JPS61153265A - Production of high strength al-mg alloy - Google Patents

Abstract

PURPOSE:To produce a high strength Al-Mg alloy having superior hot workability and peeling and corrosion resistances by soaking an Al-Mg alloy ingot having a specified composition consisting of Mg, Mn, Zr, Ti and Al under proper conditions. CONSTITUTION:An Al-Mg alloy ingot consisting of, by weight, 2-4% Mg, 0.3-1.0% Mn, 0.05-0.2% Zr and 0.01-0.1% Ti as essential components and the balance essential Al is soaked at 505-550 deg.C for 4-24hr and hot worked to obtain a high strength Al-Mg alloy. When hot rolling is carried out as the hot working, the ingot is preferably soaked for 4-16hr. When hot extrusion is carried out, the Zr content is preferably regulated to 0.07-0.2%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a high-strength AI-Mg alloy that has excellent performance as a material for chemical plants, railway vehicles, automobile wheels, etc.

[Prior Art] A1-Mg alloys have appropriate mechanical strength and are also excellent in corrosion resistance, weldability, moldability, etc., and are therefore rated as JIS Standards 5052 and 5083.

5454, 5154, etc. are widely used for the above-mentioned purposes.

[Problems to be solved by the invention] A. As a general characteristic common to 1-Mg alloys, Mg
It has been confirmed that the higher the content, the higher the strength, but the lower the extrudability and exfoliation corrosion. That is, A
l-Mg alloys are made to have high strength by utilizing the hardening phenomenon caused by solid solution of Mg, and as the amount of Mg increases, the amount of solid solution of Mg increases and the strength improves, but the deformation resistance increases. As a result, hot workability in extrusion, forging, rolling, etc. decreases. Moreover, the β phase, which is a precipitate of Mg, decreases. For this reason, when applied to applications that require particularly high strength, Al with a high Mg content, such as the 5083 series, is recommended.
-Mg alloys are selected and used, while when a high level of hot workability and exfoliation corrosion resistance is required even at the expense of strength, A I -Mg alloys with a small amount of Mg such as the 5052 series are selected and used. ing. Furthermore, A I -Mg alloys are used as soft materials or work-hardening tempered materials, but the above-mentioned tendency to decrease exfoliation corrosion due to an increase in the amount of Mg appears more markedly in work-hardening tempered materials. Therefore, there is a strong desire to develop an AI-Mg alloy that exhibits excellent exfoliation corrosion resistance even after work hardening and tempering and satisfies requirements in terms of strength. In particular, when used at high temperatures of 66°C or higher, a higher level of exfoliation corrosion resistance is required than when used at room temperature, so the amount of Mg cannot be increased casually, and after all, high strength is required. In applications requiring high Mg content, even at the expense of exfoliation corrosion resistance, in applications where high exfoliation corrosion resistance is important, a low Mg content must be used, even at the cost of strength. Therefore, even under these circumstances, A that can satisfy both strength and peeling corrosion resistance.
The development of l -Mg-based alloys is awaited. Under these circumstances, the present invention has developed an Al-Mg material that can simultaneously satisfy the required properties of strength, exfoliation corrosion resistance, and hot workability such as extrusion.
The aim is to provide alloys.

[Means for Solving the Problems] The method for producing a high-strength AI-Mg alloy according to the present invention includes Mg: 2 to 4%, Mn: 0.3 to 1.0%, Z
r: 0.05-0.2% and Ti: 0.0
Contains 1 to 0.1% as an essential component, with the remainder being substantially A.
The gist is that an Al-Mg alloy ingot consisting of L is heated at 505 to 550°C for 4 to 24 hours, and then hot worked.

[Function] As mentioned above, when trying to obtain high strength in conventional Al-Mg alloys, hot workability and exfoliation corrosion resistance decrease, and when trying to increase hot workability and exfoliation corrosion resistance, strength decreases. However, with the present invention, as mentioned above, A
By specifying the composition of the l-Mg-based alloy and strictly regulating the heat treatment conditions, we have developed an AI-based alloy that has excellent properties in all aspects of strength, hot workability, and exfoliation corrosion resistance.
A Mg-based alloy can be provided.

