In welding practice teaching, students practice in arc welding operation, often weld, burn, incomplete penetration, concave, slag, forming defects such as poor, analyzing the causes of these defects, mainly students in the welding operation and failing to observe the changes in bath temperature, there is no effective control of bath temperature and the above-mentioned defects.
Bath temperature, directly affect the quality of Copper Alloy Welding Wire, bath temperature is high, large pool, hot metal flow is good, easy-to-fusion, but too high, the molten iron under the drip easily, forming the back side welding easy to burn, to form weld, shape is also difficult to control, and the plastic connector down, bend easy to crack. Bath temperature is low, a smaller pool, hot metal dark, poor mobility, easy to produce incomplete penetration, lack of fusion, slag and other defects.
Bath temperature and the welding current, electrode diameter, electrode angle, arc burning time has a close relationship, take the following measures for the relevant factors to control the bath temperature.
1, the welding current and electrode diameter: According to the spatial location of the weld, solder level in the selection of the welding current and electrode diameter, open welding, the welding current and electrode selection of large diameter, vertical, horizontal Yang bit smaller. Such as the 12mm flat butt-welding of the closure of the bottom electrode selection φ3.2mm, welding current :80-85A, filling, cover the electrode surface used φ4.0mm, welding current :165-175A, a reasonable choice of welding current and electrode diameter, easy to control bath temperature, is the basis of weld.
2, the operation of the method, circle-shaped bath temperature operation of the transport of temperature higher than the crescent-shaped, crescent-shaped transport of temperature was higher than the zigzag operation of the bath temperature, seal welded in 12mm flat bottom, using the operation of the zigzag and with the magnitude of the swing and groove on both sides of the pause, effective control of the bath temperature, so basically the same size fuse hole, the roots do not form a groove weld and decrease the chances of burn, there is no penetration improved, so that almost flat plate welded butt welding double-sided shape is no longer difficult.
3, electrode angle, the angle between the electrode and the welding direction at 90 degrees, the arc concentration, bath temperature is high, the angle is small, arc scattered, low bath temperature, such as the 12mm flat bottom seal welding, welding angle: 50 - 70 degrees, the bath temperature has dropped, to avoid the back of the resulting weld or from high. Again, in the 12mm bottom plate for vertical welding rod seal, the joints of the electrodes used angle of 90-95 degrees, the bath temperature is rapidly increasing, smooth melt holes open, the back forming a more smooth, effective control of the connection point within concave phenomenon.
4, the arc burning time, φ57 × 3.5 pipe fixed horizontal and vertical fixed welding practice teaching, the use of off-arc method of Welding Wire China, seal welding the bottom, off the arc and arc burning time frequency directly affects the bath temperature, as wall is thin, the limited capacity of the arc heat, slow down if the bath temperature to reduce the frequency arc, easy to produce shrinkage, therefore, can only be used to control the arc burning time of bath temperature, if the bath temperature is too high, melting hole is large, the arc burning time can be reduced, so that lower bath temperature, time, melting holes smaller internal tube forming medium height, to avoid internal weld pipe welding or produce ultra-high tumors.
In summary, the welding practice teaching, students learn to observe the changes in bath temperature, effective control of weld pool temperature control method, is to learn basic welding technology, to lay the solid foundation in order to achieve a breakthrough, in order to become a outstanding work of welding technology
A high cellulose type electrode of the development of technical specifications and development difficulties
1.1 Technical Specifications
High cellulose electrode developed using AWS5.1 and AWS5.5 specified in E6010 and E7010-G electrode of technical indicators, namely: mechanical properties: E6010 Rp0.2 ≥ 330MPa Rm ≥ 420MPa A ≥ 22% Akv-30C ≥ 27J
E7010-G Rp0.2 ≥ 390MPa Rm ≥ 490MPa A ≥ 22%
Chemical composition: The chemical composition of deposited metal in line with the relevant requirements of AWS.
Process performance: excellent operational performance, to meet the requirements of the pipeline construction welding.
1.2 Development of difficulty
As we all know, high-fiber electrode is the main features of drug skin contains a lot of cellulose, wood flour, asbestos and other organic matter, organic matter in the welding combustion CO, H2 and other reducing gas, so gas is mainly cellulose electrodes welding material. To ensure that the metallurgical properties of the weld, welding metallurgy reaction process must consider the overall balance, at the same time, high-fiber electrodes is mainly used for vertical down welding, to ensure good performance, must have the right drug leather melting point and viscosity, slag skin while making appropriate drug choices.
The development of high-cellulose electrode main difficulty is how to make the electrode performance and technological properties of metallurgical balance up.
2 high-fiber electrodes slag skin drug design
2.1 Department of the choice of drug bran
According to international research experience, high-fiber electrodes slag largely determine the design of high-level research work cellulose electrodes, is generally believed that high-fiber electrodes slag slag should be short in order to ensure the vertical down welding welding operation performance. In particular slag system design, part of the researchers using high-titanium slag system (TiO ≥ 30%); some people with a non-high titanium slag system (TiO ≤ 20%). In this study, we integrated cellulose filler rod at home and abroad the advantages of slag, innovative design with a Tio2-Sio2-Mgo-MnO2-FeO slag multi-compound. Research shows that drug skin slag has a "short residue" characteristics, welding high-temperature viscosity, surface tension, melting point and moderate. Both to ensure the welding arc blow with sufficient force, but also makes each welding position (especially vertical down welding of 3:00 or 9 o'clock position) does not drip slag bath clear, easy soldering operations.
