JPS63114949A - Manufacturing method of high-strength aluminum alloy material with excellent weldability - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention ``Object of the Invention'' Industrial Field of Application The present invention is directed to an MIG, T
This invention relates to a method of manufacturing a high-strength aluminum alloy material with good weldability for use in IG, spot resistance welding, etc.

Conventional technology In order to weld large structures using aluminum or its alloy, A5083 (Al-Mg alloy), 7
It is necessary to use a material such as N01 (Al-Zn-Mg alloy).

In other words, the welding methods include MIG, TIG, spot resistance welding, which forms a sufficient molten pool in the weld, flash pad welding, which applies high energy to the weld to minimize the weld, and electron beam welding. Although many welding methods such as welding are known, it is necessary to use the above-mentioned alloys in order to obtain large structures by welding in which a sufficient molten pool is formed.

In other words, welding methods with as small a molten pool as possible require the molten pool to be rapidly cooled and have little thermal effect on the base metal, which may cause the weld pool to solidify if the material is easily cracked or the base metal. This is an excellent method when the material is easily damaged by heat.

However, since the flash pad welding method applies high voltage to the entire surface of the welding area to perform instantaneous welding, it requires high precision in processing the groove and it is necessary to generate high energy over the entire surface of the welded area. Due to its nature, when welding structures with large welds using this method, it is difficult to process the groove with high precision, or there are limits to the size of high voltage application equipment, etc. However, structures with large welded areas cannot be welded. This is almost the same in the electron beam welding method mentioned above.Since the welding process is performed by irradiating the welded area with an electron beam, it is necessary to make the welding area narrow and uniform. When welding a large structure using this method, it is difficult to perform such high-precision machining of the groove, and as described above, a structure with a large welded portion cannot be welded. On the other hand, the welding method that forms a sufficient molten pool at the welded part requires the welding process to minimize the amount of molten pool as much as possible.
Alternatively, it is possible to set welding conditions such as heat input over a relatively wide range, and the equipment cost is low, so it is widely applied to welding various structures, not only small structures but also large structures. However, for that purpose, the above A3083.
It is said that an alloy such as 7NO1 should be used.

Problems to be Solved by the Invention In general, the Aj? -Zn-M
G-Cu alloys have the highest strength among aluminum alloys, and are important as structural materials that require high strength, including aircraft. However, this Aff-Zn-Mg-C
When U-based alloy materials are welded by the above-mentioned welding method in which a molten pool is sufficiently formed in the welded part, the molten pool solidifies and the weld metal is formed between the base metals, as shown in Figure 1. It is well known that cracks 2 are likely to occur in the portion 1 and minute cracks (hereinafter referred to as micro-cracks) 12 are likely to occur in the hot welding tongue portion 11 of the base material 10. For this reason, it is not possible to assemble this type of alloy base material into a structure by welding it by the above-mentioned MIG, TIG, spot resistance welding method, etc., which sufficiently forms a molten pool, and especially in the case of large structures. Since welding with a small molten pool cannot be used as described above, it is required to assemble and join using a method that requires a large number of processing steps and has low productivity, exclusively using rivets.

"Structure of the invention" Means for solving the problem Zn: 5.0 to 7.0 wt%, Mg: 1. 0～
3.0wt%, Cu: 0.5-1.8wt%, Z
r: 0.05-0.20wt%, V: 0.03
~0.20wt%, Ti: 0.02~0.15w
t%, and the total content of Zr, ■ and Ti is in the range of 0.10 to 0.40wt%, and the balance is A1.
The ingot consisting of impurities is held at a temperature of 400 to 460 ° C for 8 to 24 hours to perform the first stage homogenization treatment,
A high-strength aluminum with excellent weldability, characterized in that it is then held at a temperature of 480 to 520°C for 8 to 24 hours to perform a second stage homogenization treatment, and then subjected to a stretching treatment by a conventional method. Manufacturing method for alloy materials.

The content of Zn, Mg, and Cu is -t% (hereinafter simply referred to as %).
), Zn: 5.0 to 7.0%, Mg: 1
．． 0 to 3.0°% and Cu: o, s to 1.8% to provide strength as an A 1-Zn-Mg-Cu-based aluminum high-strength alloy as described above.

In addition, the content of Zr % V, Ti, Zr: 0005 ~ 0
．． 20%, V: 0.03-0.20%, Ti: 0.02
~0.15% and these Z r ,, V %
By setting the total amount of T i to 0.10 to 0.40%, welding can be performed with sufficient formation of a molten pool.
Prevents cracks that occur in welded metal parts when welding using welding methods such as G, TIG, and spot resistance.