The reasons for setting each essential component in the present invention will be clarified below. First, the reason why the alloy components and their content ranges were determined is as follows.

Mg: 2 to 4% Mg is an indispensable element for ensuring the strength required for Al-Mg alloys, and if it is less than 2%, sufficient strength cannot be obtained. However, if the Mg content exceeds 4%, no matter how appropriately the types and contents of other alloying elements or heat treatment conditions described below are set, both hot workability such as extrusion and exfoliation corrosion resistance will be satisfied. You won't be able to do that.

Mn: 0.3 A71.0% An essential element to increase strength and exfoliation corrosion resistance, 0
．． If it is less than 3%, the effect will not be effectively exhibited. However, if there is too much, hot workability will decrease.
/ A 1 − M n 3iE, + * t
r4bWnM On the other hand, since the shim removal ductility and toughness of the metal material decreases, it must be kept at 1% or less.

Zr: 0.05-0.2% It has the effect of increasing strength without having too much of a negative effect on hot workability (especially extrudability), and is an important element for compensating for the lack of strength due to insufficient Mg content. Does not deteriorate peeling corrosion properties. In order to effectively demonstrate these effects, 0.
It must be contained in an amount of 0.05% or more, and particularly when applied to hot extrusion processing, it is desired to be contained in an amount of 0.07% or more. However, if it is too large, large intermetallic compounds of the Al-2 type will crystallize, resulting in decreased ductility and toughness as well as deterioration in extrusion processability, so it must be kept at 0.2% or less.

Ti: 0.01-0.1% Has the effect of refining the ingot structure and preventing casting cracks,
．． If it is less than 0.01%, the effect of refining the ingot structure is insufficient and feather-like crystals with rich directionality are generated, which not only tends to cause variations in the material properties of the processed material but also tends to cause casting cracks. However, if it exceeds 0.1%, a large amount of TiAl3 crystallized compounds will be produced, resulting in deterioration of ductility and toughness.

The A1-Mg alloy used in the present invention contains each of the above elements as essential components, and the remainder consists essentially of At. However, if necessary, the performance can be improved by further containing the following elements. It is also effective to increase it further.

Cr, V: 0.2% or less each Cr and V have the effect of increasing strength and exfoliation corrosion resistance, but their effects are smaller than those of Mn and Zr.

However, in addition to Mn and Zr, further small amounts (preferably 0 of each) are added.
．． 05% or more), the effect becomes apparent. However, if the amount is too high, hot workability will decrease, and Al-Cr and A
Since large l-V type intermetallic compounds crystallize and reduce ductility and toughness, the content must be suppressed to 0.2% or less.

B: 0.05% or less B has the effect of further refining the ingot structure when used in combination with Ti, and its effect is effectively exhibited by containing it in an amount of 0.0005% or more.

However, if it exceeds 0.05%, crystallized compounds such as T i B2 are produced, which not only reduces the effect of Ti but also adversely affects ductility and toughness due to the production of the crystallized compounds.

In the present invention, an ingot is manufactured by a conventional method using a molten A I-Mg alloy having the above-mentioned composition, and then subjected to soaking treatment and then hot working. A soaking treatment condition of 505-550°C for 4-24 hours should be adopted.

However, if the soaking temperature is lower than 505°C, precipitates containing Zr and Mn (ZrA13 and MnAlr
+, etc., which may further contain Cr or V precipitates depending on the case) is a size suitable for significantly inhibiting recrystallization of the structure, and the metal structure becomes a fibrous structure. For this reason, although the strength is improved, the hot workability is deteriorated, and furthermore, the exfoliation corrosion resistance is also deteriorated. On the other hand, the soaking temperature is 550°
When C is exceeded, the effect of inhibiting recrystallized structure by precipitates such as Mn and Zr is hardly exhibited, so recrystallization of the structure progresses well and although exfoliation corrosion resistance improves, strength deteriorates. However, if the soaking temperature is set in the range of 505 to 550°C, the effect of inhibiting recrystallization by precipitates such as Mn and Zr will be adequately exerted, and the alloy will have an appropriate ratio of fiber structure and recrystallization structure. Therefore, it has excellent strength, hot workability, and exfoliation corrosion resistance.

