| Blast furnace gas is an important secondary energy in iron-making industry, because of its large output and high calorific value,so this kind of combustible energy could be used as available energy. Because of the hot blast furnace gas high dust content, it must be removed before using. Though the traditional wet dust removal technology is mature, but lot of water,high energy dissipation equipment are major problems must be considered. Even though the emergence of dry dust removal technology has solved the above problems, it cannot remove the acid corrosion gas in blast furnace gas. There is a great corrosion problem in the pipes of transport, which restricted the widespread application of dry dust technology.The use of overlaying technology weld corrosion resistant metal in pipe wall surfacing is an effective method to solve the corrosion of blast furnace gas pipeline. In order to play the most effective role of surfacing layer, decreasing the dilution rate should be necessary.Therefore, this study proposed coupling arc and hot-wire with inert gas welding(Arcingwire GTAW) method to solve this problem. The welding method including two powers, the positive and negative electrodes of one power supply are respectively connected with the base metal and welding torch, which form the main welding arc. Another welding power positive and negative electrode is respectively connected with the consumable electrode and tungsten, forming a side-heating arc. During the welding process, the method can decouple the heat input of base metal and weld surfacing layer, so the dilution rate could be well controlled. Using high speed video camera technology on Arcing-wire GTAW droplet, the transfer behavior were observed and the preheating efficiency were analyzed. The surfacing weld macro morphology and micro-structure were studied.Calculating the different welding procedure specification on the dilution rate and the dilution rate affected weld composition. The corrosion resistance in different dilution rate by weight loss method was studied.The results show that welding procedure parameters affect metal transfer form. When use the moderate wire feed speed, metal transfer frequency, wire feed speed is smaller, thetransition type belong to large drop; when the wire feed speed is bigger, non-droplet transfer were observed. Increasing the welding current and preheating current, metal transfer would be changed. Reducing the side arc voltage, wire end metal cannot melt completely, only a part of metal form droplet transfer. Increasing the length of wire extension, the droplet transfer frequency was decreased. The use of coupling arc to heating wire, the heating efficiency is better than the traditional hot wire GTAW. Although droplet transfer type is not as same as no droplet transfer type of high heating efficiency, but the ability to decouple the wires and welding heat input was leaved.The Inconel625 welding wire is used in the surfacing welding process test on the surface of 20 G by Arcing- wire GTAW. The joint was sound. The separation phenomenon and the surface macroscopic defects such as porosity, slag inclusion and crack were not found. Increasing the weld current, the weld penetration, reinforcement also increase.Increasing the pre-heating current, the shallow depth of molten created. When it reaches 150 A,the deposited metal is obviously spread. Increasing the welding speed, welding layer width and height are reduced. Micro hardness with certain trends, wherein the heat-affected zone hardness>base material hardness>surfacing layer hardness, maximum hardness value can reach 230 HV.For surfacing layer of columnar crystal, no cracks, pores and other defects; surfacing layer and substrate interface with good fusion, no separation phenomenon. The alloy elements of surfacing layer have a uniform distribution and with the increase of dilution rate in the surfacing layer,the content of Cr, Ni, Nb, Mo decrease; on the contrary, Fe increase. The welding process can effectively reduce the dilution rate and the lowest welding can be controlled at below 7%, which inhibit the segregation phenomenon. The welding process can effectively reduce the dilution rate and the lowest value can be controlled at 7% or less, effectively inhibited the segregation phenomenon. The corrosion condition choose nickel base alloy corrosion test standard, 10%of FeCl3 corrosion solution at 50℃. For dilution rate were 12.9%, 10.6% and 7.4% of the samples and 20 G matrix corrosion test for 7 days. Macro level, three groups of samples did not appear obvious corrosion phenomenon, but matrix appeared very obvious pitting phenomenon in the second day.For the resistance to pitting corrosion and chloride ion corrosion, the low dilution rate is better than that of high dilution rate and decrease the corrosion rate. Corrosion rate ratio of the three groups of samples is close to3:1.5:1. Therefore, using Arcing-wire GTAW can reduce dilution rate for the welding layer, improve the composition of surfacing layer, thereby reducing the corrosion rate of surfacing layer. |
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