An ingot having the composition as described above is heated at a temperature of 400 to 460°C.
~ Aj in the first stage soaking treatment held for 24 hours! -C
While redissolving low melting point compounds such as u-Mg, Z
r and V are precipitated finely and uniformly.

A second stage soaking treatment at 480 to 520° C. for 8 to 24 hours re-dissolves high melting point compounds such as Aj2-Cu-Fe and Zn, Mg, and Cu that were segregated during casting and uniformly distributes them.

As a result of the soaking treatment in steps 1 and 2, microcracking during welding is prevented and stretching is facilitated.

EXAMPLES To further explain the present invention as described above, the inventors of the present invention have conducted extensive studies in view of the problems of the prior art, and have developed an MIG method for welding aluminum alloy materials by sufficiently forming a molten pool. AA that does not generate cracks or microcracks when welding by TIG, spot resistance welding, etc.
We succeeded in obtaining a method for producing a '-Zn-Mg-Cu alloy material.

First, the reason for limiting the range of addition of various alloying elements to Al in the present invention as described above will be described below.

Zn: 5.0 to 7.0% Zn is used to impart strength to alloy materials, and if its content is below the lower limit, its effect will not be sufficient, and if it exceeds the upper limit, stress corrosion cracking will occur. This range is chosen because it tends to occur and the susceptibility to weld cracking increases.

Mg: 1.0 to 3.0% Mg is also used to impart strength to the alloy material, and its effect is not sufficient if its content, along with Zn, is below its lower limit. Moreover, if it exceeds the upper limit, stress corrosion cracking is likely to occur, and the susceptibility of the base material to micro-cracks will also increase, so this range is set.

Cu: Q, 5-1.8% Cu is 5.0% or more of Zn and Mg: 1 as mentioned above
．． In combination with 0% or more, the 7NOI C mentioned above for alloy materials
It is important for achieving higher strength than AII Zn Mg-based alloys, and also provides stress corrosion cracking resistance. If the content is less than 0.5%, these effects cannot be sufficiently obtained, and if the content exceeds the upper limit, the susceptibility to weld cracking and microcracking increases, as is the case with Zn and Mg. Similarly, it is necessary to set the upper limit to 1.8%.

In the present invention, the above Zn, Mg and Cu
AI! -Zn In addition to making the Mg-Cu based high-strength aluminum alloy, we also added Zr to accurately prevent cracks that occur in the deposited metal even when welding is performed using a welding method that sufficiently forms a molten pool.
: 0.05~0.20%, V: 0.03~0.2
0%, Ti: 0.02~0.15%, Zr
, V%Tr coexist. That is, it makes the crystal grains of the weld metal part finer and prevents weld cracking, Zr and V improve stress corrosion cracking resistance, and Ti makes the ingot crystal grains finer and prevents solidification cracking during casting. do. Zr
, ■, and Ti are both contained in amounts above the lower limit, so that their effects are appropriately balanced and achieved together.
Moreover, if any one of them exceeds the upper limit, coarse particles of the intermetallic compound are likely to be generated, resulting in a decrease in toughness and fatigue strength.

Furthermore, it is numerically clear that if the total amount of Zr, V, and Ti is less than 0.10%, any of the above-mentioned coexistence effects will be insufficient, and moreover, if it is more than 0.40%, Even if each does not exceed the above-mentioned upper limit, there is still a tendency for coarse particles of the intermetallic compound to occur easily, resulting in a decrease in toughness and fatigue strength.

In addition to the above-mentioned elements, the present invention also contains, if necessary, B: 0.01% or less, Mn: 0.40% or less, Cr:
0.25% or less, Mo: 0.15% or less, Fe: 0.
It has been confirmed that the effects of the present invention are not hindered even if one or more of Si: 0.25% or less is contained. It can be contained in It is recognized that if they are added in excess of the upper limit, it will not be possible to effectively obtain the respective properties such as strength, toughness, and prevention of cracking in a welding method that sufficiently forms a molten pool. It can be done.

The product according to the present invention has Zn as described above in terms of composition.
, , Mg , Z r % V % T i together with Cu
It is not only necessary to select an appropriate range for each of the above, but also a homogenization process consisting of a specific first and second stage is required, and the relationship between them is as follows. . That is, first, an ingot having the composition as described above is heated to 400~
The first stage homogenization treatment is carried out by holding at a temperature of 460° C. for 8 to 24 hours. This treatment re-dissolves low melting point compounds such as A4-Cu-Mg system produced when casting the ingot, and also precipitates Zr and V finely and uniformly to prevent weld cracks and micro-cracks during welding. The effect is not sufficient at temperatures below 400°C for 8 hours, and
When the temperature exceeds ℃, local melting of the above-mentioned low melting point compound occurs,
It deteriorates the elongation workability in the post-process, and reduces the toughness and fatigue strength. However, even if it is held for more than 24 hours, the effect will be saturated and energy will be lost. Further 400-460℃
By setting the heating rate to a temperature of 100° C./hour or less, it is possible to uniformly and finely precipitate additional elements such as Zr and (2). In this case, the temperature increase curve may be performed stepwise.

