Because of its advantages of corrosion resistance, high specific strength and specific rigidity, low density, easy forming, and energy-saving regeneration, aluminum has been widely used in both production and life, and is an important basic material for the development and progress of the national economy. In particular, there is almost no substitute for structural and decorative applications, while flat aluminum extrusions also play an important role in promoting social and economic development.
Spray cooling is an important process for producing aluminum extrusions. The spray cooling process of aluminum extrusions directly determines the mechanical strength of the profiles. In order to improve the mechanical strength of the profiles, after many profiles are rapidly cooled, the cooling equipment is required to ensure even distribution of the aluminum strip extrusion profiles in the length, width and wall thickness directions.
This article explores the on-line water cooling factors that affect the 6061 aluminum alloy product width, width, width, and length of 650mm.
There are many factors affecting on-line water cooling of flat aluminum extrusions. This article only analyzes and summarizes the following important factors:
First, the impact of extrusion speed
The extrusion speed of aluminum extrusions is usually expressed as the velocity of the metal flowing out of the die hole. The major influence of the extrusion speed is the temperature distribution in the length direction, while the temperature distribution in the width direction is less affected. Therefore, this paper only The temperature distribution law in the length direction is discussed in the case of different extrusion speeds. That is to say, only the upper surface of the flat aluminum extrusion is taken as the study surface. If other parameters are not changed, the aluminum extrusion is flat. Pressure profile water spray cooling temperature field Temperature distribution on the centerline of the upper surface when the extrusion speeds are 10, 20, 30, 40, 50, and 60 (in mm/s).
Through the analysis, it is found that the temperature difference between the two ends of the flat aluminum extrusion will become smaller and smaller as the extrusion speed becomes larger, and the temperature change is smaller after the extrusion speed of 10 mm/s is increased to 40 mm/s. In other words, the temperature distribution in the longitudinal direction of the flat aluminum extruded section becomes more and more uniform as the extrusion speed increases, but when it is increased to 40 mm/s, the influence on the temperature field in the longitudinal direction becomes greater. The smaller, the smaller the impact, the extrusion speed has a critical value on the impact of the spray cooling temperature field of flat aluminum extrusions, the critical value is 40mm/s, if the extrusion speed is less than the critical value, then the temperature The influence of the field is larger, but if the extrusion speed is greater than the critical value, its influence on the temperature field is getting smaller and smaller.
The cooling rate for the critical cooling temperature range of the 6061 alloy should be not less than 650Â°C/min (923.15K/min), ie, the extrusion speed should be greater than 46mm/s, so that the material basically presents a large amount of substructure and part of the refinish product structure. Mechanical properties near 6A02 alloy.
Second, the impact of the nozzle lateral spacing
The upper and lower rows of nozzles are easy to make uneven temperature distribution of flat aluminum profiles, and the phenomenon occurs that the temperature on both sides is high and the center temperature of the upper and lower surfaces is low. In this regard, the nozzle arrangement structure can be optimized, and two rows of nozzle arrangements can be implemented. Two rows of nozzles are arranged above and below the extruded profile.
The nozzle diameter is 10mm, the vertical distance between the nozzles is 50mm, the number of upper and lower four rows of nozzles should be the same, all 13, the upper nozzle and the upper surface to maintain a distance of 120mm and the lower nozzle and the lower surface to maintain a distance of 10mm, cooling area The length is 650 mm, the inlet water flow rate of the nozzle is 56.52 kg/h, the lower nozzle is 141.3 kg/h, the extrusion speed is 60 mm/s, and the gravitational acceleration is 9.8 m/s2.
The influence of the lateral spacing of nozzles on the temperature field in the longitudinal direction is small and negligible. Therefore, only the variation of the temperature field in the width direction is discussed. If the above surface is the study surface and the center line of the upper surface is taken at a distance of 5mm to take the study point, then when the lateral distance L is 50, 60, 70 and 80 (in mm), the flat aluminum extrusion is The temperature field distribution of water spray cooling on the centerline of the surface has found that the temperature distribution on the centerline of the upper surface of the flat aluminum extrusion profile is â€œWâ€ with the spacing of the nozzle horizontal line increasing, and the temperature field distribution is taken at the lateral spacing. When the value is 60mm, both sides of the plate are even and the center line of the plate still has a temperature difference of 40K.
Therefore, it is more reasonable to set three rows of nozzles vertically and horizontally, that is, to add a row of nozzles along the centerline of the board width.
Third, the influence of the vertical spacing of the nozzle
The vertical spacing of the nozzles mainly affects the temperature distribution in the longitudinal direction, while the temperature distribution influencing the width direction is negligible, as long as the influence of the temperature variation law in the length direction on the vertical spacing of different nozzles is discussed. If the study surface is the upper surface and the center line of the upper surface is taken at a distance of 5mm to take the study point, other parameters remain unchanged. The inlet water flow rate for the upper row of nozzles is 734.76, and the value for the lower row of nozzles is 1836.9 (units). For kg/h), the extrusion speed is 60mm/s.
The temperature difference between the two ends of the flat aluminum extrusion will increase with the longitudinal distance between the nozzles. That is to say, the fluctuation of the longitudinal temperature distribution of the flat aluminum extrusion will increase with the increase of the longitudinal distance of the nozzle. The distribution will become more and more inhomogeneous and the vertical spacing of the nozzles should be less than 50mm.
Fourth, the impact of water temperature
Two rows of nozzles are arranged, that is, two rows of nozzles are arranged above and below the flat aluminum extrusion, and the lateral distance between the nozzles is 60 mm.
If the research surface is the upper surface, and the water temperature values â€‹â€‹are 20, 25, 30, 35, and 40 (in Â°C), the spray cooling temperature on the centerline of the upper surface length and width direction of the flat aluminum extrusion profile. Curve studies have found that the temperature of flat aluminum extrusions increases with cooling water temperature, but does not affect the uniformity of the temperature distribution.
In summary, the temperature field in the width direction is less affected by the extrusion speed and the temperature field in the length direction has greater influence, and there is a critical value in the temperature field affected by the extrusion speed. The extrusion speed for the 6061 alloy should be greater than 46 mm. /s.
In the case of two-row nozzle arrangement, the temperature field distribution in the width direction is greatly affected by the lateral spacing between the nozzles, and the temperature field distribution is even when the lateral distance of the nozzle is 60 mm. The plate center line is still 40K. Temperature difference. Therefore, it is more reasonable to set three rows of nozzles vertically and horizontally, that is, to add a row of nozzles along the centerline of the board width. With the increase of the vertical spacing of the nozzles, the longitudinal temperature distribution will be more and more uneven, and the longitudinal spacing of the nozzles should be less than 50mm.
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