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Shanghai Precision Quenching Technology Report

On-line Precision Quenching Technology Paper for Extruded Aluminum Profiles

Author: Mai Hongjie (General Manager of Foshan Nanhai Saifu Aluminum Equipment Co., Ltd. ①)

Paper Release Time: 2010-09-10; Location: Shanghai

Key words: extrusion, aluminum profile, precision, on-line quenching

abstract:

In recent years, with the rapid development of the national economy, the application of aluminum profiles in industry has become increasingly widespread. At the same time, the requirements for aluminum profiles are getting higher and higher, mainly in the following aspects: 1. The section requirements of the profiles are getting wider and the shapes are becoming more and more complex; 2. The dimensional accuracy is getting stricter; 3. The mechanical properties are getting higher and higher . In order to meet the market's requirements for aluminum profile products, higher requirements are put forward for the production process and equipment of profiles, especially the online quenching link. Because in order to achieve high mechanical properties of the profile, the cooling rate during quenching of the profile must ensure that the supersaturated solid solution is fixed and does not decompose, preventing the precipitation of the strengthening phase, so as not to reduce the mechanical properties after quenching and aging. Therefore, the cooling rate during quenching should be as fast as possible. However, the faster the cooling rate, the greater the residual stress and residual deformation of the quenched profile, and the dimensional accuracy of the profile cannot be guaranteed. Therefore, in order to meet the above three elements at the same time, higher requirements are put forward for quenching (especially online quenching): 1. It must be able to provide a sufficiently large range of cooling rates to meet the sensitivity of quenching to cooling rates for different alloys. Requirements, and the requirements of different profile wall thicknesses on cooling speed; 2. While ensuring a sufficiently large cooling rate, effectively reduce the deformation of the profile during cooling to ensure the dimensional accuracy of the profile.

Background: Current status of on-line quenching of aluminum extrusions

After nearly ten years of rapid development, the aluminum extrusion equipment has been greatly improved, and the online quenching technology has also been greatly improved, but it still cannot keep up with the needs of the development of aluminum profile products.

1. At present, most of the traditional online quenching in use in China are relatively backward

1) Failure to provide a large enough cooling rate range, and different cooling rates cannot be selected according to different alloys and profile wall thicknesses;

2) Poor regulation. The section of the profile is often asymmetrical, and the wall thickness is not uniform. If the cooling rate cannot be adjusted according to the section of the profile, the thick-walled place will cool slowly, and the thin-walled place will cool quickly. This will cause profile deformation and uneven performance;

3) Poor operability. Some online quenching devices have the functions of the above two points, but the operability is poor, the actual operation is difficult for workers, the accuracy is poor, and it is time-consuming, so it cannot meet the needs of use at all.

Due to the above reasons, the deformation of the profile is large, the performance is unstable, the reject rate is too high, the cost rises, and it is difficult to meet the needs of production. Therefore, it is an important task for the domestic aluminum profile equipment industry to improve the equipment level of domestic online quenching.

2. At present, the online quenching devices in developed countries such as Europe, America and Japan are relatively advanced

1) The combination of air cooling, fog cooling and high-pressure water spray can provide a large cooling speed range, and the appropriate cooling method can be selected according to different alloys and different profile sections. For example, air cooling can be selected for 6063 alloy profiles, high-pressure water spray can be selected for thick-walled 6061 alloy profiles, and fog cooling can be selected for thin-walled 6061 alloy profiles;

2) Good regulation. One is to distribute several air outlets and nozzles in the circumferential direction of the section of the profile, each of which can be adjusted, so that the directional adjustment of the cooling intensity can be performed according to the structure of the section of the profile. For example, the side with thicker wall thickness needs stronger cooling intensity, and the side with thinner wall thickness needs weaker cooling intensity. This is beneficial to the overall cooling of the profile, and reduces the deformation of the profile on the premise of ensuring a sufficient cooling rate; the other is multi-stage cooling, and each stage can choose a different cooling rate. Since the deformation is sensitive at the beginning of quenching, if a faster cooling rate is adopted at the beginning, and the circumferential direction of the section of the profile cannot be adjusted, the deformation of the profile will be large. Therefore, a relatively slow cooling rate can be selected in the front stage of quenching. After the profile is slowly cooled to a certain temperature, a faster cooling rate is used for rapid cooling in the latter stage. This can not only ensure sufficient cooling strength, but also reduce the deformation of the profile.