The ingot subjected to the first-stage homogenization treatment as described above is subjected to a second-stage homogenization treatment at a temperature of 480 to 520° C. for 8 to 24 hours. This treatment uses high melting point compounds such as Aβ-Cu-Fe and Zn-, MgS, which segregated during casting.
This is to re-dissolve Cu into a solid solution to facilitate the subsequent stretching process, and the effect is not sufficient if the temperature is below 480°C for 8 hours, and if it is above 520°C, partial melting and Zr % V will occur. These precipitates become coarse and deteriorate drawing workability, toughness and fatigue strength. But 24
Even if it is held for more than a certain period of time, the effect will be saturated and it will simply be an energy loss.

Note that the homogenization treatment in the first and second stages as described above can be carried out continuously or discontinuously. That is, even if the temperature is raised to the temperature of the first homogenization treatment after the temperature conditions and time of the first homogenization heat treatment are satisfied and the process is continued, the solid solution has already been redissolved by the first homogenization treatment. It does not cause local melting of low melting point compounds (,
The process directly proceeds to the second stage homogenization treatment, where high melting point compounds and the like are solid-dissolved again. Of course, even if the first stage homogenization treatment is performed, the second stage homogenization treatment is performed by cooling to room temperature or other suitable temperature and then reheating, there is almost no difference in the operation and effect. Only some thermal energy loss due to heating is observed.

The ingot that has been subjected to the first and second homogenization treatments as described above is then subjected to a drawing process such as hot or cold extrusion, rolling, forging, etc., to form a desired shape. The hot working in this case is preferably carried out at a temperature range of 380 to 480°C.

In other words, at temperatures below 380°C, processing is difficult even with careful heating, so it is necessary to increase the number of processing cycles, which reduces productivity or is disadvantageous in terms of equipment, and above 480°C This is because hot cracking is likely to occur. Further, when the hot working ratio is set to 50% or more, the hot working structure is sufficiently developed, which is effective in preventing microcracks during welding. After hot working, cold working is performed as necessary.

Thereafter, solution treatment and aging treatment are performed using conventional methods.

Next, a specific manufacturing example of the product according to the present invention will be described as follows.

Production Example 1 An ingot having a cross-sectional shape of 70n×200+n having the composition shown in Table 1 was cast by a semi-continuous casting method.

That is, alloys 1 to 8 are all according to the present invention, and 1
~5 is Zn SMg-, Cu is constant, Zr5V ST
6 to 8 are Zr, V, T
i is constant and Zn-, Mg%Cu is varied. Compared to the comparative materials of the present invention, Alloy A has Zr below the present invention range, Alloy B has Zr above the present invention range, and Alloy C has Zr, V% Ti, and V% Ti. Within the scope of the present invention, but their total amount is 0.4%
The above is beyond the scope of the present invention. Further, the Ti of the v1 alloy does not reach the range of the present invention, the Ti of the alloy E exceeds the upper limit of the present invention, and the Ti of the alloy G exceeds the upper limit of the present invention. However, alloy H is Zn
, alloy J has Mg and alloy alloy Cu does not reach the range of the present invention, while alloy ■ has Mg in Zns alloy and alloy M has C.
Each of u is beyond the scope of the present invention, and all other components satisfy the conditions of the present invention.

Table 1 Each ingot obtained as described above was heated at a heating rate of 80°C/HrO and held at a temperature of 440°C for 12 hours.
A step homogenization treatment was performed, and the ingot was further held at a temperature of 480° C. for 12 hours to perform a second step homogenization treatment. Next, this ingot was hot rolled to a thickness of 12n+ at a temperature of 440°C, then solution treated by holding at a temperature of 470°C for 30 minutes, and after water quenching, it was held at a temperature of 120°C for 24 hours. A test material was subjected to artificial aging (T6 treatment).

These test materials were welded under the welding conditions shown in Table 2 below.

