Basic principles of welding consumables


 Basic principles of welding consumables


1. Consider the physical properties, mechanical properties and chemical composition of the weldment material:

    (1) For the welding of structural steels, generally consider the principle of equal strength and select the welding consumables that meet the mechanical properties of the joints.

    (2) For the dissimilar steel welded joints between low carbon steel and low alloy steel, the corresponding welding materials for steels with lower strength grades are generally selected.

    (3) For the welding of heat-resistant steel and stainless steel, in addition to considering the strength, it is also considered that the main chemical composition of the weld metal is close to the chemical composition of the base metal.

    (4) When the harmful components such as carbon or sulfur and phosphorus in the chemical composition of the base metal are high, the welding material with strong crack resistance should be selected. Such as low hydrogen type welding consumables.

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2. Consider the working conditions and performance of the weldment:

    (1) In the case of dynamic load and impact load, the weldment has higher requirements on impact toughness and plasticity in addition to the requirements of tensile strength and yield strength. Low hydrogen type welding consumables should be used at this time.

    (2) When the weldment is working in corrosive media, it is necessary to distinguish the type of medium, concentration, working temperature and corrosion type (general corrosion, intergranular corrosion, stress corrosion, etc.) to select a suitable stainless steel welding consumable.

    (3) When the weldment is working under the condition of wear, it must distinguish between general wear and impact wear, whether it is wear between metal or abrasive, whether it is worn at normal temperature or worn at high temperature. Consideration should also be given to working in corrosive media to select the right surfacing consumables.

    (4) Welding consumables working at low or high temperatures should be selected from welding consumables that guarantee low temperature or high temperature mechanical properties.

3. Consider the complexity and structural characteristics of the weldment, the type of welded joints, etc.:

    (1) Weldments of complex shape or large thickness are prone to cracks due to the large internal stress generated by the weld metal during cooling shrinkage. Therefore, it is necessary to use welding materials with good crack resistance, such as low-hydrogen welding rods and high-toughness welding rods.

    (2) For some joints with small groove or joints with strict control of root penetration, the welding material with large penetration or penetration capability should be used.

    (3) When it is difficult to clean certain welded parts due to conditions, it is necessary to consider the use of welding consumables that are insensitive to rust, scale and oily reactions, such as acid electrodes, to avoid defects such as pores.

    4. Consider the spatial position of the weld:

    Some welding consumables are only suitable for welding at a certain position. The welding at other locations is inferior. Some welding consumables can be welded at various positions. The characteristics of the welding position should be considered when selecting:




5. Consider the working conditions and operating environment of welding:

    (1) Where there is no DC welder, the AC and DC welding consumables should be used.

    (2) Some steel materials (such as pearlitic heat-resistant steel) need to be post-weld stress-relieving heat treatment, but when the equipment conditions are limited or the structure is limited and cannot be carried out, the welding material with different chemical composition of the base metal should be selected (such as Austenitic stainless steel welding consumables, can avoid post-weld heat treatment.

    (3) The welding consumables should be reasonably selected according to the construction site conditions, such as field operation and welding work environment.

    (4) Where acid electrode and alkaline electrode can be satisfied, acid electrode should be used as much as possible in view of the high requirements of operation technology and construction preparation

 6. Consider the economics of welding:

    (1) Under the premise of ensuring the performance of use, try to use cost-effective welding consumables.

    (2) For primary and secondary welds with different performance requirements, different welding consumables may be used, and the overall performance of the welding consumables shall not be pursued.

 7. Consider welding efficiency:

    For structures with large welding workload, high-efficiency welding consumables such as welding wire, iron powder welding rod, high-efficiency stainless steel welding rod, etc. should be used as much as possible.

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