-95 GB/T5118-95 1 2 3 structural steel electrode molybdenum and chrome molybdenum steel electrode of low temperature steel welding rod junction (J) heat (R), temperature (W)
3 stainless steel electrode E GB/T983-95 4 stainless steel electrode (1) chromium stainless steel electrode (2) chrome-nickel stainless steel electrode with Cr (G) Austria (A)
The 45678 hardfacing electrode cast iron electrode of nickel and nickel alloy welding rod copper and copper alloys of aluminum and aluminum alloys - ED, the EZ ENi the TCu TAl - GB/T984-85 GB/T10044-88 GB/T13814-92 GB/T3670 -83 the GB/T3669-83 5 6 7 8 9 10 surfacing electrode cast iron electrode of nickel and nickel alloy electrode of copper and copper alloys, aluminum and aluminum alloys for special purposes electrode reactor (D) cast (Z), nickel (Ni) copper ( T) aluminum (L) Special (TS)
All major types of electrodes of the main performance also divided into several subcategories, such as low alloy steel electrodes, can be divided into high strength low alloy steel electrodes, low temperature steel welding rod, heat-resistant steel electrode, water resistant to corrosion with the electrode. Some electrode at the same time can have multiple uses.
  Acid-base classification of the slag
Welding slag basicity, that is divided in proportion to the alkaline oxides in the slag and acidic oxides.
(1) acid electrode
Drug skin contains a lot of acid such as TiO2, SiO2 slag material and a certain amount of carbonate slag strong oxidizing slag basicity coefficient is less than 1. Acid electrode welding process, arc stability, can be AC, DC, small splash, slag fluidity and off the slag, the slag mostly glassy, ​​loose and off the residue of good performance, the appearance of the weld appearance. Acidic electrode coating contains more silica, iron oxide and titanium dioxide, strong oxidation, the higher oxygen content in the weld metal alloying elements burning more, smaller coefficient of alloy transition, deposition metal hydrogen content is also higher, thus the lower the ductility and toughness of the weld metal.
(2) basic (low hydrogen type) electrode
Drug skin contains large amounts of alkaline slag material (marble, fluorite, etc.), and contains a certain amount of deoxidizer and alloying agent. Alkaline electrode depends mainly on the carbonate decomposition of CO2 for shielding gas (such as CaCO3), the arc column, an atmosphere of hydrogen partial pressure lower, and calcium fluoride in fluorite at high temperatures and hydrogen combine to form hydrogen fluoride (HF), reduce the amount of hydrogen in the weld, so the alkaline electrode is also known as a low hydrogen type electrode. Measured by glycerol per 100g diffusible hydrogen content in the deposited metal, alkaline electrode 8mL, acid electrode 17 ~ 50mL. CaO in the number of basic slag, slag desulfurization capacity, and the deposited metal thermal crack ability. Moreover, the alkaline electrode due to the low content of oxygen and hydrogen in the weld metal, non-metallic inclusions less, with high ductility and impact toughness. Alkaline electrode due to the drug skin contain more fluorite, arc stability, the general use of the DCRP, only when the drug skin contains higher amounts of stable arc agent, AC and DC dual-use. Alkaline electrodes are generally used for welded structures, such as to withstand the dynamic load or rigid structure.
 Classification according to the drug skin ingredients
In accordance with the main component of the drug skin can determine the type of electrode coating, as shown in â‘ . Of drug skin formula, resulting in the characteristics of a variety of drug skin type electrode slag, welding performance and weld metal mechanical properties are very different. Even the same type of drug skin, different grades of electrode composition and ratio of drug skin electrode process performance will be significant differences. Electrodes drug skin types and main features see â‘¡.
The â‘  electrode type of drug skin.
