Summary of the invention
Namely object of the present invention is that providing a kind of had both had excellent forming property, met again the new automobile parts high-performance aluminium alloy of baking vanish thermal treatment sclerosis and surface aesthetic needs.
Aluminium alloy of the present invention has following composition: in weight hundred parts of ratios (wt.%), Mg4.0-4.5, Si0.6-0.8, Cu0.6-1.0, Mn0.05-0.1, Cr0.05-0.1, Zr0.05-0.1, Zn0.05-0.1, Sn0.1-0.2, Sr0.01-0.05.
Preferred further, Mg4.2, Si0.7, Cu0.8, Mn0.07, Cr0.06, Zr0.06, Zn0.08, Sn0.15, Sr0.03;
Preferred further, Mg+Cu+Si≤6.0.
Aluminium alloy of the present invention is prepared by following method:
First according to the stoichiometric preparation raw material of aluminium alloy, the method by semicontinuous casting after raw materials melt is obtained aluminum alloy slab;
Aluminum alloy slab is implemented to homogenize process under the condition of 520-550 DEG C, treatment time 3-4h;
Implement hot roughing to aluminium alloy subsequently, it is 520-550 DEG C that roughing starts temperature, and finishing temperature is 450-480 DEG C, and draft is more than 90%;
Implement hot finishing to aluminium alloy subsequently, the temperature of hot finishing is 400-430 DEG C, and draft is 70-80%, strain rate 15-20/s;
Through cold rolling, aluminium alloy is pressed into required thickness subsequently;
Subsequently aluminium alloy is heated to 480-530 DEG C and implements solution treatment 30-60s, after being cooled to 280-320 DEG C with the speed of cooling of 20-30 DEG C/s, be chilled to room temperature with the speed of 150-200 DEG C/s, natural aging 24-30h;
Again aluminium alloy is heated to 50-70 DEG C of insulation 30-36h subsequently, obtains the present invention and both there is excellent forming property, meet again the new automobile parts high-performance aluminium alloy of baking vanish thermal treatment sclerosis and surface aesthetic needs.
Namely advantage of the present invention is, redesign the aluminium alloy stock proportioning being main alloy element with silicon, magnesium, copper, by cooperatively interacting of each material composition, and corresponding rolling, thermal treatment process, obtain and both there is excellent forming property, meet again the new automobile parts high-performance aluminium alloy of baking vanish thermal treatment sclerosis needs.
Embodiment
Content of the present invention is described in detail below by specific embodiment.
According to the al alloy component proportioning described in table 1, preparation starting material, obtain aluminum alloy slab by the method by semicontinuous casting after raw materials melt; Aluminum alloy slab is implemented to homogenize process under the condition of 520 DEG C, treatment time 3h; Implement hot roughing to aluminium alloy subsequently, it is 520 DEG C that roughing starts temperature, and finishing temperature is 450 DEG C, and draft is 90%; Implement hot finishing to aluminium alloy subsequently, the temperature of hot finishing is 400 DEG C, and draft is 70%, strain rate 15/s; Through cold rolling, aluminium alloy is pressed into required thickness subsequently; Subsequently aluminium alloy is heated to 480 DEG C and implements solution treatment 30s, after being cooled to 280 DEG C with the speed of cooling of 20 DEG C/s, be chilled to room temperature with the speed of 150 DEG C/s, natural aging 24; Again aluminium alloy is heated to 50 DEG C of insulation 30h subsequently, obtains aluminium alloy of the present invention.
