CN115522107A

CN115522107A - 7-series high-strength high-bending-resistance anti-collision cross beam for automobile and manufacturing method thereof

Info

Publication number: CN115522107A
Application number: CN202211168686.6A
Authority: CN
Inventors: 崔家铭
Original assignee: Min Ta Al Tech Taicang Co ltd
Current assignee: Min Ta Al Tech Taicang Co ltd
Priority date: 2022-09-24
Filing date: 2022-09-24
Publication date: 2022-12-27

Abstract

The invention relates to the technical field of metal processing, and discloses a 7-series high-strength high-bending-resistance anti-collision cross beam for an automobile, wherein the cross beam is made of the following metal materials in parts by weight: si is less than or equal to 0.12%, fe: less than or equal to 0.20%, cu:0.14% -0.20%, mn: less than or equal to 0.05 percent, mg:0.85% -0.95%, cr: less than or equal to 0.05 percent, zn:5.5% -6.0%, zr:0.14% -0.17%, ti: less than or equal to 0.1 percent and the balance of Al. According to the 7-series high-strength high-bending-resistance anti-collision cross beam for the automobile and the manufacturing method thereof, the material components and the extrusion process parameters are strictly controlled, the sectional material is subjected to pre-aging treatment, the mechanical property of the sectional material is in a low-strength stable state, and the adverse effect caused by the fact that the product performance fluctuation is not fixed due to the fact that the T4 parking time is too long and the product processing time is shortened is reduced; the final product performance 7003-T6 after T6 aging can reach Rp0.2 not less than 350Mpa, rm not less than 390Mpa and A50 not less than 12%, and the section bar has not only higher strength but also higher bending resistance after being extruded and finally T6 aging, the pressing amount of the cross beam section bar after three-point bending can reach more than 150mm without cracking, and all indexes are far higher than the national standard performance requirements.

Description

7-series high-strength high-bending-resistance anti-collision cross beam for automobile and manufacturing method thereof

Technical Field

The invention relates to the technical field of metal processing, in particular to a 7-series high-strength high-bending-resistance anti-collision cross beam for an automobile and a manufacturing method thereof.

Background

The 7 series belongs to an Al-Zn-Mg series, has higher strength, good weldability and excellent corrosion resistance, and has more applications in the aspects of vehicles, buildings, bridges, industrial equipment, large pressure vessels and the like. Because the aluminum anti-collision system for the automobile pursues high strength, the anti-collision beam needs larger strength to resist deformation in the process of carrying out a simulation collision test on the automobile, 6 series of aluminum profiles with higher strength design requirements for the anti-collision system cannot meet the requirements of the anti-collision beam for the automobile, 7 series of aluminum profiles are selected to be firmer and more reliable along with market development, and products manufactured by extrusion of the aluminum profile have the advantages of high strength, light weight, corrosion resistance, weldability, easy maintenance and the like, so that the 7 series of aluminum profiles are more and more applied in the automobile industry;

through the adjustment of the existing process parameters, namely the proportion of Mg and Zn is adjusted by optimizing the components, the characteristics of 7003 low quenching sensitivity are kept by the adjusted components; after the section bar is extruded, a 7003-T4 state product needs to be subjected to stretch bending processing, a 7 series product has a strong parking effect after being extruded, the 7003-T4 mechanical strength is gradually increased along with the prolonging of the parking time, the instability of mechanical properties has adverse effects on the subsequent stretch bending processing, the product is not easy to be subjected to stretch bending processing forming, and the problems of product size precision, surface quality reduction and the like are easily caused.

Disclosure of Invention

Technical problem to be solved

Aiming at the defects of the prior art, the invention provides a 7-series high-strength high-bending-resistance anti-collision cross beam for an automobile and a manufacturing method thereof, which have the advantages of more stable mechanical property, easier forming in subsequent processing, higher product size precision and surface quality and the like, and solve the problems that the instability of the mechanical property of the existing metal material has adverse effect on the subsequent stretch bending processing, the product is not easy to stretch bend and form, and the size precision and the surface quality of the product are easy to reduce and the like.

