Jun . 12, 2024 09:02 Back to list

The influence of various alloy elements in the welding core on welding

1. Carbon (C) is the main alloying element in steel. When the carbon content increases, the strength and hardness of the steel will increase significantly, while the plasticity will decrease. During the welding process, carbon plays a certain deoxidation role. Under the high temperature of the arc, it reacts with oxygen to generate carbon monoxide and carbon dioxide gas, which removes the air around the arc zone and the molten pool, prevents the harmful oxygen and nitrogen gases in the air from having adverse effects on the molten pool, and reduces the content of oxygen and nitrogen in the weld metal. If the carbon content is too high, the reduction effect will be intense, which will cause large spatter and pores. Considering the effect of carbon on the hardenability of steel and its increased crack sensitivity, the carbon content of low-carbon steel welding core is generally 0.1%.
2. Manganese (Mn) is a good alloying agent in steel. As the manganese content increases, its strength and toughness will increase. During the welding process, manganese is also a good deoxidizer that can reduce the oxygen content in the weld. Manganese combines with sulfur to form manganese sulfide floating in the slag, thereby reducing the tendency of hot cracks in the weld. Therefore, the manganese content of general carbon structural steel welding core is 0.30% to 0.55%, and the manganese content of steel wire for welding certain special purposes is as high as 1.70% to 2.10%.
3. Silicon (Si) is a good alloying agent. Adding an appropriate amount of silicon to steel can improve the yield strength, elasticity and acid resistance of steel; if the content is too high, it will reduce plasticity and toughness. During the welding process, silicon also has good deoxidation ability and forms silicon dioxide with oxygen, but it will increase the viscosity of the slag and easily promote the formation of non-metallic inclusions.
4. Chromium (Cr) can improve the hardness, wear resistance and corrosion resistance of steel. For low carbon steel, chromium is an accidental impurity. The main metallurgical characteristic of chromium is that it is easy to oxidize rapidly to form refractory oxide chromium trioxide (Cr203), thereby increasing the possibility of weld metal inclusions. After chromium trioxide transitions to slag, it can increase the viscosity of the slag and reduce fluidity.
5. Nickel (Ni) has a significant effect on the toughness of steel. Generally, when the low-temperature impact value is required to be high, some nickel is appropriately added.
6. Sulfur (S) is a harmful impurity. As the sulfur content increases, the tendency of hot cracks in the weld will increase. Therefore, the sulfur content in the welding core shall not exceed 0.04%. When welding important structures, the sulfur content shall not exceed 0.03%.
7. Phosphorus (P) is a harmful impurity. The main harm of phosphorus is to make the weld cold brittle. As the phosphorus content increases, the toughness of the weld metal, especially the low-temperature impact toughness, will decrease. Therefore, the phosphorus content in the welding core shall not exceed 0.04%. When welding important structures, the phosphorus content shall not exceed 0.03%.

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