[edit]Composition of welding electrodes
Welding electrodes are made up of two parts: the core and the flux skin. Welding electrode is in the metal welding core outside the paint (flux skin) uniform, centripetal pressure coating on the core. Different types of welding rods, welding core is also different. Welding core that is the metal core of the electrode, in order to ensure the quality and performance of the weld, the content of each metal element in the weld core have strict regulations, especially on the content of harmful impurities (such as sulfur, phosphorus, etc.), there should be strict limitations, better than the base material. Welding core composition directly affects the composition and properties of the weld metal, so the harmful elements in the core should be as little as possible. C content should be less than 0.10%. For example, H08A, containing S less than or equal to O.03%, P less than or equal to 0.03%, C less than or equal to 0.1%.
Welding carbon steel and low alloy steel welding core, generally choose low carbon steel as the core, and filled with manganese, silicon, chromium, nickel and other ingredients (see the national standard GB1300 a 77 wire). The reason for the use of low carbon on the one hand is the low carbon content of steel wire plasticity, wire drawing easier, on the other hand, can reduce the CO content of reducing gases, reduce spatter or porosity, and can increase the temperature of the weld metal solidification, favorable to the back welding. Add other alloying elements mainly to ensure that the comprehensive mechanical properties of the weld, while the performance of the welding process and the removal of impurities, also has a certain role.
High-alloy steel, as well as aluminum, copper, cast iron and other metal materials, the core composition in addition to the requirements of the welded metal similar to the same to control the content of impurities, and process requirements often add some specific alloying elements.
The electrode is coated with flux skin for electrode arc welding with the melting electrode, which is composed of two parts of the flux skin and the core. In the front of the electrode flux skin has 45. about the chamfer, which is to facilitate the arc. In the end there is a section of bare welding core, about 1/16 of the total length of the electrode, easy to clamp and conductive. The diameter of the electrode is actually the diameter of the core) is usually 2, 2. 5, 3. 2 or 3, 4, 5 or 6 mm and other specifications, commonly used is a small 3. 2, a small 4, a small 5 three kinds of length "L" is generally in the 250 ^ - 450 mm.
1. Cored
The metal core covered by the flux skin in the electrode is called the core. The core is generally a steel wire with a certain length and diameter. Welding, the core has two roles: one is to conduct the welding current, the arc to convert electrical energy into heat, the second is the core itself melted as filler metal and liquid base metal fusion to form a weld.
When welding electrodes, the core metal accounts for a portion of the entire weld metal. So the chemical composition of the core, directly affect the quality of the weld. Therefore, as the core of the welding rod with the steel wire are single potential unique provisions of its grade and composition. If used for submerged arc automatic welding, electroslag welding, gas shielded welding, gas welding and other welding methods for filler metal, it is called welding wire. (1) welding core alloying elements on the impact of welding
1) carbon (C) carbon is the main alloying element in steel, when the carbon content increases, steel strength, hardness increased significantly, while the plasticity is reduced. In the welding process, carbon plays a certain role in deoxidation, in the arc under the action of high temperature and oxygen compounds, generating carbon monoxide and carbon dioxide gas, the arc area and the molten pool around the air exclusion, to prevent the air oxygen, nitrogen and harmful gases on the molten pool to produce the adverse effects of the weld metal to reduce the content of oxygen and nitrogen. If the carbon content is too high, the reduction effect is intense, which will cause larger spatter and porosity. Taking into account the impact of carbon on the hardenability of steel and its increased susceptibility to cracking, the carbon content of mild steel weld core is generally cluster 0. 1%.
2) manganese (Mn) manganese in steel is a good alloying agent, with the increase in manganese content, its strength and toughness will improve. In the welding process, manganese is also a good deoxidizer, can reduce the content of oxygen in the weld. Manganese and sulfide form manganese sulfide floating in the slag, thus reducing the tendency of weld thermal cracking. Therefore, the general carbon structural steel weld core containing manganese 0. 30% to 0. 55%, welding some special-purpose steel wire, the amount of manganese up to 1. 70% a 2. 10%.