(II) technical scheme

In order to realize the purposes of more stable mechanical property, easier molding in subsequent processing and higher product dimensional precision and surface quality, the invention provides the following technical scheme: a7-series high-strength high-bending-resistance anti-collision crossbeam for an automobile is characterized in that a crossbeam metal material is composed of the following proportioning elements: si is less than or equal to 0.12%, fe: less than or equal to 0.20%, cu:0.14% -0.20%, mn: less than or equal to 0.05 percent, mg:0.85% -0.95%, cr: less than or equal to 0.05 percent, zn:5.5% -6.0%, zr:0.14% -0.17%, ti: less than or equal to 0.1 percent and the balance of Al.

Preferably, the 7-series high-strength and high-bending-resistance anti-collision cross beam for the automobile is made of the following metal materials in parts by weight: si is less than or equal to 0.12%, fe: less than or equal to 0.20 percent, cu:0.05%, mn: less than or equal to 0.05 percent, mg:0.78% -0.80%, cr: less than or equal to 0.05 percent, zn:5.5% -6.0%, zr:0.14% -0.17%, ti: less than or equal to 0.1 percent and the balance of Al.

Preferably, a small amount of H element is added into the beam metal during production, wherein the content of H is less than or equal to 0.20ml/100g.

The invention provides a manufacturing method of a 7-series high-strength high-bending-resistance anti-collision cross beam for an automobile, which comprises the following steps:

designing a mold A: the 7-series alloy has high mechanical property and hard material, the extrusion die is easy to damage and has short service life, and the surface quality of the extruded section is poor, so the feeding port of the die adopts a downstream structural design, the bearing pressure in the unit area of the extrusion die is reduced, the service life of the die is prolonged, the outlet of the die is designed into a structure for introducing nitrogen to the surface of the section, and the chemical property of the nitrogen is stable, so the outlet is controlled by the nitrogen atmosphere, the oxidation of aluminum and the bonding and accumulation of aluminum oxide are reduced, and the introduction of the nitrogen not only improves the extrusion speed, but also can obviously improve the surface quality of a product;

b, casting rod homogenization: the method adopts low-temperature long-time homogenization treatment at 470 ℃ multiplied by 16H, and air-cooled cooling at the early stage and water-cooled cooling at the later stage to room temperature, so that alloy elements are fully dissolved and homogenized, crystalline phases generated by non-equilibrium solidification are eliminated, intragranular segregation (dendrite segregation) is eliminated, the internal stress of cast ingots is eliminated, the surface quality of the extruded section after stretch bending can be improved through full homogenization treatment, and the defects of surface pitting, lines, roughness reduction and the like are avoided after the extruded section is processed. (ii) a

C, extrusion process: the method is characterized in that a horizontal 4000T extruder is used, the weight of the section is 4.217kg/m, the extrusion ratio is 51, the heating temperature of a die is 480-500 ℃, the heating temperature of an ingot is 460-480 ℃, the extrusion speed of the section is 4-6m/min, the quenching process adopts air mist cooling, the temperature of the quenched section is less than 80 ℃, the 7-series alloy section is easy to over-fire and is not suitable for high-temperature extrusion, the growth of recrystallized grains can be prevented on the basis of ensuring the extrusion property due to the low quenching sensitivity characteristic of 7003 alloy, and the qualified size of the section is ensured due to the air mist cooling quenching process. (ii) a

D, straightening on line: strictly controlling the elongation of the section bar to be 0.5-1.0%, stretching and straightening the section bar on the basis of ensuring the qualified dimension, and improving the mechanical strength of the material in a T4 state by a certain amount of deformation of the extruded aluminum alloy to prepare for subsequent pre-aging;

e, a heat treatment process: the extruded section bar is subjected to low-temperature short-time pre-aging treatment to enable the mechanical property of the material to reach a low-strength stable state, and the pre-aging system is as follows: multiplying 30min at 160 ℃; after the section is subjected to stretch bending processing, the final section T6 adopts a single-stage aging system, the time of a heating section is increased for ensuring the mechanical property after aging, and the aging system is as follows: the temperature is increased to 7h,145 ℃ and 6h, the T6 performance of the final product meets 7003-T6, rp0.2 is more than or equal to 350Mpa, rm is more than or equal to 390Mpa, and A50 is more than or equal to 12%.

