CN111254331B

CN111254331B - Al-Zn-Mg alloy and preparation method thereof

Info

Publication number: CN111254331B
Application number: CN202010268600.1A
Authority: CN
Inventors: 郭辉; 容国富; 苏国忠; 范世通; 潘仁杰
Original assignee: Taishan Jinqiao Aluminum Profile Manufactory Co ltd
Current assignee: Taishan Jinqiao Aluminum Profile Manufactory Co ltd
Priority date: 2020-04-07
Filing date: 2020-04-07
Publication date: 2021-12-28
Anticipated expiration: 2040-04-07
Also published as: CN111254331A

Abstract

The invention relates to an Al-Zn-Mg alloy, which comprises the following components in percentage by weight: 0 to 0.2 percent of Si, 0 to 0.2 percent of Fe, 0.1 to 0.3 percent of Cu, 0 to 0.1 percent of Mn, 0.7 to 1.5 percent of Mg, 5.0 to 7.0 percent of Zn, 0.1 to 0.25 percent of Zr, 0.05 to 0.25 percent of Ti, and the balance of Al and inevitable impurities. Meanwhile, the invention also comprises a preparation method of the Al-Zn-Mg alloy and application of the Al-Zn-Mg alloy in preparing bumper profiles. The Al-Zn-Mg alloy material has smaller recrystallization texture, higher strength, better corrosion resistance, better room temperature mechanical property, good bending forming property, welding property and the like, and can realize the industrial mass production of Al-Zn-Mg alloy bumper profiles.

Description

Al-Zn-Mg alloy and preparation method thereof

Technical Field

The invention relates to the field of aluminum alloys, in particular to an Al-Zn-Mg alloy and a preparation method thereof.

Background

The Al-Zn-Mg (7003/7108/7039/7005) aluminum alloy cast rod has high mechanical property, welding property and corrosion resistance, and is widely applied to the fields of high-speed rails and automobiles. The production of the aluminum alloy section generally comprises smelting, casting, homogenizing annealing, extruding, cooling, stretching, natural standing, stamping and bending, welding, artificial aging and the like.

The existing process technology is in the stages of fusion casting extrusion and later-stage parking and bending forming:

the chemical composition design of the Al-Zn-Mg (7003/7108) material is not reasonable enough;

2. the design of the homogenization temperature is not reasonable enough, and single-stage homogenization treatment is mostly adopted (the temperature rise of the furnace is too much, and gradient control cannot be realized);

3. the design of the extrusion temperature is not very reasonable;

4. the extrusion speed is not reasonable enough;

5. the extrusion ratio is over designed;

6. the cooling rate is not reasonably designed;

7. after the section comes out, the section is parked without any treatment, and natural aging strengthening is accelerated.

The 7 aspects determine that the percentage of recrystallization of the extruded Al-Zn-Mg section is increased, so that the strength of the material is increased in the natural parking stage, the elongation rate is increased and then reduced, and the design rebound deformation of the later stamping and bending die and the service life of the die are directly determined.

In the production process of Al-Zn-Mg aluminum alloy bumpers, energy absorption boxes and longitudinal beams, how to control the bending property, the welding property, the fatigue property and the corrosion property of materials becomes a key, how to control the strengthening effect caused by the natural aging of the section before bending processing and how to control the section after pretreatment, so that the section after aging has comprehensive performance in the later period is a problem which needs to be solved urgently in the field.

Disclosure of Invention

Based on the defects of the prior art, the invention provides an Al-Zn-Mg alloy and a preparation method thereof.

The technical scheme adopted by the invention is as follows:

an Al-Zn-Mg alloy comprises the following components in percentage by weight: 0 to 0.2 percent of Si, 0 to 0.2 percent of Fe, 0.1 to 0.3 percent of Cu0.1 percent, 0 to 0.1 percent of Mn, 0.7 to 1.5 percent of Mg, 5.0 to 7.0 percent of Zn, 0.1 to 0.25 percent of Zr, 0.05 to 0.25 percent of Ti, and the balance of Al and inevitable impurities.

Preferably, the components thereof comprise by weight percent: 0.1 to 0.2 percent of Si, 0.1 to 0.2 percent of Fe, 0.2 to 0.3 percent of Cu, 0.02 to 0.1 percent of Mn, 0.7 to 1.0 percent of Mg, 5.0 to 6.0 percent of Zn, 0.1 to 0.2 percent of Zr, 0.05 to 0.2 percent of Ti, and the balance of Al and inevitable impurities.

More preferably, the components thereof comprise by weight percent: 0.15% of Si, 0.15% of Fe, 0.25% of Cu, 0.07% of Mn, 0.8% of Mg, 5.5% of Zn, 0.15% of Zr, 0.1% of Ti, and the balance of Al and inevitable impurities.

The invention also comprises a preparation method of the Al-Zn-Mg alloy, which comprises the following steps:

s1, smelting: melting the Al-Zn-Mg alloy material, and using electromagnetic stirring to ensure that the alloy is uniformly diffused in the melt; controlling the temperature of the melt in the smelting process to be not more than 800 ℃ and the smelting time to be not more than 5 h;

s2, casting: casting the solution into an alloy casting body; the casting temperature is controlled between 710 and 730 ℃, the die disc temperature is controlled between 690 and 710 ℃, and the cooling water pressure is controlled between 0.02MPa and 0.2 MPa;

s3, homogenizing annealing: homogenizing and heating the alloy casting body to form an alloy casting rod;

s4, extruding: carrying out extrusion treatment on the homogenized Al-Zn-Mg cast rod to obtain an alloy extruded body;

s5, cooling: cooling the alloy extruded body;

s6, pretreatment: preheating the cooled alloy extrusion body for 24 hours;

s7, subsequent treatment: standing and carrying out other treatments to obtain the Al-Zn-Mg alloy.

Further, the homogenization treatment in step S3 adopts a three-stage homogenization process, specifically: the first-stage temperature is controlled to be between 50 ℃/h and 260-320 ℃, and the temperature is kept for 2-4 h; the temperature of the second stage is controlled to be not more than 50 ℃/h and is increased to 380-420 ℃, and the temperature is kept for 2-6 h; the third-stage temperature is controlled to be not more than 50 ℃/h, the temperature is raised to be between 460 and 500 ℃, the temperature is kept for 4 to 8h, and then the product is taken out of the furnace and cooled in air.

The main purpose of homogenizing annealing is to reduce the segregation of chemical components and the nonuniformity of structures caused in the casting process of the aluminum alloy ingot, heat the ingot to high temperature, preserve heat for a long time, and then slowly cool the ingot so as to achieve the purpose of homogenizing the chemical components and the structures. In the Al-Zn-Mg profile, the distribution and the size of disperse phase Al3Zr particles directly determine the recrystallization degree in the extrusion process, and the smaller the size of Al3Zr particles is, the smaller the size is, the more the particles are distributed in the vicinity of grain boundaries, and the growth of recrystallized grains can be effectively inhibited in the extrusion process. The invention adopts three-stage homogenization for the purpose of precipitating finer particles from Al3Zr particles in the matrix, and is beneficial to inhibiting the recrystallization of crystal grains.

Further, in the step S4, high-temperature and high-speed extrusion is adopted during extrusion, an aluminum alloy cast rod with the diameter of 127-508mm is placed into an extrusion cylinder of 1000T-8000T for extrusion, and the extrusion ratio is 10-50; the temperature range of the casting rod is set between the head temperature of 460-520 ℃, the tail temperature of 440-500 ℃, the temperature range of the extrusion cylinder is set between 400-440 ℃, the extrusion speed is set to be 2.4-6.0 mm/s, and the discharging speed of the section bar is controlled to be 5-15 m/min.

The extrusion is a plastic processing method for obtaining the required alloy section by placing a casting rod heated to a certain temperature in an extrusion cylinder and applying external force to make the casting rod flow out of a shunting die. The extrusion temperature of the present invention is designed so that the material retains sufficient fibrous and sub-crystalline grain structure after extrusion.

Further, in the step S5, cooling is carried out by adopting strong wind or water mist, the cooling rate is more than or equal to 25 ℃/S, and the temperature after cooling is not more than 150 ℃.

Since the higher the extrusion temperature, the higher the degree of solid solution will be. If adopt superstrong forced air cooling or the water smoke cooling of miniproportion behind the extrusion for the material reaches the solid solubility of certain degree, and the material cooperates great cooling rate again, can form great solid solution tissue, in the natural ageing stage in later stage, can form more GPI district and GPII district sooner, makes the speed of natural ageing accelerate, is unfavorable for the crooked processing of punching press in later stage.

Further, the pretreatment equipment in the step S6 is an aging furnace, the temperature is controlled between 140 ℃ and 200 ℃, the time is controlled between 0 h and 4h, the furnace needs to be preheated to between 120 ℃ and 200 ℃, and the material is discharged from the furnace and needs to be cooled by air.