Table 2 MIC welding conditions filler metal; A5183WY-1,6 dragon diameter (/j!-0.8%Mn-4.8%Mg-0,15%C
r) Table 3 shows the results of evaluation of mechanical properties, stress corrosion cracking life, presence or absence of coarse particles, and weldability of the test materials in the T6 state. Note that the evaluation was performed based on the following evaluation criteria.

Evaluation Criteria (1) A high-strength alloy was required to have a tensile strength in the T6 state of 50 kg/w'' or more.

(The stress corrosion cracking life in the 2176 state is calculated by applying a bending stress of 75% of the 0.2% proof stress in the direction perpendicular to the rolling direction, and CH
3% NaCl-0 adjusted to pl'14 with 3COOH,
The sample was immersed in a 5% KzCrzCh aqueous solution, and the number of days until cracking occurred was determined.

(3) Particles of intermetallic compounds having a diameter of 20 μm or more were considered coarse particles, and the presence or absence of coarse particles was determined by observing with an optical microscope.

(4) Weldability was evaluated by visually observing the presence or absence of cracks occurring in the solidified portion of the molten pool, and by observing with an optical microscope the presence or absence of microcracks occurring in the weld heat affected zone.

From the results in Table 3, it can be seen that all of the examples according to the present invention satisfy the necessary conditions, whereas those according to the comparative examples outside the composition range of the present invention do not satisfy any of the evaluation criteria, and the welding It can be seen that this is not preferable as a high-strength structural member.

Production Example 2 Ingots having the compositions of alloy numbers 1 and 6 shown in Table 1 in Production Example 1 described above were cast in the same manner as Production Example 1,
The ingot was heated at a temperature increase rate of 80° C./hour and subjected to homogenization treatment under the conditions shown in Table 4 below.

In Table 4, e and `` are cases where the second stage homogenization treatment is not performed, particularly f is the case where the temperature of the first stage homogenization is high, and g is the temperature of the first stage homogenization. is low, h is the case where the time for the second stage homogenization is insufficient, and i is the case where the temperature of the second stage homogenization is high.

For the homogenized ingots as shown in Table 4 above, the ingots were subsequently hot rolled to a thickness of 121 at a temperature of 420°C, and then solution treated by holding at a temperature of 470°C for 40 minutes. After water quenching, the material was maintained at a temperature of 120° C. for 24 hours to undergo artificial aging (T6 treatment) to obtain a test material.

These test materials were welded under the same conditions as shown in Table 2 above.

Table 5 below shows the evaluation results of the mechanical properties, stress corrosion cracking life, weldability, and stress corrosion cracking life of the welded part of the test materials in the T6 state. The evaluation criteria for stress corrosion cracking life and weldability were the same as in Production Example 1. In addition, the stress corrosion cracking life of the welded part was evaluated by applying a bending stress equivalent to 75% of the proof stress of the solidified part in a direction perpendicular to the solidified part of the molten pool, and immersed it in the same aqueous solution as in Production Example 1. The number of days until cracking occurred was determined.

From the results in Table 5, it can be seen that all the examples according to the present invention have excellent mechanical properties, but there is no cracking in the weld or the weld heat affected zone, and they also have excellent stress corrosion cracking resistance of the parent metal and weld zone. There is. On the other hand, as shown in Table 4, the comparative examples in which the homogenization treatment conditions were not met were considerably inferior in any of the evaluation criteria.

"Effects of the Invention" According to the present invention as explained above, it is possible to obtain a good stress corrosion cracking life and to obtain a highly reliable welded joint free of weld cracking and micro-cracking, which is different from conventional re-venting. AI-Zn used only for bonding
- MIG and TIG for welding Mg Cu alloy materials by forming a sufficient molten pool.

This invention has the advantage of being able to form industrially advantageous structures by applying it to spot resistance welding methods, etc., and can be said to be an invention with great industrial effects.

[Brief explanation of the drawing]

The drawing shows the technical relationship of the present invention, and is a cross-sectional explanatory diagram showing the occurrence of cracks in a welded part.

Claims (1)

[Claims] Zn: 5.0-7.0wt%, Mg: 1.0-3.0w
t%, Cu: 0.5~1.8wt%, Zr: 0.05~
0.20wt%, V: 0.03-0.20wt%, Ti
: Contains 0.02 to 0.15 wt%, and also contains Zr, V
and Ti in the range of 0.10 to 0.40 wt%, and the balance is Al and impurities.
Hold at a temperature of 00 to 460°C for 8 to 24 hours to perform a first stage homogenization treatment, then hold at a temperature of 480 to 520°C for 8 to 24 hours to perform a second stage homogenization treatment,
A method for producing a high-strength aluminum alloy material with excellent weldability, which is characterized in that it is then subjected to a drawing process using a conventional method.