3) silicon (Si ) silicon is also a good alloying agent, add the appropriate amount of silicon in the steel to improve the yield strength, elasticity and acid resistance of steel; if the content is too high, it reduces the plasticity and toughness. In the welding process, silicon also has a good ability to deoxidize, and oxygen to form silica, but it will improve the viscosity of the slag, easy to promote the generation of non-metallic inclusions.
4) chromium (Cr) chromium can improve the hardness of steel, wear resistance and corrosion resistance. For mild steel, chromium is an occasional impurity. The main metallurgical characteristics of chromium is easy to oxidize rapidly, the formation of refractory oxide chromium trioxide (Cr203), thereby increasing the possibility of weld metal inclusions. After the transition of chromium trioxide to the slag, it can make the slag viscosity increase and fluidity decrease.
5) nickel (NO nickel has a relatively significant effect on the toughness of steel, general low-temperature impact value requirements are higher, the appropriate mixing of some nickel.
6) sulfur (S) sulfur is a harmful impurity, with the increase in sulfur content, will increase the tendency of the weld to thermal cracking, so the content of sulfur in the weld core shall not be greater than 0. 04%. In welding important structures, the sulfur content shall not be greater than 0. 03%.
7) Phosphorus (2) the classification of welding core
Welding core is based on the national standard "welding steel wire" (GB 1300-77) of the provisions of the classification of special steel wire for welding can be divided into carbon structural steel, alloy structural steel, stainless steel, three categories.
2. Flux skin
The pressure coated on the surface of the core coating called flux skin. The flux skin of the welding rod plays an extremely important role in the welding process. If the use of light welding rod welding without flux skin, then in the welding process, oxygen and nitrogen in the air will be a large number of invasive molten metal, metal iron and beneficial elements such as carbon, silicon, manganese and other oxidation and nitrogen formation of various oxides and nitrides, and residual in the weld, resulting in slag or cracks in the weld. The gas melted into the molten pool may make the weld produce a large number of pores, these factors can make the mechanical properties of the weld (strength, impact value, etc.) greatly reduced, while making the weld brittle. In addition to the use of light electrode welding, the arc is very unstable, spatter is serious, the weld is poorly formed.
People in the process of practice found that if the light electrode coated with a layer of various minerals outside the composition of the flux skin, can make the arc combustion stabilization, weld quality has been improved, this electrode is called flux skin electrode. With the continuous development of industrial technology, people created a now widely used high-quality thick flux skin welding rod.
[edit]Requirements for welding electrodes
(1) easy to start the arc, to ensure that the arc is stable, small spatter in the welding process.
(2) the flux skin melting speed should be slower than the welding core melting speed to cause a horn-like set of simple (sleeve length should be less than the diameter of the welding core), which is conducive to the transition of the molten droplet and cause a protective atmosphere;
(3) the specific gravity of the slag should be less than the specific gravity of the melted metal, the solidification temperature should also be slightly lower than the temperature of the metal solidification, the slag shell should be easy to get rid of;
(4) have a doping and metallurgical treatment effect;
(5) adapt to a variety of position welding.
[edit]Welding electrode type and grade
(1) the grade of the electrode
structural steel, for example: grade, preparation method. Junction XXX, Junction for structural steel electrodes, the third number, on behalf of the type of flux skin, welding current requirements, the first two numbers: on behalf of the tensile strength of the weld metal.
(2) type of electrode
The type of electrode is determined in accordance with relevant national and international standards. EXXXX, structural steel, for example, the modeling method for the letter "E" represents the electrode, the first two that the minimum tensile strength of the molten metal, the third digit of the electrode's weld position, the third and fourth digits represent the welding current, and the third and fourth digits represent the welding current. The third and fourth digits indicate the type of welding current and type of flux coating.
4. Classification of welding electrodes
According to different situations, electrodes have three classifications: classified according to the use of electrodes, according to the main chemical composition of the flux skin classification, according to the flux skin melted slag characteristics of classification.
