CN112048685A - Post-treatment method capable of improving fatigue resistance of aluminum alloy - Google Patents

Abstract

The invention discloses a post-treatment method capable of improving fatigue resistance of an aluminum alloy, which comprises the steps of treating the aluminum alloy at-30 to-25 ℃, 50 to-45 ℃ and-65 to-60 ℃ respectively by adopting a step-by-step cooling and step-by-step rolling method, then rapidly heating to 150 to 180 ℃ within 20 to 30min for rapid heating treatment, and finally carrying out cooling and aging treatment. The mode of gradual cooling, gradual low-temperature rolling, rapid heat treatment and cooling aging treatment can effectively improve the fatigue resistance of the Al-Zn-Mg-Cu (7000) alloy.

Description

A post-processing method that can improve the fatigue resistance of aluminum alloys

technical field

The invention relates to the technical field of aluminum alloys, in particular to a post-processing method that can improve the fatigue resistance of aluminum alloys.

Background technique

7 series aluminum alloy is a very important series of aluminum alloys. It belongs to aluminum-magnesium-zinc-copper alloy. It is a heat-treatable super-hard aluminum alloy with good wear resistance and corrosion resistance. Aluminum alloys are widely used in the aerospace industry. With the advancement of science and technology, the hardness requirements of this series of alloys are getting higher and higher, and conventional high-strength and high-hardness aluminum alloys can no longer meet the needs of the industry. On the other hand, in the existing conventional aluminum alloy manufacturing process, the strength of the 7-series aluminum alloy and the quenching residual stress are a pair of contradictory performance indicators. In order to obtain high strength, high cooling strength must be used for quenching. However, cooling The large strength leads to uneven distribution of quenching residual stress. With the further increase of cooling strength, the strength of the alloy increases, but the quenching residual stress also increases significantly. However, the existence of quenching residual stress will lead to subsequent machining deformation of the extruded sheet. , the machining accuracy is poor, and it will also affect its stress corrosion resistance and fatigue performance.

Chinese invention patent CN110029297A discloses an aluminum alloy and its quenching post-treatment method. The method can effectively improve the strength properties of the plate while eliminating the quenching residual stress by repeatedly rolling in the cryogenic/quick heating state, while rolling After the production, with the subsequent deep cooling, rapid heating and cooling and aging treatment, the quenching residual stress can be effectively stabilized, and the strength properties of the plate can be further improved. Compared with the existing aluminum alloy materials, the quenching residual stress can be significantly reduced. At the same time, the strength of the aluminum alloy is also significantly improved. However, this method requires the aluminum alloy to be immersed in low-temperature liquid nitrogen for cooling, as well as multiple cold and heat exchanges. The energy consumption in the whole process is very large. Therefore, in order to reduce the cost, it is necessary to develop a method that can improve the fatigue resistance of the aluminum alloy. post-processing method.

SUMMARY OF THE INVENTION

Based on the technical problems existing in the background art, the present invention proposes a post-processing method that can improve the fatigue resistance of aluminum alloys.

The technical scheme of the present invention is as follows:

A post-processing method capable of improving the fatigue resistance of an aluminum alloy, comprising the following steps:

A. Put the quenched aluminum alloy sheet into the cold storage, and within 2~3h, slowly cool down the center temperature of the sheet from room temperature to -30~-25℃; keep the temperature at -30~-25℃, The holding time is 3~5h, and the rolling is carried out at this temperature;

B. Within 3~5h, slowly reduce the central temperature of the plate to -50~-45℃; keep the temperature at -50~-45℃, hold the temperature for 2~3h, and carry out rolling at this temperature;

C. Within 5~8h, slowly reduce the center temperature of the plate to -65~-60℃; keep the temperature at -65~-60℃, hold the temperature for 18~24h, and carry out rolling at this temperature;

D. Rapidly raise the core temperature of the plate to 150-180°C within 20-30min, and keep it for 3-5h;

E. The above plate is subjected to cooling and aging treatment, and it can be stored for 3 to 5 days.

Preferably, in the step A, rolling is performed at a rolling rate of 8 mm/s, and the rolling reduction ratio is controlled to be 8-10%.

Preferably, in the step B, the rolling is performed at a rolling rate of 5 mm/s, and the rolling reduction ratio is controlled to be 5-6%.

Preferably, in the step C, the rolling is performed at a rolling rate of 3 mm/s, and the rolling reduction ratio is controlled to be 2-3%.

Preferably, in the step E, the plate is subjected to cooling and aging treatment at a cooling rate of 5-8°C/h.

The advantages of the present invention are: the post-processing method for improving the fatigue resistance of aluminum alloys of the present invention adopts the method of stepwise cooling and graded rolling, and the aluminum alloys are cooled at -30~-25°C, -50~ -45°C and -65~-60°C treatment, then rapidly heat up to 150~180°C within 20~30min for rapid heat treatment, and finally perform cooling and aging treatment. The method of stepwise cooling + graded low-temperature rolling + rapid heat treatment + cooling and aging treatment of the present invention can effectively improve the fatigue resistance of Al-Zn-Mg-Cu (7000) series alloys.