The pretreatment process aims to enable the aluminum alloy extruded section to reach a pre-aging state in advance, so that a part of GP zone is dissolved back, or eta' and eta phase are separated out, and the mechanical property of the material is within a state value of 24-48h after extrusion; the strengthening effect caused by natural aging is slowed down.

Further, step S7 includes artificial aging treatment, the aging temperature is controlled at 90-110 ℃, and the temperature is kept for 4-8 h; then the temperature is kept for 10-18h at 145-170 ℃.

After aging treatment, the tensile strength of the material is finally between 375-395MPa, the yield strength is between 345-365MPa, the uniform elongation is between 8-12 percent, and the A50 is between 12-18 percent.

The invention also comprises application of the Al-Zn-Mg alloy prepared by the method in preparing bumper profiles.

According to the Al-Zn-Mg alloy disclosed by the invention, the recrystallized grain structure and the natural aging strengthening power generated in the extrusion process are adjusted through the extrusion process and pretreated at a certain temperature after the extrusion is finished, so that the natural aging strengthening power of the material is inhibited, eta' and eta phase are precipitated in advance, the aluminum alloy profile material reaches a relatively stable stage, and the material has lower mechanical property and extremely low natural aging strengthening capability; the thickness of the recrystallized layer of the extruded profile is not more than 3% of the wall thickness by the adjusted extrusion process.

The Al-Zn-Mg alloy material has smaller recrystallization texture, higher strength, better corrosion resistance, better room temperature mechanical property, good bending forming property, welding property and the like, and can realize the industrial mass production of Al-Zn-Mg alloy bumper profiles.

Detailed Description

Example 1

An Al-Zn-Mg alloy comprises the following components in percentage by weight: 0.1% of Si, 0.1% of Fe, 0.1% of Cu, 0.01% of Mn, 0.7% of Mg, 5.00% of Zn, 0.1% of Zr, 0.05% of Ti, and the balance of Al and inevitable impurities.

The preparation method of the alloy specifically comprises the following steps:

1. smelting: the raw materials of the Al-Zn-Mg alloys described in examples 1 to 3 were melted to ensure that the respective components were sufficiently uniformly diffused into the respective portions of the solution.

In the smelting part of the embodiment, electromagnetic stirring is used, so that the alloy is uniformly diffused in the melt; the temperature of the melt in the smelting process is controlled to be not more than 800 ℃, and the smelting time is not more than 5 h.

2. Casting: s2, casting: the solution is cast into an alloy cast body.

The casting temperature of the embodiment is controlled between 710 ℃ and 730 ℃, the die plate temperature is controlled between 680 ℃ and 700 ℃, and the cooling water pressure is controlled between 0.02MPa and 0.03 MPa.

3. Homogenizing and annealing: and uniformly heating the alloy casting body to form an alloy casting rod.

In this embodiment, the homogenization treatment adopts a three-stage homogenization process, which specifically comprises: the first-stage temperature is controlled to be between 50 ℃/h and 260-320 ℃, and the temperature is kept for 2-4 h; the temperature of the second stage is controlled to be not more than 50 ℃/h and is increased to 380-420 ℃, and the temperature is kept for 2-6 h; the third-stage temperature is controlled to be not more than 50 ℃/h, the temperature is raised to be between 460 and 500 ℃, the temperature is kept for 4 to 8h, and then the product is taken out of the furnace and cooled in air.

4. Extruding: and extruding the homogenized Al-Zn-Mg cast rod to obtain an alloy extruded body.

In the extrusion of the embodiment, high-temperature and high-speed extrusion is adopted, and an aluminum alloy cast rod with the diameter of 127-508mm is placed into an extrusion cylinder of 1000T-8000T for extrusion, wherein the extrusion ratio is 10-50; the temperature range of the casting rod is set between the head temperature of 460-520 ℃, the tail temperature of 440-500 ℃, the temperature range of the extrusion cylinder is set between 400-440 ℃, the extrusion speed is set to be 2.4-6.0 mm/s, and the discharging speed of the section bar is controlled to be 5-15 m/min.

5. And (3) cooling: and cooling the alloy extruded body.

The cooling of the embodiment adopts strong wind cooling or water mist cooling, the cooling rate is more than or equal to 25 ℃/s, and the temperature after cooling is not more than 150 ℃.

6. Pretreatment: and carrying out preheating treatment on the cooled alloy extruded body for 24 h.

The pretreatment equipment in the embodiment is an aging furnace, the temperature is controlled to be 140-200 ℃, the time is controlled to be 0-4h, the furnace needs to be preheated to be 120-200 ℃, and air cooling is needed for discharging materials.

