Austenitic Stainless Steel Electrode Selection
(1) Point 1
Generally speaking, the selection of the electrode can refer to the material of the base metal, and select the electrode with the same or similar composition as the base metal. Such as: A102 corresponds to 0Cr18Ni9, A137 corresponds to 1Cr18Ni9Ti.
(2) Point 2
Since the carbon content has a great influence on the corrosion resistance of stainless steel, the stainless steel electrode whose carbon content of the deposited metal is not higher than that of the base metal is generally selected. Such as 316L must use A022 electrode.
(3) Point 3
The weld metal of austenitic stainless steel shall ensure mechanical properties. This can be verified by welding procedure qualification.
(4) Point 4 (Austenitic heat-resistant steel)
For heat-resistant stainless steel (austenitic heat-resistant steel) working at high temperature, the selected electrode should mainly meet the hot crack resistance of the weld metal and the high temperature performance of the welded joint.
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1. For austenitic heat-resistant steels with Cr/Ni≥1, such as 1Cr18Ni9Ti, etc., austenitic-ferritic stainless steel electrodes are generally used, and it is advisable that the weld metal contains 2-5% ferrite. When the ferrite content is too low, the crack resistance of the weld metal is poor; if it is too high, σ embrittlement phase is easily formed during long-term use at high temperature or heat treatment, resulting in cracks. Such as A002, A102, A137. In some special applications, when all austenitic weld metal may be required, such as A402, A407 electrodes, etc. can be used.
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2. For stable austenitic heat-resistant steels with Cr/Ni<1, such as Cr16Ni25Mo6, etc., it is generally necessary to increase the Mo, W, Mn in the weld metal while ensuring that the chemical composition of the weld metal is approximately similar to that of the base metal. The content of such elements can improve the crack resistance of the weld while ensuring the thermal strength of the weld metal. Such as using A502, A507.
(5) Point 5 (corrosion-resistant stainless steel)
For corrosion-resistant stainless steel working in various corrosive media, the electrode should be selected according to the medium and working temperature, and its corrosion resistance should be ensured (do the corrosion performance test of welded joints).
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5.1. For the medium with the working temperature above 300℃ and strong corrosiveness, the electrode containing Ti or Nb stabilization element or ultra-low carbon stainless steel must be used. Such as A137 or A002 and so on.
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5.2. For the medium containing dilute sulfuric acid or hydrochloric acid, stainless steel electrodes containing Mo or Mo and Cu are often used, such as: A032, A052, etc.
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5.3. For equipment with weak corrosion or only to avoid rust pollution, stainless steel electrodes without Ti or Nb can be used. In order to ensure the stress corrosion resistance of the weld metal, superalloyed welding consumables are used, that is, the content of corrosion-resistant alloying elements (Cr, Ni, etc.) in the weld metal is higher than that of the base metal. For example, use 00Cr18Ni12Mo2 type welding materials (such as A022) to weld 00Cr19Ni10 weldments.
(6) Point 6
For austenitic stainless steel working under low temperature conditions, the low temperature impact toughness of the welded joint at the service temperature should be guaranteed, so pure austenitic electrodes are used. Such as A402, A407.
(7) Point 7
Nickel-based alloy electrodes are also available. For example, Mo6 type super austenitic stainless steel is welded with nickel-based welding consumables with Mo up to 9%.
(8) Point 8: Selection of electrode coating type
1. Since the dual-phase austenitic steel weld metal itself contains a certain amount of ferrite, it has good plasticity and toughness. From the perspective of weld metal crack resistance, the basic coating and the titanium calcium type coating electrode are compared. The difference is not as significant as for carbon steel electrodes. Therefore, in practical applications, more attention is paid to the welding process performance, and most of the electrodes with coating type code 17 or 16 (such as A102A, A102, A132, etc.) are used.
2. Only when the structural rigidity is very high or the crack resistance of the weld metal is poor (such as some martensitic chromium stainless steel, pure austenitic chromium-nickel stainless steel, etc.), the choice of coating code 15 can be considered. Basic coated stainless steel electrodes (such as A107, A407, etc.).
Summary
To sum up, the welding of austenitic stainless steel has its unique characteristics, and the selection of welding rods for austenitic stainless steel is particularly noteworthy. It has been proved through long-term practice that the above measures can be used to achieve different welding for different materials. Methods and electrodes of different materials, stainless steel electrodes must be selected according to the base metal and working conditions (including working temperature and contact medium, etc.). It has a good guiding significance for us, so that it is possible to achieve the expected welding quality.