2.2 high-cellulose electrode welding metallurgy overall balance of the reaction
Drugs for high-fiber skin in welding Copper Brazing Alloys produce large amounts of reducing gases, and our use of strong oxidizing - strong reduction of the metallurgical methods, making high-fiber electrodes in various stages of the reaction equilibrium. On the one hand, we add the appropriate amount of skin in drug cellulose and other organic substances; while adding more oxidizing substances such as magnetite, magnesite, etc.; in order to prevent welding spatter generation, porosity, etc., in the skin has also joined the drug trace amounts of carbonate and composite carbide.
In this study we found that if the arc oxidizing atmosphere too, can minimize the welding holes, but the process likely to affect the electrode performance, one drip slag generated phenomenon, and second, stick generate weld slag, slag off bad. However, if the arc atmosphere to restore strong, can easily produce weld porosity and other weld defects, and Arc force is not big enough.
The manufacture of high-fiber electrodes 3
3.1 high-fiber electrodes and pre-screening of the main raw material
Electrode selection and pre-main raw materials, related to the electrodes mechanical properties more directly affect the high cellulose type coated electrode pressure production performance.
In this study, the main raw material is cellulose and oxidizing substances (magnetite and magnesia, etc.). For the cellulose in addition to considering their physical and chemical properties (such as carbon points), the still need to pay attention to two points, one fiber length should be moderate, the second is to conduct pre-treatment, removal of the lignin. Studies have shown that fiber length directly affects whether pressure will produce coated tops and eccentric, lignin is affected to a high resistance to burning of cellulose electrodes. For the oxidation of substances to be screened, selected with S, P less magnetite. Furthermore, for some alloy must be carbonized.
3.2 high-cellulose electrode surface quality control
High-fiber electrodes mechanical properties and chemical composition of the control is relatively easy, but the quality is difficult to grasp the electrode surface. We adopt the following measures received good results: â‘ control the viscosity of sodium silicate and dosage; â‘¡ drug leather raw materials with particle size; â‘¢ appropriate drying system. Now the production of cellulose electrode surface is smooth, stable welding process.
4 the overall performance of high-fiber electrodes
4.1 Mechanical Properties
Authors developed E6010, E7010-G electrodes of high mechanical properties of cellulose as shown in Table 1 and Table 2. From Table 1 and Table 2 shows that high-fiber electrodes were developed to meet the AWS.A5.1 and AWS.A5.5 cellulose Types Of Welding Wires in the relevant indicators of high demand and have a certain margin.
4.2 Chemical composition
The chemical analysis showed that the development of high-fiber electrode chemical composition of deposited metal chemical composition in line with the relevant requirements of AWS.
4.3 cellulose electrodes made of high resistance to sulfide stress cracking performance (SCC) and resistance to hydrogen induced cracking (HIC)
The use of E6010 and E7010-G electrode welding L360 fittings, in accordance with ASTM G39 standard four-point bending method for SCC tests, according to the ISO3183 standard HIC experiments, test results show that our high-cellulose electrode developed resistance to sulfide stress cracking performance (SCC ) and resistance to hydrogen induced cracking (HIC) are in line with the requirements of the welding performance to meet the construction requirements acidic environment.
4.4 high-cellulose electrode welding process performance
High cellulose electrode developed by the China Petroleum Pipeline Bureau has welding training center, Sichuan Petroleum Pipeline Bureau welding training center, training center of Xinjiang Petroleum Administration Bureau, welding inspection, and other departments in the oil - companies, Dagang Oilfield Welding Training Center and a number of units of the trial, the parties agreed that the ship developed by Luoyang High cellulose electrode welding performance is good, can be used to replace imported oil and gas pipeline welding electrode.
5 the application of domestic high-fiber electrodes
In April 2004, Xinjiang has a product pipeline welding using my development and production of domestic high-fiber electrodes, the length of 50.5 km of the pipeline, using the diameter φ219mm, wall thickness 5.2mm of X52 steel, welded construction used in all my The development of high-fiber electrodes E6010 and E7010-G.
Welding process is E6010-type (φ3.2mm) root welding, E7010-G type (φ3.2mm) filled with welding, E7010-G type (φ4.0mm) for capping and welding equipment for the ZX7 DC inverter welding machine , welding standard shown in Table 3.
In August 2004, the acceptance of the pipeline through the Party, the construction unit that made high-fiber electrode root pass blowing force is moderate, stable non-stick of the arc, good welding seam forming, filling and capping easy arc welding, stable arc , clear pool, good slag removal, easy to produce welding defects such as undercut holes, with favorable results. It reflects the welders, the welding operation is easy to grasp, and electrode performance of a company in Western Europe is roughly equal. Generally believed that small-diameter thin-walled pipe welding in the construction, the requirements for high-fiber electrode is more demanding. Engineering Practice has proved that the development and production of high-fiber electrodes can be replaced by imports of welded construction.