A: 1 nickel and nickel alloy welding Nickel-based alloys are divided into four major series: (1) Inconel of Inconel (Ni-Gr-Fe-based) (2) Monel Monel of (Ni-Cu series) (3) Yin Keluo according Incoloy (Fe-Ni--Gr lines) (4) Hastelloy Hastlloy (Ni-Mo or Ni-Gr-Mo series) 2 weldability analysis (1) The most common defect of nickel and nickel alloy welding hot cracking, mainly due to a lower melting point metal eutectic material and non-metal eutectic material is nickel and iron binary eutectic material. Especially sulfur, phosphorus eutectic melting point than the nickel-iron is much lower (Ni-S 645 ℃, Ni-P is 880 ° C), a low melting eutectic material of the liquid film remaining in the grain boundary region in the weld crystallization, while linear expansion coefficients of nickel and nickel alloys, welding easy to produce greater stress, low melting point eutectic liquid film was easy to produce the effect of shrinkage stress cracking weld crystallization. (2) nickel and nickel alloys, pure nickel, Monel and other alloys, the solid-liquid phase temperature spacing is small, low liquidity in the rapid cooling crystallization conditions, the gas is too late to escape easily weld blowholes. Nickel and nickel alloy welding small line energy, reduce the temperature between layers, to speed up the cooling rate of the weld, completely clear before welding wire, the base metal groove at oil, dirt, and strictly control the sulfur in the base metal welding consumables, phosphorus content, in order to prevent the generation of cracks, pores. 3 welding method GTAW welding of nickel and nickel alloys commonly used hand SMAW, melting the inert gas shielded welding and submerged arc welding method can be used. 4 welding consumables And 4.1 welding consumables selection principles 4.1.1 with iron-nickel alloy, nickel alloy welding material welding should be selected and the parent alloy system, in the absence of corrosion resistance can require different welding materials and base metal alloy systems can also be used, but should ensure that the joints have the performance of the design requirements. 4.1.2 heterogeneous iron-nickel alloy, nickel alloy of chrome-nickel austenitic steels dissimilar welded joints of welding materials, the choice should consider the following factors: (1) the strength of the weld (including high temperature lasting strength) corrosion resistance. (2) the difference in coefficient of linear expansion after working for a long time under high temperature, may be generated by a permanent change in the volume. (3) welding cracks, porosity sensitivity. 4.2 commonly used nickel-iron alloy, nickel alloy welding consumables used refer to Table 2 4.3 commonly refer to Table 3 dissimilar nickel alloy welding consumables selection 4.4 welding consumables drying (1) use of electrodes according to the electrode product manual, quality certificate, or the requirements of the welding process guidance book for drying. (2) after drying of the electrode should be stored at 100 ° C thermostat box welder recipients should use insulation tube, such as a collar for more than 4h, should be re-baking, but shall not be more than twice the number of repeat baking. (3) recommended the electrode drying temperature. Of 4.5 pairs welding material requirements (1) welding of nickel and nickel alloy pipe welding electrodes, wire, flux, shielding gas, the electrode should be factory certification and quality certificate. (2) the characteristics of the data on the quality of welding certificate objection or doubt its quality should be the appropriate technical standards necessary reinspection. (3) welding materials storage, protection should comply with the of welding materials quality control procedures and requirements of relevant standards JB/T3223-96. (4) tungsten arc welding should adopt the cerium tungsten, and in accordance with the provisions of GB4191 "inert gas shielded arc welding and plasma welding cutting cerium tungsten electrode. (5) welding of nickel and nickel alloys used the argon purity should not be less than 99.99%. (6) with argon welding pipes should adopt the plastic hose should not use rubber hose, hose or other hygroscopic materials. 5 welding environment Nickel and nickel alloy welded construction, environmental conditions should meet the following requirements: (1) The ambient temperature of not less than 0 ℃. (2) hand arc wind speed of not more than 8m / s, the TIG when the wind speed is not greater than 2 m / s. (3) not more than 90% relative humidity. (4) non-rain and snow. (5) when the environmental conditions do not meet the above requirements, should take effective protective measures before welding. 6 Preparation for construction 6.1 Construction specification standards Petrochemical chrome-nickel austenitic steels, iron-nickel alloy and nickel alloy pipe welding procedures SH/T3523 site equipment industrial pipe welding engineering construction and acceptance "GB50236" nickel and nickel alloy electrode "GB/T13814" nickel and nickel alloy wire "GB/T15620 6.2 welding procedure qualification and welders perform standard Welding procedure qualification and welder qualification test implementation of field devices, industrial pipe welding engineering construction and acceptance specifications "GB50236 or petrochemical chrome-nickel austenitic steels, iron-nickel alloy and nickel alloy pipe welding procedures" SH3523 provisions. Welding procedure qualification and welders project can cover welding products. 6.3 according to the design documents, relevant standards and welding procedure qualification, and the preparation of the welding process instructions. 7 welding process 7.1 trimming (1) trimming groove, blunt edge on both sides of the weld 30mm range. (2) weld oxide film with a rasp, grinding wheel to clean up. (3) the weld clean-up of dirt, grease, paint application, acetone, lye, or special synthetic agent. 7.2 welding Notes 7.2.1 Welding guarantee good penetration and fusion of the premise, as far as possible in the process parameters within a small welding line energy, short arc, not swing or small swing operation. 7.2.2 When the thick weldment need multi-pass welding shall meet the following requirements: (1) In addition to the rest of the backing weld outer solder layer should adopt a multi-pass welding. (2) the temperature of the layer should be less than 100 ° C. (3) each layer every after welding should be the elimination of the weld surface of the slag, and the elimination of all surface defects. (4) layers of the welded joints of the Road to stagger. 7.2.3 using solid wire or filler wire tungsten arc welding, weld the back filled with argon, pipe the whole or partial argon two methods can be used to implement within the protection, within the protective measures, and shall meet the following requirements : (1) the beginning of the tube filled with argon flow may be appropriate to increase, to confirm that the air in the tube completely ruled out before welding. (2) welding filled with argon flow can be gradually reduced to avoid higher argon gas pressure caused by the back seam forming within or root incomplete penetration. 7.2.4 tungsten arc welding, the heated end of the wire should always be under the protection of the argon. To strengthen the protective effect in the home of the rear side of the tip auxiliary to transport protective gas drag cover. 7.2.5 weldment surface non arc abrasions, and non-arc weldment surface, ending arc. 7.2.6 welding power supply ground connection to the weldment shall direct contact with the workpiece, the transition should be used with the same material, the material of the weldment connection to avoid iron contamination. 7.2.7 Welding shall ensure the quality of the arc with the closing arc, the closing arc crater fill. 7.2.8 welding when diameter is small and hot cracking tendency larger weld material, you should take the weld on both sides mounted cooling copper block, or Sassafras swab measures weld on both sides with cold water, ethanol, to reduce the weld The high-temperature residence time, to accelerate the cooling rate of the weld. 7.2.9 Welding is completed must be timely to the surface of the weld slag and spatter around, splash material clean. 7.2.10 welded construction to avoid pollution, should be made of stainless steel hammer, stainless steel wire brush, dedicated grinding wheel. 7.3 welding parameters Different series of nickel and nickel alloy welding parameters are slightly different