Compared with stainless steel, a nickel alloy having a higher weld hot cracking susceptibility, such as solidification cracking, liquation cracking are likely to occur, and easy to produce at a crater crater cracks. Nickel and nickel alloy welding generally does not produce cold crack prone to hot cracking (solidification cracking). Nickel and sulfur, phosphorus and NiO can form low melting point eutectic, nickel and nickel alloy welds the metal solidified often coarse dendritic austenite crystals, low melting point impurities easier to concentrate at the grain boundaries, grain solidification shrinkage stress not completely solidified grain boundary and the effect of the welding stress, low-melting substance (crystal film) can easily be pulled crack formation of thermal cracks. The sulfur content in the welding material is more sensitive to thermal crack formation plays a key role. General nickel and Nickel Alloy Welding Wire in the sulfur content of less than 0.01% to 0.03%. The welding material adding manganese to form manganese sulfide and sulfur, nickel and sulfur to generate the amount of the low-melting eutectic of reducing grain boundary, can significantly reduce the sensitivity of weld hot cracking is formed. ≤ 3.0% manganese is sometimes added to the wire. Welding Materials should reduce the phosphorus content the the wire deposited metal is generally controlled phosphorus content less than 0.015% to 0.03%. Improve the manganese content can improve the solubility of phosphorus in the matrix, the grain boundary can also reduce the number of the low-melting eutectic of the nickel and phosphorus is formed, reducing the sensitivity to hot cracking. Nickel alloy containing chromium, molybdenum, aluminum, titanium, niobium, etc. may be in the weld starting modificator role in grain refinement and disrupt the direction of the dendrite. Aluminum, titanium, can play a deoxidizing effect, to reduce the amount of NiO, these it is advantageous to prevent the generation of heat cracks. Intergranular liquid film is caused by the nickel alloy single-phase austenitic weld solidification cracking the main reason. S, P, Pb, Zn, etc. are the main elements of the low-melting liquid film cause intergranular. Thus, during the welding process must be strictly limit the ingress of harmful impurities, to avoid or reduce the intergranular liquid film generated. For this reason, before the welding, it is necessary to rigorous cleaning the base material and the wire, to prevent the harmful elements in the transition to the weld zone. When the weld line can be excessive, due to the large heat input, a low melting point in the grain boundary phase being formed by melting the liquation cracking. Therefore, welding nickel alloys should be chosen low line energy.
Nickel molybdenum based Welding Alloys in the preparation before welding and welding protection how do Prior to welding, grinding on a metal surface the welding groove on both sides 25mm width to remove the oxidized color, and washed with acetone to remove grease moisture and other contaminants on the 25mm width and wire welding groove on both sides; must be thoroughly to remove the oxide film; should put an end to useless welding consumables, the welders dirty clothes hazardous substances pollution. Under the the argon protection of the hot end of the molten pool and Welding Wire process has always been at the nozzle, the temperature above 300 â„ƒ the weld should use drag hood protection. The large torch nozzle in order to maximize the shielding of the molten pool in the protection of air flow into, should always hot end of the wire to stay in the bath. Cut wire ends before re-arcing wire end has been oxidized. The the multilayer welding, each layer to be used for drag cast under the protection of high-temperature weld. The protective effect of good or bad judgment can weld surface color silver white.