Stainless Steel Supplier Corporation Limited
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Add Time:2021-06-01 Hits:41
1. The second generation 2205 stainless steel sheets and plate is usually called standard 2205 stainless steel sheets and plate. Its composition is characterized by ultra-low carbon and nitrogen content. Its typical composition is 22% Cr + 5% Ni + 0.17% n. compared with the first generation 2205 stainless steel sheets and plate, 2205 further improves the nitrogen content, It can enhance the function of stress corrosion resistance and pitting corrosion resistance in acidic medium with high chloride ion concentration. Nitrogen is a strong austenitic constituent element. The addition of nitrogen to 2205 stainless steel sheets and plate can not only improve the strength of steel, but also inhibit the segregation and delay of carbides.
2. Arrangement features: 2205 stainless steel sheets and plate in the greenhouse solid solution of austenite and ferrite accounted for about half, both two-phase arrangement characteristics. It retains the characteristics of ferritic stainless steel, such as small guide diameter, pitting corrosion resistance, crevice and chloride stress corrosion resistance, and has the advantages of austenitic stainless steel, such as good resistance, low brittle transition temperature, intergranular corrosion resistance, good mechanical and welding functions.
3. The results show that 2205 stainless steel sheets and plate is nearly twice as strong as austenitic stainless steel in terms of function, and can save data under the same pressure level. The coefficient of linear thermal expansion is lower than that of austenitic stainless steel and close to that of low carbon steel. It makes the connection between 2205 stainless steel sheets and plate and carbon steel more suitable, which has great engineering significance. Forging and cold stamping are not as good as austenitic stainless steel.
4. Weldability: 2205 stainless steel sheets and plate2205 has excellent weldability, and the sensitivity of welding cold crack and hot crack is small. Generally, preheating is not required before welding and heat treatment is not required after welding. Because of the high nitrogen content, the single-phase ferrite tendency of HAZ is small. When the welding data is selected reasonably and the welding line energy is controlled properly, the welded joint has excellent induction function.
Hot crack: the sensitivity of hot crack is much smaller than that of austenitic stainless steel. This is because the content of nickel is not high, the impurities which are easy to form low melting point eutectic are very few, and it is not easy to produce low melting point liquid film. In addition, there is no risk of rapid grain growth at high temperature.
6. Heat affected zone embrittlement: the primary problem of 2205 stainless steel sheets and plate welding is not in the weld, but in the heat affected zone. Because under the effect of welding thermal cycle, the heat affected zone is in the fast cooling non-equilibrium state, after cooling, more ferrite is always retained, and then the corrosion tendency and hydrogen induced cracking (brittleness) sensitivity are increased.
7. Welding metallurgy: in the welding process of 2205 stainless steel sheets and plate, a series of changes take place in the arrangement of weld metal and heat affected zone under the effect of thermal cycle. At high temperature, all 2205 stainless steel sheets and plates are arranged by ferrite, and austenite is separated during cooling. The amount of austenite separated is affected by many factors.
8 request for comparative example: the mechanical function and corrosion resistance of 2205 stainless steel sheets and plate welded joint depend on whether the welded joint can adhere to the proper comparative example. Therefore, the welding is carried out around how to ensure its two-phase arrangement. When the content of ferrite and austenite is close to 50%, the function is better and close to that of base metal. Changing this connection will reduce the corrosion resistance and mechanical function of 2205 stainless steel sheets and plate welded joint. The best ferrite content of 2205 stainless steel sheets and plate2205 is 45%. If the ferrite content is too low, the strength and stress corrosion cracking resistance will be reduced; Too high ferrite content more than 75% will also damage the corrosion resistance and impact resistance
9. Influencing factors of comparative example: the equilibrium relationship between ferrite and austenite in welded joint is affected not only by the content of alloy elements in steel, but also by filler metal, welding thermal cycle and maintenance gas.
10. Influence of alloy elements: according to research and many experiments, nitrogen content in base metal is very important. Nitrogen plays an important role in ensuring a satisfactory amount of austenite in weld metal and pwhaz. Nitrogen and nickel are the same elements that constitute austenite valence and expand austenite, but nitrogen is also more talented than nickel, which can avoid single-phase ferrite after welding and prevent the separation of harmful metal phases.
Because of the effect of welding thermal cycle, when the composition of self fusion welding or filler metal is the same as that of base metal, the ferrite content of weld metal increases sharply, even presents pure ferrite arrangement. In order to restrain the excessive addition of ferrite in the weld, the welding trend of 2205 stainless steel sheets and plate is to select the weld metal with austenite predominance. Generally, two ways are adopted, i.e. improving nickel in welding data or adding nitrogen. Generally, the nickel content is 2% - 4% higher than that of the base metal. For example, the nickel content of 2205 filler metal is as high as 8% - 10%. The filling data with nitrogen is more stable than that with nickel only. However, nitrogen addition can not only delay the separation of metals, but also improve the strength and corrosion resistance of weld metal. Now, the filling data are usually based on the progress of nickel, and then participate in the base metal with appropriate nitrogen content.
11. As for 2205 stainless steel sheets and plate2205, Sandvik 22.8.3l (er2209) welding wire is selected for TIG welding, and avesta2205ac / DC welding rod is selected for shielded metal arc welding. These characteristics of 2205 stainless steel sheets and plate2205 and welding data in alloy elements provide a certain scale for the selection of welding technical parameters, i.e. welding line energy, which is very beneficial to welding. 12. Thermal cycle: the biggest feature of 2205 stainless steel sheets and plate welding is that the welding thermal cycle has an impact on the arrangement of the welded joint. No matter the weld or the hot film star area, there will be phase transformation, which has a great impact on the function of the welded joint. Therefore, multi-layer and multi pass welding is advantageous. The subsequent weld bead has heat treatment effect on the previous weld bead, and the ferrite in the weld metal further transforms into austenite, which becomes the two-phase arrangement dominated by austenite; The austenite phase in the heat affected zone of the adjacent weld also increases correspondingly, and the ferrite grain can be refined, the separation of carbide and nitride from the intragranular and grain boundary can be reduced, and then the two functions of all welded joints can be improved obviously. It is also because of the influence of welding thermal cycle that 2205 stainless steel sheets and plate should be welded with the weld bead touching the medium, which is opposite to the requirement of austenitic stainless steel welding sequence.
13. The influence of technical parameters: the number of welding technology, that is, welding line energy, also plays a key role in the balance of two-phase arrangement. Because 2205 stainless steel sheets and plate is 100% ferrite at high temperature, if the linear energy is too small, the cooling rate of heat affected zone is fast, and the austenite can not separate out too much ferrite before it is supercooled in greenhouse. If the linear energy is too large, the cooling rate is too slow, although enough austenite can be obtained, it will also cause the growth of ferrite grains and the formation of ferrite in the heat affected zone σ The separation of harmful metal phase leads to joint embrittlement. In order to avoid the above situation, the best way is to control the welding line energy and interlayer temperature, and use filler metal.
14. Influence of maintenance Gas: during TIG welding, 2% nitrogen can be added in argon to avoid nitrogen loss due to dispersion on weld surface, which is helpful to balance ferrite and austenite.
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