Detailed ways

Example 1

A post-processing method capable of improving the fatigue resistance of an aluminum alloy, comprising the following steps:

A. Put the quenched aluminum alloy sheet into the cold storage, and within 2.5h, slowly cool down the center temperature of the sheet from room temperature to -28°C; keep the temperature at -28°C, hold the temperature for 3.5h, and then At this temperature, the rolling rate is 8mm/s, and the rolling reduction rate is controlled to 8.5%;

B. Within 4h, slowly reduce the core temperature of the plate to -48°C; keep the temperature at -48°C, hold the holding time for 2.5h, roll at this temperature at a rolling rate of 5mm/s, and Control rolling reduction rate of 5.8%;

C. Within 6h, slowly reduce the center temperature of the plate to -62°C; keep the temperature at -62°C, hold the holding time for 22h, roll at this temperature at a rolling rate of 3mm/s, and control The rolling reduction rate is 2.5%;

D. Rapidly raise the core temperature of the plate to 175°C within 25min, and keep it for 3.5h;

E. The above-mentioned plate is subjected to cooling and aging treatment at a cooling rate of 6°C/h, and stored for 4 days.

Example 2

A post-processing method capable of improving the fatigue resistance of an aluminum alloy, comprising the following steps:

A. Put the quenched aluminum alloy sheet into the cold storage, and slowly cool down the center temperature of the sheet from room temperature to -30°C within 3h; keep the temperature at -30°C, hold the temperature for 3h, at this temperature Rolling is carried out at a rolling rate of 8 mm/s, and the rolling reduction rate is controlled to 8%;

B. Within 5h, slowly reduce the center temperature of the plate to -45°C; keep the temperature at -45°C, hold the holding time for 3h, roll at a rolling rate of 5mm/s at this temperature, and control The rolling reduction rate is 6%;

C. Within 8h, slowly reduce the center temperature of the plate to -65°C; keep the temperature at -65°C, hold the temperature for 18h, roll at a rolling rate of 3mm/s at this temperature, and control The rolling reduction rate is 2%;

D. Rapidly raise the center temperature of the plate to 150°C within 30min, and keep it for 5h;

E. The above-mentioned plate is subjected to cooling and aging treatment at a cooling rate of 5°C/h, and stored for 3 days.

Example 3

A post-processing method capable of improving the fatigue resistance of an aluminum alloy, comprising the following steps:

A. Put the quenched aluminum alloy sheet into the cold storage, and within 2h, slowly cool down the center temperature of the sheet from room temperature to -25°C; keep the temperature at -25°C, hold the temperature for 5h, at this temperature Rolling is carried out at a rolling rate of 8 mm/s, and the rolling reduction rate is controlled to 10%;

B. Within 3h, slowly reduce the center temperature of the plate to -50℃; keep the temperature at -50℃, hold the holding time for 2h, roll at this temperature at a rolling rate of 5mm/s, and control The rolling reduction rate is 5%;

C. Within 5h, slowly reduce the center temperature of the plate to -60°C; keep the temperature at -60°C, hold the holding time for 24h, roll at a rolling rate of 3mm/s at this temperature, and control The rolling reduction rate is 3%;

D. Rapidly raise the center temperature of the plate to 180°C within 20min, and keep it for 3h;

E. The above-mentioned plate is subjected to cooling and aging treatment at a cooling rate of 8°C/h, and stored for 5 days.

Comparative Example 1

The aluminum alloy is obtained by conventional artificial aging treatment.

Comparative Example 2

The step-by-step cooling in steps A-C is cancelled, and deep cold rolling at -65°C is directly used, and steps D and E remain unchanged to obtain an aluminum alloy.

Comparative Example 3: The aluminum alloy obtained by using the process of Example 3 of the invention patent CN110029297A.

The aluminum alloys prepared in Examples 1-3 and Comparative Examples 1-3 were tested below, and the following test results were obtained. The specific results are shown in Table 1.

Table 1: The detection results of the aluminum alloys prepared in Examples 1-3 and Comparative Examples 1-3;

It can be seen from the above test results that the post-processing method of the present invention can effectively improve the fatigue resistance of the aluminum alloy.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (5)

1. The post-treatment method capable of improving the fatigue resistance of the aluminum alloy is characterized by comprising the following steps of:

A. putting the aluminum alloy plate after quenching treatment into a refrigeration house, and slowly cooling the central temperature of the plate from room temperature to-30 to-25 ℃ within 2-3 h; keeping the temperature at minus 30 to minus 25 ℃, keeping the temperature for 3 to 5 hours, and rolling at the temperature;

B. slowly reducing the central temperature of the plate to-50 to-45 ℃ within 3-5 h; keeping the temperature at minus 50 to minus 45 ℃ and keeping the temperature for 2 to 3 hours, and rolling at the temperature;

C. slowly reducing the central temperature of the plate to-65 to-60 ℃ within 5-8 h; keeping the temperature at-65 to-60 ℃ and the heat preservation time at 18 to 24 hours, and rolling at the temperature;

D. rapidly raising the central temperature of the plate to 150-180 ℃ within 20-30 min, and preserving heat for 3-5 h;

E. and (3) cooling and aging the plate, and preserving for 3-5 days.

2. The post-treatment method for improving fatigue resistance of aluminum alloy as claimed in claim 1, wherein in step A, rolling is performed at a rolling speed of 8mm/s, and the rolling reduction is controlled to be 8-10%.

3. The post-treatment method for improving fatigue resistance of aluminum alloy as claimed in claim 1, wherein in step B, rolling is performed at a rolling speed of 5mm/s, and the rolling reduction is controlled to be 5-6%.

4. The method of post-treatment for improving fatigue resistance of aluminum alloy as claimed in claim 1, wherein in step C, rolling is performed at a rolling rate of 3mm/s, and the rolling reduction is controlled to be 2-3%.

5. The post-treatment method for improving the fatigue resistance of aluminum alloy as claimed in claim 1, wherein in the step E, the plate is subjected to temperature reduction aging treatment at a temperature reduction rate of 5-8 ℃/h.