3.2 Feasibility analysis of welding stator of DYH-200 welding unit
In the DYH-200 welding unit, the trigger circuit of the argon arc welding machine is designed with a negative feedback circuit to ensure stable combustion of the welding arc. The high-frequency oscillator has a good anti-jamming device. Under the control of the programmable controller, multiple torches can synchronously trigger the arc. Moreover, the welding fixture is provided with an arc ring, an arc ring and an arc ring to ensure uniformity of arc ignition, arcing and arc extinction, and uniformity and symmetry of weld distribution. The expansion mandrel device clamps and presses the stator core. When welding, heating and cooling are carried out at the same time, so the deformation after welding is minimal or non-deformed, which ensures the flatness, verticality, size and precision of the inner hole of the stator, so that it has good intrinsic quality and appearance quality.
3.3 Process design of multiple welding torches at the same time
The process design should first select the welding equipment that can complete multiple welds at a time, and then design the specific process under the premise of meeting the design requirements.
3.3.1 Electrode design
1 electrode material
When the stator core is argon-arc welded, the workpiece is connected to the positive electrode, and the effective heat of welding is large. The cathode adopts an electrode that is not melted, and requires a high melting point of the material, low evaporation and strong electron-emitting ability, and generally uses a tungsten-based material as the electric pole.
2 electrode diameter and taper
Generally, a bar of Φ 2 to 5 mm is used; the taper is 15° to 30°.
3.3.2 Argon
Argon is not only easy to ionize, but also easy to arc. At a given current, the operating voltage of the argon arc is low, and the change in arc length causes a small change in arc voltage. Therefore, argon gas is selected as the shielding gas.
1 argon purity
Very little water and hydrogen are required. Generally, 99.99% of refined argon is used.
2 argon flow
When the flow rate of argon gas is too large, it is easy to wind the air into the protection zone to form a turbulent flow, which affects the protection effect of argon gas. At the same time, because of the high cost of argon, the production cost is increased. When the flow rate of argon gas is too small, its flow rate is smaller than the convection speed of the air in the weld zone, and a laminar flow shield cannot be formed in the weld zone, and the protection effect will also be lost. This problem must be avoided when designing this parameter. Considering various factors, the argon flow rate can be selected within 3 to 10 L/min.
3.3.3 Nozzle
A circular tube-shaped outlet tube nozzle with a smooth and wide flow protection range is selected.
3.3.4 Extension length of the electrode and arcing gap
The extension length of the electrode and the arcing gap determine the length of the argon hood, the stiffness of the gas flow and the dispersion of the gas, which affect the protection effect of the weld zone.
1 electrode extension length
The distance from the small end face of the nozzle to the working end face of the electrode is the extension length of the electrode. It directly affects the flow of the welding current. The longer the extension length of the electrode, the larger the resistance. When a large current passes, the degree of redness is more obvious, and the more easily burned, the evaporation of helium is also intensified. Moreover, the distance from the nozzle to the weld is increased, and the protective effect of argon is lowered.
The length of the electrode extension is too short, and the closer the arc is to the porcelain mouth, the more easily the porcelain mouth is burned, and the inner roundness (or inner cone surface) of the porcelain mouth is destroyed, which affects the normal formation and protection effect of the gas mask. Therefore, the extension length of the electrode is generally controlled to be 3 to 7 mm.
2 arcing gap
The arcing gap is the distance from the working face of the electrode to the welding face. It determines the arc length of the weld. The longer the gap, the longer the arc length, the higher the energy required for high-frequency arc striking, and the greater the effective value of the high-frequency voltage, so that the argon gas can be ionized. In this case, the high-frequency transformer is easily broken down, which increases the difficulty in manufacturing the high-frequency transformer.
Since the effective path of the argon gas flow (the length of the hood) is determined by the extension length of the electrode and the arcing air gap, the larger the gap, the longer the hood length, the larger the argon diffusion surface, and the lower the argon density. The degree of arc reduction is easy to cause drift, which reduces the protection effect of argon gas.
When designing multiple arc gaps of the welding torch, it should be selected between 1.5 and 2.5 mm. Therefore, the design of the process should require clearance adjustment using a feeler gauge to adjust the uniformity of multiple torches.
3.3.5 Welding speed
The design of the welding speed should be determined according to the strength requirements of the weldment, the deformation requirements, the protection effect of the argon hood, and the production efficiency. Generally, it can be selected within the range of 3.5 to 5 mm/s.
3.3.6 Welding current
Under the premise of meeting the requirements of weld penetration and welding speed, it can be selected in the range of 80 to 120A.
3.3.7 Pressure of hydraulic press
When designing the pressure of the hydraulic press, the pressure should be selected according to the dimensional accuracy requirements of different stators, which can be selected within 6-10 MPa.
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