HK1032020B - Aluminium-magnesium weld filler alloy, method of manufacturing the same and method for constructing welded construction - Google Patents

Description

Aluminum-magnesium solder alloy, method of manufacturing the same, and method of constructing solder structure

Technical Field

The present invention relates to an aluminium-magnesium based solder (weld filler) alloy, which is particularly suitable for the construction of large welded structures such as storage tanks for marine and land transportation and ships. For example: the solder alloy of the invention can be used in the welding structure of single-hull long rafts (catamarans of monohull type), yachts, light high-speed ships and other marine ships. The solder alloys of the present invention can also be used to build many other structures, such as: LNG tanks, storage warehouses, tank trucks, pressure vessels, bridges, rail wagons, and the like. In addition, the invention also relates to a manufacturing method of the aluminum-based welding wire and a construction method of a welding structure.

Description of the related Art

Al-Mg based solder alloys are widely used in large welded structures such as land and marine transportation storage tanks and ships, one of the standard alloys being the AA5183 alloy, the nominal composition (wt.%) of which is as follows:

Mg 4.3～5.2

Mn 0.5～1.0

zn of maximum 0.25

Cr 0.05～0.25

Ti is 0.15 max

Fe is 0.40 max

Si max 0.40

Cu max 0.10

Other (single) max 0.05

(Total) maximum 0.15

The balance being aluminum.

The AA5183 welding wire is particularly widely applied to welding structures of ships, catamarans, high-speed ships and other marine ships, and the alloy has wide application mainly because of high strength, high corrosion resistance, high bending capacity and high weldability. The weld strength of the AA5183 alloy can be increased by increasing the Mg content of the alloy without a large loss of ductility. However, increasing the Mg content in the Al — Mg-based solder alloy causes a drastic decrease in corrosion resistance.

Some other Al — Mg alloys disclosed in the prior art documents are described below.

Japanese patent application JP- ｃA-05169290 proposes ｃA filler alloy comprising (wt.%):

Zn 1～6

mg 3 to 6 (here Zn ≦ Mg)

Mn 0.2～0.9

Cr 0.05～0.5

Ti 0.05～0.2

B 0.01～0.2

Zr 0.05～0.2

The balance being aluminum.

The filler alloy is used for setting the speed of more than 1-3 multiplied by 10²In the welding technique of DEG C/sec, therefore, the amount of Zr added may be larger than the content thereof in solid solution.

British patent application GB-a-2000806 proposes another filler alloy, the composition (wt.%) of which is as follows:

up to 5.5% Mg

0.2～0.5％Cu

The balance being substantially aluminum.

In the embodiments and the dependent claims, the components are in turn defined as:

zn 1.0 to 4.0, preferably 2.7 to 3.3

Mg 2.0 to 5.0, preferably 3.7 to 4.3

Cu 0.2 to 0.5, preferably 0.25 to 0.35

Mn 0.3 to 2.5, preferably 0.35 to 0.45

Ti 0.05～0.2

Cr 0.05～0.3

Zr 0.05～0.2

Si less than 0.2

Fe is less than 0.4

The balance being aluminum.

In the examples, where it is noted that Cu must be added, the filler alloy disclosed in this patent application is suitable for use between AlZnMg alloys or in welded structures of AlZnMg alloys with other aluminum alloys.

European patent application EP- ｃA-0799900 relates to an aluminium alloy in the form of ｃA plate or extrusion for large welded structures, having properties exceeding the standard aｃA5083 series and having ｃA composition (wt.%):

Mg 4.5～7.0

Mn 0.4～1.2

Zn 0.5～5.0

zr maximum 0.3

Maximum Cr of 0.3

Ti of 0.2 or less

Maximum Fe of 0.5

Si max 0.5

Cu max 0.4

The balance being aluminum and unavoidable impurities.

The above-cited patent applications do not teach their use as solder alloys nor suggest that their performance is superior to standard AA5183 filler alloys.

Brief summary of the invention

It is an object of the present invention to provide an Al-Mg based solder alloy with which a solder joint has higher strength when used for soldering an aluminum alloy as compared with a standard filler alloy such as AA5183 alloy; it is another object of the present invention to provide an Al-Mg based solder alloy that can achieve ductility, bendability, corrosion resistance at least comparable to those of standard Al-Mg based wires, such as AA5356, and particularly AA 5183.

According to the present invention, there is provided an aluminium-based solder alloy in the form of a welding wire, having the composition (weight ratio: wt.%):

Mg 5.0～6.5

Mn 0.7～1.2

Zn 0.4～＜2.0

Zr 0.05～0.3

maximum Cr of 0.3

Ti of 0.2 or less

Maximum Fe of 0.5

Si max 0.5

Cu max 0.25

The balance being aluminum and unavoidable impurities.

