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Low-alloy high-strength steels can be classified into hot-rolled steel, normalized steel, low-carbon quenched and tempered steel, and medium-carbon quenched and tempered steel, based on their strength levels and heat treatment conditions. When welding low-alloy high-strength steel, the electrode selected has a very important impact on the properties of the weld metal. The selection of welding electrodes for low-alloy high-strength steel is also based on the strength grade of the steel; meanwhile, factors such as the weldability of the base material, the dimensions of the welded structure, the shape of the groove, and the stress conditions are taken into account when choosing the appropriate welding electrodes. When the ambient temperature is low, the cooling rate is fast, and cracks are likely to occur in the welded joint, a welding rod with a strength level one lower than that of the base material should be used. ①The choice of welding electrodes for hot-rolled and normalized steel is primarily based on ensuring that the mechanical properties of the metal after welding, such as strength, plasticity, and impact toughness, are comparable to those of the base material; there is no requirement for the chemical composition of the weld metal to be identical to that of the base material. When welding thick components, to prevent welding cold cracks, the \"low-strength matching\" principle can be applied by using electrodes whose weld metal strength is lower than that of the base material. Welding electrodes such as J606, J607, J707, etc. can be used. ②Electrodes for welding low-carbon quenched and tempered steel: When welding low-carbon quenched and tempered steel, there is a high tendency for cold cracking to occur; therefore, it is particularly important to strictly control the hydrogen content in the weld metal. Therefore, for welding low-carbon quenched and tempered steel, low-hydrogen or ultra-low-hydrogen electrodes should be used. For example: JXXXH, JXXXRH. ③ For welding medium-carbon quenched and tempered steel, electrodes of the low-carbon alloy system should be used. Since medium-carbon quenched and tempered steel has a high carbon content, in order to ensure the plasticity, impact toughness, and strength of the weld metal as well as to improve its crack resistance, it is necessary to use such electrodes and to minimize the levels of sulfur and phosphorus impurities in the weld metal. For components that require heat treatment after welding, it is also necessary to ensure that the chemical composition of the weld metal is similar to that of the base material.