Method for inhibiting double-zero foil annealing hot bulging
Technical Field
The invention relates to the technical field of double-zero aluminum foil production, in particular to a method for inhibiting double-zero foil annealing hot bulging.
Background
The aluminum foil, particularly the double-zero aluminum foil, is easy to generate annealing bulge phenomenon in the processing flow, namely, one or more raised lever marks are generated on the foil surface of the aluminum foil in the annealing process, which is called annealing bulge. Once the aluminum foil is annealed, the aluminum foil cannot be used for downstream, and needs to be removed, so that the production efficiency and the yield of the aluminum foil are affected, and the delivery is affected due to the fact that the length of a fixed-size product is insufficient after the annealing drum is removed.
The problem of annealing hot drums in the aluminum foil processing process affects the average yield of all aluminum foil manufacturers to be about 1%, and the influence of the hot drums on the yield of products with the thickness of less than 0.006mm, the length of more than 30000m and the width of more than 1200mm is even more than 5%. The problem of annealing the hot drums is exacerbated when the thickness of the aluminum foil rolls is thinner, the meters are longer, and the widths are wider.
The production process of the aluminum foil comprises the following steps: rolling, slitting, standing, annealing and cooling. The reason for the hot drum is that the influence factors include plate shape, oil carrying, coil density, thickness, width, coil diameter, annealing process and the like, but the reason for the root is that the stress change causes the plastic deformation of the aluminum foil. There are various reasons for the generation of stress, such as residual stress after rolling, internal stress of recrystallization change, thermal deformation stress of thermal expansion and contraction, deformation stress caused by oil gas pressure, etc., and the influence of the final change result is also reflected in the final state after annealing.
The reason for the thermal bulging is described by the stress variation: the ideal situation of the aluminum foil coil heat transfer is shown in fig. 1, the heat transfer is divided into an axial form and a radial form, in fig. 1, the single diagonal filling area is mainly axial heat transfer, the double diagonal filling area is mainly radial heat transfer, the dash-dot line is a track where the radial target temperature and the axial target temperature reach simultaneously, the dash-dot line is a track where the axial heat transfer at two ends reaches the target temperature, and half of the length of the single diagonal filling area (the axial heat transfer speed) is about 20-50 times of the radial highest position (the radial heat transfer speed) of the double diagonal filling area.
The axial heat transfer of the aluminum foil is realized by the same material of the aluminum foil, the heat transfer speed is very high, the heat transfer and stress are relatively uniform, and the heat transfer direction is along the axial direction of the aluminum foil coil, so that the heat rising is not influenced.
The radial heat transfer is between different materials of aluminum foils, besides the air between each layer affects the heat transfer, the oil carried by the aluminum foils between the layers also affects the heat transfer seriously, so the radial heat transfer speed is very slow, the heat transfer and the stress are not uniform, the stress is not easy to release along the axial direction, the stress is mainly released along the radial direction, meanwhile, the oil gas can be evaporated after the oil carried on the surface of the aluminum foils reaches a certain temperature, the middle oil vapor is difficult to discharge along the axial direction, the radial pressure can be generated to act on the aluminum foils, and when various resultant forces exceed the strength of the aluminum foils or the aluminum foil plate type is not good and is partially defective, the plastic deformation is caused to finally form the bulge.
Because the axial and radial heat transfer speeds of the aluminum foil are greatly different, the axial heat transfer speed is 20-50 times of the radial heat transfer speed according to the actual test, the thickness of the aluminum foil is also changed differently, the influence speed of the thick foil is reduced, and the influence speed of the thin direction is increased. Therefore, the established process time is basically not considered to be influenced by radial heat transfer during daily double zero foil annealing, but the phenomenon of hot bulging is quite related to the ignored radial heat transfer.
The heat transfer during cooling of the aluminum foil coil is the same as that shown in fig. 1, except that the heat transfer is reversed, and the heat transfer is from the inside to the outside of the aluminum foil coil. Axial heat transfer is from the middle to the two ends in the axial direction, and the same reason ensures that the heat transfer and deformation are uniform. The radial heat transfer is affected by interlayer air, the heat transfer speed is low, the cooling is also uneven, and the middle part of the aluminum foil coil is still at high temperature during external cooling, so that the middle part can not be contracted to deform due to the fact that the middle part is still in a thermal expansion state during external cooling shrinkage, the internal stress of the aluminum foil coil is increased, and when the deformation amount exceeds the thermal elastic deformation at the corresponding temperature, the part is converted into plastic deformation from the elastic deformation during original temperature rise, and finally the bulge is formed.
Therefore, the reason for the annealing heat bulging is that plastic deformation at the time of temperature rise and deformation transformation at the time of temperature reduction are finally formed. In summary, the thermal bulging area can only be the area where the radial heat transfer is dominant, namely the range of the double-diagonal filling area in fig. 1, and the deepest bulging area does not exceed the radial highest position of the area. Corresponding to the shape of the region is the rule of bulging, i.e. the depth of the bulging increases from the two ends to the middle in the axial direction, and the number of bulging decreases from the outer layer inwards for depth reasons.
