CN102581473B - Ultrasonic assisted semi-solid friction stir welding method applicable to connection of particle reinforced aluminum matrix composite - Google Patents

Abstract

An ultrasonic-assisted semi-solid friction stir welding process method based on the rotation and vibration of the stirring tool for the connection of particle-reinforced aluminum matrix composites, which solves the problem of the existence of stirring tools in the connection of particle-reinforced aluminum matrix composites in the existing conventional friction stir welding technology Problems such as severe wear and high manufacturing cost of the stirring tool. Butt-clamp weldment A and weldment B on the workbench; the stirring needle of the stirring tool penetrates into the part to be welded at a speed of 1000-5000rpm, the fixed shoulder of the stirring tool does not rotate and does not penetrate into the workpiece, and keeps the fixed axis The lower end surface of the shoulder is closely attached to the upper surface of the workpiece; the ultrasonic wave of the ultrasonic transducer is directly transmitted to the inside of the area to be welded through the stirring needle connected with the ultrasonic horn; The tool moves along the weld seam at a speed of 50-1000mm/min. The invention effectively transmits the ultrasonic wave to the part to be welded, not only refines the crystal grains in the stirring area, but also greatly reduces the wear of the stirring needle.

Description

An ultrasonic-assisted semi-solid friction stir welding method suitable for joining particle-reinforced aluminum matrix composites

Technical field: The present invention relates to a welding method, especially an ultrasonic-assisted semi-solid friction stir welding method suitable for joining particle-reinforced aluminum matrix composite materials, which belongs to the technical field of material joining.

Background technology: Due to the advantages of high specific strength, high wear resistance, good heat treatability, and flexible preparation process, particle-reinforced aluminum matrix composites have broad application prospects in aviation, aerospace, military, automobile, electronics and other fields. As a new generation of advanced engineering materials, the welding of particle-reinforced aluminum matrix composites is a research hotspot among scholars at home and abroad. Judging from the current research status, all welding methods suitable for aluminum alloys can be applied to the welding of aluminum matrix composites, but due to the difference in physical properties between the basic aluminum alloy and the reinforcing phase and the instability of thermodynamics, using It is difficult to obtain high-quality welded joints by conventional fusion welding methods. Friction stir welding is a solid phase connection technology invented by the British Welding Institute in 1991. It has the advantages of low deformation, high strength, no conventional fusion welding defects and green and pollution-free. It appears in the particle reinforced aluminum matrix composite material. Connections offer a new way of thinking. The hardness of SiC and other reinforcing phases in aluminum matrix composites is very high. If ordinary materials are used to make stirring tools, the wear of the friction stirring head will be very serious in the later stage of welding, and there may even be a risk of breaking. Therefore, it was proposed to use GT35 Steel-bonded hard alloy is used to manufacture stirring pins, but the price of GT35 steel-bonded hard alloy is very expensive, which is not conducive to the promotion and application of friction stir welding technology in particle-reinforced aluminum matrix composites.

Summary of the invention: In order to solve the shortcomings of the existing conventional friction stir welding technology, such as the serious wear of the stirring tool and the high manufacturing cost of the stirring tool, when connecting particle reinforced aluminum matrix composites, the present invention proposes a method based on the fixed shoulder, high-speed rotation of the stirring needle and Vibration-based ultrasonic-assisted semi-solid friction stir welding method.

In order to achieve the above purpose, the technical solution adopted in the present invention is: an ultrasonic-assisted semi-solid friction stir welding method suitable for the connection of particle-reinforced aluminum matrix composite materials, specifically adopting the following steps:

Step 1. Place weldment A and weldment B on the same horizontal plane, and clamp them on the workbench with a fixture.

Step 2. The stirring needle forming the stirring tool is jagged, its maximum diameter is greater than 1.5 times the thickness of the workpiece and the cone angle is less than 5°. The stirring needle penetrates into the part to be welded at a speed of 1000-5000 rpm; the shaft shoulder forming the stirring tool is fixed, And the diameter of the shaft shoulder is greater than 2 times the thickness of the workpiece; the ultrasonic wave of the ultrasonic transducer is directly transmitted to the inside of the area to be welded through the stirring needle connected with the ultrasonic horn. The parameters of the ultrasonic wave are as follows: the frequency is 16 ~ 60K and the amplitude is 20 ~50μm; the penetration speed of the stirring tool is 1 ~ 4mm/min, the penetration depth of the stirring needle into the workpiece is 0.1 ~ 0.3mm smaller than the thickness of the workpiece, the shaft shoulder does not penetrate into the workpiece, and the end surface of the shaft shoulder is kept in close contact with the upper surface of the workpiece, so that To improve the quality of the weld surface and reduce the strength loss of the joint.