(III) advantageous effects

Compared with the prior art, the invention provides a 7-series high-strength high-bending-resistance anti-collision cross beam for an automobile and a manufacturing method thereof, and the anti-collision cross beam has the following beneficial effects: according to the 7-series high-strength high-bending-resistance anti-collision beam for the automobile and the manufacturing method thereof, through strict control of material components and extrusion process parameters, an extruded product can meet the high-precision standard of extrusion tolerance GB/T14846, the sectional material is subjected to pre-aging treatment, the mechanical property of the sectional material is in a low-strength stable state, and the adverse effect caused by unfixed product performance fluctuation due to overlong T4 parking time of the product is reduced; the final product performance 7003-T6 after T6 aging can reach Rp0.2 not less than 350Mpa, rm not less than 390Mpa and A50 not less than 12%, and the section bar has not only higher strength but also higher bending resistance after being extruded and finally T6 aging, the pressing amount of the cross beam section bar after three-point bending can reach more than 150mm without cracking, and all indexes are far higher than the national standard performance requirements.

Drawings

FIG. 1 is a sectional view of a 7-series high-strength and high-bending-resistance anti-collision cross beam structure for an automobile, according to the present invention;

fig. 2 is a three-point bending test diagram of a 7-series high-strength high-bending-resistance anti-collision cross beam structure for an automobile.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.

Example one

Referring to fig. 1-2, a 7-series high-strength and high-bending-resistance anti-collision cross beam for an automobile is disclosed, wherein the cross beam is made of the following metal materials in parts by weight: si is less than or equal to 0.12%, fe: less than or equal to 0.20%, cu:0.14% -0.20%, mn: less than or equal to 0.05 percent, mg:0.85% -0.95%, cr: less than or equal to 0.05 percent, zn:5.5% -6.0%, zr:0.14% -0.17%, ti: less than or equal to 0.1 percent and the balance of Al.

Example two

A7-series high-strength high-bending-resistance anti-collision cross beam for an automobile is characterized in that a metal material of the cross beam consists of the following proportioning elements: si is less than or equal to 0.12%, fe: less than or equal to 0.20 percent, cu:0.05%, mn: less than or equal to 0.05 percent, mg:0.78% -0.80%, cr: less than or equal to 0.05 percent, zn:5.5% -6.0%, zr:0.14% -0.17%, ti: less than or equal to 0.1 percent and the balance of Al.

When the alloy material is produced, the content of impurity elements Fe and Si is strictly limited, the main strengthening phase of the 7-series alloy is eta-phase MgZn2, the microstructure is a hexagonal lattice structure and belongs to Zn excess alloy, and the excess Zn is controlled to be about 1 percent; the mechanical strength of the alloy can be obviously improved by adding a small amount of Cu into the alloy; meanwhile, the low quenching sensitivity of the alloy is ensured, mn and Cr elements are not added in the alloy proportion, a small amount of Zr element is added to replace Mn and Cr, the crystal grains can be refined, the tissue structure is improved, the comprehensive performance of the material is improved, and meanwhile, the weldability is improved by adding a small amount of Zr element.

The mixture ratio of the two components is detailed in the following table 1, and the mechanical property results are detailed in the following table 2.

TABLE 1 aluminum alloy chemical composition (mass fraction/%)

TABLE 2 summary of mechanical Properties of the different Components products

And (3) analyzing a test result: under the same extrusion process state, the mechanical property result shows that the component 1 is obviously higher than the component 2, the two are mainly different in Cu and Mg contents, and the improvement of the Cu and Mg contents of the 7-series alloy in a certain component range can improve the mechanical strength of the extruded section after aging; t6 aging system: heating for 7h,145 ℃ and 6h; component 1: t6 mechanical properties, rp0.2:360mpa, rm:405mpa, A50:16.6%, ingredient 2: t6 mechanical properties, rp0.2:325MPa, rm:374mpa, A50:17.2 percent, the comprehensive comparison component 1 has mechanical property superior to that of the component 2, the yield strength and the tensile strength of the component 1 are improved by more than 100Mpa compared with the traditional 6-series alloy, the elongation A50 after fracture is improved by about 6 to 8 percent compared with the traditional 6-series alloy, and the mechanical property far exceeds the national standard requirement of performance.