3) Operability is better. All these adjustments can be controlled through the man-machine interface, the adjustment is more convenient and the operability is strong. The control system has an automatic memory function, which automatically records the process parameters of each production, and can be automatically recalled when it is used next time.

However, because the extrusion of aluminum profiles is intermittent extrusion, the effective cooling time of the profiles that stop in the quenching zone during non-extrusion and the profiles that pass through the quenching zone during extrusion is inconsistent, which will cause the quenching strength of the two sections to be inconsistent. The performance and amount of deformation are also inconsistent. This problem has not been solved well by the more advanced quenching devices in the world.

Paper text: Introduction of new domestic online precision quenching technology and equipment

1. On-line precision quenching considerations

1-1 Sufficient cooling rate range

Only a sufficient cooling rate can ensure that the supersaturated solid solution is fixed and does not decompose, prevent the precipitation of strengthening phases, and ensure that the mechanical properties of the profile after quenching and aging reach the best level. To achieve a sufficient cooling rate, it is necessary to configure a reasonable cooling source, cooling length and cooling density. The cooling source refers to the fan, the water pump and the corresponding cooling medium. The cooling length refers to the length of the tuyere, nozzle or water tank. The cooling density refers to the distribution density of the tuyeres or nozzles. These three aspects should be determined according to the maximum linear density of the profiles produced by the production line, the sensitivity of quenching of different alloys to the cooling rate, and the comprehensive calculation of the extrusion speed. The greater the linear density of the profile produced, the stronger the quenching sensitivity of the alloy to the cooling speed, and the faster the extrusion speed, the larger the fan and water pump to be configured, the longer the length of the quenching zone, and the water temperature of the water used as the medium. to be lower. When the low temperature water cannot meet the cooling speed, different solvents can be added to the water to adjust the cooling capacity of the water. Such as polyethanol, the cooling rate is controlled by adjusting the concentration of polyethanol aqueous solution.

1-2 The cooling rate of the profile section remains basically the same

Only when the cooling rate is basically the same, can the quenching effect of the profile be basically consistent, thereby ensuring the uniformity of the profile performance and effectively reducing the deformation and bending of the profile. To ensure that the cooling rate in the circumferential direction of the section of the profile is consistent, it is necessary to ensure that the cooling intensity in the circumferential direction of the section can be adjusted according to the structure of the profile section and the thickness of the wall thickness. For example, the side with thicker wall thickness needs higher cooling intensity, and the side with thinner wall thickness needs lower cooling intensity, so that the profile section can be cooled to the same temperature at the same time.

In order to ensure that the longitudinal quenching strength of the profile is consistent, it is necessary to ensure that the cooling time received in the longitudinal direction is consistent, that is, the effective cooling time for each part passing through the quenching zone in the longitudinal direction is consistent.

1-3 Adapt to the change of aspect ratio of different profile sections

In particular, the aspect ratio of profiles produced by medium and large extruders varies greatly. When producing plates, the aspect ratio may reach more than 100:1, while when producing pipes or rods, the aspect ratio may be 1:1. In the case of such a large aspect ratio change, how to ensure the appropriate distance between the top, bottom, left, and right surfaces of the profile, the tuyere and the nozzle, so as to ensure effective cooling speed and reduce energy consumption.

1-4 The operability is relatively strong, and it is convenient for the operator to adjust and control.

1-5 On the premise of meeting the above four points, how to effectively reduce the cost of operation.