The effect of the width and the roll diameter of the aluminum foil roll on the hot bulging is also evident from fig. 1. According to the difference of 20-50 times of the tested heat transfer speed, a material roll with the width of 1600mm can be roughly calculated, the deepest part of the hot drum can not exceed 40mm, and the region beyond the 200-300mm at the two ends is basically free of the drum with the depth exceeding 10 mm. This corresponds to empirical data in daily production, i.e. the quality-influencing hot drum is essentially only in aluminium foil rolls having a width exceeding 600mm, with a drum depth of 10-30mm.
In the industry, various manufacturers increase investment for improving the problem of the aluminum foil heat drum, and various measures such as radial heat transfer inhibition, temperature rise and cooling speed reduction or oil carrying and oil removal control are adopted, so that good effects are achieved, but the problems are not thoroughly solved all the time, and the problems are the quality problems to be solved in the current industry.
Disclosure of Invention
The invention provides a method for inhibiting double-zero foil annealing hot bulging, which aims to solve the problem that the existing measures are poor in aluminum foil hot bulging effect, and residual stress in aluminum foil processing is eliminated by adjusting the production flow and optimizing the production process, so that the problem of aluminum foil bulging is solved.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a method of inhibiting double zero foil annealing thermal bulging comprising the steps of:
step 1, adding a low-temperature high-vacuum oil removal process after rolling: directly pushing the coil into a vacuum furnace after rolling, controlling the temperature of furnace gas to be 120 ℃ and preserving heat for 5-15 hours, vacuumizing to be less than 100Pa, preserving heat for 5-10 hours, and finally directly discharging from the furnace and standing;
step 2, standing the coil after rolling and before slitting;
and step 3, adding a recovery section in the annealing process: and in the heating and heat preserving stage, heat preserving is carried out for 5-15 hours at 100-150 ℃, and then the subsequent normal annealing is carried out.
In step 1, the coil is directly deoiled at low temperature and high vacuum by using the coil temperature after rolling is finished, so that the heating time can be shortened, and the annealing time is shortened by taking the performance as a main part and deoiling as an auxiliary part in the subsequent annealing process.
In the step 2, after rolling, the coil is kept stand in the first stage until the coil is cut into the first stage of natural aging stress relief, and after cutting, the coil is put into an annealing furnace to be the second stage of natural aging stress relief.
Further, in the step 2, a material roll heat preservation device is added, and the material roll is kept stand in the heat preservation device, and meanwhile, the standing time is prolonged.
Further, in step 3, in the final product annealing process, a recovery annealing section is added to reduce stress, and the coil is kept for a period of time in a temperature range lower than the recrystallization temperature.
Through the technical scheme, the invention has the beneficial effects that:
according to the invention, aiming at the reason of influencing the thermal bulging, the adjustment is respectively carried out on the prior art, and meanwhile, the working procedures are added, so that the stress influence can be effectively removed. Wherein, the rolling is followed by standing, so that a better stress relieving effect can be achieved to relieve residual stress; the added low-temperature high-vacuum oil removal and stress removal process can remove the influence of stress and surface oil at the same time, thereby achieving the purpose of inhibiting the double-zero foil annealing hot bulging. The recovery stage is added in the annealing process, so that the aluminum foil has enough time to recover, and the stress influence can be well removed, thereby achieving the purpose of inhibiting the hot bulge.
Drawings
Fig. 1 is a schematic diagram of an ideal case of heat transfer by heating an aluminum foil roll.
Detailed Description
The following detailed description of specific embodiments of the invention refers to the accompanying drawings:
a method of inhibiting double zero foil annealing thermal bulging comprising the steps of:
and step 1, adding a low-temperature high-vacuum oil removal process after rolling, namely carrying out low-temperature high-vacuum oil removal and stress removal on the coil after rolling, wherein the process is an improved oil removal and stress removal comprehensive measure. Specifically, after rolling, the coil is directly pushed into a vacuum furnace, directly heated to the temperature of 120 ℃ of furnace gas and kept for 5-15 hours, then vacuumized to be below 100Pa and kept for 5-10 hours, and finally directly discharged from the furnace and kept stand. After the material is rolled into the furnace, the temperature of the rolled material is fully utilized to about 80 degrees, and the heating and heat preservation electricity consumption can be greatly reduced, so that the effects of saving energy and reducing cost can be achieved.
The oil on the surface of the aluminum foil can influence the friction force between layers on one hand, so as to influence the drum; on the other hand, the oil gas pressure of high-temperature evaporation of the aluminum foil in the annealing process acts on the surface of the aluminum foil to interact with the stress of the aluminum foil, so that the drum is influenced. Therefore, reducing the oil in the aluminum foil tape prior to annealing is also a means of reducing the lifting.