designing a mold: the 7-series alloy has high mechanical property and hard material, the extrusion die is easy to damage and has short service life, and the surface quality of the extruded section is poor, so the feeding port of the die adopts a downstream structural design, the bearing pressure in the unit area of the extrusion die is reduced, the service life of the die is prolonged, the outlet of the die is designed into a structure for introducing nitrogen to the surface of the section, and the chemical property of the nitrogen is stable, so the outlet is controlled by the nitrogen atmosphere, the oxidation of aluminum and the bonding and accumulation of aluminum oxide are reduced, and the introduction of the nitrogen not only improves the extrusion speed, but also can obviously improve the surface quality of a product;

D, straightening on line: strictly controlling the elongation of the section bar to be 0.5-1.0%, and stretching and straightening the section bar on the basis of ensuring the qualified size, wherein a certain amount of deformation of the extruded aluminum alloy can improve the mechanical strength of the material in a T4 state and is prepared for subsequent pre-aging;

e, a heat treatment process: the extruded section bar is subjected to low-temperature short-time pre-aging treatment to enable the mechanical property of the material to reach a low-strength stable state, and the pre-aging system is as follows: multiplying the temperature at 160 ℃ for 30min; after the section is subjected to stretch bending processing, the final section T6 adopts a single-stage aging system, the time of a heating section is increased for ensuring the mechanical property after aging, and the aging system is as follows: the temperature is increased to 7h,145 ℃ and 6h, the T6 performance of the final product meets 7003-T6, rp0.2 is more than or equal to 350Mpa, rm is more than or equal to 390Mpa, and A50 is more than or equal to 12%.

The 7-series section bar has the advantages of pre-aging treatment: the mechanical property of the product of the section after pre-aging is in a low-strength stable state, and the ratio of the mechanical strength increase trend within 20 days after extrusion to the product without pre-aging treatment is shown in the following table;

TABLE 3 summary of profile parking mechanical Properties

Description of the invention: the mechanical test sample section sampling is continuous sampling at adjacent positions of the same extruded section, and the influence of the extrusion process or performance fluctuation among batches is eliminated;

the profile parking test data show that: the mechanical property of the pre-aged section product is relatively stable, the anti-tensile strength after pre-aging has a certain reduction effect (about 30MPa reduction), the yield strength and tensile strength within 20 days have relatively small fluctuation (the fluctuation is less than 20 MPa), the yield strength and tensile strength within 20 days have large fluctuation (the yield strength fluctuation is more than 50MPa, and the tensile strength fluctuation is more than 60 MPa), the mechanical strength still slightly rises along with the continuous extension of the parking time, the elongation after fracture shows a relatively stable state, and the average elongation after fracture of the pre-aged section product is about 1 percent compared with the elongation after fracture of the non-pre-aged section product; the mechanical strength deviation of the product is large when the T4 processing parking time of the sectional material product is unfixed, the longer the parking time before processing is, the higher the mechanical strength of the sectional material is, the harder the product is, the instability of the stretch bending process is caused, the product after the pre-aging treatment can effectively solve the problem, the relatively stable low-strength mechanical property state not only makes the forming processing easier, but also can improve the processing size precision of the product, reduce the resilience amount, and improve the surface quality and the processing qualified rate.

Three-point bending test:

and (4) analyzing results: the three-point bending test equipment for the section is a universal testing machine, the diameter of a pressure head is 180mm, the length of the section is 1500mm, the pressing speed is 50mm/min, the section subjected to T6 aging is subjected to three-point bending test, the experimental result shows that the section with the pressing distance exceeding 150mm does not crack when the pressure head is in contact with the section, the section shows good toughness indexes, and the requirement of the section on high bending resistance can be completely met. Metallographic test:

the experimental equipment is a Nikon metallographic analyzer with the magnification of 100X, and the cross section surface of the polished section is subjected to acid corrosion by adopting anode coating HBF4 for a test sample.