In addition, the invention also provides a manufacturing method of the aluminum-based welding wire, which comprises the following steps: preparing an aluminum-based alloy material body having the above composition and drawing the aluminum-based alloy material body into a welding wire.

With the present invention, welded aluminum joints with strength higher than standard AA5183 welds can be provided. The solder alloy according to the present invention has been successfully used between AlMg alloys or in a welded structure of AlMg alloy with other aluminum alloys. It should be noted in particular that: when the AlMg alloy of the welding structure and the solder alloy of the invention are in the same chemical composition range, the welding of the alloy of the invention can obtain good effect.

It has also been found that the solidification range of the alloy is increased with a higher content of both Mg and Zn compared to a standard AA5183 filler wire, the solidification range of the solder alloy of the invention being 568-639 ℃ and the solidification range of the standard AA5183 alloy being 574-638 ℃, which is particularly advantageous when using the solder alloy of the invention for the construction of solder structures, such as: the transition from the weld to the base material can be smoothed, thereby reducing the notch effect and thereby improving the fatigue performance of the welded joint. In addition, during fusion welding, surface oxides, such as alumina, are present at the location where the weld overlaps the base material. The high fluidity of the solder alloy of the present invention allows for an increased adhesion surface for soldering, thereby reducing the deleterious "bridging" effect. In addition, relatively flat welds can be obtained with finer or smoother undulations in the weld surface.

It is believed that better performance can be achieved with the present invention: the strength level of the weld is particularly improved due to the increased Mg and Mn content and the addition of Zr. Good corrosion resistance at high Mg content benefits from the uniform precipitation of relatively few anodic Mg and Zn containing intermetallic compounds in the weld microstructure.

According to the invention, the content of alloying elements in the aluminium-based solder alloy is limited for the following reasons (all percentages in weight%: wt.%):

mg: mg is the main strengthening element in the solder alloy, the content of Mg is less than 5.0 percent, the welding line can not achieve the required strength, and the addition amount of Mg exceeds 6.5 percent, so the welding wire is very difficult to manufacture by the solder alloy. The reason for the difficulty in manufacturing is that severe cracks are generated during continuous casting or semi-continuous casting and subsequent processing. For the purposes of manufacturability and strength, the preferred Mg content is 5.0-6.0%.

Mn: mn is a basic additive element and is matched with Mg, and Mn can improve the strength of a welded joint. An Mn content of less than 0.6% cannot provide a sufficient strength of the welded joint; while the Mn content exceeds 1.2%, the production of the wire drawing material is very difficult, and the preferable minimum Mn content is 0.7% for securing the strength.

Zn: zn is an important additive element for ensuring the corrosion resistance of the welding seam, and can also improve the strength of the welding seam to a certain extent. Zn is added in an amount of less than 0.4%, sufficient corrosion resistance comparable to that of the AA5183 alloy weld joint cannot be provided; whereas due to weldability requirements the Zn content has to be limited to below 2.0%, more preferably the Zn content should be limited to a maximum of 0.9%, in a further preferred embodiment the Mg/Zn ratio should be larger than 5 to obtain a good combination of strength and corrosion resistance.

Zr: zr has important significance for improving the strength of the welding seam and preventing cracks in the welding process. Zr contents exceeding 0.3% lead to the formation of very coarse acicular primary particles, which cause unacceptable failure during drawing, so that the Zr content must be kept below 0.3%.

Ti: ti is an important grain refiner during weld solidification, however, Ti in combination with Zr can form an undesirable coarse primary phase that can reduce weld toughness and fatigue strength. To avoid this, the Ti content must be kept below 0.2%, and the preferable range of Ti content is 0.05 to 0.1%.

Fe: fe forms Al-Fe-Mn compounds during casting, thereby limiting the beneficial effects of Mn. Fe content exceeding 0.5% forms coarse primary particles, thereby reducing the fatigue life of the solder alloy solder joint of the present invention. Therefore, the preferable range of Fe content is 0.10 to 0.30%.

Si: si forms Mg which is hardly soluble in Al-Mg alloys (Mg content > 4.5%)₂Si, and therefore Si, limits the beneficial effect of Mg, and Si also combines with Fe to form coarse AlFeSi particles, thereby affecting the fatigue life of the welded joint of the welded structure. To avoid loss of action of the main strengthening element Mg, the Si content must be kept below 0.5%. The preferable Si content is 0.10 to 0.30%.