According to the principle of petroleum reduced pressure distillation, the recovery temperature of the aluminum foil is combined, and low-temperature high-vacuum oil removal annealing is performed after rolling is finished, so that oil on the surface of the aluminum foil can be effectively removed, and the processing residual stress can be better removed, thereby achieving the purpose of preventing bulging after annealing of a final finished product.
Meanwhile, as low-temperature high-vacuum oil removal is performed in advance, the process control is adjusted to be mainly based on performance and secondarily based on oil removal during final annealing of finished products. And because most of the time is used for degreasing in the annealing at present, the annealing time of the finished product can be greatly shortened after the measures are adopted, thereby improving the production efficiency.
And 2, standing the coil after low-temperature high-vacuum annealing, namely canceling the existing standing after slitting, adjusting the standing after rolling and degreasing, wherein the standing is the measure for eliminating the residual stress in the processing process. Meanwhile, a conventional material roll heat preservation device is added to preserve heat and stand the material roll, and meanwhile, the standing time is prolonged, so that a good stress relieving effect is achieved.
The natural aging destressing after rolling is finished comprises two stages, wherein the first stage of natural aging destressing is from rolling to slitting, and the second stage of natural aging destressing is from slitting to annealing furnace.
The purpose of standing at normal temperature and normal pressure is to eliminate the processing residual stress. The existing production flow is mainly to carry out standing after slitting, namely, the material roll is naturally kept standing for a certain time in the second stage: the temperature is lower in winter, the standing time is longer, and the standing time is shorter or even no standing is performed when the temperature is higher in summer.
The optimized production flow is adjusted to be developed in the first stage. The first stage is that the temperature of the coil is higher at the end of rolling, the temperature of the coil can reach 80 DEG or higher after the end of rolling in summer, the temperature of the coil is basically higher than the ambient temperature when slitting after standing for one day, the temperature reaches more than 30 DEG, and the temperature is basically maintained after slitting. After the rolling in winter is finished, the temperature of the coil can be slightly lower to about 60 degrees, the temperature during slitting is basically equal to the indoor environment temperature by 10 degrees after standing for one day, and the temperature is basically maintained after slitting.
The effect that the material roll does not stand in summer is better than that of standing for a long time after slitting in winter, so that the natural aging effect in the first stage in summer is fully demonstrated to be better than the total effect of the two stages in winter, and the reason is mainly that the average temperature in the first stage in summer is higher. Therefore, the best stage for eliminating the processing residual stress is to fully utilize the temperature of the coil to achieve better stress eliminating effect after the rolling is finished.
And 3, adding a recovery section in the annealing process to optimize the annealing process, namely carrying out recovery annealing, wherein the recovery annealing is annealing below the recrystallization temperature, namely preserving heat for a period of time at a temperature lower than the recrystallization temperature, specifically preserving heat for 5-15 hours at 100-150 ℃ in the temperature-raising and heat-preserving stage, and then carrying out subsequent normal annealing. The aim of eliminating and controlling the concentrated release of stress can be achieved through the optimization of the annealing process, and the rising of the drum is further controlled.
For residual stress during processing, three main types are: macroscopic stress, microscopic stress, and lattice distortion stress. The first kind of macroscopic stress is caused by uneven integral deformation of the aluminum foil, and the quality of plate type control is the most direct embodiment. Although macroscopic stresses account for a small proportion of the total residual stress, they still have an impact on the lifting. The standing measure is the most basic measure for removing macroscopic stress, but is only partially removed under the influence of temperature and time, and the macroscopic stress can be well removed by adopting the high-vacuum oil removal and stress removal process for assistance.
The effect of the aluminum foil annealing process on performance is mainly in two stages, recovery and recrystallization. The recovery stage can remove all macroscopic stresses of the first type and part of the second and third types of stresses, and the recrystallization stage can remove all processing residual stresses. Although the recovery and the recrystallization are different stages, competition exists between the recovery and the recrystallization, the driving force of the recovery and the recrystallization is deformation energy storage in the processing process, and the energy requirements of the recovery and the recrystallization are different. The recovery stage has a great influence on the recrystallization, and the recrystallization temperature also has a certain influence on the recovery stage. In the process of continuously heating and absorbing heat energy, once recrystallization starts, recovery is not carried out, so the rest three stresses are released and eliminated in the recrystallization process, and the stress is released intensively, thereby generating corresponding influence.
Therefore, in the final product annealing process, the stress influence can be well removed by adding a recovery stage in the optimization process, so that the aim of inhibiting hot bulging is fulfilled.
The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention, so that all equivalent changes or modifications of the structure, characteristics and principles described in the claims should be included in the scope of the present invention.