According to the use of electrodes, there are two forms of expression, one for the former Ministry of Machinery Industry, can be divided into electrodes: structural steel electrodes, heat-resistant steel electrodes, stainless steel electrodes, cladding electrodes, low-temperature steel electrodes, iron electrodes, nickel and nickel alloy electrodes, copper and copper alloy electrodes, aluminum and aluminum alloys, as well as special-purpose welding electrodes. The second is the national standard, for carbon steel welding rod, low alloy welding rod, stainless steel welding rod, surfacing welding rod, cast iron welding rod, copper and copper alloy welding rod, aluminum and aluminum alloy welding rod. There is no principle difference between the two, the former is expressed in commercial grades, the latter is expressed in models.
If classified according to the main chemical composition of the electrode flux skin, the electrodes can be divided into: titanium oxide electrodes, titanium calcium oxide electrodes, ilmenite electrodes, iron oxide electrodes, cellulose electrodes, low hydrogen electrodes, graphite electrodes, and salt-based electrodes.
If according to the welding electrode flux skin melting, the characteristics of the slag to classify, the electrode can be divided into acidic and alkaline welding electrodes. Acidic welding rod flux skin is mainly composed of acidic oxides, such as silicon dioxide, titanium dioxide, iron oxide, etc.. Alkaline electrode flux skin is mainly composed of alkaline oxides, such as marble, fluorite and so on.
Welding electrodes can be divided into structural steel electrodes, heat-resistant steel electrodes, stainless steel electrodes, cast iron electrodes, copper and copper alloy electrodes, aluminum and aluminum alloy electrodes and so on according to different uses.
Welding electrodes can be divided into two categories according to the chemical properties of the slag: acid and alkaline welding electrodes. Alkaline electrode weld contains hydrogen, sulfur, phosphorus less. Weld mechanical properties are good, but sensitive to oil, water, rust, easy to produce porosity. Acid electrode welding arc stability, less spatter, good deslagging. Therefore, the important welding structural parts of the choice of alkaline electrodes, while the general structure of the choice of acidic electrodes.
Structural steel electrodes for the brand name: the first character in Chinese pinyin plus three digits to indicate such as our internship structural steel electrodes used in the brand name for J422 (or knot 422). "J" means "Junction" of structural steel welding rod. Behind the two for the number "42" for the tensile strength of the weld metal is not less than 420MPa; the last number "2" on behalf of the titanium calcium flux skin, with AC or DC power supply can be.
Acidic carbon steel electrodes
Type : J421, J421Fe, J422, J423, J425, J502, J501Fe15
Type GB Model AWS Model Type Flux Cortex Type Current Type Main Application Specifications
J421 E4313 E6013 Titanium Oxide AC/DC Welding of mild steel structure, especially suitable for thin plate and small pieces and short weld intermittent welding and cover welding requiring surface finish Φ2.0-Φ5.0