Step 3. When the stirring tool reaches the set plunging depth, the stirring needle stops pricking and continues to rotate for 1 to 5 minutes; then, the stirring tool moves along the joint between weldment A and weldment B at a speed of 50 to 1000 mm/min. The butt surface moves horizontally until the welding is completed.

The beneficial effects of the present invention are:

1. The stirring needle rotates at a high speed and the vibration and the friction between the weldment provide a large amount of heat to the part to be welded, resulting in the temperature of the material between the solidus and liquidus temperatures (that is, the semi-solid temperature), making the material near the stirring needle The degree of softening is increased, and the rotation, torsion and forward resistance are correspondingly reduced, which can effectively prevent the occurrence of defects such as tunnels and S-shaped lines, and reduce the requirements for clamping tools and stirring tools. It is suitable for welding particle-reinforced aluminum matrix composites.

2. The shaft shoulder of the stirring tool is fixed and does not penetrate into the surface of the workpiece. Rolling the welding material in the softened state can prevent the material in the stirring zone from flowing out of the weldment, avoid the generation of flash defects, and make the surface quality of the weldment better. Well, the mechanical properties of the welded joint are greatly improved.

3. Make the stirring needle, ultrasonic horn and ultrasonic transducer into a whole. The cone angle of the stirring needle is small and serrated, which can increase the contact area with the material to be welded, which is conducive to the effective amplification of ultrasonic waves. And it is transmitted to the inside of the welding part, using the characteristics of ultrasonic waves to refine the grain and reduce the wear of the welding material on the stirring pin, improve the performance of the joint, and promote the application of welding technology in particle reinforced aluminum matrix composites.

Description of drawings

Fig. 1 is a structural schematic diagram of a stirring tool.

Figure 2 is a schematic diagram of the ultrasonic-assisted semi-solid friction stir welding process suitable for joining particle-reinforced aluminum matrix composites.

Fig. 3 is a schematic diagram of the positional relationship between the stirring tool and the two plates to be welded during the friction stir welding process.

Detailed ways:

As shown in Figure 1: the stirring needle 1, the ultrasonic horn 3 and the ultrasonic transducer 4 are made into a whole, which effectively amplifies the ultrasonic wave and transmits it to the part to be welded; the stirring tool 5 consists of the stirring needle 1, the fixed shoulder 2. The ultrasonic horn 3 and the ultrasonic transducer 4 are composed. The fixed shoulder 2 is set on the stirring needle 1. The cone angle of the stirring needle 1 is small and serrated, which can increase the contact area with the welding material. In turn, the effect of ultrasonic waves is improved and the temperature of the part to be welded is increased.

As shown in Figure 2: the weldment A6 and the weldment B7 are butted and placed on the same horizontal plane (that is, the weldment A6 and the weldment B7 are paired), and the weldment A6 and the weldment B7 are both plates.

As shown in Figure 3: the lower end surface of the fixed shoulder 2 is kept in close contact with the upper surface of the workpiece to be welded but does not penetrate, the penetration depth of the stirring pin 1 is H, and the thickness of the weldment A6 and the weldment B7 are both T.

Embodiment one

An ultrasonic-assisted semi-solid friction stir welding process suitable for the connection of particle-reinforced aluminum matrix composite materials described in this embodiment is realized according to the following steps:

Step 1. Place the weldment A6 and the weldment B7 butt-connected and on the same horizontal plane (that is, pair the weldment A6 and the weldment B7)), and clamp them on the workbench with a fixture; the weldment A6 and the weldment B7 All are plates.

Step 2. The stirring needle 1 forming the stirring tool 5 is jagged, the maximum diameter is greater than 1.5 times the thickness of the workpiece, and the cone angle is less than 5°, and it is pierced into the part to be welded at a speed of 1000-5000rpm (that is, weldment A6 and weldment B7 the butt joint surface); the shaft shoulder 2 that forms the stirring tool 5 is fixed (that is, does not rotate) and the diameter of the shaft shoulder is greater than 2 times the thickness of the workpiece; the ultrasonic wave of the ultrasonic transducer 4 passes through the stirring needle 1 connected with the ultrasonic horn 3 Directly transmitted to the inside of the area to be welded, the parameters of the ultrasonic wave are as follows: the frequency is 16-60K and the amplitude is 20-50μm; the penetration speed of the stirring tool 5 is 1-4mm/min, and the penetration depth of the stirring needle 1 into the workpiece is 0.1 smaller than the thickness of the workpiece ~0.3mm, the shaft shoulder 2 does not penetrate into the workpiece, and the end surface of the shaft shoulder is kept in close contact with the upper surface of the workpiece, so as to improve the quality of the weld surface and reduce the strength loss of the joint.

Step 3. When the stirring tool 5 reaches the set plunging depth, the stirring needle 1 stops the pricking and continues to rotate for 1 to 5 minutes; then, the stirring tool 4 moves along the weldment A6 and the weldment at a speed of 50 to 2500 mm/min. The butt surface of piece B7 moves horizontally until the welding is completed.

Embodiment two

In step 2 of this embodiment, the rotation speed of the stirring needle is 3000-5000 rpm. The rotation speed of the stirring needle can be selected according to the specific conditions of weldment A6 and weldment B7 and the temperature in the welding process to make the workpiece semi-solid. Other steps are the same as in Embodiment 1.

Embodiment Three

In the second step of this embodiment, the ultrasonic frequency is 40K-60K. The ultrasonic frequency can be selected according to the specific conditions of weldment A6 and weldment B7 and the wear condition of the stirring pin 1, so that the grains in the weld nugget and its surrounding area can be fully refined and the performance of the joint can be improved. Other steps are the same as in Embodiment 1.

Embodiment Four

In the third step of this embodiment, the stirring tool 5 moves along the horizontal direction at a speed of 50-200 mm/min. The moving speed of the stirring tool can be selected according to the weldment A6 and the weldment B7 and the temperature in the welding process to make the workpiece semi-solid. Other steps are the same as in Embodiment 1.

Embodiment five

In step three of this embodiment, when the stirring tool 5 reaches the set pricking depth, the stirring needle 1 stops pricking and continues to rotate for 4-5 minutes. The continuous rotation time of the stirring needle can be selected according to the specific conditions of weldment A6 and weldment B7 and the temperature in the welding process, so that the workpiece can be fully preheated and the workpiece can be more easily semi-solid. Other steps are the same as in the fourth embodiment.

Claims (4)

1. be applicable to the ultrasonic semi-solid state assistant friction stir welding method that particle enhanced aluminum-based composite material connects, specifically adopt following steps:

Step 1, weldment A and weldment B docking is placed and is positioned in same level, and with fixture clamping on workbench;

The mixing needle indentation of step 2, composition stirring tool, its maximum gauge is greater than 1.5 times of thickness of workpiece and cone angle is less than 5 °, and mixing needle penetrates position to be welded with the rotating speed of 3000～5000rpm; The shaft shoulder of composition stirring tool is fixed, and the shaft shoulder diameter thickness of workpiece that is greater than 2 times; The ultrasonic wave of ultrasonic transducer is directly delivered to inside, district to be welded by the mixing needle being connected with ultrasonic amplitude transformer, and hyperacoustic parameter is as follows: frequency is that 16～60K and amplitude are 20～50 μ m; It is 1～4mm/min that stirring tool penetrates speed, and mixing needle penetrates the little 0.1～0.3mm of workpiece depth ratio thickness of workpiece, and the shaft shoulder does not penetrate workpiece, and retainer shaft shoulder end face and workpiece surface fit tightly;

Step 3, in the time that stirring tool reaches the lower bundle degree of depth of setting, mixing needle stop lower bundle and continue rotation 4～5 minutes; Then, stirring tool moves along the interface horizontal direction of weldment A and weldment B with the speed of 50～200mm/min, until welded.

2. a kind of ultrasonic semi-solid state assistant friction stir welding method that particle enhanced aluminum-based composite material connects that is applicable to as claimed in claim 1, is characterized in that: described weldment A and weldment B are sheet material.

3. a kind of ultrasonic semi-solid state assistant friction stir welding method that particle enhanced aluminum-based composite material connects that is applicable to as claimed in claim 1, it is characterized in that: described stirring tool is made up of mixing needle, the fixing shaft shoulder, ultrasonic amplitude transformer and ultrasonic transducer, the fixing shaft shoulder is sleeved on mixing needle, and mixing needle, ultrasonic amplitude transformer and ultrasonic transducer are as a whole.

4. a kind of ultrasonic semi-solid state assistant friction stir welding method that particle enhanced aluminum-based composite material connects that is applicable to as claimed in claim 1, is characterized in that: in step 2, described ultrasonic frequency is 40K～60K.