Cr: cr increases the corrosion resistance of the alloy, however, Cr limits the solubility of Mn and Zr, so to avoid the formation of coarse primary phases, the Cr content must be kept below 0.3%, preferably in the range of 0-0.15%.

Cu: the Cu content should be kept below 0.25%, and Cu contents exceeding 0.25% cause a great deterioration in the pitting corrosion resistance of the solder alloy of the present invention. The preferred Cu content should be below 0.10%, and the more preferred Cu content should be at the level of the impurities, i.e. below 0.05%.

The balance of aluminum and inevitable impurities, generally 0.05% of each impurity element at the maximum, and 0.15% of the total impurities at the maximum. With respect to the impurity range, the beryllium content should preferably be limited to about 0.00008%.

The solder alloy of the present invention is most preferably provided in the form of a drawn wire, which may be manufactured, for example, by: the alloy is extruded by a porous die, the temperature range during extrusion is 200-550 ℃, and the speed range of an extrusion rod is 1-25 m/min. And then drawing the extruded bar stock for multiple times to form a wire. The extrusion ratio commonly used in aluminum wire drawing can be adopted, and the intermediate annealing at 250-550 ℃ can be adopted in the wire drawing process. The drawn wire may be subjected to final annealing at a temperature of 250 to 550 ℃ if necessary. The soaking time in each annealing process is 10 minutes to 10 hours. The diameter of the drawn wire is usually 0.6 to 6.0 mm. The wire may also be made by: continuously casting the alloy into, for example, a round bar shape; directly coiling the bar or coiling the rolled bar; then, the wire is drawn to form a filler wire.

The invention also includes a method of constructing a welded structure such as a marine or land transportation storage tank or vessel, comprising the steps of:

(a) preparing separate individual components of a welded structure;

(b) the components are welded together with an aluminum-based solder alloy having the above characteristics.

The various components of the welded structure are preferably in the form of extrusions, plates, sheets, or combinations thereof.

It can be found that: by using the solder alloy according to the invention, a smooth transition of the weld to the base material is obtained, compared to a standard AA5183 filler wire, whereby the notch effect is reduced and the fatigue properties of the welded joint are improved. It can also be found that: the weld-bonding surface is enlarged after the solidification range of the solder alloy is enlarged, thereby reducing the harmful 'bridging' effect. In addition, it is also found that: the use of the solder alloy according to the invention results in a flatter weld and a finer and/or smoother waviness of the weld surface compared to standard AA5183 welding wires.

Examples

Example 1

Two DC-as-cast extruded ingots of solder alloy according to the invention (see table 1 for weight percentage composition) were extruded into round bar-shaped extrusions 9.5mm in diameter, and the feedstock for subsequent wire cold drawing was produced using a standard direct extrusion process. A portion of the batch of each extruded solder alloy rod was then redrawn into 1.2, 1.6, 3.2, and 4.0mm diameter filler wires, respectively, having diameters consistent with standard MIG (Metal inert gas welding) wire diameters. Another portion of the batch of each solder alloy was made into 1.5, 2.0, 2.5, 3.2, 5.0, 6.0, and 8.0mm diameter wires consistent with TIG (tungsten inert gas welding) standard wire diameters, respectively. The wire drawing comprises a series of cold drawing processes and intermediate annealing at 380 ℃. For reference, this example also used a standard solder alloy AA5183 (see table 1).

1000X 8mm (length of substrate X width X thickness) standard MIG welded panels were prepared using 1.2mm diameter welding wire, the chemistry of the plates or substrates used is also given in Table 1, all the plates were in the H321 temper, and the chemistry of plate A corresponded to the standard AA5083 alloy.

Tensile test and corrosion test specimens were taken from the welded panels. Tensile properties of the welded panels were determined using a standard tensile test, pitting corrosion resistance and spalling corrosion resistance were evaluated using the ASSET test according to ASTM G66, and SCC resistance was evaluated using the four-point bending test according to the ASTM G39 protocol.

Table 2 lists the tensile results after 3 to 4 trials of each combination, from which it can be seen that: by replacing the AA5183 solder alloy with the welding wire according to the invention, the tensile properties of the welded panels are significantly improved, with optimum results being obtained when welding panels with the welding wire according to the invention in the same chemical composition range as the welding wire alloy according to the invention.

Table 3 shows the ASSET test results in which N indicates no corrosion cracking, P indicates the presence of pitting, and a to D indicate gradual deterioration of the corrosion resistance. As can be seen from table 3: when the welding wire is used for welding, the corrosion resistance of a welding plate is equal to or better than that of a welding plate when the welding wire is used for welding by using a standard solder alloy. Regardless of the combination used, samples from all combinations passed the 1000 hour SCC test according to the ASTM G39 specification. It can be seen from this that: the strength of the welded plate is improved without reducing the stress corrosion resistance.