2. Two new online quenching devices

In order to solve the above problems, we have designed two different forms of online quenching devices. One is for medium and large (above 1650t) extrusion machines, and the other is for medium and small (below 1650t) extrusion machines. Because the profile section produced by the medium and large extruder is relatively large, it is easier to realize the differential cooling control of the profile in the four directions of up, down, left, and right. However, the cross-section of profiles produced by small and medium-sized extruders is relatively small, and it is relatively difficult to realize the differential cooling control of profiles in the four directions of up, down, left, and right, so it is necessary to design different solutions in a targeted manner.

2-1 Functional characteristics of on-line quenching device for medium and large extruders

2-1-1 Four-in-one functions of air cooling, air-mist mixing, mist cooling, and high-pressure water spraying

We adopt the four-in-one functions of air cooling, wind-mist mixing, fog cooling, and high-pressure water spraying. Each function can be adjusted according to the needs, forming a cooling intensity that varies steplessly from weak to strong, and adapts to different alloys and different walls. Thickness has different demands on cooling intensity. For example, air cooling is generally used when producing thin-walled 6063 alloy profiles, air-mist mixing is used when producing thick-walled 6063 alloy profiles or thin-walled 6061 alloy profiles, fog cooling is used when producing medium-thin-walled 6061 alloy profiles, and thick-walled 6061 alloy profiles are produced. Using high pressure water spray.

The configuration of the cooling source should be determined according to the meter weight of the profile produced by the machine, the extrusion speed, the sensitivity of the alloy quenching to the cooling speed and other factors. The greater the profile weight, the higher the extrusion speed, the stronger the sensitivity of alloy quenching to cooling speed, the greater the power of the fan and water pump, and the longer the length of the quenching zone.

Why use wind and fog mixing? The main reason is that the temperature in the extrusion workshop is relatively high. In pure air cooling, even if the wind pressure and air volume are large, the cooling speed is not high and the energy consumption is large. If fog cooling or water cooling is used directly, the cooling rate of some alloy profiles is too high, and the profiles are easy to deform. The use of wind and mist mixing can not only obtain a much stronger cooling effect than air cooling, but also reduce the energy consumption of the fan, so as to obtain a suitable cooling speed.

2-1-2 Circumferential multi-channel cooling arrangement and differential adjustment of cooling intensity

In order to solve the uniformity of cooling in the circumferential direction of the cross-section, several air outlets and nozzles are distributed in parallel around the centerline of the extruder (as shown in Figure 1). Each air outlet and nozzle can individually adjust the air volume or water volume to meet the cooling speed required by different alloys and wall thicknesses, ensuring uniform quenching at all positions on the cross section. This plays a key role in ensuring uniform profile properties and effectively reducing profile deformation.

figure 1

2-1-3 Longitudinal segment adjustment and sequential opening and closing functions

The cooling intensity of each longitudinal section can be adjusted individually. When individual profiles are particularly easy to deform during quenching, and the above two functions alone cannot be satisfied, the cooling intensity of the front section in the longitudinal direction can be reduced, and the cooling intensity of the rear section can be increased. This can not only ensure that the profile is fully cooled, but also reduce the deformation of the profile.

In order to solve the uniformity of longitudinal quenching of profiles, each tuyere and nozzle is divided into several sections in the longitudinal direction (as shown in Figure 2), and the specific number of sections shall be determined according to the needs of the specific production line. Each section has an independent control valve to control. When changing rods and stopping extrusion, it will be closed sequentially from the cooling bed to the extruder; when extruding after rod replacement, it will be opened sequentially from the extruder to the cooling bed. In this way, the cooling time in the longitudinal direction of the profile can be basically consistent, thereby ensuring that the performance of the profile in the longitudinal direction is relatively uniform, and reducing the longitudinal bending and torsion.

figure 2

2-1-4 Up and down displacement adjustment of top air outlet (nozzle) and side air outlet (nozzle)

In order to solve the excessive change of the aspect ratio of the profile, which causes the distance between the upper, lower, left, and right air outlets or the nozzle and the surface of the profile to change too much, we design the upper air outlet and nozzle and the left and right side air outlets and side nozzles to be separated, and they can be separated from each other. Move (as shown in Figure 3). In this way, the distance between the tuyere or nozzle and the surface of the profile can be adjusted according to the aspect ratio of the profile, ensuring that the air outlets, nozzles and nozzles of the upper, lower, left, and right sides maintain an appropriate distance and position from the surface of the profile, improving cooling accuracy and reducing energy consumption Loss.

