Consider the physical properties, mechanical properties, and chemical composition of weldment materials
(1) For the welding of structural steel, the principle of equal strength is generally considered, and the welding consumables that meet the requirements of the mechanical properties of the joint are selected.
(2) For dissimilar steel welded joints between low carbon steel and low alloy steel, generally choose welding consumables corresponding to steels with lower strength grades.
(3) For the welding of heat-resistant steel and stainless steel, in addition to considering the strength, it is also necessary to consider that the main chemical composition of the weld metal is close to that of the base metal.
(4) When harmful impurities such as carbon or sulfur and phosphorus are high in the chemical composition of the base metal, welding consumables with strong crack resistance should be selected. Such as low hydrogen welding consumables, etc.
Consider the working conditions and performance of the weldment
(1) When the weldment is subjected to dynamic load and impact load, in addition to ensuring tensile strength and yield strength, it has higher requirements for impact toughness and plasticity. At this time, low-hydrogen welding consumables should be used.
(2) When the weldment works in a corrosive medium, it is necessary to distinguish the type, concentration, working temperature and corrosion type (general corrosion, intergranular corrosion, stress corrosion, etc.) of the medium, so as to select the appropriate stainless steel welding material.
(3) When the weldment works under the condition of wear, it is necessary to distinguish whether it is general wear or impact wear, whether it is intermetallic wear or abrasive wear, whether it is worn at room temperature or at high temperature, etc. It should also be considered whether to work in a corrosive medium to select suitable surfacing welding consumables.
(4) For welding parts working at low temperatures or high temperatures, welding consumables that can ensure low-temperature or high-temperature mechanical properties should be selected.
Consider the complexity and structural characteristics of the weldment, the type of welded joints, etc.
(1) Weldments with complex shapes or large thicknesses are prone to cracks due to the large internal stress generated by the weld metal during cooling and shrinkage. Therefore, it is necessary to use welding materials with good crack resistance, such as low-hydrogen electrodes and high-toughness electrodes.
(2) For some joints with small grooves, or joints with strict penetration control at the root, welding consumables with larger penetration depth or penetration capability should be selected.
(3) When it is difficult to clean some welding parts due to the limitation of conditions, the selection of welding materials that are not sensitive to rust, oxide scale and oil pollution, such as acid electrodes, should be considered to avoid defects such as pores.
Consider the spatial location of the weld
Some welding consumables are only suitable for welding in a certain position, and the effect of welding in other positions is poor. Some welding consumables can be welded in various positions. The characteristics of the welding position should be considered when selecting
Consider welding working conditions and operating environment
(1) When there is no DC welding machine, welding materials for both AC and DC should be selected.
(2) Some steels (such as pearlitic heat-resistant steel) need to be subjected to post-weld stress relief heat treatment, but when it cannot be carried out due to the limitations of equipment conditions or its own structure, welding materials with different chemical compositions from the base metal should be selected (such as Austenitic stainless steel welding consumables), can be exempted from post-weld heat treatment.
(3) Welding consumables should be selected reasonably according to the construction site conditions, such as field operation and welding work environment.
(4) In the place where both the acid electrode and the basic electrode can be satisfied, in view of the high requirements on operation technology and construction preparation of the basic electrode, the acid electrode should be used as far as possible.
Consider the economics of welding
(1) On the premise of ensuring performance, try to use cost-effective welding consumables.
(2) For primary and secondary welds with different performance requirements, different welding consumables can be used, and do not unilaterally pursue the overall performance of the welding consumables.
Consider welding efficiency
For structures with large welding workloads, high-efficiency welding materials, such as welding wire, iron powder welding rods, and efficient stainless steel welding rods, should be used as far as possible.