Table 1
|
1 |
2 |
3 |
1# |
2# |
3# |
4# |
5# |
6# |
Mg |
4.0 |
4.2 |
4.5 |
3.0 |
5.5 |
4.5 |
4.2 |
4.1 |
4.2 |
Si |
0.8 |
0.7 |
0.6 |
0.4 |
0.6 |
0.8 |
0.7 |
0.8 |
0.7 |
Cu |
1.0 |
0.8 |
0.6 |
0.5 |
0.8 |
1.0 |
0.8 |
0.9 |
0.7 |
Mn |
0.05 |
0.07 |
0.08 |
0.06 |
0.05 |
0.1 |
0.04 |
0.2 |
0.07 |
Cr |
0.1 |
0.06 |
0.07 |
0.08 |
0.09 |
0.1 |
0.02 |
0.1 |
0.08 |
Zr |
0.05 |
0.07 |
0.09 |
0.07 |
0.08 |
0.08 |
- |
0.1 |
0.07 |
Zn |
0.05 |
0.08 |
0.1 |
0.07 |
0.08 |
0.06 |
0.02 |
0.15 |
0.05 |
Sn |
0.1 |
0.15 |
0.2 |
0.15 |
0.1 |
0.15 |
0.2 |
0.2 |
- |
Sr |
0.01 |
0.03 |
0.05 |
0.04 |
0.02 |
0.05 |
0.03 |
0.04 |
- |
TS |
282 |
294 |
275 |
211 |
298 |
312 |
256 |
308 |
284 |
YS-1 |
115 |
120 |
110 |
102 |
154 |
165 |
104 |
157 |
117 |
YS-2 |
183 |
192 |
178 |
143 |
185 |
201 |
155 |
190 |
152 |
LDR |
2.21 |
2.28 |
2.28 |
1.95 |
1.86 |
1.88 |
2.07 |
1.94 |
2.13 |
SS |
○ |
○ |
○ |
○ |
× |
○ |
○ |
○ |
× |
In table 1, TS is tensile strength, units MPa; YS-1 is the yield strength without paint baking, units MPa; YS-2 is through 170 DEG C, yield strength after 30min paint baking, units MPa; LDR is limit stretching ratio; SS is the surface quality evaluation after being shaped, and zero is without obvious stretcher strain markings, × for there being obvious stretcher strain markings.
As can be seen from the result of table 1, Mg is as main alloying element, for the intensity of aluminum-system and plasticity, there is material impact, the content of Mg alloying element is too low, be then difficult to realize grain refining, and the effect of strengthening phase strengthening, thus the requirement of system for intensity and plasticity cannot be met, if but the too high levels of Mg, then easily there is intercrystalline failure and cause brittle rupture when being shaped, inventing obvious plasticity and worsening.Mg too high levels also has adverse influence for the surface quality of the rear aluminium alloy that is shaped simultaneously.In the present invention, the content of preferred Mg is 4.0-4.5, more preferably 4.2.
Si alloying element is significant for formation intermetallic compound strengthening phase, and in order to form enough strengthening phases to meet the needs of intensity, the content of Si can not be too low, at least should reach 0.6.But the precipitation that too much Si addition may cause strengthening phase excessive, thus make forming process easily brittle rupture occur and affect processability, therefore should control its content and be less than 0.8.Preferably, the Si in the present invention is 0.7.
Mg with Si is not the same has determinative mutually for precipitation strength for Cu alloying element, in order to obtain excellent intensity and processability, the content of Cu should ensure more than 0.6, but too much Cu content not only can cause the excessive of precipitated phase thus make plasticity be deteriorated, also can the intergranular corrosion resistance performance of severe exacerbation system, therefore should control its content and be less than 1.0.Preferably, the Cu in the present invention is 0.8.
Meanwhile, the consideration that tensile strength improves saturability and avoids yield strength too high, preferred Mg+Cu+Si≤6.0 is considered.
Mn, Cr, Zr, Zn are as the alloying element of trace, it mainly serves grain refining, appropriate interpolation has beneficial effect for the intensity of system and forming property, for ensureing to play its effectiveness, the addition of each composition at least reaches Mn0.05, Cr0.05, Zr0.05, Zn0.05, but its interpolation should be inexcessive yet, otherwise coarse grain can be generated on the contrary and severe exacerbation plasticity, and reduce the corrosion resistance nature of system, specifically should control its content and be no more than Mn0.1, Cr0.1, Zr0.1, Zn0.1.And the complex intensifying of Mn, Cr, Zr is comparatively effective, and preferably its content is Mn0.07, Cr0.06, Zr0.06.
