Reasons and prevention of the deformation of industrial large ceiling fan blades, do not regret it!

Industrial ceiling fans are widely used in shopping malls, supermarkets, gymnasiums, factory workshops and other places, but partners who have personally purchased industrial ceiling fans may find that there are still some differences in industrial ceiling fans. For example, some industrial ceiling fans have to bend and so on. Deformation problems, some do not, so why do industrial ceiling fan blades have deformation problems? How do avoid and prevent the occurrence of fan blade deformation during production or welding? Next, the editor will introduce to you the reasons for the deformation of the large industrial ceiling fan blades and preventive measures, hoping to help you.

1. Reasons for deformation of large industrial ceiling fan blades At present, the industrial large ceiling fan blades on the market are mainly made of aluminum alloy. This is because aluminum alloy materials have low density, high strength, high thermal conductivity, and strong corrosion resistance. Good physical properties and mechanical properties, but due to improper selection of welding methods and welding process parameters, it will lead to serious mechanical deformation after blade welding due to excessive force concentration, or due to weld pores, slag inclusion, and incomplete penetration. And so on, resulting in weld metal cracks or loose material, thus seriously affecting product quality and performance. Next, we will analyze several reasons for the deformation of the fan blades:

1. It is easy to be oxidized. In the air, aluminum is easy to combine with oxygen, resulting in a dense aluminum oxide film (thickness about 0.1-0.2mm) with a high melting point (about 2050°C), which greatly exceeds the melting point of aluminum and aluminum alloys. (around 600°C). The density of alumina is 3.95-4.10g/cm, which is about 1.4 times that of aluminum. The surface layer of alumina film is easy to absorb water. When welding, it will hinder the fusion of basic metals, and it is easy to form pores, slag inclusions, and lack of fusion. , resulting in reduced performance.

2. It is easy to generate pores. The main factor for the generation of pores during the welding of aluminum and aluminum alloys is hydrogen. Since liquid aluminum can dissolve a large amount of hydrogen, solid aluminum basically does not dissolve hydrogen, so when the temperature of the molten pool rapidly cools and solidifies, Hydrogen does not have time to escape, and it is easy to form pores in the weld. At present, it is difficult to completely eliminate the hydrogen hole. There are many sources of hydrogen, such as hydrogen in the arc welding atmosphere, and the surface of aluminum plates and welding wire adsorbs moisture in the air.

3. The tendency of deformation during welding is large. The linear expansion coefficient and crystallization shrinkage rate of aluminum are about twice larger than those of steel, which is easy to generate relatively large internal stress of welding deformation, and the structure with high rigidity will accelerate the formation of thermal cracks.

4. Evaporation and burning of alloying elements Aluminum alloys contain elements with low boiling points (such as magnesium, zinc, manganese, etc.), which are easily evaporated and burned under the action of high-temperature arcs, thereby changing the chemical composition of the weld metal and making the welding Seam performance decreases.

5. Temperature strength and plasticity The strength and plasticity of aluminum at low and high temperature are very low, which destroys the formation of the weld metal, and sometimes easily causes the weld metal to collapse and weld through. These are all caused by the soft texture of aluminum. To avoid these situations, it is necessary to control the temperature during the welding process to avoid deformation or welding penetration caused by excessive temperature.

2. Preventive measures for fan blade deformation

1. Make preparations before welding Use chemical and mechanical methods to strictly clean the surface oxide film on both sides of the weld groove. Chemical cleaning is cleaning the surface of the workpiece with edible alkali or acid. This method can not only remove the oxide film but also remove the oil. Mechanical cleaning can use pneumatic and electric milling cutters, scrapers, files and other tools. For thinner oxide films, 0.25mm copper wire brushes can be used to polish and remove the oxide film. Welding should be performed immediately after cleaning. If it is placed for more than 4 hours, it must be cleaned again.

2. During the welding process of determining the assembly gap and tack welding distance, the aluminum plate is heated and expanded, so that the gap of the weld groove is reduced. If the assembly gap before welding is too small, the overlapping of the grooves of the two plates will be caused during the welding process. , Increase the unevenness and deformation of the board surface after welding. If the matching gap is too large, welding is difficult and there is a possibility of burn-through. A certain tack welding spacing can ensure the required tack welding gap, and selecting the appropriate assembly gap and tack welding spacing is an effective measure to reduce deformation.

3. Choose the right welding equipment There are many types of welding products on the market. It is usually recommended to use AC tungsten argon arc welding (ie TIG welding). It is a welding method that uses the arc generated between the tungsten electrode and the workpiece to melt the base metal and fill the welding wire under the protection of argon gas. When this welding machine is working, because the polarity of the alternating current changes periodically, in each cycle, the half-wave is DC positive connection, and the half-wave is DC reverse connection.

4. Select the appropriate welding method. The welding method parameters are usually carried out by the left welding method, and the welding torch and the workpiece will form an angle of 60°. When the welding thickness is 15mm, the right welding method is used, and the welding torch and the workpiece will form a 90° angle. When the thickness of the welded wall is more than 3mm, open the V-shaped groove, the angle is 60°~70°, the gap should not be greater than 1mm, and the multi-layer welding method is used to complete. When the wall thickness is less than 1.5mm, no groove, no gap, and no filler wire. When welding the fixed pipe butt joint, if the pipe diameter is 200mm and the wall thickness is 6mm, it is advisable to use a tungsten electrode with a diameter of 3-4mm, a welding current of 220-240A, a filler wire with a diameter of 4mm, and a filler wire with a diameter of 1-4mm. 2 layers are welded.