And (4) analyzing results: metallographic results show that the alloy has a recrystallized grain structure (coarse grain layer) on the outer walls of two sides along the whole wall thickness direction, the matrix has a fibrous grain structure, the thickness of the coarse grain layer in the transverse direction is not obviously different from that in the longitudinal direction, the thickness of the coarse grain layer on one side is about 80-150 mu m, and the total thickness of the coarse grain layers on the two sides accounts for about 3-5% of the whole wall thickness, so that the high-quality requirement of an extruded section on the thickness of the coarse grain layer with a high-power metallographic structure is completely met.

Low power and weld flaring test:

the head and tail materials of the section bar have no defects of tail shrinkage, cracks and the like in a low power mode after being subjected to alkali soaking; the cracking position of the flaring does not have a clean smooth fracture, the flaring is shown as the tearing of a sawtooth-shaped or rough edge surface, and can also be shown as the spiral tearing of a test piece; the low power and flaring result meets the quality requirements of the extruded hollow section on sodium silicate and flaring;

TABLE 3 head tailing Low fold results

TABLE 4 Flared test results

The invention has the beneficial effects that: by strictly controlling the material components and the extrusion process parameters, the extruded product can meet the high-precision standard of the extrusion tolerance GB/T14846, the sectional material is subjected to pre-aging treatment, the mechanical property of the sectional material is in a low-strength stable state, and the adverse effect caused by the fact that the product processing time is not fixed and the product performance fluctuation is reduced because the T4 standing time is too long; the final product performance 7003-T6 after T6 aging can reach Rp0.2 not less than 350Mpa, rm not less than 390Mpa and A50 not less than 12%, and the section bar has not only higher strength but also higher bending resistance after being extruded and finally T6 aging, the pressing amount of the cross beam section bar after three-point bending can reach more than 150mm without cracking, and all indexes are far higher than the national standard performance requirements;

with the pursuit of high strength and high safety of automobiles, the proportion of Mg and Si needs to be improved when the performance of the traditional 6-series alloy section is improved, the quenching sensitivity is relatively high due to high alloying components of the 6-series alloy, and the size of the section is difficult to control. The 7-series beam alloy keeps the characteristic of low quenching sensitivity, the size of the profile is well guaranteed, the mechanical strength and the bending resistance of the traditional 6-series anti-collision beam profile are greatly improved, the performance index of aluminum extruded materials in China is improved, the process technology reaches the world advanced level, the successful research and development and application of the profile accelerate the development of the aluminum extruded profile on automobile structural parts, the weight of the whole automobile is reduced, the safety performance of the automobile is further improved, the pre-aging application of the extruded profile product effectively solves the problem that the mechanical strength is greatly increased due to overlong 7003 alloy parking time, and the application has great significance to actual production.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The utility model provides a 7 are crashproof crossbeam of high strength high bending resistance for car which characterized in that: the beam metal material is composed of the following proportioning elements: si is less than or equal to 0.12%, fe: less than or equal to 0.20%, cu:0.14% -0.20%, mn: less than or equal to 0.05 percent, mg:0.85% -0.95%, cr: less than or equal to 0.05 percent, zn:5.5% -6.0%, zr:0.14% -0.17%, ti: less than or equal to 0.1 percent and the balance of Al.

2. The 7-series high-strength high-bending-resistance anti-collision cross beam for the automobile according to claim 1, characterized in that: the beam metal material is composed of the following proportioning elements: si is less than or equal to 0.12%, fe: less than or equal to 0.20%, cu:0.05%, mn: less than or equal to 0.05 percent, mg:0.78% -0.80%, cr: less than or equal to 0.05 percent, zn:5.5% -6.0%, zr:0.14% -0.17%, ti: less than or equal to 0.1 percent and the balance of Al.

3. The 7-series high-strength high-bending-resistance anti-collision beam for the automobile according to claim 1 or 2, characterized in that: a small amount of H element is added in the production of the beam metal, wherein the content of H is less than or equal to 0.20ml/100g.

4. A manufacturing method of a 7-series high-strength high-bending-resistance anti-collision cross beam for an automobile is characterized by comprising the following steps: