High temperature, high pressure and the pressure vessel and run in the presence of hydrogen under the conditions, the corrosion of the surface of the inner wall of the reactor in order to avoid the desulfurizing reaction produce large amounts of H2S and when the reactor is stopped running, the stress caused by the of polythionic acid (H2SXO6) corrosion cracking, corrosion-resistant material in the inner wall of the reactor are usually surfacing. Molybdenum niobium as the main strengthening element of solid solution strengthening Types Of Welding Wires nickel base wrought superalloy 625, having excellent corrosion resistance and oxidation resistance, from cryogenic to 980 â„ƒ have high strength, toughness, fatigue strength and oxidation resistance. In the atmosphere, natural water, sea water, neutral salts and alkali weak medium is essentially non-corrosive, more demanding medium, to oxidizing acid tolerant and resistant to reducing acid medium. Excellent resistance to intergranular corrosion, stress corrosion, pitting and crevice corrosion. Both require high corrosion resistance, but also meet the high temperature corrosion resistant alloy, has been widely used in the manufacture of pressure vessels. A large area of the inner wall of the container can be used to strip cladding technology, took over the inner wall surfacing, small diameter Flux Cored Welding Wire the surfacing welding process (FCAW) has to adapt to the current and voltage range high deposition efficiency, productivity has improved significantly, the economy is fine; welding conditions to achieve relatively easy, easy semi-automatic and automatic welding; slag detachability good weld appearance; splash is small, excellent arc stability, high pass rate, etc. and are widely used in the production.
Flux Cored Welding Wire powder volume in the metal tube inside the wire, efficient shipyard welding materials are widely used in recent years and it combines the advantages of the electrodes and solid wire, low spatter, stable welding arc soft, all-position welding, continuous welding.
The role of the powder: 1) the arc stabilization Na, K and other ingredients of Na +, the ionization of K +, etc., in the welding process has played the role of the steady arc. (Na, K, etc.) 2) mechanical properties of the stabilized metal cladding adding deoxidizing elements such as Mg, Al, Si, Mn, and oxygen in the deposited metal, can be eliminated prevent welding the generation of holes, thus improving the strength and toughness of the deposited metal. 3) to promote the formation of alloy Si, Mn, Ni, Cr, Mo and other elements to promote the formation of the fused metal alloy, to improve the characteristics of the deposited metal, Si and Mn element is able to maintain appropriate strength and toughness of the deposited metal, Ni is possible to improve the impact of the low-temperature metal toughness, Cr and Mo can improve the crack resistance of the deposited metal. 4) the formation of welding slag Powder in the welding process to produce a large number of the welding slag, the adhesion and solidification of the surface of the weld metal, to prevent the cold compaction of the metal after the welding step, help exclude hydride, and thereby improve the basic performance of the weld metal. 5) generates a protective gas FCW component of the product, part of the powder gas is generated in welding, able to guarantee the stability of the arc in the welding process, to prevent the occurrence of nitridation and oxidation of the welded portion, and the protection of the chemical composition of the deposited metal and to improve its mechanical properties.
The classification of the product Flux cored wire products, depending on the internal powder ingredients into titanium and alkali-two, the titanium type due to the addition of more TiO2 ingredients with enabling weld appearance, all-position welding workability characteristics. However, compared to the base type poor impact toughness and crack resistance. The metal titanium representatives product is the SF-71, Supercored71 the representatives of alkali-type products such as Supercored 70B. After welding with the other methods can be classified according to the presence or absence of the weld slag, slag-type, metallic powder type, slag-type features in the welding process because the resulting welding slag may be used for all-position welding, metal powder type produce small amounts of welding slag, can only be applied in the downward welding. Most of the flux cored wire products belong to the slag and metal powder products SF-70MX Supercored 70NS. Protective gas Flux cored wire products, many using 100% CO2 and 80% A r +20% gas mixture to protect the gas, there are a lot of products do not use protective gas flux cored wire products must use the specified protective gas, if you are using a non-specified protective gas cause changes in the composition of the deposited metal alloy, causing changes in the mechanical properties of the deposited metal, resulting in lower welding performance (of course workability than using the specified the low protective gas) using CO2 and A r protection gas, when welding with a solid wire, a welding of the welding wire form shown in Figure 3, the shape of the arc as shown in Figure 4, A r protective gas, there SPRAY, the greater the arc, then, there will be poor concentration, welding slit width, melting into reducing the phenomenon.
Flux-cored and solid wires The cored wire although the use of solid wire welding method, but has the following advantages and disadvantages compared with the solid wire. .
Advantage Welding speed. Downward welding, horizontal welding, flux-cored wire speed faster than the solid wire welding speed of about 10%, especially vertical welding (Vertical) and overhead welding (over head) when, according to the role of the powder can be welding using a high current, it can be increased by more than twice the speed. 2 can be all-position welding Solid wire welding in the horizontal or on high welding techniques require welders to weld the time, will produce a large number of spatter, and therefore only suitable for sheet metal welding, but the flux-cored the full welding slag, covering welding parts So for all position welding. 3 small splash Flux-cored and solid wires compared spatter small, continuous use will not clog the torch mouth. 4 good workability Soft flux-cored arc welding workability, and ease of operation. Disadvantages: A deposition efficiency is low cored wire after the welding because produce large amounts of welding slag deposition efficiency of approximately 88%, while the solid wires because there is no weld slag deposition efficiency of approximately 95% 2. Soot Flux-cored wire during the welding process relatively soot 3. Expensive Kg units, flux cored wire prices, although more expensive, but if calculated from the point of view of improving productivity, but has also managed to save costs.