JPH0441646A - Aluminum alloy having good corrosion resistance and excellent in formability and baking hardenability - Google Patents

Abstract

PURPOSE:To obtain an Al alloy excellent in corrosion resistance, formability and baking hardenability by adding specified elements to Al. CONSTITUTION:An alloy having a compsn. contg., by weight, 0.6 to l.4% Si, 0.4 to 1.0% Mg, 0.04 to 0.50% Cu, 0.01 to <0.05% Mn and the balance Al with inevitable impurities is cast and is thereafter subjected to homogenizing treatment, hot rolling and cold rolling into a sheet having 1mm thickness. This sheet is furthermore subjected to soln. treatment of 540 deg.CX1min in a continuous annealing furnace, is successively subjected to forced air cooling and is aged at a room temp. for a month, by which the Al alloy which is the material having good corrosion resistance and formability as well as excellent in baking hardenability and useful as the apparatus material for transport including an automobile body sheet material can be manufactured.

Description

Detailed Description of the Invention [Industrial Application Fields] The present invention provides an aluminum alloy with good corrosion resistance, excellent formability and bake hardenability, which is particularly suitable for manufacturing transportation equipment such as automobile body sheet materials. It is related to.

[Prior Art] Conventionally, AA801B (A I -1,0~1°5
%S i -0,25~O,B%M g -0,20%
Below Cu-0, below 20% Mn) AA6111 (A
l -0,7~1.1% 5i-0,50~1.0
5M g -0,50~0.9%Cu -0,10~
0.45%Mn) is known, and A I -0.4~1.2%810.4~1.1%M with Fe as an essential component
g-0,1~0. B%Cu -0.05~0.35%F
e -0.2~0.8% Mn alloy (Special Publication No. 59-39
499) and Al-0 with improved spot welding properties.
, 3-1.526 S j O, 4-1.5% M
g-0.03% or less Cu-0.1% or less Mn (see US Pat. No. 4,460,418) has also been developed.

[Problems to be Solved by the Invention] However, the above-mentioned conventional materials are not necessarily satisfactory in terms of moldability, and when a zinc phosphate film is formed as an automobile panel, a uniform film cannot be obtained. There is.

[Means to solve the problem]

The present invention was made to solve the above problems, and
In weight%, Si: 0.6-1.4%, Mg: 0.4
~1.0%, Cu: 0.04%~0.50%, M
n: Contains 0.01 to less than 0.05%, the remainder is A
It is an aluminum alloy characterized by good corrosion resistance, excellent formability and bake hardenability, and is characterized by consisting of I and unavoidable impurities.

The reasons for limiting the above composition are as follows.

Si: Necessary to obtain high strength. If it is less than 0.6%, the desired strength cannot be obtained, and if it exceeds 1.4%, grain boundary precipitation will occur and ductility will decrease, and corrosion resistance will also deteriorate. .

Mg: Necessary together with Si to obtain high strength,
If it is less than 0.4%, the desired strength cannot be obtained;
If it exceeds 100%, grain boundary precipitation will increase, ductility will decrease, and corrosion resistance will also deteriorate.

Cu: Addition of a small amount promotes the cathode reaction and forms a uniform and fine zinc phosphate film.

If it is less than 0.03%, it will not have sufficient effect, and if it is less than 0.50%.
If it exceeds 100%, room temperature aging is likely to occur after solution treatment, resulting in poor moldability. In addition, corrosion resistance is poor and pitting corrosion occurs.

By adding a small amount of Mn, it is effective for uniform fine precipitation of Mg-8i-based compounds, effective for increasing strength during heating after forming, uniform fine crystal grains can be obtained, and high ductility can be obtained. . Furthermore, grain boundary segregation of Si is suppressed and high ductility is maintained. If it is less than 0.01%, there will be no effect, and if it is more than 0.05%, the yield strength after solution treatment will be high and the moldability will be poor.

Example C] After casting an alloy having the composition shown in Table 1, it was subjected to homogenization treatment, hot rolling, and cold rolling to form a plate having a thickness of 1. Further, the sample material was subjected to solution treatment at 540° C. x 111 nm in a continuous annealing furnace, followed by forced air cooling and aging at room temperature for 1 month.

Table 2 shows the evaluation results of these test materials. Corrosion resistance was determined by a 30-day salt spray test. SEM to see if the zinc phosphate film is evenly coated on the entire surface.
Judgment was made by

Since the test materials of Examples 1 to 3 had compositions within the scope of the claims of the present invention, good performance was obtained. Since the sample material of Comparative Example 1 had a large amount of Cu, pitting corrosion occurred in the salt spray test. Since the T4 material has a high yield strength and a low Erichsen value, its formability is poor. Since the sample material of Comparative Example 2 has a small amount of Cu, a uniform and fine zinc phosphate film cannot be obtained.

Since the sample material of Comparative Example 3 has a small amount of Mn, grain boundary segregation of Si occurs, resulting in a decrease in ductility. In Comparative Example 4, since the amount of Mn is large, the strength of the T4 material is too high and the moldability is poor.

Table 2 Table 1 Chemical composition (vt%) Note: Fe and Cr5Ti are impurities.

[Effects of the Invention] As explained above, the aluminum alloy of the present invention has good corrosion resistance and formability, and is a material with excellent bake hardenability, and is suitable for transportation equipment materials including automobile body sheet materials. It is useful as

Claims (1)

[Claims] In weight%, Si: 0.6-1.4%, Mg: 0.4-1
．． 0%, Cu: 0.04% to 0.50%, Mn: 0.0
An aluminum alloy with good corrosion resistance, excellent formability and bake hardenability, characterized by containing 1% to less than 0.05%, with the remainder consisting of Al and unavoidable impurities.