CN101301710A - A kind of rare earth-containing magnesium alloy medium-temperature solder and preparation method thereof - Google Patents

Abstract

A rare earth-containing magnesium alloy medium-temperature solder and a preparation method thereof belong to the technical field of manufacturing magnesium alloy connecting materials. The existing magnesium alloy solder and its preparation have problems such as high cost, high melting point, poor process performance and the like. The components and weight percentages of the rare earth-containing magnesium alloy medium-temperature solder provided by the invention are: Al: 2-10%, Zn: 40-55%, Mg: 38-50% and Nd: 0.1-2%. The invention prepares rare earth-containing magnesium alloy mid-temperature solder by melting Mg, Al, Zn and Mg-Nd master alloys and casting. The brazing material of the invention has the advantages of simple preparation, low cost, low melting temperature, excellent brazing process performance and the like.

Description

A kind of rare earth-containing magnesium alloy medium-temperature solder and preparation method thereof

technical field

The invention belongs to the technical field of manufacturing magnesium alloy connecting materials, and in particular relates to a rare earth element-containing magnesium alloy medium-temperature solder and a preparation method thereof.

Background technique

Magnesium alloy is known as the green engineering structural material in the 21st century, and it has extremely important use value in the fields of aerospace, automobile and electronics. However, during the welding process of magnesium alloys, problems such as oxidative combustion, cracks, pores, and large deformation after welding may occur, making it difficult to obtain welded joints that match the properties of the base metal. In recent years, with the demand for magnesium alloy components with complex structures and poor openness, as well as components of dissimilar materials such as magnesium alloys and aluminum alloys, magnesium alloys and steels, the use of brazing methods to join magnesium alloys has received extensive attention.

The research on magnesium alloy brazing materials is still immature, and there is no brazing material that can be widely used. At present, there are only three commercial magnesium alloy brazing filler metals in foreign countries: BMg-1, BMg-2a and MC3 alloys. The brazing temperature of these filler metals is relatively high (about 600 ° C), which exceeds the ignition point and melting point of magnesium alloys. Therefore, it is difficult to apply to the brazing of common magnesium alloys, such as AZ31B (melting point 566°C). In addition, higher brazing temperature will reduce the performance of magnesium alloy joints, especially the mechanical properties. Therefore, the development of low-melting-point medium-temperature solder is an important research direction for magnesium alloy brazing. For example, the In-34.5Mg-0.8Al-0.2Zn solder developed by Japanes e Pan.2004050278 has a brazing temperature of 490°C, and the tensile strength of the joint can reach the strength of AZ31B with a thickness of 0.9mm, which is about 275MPa, but the addition of In This brazing material is too expensive, greatly increases the cost of brazing, and is difficult to be widely used. In recent years, some people have added Mn, Be, Si, Ni and other elements on the basis of Mg-Al-Zn-based solder, but these solders are difficult to prepare, poor in processability, and especially need to be used in conjunction with flux. The problems such as poor corrosion resistance of joints have not been widely used.

In order to reduce the residual stress of the magnesium alloy base metal after cooling, the brazing temperature should be close to the recrystallization temperature of the magnesium alloy, and the melting temperature interval of the solder should be small; the solder and the base metal can be well wetted to reduce welding defects; the joint has Good mechanical properties. Therefore, it is an urgent technical problem to be solved in the field of magnesium alloy connecting materials to develop a medium-temperature solder with excellent process performance and joint mechanical properties, low cost, and simple process and its preparation method to make it suitable for flux-free ultrasonic brazing.

Contents of the invention

The purpose of the present invention is to solve the problems in the prior art, and provide a brazing filler metal that is easy to prepare, has excellent process performance, low melting temperature and cost, and has suitable strength and a preparation method thereof.

The components in the rare earth-containing magnesium alloy medium-temperature solder provided by the present invention and their weight percentages are: Al: 2-10%, Zn: 40-55%, Mg: 38-50% and Nd: 0.1 -2%.

Among them, Al and Mg form a limited solid solution to improve the room temperature strength, hardness and fluidity of the brazing material; Zn improves the strength of the brazing filler metal through the dual strengthening effect of solid solution and aging, and reduces the corrosion problem caused by the presence of Fe and Ni in the magnesium alloy; Nd improves the brazing filler metal. Material activity and wettability, improve joint strength.

The preparation method of the rare earth-containing magnesium alloy intermediate temperature solder provided by the present invention comprises the following steps:

1) Prepare Mg ingot, Al ingot, Zn ingot and Mg-Nd master alloy according to the weight percentage of each component in the target solder: Al: 2-10%, Zn: 40-55%, Mg: 38- 50% and Nd: 0.1-2%;

2) After preheating the graphite crucible to 100°C, sprinkle a covering agent accounting for 5wt% of the target solder melting amount into the bottom of the crucible, and add the Mg ingot and Al ingot prepared in step 1), and then sprinkle in the target solder melting amount Add 5wt% covering agent and heat up to 700-800°C;

3) After the Mg ingot and the Al ingot are completely melted, add the Zn ingot prepared in step 1) and the master alloy of Mg-Nd, sprinkle into the covering agent accounting for 5wt% of the target solder melting amount;

4) After the alloy is completely melted, stir the alloy melt for 2 minutes, let it stand for 10 minutes, then take it out of the furnace, and remove the slag;

5) casting the alloy solution in step 4) in a low-carbon steel mold at a casting temperature of 650-750° C., and air-cooling to room temperature to obtain a rare earth-containing magnesium alloy medium-temperature solder.

Wherein, the components and contents of the covering agent described in steps 2) and 3) are BaCl ₂ : 35.0wt%, LiCl: 30.0wt%, KCl: 10.0wt% and CaF ₂ : 25.0wt%, according to conventional physical mixing be made of.

Compared with the prior art, the present invention has the following beneficial effects:

1) The present invention adopts effective and cheap magnesium alloying elements Al and Zn, which can effectively reduce the production cost, and the preparation process is simple, and the solder composition is uniform.

2) The brazing material prepared by the present invention has excellent process performance, low melting point, effectively reduces the brazing temperature, is suitable for the connection of common magnesium alloy AZ31B, and has a small melting range and good solder fluidity. Due to the addition of rare earth elements, the increase The surface activity of the solder is improved, so the solder has good wettability. With the assistance of ultrasonic vibration, flux-free brazing can be realized, which avoids the corrosion of the solder to the brazed joint, and the joint rarely has defects. , to ensure the mechanical properties of magnesium alloy joints.

Detailed ways

The crucible resistance furnace used in the following examples is SG2A7.5-10 crucible resistance furnace.

comparative example

After preheating the graphite crucible to 100°C, sprinkle 50g of covering agent (among them, 35.0wt.% BaCl ₂ , 30.0wt.% LiCl, 10.0wt.% KCl and 25.0wt.% CaF ₂ ) on the bottom of the crucible, and Put 550g of Mg ingot and 60g of Al ingot in the crucible, sprinkle 50g of covering agent, heat up to 700°C, after it is completely melted, add 500g of Zn ingot, then sprinkle in 50g of covering agent, stir for 2 minutes after the alloy is completely melted, let it stand for 10 minutes, and then come out of the furnace , scoop out the slag, cast in a low-carbon steel mold at a casting temperature of 700°C, and air-cool to room temperature to obtain a magnesium alloy medium-temperature solder.

Example 1

After preheating the graphite crucible to 100°C, sprinkle 50g of covering agent (among them, 35.0wt.% BaCl ₂ , 30.0wt.% LiCl, 10.0wt.% KCl and 25.0wt.% CaF ₂ ) on the bottom of the crucible, and put Put in 360g Mg ingot and 70g Al ingot, sprinkle 50g of covering agent, heat up to 800°C, after it is completely melted, add 530g of Zn ingot and 143g of Mg-Nd master alloy (containing 20wt% Nd), then sprinkle in 50g of covering agent, and wait until the alloy is completely melted Stir for 2 min, stand still for 10 min, take out the furnace, remove the slag, cast in a low-carbon steel mold at a casting temperature of 750°C, and air-cool to room temperature to obtain a rare earth-containing magnesium alloy medium-temperature brazing filler metal.

Example 2

After preheating the graphite crucible to 100°C, sprinkle 50g of covering agent (including 35.0wt.% BaCl ₂ , 30.0wt.% LiCl, 10.0wt.% KCl and 25.0wt.% CaF ₂ ) on the bottom of the crucible, and put 410g Mg and 50g Al ingots, then sprinkle 50g of covering agent, heat up to 800°C, after complete melting, add 510g of Zn ingot and 143g of Mg-Nd master alloy (containing 20wt% Nd), then sprinkle 50g of covering agent, wait for complete melting Stir for 2 minutes, stand still for 10 minutes, take out the furnace, remove the slag, cast in a low-carbon steel mold at a casting temperature of 650°C, and air-cool to room temperature to obtain a rare earth-containing magnesium alloy medium-temperature brazing filler metal.

Example 3

After preheating the graphite crucible to 100°C, sprinkle 50g of covering agent (including 35.0wt.% BaCl ₂ , 30.0wt.% LiCl, 10.0wt.% KCl and 25.0wt.% CaF ₂ ) on the bottom of the crucible, and put 443g Mg and 70g Al ingots, then sprinkle 50g of covering agent, heat up to 780°C, after it is completely melted, add 520g of Zn ingot and 71g of Mg-Nd master alloy (containing 20wt% Nd), then sprinkle 50g of covering agent, stir after it is completely melted 2 minutes, stand still for 10 minutes, then take out the furnace, remove the slag, cast in a low-carbon steel mold at a casting temperature of 650°C, and air-cool to room temperature to obtain a rare earth-containing magnesium alloy medium-temperature brazing filler metal.

