Stainless steel is the main element of Cr is higher than 12% increase, to make steel in the passive state, but also has characteristics of stainless steel. According to the microstructure of stainless steel into ferritic, martensitic, austenitic, austenitic + ferritic and precipitation hardening stainless steel. Austenitic stainless steel at room temperature, the organization is usually pure austenite, there are also some small amount of austenite + ferrite, this small amount of ferrite helps to prevent hot cracking.
(1) as far as possible biphasic tissue weld metal ferrite content of 3-5% or less in control. Because a large number of ferrite dissolved harmful physical S, P impurities.
(2) try to use high quality alkaline drug skin electrodes to limit the weld metal in the S, P, C and other content.
2, intergranular corrosion: According to the chromium depletion theory, weld and heat affected zone heated to 450-850 â„ƒ in the temperature-sensitive zone in the grain boundary precipitation of chromium carbide, chromium depleted grain boundary cause, not the degree of corrosion resistance .
(1) the use of low-carbon or low carbon Welding Electrodes consumables, such as the A002, etc.; using titanium, niobium and other elements of the electrode stabilization, such as the A137, A132 and so on.
(2) by wire or rod to weld into a certain amount of ferrite forming elements, the weld metal into austenite + ferrite phase organization, (general control of ferritic 4-12%) .
(3) reduce the weld pool heat, use a smaller welding current and welding speed faster, speed up the cooling rate.
(4) of the resistance to intergranular corrosion demanding welding conditions for stabilizing annealing after welding
3, stress corrosion cracking: stress corrosion cracking of welded joints in a particular corrosive environment by the tensile stress arising from the delayed cracking phenomenon. Welded joints of austenitic stainless steel to stress corrosion cracking of welded joints is more serious failure mode, showed no plastic deformation of brittle failure.
Stress corrosion cracking prevention measures:
(1) to develop a reasonable forming and assembly processes to minimize the degree of cold deformation, avoid forcing the assembly to prevent all injuries caused during assembly (the assembly of various wounds and burn marks arc will become the SCC crack source, could easily lead to corrosion pits).
(2) a reasonable choice of welding consumables: weld and base metal should be a good match, does not produce any adverse tissue, such as grain coarsening and brittle martensite, etc.;
(3) take appropriate Nickel Alloy Welding Electrodes process: to ensure a good weld, does not produce any stress concentration or pitting defects, such as undercut, etc.; take reasonable welding sequence, reducing the welding residual stress level;
(4) eliminate the stress treatment: post-weld heat treatment, such as fully annealed or annealed after welding; used in difficult to implement post-weld heat treatment or shot peening hammer, etc.
(5) Production management: media control of impurities, such as liquid ammonia medium O2, N2, H2O, etc.; liquefied petroleum gas in H2S; chloride solution O2, Fe3 +, Cr6 +, etc.; corrosion treatment: such as coating, lining or cathodic protection; added inhibitor.
4, low-temperature embrittlement of weld metal: for austenitic stainless steel welded joints at low temperature use, the plastic weld metal toughness is the key issue. At this point, weld metal ferrite in the presence of low-temperature toughness is always worse.
Through the use of pure austenitic welding consumables and adjust the welding process to obtain a single austenitic weld.
5, the welded joints of σ phase embrittlement: weldment to withstand a certain time in the heated to high temperatures in a brittle weld precipitation of σ phase, the entire joint embrittlement, ductility and toughness decreased significantly. σ phase precipitation temperature range of 650-850 â„ƒ. In the high temperature heating process, σ phase mainly formed by the ferrite transformation. The longer the heating time, σ phase precipitation more.
(1) limit in the weld metal ferrite content (less than 15%); ultra-alloy welding materials, namely high nickel welding consumables.
(2) the use of small practices to reduce the weld metal at high temperatures the residence time;
(3) precipitation of σ phase have been when conditions allow for solution processing, the σ phase dissolved in austenite.
E4303, E4313 Nickel Electrode welding material in China's leading product, accounting for 80% of the total production of electrodes around. Recent years, the welding industry are looking for with little or no use of rutile titanium dioxide or by high prices of raw materials to reduce production costs way, sepiolite, clay, pyrophyllite, etc. used in non-metallic mineral aluminosilicate E4303, E4313 welding electrode in, have achieved a certain effect, but not completely smooth and has good plasticity. And sericite overall performance is much better, and help improve the E4303, E4313 welding quality.
1: lamellar mica is potassium aluminum silicate structures for KAl2 [Si3AlO10] (OH, F)
Suitable for welding rod industry, the chemical composition of sericite as follows:
Chemical composition SiO2Al2O3K2OH2OSP
Content (%) 50-6025-307-11 ≤ 5 ≤ 0.03 ≤ 0.03
2: GTS sericite applications and features:
2.1 and sepiolite, clay, pyrophyllite, compared with higher levels of sericite in K2O (pyrophyllite, 7.41%; sericite ,7.5-11%; clay, sepiolite does not contain K2O), and therefore have a lower ionization potential, in the arc burning process, facilitate the provision of conductive ions, so that the arc burning stable.
2.2 GTS sericite S, P low impurity content (S content of 0.015-0.018%), help to reduce the deposited metal in the S, P, reducing its tendency to crack, to improve crack resistance.
2.3 low water swelling (pyrophyllite, 70.5%; sepiolite, 5.2%; titanium dioxide, 32.6%; sericite, 4.3%), medicine for the skin to reduce Welding Electrode Manufacturers crack beneficial.
2.4 adsorbed water content is low (after 110OC × 2h after baking, moisture% is: pyrophyllite, 1.8; clay, 5.2%; sepiolite, 5.8%; titanium dioxide, 2.4%; sericite, 2.5%), can improve its moisture resistance properties, reduce the spread of deposited metal hydrogen content, lower stomatal sensitivity, improve the level of X-ray film scratches.
2.5As was fine scaly, with a certain degree of flexibility, plasticity, increase the welding rod coatings and slip in the powder cylinder flow, pressure applied to improve its performance.
2.6GTS sericite particle size distribution, excluding large particles of foreign impurities in the arc burning does not produce burst, thereby reducing spatter, while reducing the burning of the sound.
Conclusions: GTS sericite is a new drug skin electrode material. It contains 7% -11% K2O, can improve the arc stability, reduce splash, welding process to improve the performance of the production process to solve the electrodes of the electrode drugs often cracking skin problems, E4303, E4313 electrode in applications such as acid recommended ratio of 3% -5%, can improve the coating slip, viscosity, instead of titanium dioxide, reducing the cost of welding rod.