The principle of selecting welding materials is strong matching. Strong nodes and weak members: The strength, plasticity and impact toughness of the deposited metal of the welding material are higher than the minimum values stipulated in the base metal standards. All properties of welded joints (welds and heat-affected zones) are required to meet the minimum values stipulated in the base metal standards. Taking into account the plasticity of the weld. When welding thick plates, welding materials should be selected according to the strength after thickness effect. When the node constraint is large, low-strength welding materials can be used below the plate thickness. Meet impact toughness requirements. We must focus on selecting the toughness of the welding materials so that the toughness of the weld and heat-affected zone meets the standard requirements of steel.
.High strength steel weldability evaluation method
Carbon equivalent calculation and evaluation method. Test evaluation method for maximum hardness in heat affected zone. Critical fracture stress assessment method for pin test.
.Minimum preheating temperature determination method
Crack test control. Determine the minimum preheating temperature based on the crack resistance test of the slope entrance sample. Hardness control. According to the steel with a certain carbon equivalent, the hardness of the heat-affected zone of the fillet weld of different plate thickness joints reaches the corresponding cooling rate (℃), and the welding line energy is determined by looking up the table. The minimum preheating temperature is determined based on the crack sensitivity index, plate thickness range, restraint level, and diffusible hydrogen content of the deposited metal. The minimum preheating temperature is determined based on a specific graph of joint heat input, cooling time and steel material.
.Welding quality control
Control heat input and cooling rate. Control the welding current, voltage, welding speed and cooling time of the deposited metal between ℃ and ℃. Control the mass percentage of carbon, sulfur, phosphorus, nitrogen, hydrogen and oxygen in the weld. Use high-quality alkaline low-hydrogen welding materials and adopt good operating techniques to fully protect the molten pool metal (short arc, limited swing, and stable inclination angle). Stress and deformation control. Use welding methods with high energy density and low heat input, such as gas shielded welding with small line energy, multi-layer and multi-pass welding to reduce the angle and gap of the welding groove, and reduce the amount of deposited metal filling. Use symmetrical grooves, symmetrical and in turns. Long welds should be de-welded in sections or multiple people should be welded at the same time using jump welding to avoid deformation and stress concentration.
In short, for the welding of high-strength steel, we should comprehensively consider its performance requirements based on the strengthening mechanism and supply status of the steel itself, reasonably select welding materials and test methods to evaluate its weldability, and formulate a reasonable welding process. To guide actual welding production. Welding of this steel type should mainly consider taking measures to reduce its tendency to cold crack. During welding, the interlayer temperature and welding line energy should be strictly controlled to prevent the joint from weakening.
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High-strength steel welding construction technology for steel structures