7. And (3) subsequent treatment: standing and carrying out other treatments to obtain the Al-Zn-Mg alloy.

The subsequent treatment of the embodiment also comprises artificial aging treatment, wherein the aging temperature is controlled at 90-110 ℃ and is kept for 4-8 h; then the temperature is kept for 10-18h at 145-170 ℃.

Through the adjustment of the extrusion process and the pretreatment at a certain temperature after the extrusion is finished, the dynamic force of the natural aging strengthening of the material is inhibited, eta' and eta phase are precipitated in advance, the aluminum alloy profile material reaches a relatively stable stage, and the material has lower mechanical property and extremely low natural aging strengthening capability; after the adjusted extrusion process, the thickness of a recrystallization layer of the extruded section is not more than 3% of the wall thickness, the section is naturally parked in a state without any pretreatment, the tensile strength is gradually increased from 270MPa to about 350MPa, the yield strength is gradually increased from 160MPa to about 230MPa, and the hardness is gradually increased from HW 7 to HW 16; after the pretreatment, the tensile strength of the section is gradually increased from 270MPa to about 300MPa and then is kept unchanged; the yield strength is gradually increased from 160MPa to about 190MPa and then is kept unchanged; the HW is gradually increased to be 7 and then is kept unchanged after the HW is gradually increased to be 12;

the final material is naturally placed for 7-15 days after pretreatment, the performance change is small, the good stamping deformation capability is still kept, the rebound deformation after stamping is extremely small, and the material reaches a stable state.

Example 2

An Al-Zn-Mg alloy comprises the following components in percentage by weight: 0.2% of Si, 0.2% of Fe, 0.3% of Cu, 0.1% of Mn, 1.5% of Mg, 7.0% of Zn, 0.25% of Zr, 0.25% of Ti, and the balance of Al and inevitable impurities. The preparation method is the same as that of example 1.

Example 3

An Al-Zn-Mg alloy comprises the following components in percentage by weight: 0.1% of Si, 0.1% of Fe, 0.2% of Cu, 0.02% of Mn, 0.7% of Mg, 5.0% of Zn, 0.1% of Zr, 0.05% of Ti, and the balance of Al and inevitable impurities. The preparation method is the same as that of example 1.

Example 4

An Al-Zn-Mg alloy comprises the following components in percentage by weight: 0.2% of Si, 0.2% of Fe, 0.3% of Cu, 0.1% of Mn, 1.0% of Mg, 6.0% of Zn, 0.2% of Zr, 0.2% of Ti, and the balance of Al and inevitable impurities. The preparation method is the same as that of example 1.

Example 5

An Al-Zn-Mg alloy comprises the following components in percentage by weight: 0.15% of Si, 0.15% of Fe, 0.25% of Cu, 0.07% of Mn, 0.8% of Mg, 5.5% of Zn, 0.15% of Zr, 0.1% of Ti, and the balance of Al and inevitable impurities. The preparation method is the same as that of example 1.

Example 6

An Al-Zn-Mg alloy bumper profile, made from the profile described in example 5.

In the embodiment, the extruded section is subjected to pre-aging treatment within 8h, the temperature is 150 ℃, and the time is 1 h; then standing for 0 day, 7 days, 15 days, 30 days and 90 days respectively, and comparing the states at different times to carry out room temperature tensile mechanical property tests, wherein the test results are shown in table 1. Room temperature tensile mechanical property tests were performed for each standing time in the final aging state, and the test results are shown in table 2.

TABLE 1 tensile mechanical properties at room temperature for different residence times after preaging of the alloys

Parking time/day	Tensile strength/MPa	Yield strength/MPa	Elongation/percent
				0	272	165	7
7	288	179	9
				15	296	182	11
30	298	188	12
				90	303	193	12

TABLE 2 tensile mechanical properties at room temperature of the alloys after final aging treatment at different dwell times

Parking time/day	Tensile strength/MPa	Yield strength/MPa	Elongation/percent
				0	392	365	13
7	387	360	15.5
				15	373	355	16
30	371	350	16.5
				90	376	349	17

As can be seen from the above table, the Al-Zn-Mg alloy material described in this embodiment has a smaller recrystallization texture, higher strength, better corrosion resistance, better room temperature mechanical properties, good bending formability, welding properties, and the like, so that industrial mass production of the Al-Zn-Mg alloy bumper profiles can be realized.