J421Fe E4313 E6013 Iron powder titanium type AC/DC Welding of low-carbon steel structure, especially suitable for thin plate and small pieces and short weld intermittent welding and cover welding requiring surface finish Φ2.5 - Φ5.0
Titanium oxide type AC/DC Welding of low carbon steel structure, especially suitable for thin plate and small pieces and short weld intermittent welding and cover welding requiring surface finish Φ2.5-Φ5.0
J422 E4303 -- Calcium Titanium AC/DC is used to weld more important low carbon steel structure and strength grade low alloy steel, such as 09Mn2, etc. Φ2.0-Φ5.0
J423 E4301 -- Titanium-iron type AC/DC can be used to weld the more important low carbon steel structure Φ3.0-Φ5.0
J425 E4311 E6011 Potassium cellulose type AC/DC is suitable for butt joints, angle joints and lap joints of thin plate structure. Such as power station flue, air ducts, transformer tanks, ship hull and vehicle outer plate of low carbon steel structure Φ3.2-Φ5.0
J502 E5003 -- Calcium Titanate AC/DC Mainly used for welding of low alloy steel such as 16Mn Φ2.0 -Φ5.0
J501Fe15 E5024 E7024 Iron Powder Titanium Type AC/DC Suitable for the welding of rolling stock, shipbuilding, boilers and other structures Φ2.5-Φ5.0
Chemical Composition of Deposited Metal % Mechanical Properties of the Deposited Metal
Grade C Mn Si S P Tensile Strength (Mpa) Yield Strength (Mpa) Elongation (%) Impact Value
°C J
J421 ≤0.12 0.3~0.6 ≤0.35 ≤0.035 ≤0.040 ≥420 ≥330 ≥22 0 ≥47
J421Fe ≤0.12 0.3~0.6 ≤0.35 ≤0.035 ≤ 0.040 ≥420 ≥330 ≥17 0 ≥47
J422 ≤0.12 0.3 ~ 0.6 ≤0.25 ≤0.035 ≤0.040 ≥420 ≥330 ≥22 -20 ≥47
J423 ≤0.20 0.3 ~ 0.6 ≤0.20 ≤0.035 ≤0.040 ≥420 ≥330 ≥22 0 ≥ 27
J425 ≤0.12 0.3～0.6 ≤0.30 ≤0.035 ≤0.040 ≥420 ≥330 ≥22 -30 ≥27
J502 ≤0.12 ≤1.60 ≤0.30 ≤0.035 ≤0.040 ≥420 ≥400 ≥20 0 ≥27
J501Fe15 ≤ 0.12 0.8~1.4 ≤0.90 ≤0.035 ≤0.040 Mo≤0.30 V≤0.08 ≥420 ≥400 ≥17 0 ≥27
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Alkaline Carbon Steel Electrodes
Kinds : J426, J427, J506, J507, J506Fe
Brand GB Model AWS Model Flux skin type Current type Main purpose Specifications
J426 E4316 E6016 Low hydrogen potassium type AC/DC Used to weld important low carbon steel and low alloy steel structure. Such as O9Mn2 etc Φ2.5-Φ5.0
J427 E4315 -- Low hydrogen sodium type DC(R) Used to weld important low carbon steel and low alloy steel, such as O9MnSi etc Φ2.5-Φ5.0
J506 E5016 E7016 Low Potassium Hydrogen Type AC/DC Used to weld medium carbon steel and low alloy steel such as 16Mn, O9MnSi, etc. Φ2.5-Φ5.0
J507 E5015 E7015 Low Potassium Hydrogen Type DC(R) It can be used to weld medium carbon steel and certain low alloy steel such as 16Mn, O9Mn2Si, O9Mn2V, etc. Φ2.5-Φ5.0
J506Fe E5018 E7018 Iron Powder Low Hydrogen Potassium Type AC/DC Suitable for the welding of carbon and low alloy steels, such as 16Mn, etc. Φ2.5-Φ5.0
Chemical Composition of the Molten Metal % Mechanical Properties of the Molten Metal
Grade C Mn Si S P Tensile Strength (Mpa) Yield Strength (Mpa) Elongation (%) Impact Value
℃ J
J426 ≤0.12 ≤1.25 ≤0.90 ≤0.035 ≤0.040 ≥420 ≥330 ≥22 -30 ≥27
J427 ≤0.12 ≤1.25 ≤0.90 ≤0.035 ≤0.040 ≥420 ≥330 ≥22 -30 ≥27
J506 ≤0.12 ≤1.6 ≤0.75 ≤0.035 ≤0.040 ≥490 ≥400 ≥22 -20
-30 ≥47
≥27
J507 ≤0.12 ≤1.25 ≤0.75 ≤ 0.035 ≤0.040 ≥490 ≥400 ≥22 -20
-30 ≥47
≥27
J506Fe ≤0.12 ≤1.6 ≤0.75 ≤0.035 ≤0.040 ≥490 ≥400 ≥22 -30 ≥27
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