1, the power density. Laser processing power density is the most critical parameters. The higher power density, in the microsecond time range, the surface can be heated to the boiling point, a large amount of vaporization. Therefore, high power density for the material removal process, such as drilling, cutting, carving favorable. For the lower power density, surface temperature reaches the boiling point to go through a few milliseconds before vaporization at the surface, the bottom to the melting point, easy to melt to form a good weld. Therefore, Welding Electrode in conduction, the power density in the range of 104 ~ 106W/cm2. 2, the laser pulse waveform. Laser pulse in the laser welding is an important issue, especially for sheet welding is more important. When high-intensity laser beam radiation to the surface, the metal surface will be 60 to 98% reflected laser energy is lost, and the reflectivity change with surface temperature. During a laser pulse, the metal is highly variable reflectivity. 3, the laser pulse width. Pulse width is one of the important parameters of laser welding, it is both material removal and material different from important parameters of melting, but also determine the cost and size of processing equipment, the key parameters. 4, away from the coke on the welding quality. Laser welding often requires a certain amount of fuss from, because the laser beam focus at the center of power density is too high, to evaporate into the hole. Leave the laser focus of the plane, relatively uniform power density distribution. Defocus in two ways: positive and negative defocus defocus. Focal plane is located above the work piece is positive defocus, and vice versa for negative defocus. By geometrical optics theory, when an equal positive and negative from the fuss, the corresponding power density is approximately the same plane, but in fact different shapes of molten pool obtained. Negative defocus, the availability of greater penetration, which is related to the formation of molten pool. Experiments show that the laser heating 50 ~ 200us material begins to melt, the formation of liquid metal and appears asked sub-vaporized to form a city pressure steam, and high speed jet, a dazzling white light. At the same time, high concentrations of vapor to liquid metal movement to the pool edge, the formation of depression in the pool center. When the negative defocus, the material within the power density is higher than it is easy to form more melting, vaporization, so that light passing to the deeper material. So in practice, when asked penetration is high, with negative defocus; Nickel Welding Electrodes thin materials, it is appropriate is out of focus.
Boiler thermal power source. Of mill, Fan (collectively, the fans) is an important component in the boiler equipment. Of mill used to transport coal; induced draft fan is used to pump gas to make it through the chimney smoke. Boiler fan impeller units, in the course of their work, due to high speed (1 480 r / min or more), and withstand a certain wind, leaves and dust particles will be friction and corrosive effect of flue gas, generally run 7 month or so, it will be washed worn out leaves the phenomenon occurs, resulting in decreased life of the impeller, you need downtime. This will cause a corresponding boiler stop running, not only increases the labor intensity of the maintenance workers, increase the loading and unloading costs, spare parts and the corresponding amount of expenses, is more serious is the opportunity of stopping power generation, causing serious economic losses and Welding Electrodes .
Fan impeller structure and technical requirements Boiler fan specification is generally not uniform, the impeller diameter (1 600 ~ 2 000) mm between.
The technical requirements of the impeller: (1) after the disk roughness ≤ 0.5/100; (2) at the end after the jump cylindrical disk error ≤ 4 mm; (3) Disc diameter cylindrical jump at the deviation of ≤ 3 mm; (4) at the end of tapered cylindrical disk before jumping deviation ≤ 6 mm; (5) leaf exports in the face of the back plate is not vertical deviation ≤ 1 / 100; (6) The static and dynamic balance correction.
Generally speaking, on the surface There are several ways to strengthen such as carburizing, plating, and plasma spraying. Conditions for the use of fans and the field conditions, the only feasible way to oxy-acetylene and electric arc spray welding.
Dilution rate of surfacing layer, reflecting the melting of base metal cladding layer into the percentage of the amount. Q235 wheel or base metal is generally 16 Mn. After melting the base metal from the dilution of wear-resistant alloys, alloy weld overlay will reduce the effectiveness, impact wear resistance.
After surfacing the impeller, the acceptance need not be static and dynamic balance test, the surface needs to size, shape and location to meet the bias requirements. Since surfacing uneven heating causes the impeller to produce welding stress, leading to welding deformation, it needs to take appropriate technical measures to control the deformation of the impeller within the tolerance range.
Power plant operation shows that the fan blade life after surfacing increased by 4 times, to avoid the impeller in a boiler overhaul period, due to wear and tear caused by leaf replacement or repair, ensure the normal operation of the unit, and achieved good economic and social benefits.