Figure 3 Up and down misalignment adjustment of the damper and the air outlets on both sides

2-1-5 Auxiliary puller

In quenching operations, tractors are generally not suitable for entering the quenching zone, especially for water cooling operations. If the tractor enters the quenching zone, the quenching device will be difficult to work normally, and the profile passing through the quenching zone cannot be quenched normally, which will cause waste of this section of profile. When the tractor does not enter the quenching zone, but can realize traction and quenching at the same time, the auxiliary traction head is used (as shown in Figure 4). When the first cast rod is produced, the profile is pulled by the auxiliary tractor, the auxiliary tractor is pulled by the tractor, and the quenching device is working normally.

Figure 4 Auxiliary puller

2-1-6 Man-machine interface control and parameter memory function

In order to facilitate the control of the operator, all the actions and process parameters of the online quenching device can be controlled through man-machine dialogue. The friendly operation interface (as shown in Figure 5) is very suitable for domestic workers. In order to improve the efficiency of adjustment and reduce waste products caused by improper adjustment process, the control system is specially designed with automatic memory function. For each profile produced, when the quenching process parameters are considered to be reasonable, the memory function can be used to memorize this group of parameters. When the profile is produced next time, just enter the model code of the profile, and the system will automatically recall the previous memory. parameters for production.

Figure 5 Man-machine interface control and parameter memory function

2-1-7 Remote debugging, monitoring and maintenance

In order to facilitate debugging, monitoring and maintenance, the control system has a remote monitoring interface. When necessary, the system can be remotely debugged, monitored and maintained through the network.

The above scheme has been fully verified on the online quenching device (as shown in Figure 6) equipped with the 2500t and 3600t extrusion machines of Guangdong Haomei Aluminum Co., Ltd., which can fully meet the requirements of the production process. After online quenching and artificial aging, the profiles fully meet the requirements of mechanical properties, and the dimensional accuracy is also fully guaranteed.

Figure 6 Engineering example

2-2 Functional characteristics of online quenching device for small and medium-sized extruders

For the supporting online quenching device for small and medium extruders, in addition to the functional configuration of a, b, c, f, g on the online quenching device for medium and large extruders, the following functions are strengthened (as shown in Figure 7 ):

Figure 7 Rotation and swing control of the nozzle

2-2-1 spray head is designed to swing and rotate

In order to solve the accurate positioning of the water spray on the section of the small profile, the water spray and spray nozzles are designed to be able to swing and rotate, such as α and β in the illustration. Rotating the nozzle at a certain angle can adjust the width of the sprayed water and mist to a certain range, and even adjust it to a line parallel to the extrusion center line, so that the water can be concentrated on a certain part of the profile. The nozzle swings at a certain angle, which is also beneficial to aim the water and mist at a certain position of the profile.

2-2-2 nozzle can also move radially

The nozzle can also move a certain distance in the radial direction, which is also for better cooling positioning and reducing water pressure loss. This scheme has been fully verified on the online quenching device equipped with the 1450t and 1800t extruders of Shenzhen Fusheng Hardware Products Co., Ltd. After online quenching and artificial aging, the profiles fully meet the requirements of mechanical properties, and the dimensional accuracy is also fully guaranteed.

Summary: Research and Development Direction of Online Quenching

1. Develop in the direction of intelligent control

At present, the on-line quenching device is mainly controlled by people, and operators can choose different cooling methods and cooling speeds according to different alloy compositions, different profile sections and wall thicknesses. This will not only be highly dependent on people, but also affect efficiency and accuracy. intelligent