Drug skin types: (1) titanium ‖ drug skin ingredients: titanium dioxide ≥ 35% ‖ welding power supply: AC or DC (2) drug skin types: titanium calcium type ‖ drug skin ingredients: titanium dioxide 30% carbonate, welding power source: DC or AC (3) less than 20% of salt ‖ drug skin types: of ilmenite ‖ drug skin main components: ilmenite ≥ 30% ‖ drug skin type welding power source: DC or AC (4): iron oxide type ‖ drug skin main components: the large amounts of iron oxide and more ferromanganese deoxidizer ‖ welding power supply: AC or DC (5) drug skin types: high cellulose sodium the ‖ drug skin main components: organic matter over 15% of titanium dioxide about 30% ‖ welding power source: DC (6) drug skin types: high-cellulose, the main component of the potassium-type ‖ drug skin: more than 15% of the organic titanium dioxide 30% ‖ welding power supply: AC or DC (7) drug skin types: low hydrogen sodium type the ‖ drug skin ingredients: calcium, magnesium carbonate and fluorite ‖ Welding Power Supply: DC (8) drug skin types: low hydrogen potassium type the ‖ drug skin ingredients: calcium, magnesium carbonate, and fluorite ‖ welding power supply: AC or DC (9) the type of drug skin: the skin of iron powder low hydrogen type ‖ drug main components: calcium, magnesium carbonate, fluorite and iron ‖ welding power supply: AC or DC (10) the type of drug skin: graphite ‖ drug skin main components: the large amounts of graphite ‖ welding power supply: AC or DC (11) drug skin types: the main component of the base ‖ drug skin: chloride and fluoride the ‖ welding power supply: DC
â‘¡ electrode drug skin type characteristics
(1) drug skin types: are not already requires the type of power supply types: does not require the main features: zirconia, rutile and alkaline type in some of the electrode, these new slag system is not yet formed a series of (2) the type of drug skin : titanium dioxide supply types: DC or AC main features: contain large amounts of titanium dioxide electrode process performance, stable arc, then arc spatter is small, shallow penetration, slag coverage, easy slag detachability. weld ripple particularly beautiful, all-position welding, especially appropriate for sheet metal welding, weld plastic and crack less. With drug skin changes in the amount of potassium, sodium and iron, is divided into the main features of the high titanium potassium type, high-titanium sodium and iron titanium (3) the type of drug skin: a lime-titania type of power: DC or AC : drug skin with titanium dioxide for more than 30 percent calcium, magnesium carbonate, 20%, the electrode process performance, good slag fluidity, and general penetration, arc stability, weld appearance and easy slag detachability, apply to the whole position welding, such as the J422 is guilty of this type is currently the most widely used as a welding rod used in the carbon steel electrode. (4) the type of drug skin: ilmenite type of power: DC or AC main features: drug skin containing ilmenite 305, electrode melting fast, slag fluidity, penetration deep, easy slag detachability, welding neat waves, stable arc welding, fillet welding process better performance, lesser vertical welding the welds have good crack resistance (5) drug skin types: iron oxide type of power: DC or AC main features: drug skin with large amounts of iron oxide and more ferromanganese Deoxidizer of, penetration, melting fast, high welding productivity, stable arc, then arc welding of overhead position welding is more difficult, splashing slightly larger, the weld thermal cracking performance, apply to plate welding. Arc force, suitable for field operation. Drug skin by adding a certain amount of iron compared with iron powder titania type (6) drug skin types: cellulose type of power: DC or AC main features: drug skin containing more than 15% organic, 30% of titanium oxide, good welding performance, stable arc, Arc force is large, deep penetration, slag, slag detachability. Can be used for vertical down welding, forming welding deep penetration or one-side welding. Li, Yang welding process. Applicable to the welding of the sheet structure, fuel tank, pipeline, vehicle shell. Arc stability in the skin with the drug agent, the binder content is divided into high-cellulose sodium (DCRP), high cellulose potassium two groups (7) drug skin types: low hydrogen potassium type (low hydrogen sodium type ) Power Supply: AC or DC (direct current) main features: drug skin composition of carbonate and fluorite. Electrode before use subject to the 300 ~ 400 ℃ baking. Short arc welding process in general, all-position welding. The weld has good crack resistance and mechanical properties of force. Suitable for the welding of welded structures. In accordance with the dose of drug skin in the steady arc, the amount of iron and binder is divided into low hydrogen sodium, low hydrogen potassium type and iron powder low hydrogen type (8) drug skin type: graphite Power Type: DC or AC main characteristics: drug skin contains large amounts of graphite, usually cast iron or hardfacing electrode. Low-carbon steel welding core, poor welding performance, splash more, smoke less slag suitable for flat welding. The use of non-ferrous metal welding core can improve their process performance, but the current is not easy (9) the type of drug skin: the base type of power: DC Main features: drug skin contain large amounts of chloride and fluoride, is mainly used for aluminum and aluminum alloys. Moisture absorption, drying prior to welding. Drug leather low melting point, melting fast. DC power to the welding process is poor, short arc, slag corrosion after welding required hot water cleaning In addition, for drug skin containing large amounts of iron powder electrode can be called the iron powder electrode. At this time, in accordance with the main component of the corresponding electrode drug skin can be divided into the iron titanium, iron titanium calcium type, iron ilmenite type, iron and iron oxide type, iron powder low hydrogen type, etc., constitute the iron Series of powder electrode.