Sn alloying element can play the effect improving surface quality in system, and for playing its effect, the addition of Sn at least should reach 0.1.But too much Sn addition may cause the corrosion resistance nature of other degradation, particularly aluminium alloy of system, therefore preferred below 0.2, more preferably 0.15.
The Main Function of Sr alloying element is to play inhibiting grain growth, the generation of the coarse grains particularly in solution treatment process, for playing above-mentioned effect, the addition of Sr at least should be 0.01, but too much interpolation can make the mechanical property of system worsen, therefore should control its addition and be less than 0.05, more preferably 0.03.
For investigating the impact of subsequent heat treatment technique for aluminium alloy capability further, the chemical composition that have employed embodiment 2(comparative example not embodiment 2 is identical) chemical composition and processing parameter as according to object, change heat treatment parameter and test results of property, specifically see table 2.
Table 2
In order to obtain sufficient homogenizing effect, all heat treated temperature should be at least 520 DEG C, but also should be not too high, to avoid the local melting of alloy.Meanwhile, in order to avoid the coarsening of the alloying element precipitates such as Mn, Cr, should avoid the heat treated of process time or repeatedly heat, controlling soaking temperature in the present invention is 520-550 DEG C, and the treatment time is 3-4h.
The beginning temperature preferred heterogeneity treatment temp of hot roughing is consistent, if the temperature of hot roughing is lower than 520 DEG C, can not recrystallize fully in the process of rolling, the tendency of coarsening in a organized way, and the beginning temperature of roughing is too high, then easily cause the series of problems such as local melting, surface oxidation, thus affect surface quality and plasticity.
The preferred 450-480 DEG C of finishing temperature of hot roughing, finishing temperature is too low, and after making hot finishing, recrystallize is insufficient, and finishing temperature is too high, and the crystal grain of hot finishing subsequently can be made to have coarsening to be inclined to.
The processing temperature of hot finishing is preferably 400-430 DEG C, the temperature of hot finishing is too low, and after making finish rolling, recrystallize can not fully carry out, the ductility of alloy and processing characteristics deficiency, and the temperature of hot finishing is too high, be then difficult to effectively control the even with the performance of guarantee system of grain fineness number.Meanwhile, too low strain rate, also can cause the uneven of grain fineness number, should controlled strain speed at 15-20/s.
Solid solution temperature should ensure at 480 DEG C, because too low temperature can not make the precipitation strength elements such as Mg, Cu, Si obtain sufficient solid solution, thus be difficult to obtain enough plasticities and bake hardening, but also more than 530 DEG C, otherwise local melting, surface oxidation equivalent risk should do not had.And in order to obtain enough solid solution effects, solution time should at least at more than 30s, but also should not be long to affect the efficiency of producing.
The slow cooling of one-step cooling is mainly that the precipitation of now strengthening phase is not remarkable, therefore slow cooling can't cause the obvious rising of yield strength, thus the forming property of system can not be worsened, its cooling rate of preferred control is at 20-30 DEG C/s, further reduction speed of cooling is then likely in crystal boundary generation precipitation-hardening, thus the plasticity affected subsequently and bake hardening.
The chilling of two-step cooling can suppress the generation of precipitation-hardening effectively, thus effectively can suppress the increase of yield strength, reaches the object improving forming property.To achieve these goals, speed of cooling at least should reach 150 DEG C/s, but should be not too high, otherwise has the risk that quenching strain occurs.
Again aluminium alloy is heated to 50-70 DEG C of insulation, the abundant diffusion of solute atoms can be impelled, to form low-temperature reinforcement phase, thus reach the object improved plasticity, improve intensity.But too high aging temp then may cause the precipitation of high-temperature-phase, thus worsen the plasticity of system.