Example 2

Welding was carried out by the double-sided TIG method in the same manner as in example 1, for which 4mm diameter welding wire was used, and the tensile properties results are shown in Table 4.

As can be seen from table 4: the strength of the welded plates obtained when the base material/wire combination is plate B/invention wire 1 is much higher than the welded plates obtained with the plate a/AA5183 wire combination, which is a comparative combination of the AA5053 alloy with the currently widely used AA5183 wire combination.

TABLE 1

	Mg	Mn	Zn	Zr	Cu	Cr	Fe	Si	Ti	Al
											Solder 1 of the invention solder 2AA5183 solder plate A plate B of the invention	5.305.894.604.825.30	0.840.820.680.650.84	0.550.500.010.090.55	0.130.12-0.010.13	0.0130.010.040.030.013	0.0490.070.080.070.049	0.190.210.330.150.19	0.110.070.150.090.11	0.0150.080.010.100.015	bal.bal.bal.bal.bal.

TABLE 2

Combination of		0.2% yield Strength (MPa)	Ultimate tensile strength (MPa)	Elongation (%)
					Panel A	AA5183 solder	125	275	15.2
127	282	15.4
			130	277			17.1
128	274	14.5
			Panel A	The solder of the invention			141	297	14.6
142	296	13.9
					140	301	14.3
145	305	11.1
					Panel B	AA5183 solder	160	310	15.2
165	312	16.2
			162	317			13.3
164	320	16.4
			Panel B	Solder 1 of the invention			170	319	15.7
172	325	14.2
					174	324	11.6
171	331	10.9
					Panel B	Solder 2 of the invention	180	341	16.2
177	345	14.7
			181	340			15.9

TABLE 3

Combination of	Base material	Heat affected zone	Weld seam
				Board A/AA5183 solder	PB/PC	N	N
Plate A/solder of the invention 1	PB	N	N
				Board B/AA5183 solder	N	N	N
Plate B/solder 1 of the invention	N	N	N
				Plate B/inventive solder 2	N	N	N

TABLE 4

Combination of	0.2% yield Strength (MPa)	Ultimate tensile strength (MPa)	Elongation (%)
				Board A/AA5183 solder	125	275	15.2
127	282	15.4
			130		277	17.1
Plate B/solder 1 of the invention	168	330					16.2
			170	335	16.5

Claims (9)

1. An aluminium-based solder alloy in the form of a welding wire consisting of (in weight percent: wt.%):

Mg 5.0～6.5

Mn 0.7～1.2

Zn 0.4～＜2.0

Zr 0.05～0.3

maximum Cr of 0.3

Ti of 0.2 or less

Maximum Fe of 0.5

Si max 0.5

Cu is 0.25 max, and the balance is aluminum and inevitable impurities.

2. An aluminium-based solder alloy in the form of a welding wire according to claim 1, characterised in that the Mg content is in the range of 5.0 to 6.0 wt.%.

3. Aluminium-based solder alloy in the form of a welding wire according to claim 1 or 2, characterised in that the Cr content is not higher than 0.15 wt.%.

4. The aluminum-based solder alloy in the form of a welding wire according to claim 1 or 2, characterized in that the Zn content is not higher than 0.9 wt.%.

5. An aluminium-based solder alloy in the form of a welding wire according to claim 3, characterised in that the Zn content is not higher than 0.9 wt.%.

6. A method of manufacturing an aluminum-based welding wire according to any one of claims 1 to 5, characterized by comprising the steps of:

(a) an aluminum-based alloy material body having the following composition (wt.%) was prepared

Mg 5.0～6.5

Mn 0.7～1.2

Zn 0.4～＜2.0

Zr 0.05～0.3

Maximum Cr of 0.3

Ti of 0.2 or less

Maximum Fe of 0.5

Si max 0.5

Cu max 0.25

The balance of aluminum and inevitable impurities; and

(b) drawing the aluminum-based alloy material body into a welding wire.

7. A method according to claim 6, characterized in that the alloy is provided in the form of an extrusion.

8. A method of constructing a welded structure comprising the steps of:

(a) preparing individual discrete components of the welded structure;

(b) welding the individual discrete components together with an aluminium-based solder alloy in the form of a welding wire according to any one of claims 1 to 5.

9. The method of claim 8, wherein the individual components of the welded structure are provided as extrusions, plates, sheets, or combinations thereof.