Similarly, room temperature tensile mechanical tests on the sectional materials of examples 1 to 4 also show that the corresponding alloy sectional materials have good room temperature mechanical properties, good bending formability, welding performance and the like, and are very suitable for being used as bumper sectional materials.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.

Claims

1. An Al-Zn-Mg alloy is characterized by comprising the following components in percentage by weight: 0 to 0.2 percent of Si, 0 to 0.2 percent of Fe, 0.1 to 0.3 percent of Cu, 0 to 0.1 percent of Mn, 0.7 to 1.5 percent of Mg, 5.0 to 7.0 percent of Zn, 0.1 to 0.25 percent of Zr, 0.05 to 0.25 percent of Ti, and the balance of Al and inevitable impurities;

the preparation method of the Al-Zn-Mg alloy comprises the following steps:

s1, smelting: melting the raw materials of the Al-Zn-Mg alloy, and using electromagnetic stirring to ensure that the alloy is uniformly diffused in the melt; controlling the temperature of the melt in the smelting process to be not more than 800 ℃ and the smelting time to be not more than 5 h;

s2, casting: casting the molten liquid into an alloy casting body; the casting temperature is controlled between 710 ℃ and 730 ℃, the temperature of the die plate is controlled between 690 ℃ and 710 ℃, and the cooling water pressure is controlled between 0.02MP a and 0.2MP a;

s5, cooling: cooling the alloy extruded body;

s6, pretreatment: preheating the cooled alloy extrusion body for 24 hours;

s7, subsequent treatment: standing and carrying out other treatments to obtain the Al-Zn-Mg alloy;

wherein, the homogenization treatment in the step S3 adopts a three-level homogenization process, which specifically comprises: the first-stage temperature is controlled to be between 50 ℃/h and 260-320 ℃, and the temperature is kept for 2-4 h; the temperature of the second stage is controlled to be not more than 50 ℃/h and is increased to 380-420 ℃, and the temperature is kept for 2-6 h; the third-stage temperature is controlled to be not more than 50 ℃/h, the temperature is raised to be between 460 and 500 ℃, the temperature is kept for 4 to 8h, and then the product is taken out of the furnace and cooled in air.

2. The Al-Zn-Mg alloy according to claim 1, comprising, in weight percent: 0.1 to 0.2 percent of Si, 0.1 to 0.2 percent of Fe, 0.2 to 0.3 percent of Cu, 0.02 to 0.1 percent of Mn, 0.7 to 1.0 percent of Mg, 5.0 to 6.0 percent of Zn, 0.1 to 0.2 percent of Zr, 0.05 to 0.2 percent of Ti, and the balance of Al and inevitable impurities.

3. The Al-Zn-Mg alloy according to claim 1, comprising, in weight percent: 0.15% of Si, 0.15% of Fe, 0.25% of Cu, 0.07% of Mn, 0.8% of Mg, 5.5% of Zn, 0.15% of Zr, 0.1% of Ti, and the balance of Al and inevitable impurities.

4. The Al-Zn-Mg alloy as claimed in claim 1, wherein the step S4 of extruding is carried out by high-temperature high-speed extrusion, wherein an aluminum alloy cast rod with a diameter of 127-508mm is placed in an extrusion cylinder of 1000T-8000T for extrusion at an extrusion ratio of 10-50; the temperature range of the casting rod is set between the head temperature of 460-520 ℃, the tail temperature of 440-500 ℃, the temperature range of the extrusion cylinder is set between 400-440 ℃, the extrusion speed is set to be 2.4-6.0 mm/s, and the discharging speed of the section bar is controlled to be 5-15 m/min.

5. The Al-Zn-Mg alloy according to claim 1, wherein the cooling in step S5 is by forced air cooling or water mist cooling, the cooling rate is not less than 25 ℃/S, and the temperature after cooling is less than 150 ℃.

6. The Al-Zn-Mg alloy as claimed in claim 1, wherein the pretreatment equipment in step S6 is an aging furnace, the temperature is controlled at 140-200 ℃, the time is controlled at 4h, the furnace needs to be preheated to 120-200 ℃, and the material is discharged by air cooling.

7. The Al-Zn-Mg alloy according to claim 1, wherein the step S7 comprises artificial aging treatment, the aging temperature is controlled at 90-110 ℃ and kept for 4-8 h; then the temperature is kept for 10-18h at 145-170 ℃.

8. Use of an Al-Zn-Mg alloy according to any one of claims 1 to 7 for the production of bumper profiles.