1 to consider the physical properties of weldment material, mechanical properties and chemical composition
Details intensity principle (1) of steel welded structure, general considerations, which are selected to meet the mechanical property requirements of the welding consumables.
(2) For the dissimilar weld joints between low carbon steel and low alloy steel, generally used corresponding to the intensity level lower steel welding consumables.
(3) and the welding heat-resistant stainless steel, in addition to consideration of the strength, but also consider the chemical composition of the weld metal and the chemical composition of the base material mainly close.
(4) When the chemical composition of the base material of carbon or high sulfur, phosphorus and other harmful impurities, should be selected strong crack resistance welding consumables. The low hydrogen type consumables like.
Consider two weldments working conditions and performance
56 (1) in the weldment and subjected to impact loading dynamic load case, in addition to the requirements to ensure the tensile strength, yield strength, the impact toughness and ductility have higher requirements. At this time should use low hydrogen type consumables.
(2) the working weldments in corrosive media, the media must distinguish between species, concentration, temperature and the type of corrosion (general corrosion, intergranular corrosion, stress corrosion, etc.), so as to select a suitable stainless steel welding consumables.
(3) at the weldment by working under conditions of wear, wear is generally required to distinguish between an impact or abrasion, wear or intermetallic abrasive wear, wear or abrasion is at a high temperature and the like at normal temperature. It should also consider whether the work in corrosive media, to select the appropriate welding consumables.
(4) at low temperature or high temperature operating weldments, welding materials should be selected to ensure a low temperature or high temperature mechanical properties.
3 consider the structural characteristics and complexity of the weldment, weld joint type, etc.
56 (1) or a complex shape weldment thickness, due to large internal stress generated in the weld metal shrinkage on cooling, cracks are easily generated. Thus, good crack resistance must welding consumables, such as low hydrogen type electrodes, high toughness electrodes.
(2) for some small linker groove, or tight control of root penetration joints, welding materials should be used with a greater depth of penetration or the penetration capability.
(3) due to certain conditions the welded portion difficult to clean when clean, should be considered for selection of rust, scale and oil not sensitive consumables, such as acid electrode, in order to avoid defects such as pinholes.
Considering the spatial position of the welding seam 4
Detail: Some welding consumables is only applicable to a certain position, poor welding effect other locations, some of the consumables can be various welding positions, the position of the weld features to be considered when choosing
5 to consider the working conditions of welding, the operating environment
Information (1) the case where no DC welder, welding materials should be used in DC to AC.
(2) some steels (e.g. pearlitic heat resistant steel) the need for post-weld stress relief heat treatment, but the device itself or the constraints can not be performed by structural constraints, should be used with a different chemical composition of the base metal of welding consumables (e.g. austenitic stainless steel welding consumables), the heat treatment after welding can be free.
(3) should be based on the construction site conditions, such as field operations, welding consumables environment like a reasonable choice.
(4) where the acidic and basic welding electrodes have to meet, in view of the high alkaline electrode preparation technique and construction requirements, it should be acidic electrodes.
6 to consider the economics of welding
Details (1) in ensuring the performance of the premise, try to use cost-effective welding consumables.
(2) There are different requirements for primary and secondary weld performance, using different welding consumables, not one-sided pursuit of comprehensive performance welding consumables.
7 Consider the welding efficiency
Detail: amount of welding work structure, conditions should maximize the use of welding consumables **, such as wire, rod iron, stainless steel electrode efficiency and the like.
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