Further, the soaking treatment time is appropriately selected depending on the soaking temperature, but if it is less than 4 hours, the same problem as in the case where the soaking temperature is insufficient will occur. In soaking treatment within the above-mentioned preferred temperature range, the soaking effect is saturated after 24 hours, and if soaking is continued beyond that time, secondary recrystallization will proceed, resulting in poor strength and stress corrosion cracking resistance.

When applied to applications where exfoliation corrosion resistance is particularly strongly required, it is desirable to limit the scorching heat treatment to within 16 hours.

After soaking in this manner, the material is then subjected to hot working such as hot extrusion using a conventional method to maintain excellent hot workability and improve strength and exfoliation corrosion resistance. An excellent Al-Mg alloy can be obtained.

[Example] Example 1 A slab with a thickness of 50 mm was formed using a molten Al-Mg alloy having the chemical composition shown in Table 1, and after soaking under the conditions shown in Table 2, the slab was made into a slab with a thickness of 6+++ m. Hot rolled to

Thereafter, softening annealing was performed at 350° C. for 2 hours to obtain a soft material. Next, soft material No. 2.9.11 was selected as a representative example, and after cold rolling at a processing rate of 15 to 50%, stabilization treatment was performed at 130 to 170°C for 3 hours to obtain H3.
We manufactured a type of work-hardened tempered material.

The material properties of the soft material are shown in Table 2, and the material properties of the work-hardened and tempered material are shown in Table 3.The alloys produced under conditions that meet the specified requirements of the present invention are compared to the comparative alloys. It can be seen that it is superior in both strength and exfoliation corrosion resistance.

Table 3 *Tested according to QQAOO250/19 standard after heat treatment at 120℃ x 7.

Evaluation: 0 A>B>C (J Example 2 A billet of 190 mmφ was formed using the molten A I-Mg alloy with the chemical composition shown in Table 4, and soaked under the conditions shown in Table 5. After that, the deformation resistance of the ingot was measured.Then, the ingot was extruded into the shape shown in Figure 1 to examine its extrudability, as well as its mechanical properties after extrusion, and its exfoliation corrosion resistance. The deformation resistance was determined by the drop hammer test method and the change in the height of the test piece before and after the drop hammer.The extrudability was evaluated by the final use of the press during extrusion.

The results are shown in Table 5, and it can be seen that the alloys that meet the specified requirements of the present invention have better extrudability and superior strength and exfoliation corrosion resistance than conventional alloys.

Example 3 Invention alloy No. 12.13 shown in Table 4 and No.
Comparative alloy No. 20.21 was selected, and an extrusion test (extrusion temperature: 500° C.) was performed on a large thin-walled material shown in FIG. 2 to determine the minimum extrudable wall thickness (t: m+s).

The results are shown in Table 6. Although the alloy of the present invention has high strength, it also has excellent extrudability and can be extruded into thin walls.

Table 6 [Effects of the Invention] The present invention is constructed as described above, by strictly setting the chemical components and soaking treatment conditions.

It is possible to provide an Al-Mg alloy that not only has excellent strength and hot workability (particularly extrudability), but also has excellent exfoliation corrosion resistance regardless of whether it is a soft material or a work-hardened tempered material. Became.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams showing the cross-sectional shape of the extruded material employed in the experimental example.

Claims (3)

[Claims] (1) Mg: 2-4% (weight%: same below), Mn: 0
．． 3-1.0%, Zr: 0.05-0.2%, Ti: 0
．． 01 to 0.1% as an essential component, and the remainder is substantially Al.
A method for producing a high-strength Al-Mg alloy, which comprises heating at ℃ for 4 to 24 hours and then hot working. (2) Heating the ingot at 505-550°C for 4-16 hours,
The manufacturing method according to claim 1, wherein hot rolling is then performed. (3) Al-Mg with Zr content of 0.07-0.2%
The manufacturing method according to claim 1, wherein hot extrusion is performed after heating the alloy ingot.