Example 4

After preheating the graphite crucible to 100°C, sprinkle 50g of covering agent (including 35.0wt.% BaCl ₂ , 30.0wt.% LiCl, 10.0wt.% KCl and 25.0wt.% CaF ₂ ) on the bottom of the crucible, and put 477g Mg and 20g Al ingots, then sprinkle 50g of covering agent, heat up to 730°C, after it is completely melted, add 515g of Zn ingot and 107g of Mg-Nd master alloy (containing 20wt% Nd), then sprinkle 50g of covering agent, and wait for complete melting Stir for 2 minutes, stand still for 10 minutes, take out the furnace, remove the slag, cast in a low-carbon steel mold at a casting temperature of 700°C, and air-cool to room temperature to obtain a rare earth-containing magnesium alloy medium-temperature brazing filler metal.

Example 5

After preheating the graphite crucible to 100°C, sprinkle 50g of covering agent (including 35.0wt.% BaCl ₂ , 30.0wt.% LiCl, 10.0wt.% KCl and 25.0wt.% CaF ₂ ) on the bottom of the crucible, and put 572g Mg and 100g Al ingots, then sprinkle 50g of covering agent, heat up to 700°C, after it is completely melted, add 415g of Zn ingot and 36g of Mg-Nd master alloy (containing 20wt% Nd), then sprinkle 50g of covering agent, stir after it is completely melted 2 minutes, stand still for 10 minutes, take out the furnace, remove the slag, cast in a low-carbon steel mold at a casting temperature of 750°C, and air-cool to room temperature to obtain a rare earth-containing magnesium alloy medium-temperature brazing filler metal.

Example 6

After preheating the graphite crucible to 100°C, sprinkle 50g of covering agent (including 35.0wt.% BaCl ₂ , 30.0wt.% LiCl, 10.0wt.% KCl and 25.0wt.% CaF ₂ ) on the bottom of the crucible, and put 620gMg and 60gAl ingots, then sprinkle 50g of covering agent, heat up to 700°C, after complete melting, add 439g of Zn ingot and 7.2g of Mg-Nd master alloy (containing 20wt% Nd), then sprinkle 50g of covering agent, and wait for complete melting Stir for 2 minutes, stand still for 10 minutes, take out the furnace, remove the slag, cast in a low-carbon steel mold at a casting temperature of 680°C, and air-cool to room temperature to obtain a rare earth-containing magnesium alloy medium-temperature brazing filler metal.

Adopt the brazing filler metal that comparative example and embodiment 1-6 make carry out ultrasonic-assisted brazing to AZ31B thin plate (3mm thick), measure spreading area and joint shear strength; Adopt differential scanning calorimetry (DSC) to record brazing filler metal The liquidus and solidus temperatures are shown in Table 1.

From Table 1, it can be seen that the addition of rare earth elements increases the spreading area and shear strength of the solder, but has little effect on the liquidus and solidus temperatures of the solder, and the melting temperature of the solder is higher than that of the solder. Low, suitable for brazing process of medium temperature magnesium alloy.

Table 1 Spreading area, melting zone and joint shear strength of solder

Claims (3)

1, a kind of magnesium alloy intermediate temperature solder that contains rare earth is characterized in that, each component and shared percentage by weight thereof in the solder are: Al:2-10%, Zn:40-55%, Mg:38-50% and Nd:0.1-2%.

2, the preparation method who contains the magnesium alloy intermediate temperature solder of rare earth according to claim 1 is characterized in that, may further comprise the steps:

1) with Mg ingot, Al ingot, Zn ingot and Mg-Nd intermediate alloy according to target in the solder the shared percentage by weight of each component get the raw materials ready: Al:2-10%, Zn:40-55%, Mg:38-50% and Nd:0.1-2%;

2) graphite crucible is preheated to 100 ℃ after, crucible bottom is sprinkled into the coverture that accounts for target solder melting amount 5wt%, and adds Mg ingot and the Al ingot for preparing in the step 1), is sprinkled into the coverture that accounts for target solder melting amount 5wt% again, is warming up to 700-800 ℃;

3) treat that Mg ingot and Al ingot melt fully after, add the Zn ingot and the Mg-Nd intermediate alloy that prepare in the step 1), be sprinkled into again and account for target solder melting amount 5wt% coverture;

4) treat that alloy melts fully after, the alloy liquation is stirred 2min, come out of the stove after leaving standstill 10min, drag for slag;

5) alloy solution in the step 4) is cast in the mild steel mould, cast temperature is 650-750 ℃, and air cooling obtains containing the magnesium alloy intermediate temperature solder of rare earth to room temperature.

3, preparation method according to claim 2 is characterized in that step 2) and 3) described in the component and the content of coverture be BaCl ₂: 35.0wt%, LiCl:30.0wt%, KCl:10.0wt% and CaF ₂: 25.0wt%.