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 wires 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. The chemical composition of the solder core, a direct impact on 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. Electrode drug skin is coated on the surface of the coating layer of the solder core. Drug skin formed after the decomposition of melt in the welding process gas and slag, the effect of mechanical protection, metallurgical processing, the role to improve process performance. Composition of drug skin: mineral classes (such as marble, fluorspar, etc.), ferroalloy and metal powder (such as ferromanganese, ilmenite, etc.), class of organic compounds (such as wood flour, starch, etc.), chemical products (such as titanium white powder, sodium silicate, etc.). Electrode drug skin is an important factor in determining the weld quality in the welding process, the role of the following aspects: to improve the stability of arc burning. Light electrode with drug-free skin is not easy to ignite the arc. Even if the ignition can not be stable combustion. Electrodes drug skin generally contains potassium, sodium, calcium and low ionization potential of the substance, which can improve the stability of the arc, to ensure that the welding process is ongoing. Protecting the weld pool. Welding process, oxygen, nitrogen and water vapor in the air, immersed in the weld, the weld will bring adverse effects. Not only the formation of pores, but also reduce the weld mechanical properties and even lead to cracks. Electrode drug skin melting, resulting in a large number of gas enveloped the arc and weld pool will reduce the interaction of the molten metal and air. Weld cooling, the melting of drug skin formation of a layer of slag covering the weld surface to protect the weld metal and slow cooling, reducing the possibility of generating pores. Ensure weld deoxy to parathion impurities. Welding process protection, but still it is inevitable that a small amount of oxygen into the molten bath, metal and alloy oxidation and burning of the alloying elements, reduce weld quality. Therefore, the need to add a reducing agent (such as manganese, silicon, titanium, aluminum, etc.) in the electrode drug skin into the molten pool oxide reduction. Add alloying elements to the weld. Due to the high temperature of the arc, the weld metal alloying elements will be evaporation burning, so that the mechanical properties of weld decreased. Therefore, we must join the appropriate alloying elements to the weld through drug skin, to make up for the burning of the alloying elements to ensure or improve the mechanical properties of the weld. Some alloy steel, but also by the skin of the drug to the weld penetrate the alloy close to the weld metal and base metal composition, mechanical properties to catch up with even more than the base metals. Improve welding productivity, reduce splashing. The electrode drugs leather droplet increase and reduce the role of splashing. Electrode was slightly lower than the melting point of drug skin welding the core of the solder joints, but welding cables in the central area of ??the arc, the higher temperature, the solder core is first melted, drug skin may cause delay in melting point. Formed in the electrode ends of a short segment of drug leather tube, and the role of Arc force, the droplet on the straight hitting the bath and make it conducive to the overhead position welding and vertical welding. In addition, the solder core coated with a drug leather, the arc heat is more concentrated. The same time, due to the reduction of metal loss caused by spatter, increase deposition coefficient, improved welding productivity. In addition, the amount of dust in the welding process will be reduced.
Carbon (C) Carbon is the main alloying element in steel, When the carbon content increases, the strength of steel, the 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 Take into account the impact of carbon steel hardenability and increase crack sensitivity, low-carbon steel welding core carbon content is generally 0.1%. Manganese (Mn) manganese steel is a good alloying agent, and its strength and toughness increased with increasing manganese content. In the welding electrode, 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% of welding some special-purpose steel wire, the manganese content up to 1. 70% of 2.10%. Silicon (Si) Silicon is also a good alloying agent, adding an appropriate amount of silicon in steel 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. 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. Nickel (Ni) of nickel on the toughness of steel have more significant effects, the general low-temperature impact value higher, the appropriate incorporation of nickel. Sulfur sulfur (S) is a harmful impurities, with the increase of sulfur content, will increase the tendency of hot cracking of welds, Welding Cable sulfur content not greater than 0.04%. In the welding of important structures, the sulfur content not greater than 0.03%. Phosphorus (P)