 Classified by electrode performance
Special electrode to electrode performance classification, are manufactured according to the performance of its special use, such as ultra-low hydrogen electrodes, low dust and low toxicity electrode, vertical down welding rod, lying welding electrode, a bottom electrode, efficient iron powder electrode, moisture electrode, underwater welding rod, gravity electrode.
 Electrode of the selection principle
Electrode selection is required to ensure the welding of structural safety, feasible use of the premise, according to the chemical composition of the welded materials, mechanical properties, thickness and joint type, welding structural characteristics of the stress state of the structural conditions of use on weld properties welded construction conditions and the technical and economic benefits examine the targeted selection of welding rod, if necessary, need for welding test.
(1) with steel welding electrode selection of points
The â‘  consider the weld metal mechanical properties and chemical composition for ordinary structural steel, and usually require the strength of the weld metal and base metal, should use the deposited metal tensile strength equal to or slightly higher than the base metal electrode. Alloy structural steel, may also require the same or close to alloy composition and the base metal. In the rigidity of the welded structure, joint stress, weld cracks easily the adverse circumstances, you should consider using a low strength of the base metal electrode. When the base metal, carbon, sulfur, phosphorus and other elements of the high levels of the weld prone to cracking, should use good crack resistance of the basic low-hydrogen electrodes. (2) consider the welding component performance and working conditions of the weldment to withstand the loads and impact loads, in addition to meet the strength requirements, the principal should ensure that the weld metal has a high impact toughness and ductility, the choice of plastic, high toughness, low hydrogen electrodes. Contact with the corrosive medium, the weldment should be selected according to the nature of the medium and the corrosion characteristics of stainless steel type electrode or other corrosion-resistant electrode. At high temperature, low temperature, wear or other welding work under special conditions should be used in the corresponding heat-resistant steel, low temperature steel, surfacing, or other special purpose welding rod. (3) to consider welding the structural characteristics and loading conditions on the structure and shape of complex, rigid Heavy welding, easy to make a lot of internal stress in the welding process, weld cracks, should use good crack resistance of alkaline low hydrogen electrode. Uneven force large, welded parts are difficult to clean the weldment should be used for rust, oxide, oil is not sensitive to acid electrode. The conditions imposed can not flip the weldment should be used suitable for all position welding electrode. The â‘£ consider the construction conditions and economic benefits to meet product performance requirements should be used in the process and good acid electrode. Acid electrode should be used in small or poorly ventilated situations, or low-dust electrode. The structure of large amount of welding work, the conditions should maximize the use of high efficiency electrode, such as iron powder electrode, high efficiency, gravity electrode, or the selection of special electrode of the bottom electrode to stand down the electrode and the like, in order to improve welding productivity.
Electrode selection of points _AT_ (2) The welding of dissimilar steel
① intensity level different carbon steel + low-alloy steel (or low-alloy steel + high strength low alloy steel) generally requires the weld metal or the joint strength of not less than two minimum strength of the weld metal, the choice of electrode deposited metal strength should be able to ensure the strength of the welds and joints of not less than the intensity low voltage to the base metal strength, ductility and impact toughness of the weld metal should not be lower than the performance of higher strength plastic poor voltage parent material. Therefore, according to the intensity level of the two lower steel selection of welding rod. However, in order to prevent welding cracks, the intensity level should be higher, poor weldability of the steel to determine the welding process, including welding specification, preheat temperature and post weld heat treatment. ② low alloy steel + austenitic stainless steels in accordance with the limit values ​​of chemical composition of the deposited metal selected electrode is generally used in higher levels of chromium and nickel, plastic, and good crack resistance Cr25-Ni13 austenitic steels electrode in order to avoid cracks due to brittle hardened organization. But should be poor weldability of stainless steel to determine the welding process and specification. ③ stainless clad steel plate electrode of the selection of three different performance requirements should be considered on the grassroots level, stratified transition layer welding. Welding of the primary (carbon or low alloy steel), the choice of the appropriate strength grade structural steel electrode; stratified direct contact with the corrosive medium should be used in the corresponding components of austenitic stainless steel electrode. The key is the welding of buffer layer (ie, stratified with the primary interface) must take into account the dilution effect of the substrate material should be used in chromium and nickel content is high, good ductility and crack resistance of Cr25-Ni13-type austenitic steel electrode.